COMET FRONT SPRING BOX RENOVATION

[davidd]

When making the SS rear spring boxes that were available from Justin, the UHMW band was attached to the spring box by cutting a small groove in the new SS spring box. The plastic slider had a complimentary ridge cut into the plastic slider when it was sized on the lathe to fit in between both spring boxes. The slider could then be pushed onto, or into the spring box until the ridge on the slider hit the grove in the spring box. It would snap in place and never move. No glue was necessary.

Unfortunately, Carl introduced grease to the rear spring boxes as well as the plastic slider and the grease attracted sand which ruined the finish on the inner spring box. Justin made a pair of new inners for Carl and I used Carl's damaged inners on my racer. I still have them, but I made a coilover to do away with the spring boxes in 2002.

David

 

[oexing]

For keeping the inner tubes centralized you want the centralizing material to sit on the inner tube to act in the i.d. of the outer tube. So any scratches produced by the proud spots will only happen in the outer tube i.d. and not seen from onlookers. I found the idea on Hagons, they dimple the smaller tube for proud dimples. I did same strategy on my Fournales based oleopneumatics by having IGUS material pressed in the alu components.
You could try same idea from Hagon by having blobs of stainless welded, 4 each ,on the inner tube, and file them so the inner tube just enters the outer with little play . Certainly keep the lot greased, for the springs anyway, gaiters would be good. That should work for very long time when dirt is kept out.

Vic

 

[CarlHungness]

What is UHMW?

Ultra High Molecular polyethlene...looks like a roll of teflon. In the states available from McMaster-Carr.

 

[CarlHungness]

When making the SS rear spring boxes that were available from Justin, the UHMW band was attached to the spring box by cutting a small groove in the new SS spring box. The plastic slider had a complimentary ridge cut into the plastic slider when it was sized on the lathe to fit in between both spring boxes. The slider could then be pushed onto, or into the spring box until the ridge on the slider hit the grove in the spring box. It would snap in place and never move. No glue was necessary.

Unfortunately, Carl introduced grease to the rear spring boxes as well as the plastic slider and the grease attracted sand which ruined the finish on the inner spring box. Justin made a pair of new inners for Carl and I used Carl's damaged inners on my racer. I still have them, but I made a coilover to do away with the spring boxes in 2002.

David

Boy, I don't remember that scenario...I don't think I would have ever greased the spring boxes. and my spring boxes are stock in front, nothing has been machined...and I sure don't recall ever getting a second set of rear spring boxes from Justin...I cannot swear as to what adhesive I used to glue in the UHMW but am confident I would have run a test long before ever trying to insert them. You've got me mixed up with someone else...I'd cop to the mistake for sure, but I have stock front spring boxes and Justin's rear boxes. Just last year the right side UHMW came a little loose on the right side box and now hangs about an inch below where it ought to be, but is still working a treat.

 

[CarlHungness]

Apparently super-glue works:

https://www.mcmaster.com/products/a...nt-bond-adhesives-for-hard-to-bond-materials/

Good one Bruce...I do not recall using super glue, it would not have appealed to me, being in such a small bottle. As stated in my other post I certainly would have run a 2-3 day test on the adhesive, and probably made note of it in my 'logbook' such as it is. Maybe I used the newspaper trick with contact cement, such as one does on a counter top..the newspaper doesn't stick to the contact cement why dry so you can slide paper under your Formica, position it, then slide out the paper. Now thinking of it, it'd be a challenge to roll the UHMW and slide it into a tube without having it stick. Then too, one could make a longer tube of UHMW, wrap it up tightly so you're sure the top goes in, then let it swirl outward so it'll stick all the way down the tube, and if long cut it off. I love doing stuff like that, you think you've accomplished something when it all goes together.

 

[Robert Watson]

UHMW has quite a high co efficient of thermal expansion, so watch out for your clearances if using it in widely varying temperatures

 

[oexing]

Whatever you use for keeping shrouds from scratching each other, you should fix that material NOT in the outer shroud but instead on the inner tube. So only then any minor scratches will show in the i.d. of the outer shroud where it does not matter. Look at my plastic plugs pressed into the alu seal holders. They contact just the outer shroud i.d. in operation, so scratches do not matter at all. Or try the Hagon type dimples by welding proud dimples onto the INNER shroud . That will do many miles with a little grease as you want some grease there anyway for the springs.

Vic

 

[davidd]

you should fix that material NOT in the outer shroud but instead on the inner tube.

Well stated.

David