Torque - the math

Hi !

I need a ghetto dynometric tool to adjust my R&G crash bung , the are fixed to engine by 2 big hex bolts , big one has a torque of 93Nm , and small one 55Nm

Torque = r F sin(alfa)
- (Since sin(alfa)= sin(90º) = 1)
Torque = radius x Force

so:
Torque = wrench length * the strength i aply to it !

Wrench is 40cm long = 0.4m

Im 80kg ~= 800Nm

So if i have the wrench on the horizontal , and apply all my weight on the wrench end , the torque i apply to the bolt is:
Torque=0.4 * 800 = 320Nm

And to make 93 torque ,for the big engine bolt ,i just have to apply all my weight at:
x*800=93 ;x= 0.11m ;
i have to apply all my weight at 11cm from the bolt !


Does this make any sense ?


Taxi

Looks about right, but good luck in getting it done right.

Where are you? I'm sure somebody local with be able to lend you a torque wrench.

Originally Posted by dotted

Does this make any sense ?

I think you can guess the answer.

I'm to far away , Azores islands !


The aluminium frame doesn't look to flexible , I'm just afraid to stress the frame from over doing the bolts !

There are some reports of bent frames from crashes , i wonder if some of them are from over tight crash bungs !

I doubt any body has bent a frame from over tightrening a bolt. I wouldn't stand on the wrench though, Just do the big one up tight about as tight s a car wheel nut, steel wheel and the other about half as tight.

[timwilky]

buy a torque wrench,

TBH I went for years without using one, and even now I use a torque wrench more as confirmation of my "feel".

Once you have stripped a few threads you get to know when you are getting close

Hi matey

just a quick point. there is no way that you could possibly bend the frame enough to permanently distort it by tightening a bolt. AS far as bent frames from crashes go, the bungs are only designed to stop your plastics, frame and other ancilliries from major damage in a lowish - maedium speed crash. They will not be effective unless really lucky) in a major fall.

Also looking at your calcs, if you try and put 320Nm through a bolt you will shear it or strip the threads in what you are inserting it into no worries. To give you an idea I tighten some 25mm bolts only too 195Nm on a hydraulic cylinder that transmits 11 tonne of force.

Ahhh science in action ...

Your theory is sound, but I feel you are better off applying a smaller weight but with a longer moment. I have no idea how you would accurately place you body weight at 11cm from the fulcrum!!

How about this … fill a bucket with some water until you have say 10kg of water (inc bucket), you can measure this on some scales, or do the rough math, water is 1kg per litre. You will then be able to measure a leaver and attach the bucket at the appropriate point. Much less room for error than using yourself as the load!!

How can anyone whether they are American or not use a word like MATH?

It is plural :P Mathematics or MATHS

So if there are two of you does that make you Malcs ?????? :P