Strontium Dog
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| posted on 9/11/10 at 09:54 AM |
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Poly bush size?
Hi, I have some 29mm int. 3mm walled CDS tube that I want to make some bush tubes out of. Rally design bushes are spec'd at 28.8mm. Has anyone
used these bushes in this size tube and were they loose?
I'm guessing that it will be OK but I need a lot of bushes and it could be a costly and time consuming mistake if I am wrong!
The other option is what other bushes are available and known to be good quality? The RD ones will all need the crush tubes cutting down to 44mm from
46 as well and as there is 64 of them to do it would be nice to find some with the right size crush tube to start with!
Cheers Si.
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3GEComponents
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| posted on 9/11/10 at 11:18 AM |
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Hi Si,
Ours are 44mm long, bush is 28.5mm in diameter with a 19mm hole in it.
64?  What are you making?
Kind regards
John
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procomp
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| posted on 9/11/10 at 11:57 AM |
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Hi
Are you talking about proper polyurethane bushes or the cheap nasty ones that most manufacturers sell. ?
Cheers Matt
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Strontium Dog
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| posted on 9/11/10 at 12:37 PM |
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Hi John, I'm building a 20 wheel locost!
No, actually I have 4 cars to sort the suspension out on at the moment! This is why I don't want to make a mistake as it's a lot of
materials and work.
Matt, I was hoping for decent quality bushes of course. I presumed (rightly or wrongly) that the ones from Rally Design would be of an acceptable
quality but please correct me if they are not!
The other issue is that I need to know the centre size for the bolt before I machine 64 brackets with the wrong size hole! I have seen 12mm 12.7mm and
I presume that the 19mm mentioned above is without crush tubes!
The question remains, will a 28.8mm rally design bush be OK (assuming they aren't crap) in a 29mm tube or do I need to find different bushes
from Matt or John for instance, or different CDS tube?
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paulf
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| posted on 9/11/10 at 12:49 PM |
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I used some welded seam tube of similar diameter and found that the tolerance plus the weld on the seam held the bushes securely.If its accurate and
seam less then the bushes are going to be loose with .2mm clearance.
Paul
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procomp
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| posted on 9/11/10 at 03:29 PM |
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Hi
The rally design ones should be OK. Although i personally prefer the super flex items. If it has a shore rating of 80 it should be OK in the slightly
bigger outer housing Although this depends upon the dimensions of the inner pivot tube Which will determine how much of am interference fit it will
all be as a final assembled unit inside the outer housing.
These types of bushes should be fitted into a smooth bore rather than a seamed tube. If there is any rotation of the bush it will start to shred on
the welded seam. Also do the Rally design items come with stainless steel inner pivots. Mild steel items are of no use what so ever in this
application.
As i say personally i use the Super flex items every time as they are manufactured to a very high tolerance and are self lubricating and come with the
stainless pivot tubes as well as packets of lubricant specifically for fitting the bushes.
Cheers Matt
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D Beddows
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| posted on 9/11/10 at 04:01 PM |
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and Super Flex are really nice people to deal with as well
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Minicooper
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| posted on 9/11/10 at 04:54 PM |
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The rally design ones look simliar to these rock hard plastic ones you see but are compliant like the superflex type, the crush tube is stainless
steel but like you say 46 instead of the usual 44. The rally design ones are far cheaper though so it may be worth it to you to take 2mm of the crush
tube or if you haven't made the brackets yet get some brackets made to suit. The superflex ones are premier stuff but they are very expensive
compared to others. The rally design type crush tube uses 1/2 bolts as opposed to the 12mm typically found on the hard plastic type.
I used the rally design ones as my brackets could be any width to suit
Also using the plastic type on live axles which I assume your doing can't be a good idea can it?
Cheers
David
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Strontium Dog
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| posted on 9/11/10 at 05:21 PM |
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Matt, CDS is seamless as I am sure you know already and I completely agree with what you are saying! I don't want to use seamed tube even though
I could clean up the weld, why spoil the ship and all that! I want to use the 35mm 3mm wall CDS if I can get away with the bushings. So you think that
I am right and the little bit of extra tube clearance should not be an issue then? I may order a couple of bushes and have a play, unless someone has
a spare pair they don't need (blag blag!).
Minnicooper, I am not going to use hard plastic and I am using IRS on all 4 cars. I have just started machining my brackets from 50mm 3mm wall box
section. This is why I want the 44mm crush tubes. No problem trimming them to 44mm from 46mm as long as they are going to fit the 29mm smooth bore of
my rod end tubes without rotating! The rotation should be around the crush tube and not within the bush housing, hence my concerns as to the extra
0.2mm. Rally Design could not answer this query.
