NEW! Ultimate C/S Prop Wrench Anti Splat Aero

[PerfTech]

Originally Posted by scard

Yeah, Alan, you don't say what Size the wrench is! I have a Hartzell C/S prop on my O320 that I'm certain has a different bolt size (5/8") than that on a O360 . I would love one of your wrenches, but it needs to be the right size .

Sorry about that Scott, you are correct I somehow overlooked that. The wrench is 3/4" as that is the only size we have seen on C/S props. If we receive the requests for a 5/8" we will make those also. I will contact the propeller manufacturers again today and find out the approximate ratio of 5/8" bolt use. Thank you for pointing this out to us. Allan

[Garage Guy]

Originally Posted by The Paintman

He has done the math for us

So he says, but he hasn't showed his math to us. Meanwhile nauga and schristo and others have shown math that indicates that the 0.8 correction factor is a special case, and depends on the force on the torque wrench being applied one foot from the torque wrench head.

I suppose Allan is too busy filling orders to do it, but if anyone else wants to step up and show your derivation of a constant 0.8 correction factor, have at it. And while you are at it, show the derivation for the correction factor for torque wrenches that read in-lbs and newton-meters, as well as a ft-lbs one.

--Paul

[L.Adamson]

Originally Posted by Garage Guy

So he says, but he hasn't showed his math to us. Meanwhile nauga and schristo and others have shown math that indicates that the 0.8 correction factor is a special case, and depends on the force on the torque wrench being applied one foot from the torque wrench head.

The math is incorrectly applied. That click you hear and feel is from pre-set spring tension, depending on the torque setting. It won't make a difference if the handle is 12, 24, or 36 inches..........as long as the same torque number is used (such as 100 foot pounds), and the "tool" remains at 3" length.

What you "feel" while pushing the handle will be different. But the nut won't be turning any more, or any less.........just because the handle is a different length.

[Garage Guy]

Originally Posted by erich weaver

When you set the torque wrench for 100 ft lbs, by definition, you are going to have a force of 100 lbs applied 1 foot from the end of the wrench regardless of how long your wrench is

Or, you might have a force of 50 lbs applied 2 foot from the head of the torque wrench. Either way the wrench reads 100 ft-lbs of torque at its head.

But in the first case the torque at the nut is 100 lbs through a 1.25 foot arm, 125 ft lbs, for a conversion factor of 0.8. In the second case that torque at the nut is 50 lbs through a 2.25 foot arm, 112.5 ft lbs, for a conversion factor of 0.89.

so that's where the 12 inches comes from. When you add the 3 inch extension, you are applying that 100 lbs to the close end of the extension, but more than 100 lbs to the nut at the far end of the extension. Hence the multiplier of 12/(12 + 3) = 0.8

Follow your logic for a torque wrench that reads in in-lbs. Set it for 1200 in-lbs; by definition that is 1200 lbs 1 inch from the torque wrench head. That's where the 1 inch comes from. When you add the 3 inch extension, you are applying 1200 in-lbs to the close end of the extension, but more at the nut. Hence a multiplier of 1/(1+3) = 0.25.

Something is wrong with that logic! 1200 in-lbs just is 100 ft-lbs. Changing the labels on the torque wrench certainly shouldn't change the multiplier...

WOO HOO! Now I can sleep.

Sorry!

--Paul

[L.Adamson]

Another way of demonstrating.

A foot lb. is the force of 1 lb., 12" perpendicular to the pivot point.

If we take 100 lbs, and set it 12" from the pivot point, then it's 100 ft. lbs torque against the pivot point.

If we use a 24" or 36" wrench, we are NOT moving the 100 lbs past the 12" spot on the wrench. It remains at the 12" point. By adding a longer handle, we push with less force, to move that 100 lbs.

With the addition of the 3" tool, the 12" point (which is used for the "foot" in ft/lbs. is now 15". And that's why a fraction is used. 3" & 12" remain as constants.

[Lux Wrangler]

So he says, but he hasn't showed his math to us. Meanwhile nauga and schristo and others have shown math that indicates that the 0.8 correction factor is a special case, and depends on the force on the torque wrench being applied one foot from the torque wrench head.

I suppose Allan is too busy filling orders to do it, but if anyone else wants to step up and show your derivation of a constant 0.8 correction factor, have at it. And while you are at it, show the derivation for the correction factor for torque wrenches that read in-lbs and newton-meters, as well as a ft-lbs one.
- Paul

It would be nice if everyone saw the math and agreed, but somehow I don't foresee that outcome. I could devise an experiment to prove that the torque wrench length matters. That would be science and perhaps wouldn't satisfy everyone either? Perhaps it could settle a bet? anyone?

[380mxc]

My torque wrench Proto model J6014C has instructions and a formula
They use 22.57 for the handle length . If you used there formula the multiplier would be .882 (for that wrench only)

If you use a 3 " extension and want to apply 80ft lbs of torque to the bolt
you would set the wrench at 70.56 lbs

If the wrong multiplier was used for that wrench .8 it would set at 64 lbs

They would be under torqued by 9.6% if .8 was used with this wrench

The best thing to do is check with the manufacture of the torque wrench used and you should have the required information.

Be Safe

Tim

[WSBuilder]

An easy way to demo the induced torque would be to use the tool and a linear (non-settable) torque wrench. Torque a bolt with the extension, then read the required torque to loosen without it.

[L.Adamson]

Originally Posted by Lux Wrangler

It would be nice if everyone saw the math and agreed, but somehow I don't foresee that outcome. I could devise an experiment to prove that the torque wrench length matters. That would be science and perhaps wouldn't satisfy everyone either? Perhaps it could settle a bet? anyone?

Sure, try it.

The wrench will still click at the exact same spot, and the nut rotation will still stop at the exact same spot. I don't care if the handle is 3' or 30'.
It's still based on that 12" (for ft/lb.) & 3". Those numbers don't change.

[L.Adamson]

Originally Posted by 380mxc

My torque wrench Proto model J6014C has instructions and a formula
They use 22.57 for the handle length . If you used there formula the multiplier would be .882 (for that wrench only)

If you use a 3 " extension and want to apply 80ft lbs of torque to the bolt
you would set the wrench at 70.56 lbs

If the wrong multiplier was used for that wrench .8 it would set at 64 lbs

They would be under torqued by 9.6% if .8 was used with this wrench

80 * .08 = 64 lbs. at 12"

3 more inches is .25 of 12"

64 * the additional .25 = 16

64 + 16 = 80