The motor on my hammer packed it up and while I'm searching for a replacement (the original came from a dead compressor with who knows how many miles on it, 15 years ago), I thought back to a conversation I had with Grant Sarver just before he died.

 

Could you use a VFD as the speed control for a powerhammer?   I'm thinking that you could run the belt from the motor to the drive pulley directly, with no clutch.  The VFD would be controlled with a foot pedal.  The more you depressed the pedal, the faster the motor would run, like a big sewing machine.  Could that be made to work?  It sounds to me that you'd have both speed control (from O to OMG) and maybe a single blow stroke.

 

The hammer is a shop built mechanical, like a Champion, with a DuPont toggle arm setup, about 50#.

 

Thanks

 

Geoff

I had a VFD on my lathe before buying a large RPC. It took several seconds for the motor to go from 0 to 60 hertz. Speed changed after the motor was running were not instantaneous either. If I remember correctly VFDs were original created to lessen the inrush current when a motor is turned on by controlling the electrical cycle frequency. I don't know if other VFDs have parameters that can be changed so that speed changes happen faster but I would defiantly say it would not work with the one I had.

 

There was a thread on Practical Machinist recently were some installed a 75lb Fairbanks hammer and removed the jack shaft and the old motor and replaced it with a higher HP but lower RPM modern motor. The new motor without the extra rotational mass struggled to get the hammer moving from a dead stop. Something to think about if there will be no line shaft or clutch pulley constantly spinning.

Vfd / invertors here have loads of parameters, acceleration, deccelerat, braking force, current boost,

on my hammer I set min freq to about 20hz, max to about 50hz, slow accel and fast decel, DC braking to max to stop motor in 1 rev max.

here mains is at 50hz and 240v or 3 phase is 415v

Check out Steve H's post & video at the end of his "New addition to the family" thread about his Beaudry hammer over at the NWBA forum.

I've got 30 hp of 3 ph converter, so I could go that route.  I would like to try this, but right now I found a nice beefy 220 v unit an d I will go with that.  Thanks for the replies.  I'll check the NWBA thread as well.

 

Geoff

I have thought this may work, and I went to the expense of buying a variable potentiometer foot pedal...However I was lucky enough to see a hammer in belgium that ran from a vfd with no clutch, it was pretty lame and had slow response time. I think lack of momentum was the issue, not much beats a fly wheel. I think it would work well with an oversized , over powered motor.