Roadster polybush sleeve tubes
Keune - 27/11/20 at 10:07 AM
Hi,
I am currently building new rear wishbones, on the inboard side with poly bushes and outboard rose joints.
I used tube Ø33,7 x 2,6 for the poly bush tubes, as per the book, but I have the feeling the poly bushes are too loose in there.
They slide in easily by hand, which is not what I know of experience with the classic rubber bushes, where at least a vice and some grease is
necessary to get them in the end tubes.
The last I want is ending up with a car that swarves all over the place because of this.
What is your experience or advice to this? Is this ok or shall I replace the bush tubes by Ø33,7 x 3,25mm?
The poly bushes are the typical orange ones.
https://www.dropbox.com/s/fvctx4af9zw4gpb/20201125_163448.jpg?dl=0
https://www.dropbox.com/s/mbxw56fvschqt6p/20201126_204211.jpg?dl=0
[Edited on 27/11/20 by Keune]
Slimy38 - 27/11/20 at 12:35 PM
I also used that same 33.7 tube, and my poly bushes go in by hand. As far as I understand it, it's because it's a bendy rubber with a hole
through the middle!! It's only when I put in the inner sleeve that things tighten up. If you want to compare it with other rubber bushes, try
putting the inner sleeve in the bush first, then try and get it into the tube. You should find that 'by hand' is no longer an option.
By the way, I think you ought to revisit those lower wishbones. You've removed all triangulation by having the rose joints mounted like that.
[Edited on 27/11/20 by Slimy38]
Keune - 28/11/20 at 12:14 PM
Please see this short video I just made:
https://www.dropbox.com/s/bkvfd5l5hex99t3/20201127_171920.mp4?dl=0
The rod ends induce some offset in the triangulation, that's true, but I don't expect that to be an issue as the M12 rod ends, their
threaded bosses and the tubing should be plenty strong.
I bought the rod ends and bosses from McGill Motorsport. They can only be welded in one way.
[Edited on 28/11/20 by Keune]
voucht - 28/11/20 at 02:49 PM
Hello Keune,
I'm sorry but I have to agree with Slimy on that one. And I'm pretty sure I will not be the only one here. Your wishbones do not look OK to
me either.
Here is a picture of Haynes Roadster (MX5) wishbones transformed for rose joints. They are from Rosco, and for I chose them as an example because his
car was one of the finest Haynes Roadster I have ever seen being built (you can check his build thread on the Haynes forum :
http://forums.haynes.co.uk/showthread.php?t=13517)
Photo : https://photos.app.goo.gl/cAaPNAv1XNRQXLWQ8
I think that is how it should be done.
Good luck 
Slimy38 - 28/11/20 at 03:50 PM
quote:
Originally posted by Keune
Please see this short video I just made:
https://www.dropbox.com/s/bkvfd5l5hex99t3/20201127_171920.mp4?dl=0
OK, that seems wrong. I guess it'll be good that it won't bind at any point, but mine are nowhere near that loose. I have just double
checked my order email, it's definitely 33.7 x 2.6mm. I couldn't do what you did in that video. I'm assuming you've checked the
inner sleeve and that is correct book measurements? It wouldn't be the first time I've heard about bushes not being quite the right size.
quote:
Originally posted by Keune
The rod ends induce some offset in the triangulation, that's true, but I don't expect that to be an issue as the M12 rod ends, their
threaded bosses and the tubing should be plenty strong.
I bought the rod ends and bosses from McGill Motorsport. They can only be welded in one way.
Triangulation only works if there are straight lines between the corner. You are right that the rod end, the threaded boss and the tubing will not
break. It'll be the weld just behind all of that which will break. The picture voucht posted shows a much better solution, both for wishbone
fixing to the side of the boss and a brace between the two.
[Edited on 28/11/20 by Slimy38]
Keune - 28/11/20 at 05:43 PM
That's a seriously impressive build!
I'll do some more tweaking on the wishbones.
Thanks for your positive feedback.