On 2/19/2014 4:41 PM, dpb wrote:
> One thing is clear...the practice w/ the modern computer and things such
> as Matlab, Mathematica, and all the other engineering toolsets is a far
> cry from the early days when was issued the 20" K+E slide rule when
> first reported for duty at B&W NPGD...
Last couple of semesters of college making up for lost time with as many
math courses as I could handle, my slide rule skills were like a sharp
pencil when I was drafted into the Army. As a young Fire Direction
Officer, I had no trouble routinely sending commands to the guns before
our computerized system cleared its buffers.
Today, I'd have a hard time using one to stir my coffee ...
--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
KarlCaillouet@ (the obvious)
On Friday, February 21, 2014 6:22:15 PM UTC-5, [email protected] wrote:
> On Thu, 20 Feb 2014 14:40:05 -0600, Leon <lcb11211@swbelldotnet>
>
> wrote:
>
>
>
> >On 2/20/2014 2:23 PM, [email protected] wrote:
>
> >> *Should be "of equal mass and close mass distribution"
>
> >>
>
> >> And please don't swap the terms. Recoil? Leon likes the term bounce back :)
>
> >
>
> >Bounce back = Energy that is not entirely absorbed by the strike and
>
> >which is deflected.
>
>
>
> Right. Energy that isn't absorbed is useless, however that which isn't
>
> moving the struck object is just being absorbed uselessly as heat
>
> anyway. I don't see that the lack of "bounce" necessarily makes the
>
> hammer more "efficient".
It doesn't.
>It just means it's absorbing energy, rather
> than the user's arm.
>
>
>
> >Recoil is a good term. Not all of the energy spent inside a bullet is
>
> >pushing the bullet down the barrel, much is absorbed by the person
>
> >shooting the gun.
>
>
>
> Newton's third law kinda makes this a given.
On 2/19/2014 10:00 AM, dpb wrote:
> On 2/19/2014 9:41 AM, Swingman wrote:
>> All too often the advice proffered in forums like this are based on
>> Googled knowledge and damned little to none, actual experience.
>
> Well, being a "trained physicist" sometimes helps to understand the
> underlying principles involved, too. :)
No worries, those who are trained in just about any scientific
discipline are generally quite capable of recognizing the same in others
of very different disciplines, Google notwithstanding. <g>
That fact might have a time limit on it though ... ;)
--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
KarlCaillouet@ (the obvious)
On Mon, 17 Feb 2014 22:50:28 -0800 (PST), [email protected] wrote:
> On Tuesday, February 18, 2014 12:40:22 AM UTC-5, Martin Eastburn wrote:
>> As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
>>
>> You want the many hammer blows when you smack something.
>
> Not convinced. Here's why:
>
> F = ma : Half full gives me approx F = 1/2 ma
>
> "Many hammer blows" : Force = ma (collission1) + ma (collisions2) ...
> etc. = m(total)a
>
> You only end up with approx 1/2 the amount of force as a full hammer head
> spread out over multiple smaller collisions. The sum of which are still
> 1/2 a full head.
>
>>
>> Martin
>>
>> On 2/17/2014 10:34 PM, [email protected] wrote:
>>
>>> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun
>>> project.
>>
>>>
>>
>>> The plans were taken from Shopnotes 1992 No2.
>>
>>>
>>
>>> http://www.youtube.com/watch?v=t-j3UcfQ_rE
>>
>>>
But you have ended up with a sledge hammer, not a dead blow.
A proper dead blow transfers all its force and no bounce back. You can hit
it as hard as you can on a concrete floor and it just "sits" there.
--- news://freenews.netfront.net/ - complaints: [email protected] ---
On Friday, February 21, 2014 10:40:34 AM UTC-5, dpb wrote:
> On 2/20/2014 5:19 PM, [email protected] wrote:
>
> ...
>
>
>
> > Agreed. They behave differently and I touched on the differences in length.
>
> ...
>
>
>
> Superficially and without proper conclusions, unfortunately.
No. Correct conclusions and efficiently in depth.
>
>
>
> A demonstration that isn't _exactly_ the same problem, but very closely
>
> related is at...
>
>
>
> <http://neilatkin.com/2013/07/31/3-act-physics-momentum/>
>
>
>
> --
"Mike Marlow" <[email protected]> wrote:
> dpb wrote:
>> On 2/18/2014 7:00 PM, Leon wrote:
>> ...
>>
>>> I don't know, I can hold the impact with a large enough socket, with
>>> my bare hand, with a little slippage.
>>
>> Because impact wrenches don't actually deliver torque, per se, but an
>> energy impulse. Somewhat paradoxically, against a "springy"
>> resistance like your hand, there is very little, if any actual torque
>> delivered as opposed to it working against a stuck fastener.
>>
>> There's a decent albeit not fully rigorous discussion at wikipedia
>> under a heading "Effect of Impact Drive"...in short to transfer the
>> hammer action to the driven part requires an essentially elastic (the
>> cue ball on the object ball thingie) impact whereas your hand hold is
>> very non-elastic.
>>
>> <http://en.wikipedia.org/wiki/Impact_wrench>
>
> Boy - this group can dive down into esoteric rabbit holes! Why doesn't
> someone just try it rather than deliberating all of the theoretical
> I-don't-really-know stuff?
Well actually, as indicated with one of my last reply, I have tried it.
<[email protected]> wrote:
> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>
> The plans were taken from Shopnotes 1992 No2.
>
> http://www.youtube.com/watch?v=t-j3UcfQ_rE
Nice looking mallet!
BUT with no internal loose mass, your answer about " deadblow?", would be
no, not until the bb's slowly deform the cylinders and have more room to
move to give the secondary amount of force to help counteract bounce back.
The more movement the more counteraction to bounce back you will have.
Having said that, walnut being significantly softer than maple might itself
cushion/absorb some of the impact and lessen the bounce back if you don't
strike squarely or until the walnut rounds off or splits off.
If you are building these for a conversation piece, the walnut looks very
nice. For actual use I would recommend that the striking faces be of equal
hardness. As the softer material mixed with a harder material wears away
faster the striking surface naturally becomes smaller and the force is
concentrated in a smaller area. This might leave an unwanted impression on
a wood surface if you are using the mallet for adjustments. That particular
use is what deadblows excel at.
If you used a heavier material, walnut is pretty lite weight, with less
loose mass internally you benefit more with more counteraction to bounce
back.
Now let me throw you a curve on your "force calculation". First off your
equation does seem logical.
BUT an impact driver delivers more efficient force than does a
drill/driver with the same available power supply. It's the multiple
impacts of the impact driver that wins the contest of loosening the stuck
screw vs. the constant force of the drill/ driver..
So while loose shot in a dead blow hammer might seem to have less force at
initial impact the amount of work being done is probably close to the same
given the second impact force of the loose shot. That is going to be hard
to formulate given some loss from the secondary force counteracting the
bounce back. Maybe if the entire mallet striking surface was walnut the
bounce back would be diminished. Whew! :-). Something to think about.
LOL
I hate to keep kicking this horse but... I just received my electronic issue if Popular Woidworking today. An article on mallets was on the inside. What a coinkydink.
