tightening torque question for engineers:

[speeder]

Or anyone else that knows. (Not guessing). I have a bolt that needs to be tightened to 260+ lbs./ft. I do not have a torque wrench that goes that high, nor the strength to pull it that hard if it did.

If a 200 lb. man stands on a 1 ft. long breaker bar, is that 200 ft./lbs? How heavy would he have to be on a 2 ft. bar for 260 lbs.? A 3 ft. bar? Better yet, what is the formula?

TIA.

[RWebb]

length of moment arm * wt. (Force)

now here is the next question -- should you stand on 1 foot???

[sketchers356]

Torque=distance x force

Not an engineer, but this is what us physicists use.

So a 2 ft bar with 200lbs on it would be 400 ft lbs

[Hodgey]

Originally Posted by speeder

Or anyone else that knows. (Not guessing). I have a bolt that needs to be tightened to 260+ lbs./ft. I do not have a torque wrench that goes that high, nor the strength to pull it that hard if it did.

If a 200 lb. man stands on a 1 ft. long breaker bar, is that 200 ft./lbs? How heavy would he have to be on a 2 ft. bar for 260 lbs.? A 3 ft. bar? Better yet, what is the formula?

TIA.

In answer to your first question, YES.
In answer to your second question : 130lbs

In answer to your third question
The formula is simple as the answer is in the units ...... ft lbs

Torque Applied = Force x Distance

So, if you weigh 200 lbs and you put all of your weight on a 2 ft bar, then the torque would be 400 ft lbs

[VaSteve]

Breaker bars are for loosening.

[mossguy]

Maybe a tightening bar, then.

Best,
Tom

[DARISC]

Originally Posted by mossguy

Maybe a tightening bar, then.

Best,
Tom

I think you mean a "fixer" bar.
They used to sell breaker bar/fixer bar matched sets.
But not many.

I have my grandfather's neighbor's matched set.
I acquired them just as he had.
I stole them from him.

I got a lot of use out of the breaker bar.
But I used to break a lot of what I was trying to break.
I don't care what they're named, fixer bars are usless.

Unless, you use it like a breaker bar.
I used my fixer for a breaker all the time.
Until I broke it.

An hour later I broke the breaker.
There's only one tool that can, sometimes, fix a breaker.
I had one, but it was broken.

I'd post a picture of the broken breaker,
with the broken fixer laying beside it.
But I can't tell you which is which.

[Flieger]

Make sure you stand on the end. If you distribute your load, you would have less torque.

[red-beard]

You can adjust the torque by standing closer to the bolt. You need to stand at the 1' 3.6" point...Mark it with tape...

[red-beard]

BTW, they sell torque multiplying wrenches

Torque Wrench Multiplier - Compare Prices, Reviews and Buy at NexTag - Price - Review

They ain't cheap, but they's handy...

[IROC]

Another fun equation is that - for most practical circumstances:

T=.2Fd

Where:

T = torque
F = axial force (clamping) that is applied by the fastener during torquing
d = the nominal diameter of the fastener

The ".2" is a friction factor which is a decent approximation most of the time...

So if the fastener you are torquing to 260 ft-lbs is a 3/4" bolt, for instance, then that fastener is generating:

260 ft-lbs (12 in) = .2(F).75

F = 20800 lbs

That's a lot.

[GH85Carrera]

It sounds like you are doing the rear axle bolt on a 911. When I tightened mine I used a 3 foot bar. I marked the spot that was exactly 3 feet from the center point and pressed down while standing on a bathroom scale. I pressed down until the scale showed 86 lbs less than my normal weight.

My math was 86 lbs at 3 feet = 258. The tough part is to keep the pressure so even the scale does not bounce around.

I bought a cheap Chinese made bar that is a 1 inch drive for 30 bucks. The socket cost me more than that.

I am not an engineer but I slept at Holiday Inn once.

[speeder]

Originally Posted by GH85Carrera

It sounds like you are doing the rear axle bolt on a 911. When I tightened mine I used a 3 foot bar.

No. But similar, it's a 36 mm gland nut on a 356 flywheel. It's a one-time use hollow bolt, (don't know why they call it a nut), one challenge is going to be holding engine still enough while tightening. The engine weighs very little.

The car also has 36 mm axle nuts that need to be extremely tight, not as worried about those since you have the entire car to hold still.

Here is what it took to loosen flywheel and axle nutz, a massive 3/4 drive impact:

[Joe Ricard]

breaker / fixer bar. not that is funny!!!!!!

If you own and work on Porsches buy the right tool.

why is it when you torque it down to 263 ft/lbs it takes 4 foot breaker and a pipe extension and me and a friend to bust it loose?

Now I have a pimpin impact wrench, no nut is too tuff to break loose.

[Joe Ricard]

ratchet strap the motor case to the work bench. at least you have a flywheel lock installed.

[rick-l]

Originally Posted by RWebb

now here is the next question -- should you stand on 1 foot???

You should stand with the middle of your foot at 1 foot.

[mschuep]

Make sure the bar is horizontal as well...an angle of 20* from the horizontal would mean 244ft*lb instead of 260ft*lb.

All you ever wanted to know about torque...
Torque - Wikipedia, the free encyclopedia

[1990C4S]

Why not take it to a diesel shop and have them do it right? It will take two minutes.

[sammyg2]

BTW,
Proper lubrication makes all the difference in the world when it comes to torque. Dry threads can require up to 180% of the twisting force to obtain the same percentage of yield as one with say, moly lube or mil spec anti-seize.
On the threads, washer (if there is one) and also on the face of the fastener and the part it's going up agin.

[DARISC]

Originally Posted by IROC

...a decent approximation...

Decent is relative and open to interpretation.

I once presented a GF with what I thought was a decent approximation of our relationship status, which resulted in my making a proposal; I raised the bar and suggested that we try...I won't get into what here.

My point is that what I thought was a decent approximation, and my big mouth, led her to accuse me of making an indecent proposal.

She told me, Back off! So I did, bending my breaker bar in the process.

Boy was she torqued!

She forgave me though. And she straightened my breaker bar.