Narrowing the PH field

[youngdylan]

Hi Bob I have a Clay Spencer tire hammer which I built at NESM in Aburn, ME 3 years ago. I am very happy with it, if you want to try it out come up to my shop I'm about 3/4 hour North of you in Liberty. PM me if you are interested. wana be

Actually Bob I would say rather than listening to opionated people like me, go and have a play with as many different types as yo can then make your mind up. I'm always the first to admit I'm biased.

[arftist]

Arftist

This is probably right if you're only using a 250mm stroke cylinder. I always recommend going for at least a 300mm stroke for the little additional cost. If you make the pilot height easily adjustable you can always get full strokes for most height tooling.

My Kinyon actually uses a 400mm stroke for this reason and because I've rigged up a circuit where I can use it as a single blow "treadle". The more the tup travels and picks up speed the faster it hits.

I guess air v mechanical is always gonna polarize opinion. I've only ever built or used air ........ and I'm very biased Air hammers rock

Even if you use a longer piston you still are not hitting full stroke when you use taller tooling, unless you can adjust the starting height of the tup, the way you can with a spring helve hammer.

[youngdylan]

Even if you use a longer piston you still are not hitting full stroke when you use taller tooling, unless you can adjust the starting height of the tup, the way you can with a spring helve hammer.

adjusting the pilot height adjusts the "mid point" about which the tup oscillates = adjusting the starting starting height of the tup. Easy!

Extra height of cylinder needed because if the "start" height is lifted so is the "finish" height. Should I do a diagram?

[Mainely,Bob]

Maybe I`m seeing thing wrongly here but aren`t you 2 talking about 2 different things?

One is talking about raising the stroke to allow tooling under the tup while keeping essentially the same stroke.
The other is talking about raising the start point which will also lengthen the stroke.

Seems to me what`s important is velocity of the tup.Longer stroke=more time to accelerate=more velocity at the strike.
I touched on this in another thread about tup connection but am wondering if the reason mechanicals seem to hit harder for the same stroke is because of both the freer moving tup(more inertia) and maybe because a mechanical spring stores and delivers potential energy more effectively than compressing a cushion of air.
I`m not an engineer but I have been known to stay in certain motels...

[youngdylan]

Maybe I`m seeing thing wrongly here but aren`t you 2 talking about 2 different things?

One is talking about raising the stroke to allow tooling under the tup while keeping essentially the same stroke.
The other is talking about raising the start point which will also lengthen the stroke.

Seems to me what`s important is velocity of the tup.Longer stroke=more time to accelerate=more velocity at the strike.
I touched on this in another thread about tup connection but am wondering if the reason mechanicals seem to hit harder for the same stroke is because of both the freer moving tup(more inertia) and maybe because a mechanical spring stores and delivers potential energy more effectively than compressing a cushion of air.
I`m not an engineer but I have been known to stay in certain motels...

Bob I've no experience of mechanicals so I don't know how the are adjusted.

With the the Kinyon the stroke length (if it was allowed to develop full stroke and not hit something) relies on the inertia of the tup. It oscillates more or less about the position of the pilot. In this case, the pilot position (height) doesn't affect the length of the stroke it just lift the mid point of the oscillation. This is assuming the cylinder is tall enough and you've got the head height above the tup. I dont have mine hitting the rebound spring when the pilot is low down, it's just there for me "in case".

It gets a bit more complicated when it hits something "mid stroke" i.e when the inertia of the tup keep's moving it down even though the air in the cylinder wants to push it up. It's another question were abouts in the "natural" stroke it the optimum position for it to hit

I guess I should try and sketch what I think I'm talking about but I'm feeling all spontaineous today and reaching for the scanner kills that!

Bottom line of all this physicsbabble is it's easy to get maximum hits for a range of material thickness with a long stroke cylinder and adjustable pilot (notice the new Kinyon appears to have an adjustable pilot position)

Am I beginning to just add more heat than light?

[Mainely,Bob]

I think if you could explain "pilot" I`d have it.
I was under the impression that the stroke length was controlled by using air to limit or buffer the end of the stroke in either direction.Is this what the pilot(or pilot valve)does?

[youngdylan]

I think if you could explain "pilot" I`d have it.
I was under the impression that the stroke length was controlled by using air to limit or buffer the end of the stroke in either direction.Is this what the pilot(or pilot valve)does?