On the topic of dead blows the cabal says:
"Minimal rebound makes better use of the applied force"
How do I get a better use of force here? How did this myth start? I want to blame someone. Norm? Can I blame Norm? :)
Again if F = ma. And I apply the m a little at a time apposed to all at once, how is this a better use of the applied force? I think we officially debunked Leon's hammer driver explanation :)
<[email protected]> wrote:
> This is the one I have.
> http://www.leevalley.com/en/wood/page.aspx?p=44326&cat=1,53193
----------------------------------------------------------------
When it's time to replace, HF is your place.
About $5 for the equivalent.
Lew
On Sat, 22 Feb 2014 00:59:19 +0000 (UTC), [email protected]
(Larry W) wrote:
>In article <[email protected]>,
> <[email protected]> wrote:
>>On Thu, 20 Feb 2014 16:56:54 -0600, Leon <lcb11211@swbelldotnet>
>>>For the past 20 or so years I have used one of those smaller hammers
>>>with a red rubber face on one end and a yellow plastic face on the
>>>other.
>>
>>This is the one I have.
>>http://www.leevalley.com/en/wood/page.aspx?p=44326&cat=1,53193
>
>Buy one here and you'll have enough money left over to get 4 pounder too.
>
>http://www.harborfreight.com/2-12-lb-neon-orange-dead-blow-hammer-69003.html
>
>http://www.harborfreight.com/4-lb-neon-orange-dead-blow-hammer-41800.html
>
>and don't forget your free worklight, screwdrivers, and tape measure while
>you're there.
>
>http://www.harborfreight.com/free-coupons2014.html
"Limit one FREE coupon per customer per day."
In article <[email protected]>,
<[email protected]> wrote:
>On Thu, 20 Feb 2014 16:56:54 -0600, Leon <lcb11211@swbelldotnet>
>>For the past 20 or so years I have used one of those smaller hammers
>>with a red rubber face on one end and a yellow plastic face on the
>>other.
>
>This is the one I have.
>http://www.leevalley.com/en/wood/page.aspx?p=44326&cat=1,53193
Buy one here and you'll have enough money left over to get 4 pounder too.
http://www.harborfreight.com/2-12-lb-neon-orange-dead-blow-hammer-69003.html
http://www.harborfreight.com/4-lb-neon-orange-dead-blow-hammer-41800.html
and don't forget your free worklight, screwdrivers, and tape measure while
you're there.
http://www.harborfreight.com/free-coupons2014.html
--
Make it as simple as possible, but not simpler. (Albert Einstein)
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
On Sat, 22 Feb 2014 16:28:52 -0500, "Morgans"
<[email protected]> wrote:
>
>
><[email protected]> wrote
>
>> You just contradicted yourself. There is *not* a greater transfer of
>> energy if the hammer rebounds. The energy required for the rebound is
>> not imparted to the object, which is sorta the purpose of striking it
>> in the first place.
>
>What he said. Where did the energy for the mallet come from to make it
>reverse direction. From the object being struck not soaking up all the
>energy. Been saying that all along.
That said, because it doesn't rebound doesn't mean that it did its
job, either. If the energy is absorbed in the hammer's head (heat),
it's not doing much good either. Of course, if it dents the paint on
your just completed cherry table, it isn't doing its job either. ;-)
>
>This horse is about dead, isn't it?
You're supposed to put the glue on the tenon _before_ pounding it into
the mortise.
On Thursday, February 20, 2014 5:06:50 PM UTC-5, Leon wrote:
> On 2/20/2014 3:31 PM, [email protected] wrote:
>=20
> > There is bounce. That's my point. The "bouncing" is occurring on the =
inside of the cavity. A ball dropped from one end of a cavity to the other=
is going to bounce.
>=20
>=20
>=20
> The mallet head striking an object bounces. The shot hitting the=20
>=20
> opposite end of the mallet when the mallet bounces back "helps" to=20
>=20
> cancel out the head bounce back.
It helps to cancel out the mallet bouncing back. I'm not arguing this poin=
t. We agree here.
There is bouncing in either case that results in an energy loss. This does=
n't address the deadblow's claimed increase in efficiency. =20
Hundreds (arbitrary) of shots smacking into the bottom of a cavity or a sho=
t filled cavity are going to bounce and bang around. The sum loss in energ=
y from the bounce back (including any collisions between each other) of eac=
h shot is going to be significant.=20
If you were to compare the efficiency of a deadblow's strike and a mallet o=
f equal mass and size (shot filled w/ no empty space), and take into accoun=
t the above, I wouldn't expect an increase in efficiency from the deadblow.
On Tuesday, February 18, 2014 1:55:33 AM UTC-5, woodchucker wrote:
> On 2/18/2014 1:50 AM, [email protected] wrote:
>
> > On Tuesday, February 18, 2014 12:40:22 AM UTC-5, Martin Eastburn wrote:
>
> >> As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
>
> >>
>
> >> You want the many hammer blows when you smack something.
>
> >
>
> >
>
> > Not convinced. Here's why:
>
> >
>
> > F = ma : Half full gives me approx F = 1/2 ma
>
> >
>
> > "Many hammer blows" : Force = ma (collission1) + ma (collisions2) ... etc. = m(total)a
>
> >
>
> > You only end up with approx 1/2 the amount of force as a full hammer head spread out over multiple smaller collisions. The sum of which are still 1/2 a full head.
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >>
>
> >> Martin
>
> >>
>
> >>
>
> >>
>
> >> On 2/17/2014 10:34 PM, [email protected] wrote:
>
> >>
>
> >>> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>
> >>
>
> >>>
>
> >>
>
> >>> The plans were taken from Shopnotes 1992 No2.
>
> >>
>
> >>>
>
> >>
>
> >>> http://www.youtube.com/watch?v=t-j3UcfQ_rE
>
> >>
>
> >>>
>
> >
>
>
>
> So I was wrong, I thought Martin was talking about the bounce back.
>
> With a full head, you gain mass, but I don't think it gives you the
>
> deadblow, that is desireable. That's why I would go with less fill, but
>
> lead, to gain back the mass.
No. Substitute the mass for lead in my equations above. You are still better off with a full head of lead than 1/2 full head of lead. It's the same equations.
>
>
>
> --
>
> Jeff
On Thu, 20 Feb 2014 14:40:05 -0600, Leon <lcb11211@swbelldotnet>
wrote:
>On 2/20/2014 2:23 PM, [email protected] wrote:
>> *Should be "of equal mass and close mass distribution"
>>
>> And please don't swap the terms. Recoil? Leon likes the term bounce back :)
>
>Bounce back = Energy that is not entirely absorbed by the strike and
>which is deflected.
Right. Energy that isn't absorbed is useless, however that which isn't
moving the struck object is just being absorbed uselessly as heat
anyway. I don't see that the lack of "bounce" necessarily makes the
hammer more "efficient". It just means it's absorbing energy, rather
than the user's arm.
>Recoil is a good term. Not all of the energy spent inside a bullet is
>pushing the bullet down the barrel, much is absorbed by the person
>shooting the gun.
Newton's third law kinda makes this a given.
Consider this:
A large force that is delivered in smaller doses is not as efficient at driving a joint home as one force all at once.
Each smaller force would have to first overcome the coefficient of friction before it can move an object. Any small fraction of the force that is below the coefficient of friction is a loss.
Consider the extreme : dropping 100 kg of lead weights on a stuck joint at a 1g at a time versus dropping the 100 kg all at once. If the 1g force doesn't break the coefficient of friction you will have very little net joint closure.
