Tech Question For Saab Clutch Cylinder Spacer Design

[problemchild]

In my conversion, I need to add 1.8" to the spacer for the Saab clutch cylinder (as shown).

The easy way is to machine another "donut" spacer that is 3.5" OD and 2.6" thick. Easy being a relative term, as the raw material will be a nice chunk of change, and there would be a good chunk of time in the machining. It would also be heavy.

An easier way would be to use the current .8" thick donut and use three 1.8" long x .5"OD standoffs to space the donut to my desired distance using longer bolts. I can buy 2" long aluminum standoffs from McMaster Carr and shorten in a few minutes, making it a $10/10 min job.

So my question is ...... is there radial loads involved that make my idea problematic? The 1/2" OD standoffs are the appropriate diameter for the width of the machined surfaces on each end, but I could make 3/4" OD work too, or I could make the standoffs out of 1/2" x 1" square material.

For reference, the bolts are M6 x 1.0 and 100mm length will work for either option.

I would appreciate input. Thanks!

[DaveW]

I think you meant "will there be circumferential loads?"

The answer is yes, there will be, but unless the TO bearing seizes up, they'll be small, just from the bearing drag. What I would do is to use 1" diameter stand-offs machined down to 1/2" diameter away from the ends. That will provide reasonable resistance to circumferential and any other side loading and will not weigh much more than your plain 1/2' standoffs.

Sketch below:

[DaveW]

I re-read your question, so to meet the 1/2" wide restriction in mtg surface, you could machine opposing sides flat on each end down to the 1/2" diameter. Or the 1/2 x 1" rectangular section you mentioned would work and be easier to make, plus if you left it full size for the whole 1.8", it would be stronger.

Another thing to remember (that you likely already thought of) is that you need to support the inner rear closure to keep it from blowing out when fluid pressure is applied.

[problemchild]

I re-read your question, so to meet the 1/2" wide restriction in mtg surface, you could machine opposing sides flat on each end down to the 1/2" diameter. Or the 1/2 x 1" rectangular section you mentioned would work and be easier to make, plus if you left it full size for the whole 1.8", it would be stronger.

Another thing to remember (that you likely already thought of) is that you need to support the inner rear closure to keep it from blowing out when fluid pressure is applied.

Yes, there is something about those 1/2" OD standoffs that just does not seem right. I will figure something out, probably influenced by my aluminum bar inventory. The existing donut (which I will reuse), does support the rear of the cylinder. Thanks!

[DaveW]

Yes, there is something about those 1/2" OD standoffs that just does not seem right. I will figure something out, probably influenced by my aluminum bar inventory. The existing donut (which I will reuse), does support the rear of the cylinder. Thanks!

Yeah, the 1/2" standoffs might have been flexible enough for the slave/TOB mass to get into a harmonic vibration
and loosen/fail due to engine vibrations. The 1/2 x 1" rectangular setup will be less likely to do that because it's a lot more rigid.