rubber anchor

[BEAR]

I was thinking about what you are doing. It came to mind that you could do the same with a large rubber bumper, or grommet. If you took two pieces of plexiglass or aircraft plywood, cut out discs that you could place on each side of the grommet, and then screw it down to compress it with an all-thread or bolt going through the middle, you could have thd same thing with a shorter length. If say you needed a 3″ O.D. grommet, could you find one? I think you can at http://cableorganizer.com/grommet/rpd-grommets.htm. Check it out and see.

[edwardModerator]

That is basically what the o-rings in my design are doing. I add about .25″ total length to my e-bay for having two o-rings added on. I also chose o-rings because they are available in many sizes.

Edward

[SCOTT EVANS]

What are your tolerances on the other rings? 1/4″ o-ring is very very big and is much harder to compress.

I have made a 3″ version where the o-ring was a -232 (3.012 x .139 x 2.734) For that one I would make a plate or step on your bulkhead that the o-ring fits snugly over – you should not have to stretch it at all. 2.75″ is probably about right, maybe just a bit smaller. I would make the step between .0625 and .075 tall. This allows the o-ring to compress and expand outward enough.

This type of retention takes much more finesse than others, but when you get it right you can’t move it at all. I took my 3″ version and put it into the middle of the tube, put a piece of PVC that fit the tube to press against the e-bay and used a post driver on the tube. I crumpled the tube and it didn’t budge. It is very secure once you get the tolerances dialed in.

Edward

I was starting with 2-7/8 od, but your saying 3 inch ? Inside of the tube measures 2.90 or maybe thats the coupler.
Im gona have a lot of misc. orings orings before im done!
We gona have to have an oring tossing contest!!! 😀

[SCOTT EVANS]

What are your tolerances on the other rings? 1/4″ o-ring is very very big and is much harder to compress.

I have made a 3″ version where the o-ring was a -232 (3.012 x .139 x 2.734) For that one I would make a plate or step on your bulkhead that the o-ring fits snugly over – you should not have to stretch it at all. 2.75″ is probably about right, maybe just a bit smaller. I would make the step between .0625 and .075 tall. This allows the o-ring to compress and expand outward enough.

This type of retention takes much more finesse than others, but when you get it right you can’t move it at all. I took my 3″ version and put it into the middle of the tube, put a piece of PVC that fit the tube to press against the e-bay and used a post driver on the tube. I crumpled the tube and it didn’t budge. It is very secure once you get the tolerances dialed in.

Edward

Got some orings yesterday. Turns out 3/16″ work for me. 2-7/8 od.
I tapered the disc at a 45 to push up as they sqwezed together.
It will lock it in tighter than a drum, especially with it at both ends.

[Author]

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