But you still have deceleration. A point that gets at the increased efficiency claim. The magnitude can certainly be debated.
I'm not sold on the increased efficiency from a better recoil property for the shot. It's still going to recoil. Bang into each other (energy loss) and bang into the sides of the cavity (energy loss)
You also have a loss in energy via heat (from banging into each other) that doesn't come into play on a solid hammer of equal mass. Again, this gets to efficiency. Magnitude can be debated.
I don't think we get a free lunch here. More efficiency from a hammer strike with the same amount of mass - not convinced.
<[email protected]> wrote:
> I'm just about to hit sixty and my wants have changed significantly.
> Take food as an example. When I was younger I mostly had quantity on
> my mind. That's changed and now I almost exclusively seek out
> quality.
> ~ That concept has transferred over to a significant portion of my
> life.
------------------------------------------------------
Rookie!!
Can certainly relate to your change in perspective of life.
Lew
On Thu, 20 Feb 2014 19:14:47 -0500, "Mike Marlow"
>Oh man Dave - sucks that you don't have Harbor Freight up there
Well, we've got a Princess Auto which isn't too far removed. But, to
tell the truth, the main reason I buy from Lee Valley aside from the
quality of their tools is their service. I can search out cheap or
quality tools almost anywhere. I *can't* get top notch service if I
have a problem or complaint most places.
I'm just about to hit sixty and my wants have changed significantly.
Take food as an example. When I was younger I mostly had quantity on
my mind. That's changed and now I almost exclusively seek out quality.
~ That concept has transferred over to a significant portion of my
life.
On Tuesday, February 18, 2014 11:26:06 PM UTC-5, Mike Marlow wrote:
> dpb wrote:
>
> > On 2/18/2014 7:00 PM, Leon wrote:
>
> > ...
>
> >
>
> >> I don't know, I can hold the impact with a large enough socket, with
>
> >> my bare hand, with a little slippage.
>
> >
>
> > Because impact wrenches don't actually deliver torque, per se, but an
>
> > energy impulse. Somewhat paradoxically, against a "springy"
>
> > resistance like your hand, there is very little, if any actual torque
>
> > delivered as opposed to it working against a stuck fastener.
>
> >
>
> > There's a decent albeit not fully rigorous discussion at wikipedia
>
> > under a heading "Effect of Impact Drive"...in short to transfer the
>
> > hammer action to the driven part requires an essentially elastic (the
>
> > cue ball on the object ball thingie) impact whereas your hand hold is
>
> > very non-elastic.
>
> >
>
> > <http://en.wikipedia.org/wiki/Impact_wrench>
>
>
>
> Boy - this group can dive down into esoteric rabbit holes! Why doesn't
>
> someone just try it rather than deliberating all of the theoretical
>
> I-don't-really-know stuff?
>
>
>
> --
>
>
>
> -Mike-
>
> [email protected]
It's physics. All of which can be extremely modeled with math w/o lifting a finger.
On 2/20/2014 10:47 AM, [email protected] wrote:
> I hate to keep kicking this horse but... I just received my electronic issue if Popular Woidworking today. An article on mallets was on the inside. What a coinkydink.
>
> On the topic of dead blows the cabal says:
>
> "Minimal rebound makes better use of the applied force"
>
> How do I get a better use of force here? How did this myth start? I want to blame someone. Norm? Can I blame Norm? :)
>
> Again if F = ma. And I apply the m a little at a time apposed to all at once, how is this a better use of the applied force? I think we officially debunked Leon's hammer driver explanation :)
>
>
>
>
>
>
Probably thinking one thing and saying another. With a dead blow you
don't have to worry about the the hammer bounce back coming and hitting
you in the head. ;~) Consequently you can bang harder and not worry
that so much.
On 2/18/2014 1:50 AM, [email protected] wrote:
> On Tuesday, February 18, 2014 12:40:22 AM UTC-5, Martin Eastburn wrote:
>> As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
>>
>> You want the many hammer blows when you smack something.
>
>
> Not convinced. Here's why:
>
> F = ma : Half full gives me approx F = 1/2 ma
>
> "Many hammer blows" : Force = ma (collission1) + ma (collisions2) ... etc. = m(total)a
>
> You only end up with approx 1/2 the amount of force as a full hammer head spread out over multiple smaller collisions. The sum of which are still 1/2 a full head.
>
>
>
>
>
>
>
>
>
>>
>> Martin
>>
>>
>>
>> On 2/17/2014 10:34 PM, [email protected] wrote:
>>
>>> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>>
>>>
>>
>>> The plans were taken from Shopnotes 1992 No2.
>>
>>>
>>
>>> http://www.youtube.com/watch?v=t-j3UcfQ_rE
>>
>>>
>
So I was wrong, I thought Martin was talking about the bounce back.
With a full head, you gain mass, but I don't think it gives you the
deadblow, that is desireable. That's why I would go with less fill, but
lead, to gain back the mass.
--
Jeff
As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
You want the many hammer blows when you smack something.
Martin
On 2/17/2014 10:34 PM, [email protected] wrote:
> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>
> The plans were taken from Shopnotes 1992 No2.
>
> http://www.youtube.com/watch?v=t-j3UcfQ_rE
>
What I don't understand in particular are these two phenomena that would se=
em to reduce the effectiveness of the applied mass:
1) when the deadblow is accerated toward the object the mass (majority) is =
in the rear of the cavity (from inertia). After the deadblow makes contact=
the mass leaves the rear of the cavity and travels to the from and as it d=
oes, it decelerates. (Loss of a thus loss of efficiency)
2) there is still bounce back inside the deadblow head. After the shot is =
thrown against the front inside of the deadblow it will bounce back. The e=
nergy that is lost to internal bounce back should equal any energy lost to =
the bounce back of a non-deadblow mallet of equal mass. Correct?
"Mike Marlow" <[email protected]> wrote:
> [email protected] wrote:
>> On Thu, 20 Feb 2014 15:36:59 -0800, "Lew Hodgett"
>>> When it's time to replace, HF is your place.
>>> About $5 for the equivalent.
>>
>> Yup, I could buy a cheap knockoff from Harbour Freight for a lot less
>> money. Then I could add on mailing costs, duty garbage and several
>> weeks time waiting for it to come across the border into Canada.
>>
>> Good idea Lew. I'll keep that idea in mind the next time I want to buy
>> some cheap tool garbage.
>
>
> Oh man Dave - sucks that you don't have Harbor Freight up there.
Oh man Mike, that is almost like saying that it sucks that they don't have
Obamacare up there. :-)
<[email protected]> wrote:
> Yup, I could buy a cheap knockoff from Harbour Freight for a lot
> less
> money. Then I could add on mailing costs, duty garbage and several
> weeks time waiting for it to come across the border into Canada.
>
> Good idea Lew. I'll keep that idea in mind the next time I want to
> buy
> some cheap tool garbage.
-------------------------------------------------------------------
It's NOT buying cheap garbage,
it is the prudent utilization of ones available resources. <wink>
It's all a matter of perspective.
Lew
On Thu, 20 Feb 2014 15:36:59 -0800, "Lew Hodgett"
>When it's time to replace, HF is your place.
>About $5 for the equivalent.
