NEW! Ultimate C/S Prop Wrench Anti Splat Aero

[Mark Albery]

I've just had a quick look at the thread, and there seems to be quite a mix of fact and fiction here, so thanks to schristo for showing the free body diagram.

Torque is the product of a force and the perpendicular distance from that force to the point of application.

So if you're applying the force at 90 degrees to the wrench then the torque measured (at the wrench) is that force times distance to the end of wrench, and the torque applied to the nut is force times distance from wrench handle to the nut.

So the correction is the ratio of those two distances. Put the crowsfoot at 90 degrees and the distances are the same, so no correction, but otherwise the correction will depend on the length of wrench and length of crowsfoot offset.

schristo has it right.

[gstone]

Any torque wrench is set to measure the torque where it attaches.... 6 inches long or 4 feet long matters not! It is set to measure the applied force at the attach end. So that measure is constant no matter how long Your wrench is (pun intended) the only thing that changes is the .25 foot long extension that you attach to the end of your torque wrench and that is why the correction is always the same!!

My opinion, I believe it, has not one thing to do with religion.

[TThurston]

This discussion raises a question that has concerned me. I have two torque wrenches (cheap and expensive)

Is there a way that I can use wrench B to test the torque applied by wrench A?

Or, can I use my wrench that's newly calibrated to test the torque applied to nuts before calibration?

Or, can I use my basic torque wrench to test the torque applied when I use the device discussed in this thread to see if 0.8 really is the correct value?

Or in general, do I just trust my torque wrench or is there a way I can test it?

[marchudson]

The length of the wrench does matter.
Have a look at the formula for calculating crows foot extension.

Wrench torque = Torque Spec * (Wrench length / (Wrench length + Crows foot extension length))

You can't just multiply your desired torque by .8 and expect to get the value to place into your torque wrench. This .8 value works for a 12" / 1 foot torque wrench only.

The attached image might help clear things up a bit. It assumes that you want to apply 100 FT-LB of torque to a bolt using a 3" extension using three different length torque wrenches. A one, two, and ten foot torque wrench. If you just multiply the 100FT-LB value by .8 and dial in 80 FT-LBS in your torque wrench, you can calculate the different values you will obtain.



As you can see above, you won't be getting 100 FT-LBS of desired torque unless you are using a 1ft torque wrench.
Stick with the formula and it will tell you what value to put into your torque wrench.

[gstone]

The change only happens between A and B because all the wrenches apply 80 lb ft of torque to the "B" location and B x 1.25 = 100 lb ft of torque....

I believe!.....

[Ironflight]

Genius Alan - pure genius! You've managed to keep your ad at the very top of the "New Posts" for over a day!

I'm putting one of your wrenches on my wish list. Now, of course, you need to make one that fits the prop bolts on our WW 151 (I think they are 5/8" heads, but I might be wrong...) - they are different from our Hartzells.

[Mike S]

Originally Posted by PCHunt

The reason length doesn't matter is that the torque wrench is indicating the torque on the nut, and not the force on the end of the wrench.

Yep

A wrench handle can be any length, and if the torque reading is calibrated at the nut end of the wrench, it will tell you the torque on the nut, which is what you want.

Yep again

You guys are confusing the nut torque with the force needed at the handle.

All torque wrenches read TORQUE AT THE NUT, not force on the end of the handle.

That's why the length of the handle doesn't matter for torque wrenches.

Taking all bets!

Only problem here is torque is a rotational force, around a center point.

Adding the extension changes the location of the center point of rotation, and the head on the torque wrench is now moving in an arc, not rotation.

All that said, I still think the .8 formula is correct, not too sure of the logic presented above-------Pete's or mine

[PerfTech]

Originally Posted by Ironflight

Genius Alan - pure genius! You've managed to keep your ad at the very top of the "New Posts" for over a day!

I'm putting one of your wrenches on my wish list. Now, of course, you need to make one that fits the prop bolts on our WW 151 (I think they are 5/8" heads, but I might be wrong...) - they are different from our Hartzells.

"Thank You"!!!!!
It is slowing down a little on the posts so apparently I am going to have to stir it up with the announcement of the new coating we are thinking about changing over to. It's called "Skuzmolimide 151" and I am absolutely positive that we have many experts here with lots of experience in the use and application of this product ( any and all information can only help). Thanks, Allan

[Lux Wrangler]

Taking all bets! - PCHunt

BTW...I assume the smile face means no one is actually taking bets in real life? We are just having a friendly discussion?... right?

[scard]

Originally Posted by Ironflight

Genius Alan - pure genius! You've managed to keep your ad at the very top of the "New Posts" for over a day!

I'm putting one of your wrenches on my wish list. Now, of course, you need to make one that fits the prop bolts on our WW 151 (I think they are 5/8" heads, but I might be wrong...) - they are different from our Hartzells.

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 .