CS Prop Installation

[frankh]

Originally Posted by Joey

Your A&P friend is correct.

I don't want to sound rude, but there is some very dangerous advice being given in here. Advice that could lead to people improperly torquing their propellers.
Absolutely incorrect. The angle does matter. If you require proof, this link does the math to demonstrate.

PLEASE be more careful with this stuff! I hope Dan sees this and adds a caution to his calculator that the values given are only accurate if the extension is kept inline with the tool.

So lets say your torque wrench is set for 100ft lbs. Are you telling me that if I apply 100 ftlbs to the end of the extension with the wrench at zero degrees, it will be a different torque than if applied at 90 degrees?

I need to think about the math but intuitively the wrench is applying 100ftlb at the end of the extension no matter what the angle....

Probably a moot point ayway because I why would you use anything other than a straight wrench when torquing the prop bolts?

Either way,I believe the origional assertion was that if you applied the Twrench at 90 degrees to the extension then you could ignore the extension...This is definatly not true.

Frank

[RVPilotDotCom]

Thanks again for both the offer of the wrench extension ( found one in my tool box that would do - thx. ) and the additional info on places to find torque computations due to adding the additional length.

I think for the most part we are all in violent agreement here, but think about adding the crows foot to the end of a torque wrench as adding a cheater pipe on the end of a socket wrench. The longer the cheater the more torque you produce. It won't mater how many socket extensions you put on that socket wrench, until you bring out that cheater pipe that nut is not coming off.

So it is with the addition of the crows foot, it's like adding a mini cheater. It will cause a small increase in torque that has to be compensated for in your computations.


Clear skies,

- Jim

[Joey]

Originally Posted by frankh

So lets say your torque wrench is set for 100ft lbs. Are you telling me that if I apply 100 ftlbs to the end of the extension with the wrench at zero degrees, it will be a different torque than if applied at 90 degrees?

Yes. Anthing other than 90 degrees will change the mechanical advantage.

I need to think about the math but intuitively the wrench is applying 100ftlb at the end of the extension no matter what the angle....

I can see how it would appear so, but once you do the math it becomes clear.

Probably a moot point ayway because I why would you use anything other than a straight wrench when torquing the prop bolts?

I do it every day. Sometimes that's what it takes to get in there.

Either way,I believe the origional assertion was that if you applied the Twrench at 90 degrees to the extension then you could ignore the extension...This is definatly not true.

Frank

It's 100% true.

[Joey]

Originally Posted by RVPilotDotCom

So it is with the addition of the crows foot, it's like adding a mini cheater. It will cause a small increase in torque that has to be compensated for in your computations.

Only if it adds the effective length of the tool. A crow's foot oriented 90 degrees to the wrench does not add to the effective length and adds no mechanical advantage.

[William Slaughter]

If anybody still doubts this issue, please follow the link Joey provided and do the math before posting. And thanks for the link, Joey. I'm going to save that PDF in my technical ref files.

William
Mechanical Engineer in a previous job lifetime.
Done the math on this issue quite a few times.

[RV_7A]

Why do the math when you can use this tool????

http://www.cancutter.com/downloadPro...Calculator.exe

[Joey]

That is a handy tool. I'm glad to see this included:



Also, thanks to Dan C. for adding that caution notice to his online calculator.

[Kevin Horton]

Originally Posted by frankh

So lets say your torque wrench is set for 100ft lbs. Are you telling me that if I apply 100 ftlbs to the end of the extension with the wrench at zero degrees, it will be a different torque than if applied at 90 degrees?

I need to think about the math but intuitively the wrench is applying 100ftlb at the end of the extension no matter what the angle....

Probably a moot point ayway because I why would you use anything other than a straight wrench when torquing the prop bolts?

Either way,I believe the origional assertion was that if you applied the Twrench at 90 degrees to the extension then you could ignore the extension...This is definatly not true.

Sorry Frank, but you need to go back to physics class.