Yup, I could buy a cheap knockoff from Harbour Freight for a lot less
money. Then I could add on mailing costs, duty garbage and several
weeks time waiting for it to come across the border into Canada.
Good idea Lew. I'll keep that idea in mind the next time I want to buy
some cheap tool garbage.
[email protected] wrote:
> On Thu, 20 Feb 2014 15:36:59 -0800, "Lew Hodgett"
>> When it's time to replace, HF is your place.
>> About $5 for the equivalent.
>
> Yup, I could buy a cheap knockoff from Harbour Freight for a lot less
> money. Then I could add on mailing costs, duty garbage and several
> weeks time waiting for it to come across the border into Canada.
>
> Good idea Lew. I'll keep that idea in mind the next time I want to buy
> some cheap tool garbage.
Oh man Dave - sucks that you don't have Harbor Freight up there.
--
-Mike-
[email protected]
In article <[email protected]>,
<[email protected]> wrote:
>On Thu, 20 Feb 2014 15:36:59 -0800, "Lew Hodgett"
>>When it's time to replace, HF is your place.
>>About $5 for the equivalent.
>
>Yup, I could buy a cheap knockoff from Harbour Freight for a lot less
>money. Then I could add on mailing costs, duty garbage and several
>weeks time waiting for it to come across the border into Canada.
>
>Good idea Lew. I'll keep that idea in mind the next time I want to buy
>some cheap tool garbage.
I'd bet even money that the HF model is identical to LVs except for color.
--
Make it as simple as possible, but not simpler. (Albert Einstein)
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
On Thursday, February 20, 2014 4:41:10 PM UTC-5, dpb wrote:
> On 2/20/2014 2:59 PM, [email protected] wrote:
>
> ...
>
>
>
> > I don't think we get a free lunch here. More efficiency from a
>
> > hammer strike with the same amount of mass - not convinced.
>
>
>
> They're _not_ the same system and that _does_ make a difference in how
>
> they behave.
Agreed. They behave differently and I touched on the differences in length.
>
>
>
> --
On Tuesday, February 18, 2014 12:40:22 AM UTC-5, Martin Eastburn wrote:
> As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
>
> You want the many hammer blows when you smack something.
Not convinced. Here's why:
F = ma : Half full gives me approx F = 1/2 ma
"Many hammer blows" : Force = ma (collission1) + ma (collisions2) ... etc. = m(total)a
You only end up with approx 1/2 the amount of force as a full hammer head spread out over multiple smaller collisions. The sum of which are still 1/2 a full head.
>
> Martin
>
>
>
> On 2/17/2014 10:34 PM, [email protected] wrote:
>
> > I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>
> >
>
> > The plans were taken from Shopnotes 1992 No2.
>
> >
>
> > http://www.youtube.com/watch?v=t-j3UcfQ_rE
>
> >
On 2/18/2014 10:11 AM, [email protected] wrote:
> Yes. Thank you for the 'not'. :)
LOL
Welcome to MY world. Thinking one thing, typing something else all
together.
On Monday, February 17, 2014 10:34:56 PM UTC-6, [email protected] wrote:
> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly fun project.
>
>
>
> The plans were taken from Shopnotes 1992 No2.
>
>
>
> http://www.youtube.com/watch?v=t-j3UcfQ_rE
It looks great but I think a solid head where you drill, fill, and cap on both sides would be more useful. Also, why not taper the mortise and insert the handle end first so that it gets more snug the further you pull it through?
Here's Roy Underhill getting it done.
http://video.pbs.org/video/2365021538/
On Thu, 20 Feb 2014 19:39:06 -0500, "Mike Marlow"
>times as much for something that just isn't all that much better. The name
>brand market has done a good job of marketing their names, and the quality
>difference just isn't there in a lot of cases.
Sure, I know what you're saying. Taking the dead blow hammer that was
under discussion, any cheap dead blow would likely do, I can't deny
that. For me, it mostly comes down to what's easier or less time
consuming. Cost often comes in third.
When it comes to tools, I like most of what Lee Valley sells. If I
ever have any problem at all, they take care of it right away. One of
their biggest stores is close to where I live. If I can't get there,
my closest friend lives very close to one of their stores.
I've got a driver's license, but don't own a car. Because of the
chair, for me to go running around or spreading my dollars a little
more judiciously, it takes me considerable time than most. I guess my
position is a little more unique that most, but it's what works for
me. I'll even admit that I'm probably mired in my ways and not so
inclined to change.
On 2/18/2014 12:40 AM, Martin Eastburn wrote:
> As I posted, I'd use a 50% fill of BB's - the video shows 100% fill.
> You want the many hammer blows when you smack something.
> Martin
>
> On 2/17/2014 10:34 PM, [email protected] wrote:
>> I made a mallet (deadblow?) from walnut, maple and BBs. Incredibly
>> fun project.
>>
>> The plans were taken from Shopnotes 1992 No2.
>>
>> http://www.youtube.com/watch?v=t-j3UcfQ_rE
>>
Looks good, but I would agree with Martin, also I might use lead shot to
increase the weight with less fill.
--
Jeff
On Thu, 20 Feb 2014 16:06:50 -0600, Leon <lcb11211@swbelldotnet>
>The mallet head striking an object bounces. The shot hitting the
>opposite end of the mallet when the mallet bounces back "helps" to
>cancel out the head bounce back.
Pretty much as I'd have explained it. But however one looks at it, a
dead blow mallet is a damned useful tool. You don't really realize it
though until you actually use one.
On 2/18/2014 8:29 AM, [email protected] wrote:
> ok. Then what i have is a mallet and I named it correctly. I'm
concerned with the mallet head bouncing back. I'd rather strike fewer
times with more force than more times with less bounce back.
Probably "not" concerned with the mallet bouncing back....
With that thought you have exactly what you were going for.
Imagine using mercury for the weight, I wonder if it would leak out. LOL
On 2/19/2014 6:19 AM, Mike Marlow wrote:
> You get the beer prize then. I just sometimes find it funny how much we
> kick ideas or thoughts around here instead of putting some of them to the
> test. It does show we've got some thinking people here and sometimes I'm
> downright amazed at what the guys here contribute, but still...
That's why it is invaluable, when either taking or giving advice, for
those seeking same to be able to see some actual evidence of the
advisor's skill and knowledge of that which he speaks.
IOW, thank dog for hypertext markup language and Sir Berners-Lee giving
some us the ability to do that when proffering advice. ;)
All too often the advice proffered in forums like this are based on
Googled knowledge and damned little to none, actual experience.
--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
KarlCaillouet@ (the obvious)
>>
>> With a full head, you gain mass, but I don't think it gives you the
>>
>> deadblow, that is desireable. That's why I would go with less fill, but
>>
>> lead, to gain back the mass.
>
> No. Substitute the mass for lead in my equations above. You are still
> better off with a full head of lead than 1/2 full head of lead. It's the
> same equations.
What you are describing is a weighted mallet. For a deadblow hammer to be
effective, the shot moves to the back of the hammer as you start to swing,
then crashes forward at impact, thus reducing rebound. It can not shift if
it is full. See the definition, here.
http://www.hgtv.com/home-improvement/tool-glossary/index.html#dname
dead-blow hammer
Strikes blows without damaging the work's surface. The tool's hollow head is
partially filled with small metal shot, which reduces rebounding.