I hope this explanation doesn't patronise, or if this (excess) verbiage doesn't help, I'll have go a doing a sketch over the weekend. Remind me if I forget!

I guess it's kinda difficult to explain in words, mean time here's a couple of nuggets that may/may not help.

The pilot is really just like an electrical relay, it switches a bigger valve. It's the bigger valve that does the switching of the air to the cylinder. The pilot just sends a "signal" to the main valve to switch over "states"

The valve can be in one of 2 states:

STATE 1 air pressure is on top of the piston forcing the tup down and the bottom "chamber" of the cylinder is exhausting any air in it
STATE 2 air pressure is below the piston forcing the tup up and the top chamber of the cylinder is exhausting any air in it

As the hammer moves up/down the valve is continually switching between these 2 states. What causes it to switch states is a bit subtle. When it clicks for you it'll click for you but here's my attempt at an explanation.

Stroke length is inherent to the design. In essence the buffer at the top of the cylinder (there's none at the bottom) doesn't control the stroke. It can influence it but that'll just complicate things at this point. Note, as far as I understand it, it's just there to stop the top of the piston (in the air cylinder) crashing into the top of the cylinder. It does however store energy from the tup on its up stroke and returns it on the down stroke.

Right then lets get down to the meat of this stroke malarky.

1. Lets assume the tup is going down and has passed the pilot. This is state 2. In this state, the valve is set so the air so wants to force the tup up BUT (and this is important) the "momentum" of the tup means it keeps going down (but its slowing down )

2. Eventually the air pressure overcomes the momentum of the tup and it begins to move up. This point would be the bottom of the stroke if it hadn't hit any hot steel on the way.

3. As the hammer moves up it passes the pilot which sends a signal to the main valve which now switches to state 1. Now the air wants to push the hammer back down BUT the momentum of the tup keeps it going (but its slowing down again)

4. Eventually the air pressure overcomes the momentum of the tup and it begins to move down. This is the top of the stroke.

5. As it moves down it passes the pilot which sends a signal to the main valve to switch back to to state 2. ............ now we're back to point 1. above and the whole thing begins again.

It's this continuous "trade off" of air pressure and momentum that controls the stroke and speed of the tup. Note, this is just the basic Kinyon valving. I'm sure there's others being used. The modifications I mentioned in previous posts still don't alter the principle. I hardly know how steam hammers work but I think it's a similar principle. Self contained hammers use a VERY DIFFERENT PRINCIPLE.

So what controls the speed I hear you ask?

Well if the exhaust system is blocked, the air in it stops the hammer moving up or down. For the above cycle to work it's imporant that the cylinder "chamber" that does not have air pressure applied can vent any air that is trapped in it. The less air it can vent, the slower the above cycle goes. The exhaust "closure" is controlled by the throttle.

Note Kinyons behave like mechanicals in that they speed up as the throttle is pressed unlike self contained which run at constant speed.

Right then, that's got be enough for you to mull over for now. I wanna kick back drink beer and relax.

Note, I'm a s** with typo's, chances are I've put one in just the wrong place. I'll proof read later

[youngdylan]

Just realised that all the above doesn't actually say where the pilot is. It's the small roller (usually) air "switch" that the tup passes on it way up/down. A cam on the tup activates. The height is usually set so that when the tup is about 2-3 inches or lower from the work it is not "pressed". When the tup rises up by about 2-3 inches or higher it does press the "pilot"

[Mainely,Bob]

Message received and noted.
The pilot is what is switching the air between sides of the piston as I had thought.
Sounds like you`re using an electric limit switch as opposed to a pneumatic one like we favored for the air logic systems we set up.They both serve the same function,just trigger differently.

Your explanation also gets to the heart of what I was talking about with the tup inertia/velocity thing.
Air hammers are relying on the air cushion run thru related valving to arrest movement of the tup at the limits of the stroke.The system is set up so the air is buffering the cycle and attempting to move the cylinder in one direction while the tup is still moving in the opposite direction.In a sense you`re always fighting against either the restriction of the valving/lines or the air cushion while it`s building.The tup never gets to reach it`s true potential because of this.
Longer cylinders and large supply lines/valve ports help minimize the effects but will never eliminate it.

