Torque arm bolt

[Corvus]

I think there is a grade of stainless with a reasonably high yield strength, but I can't remember the reference. The value is something akin to en16, if memory serves. Good, but not quite up to a decent socket head bolt, which exceeds 8.8 usually. GKN used to be the big name back in the day...

[Blackal]

IIRC - 410/460SS is commonly used for knives, so may well have a higher yield strength - albeit...... at the expense of "toughness".

Al

[Dog Tyred]

For heavens sake! Stop dickking about and put a Ti bolt in there if you are remotely worried.

Personally I think you are worrying about absolutely nothing. BMW are not in the habit of underspeccing fasteners! And don't forget the PL arm itself is made of pressed tin!

DT

[Tapio]

Edit: I agree that the threaded portion doesn't matter "theoretically" provided friction alone is sufficient. But imagine if the bolt was, say, 10mm dia and the hole was , say, 12mm dia. Even if the bolt was strong enough to induce friction, would you trust that amount of clearance? If you've done your sums right you should be able to. But would you?

It is totally wrong thinking to have a screw joint where friction is not sufficient, and only survives due to the scew also taking shear load =>back to the drawing board.
If friction is not strong enough to hold the parts, then there will be movement. If there's movement, then there will be wear. As wear increases, screw tension decreases. You will find yourself looking for that screw in the ditch, sooner or later.

If enough friction cannot be had in the joint, then you must have another solution.
Here's a pic of a truck prop shaft: http://www.keoghcommercials.com/details.php?id=24
this is an expensive solution, since the slots need to be press fit (again, no movement!). Tight tolerances cost money.

//T

[Blackal]

I might be misreading your post Tapio, but there are several applications where stressed members are on a floating pin/bolt - clevis.

Shock absorbers are a case in point?

Al

[Tapio]

Shock absorbers have a rubber bushing in each end. Same thing with the paralever torque arm.
But you're right; clevis pins allow movement. And are sometimes used in applications with a lot of force. But that's a totally different joint. The parts are not clamped together like they are with a screw fastener.

[Corvus]

Edit: I agree that the threaded portion doesn't matter "theoretically" provided friction alone is sufficient. But imagine if the bolt was, say, 10mm dia and the hole was , say, 12mm dia. Even if the bolt was strong enough to induce friction, would you trust that amount of clearance? If you've done your sums right you should be able to. But would you?

It is totally wrong thinking to have a screw joint where friction is not sufficient, and only survives due to the scew also taking shear load =>back to the drawing board.
If friction is not strong enough to hold the parts, then there will be movement. If there's movement, then there will be wear. As wear increases, screw tension decreases. You will find yourself looking for that screw in the ditch, sooner or later.

If enough friction cannot be had in the joint, then you must have another solution.
Here's a pic of a truck prop shaft: http://www.keoghcommercials.com/details.php?id=24
this is an expensive solution, since the slots need to be press fit (again, no movement!). Tight tolerances cost money.

//T

That was entirely my point!

We agree.

Edit: yip, prop shafts, to my recollection, utilize "dowel" bolts.

[Corvus]

I might be misreading your post Tapio, but there are several applications where stressed members are on a floating pin/bolt - clevis.

Shock absorbers are a case in point?

Al

There's always a bush up the middle, effectively bearing the load under friction.

[Corvus]

........

A). Stop dickking about.....

B). And don't forget the PL arm itself is made of pressed tin!

DT

A)

B) all the more reason to make sure it's held properly then.

[1200boxer]

Am I wrong or is that an articulated joint?As the swinging arm moves up and down the final drive housing pivots on the pivot pins which means that the torque arm cannot be ridigly attachet to it.

[Dog Tyred]

Am I wrong or is that an articulated joint?As the swinging arm moves up and down the final drive housing pivots on the pivot pins which means that the torque arm cannot be ridigly attachet to it.

You are correct it is a pivot joint so there is a spacer bush in the final drive housing so the paralever arm clamps tightly onto that rather than the main housing. See the example on ebay below.

http://www.ebay.co.uk/itm/Final-drive-r ... 1c4883c538

DT

[1200boxer]

Am I wrong or is that an articulated joint?As the swinging arm moves up and down the final drive housing pivots on the pivot pins which means that the torque arm cannot be ridigly attachet to it.

You are correct it is a pivot joint so there is a spacer bush in the final drive housing so the paralever arm clamps tightly onto that rather than the main housing. See the example on ebay below.

http://www.ebay.co.uk/itm/Final-drive-r ... 1c4883c538

DT

Exactly.The problem is, there's none on the 1200S.A design fault?

[Corvus]

Am I wrong or is that an articulated joint?As the swinging arm moves up and down the final drive housing pivots on the pivot pins which means that the torque arm cannot be ridigly attachet to it.

You are correct it is a pivot joint so there is a spacer bush in the final drive housing so the paralever arm clamps tightly onto that rather than the main housing. See the example on ebay below.

http://www.ebay.co.uk/itm/Final-drive-r ... 1c4883c538

DT

Looks like a metalastik bush? Doesn't really change any of my comments, or the general line of discussion as far as I can see? The bolt clamps the inner steel bush within the metalastik bush (if that is what it is) and so has to withstand the loads imposed upon it.

[Dog Tyred]

Exactly.The problem is, there's none on the 1200S.A design fault?

Really? There appears to be one ( the spacer bearing) on on the images I can see of a R12S bevel box

To quote what's his name Bannatyne " I'm out"

DT

[Dog Tyred]

Looks like a metalastik bush? Doesn't really change any of my comments, or the general line of discussion as far as I can see? The bolt clamps the inner steel bush within the metalastik bush (if that is what it is) and so has to withstand the loads imposed upon it.

oK I'm back in

I give in as I have no idea what you are talking about. Just use the bloody thing and don't worry about it as I'm sure BMW have it covered.

DT