--
Jim in NC
---
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In article <[email protected]>,
Morgans <[email protected]> wrote:
<various arguments about dead blow hammer design snipped...>
>What you are describing is a weighted mallet. For a deadblow hammer to be
>effective, the shot moves to the back of the hammer as you start to swing,
>then crashes forward at impact, thus reducing rebound. It can not shift if
>it is full. See the definition, here.
>
Make the hammer twice as big, using equivalent of a full load of shot from
the original smaller size, for the best of both worlds? :)
--
There is always an easy solution to every human problem -- neat,
plausible, and wrong." (H L Mencken)
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
In article <[email protected]>,
Leon <lcb11211@swbelldotnet> wrote:
>oN 2/18/2014 9:15 AM, [email protected] wrote:
>> Consider this:
>>
>> A large force that is delivered in smaller doses is not as efficient
>at driving a joint home as one force all at once.
>
>Perhaps in theory. but in real life, the impact driver works with
>multiple lighter strength impacts. Its the multiple impacts that
>produce more work in a given period of time. A larger single force may
>be way too much or simply not enough.
>
I believe the flaw to that argument is that an impact driver in fact
does NOT use multiple lighter strength impacts, but actually, due to the
nature of impact, uses momentarily HIGHER forces than the static tool
torque spec would imply.
--
There is always an easy solution to every human problem -- neat,
plausible, and wrong." (H L Mencken)
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
On 2/18/2014 7:00 PM, Leon wrote:
...
> I don't know, I can hold the impact with a large enough socket, with my
> bare hand, with a little slippage.
Because impact wrenches don't actually deliver torque, per se, but an
energy impulse. Somewhat paradoxically, against a "springy" resistance
like your hand, there is very little, if any actual torque delivered as
opposed to it working against a stuck fastener.
There's a decent albeit not fully rigorous discussion at wikipedia under
a heading "Effect of Impact Drive"...in short to transfer the hammer
action to the driven part requires an essentially elastic (the cue ball
on the object ball thingie) impact whereas your hand hold is very
non-elastic.
<http://en.wikipedia.org/wiki/Impact_wrench>
--
dpb wrote:
> On 2/18/2014 7:00 PM, Leon wrote:
> ...
>
>> I don't know, I can hold the impact with a large enough socket, with
>> my bare hand, with a little slippage.
>
> Because impact wrenches don't actually deliver torque, per se, but an
> energy impulse. Somewhat paradoxically, against a "springy"
> resistance like your hand, there is very little, if any actual torque
> delivered as opposed to it working against a stuck fastener.
>
> There's a decent albeit not fully rigorous discussion at wikipedia
> under a heading "Effect of Impact Drive"...in short to transfer the
> hammer action to the driven part requires an essentially elastic (the
> cue ball on the object ball thingie) impact whereas your hand hold is
> very non-elastic.
>
> <http://en.wikipedia.org/wiki/Impact_wrench>
Boy - this group can dive down into esoteric rabbit holes! Why doesn't
someone just try it rather than deliberating all of the theoretical
I-don't-really-know stuff?
--
-Mike-
[email protected]
Leon wrote:
> "Mike Marlow" <[email protected]> wrote:
>> dpb wrote:
>>> On 2/18/2014 7:00 PM, Leon wrote:
>>> ...
>>>
>>>> I don't know, I can hold the impact with a large enough socket,
>>>> with my bare hand, with a little slippage.
>>>
>>> Because impact wrenches don't actually deliver torque, per se, but
>>> an energy impulse. Somewhat paradoxically, against a "springy"
>>> resistance like your hand, there is very little, if any actual
>>> torque delivered as opposed to it working against a stuck fastener.
>>>
>>> There's a decent albeit not fully rigorous discussion at wikipedia
>>> under a heading "Effect of Impact Drive"...in short to transfer the
>>> hammer action to the driven part requires an essentially elastic
>>> (the cue ball on the object ball thingie) impact whereas your hand
>>> hold is very non-elastic.
>>>
>>> <http://en.wikipedia.org/wiki/Impact_wrench>
>>
>> Boy - this group can dive down into esoteric rabbit holes! Why
>> doesn't someone just try it rather than deliberating all of the
>> theoretical I-don't-really-know stuff?
>
>
> Well actually, as indicated with one of my last reply, I have tried
> it.
You get the beer prize then. I just sometimes find it funny how much we
kick ideas or thoughts around here instead of putting some of them to the
test. It does show we've got some thinking people here and sometimes I'm
downright amazed at what the guys here contribute, but still...
--
-Mike-
[email protected]
On 2/18/2014 10:26 PM, Mike Marlow wrote:
> dpb wrote:
>> On 2/18/2014 7:00 PM, Leon wrote:
>> ...
>>
>>> I don't know, I can hold the impact with a large enough socket, with
>>> my bare hand, with a little slippage.
>>
>> Because impact wrenches don't actually deliver torque, per se, but an
>> energy impulse. Somewhat paradoxically, against a "springy"
>> resistance like your hand, there is very little, if any actual torque
>> delivered as opposed to it working against a stuck fastener.
>>
>> There's a decent albeit not fully rigorous discussion at wikipedia
>> under a heading "Effect of Impact Drive"...in short to transfer the
>> hammer action to the driven part requires an essentially elastic (the
>> cue ball on the object ball thingie) impact whereas your hand hold is
>> very non-elastic.
>>
>> <http://en.wikipedia.org/wiki/Impact_wrench>
>
> Boy - this group can dive down into esoteric rabbit holes! Why doesn't
> someone just try it rather than deliberating all of the theoretical
> I-don't-really-know stuff?
Not really so esoteric at all...it's the explanation for _why_ Leon's
experience is so....that seems at best at least counter-intuitive on
first blush.
--
On 2/19/2014 9:41 AM, Swingman wrote:
...
> All too often the advice proffered in forums like this are based on
> Googled knowledge and damned little to none, actual experience.
Well, being a "trained physicist" sometimes helps to understand the
underlying principles involved, too. :) Google did help find a
readable article, however, that outlines them...
--
dpb wrote:
> On 2/19/2014 9:41 AM, Swingman wrote:
> ...
>
>> All too often the advice proffered in forums like this are based on
>> Googled knowledge and damned little to none, actual experience.
>
> Well, being a "trained physicist" sometimes helps to understand the
> underlying principles involved, too. :) Google did help find a
> readable article, however, that outlines them...
Ok - I risk going out on a limb here, in areas that I'm not qualified to
speak into, but I do recognize your claim to credentials. What I have seen
many, many times is where there is some other consideration that the trained
eye failed to see. Not at all to downplay those credentials, but it is fair
to say that even the best design by the best engineering mind, falls prey to
the discovery of the prototype. You know - the oops moment when we realize
that we didn't recognize some aspect of the problem, or the likes. If
everything worked in the theoretical realm as it seems it should (as we see
it...), there would be no need for prototypes, proof of concept, testing,
etc.
Ok (again...), I lean towards the practical. I appreciate the theoretical
and in fact I value it greatly. But - I go to "just doing it" at some
point. Maybe that's just me, but it's the only way I can really prove the
theories behind what I'm doing.
--
-Mike-
[email protected]
On 2/19/2014 11:07 AM, Mike Marlow wrote:
...
