Power Drawbar

[Clive FosterParticipant @clivefoster55965]

grubscrew

The butterfly impact wrench is the standard way of doing things and clearly works well given teh correct air pressure. I think my commercial, still unfitted, Align branded unit has some instructions on how to get it right.

Disadvantage is that you need air all the time and have to find the air handling hardware. Which most of us don’t have laying around. Far easier now with E-Bay and push in connectors instead of the screw type. As I use a quiet “suitcase” compressor to run my mist cooler and do occasional blowdown duties I concluded that having the bigger Hydrovane I use for blasting on all the time using, potentially, more electricity was anther thing that the benefits of auto change weren’t worth to me. Guess the Hydrovane would spin up about three times a day to top up the tank so hardly serious but I’d have to run more air lines too.

Electric is far easier to connect and switches simple but mounting will be an issue. I’m unconvinced that tightening with an electric impact is really safe. Those Makita curves clearly show that over tightening is very likely if it runs for too long. You really don’t want to risk jamming thing up good and proper.

Plain drill drive with a variable voltage to control the power for tighten and loosen seems safer and more predictable. Tightening up will always get a bit more torque due to the momentum of the spinning parts. Loosening will always be harder because the motor has to run up from stopped. I suspect that at the same voltage start up torque will always be a bit less than running stall torque. Ideal would be plain drive to tighten and impact to loosen but thats hardly practical.

One not unimportant advantage of using air and a butterfly impact wrench is that there are several fully worked out designs floating around t’net. Homebrew “different” from scratch always takes way longer than you’d expect due to the bits you forgot about and the effort of tweaking et al so it just works.

Clive

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