torque setting calculations Options

[JFG]

I've discovered that my torque wrench only goes up to 160 ft lbs. I need another 50 ft lbs to lock up the rear drive shafts into the wheel bearing hub.

I have an angle gauge and was wondering if it is possible to convert the remaining 50 ft lbs into degrees for the angle gauge?

[barefoot]

Don't think an angle gage would work as the # of degrees of rotation is highly dependent on how tight the nut is.
You're better off by using your longest breaker bar and determining how much weight you're putting on it.
Say you have a 24" breaker bar and you stand on it with your 200 # body weight, that's 400 ft-lbs assuming you have the bar horizontal when you step on it.

[JOEPROPER]

I'd buy another torque wrench if i were you. Or borrow one.

[iankarr]

I bought a high range torque wrench from HF for 65 bucks with one of those 20% off coupons. Not super cheap, but less expensive and scary than losing a wheel at speed.

https://www.harborfreight.com/3-4-quarter-i...wrench-808.html

You'll also need 30mm X 3/4 socket.

If you're comfortable with the force/lever method, here's a great calculator...

https://www.sensorsone.com/force-and-length...que-calculator/

Enjoy!

[Tbrown4x4]

Borrow, rent, or buy the proper torque wrench. The wrench should also make the torque value somewhere in the middle of it's range if possible. As you get toward the minimum or maximum of the range, the torque will be less accurate.


Bolt clamping force is based on the bolt stretch. You can calculate the required torque, because you know how much the bolt will stretch in say, 180 deg. It will rotate 1/2 thread, and depending on thread pitch, it will stretch the bolt a certain amount, and provide the necessary clamping force.

But, you still need consider the material of the bolt and what it's threaded into.

Just borrow a torque wrench. (IMG:style_emoticons/default/smile.gif)

PS: I would be leery about how well taken care of the auto parts store tool rentals were. Find a friend, or take it to a shop for final torque

[Mark Henry]

Don't think an angle gage would work as the # of degrees of rotation is highly dependent on how tight the nut is.
You're better off by using your longest breaker bar and determining how much weight you're putting on it.
Say you have a 24" breaker bar and you stand on it with your 200 # body weight, that's 400 ft-lbs assuming you have the bar horizontal when you step on it.

It's not a critical value like a rod bolt, so this method works fine.

[jd74914]

(IMG:style_emoticons/default/agree.gif)

I always just stand the correct length outon a breaker bar.

[Tbrown4x4]

Sorry for the general, too detailed answer. Early in my mechanical career, I had 2 customers almost lose wheels on my account. I've been pretty anal about torque specs ever since. (I have 8 torque wrenches. Is that a cry for help? haha)

Sure, axle nut is less critical hardware. Don't you torque it and then tighten even more to line up the split pin anyway?

[JFG]

Thanks for the info. For now I have used my breaker bar until my tool borrowing neighbour reappears.

[porschetub]

3/4'' drive is the only way to go,I've snapped a 1/2'' breaker bar on my super Beetle years ago, seem to remember they were 217ft/lbs.
Can you buy a large capacity torque wrench in 1/2'' ? Ive never seen one.

[Triaddave]

That is one of those things you check every time you're there. Go as tight as possible, then use the click sound in you shoulder, done.

[Elliot Cannon]

Buying a torque wrench from HF. Standing on a breaker bar. Pretty much the same accuracy. (IMG:style_emoticons/default/av-943.gif)

[stugray]

Buying a torque wrench from HF. Standing on a breaker bar. Pretty much the same accuracy. (IMG:style_emoticons/default/av-943.gif)

Actually the "standing on the breaker bar" is perfectly accurate (assuming you do the calc correctly), but only as good as your bathroom scale.

[Elliot Cannon]

Buying a torque wrench from HF. Standing on a breaker bar. Pretty much the same accuracy. (IMG:style_emoticons/default/av-943.gif)

Actually the "standing on the breaker bar" is perfectly accurate (assuming you do the calc correctly), but only as good as your bathroom scale.

So, if you attached one of these to a 2 foot long breaker bar and pulled till it read 125 lbs. would that equal 250 foot lbs.?

[Mark Henry]

3/4'' drive is the only way to go,I've snapped a 1/2'' breaker bar on my super Beetle years ago, seem to remember they were 217ft/lbs.
Can you buy a large capacity torque wrench in 1/2'' ? Ive never seen one.

I have a 1/2" that goes to 250lbs.
IIRC the beetle torque is higher than the 914, it also has a bigger 36mm head nut. Note just checked US manuals say 250lbs but ROW manuals say 217lbs, I've always done 250 then plus to get the pin holes to line up. This is the beetle figure, likely I did the book spec on my 914. BTW When it comes to torque specs I try not to go from memory, I always check the book.
You're totally correct on removing them, 3/4" breaker bar is the way to go.

[Andyrew]

Ive never torqued the stub axle. I use my cheater bar and pretty much put all my weight on it.

I even leave the cotter pin out. I take out the cv joints with the stub instead of the bolts on the outside as it saves me way to much time.

[Dave_Darling]

So, if you attached one of these to a 2 foot long breaker bar and pulled till it read 125 lbs. would that equal 250 foot lbs.?

If you got the hook on that scale exactly 24" from the center of the nut, that would be 250 lb-ft.

If it was only 23" from the center of the nut, you'd have 250 * 23 / 24, or 240 lb-ft.

--DD

[Mueller]

In the Machinist Handbook, page 1406 there is a method to determine torque via "turn-of-nut" or angle method. However you would need to be able to measure the elongation of the shaft.

According to the book, even using a calibrated torque wrench, the accuracy is +/- 24%
Turn-of-nut or angle method is better at +/- 15% , numbers are better with a computer controlled torque wrench as used by modern factories.

By feel is +/- 35% according to the book.

[Elliot Cannon]

Does the cleanliness of the threads affect the torque as well? Rusty and dirty or clean and lubricated? Wouldn't clean and unclogged threads make for a more accurate torque? Ah! What the hell, I just honk it down tight and throw a cotter key in it anyway. It's worked so far. (IMG:style_emoticons/default/av-943.gif)