> Ok (again...), I lean towards the practical. I appreciate the theoretical
> and in fact I value it greatly. But - I go to "just doing it" at some
> point. Maybe that's just me, but it's the only way I can really prove the
> theories behind what I'm doing.
Well, certainly I'll never claim every analysis I ever did was perfect
when taken to the lab w/o modification... :) (*)
OTOH, a prototype w/o some design basis in theory has a likelihood to
not be very successful, either, at least w/o a lot more testing effort
than could be necessary.
And, of course, the type of problem one's out to try to solve has a lot
to do with how much and how involved calculations needs must be. I only
tossed this one in here because the case of the impact wrench behavior
brought up isn't so apparent as to why since as Leon notes one can hold
it by hand yet it has the ability to break loose "frozen" fasteners that
simple leverage often can't. That seemed worth pointing as to what is
actually happening.
(*) Then again, they didn't give us a practice reactor to go run
experiments on before first criticality and power ascension; we had to
get it right from basic principles. Needless to say, there definitely
were some tight muscles in certain areas when that day came...but, turns
out theory correctly applied _does_ work and we hit hot zero power
criticality soluble boron concentration within about 10 ppm of the
computed value (1190 vs 1200).
--
On 2/19/2014 4:12 PM, Swingman wrote:
...
> No worries, those who are trained in just about any scientific
> discipline are generally quite capable of recognizing the same in others
> of very different disciplines, Google notwithstanding. <g>
>
> That fact might have a time limit on it though ... ;)
If that's referring to what I'm presuming, I'm forgetting more and at a
more rapid rate every day, too... :(
A fellow at the morning coffee klatch the other morning had seen a Nova
program with Brian Greene wherein he had apparently (I didn't see it)
mentioned getting interested in physics in HS when he realized could
write equations for complex systems and solve for the resulting motion.
I guess the example was the HS physics instructor hypothesized a
baseball stuck to the ceiling w/ a wad of gum and what would happen?
After the obligatory explanation of Newton (the fellow's a geologist,
not an engineer so his physics is even rustier than mine), I explained
how there's an easier formulation altho I doubted that even Dr Greene
knew anything about it at the HS level. So, I started to write the
Lagrangian show him how to set up the two coordinates of angle and
vertical displacement and then...and then...and then... :(
Just been too long. So, anyway, I've spent the evenings last week or so
after that humbling experience glancing thru a couple old texts again
while the Olympics bumbles along in the background...
One thing is clear...the practice w/ the modern computer and things such
as Matlab, Mathematica, and all the other engineering toolsets is a far
cry from the early days when was issued the 20" K+E slide rule when
first reported for duty at B&W NPGD...
--
On 2/20/2014 10:47 AM, [email protected] wrote:
> I hate to keep kicking this horse but... I just received my
> electronic issue if Popular Woidworking today. An article on mallets
> was on theinside. What a coinkydink.
>
> On the topic of dead blows the cabal says:
>
> "Minimal rebound makes better use of the applied force"
>
> How do I get a better use of force here? How did this myth start? I
want to blame someone. Norm? Can I blame Norm? :)
>
> Again if F = ma. And I apply the m a little at a time apposed to all
> at once, how is this a better use of the applied force? ...
You _really_ don't want to get more into the physics of hammers, trust
me... :)
But, besides the conservation of energy, there's conservation of
momentum to be considered and the transfer of energy from/to the target
is also a dependent on the characteristics of both the driver head and
the target.
And, the actual force is an impulse wherein the motion of the hammer
comes to rest in a distance that is dependent on the resistance of the
target--the more resistant, the shorter the distance moved and the
higher the delivered force because that resisting force times the moved
distance must be the same as the kinetic in the hammer to balance the
energy.
A well-designed dead-blow hammer has most of the mass in the head in the
innards so the actual head has essentially come to rest when the
internal mass then delivers the blow. The effectiveness comes from the
more effective transfer and less recoil energy that doesn't go into the
target with a conventional hammer head.
And, that's all I'm going to say and I'm _not_ going to go into a
full-blown analysis...if I still had access to a nonliner FEA system I
might be inclined to set up a couple or three examples that could show
what happens w/o having to actually set up the detailed analytical
solution, but having returned to the farm from the consulting gig I
don't. It's a lot like a simplified case of the collision analyses the
major auto manufacturers go through where they actually use such to help
design survivability into their vehicles...
--
On 2/20/2014 1:29 PM, [email protected] wrote:
> What I don't understand in particular are these two phenomena that would seem to reduce the effectiveness of the applied mass:
>
> 1) when the deadblow is accerated toward the object the mass
> (majority) is in the rear of the cavity (from inertia). After the
> deadblow makes contact the mass leaves the rear of the cavity and
> travels to the from and as it does, it decelerates. (Loss of a thus loss
> of efficiency)
>
> 2) there is still bounce back inside the deadblow head. After the
> shot is thrown against the front inside of the deadblow it will
> bounce back. The energy that is lost to internal bounce back should
> equal any energy lost to the bounce back of a non-deadblow mallet of
> equal mass. Correct?
Both, essentially, "no" with a proper choice of materials and
construction. 1) doesn't decelerate except by hitting the head (albeit
some indirectly thru the elements ahead of them) to any appreciable
extent. The benefit comes from the marked difference in recoil energy
lost. The internals don't act as does a solid; it's that
elastic/inelastic thingie again...
--
<[email protected]> wrote in message
news:[email protected]...
> But you still have deceleration. A point that gets at the increased
> efficiency claim. The magnitude can certainly be debated.
>
> I'm not sold on the increased efficiency from a better recoil property for
> the shot. It's still going to recoil. Bang into each other (energy loss)
> and bang into the sides of the cavity (energy loss)
>
> You also have a loss in energy via heat (from banging into each other)
> that doesn't come into play on a solid hammer of equal mass. Again, this
> gets to efficiency. Magnitude can be debated.
>
> I don't think we get a free lunch here. More efficiency from a hammer
> strike with the same amount of mass - not convinced.
>
Look at the swing as a closed energy system. If the hammer bounces back,
that energy came "from somewhere." It came from not driving the object
being struck. When there is no bounce, all of the energy (minus a very
small amount of friction of the shot heating up) gets expended driving the
struck object. That is the only way you can look at it.
--
Jim in NC
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In article <[email protected]>, Lew
Hodgett <[email protected]> wrote:
> There will always be a high end market.
>
> The question remains, "Can you afford it?"
And there are places for the cheap crap. My brother works as a high
steel welder. One of the companies he works for buys $40 angle grinders
for work on site. Why? Because they grow legs and trip into the back of
people's trucks.
But I think a lot of people simply have no clue that when a tool is
advertised as "just like the pros use" it doesn't mean "professional
quality work by people who are proud of their skill and craft", it
means "anybody who can convince somebody else to part with some money".
My $0.02...
--
³Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness
sobered, but stupid lasts forever.² -- Aristophanes
"Lew Hodgett"
>>It's NOT buying cheap garbage,
>>it is the prudent utilization of ones available resources. <wink>
>>It's all a matter of perspective.
--------------------------------------------------
<[email protected]> wrote:
> Ok, I'll let you get away with that one. But, consider a significant
> amount of the comments posted here in regards to the cheap crap that
> floods into our North American market.