Rally design bushes are just over £3.00+twat each inc. stainless crush tube if you buy 20+
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Minicooper
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| posted on 9/11/10 at 06:06 PM |
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The hard plastic bushes and the rally design bushes I have are identical in outer dimensions, so whichever you use will have the same potential
problems, ie rotating in 29mm id tube. I have both types in the garage and several bits of tube around these sorts of dimensions 29mm ish, I can have
a play and see if any conclusions can be drawn
Cheers
David
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Strontium Dog
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| posted on 9/11/10 at 06:21 PM |
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quote:
Originally posted by Minicooper
The hard plastic bushes and the rally design bushes I have are identical in outer dimensions, so whichever you use will have the same potential
problems, ie rotating in 29mm id tube. I have both types in the garage and several bits of tube around these sorts of dimensions 29mm ish, I can have
a play and see if any conclusions can be drawn
Cheers
David
Nice one David, that would be great. If they turn in the tube then I am stuffed!
Where does everyone else get there bush tubing from then and what wall thickness do you all use? I wanted to use the 3mm wall as I know that two of
the sets at least are going to get a great deal of hard use. Ie, pot hole ridden lanes!
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Minicooper
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| posted on 9/11/10 at 06:55 PM |
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Right, I have 35mm od and 29mm id cds tube with the burrs removed, the exact dimensions I can't be 100% sure as my cheap digital micrometer is
playing up but it's very close to the 29id your after, the rally design bush is a moderate push fit into the tube with thumb pressure.
It's a firm fit but it's not tight, when the crush tube is added the assembly tightens up a bit more. With the 35mm tube gripped in the
vice, I can just turn the poly bush by hand but it's a significant effort
I think if I was in your position I would buy say an axle set 8 off and try them with your tube, if it didn't work for you you could sell on an
axle sets worth, up to you
Cheers
David
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procomp
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| posted on 9/11/10 at 07:51 PM |
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Hi
That sounds about right for the rally design items in the 29mm id housings. But a slightly loose fit compared to the superflex items when in the
correct fit housings. So how about using the rally design items and having new pivot tubes made up which are the correct length and 10 tho / 0.25mm
bigger in id. That might end up as the cheapest option with decent results.
I see mention of Axle a few times are we talking about the fitment of a live axle in the rear. ?
Cheers Matt
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Strontium Dog
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| posted on 9/11/10 at 08:56 PM |
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Thanks for the effort there David! I wonder if I powder coat the inside of the tubre how much that will reduce the clearance and tighten the
fit?!
Matt, these are for wishbones and not a live axle. The chassis are all IRS. What tube would you use as I am struggling to find something with a
28.5-28.8mm internal diameter. I may just be looking in all the wrong places of course!
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procomp
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| posted on 9/11/10 at 09:15 PM |
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Hi
The 35mm OD stuff is about all you will find in that size. It's the std size tubing that the plastic bushes most use was designed for. But them
bushes where never intended to be used as Suspension bushing they are just general bushes. we used to use them on the dragsters and hotrods as engine
mounts where we had quick release pip pins to pull the engine out very quickly.
I use superflex items and machine the outer housings to be a very precise fit depending on the application they are being used for in the
suspension.
Cheers Matt
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Minicooper
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| posted on 9/11/10 at 09:31 PM |
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Just for clarity the tube I was using was not degreased in any way and no paint/powdercoating ie bare metal, I thought overall it ended up quite tight
and with powdercoating would nip it a touch more.
Something you have to try for yourself see if it's right for you
Cheers
David
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procomp
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| posted on 9/11/10 at 10:48 PM |
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Hi
Just been speaking to a customer who has used those bushes as replacement for the plastic items. Apparently if you only lubricate the inner pivot tube
to bush and NOT the outer housing to bush surfaces they will work as intended. Although he had no dims of the actual tubing used for the outer housing
as they where fitted into existing wishbones from manufacturer. So i guess it could well work not to bad as those manufacturers who are using CDS will
be using the same size so maybe worth a try as said above always sell them on if no joy.
Cheers Matt
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Strontium Dog
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| posted on 10/11/10 at 09:24 AM |
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Thanks muchly for all the help there guys. I think I'll buy a set and see how I get on. I can make sure I get some powder coat down the tubes
and see how they feel. As long as the bush moves around the pivot/crush tube easily then I think it'll be OK, fingers crossed.
Again, many thanks everyone for the advice and experimentation!
Cheers Si.
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