Mechanicals,on the other hand,seem to let the tup use more of it`s energy by slingshotting it back and forth(the "whip") like the air system does but only limiting it at the last possible moment at the top and not at all at the bottom(if adjusted properly).At the bottom of the stroke the springs and related linkage serves more to allow the powering system(either linear or rotary) to continue thru it`s cycle after the tup has stopped possibly adding slight additional mechanical power to the hit,especially in a helve type system.
All this would explain why folks report that mechanicals hit harder than air hammers of the same weight.

So,what am I missing and where have I gone wrong on my path to weighing the application of the theory involved?

[arftist]

Message received and noted.
The pilot is what is switching the air between sides of the piston as I had thought.
Sounds like you`re using an electric limit switch as opposed to a pneumatic one like we favored for the air logic systems we set up.They both serve the same function,just trigger differently.

Your explanation also gets to the heart of what I was talking about with the tup inertia/velocity thing.
Air hammers are relying on the air cushion run thru related valving to arrest movement of the tup at the limits of the stroke.The system is set up so the air is buffering the cycle and attempting to move the cylinder in one direction while the tup is still moving in the opposite direction.In a sense you`re always fighting against either the restriction of the valving/lines or the air cushion while it`s building.The tup never gets to reach it`s true potential because of this.
Longer cylinders and large supply lines/valve ports help minimize the effects but will never eliminate it.

Mechanicals,on the other hand,seem to let the tup use more of it`s energy by slingshotting it back and forth(the "whip") like the air system does but only limiting it at the last possible moment at the top and not at all at the bottom(if adjusted properly).At the bottom of the stroke the springs and related linkage serves more to allow the powering system(either linear or rotary) to continue thru it`s cycle after the tup has stopped possibly adding slight additional mechanical power to the hit,especially in a helve type system.
All this would explain why folks report that mechanicals hit harder than air hammers of the same weight.

So,what am I missing and where have I gone wrong on my path to weighing the application of the theory involved?

Nothing. You missed nothing.Mechanical hammer's stroke actualy increases as the speed increases. Properly adjusted, the tup, when manualy rotated through it's stroke, reaches B.D.C about an inch above the work, allowing for overstroking.

[youngdylan]

Message received and noted.
So,what am I missing and where have I gone wrong on my path to weighing the application of the theory involved?

Possibly I'm giving an explanation to a question that wasn't asked. I've never used a mechanical but the consensus is they hit harder. I'll go with that given that the tup in Kinyon is being cushioned by the air in the cylinder as it hits the work.

What I was trying to explain was how the pilot position affects the optimum height of the work being done. Using a long stoke cylinder and adjustable pilot gives a lot of versatility. I'll typically have my Kinyon set for say 25mm thick work but with a quick tap on my lever that lifts the pilot and I can be working 100mm by 12mm edge on with no loss of impact. Using the 400mm cylinder I can work 150mm edge on with still quite effective blows.

Kinda curious if mechanicals can cover such a wide range of work thickness?

Guess the question really is what do you wanna do with your hammer. If it's mainly drawing out hard and fast build a mechanical. If it's a wide range of applications from drawing through to punching and sliting build a Kinyon. Better still if you're a tinkerer at heart, with time and space to spare, have a go at both.

Might be worth you having a look at some of the videos on the Pheonix site to see how versatile Kinyons with a tall cylinders are. I'm not totally up on the valving but it's still a Kinyon at heart

http://www.phoenixha...hoenix_demo.htm

[John Larson]

It is not at all commonly agreed that mechanical hammers hit harder than air hammers. It is too broad a statement. Some mechanicals hit harder than others, ditto air hammers.

[Mainely,Bob]

Bummer,something`s wrong with Quicktime on my PC.I get audio only.
Sounds interesting though.

[finn;-)]

The amount of power you are getting out of your utility style air hammer is also determined, by how hard you are pushing it. If you are just barely reaching the stock and gently slapping it at the turn around point, you will get very light blows, which can be very useful. If you smash the treadle down, and the ram is still accelerating as it hits the steel you can get a nice punch, on some hammers you might have to drop the limiter switch down to prevent premature brakeing of the ram, ie buffering, beggining the turnaround...)

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