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madkayaker
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Lots?
Im not 100% sure of this but I believe 8.8 stands for Strength of 800 MPa and a yield strength of 0.8 of that.
Tonnage wise that would give 58 tonnes / square inch tensile and 46 tonnes yield. Its the yield thats important.
The csa of a 20mm bolt is 314mm2 or 0.486 square inch
So a load of 22.35 tonnes will permanently deform the bar.
In practice its probably quite a bit higher.
Tonnage wise that would give 58 tonnes / square inch tensile and 46 tonnes yield. Its the yield thats important.
The csa of a 20mm bolt is 314mm2 or 0.486 square inch
So a load of 22.35 tonnes will permanently deform the bar.
In practice its probably quite a bit higher.
wyn
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Thanks for that info Al.
That looks about right as the pump and cylinder didn't feel as though it had maxed out at 33 tons.
I think the main problem might have been poor preperation and cleaning of the shaft, increasing the force needed to push the bearing on. This job has been done a number of times in the past with no probs before.
That looks about right as the pump and cylinder didn't feel as though it had maxed out at 33 tons.
I think the main problem might have been poor preperation and cleaning of the shaft, increasing the force needed to push the bearing on. This job has been done a number of times in the past with no probs before.
madkayaker
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Might have stressed the bar by repeated pushing also would the dynamic load make and differance?
rtbcomp
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Bolt ratings will be tension because they stretch when tightened.
Nearly correct Al. The Cross sectional area should be reduced to allow for the threads being the narrowest and weakest part. Actual minimum diameter of an M20 threaded bar is 18mm, therefore CSA is 254mm2. Theoretical yield strength is just over 16 tonnes.
I guess you have never seen a bearing/ fly wheel puller then that has a bolt on the middle that PUSHES on to the center to pull the outer off.
Also the OP said
That looks to me like compression.
Justme
rtbcomp
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With a 3 legged puller for example, the claws go round the outside of the bearing, the screw engages on the end of the shaft in the centre.
For the bearing to be pulled off the shaft towards the puller the claws must be in tension, the reaction to this tension will be compression in the screw.
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chunkolini
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Dat makes sense.
Just to add to the complications, threaded bar, the stuff I buy from my hardware store has a cheap feel to it, galvanised 'steel' is it a product rated to do anything?
Just to add to the complications, threaded bar, the stuff I buy from my hardware store has a cheap feel to it, galvanised 'steel' is it a product rated to do anything?
rtbcomp
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I see what you're saying, but I reckon that if the yoke is to move in the direction of the green arrow the thread must extert a force on it in the same direction. The reaction to this force must be in the opposite direction, ie compression in the length of the screw included in the thickness of the yoke plus the length outside the yoke below the red bit.
Imagine a point on the yoke above a thread engaged with the thread. As the screw is tightened that point will tend to squeeze the threads together.
Imagine a point on the yoke above a thread engaged with the thread. As the screw is tightened that point will tend to squeeze the threads together.
I'm afraid I think I'm with rtb on this one. The arms would be in tension, the bottom of the thread in compression. The yoke is in bending and I would have thought that the thread in the yoke is in shear. I can't quite get my head around how the top part would be in tension....
wyn
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Spot on Chunko..........we were supplied with stuff that wasn't 8.8
Used the right stuff and no problems.
I'll post a couple of pics of tonights work and what we were up to with it.