CASE 1 - extension in line with torque wrench

Let's assume you have your torque wrench set to 100 in-lb. Let's assume the distance between the hand grip and the square drive for the socket is 10 inches. If you put a socket on the wrench, and put it on a nut, you'll need to pull on the hand grip with a force of 10 lb to create a moment (torque) of 100 in-lb.

Now, let's imagine that you have an extension that is two inches long. You mount the extension so that it is aligned with the axis of the torque wrench, so the end of the extension is now 12 inches from the hand grip on the wrench. You put a socket on the extension, put it on a nut, and pull until the torque wrench clicks at 100 in-lb. How much torque have you put on the nut? The torque on the nut is the sum of two things:

1. The torque wrench applied a moment of 100 in-lb to the extension, and this moment is reacted at the nut.

2. You pulled on the torque wrench hand grip with a force of 10 lb, and this force is reacted where the torque wrench is attached to the extension. The 10 lb of force on the end of the extension creates a torque at the nut of 10 lb x 2 inches = 20 in-lb.

The total torque applied to the nut = the sum of 100 + 20 = 120 in-lb.

CASE 2 - extension at 90 deg to torque wrench

The 10 inch long torque wrench is still set to 100 in-lb. But now the 2 inch long extension is at 90 degrees to the torque wrench axis. We put a socket on the extension, put it on a nut, and pull until the torque wrench clicks at 100 in-lb. How much torque have you put on the nut? The torque on the nut is the sum of two things:

1. The torque wrench applied a moment of 100 in-lb to the extension, and this moment is reacted at the nut.

2. You pulled on the torque wrench hand grip with a force of 10 lb, and this force is reacted where the torque wrench is attached to the extension. This force is transferred through extension, and is reacted at the nut. How much torque does this force create at the nut? Well, the force is actually aligned with the axis of the extension. This is just like putting a wrench on a nut, and then pushing on the end of the wrench so that the direction of the push is directly towards the nut. You can push as hard as you want, and the nut won't turn, as the axis of the force is directly through the nut. The distance between the axis of this force and the centre of the nut is 0 inches, so the torque = 10 lb x 0 inches = 0 in-lb.

The total torque applied to the nut = the sum of 100 + 0 = 100 in-lb.

[captainron]

Guys, this one's so easy it's silly! Hammer a nail about half way into some solid surface like a doorframe. If you are using a 3/8 drive torque wrench, hang the box end of a 3/8 inch combination wrench on the nail. Bring the open end of the wrench up to a level position, and slide it over the drive end of the torque wrench. Have the torque wrench set at its lowest setting. Now, with the torque wrench at a 90 degree angle to the combination wrench, steady the drive end of the torque wrench with one hand and apply force to the handle end of the torque wrench with your other hand. Make sure you are applying this force perpendicular to the handle. When the set torque is reached at the drive end, the wrench will "click". Have you applied any torque at all to the nail? Of course not! Visualize this with an even longer "adapter", and you'll get the idea.With a very short crowfoot adapter, at 90 degrees to the torque wrench, it probably wouldn't make enough difference- just know that the applied torque will be lower than what the wrench is set for.

[captainron]

Guys, this one's so easy it's silly! Hammer a nail about half way into some solid surface like a doorframe. If you are using a 3/8 drive torque wrench, hang the box end of a 3/8 inch combination wrench on the nail. Bring the open end of the wrench up to a level position, and slide it over the drive end of the torque wrench. Have the torque wrench set at its lowest setting. Now, with the torque wrench at a 90 degree angle to the combination wrench, steady the drive end of the torque wrench with one hand and apply force to the handle end of the torque wrench with your other hand. Make sure you are applying this force perpendicularly to the handle. When the set torque value is reached at the drive end, the wrench will "click". Have you applied any torque at all to the nail? Of course not! Visualize this with an even longer "adapter", and you'll get the idea. With a very short crowfoot adapter, at 90 degrees to the torque wrench, it probably wouldn't make enough difference- just know that the applied torque will be lower than what the wrench is set for.