>
> The demand for all the cheap shit has destroyed much of the quality
> goods markets that made us great in the first place. All that's left
> is for us to spiral down the drain. It's a slippery slope that
> there's
> not turning back from, at least not as far as I can see.
---------------------------------------------------
It's pretty simple.
To paraphrase a famous country/western song:
You got the money, honey,
I got the time,
You got no more money, honey,
I got no more time.
There will always be a high end market.
The question remains, "Can you afford it?"
Lew
"Mike Marlow" wrote:
> I certainly agree with the thought Dave, but you've seen me post
> about Harbor Freight. There's a lot of stuff that they sell that is
> just fine. There's things I'd be afraid of buying but even that has
> changed over the years. Used to be that I wouldn't buy anything
> with a motor from them and now that's not true. Some of the stuff
> is cheap junk - can't escape that. But - that doesn't paint the
> entire line of products. I too look for some level of quality - I
> think we all do. But, I'm not going to pay 3 to 4 times as much for
> something that just isn't all that much better. The name brand
> market has done a good job of marketing their names, and the quality
> difference just isn't there in a lot of cases.
--------------------------------------------------------
I use H/F for consumable items.
Gloves, chip brushes, pneumatic quick connect fittings,
light weight bar clamps, bottle jacks, some pneumatic hand tools, etc.
Air hoses are strictly a consumable item, with Goodyear rubber hoses
being the possible exception. The price has to reflect the fact they
are
throw away items.
I have yet to find an electric hand tool that can handle the
fiberglass
dust generated when working glass.
For working in glass, you have Milwaukee and you have Milwaukee.
Lew
On Thu, 20 Feb 2014 16:23:14 -0800, "Lew Hodgett"
>It's NOT buying cheap garbage,
>it is the prudent utilization of ones available resources. <wink>
>It's all a matter of perspective.
Ok, I'll let you get away with that one. But, consider a significant
amount of the comments posted here in regards to the cheap crap that
floods into our North American market.
The demand for all the cheap shit has destroyed much of the quality
goods markets that made us great in the first place. All that's left
is for us to spiral down the drain. It's a slippery slope that there's
not turning back from, at least not as far as I can see.
[email protected] wrote:
>
> Ok, I'll let you get away with that one. But, consider a significant
> amount of the comments posted here in regards to the cheap crap that
> floods into our North American market.
>
> The demand for all the cheap shit has destroyed much of the quality
> goods markets that made us great in the first place. All that's left
> is for us to spiral down the drain. It's a slippery slope that there's
> not turning back from, at least not as far as I can see.
I certainly agree with the thought Dave, but you've seen me post about
Harbor Freight. There's a lot of stuff that they sell that is just fine.
There's things I'd be afraid of buying but even that has changed over the
years. Used to be that I wouldn't buy anything with a motor from them and
now that's not true. Some of the stuff is cheap junk - can't escape that.
But - that doesn't paint the entire line of products. I too look for some
level of quality - I think we all do. But, I'm not going to pay 3 to 4
times as much for something that just isn't all that much better. The name
brand market has done a good job of marketing their names, and the quality
difference just isn't there in a lot of cases.
--
-Mike-
[email protected]
On 2/20/2014 2:59 PM, [email protected] wrote:
...
> I don't think we get a free lunch here. More efficiency from a
> hammer strike with the same amount of mass - not convinced.
They're _not_ the same system and that _does_ make a difference in how
they behave.
--
On 2/20/2014 5:19 PM, [email protected] wrote:
...
> Agreed. They behave differently and I touched on the differences in length.
...
Superficially and without proper conclusions, unfortunately.
A demonstration that isn't _exactly_ the same problem, but very closely
related is at...
<http://neilatkin.com/2013/07/31/3-act-physics-momentum/>
--
On 2/21/2014 9:40 AM, dpb wrote:
> On 2/20/2014 5:19 PM, [email protected] wrote:
> ...
>
>> Agreed. They behave differently and I touched on the differences in
>> length.
> ...
>
> Superficially and without proper conclusions, unfortunately.
>
> A demonstration that isn't _exactly_ the same problem, but very closely
> related is at...
>
> <http://neilatkin.com/2013/07/31/3-act-physics-momentum/>
Didn't intend that to sound as snippy as it does, sorry...but, the
problem has much to do with the differences between elastic and
inelastic collisions which is why I pointed out at the beginning of the
subthread you really don't want to get too deeply into the actual
physics because it isn't a trivial problem that can be correctly modeled
with only a couple of masses with linear springs. Hence trying to draw
conclusions on comparison to that as a model isn't fruitful.
While the example video shows an interaction between to solid objects
w/o the inner mass of the deadblow hammer, the difference between the
two shows the fundamental difference in momentum transfer between
(nearly) elastic and inelastic collisions. Therein is the key to the
difference in behaviors in the other as well altho it's yet more complex
to actually model given the second mass. But, for a first
approximation, think of the inelastic case in the video as if that were
the impacting interior mass of the deadblow hammer assuming you could
deliver the blow w/o the container and you've got the start of a
visualization.
--
In article <[email protected]>,
<[email protected]> wrote:
>On Thu, 20 Feb 2014 14:40:05 -0600, Leon <lcb11211@swbelldotnet>
>wrote:
>
>>On 2/20/2014 2:23 PM, [email protected] wrote:
>>> *Should be "of equal mass and close mass distribution"
>>>
>>> And please don't swap the terms. Recoil? Leon likes the term bounce back :)
>>
>>Bounce back = Energy that is not entirely absorbed by the strike and
>>which is deflected.
>
>Right. Energy that isn't absorbed is useless, however that which isn't
>moving the struck object is just being absorbed uselessly as heat
>anyway. I don't see that the lack of "bounce" necessarily makes the
>hammer more "efficient". It just means it's absorbing energy, rather
>than the user's arm.
>
>>Recoil is a good term. Not all of the energy spent inside a bullet is
>>pushing the bullet down the barrel, much is absorbed by the person
>>shooting the gun.
>
>Newton's third law kinda makes this a given.
It also depends on your definition of what an "efficient" hammer blow is
and what its purpose is. If I remember my physics right, there actually
is a _greater_ transfer of kinetic energy to the strcuk object when the
striking object rebounds. Conservation of momementum demands it. On the
other hand, that's based on "inelastic" objects and and when there's
deformation then things are calculated differently.
Maybe the deformation is what you're after, rather than kinetic energy
transfer. I've been away from the math of physics for too long to
figure out or remember how this translates for instance into driving a
tenon into a mortise or other common tasks. I'm sure one of our
engineer participants will address this soon enough. :)
--
Make it as simple as possible, but not simpler. (Albert Einstein)
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
<[email protected]> wrote
> You just contradicted yourself. There is *not* a greater transfer of
> energy if the hammer rebounds. The energy required for the rebound is
> not imparted to the object, which is sorta the purpose of striking it
> in the first place.
What he said. Where did the energy for the mallet come from to make it
reverse direction. From the object being struck not soaking up all the
energy. Been saying that all along.
This horse is about dead, isn't it?
--
Jim in NC
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In article <[email protected]>,
Morgans <[email protected]> wrote:
>
>
><[email protected]> wrote
>
>> You just contradicted yourself. There is *not* a greater transfer of
>> energy if the hammer rebounds. The energy required for the rebound is
>> not imparted to the object, which is sorta the purpose of striking it
>> in the first place.
