Comments on: Titan’s Ratcheting Breaker Bar

By: Benjamen Johnson

Benjamen Johnson — Thu, 06 Sep 2007 00:49:22 +0000

Yeah, that’s what I meant….Thanks for the correction m4ff3w

By: Craig

Craig — Thu, 06 Sep 2007 00:44:57 +0000

Awesome, thanks Ben (and m4ff3w). Wow that’s a simple formula, I’m pretty sure even I could remember that.

By: m4ff3w

m4ff3w — Wed, 05 Sep 2007 22:50:36 +0000

375ft/lbs != 250lbs * 1.5ft

375ft*lbs = 250lbs * 1.5ft

By: Benjamen Johnson

Benjamen Johnson — Wed, 05 Sep 2007 15:03:02 +0000

Craig,

T = F * d

where:
T is the torque
F is the force used
d is the length of the lever arm

So in the above example the lever arm is 18″ or 1.5′ and the force is 250lbs

T = F * d
375ft/lbs = 250lbs * 1.5 ft.

I could have used a simpler example where the relationship would have been more obvious, like a 2 ft lever with 100lbs of force is 200 ft/lbs, but I was trying to use numbers relevant to the situation.

By: Craig

Craig — Wed, 05 Sep 2007 04:13:15 +0000

Interesting, thanks for the perspective Ben.

Question. What formula (or where did you find the formula) to figure out the 250 lb man 18″ breaker bar rating?

I’d be extremely interested in playing with some different variables.

And yes, I agree about dragging out the air hose/extension cord, those always seem to hinder my likelihood of impact wrench use.

By: Benjamen Johnson

Benjamen Johnson — Tue, 04 Sep 2007 14:11:28 +0000

To put 376 ft/lbs in perspective, if a 250 lb man puts all his weight into an 18″ breaker bar, he can generate 375 ft/lbs of torque. A SAE Grade 5 3/8-16 bolt can take 370 ft/lbs of torque (I’m not sure whether the threads fail or the bolt shears).

That said, yes there are applications that may require more torque, and yes a pneumatic impact wrench (or electric) can generate much more torque. But sometimes you don’t want to drag out the air hose, or you might be away from your garage.

By: Craig

Craig — Tue, 04 Sep 2007 04:25:22 +0000

Ok, I’m certainly no genius, but 376 ft-lbs seems pretty light duty to me. My Dewalt electric impact is rated to 350 ft-lbs, and decent pneumatic Impacts can be rated much higher. Also, at 250 lbs., I don’t see myself being able to hang off the end of a piece of pipe, like I’ve done countless times (damn tire change places) with my standard breaker bar.

Having said that, I think this is a great idea, but I think I’ll wait for the heavier duty model.

By: Old Donn

Old Donn — Mon, 03 Sep 2007 23:32:18 +0000

They don’t call them breaker bars for nothing.

By: Benjamen Johnson

Benjamen Johnson — Mon, 03 Sep 2007 15:42:18 +0000

A safety issue I forgot to raise in the post: How much torque can a standard 1/2″ socket bear before it breaks? Maybe you should also use impact sockets, designed for higher torque, when you are applying 376ft-lbs of torque.