VFD on a trip hammer

Mecha

Mecha

Titanium Bladesmith
Knifemaker / Craftsman / Service Provider
Joined
Dec 27, 2013
Messages
10,005
Hi everyone,

I was wondering if anyone else uses a VFD on their trip hammer. I'm using a cheap-o VFD on a 50-lb Little Giant, and love it. It allows using the motor in a simple direct-drive fashion (no gear reduction) while not turning the hammer too quickly with your foot to the floor on the clutch. When doing bulk forging, you just have to set your speed and just step on the clutch instead of slipping the old mechanism to get the speed you want. A 1 hp motor has plenty of power this way for a hammer this size, from very slow speed up to self-destruct mode!

Highly recommended! :thumbup:

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A power hammer is on my list of goals to build in my knife making journey. I acquired a 1hp motor for the build so far. A vfd sounds like a great idea.
 
Hey, when did you get a LG 50? Nice!
My 50 runs off of a VFD, 3 hp motor. I just use the VFD to make 3 phase, with a conventional pulley/speed reduction and the hammer clutch.
Are you saying you have the hammer set direct drive, and use an electronic pedal or some such to vary the speed it runs while working? I believe I've heard of another fella who did that and liked it. I've often thought of trying mine in that mode, just never got as far as sourcing a foot pedal/rheostat for the VFD remote circuit.
 
S.Alexander said:
A power hammer is on my list of goals to build in my knife making journey. I acquired a 1hp motor for the build so far. A vfd sounds like a great idea.
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Yes! On an old mechanical machine like this Little Giant, which is approaching 100 years old, nothing says "I care" like setting it up to run at a nice smooth pace and not stressing the parts. When our new robot overlords lake control, I'm sure they will look kindly upon those who treat their machines well.
 
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Salem Straub said:
Hey, when did you get a LG 50? Nice!
My 50 runs off of a VFD, 3 hp motor. I just use the VFD to make 3 phase, with a conventional pulley/speed reduction and the hammer clutch.
Are you saying you have the hammer set direct drive, and use an electronic pedal or some such to vary the speed it runs while working? I believe I've heard of another fella who did that and liked it. I've often thought of trying mine in that mode, just never got as far as sourcing a foot pedal/rheostat for the VFD remote circuit.
Click to expand...

Just got the hammer up and running a couple of months ago. It had been sitting on a trailer exposed to the weather on the Oregon coast for about 7 years and was a mess, but after tear down, cleanup, re-assembling and a good grease job, it works like a charm. :]

The VFD was used because the 1750 RPM motor is hanging on a hinged mount, with the double V-belts just wrapped around the drive drum of the LG (simple direct belt drive without extra gear reduction). Even with a tiny drive pulley, at full speed with no other gear reduction, with the clutch fully engaged it would run way too fast for the old machine. So using a VFD makes mounting a motor very simple and easy, and then you can just set the top speed at a nice sweet spot and use the normal clutch casually without slipping it on a super fast rotating drive drum. I'm sure this will save a lot of wear and tear on the machine.

It sure is nice to be able to set the hammer's top speed limit and use it normally from there. It makes controlling the speed easier for the scatter-brained forger.

I don't have a foot rheostat control for the VFD, but would like to do that (and a true direct drive) for my next home-made trip hammer, the s.a.m. hammer mk IV.
 
A lot of guys use VFD's to convert 3-phase power to bigger self contained hammers.
 
I've heard of folks using a VFD to convert single phase to three phase but never anyone using direct drive. How does it work? When you turn it on does the ram move up and down or do you have to turn the speed up to get it going? Is it possible to do single hits? I'm not sure I could get used to that!

-Clint
 
Augus7us said:
I've heard of folks using a VFD to convert single phase to three phase but never anyone using direct drive. How does it work? When you turn it on does the ram move up and down or do you have to turn the speed up to get it going? Is it possible to do single hits? I'm not sure I could get used to that!

-Clint
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Sorry for the confusion, I meant no step pulleys for gear reduction. The hammer's clutch is still used, it's just that the drive belt is directly wrapped around the hammer's drive cyinder from the motor. I believe this would be too fast for the hammer without the VFD to slow it down. Apart from that, I love being able to set the top speed of the hammer with the clutch fully depressed.
 
If you have the right diameter motor pulley it works fine- as long as the motor is 1725 rpm and no more.
My hammer motor has a small double-v pulley- 2.4” pitch diameter, (with 4L belts) which will yield +/- 348 rpm at the hammer shaft with the drive belts right over to the 12" hammer pulley and it works well at 60 Hz. The literature for the hammer states a target top speed of 350 bpm.
That said, you're right, it's nice to be able to dial it down. In my case, for when students are learning to run it!
 
That's nearly 6 hits per second! :eek: Nice to know it can run at that speed. I guess it's all a matter of tuning the hammer's spring tension etc.
 
It is fast. They have to be tuned up well to manage it without flailing or fluttering. Mine is not perfect, but working with it you adapt to how to work the treadle to run it smoothly. It's just nice to have that bit of extra stomp when you really hit the gas.
 
While they are not as nice as a air hammer as far as using tooling a well tuned LG runs like a machine gun and will draw out steel very,very fast..
 
This is interesting, because I haven't heard of anyone using a VFD on a power hammer before. I recently bought this 25# LG, serial #8000, and plan to fully restore it. Now you are making me consider whether I should add a VFD or not! Currently I have a Leeson 1.5hp/1725rpm motor on order, with a 2.5" double-groove pulley to achieve the recommended 350 +/- Ram rpm's. It's only a single phase motor (115/208-230V), so would this work with a VFD? I'm not an electrical-type, so this stuff gets lost on me sometimes.

Yes, she's a little worn and rusty, but that's ok... she's all mine :)

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