>
>What he said. Where did the energy for the mallet come from to make it
>reverse direction. From the object being struck not soaking up all the
>energy. Been saying that all along.
>
>This horse is about dead, isn't it?
>--
>Jim in NC
>
>
>---
>This email is free from viruses and malware because avast! Antivirus
>protection is active.
>http://www.avast.com
>
Check out the math. If we're talking about kinetic energy and conservation
of momentum, more will be transferred to the struck object in an elastic
collision, where the striking object by definition is free to rebound and
there is no permanent deformation of either object. Of course, most of
the time in woodworking, we're NOT talking about an elastic collision and
it's not what we want either.
--
Often wrong, never in doubt.
Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
On Sat, 22 Feb 2014 00:52:14 +0000 (UTC), [email protected]
(Larry W) wrote:
>In article <[email protected]>,
> <[email protected]> wrote:
>>On Thu, 20 Feb 2014 14:40:05 -0600, Leon <lcb11211@swbelldotnet>
>>wrote:
>>
>>>On 2/20/2014 2:23 PM, [email protected] wrote:
>>>> *Should be "of equal mass and close mass distribution"
>>>>
>>>> And please don't swap the terms. Recoil? Leon likes the term bounce back :)
>>>
>>>Bounce back = Energy that is not entirely absorbed by the strike and
>>>which is deflected.
>>
>>Right. Energy that isn't absorbed is useless, however that which isn't
>>moving the struck object is just being absorbed uselessly as heat
>>anyway. I don't see that the lack of "bounce" necessarily makes the
>>hammer more "efficient". It just means it's absorbing energy, rather
>>than the user's arm.
>>
>>>Recoil is a good term. Not all of the energy spent inside a bullet is
>>>pushing the bullet down the barrel, much is absorbed by the person
>>>shooting the gun.
>>
>>Newton's third law kinda makes this a given.
>
>It also depends on your definition of what an "efficient" hammer blow is
>and what its purpose is. If I remember my physics right, there actually
>is a _greater_ transfer of kinetic energy to the strcuk object when the
>striking object rebounds. Conservation of momementum demands it. On the
>other hand, that's based on "inelastic" objects and and when there's
>deformation then things are calculated differently.
You just contradicted yourself. There is *not* a greater transfer of
energy if the hammer rebounds. The energy required for the rebound is
not imparted to the object, which is sorta the purpose of striking it
in the first place. There is no such thing as conservation of
momentum, in this case. There is *always* conservation of (matter
and) energy.
>Maybe the deformation is what you're after, rather than kinetic energy
>transfer.
Deformation is kinetic energy transfer. You're converting the kinetic
energy into heat (still kinetic energy with perhaps some potential
energy in a chemical/physical state change).
>I've been away from the math of physics for too long to
>figure out or remember how this translates for instance into driving a
>tenon into a mortise or other common tasks. I'm sure one of our
>engineer participants will address this soon enough. :)
It all turns into heat. ;-) You're trading the kinetic energy from
the hammer into heat from friction (heat/kinetic energy) of the
mortise into it's tenon.
On 2/18/2014 6:09 PM, Larry W wrote:
> In article<[email protected]>,
> Leon<lcb11211@swbelldotnet> wrote:
>> oN 2/18/2014 9:15 AM, [email protected] wrote:
>>> Consider this:
>>>
>>> A large force that is delivered in smaller doses is not as efficient
>> at driving a joint home as one force all at once.
>>
>> Perhaps in theory. but in real life, the impact driver works with
>> multiple lighter strength impacts. Its the multiple impacts that
>> produce more work in a given period of time. A larger single force may
>> be way too much or simply not enough.
>>
>
> I believe the flaw to that argument is that an impact driver in fact
> does NOT use multiple lighter strength impacts, but actually, due to the
> nature of impact, uses momentarily HIGHER forces than the static tool
> torque spec would imply.
>
>
>
>
I don't know, I can hold the impact with a large enough socket, with my
bare hand, with a little slippage.
On 2/20/2014 2:23 PM, [email protected] wrote:
> *Should be "of equal mass and close mass distribution"
>
> And please don't swap the terms. Recoil? Leon likes the term bounce back :)
Bounce back = Energy that is not entirely absorbed by the strike and
which is deflected.
Recoil is a good term. Not all of the energy spent inside a bullet is
pushing the bullet down the barrel, much is absorbed by the person
shooting the gun.
On 2/18/2014 9:15 AM, [email protected] wrote:
> Consider this:
>
> A large force that is delivered in smaller doses is not as efficient at driving a joint home as one force all at once.
Perhaps in theory. but in real life, the impact driver works with
multiple lighter strength impacts. Its the multiple impacts that
produce more work in a given period of time. A larger single force may
be way too much or simply not enough.
>
> Each smaller force would have to first overcome the coefficient of friction before it can move an object. Any small fraction of the force that is below the coefficient of friction is a loss.
Agreed there is that, but addressing the deadblow that you mentioned,
the loose shot works more to dampen the bounce back rather to increase
force. There are all kinds of factors to consider here. The loose
shot's main function is really not to increase the driving force. Your
adding of the loose BB's to fill the void was more of a convenience to
add mass than to add the feature of a dead blow mallet. You have to
have the second impact of loose shot to tweak the mallet to have dead
blow characteristics.
> Consider the extreme : dropping 100 kg of lead weights on a stuck joint at a 1g at a time versus dropping the 100 kg all at once. If the 1g force doesn't break the coefficient of friction you will have very little net joint closure.
That is correct however in a dead blow hammer the loose shot weight does
not have that extreme of a difference to the rest of the hammer head as
the 100 to 1 ratio.
I think your reference to the mallet possibly acting like a deadblow was
whet most of the replies were questioning.
I was just throwing the countless possibilities to be factored in to get
different affects depending on the size of the shot, weight of the shot,
shot weight ratio, size and shape of the shot chamber... ;~)
Just something to think about. ;~)
Either way your mallet looks really cool!
On 2/20/2014 4:46 PM, [email protected] wrote:
> On Thu, 20 Feb 2014 16:06:50 -0600, Leon<lcb11211@swbelldotnet>
>> The mallet head striking an object bounces. The shot hitting the
>> opposite end of the mallet when the mallet bounces back "helps" to
>> cancel out the head bounce back.
>
> Pretty much as I'd have explained it. But however one looks at it, a
> dead blow mallet is a damned useful tool. You don't really realize it
> though until you actually use one.
Now I will say........ I had a dead blow mallet back in the 70's. It
eventually degraded and the plastic disintegrated and left the steel
handle and a shot gun shell sized capsule partially filled with the pellets.
I suspect that a lot of the bounce back is also absorbed by the plastic
material that is used to encase the steel parts.
For the past 20 or so years I have used one of those smaller hammers
with a red rubber face on one end and a yellow plastic face on the
other. The plastic face end is a similar plastic that is used on the
dead blow mallets. My current non dead blow hammer does not have much
bounce back either....
On 2/20/2014 3:31 PM, [email protected] wrote:
> There is bounce. That's my point. The "bouncing" is occurring on the inside of the cavity. A ball dropped from one end of a cavity to the other is going to bounce.
The mallet head striking an object bounces. The shot hitting the
opposite end of the mallet when the mallet bounces back "helps" to
cancel out the head bounce back.