MonkeyHunter
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| posted on 8/9/04 at 02:17 PM |
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DIY suspension bushes.
Hi, I am ordering some casting polyurethane, to stiffen up my suspension mounts.
I will have quite a bit left over, so my question is, is there any reason why I cant make my own top hat suspension bushes, but with the
"rims" of the top hats as separate pieces?
I figure it will be much simpler to make them in this way, as I can pour two bars of poly, and then just cut to the appropriate length, as opposed to
making lots of top hat moulds.
Also, anyone know of anything that is good at dissolving / removing polyurethane? As I want to remove the stuff in my engine mounts at the moment.
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liam.mccaffrey
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| posted on 8/9/04 at 02:32 PM |
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i am going to make my own suspension bushes if i can get some poly,
i was going to turn them down from bar so if there is a better way i would be very interested
any one know where i can get poly rod from?
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timf
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| posted on 8/9/04 at 02:38 PM |
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quote:
Originally posted by liam.mccaffrey
i am going to make my own suspension bushes if i can get some poly,
i was going to turn them down from bar so if there is a better way i would be very interested
any one know where i can get poly rod from?
http://www.aiinternational.co.uk/
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andylancaster3000
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| posted on 8/9/04 at 03:27 PM |
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Have a look at the RS components website
www.rswww.com
or get hold of their catalogues. They have a large selection of plastics probably suitable
Andy
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Hellfire
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| posted on 8/9/04 at 04:17 PM |
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quote:
Originally posted by andylancaster3000
Have a look at the RS components website
www.rswww.com
or get hold of their catalogues. They have a large selection of plastics probably suitable
Andy
R U on commission? 
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MonkeyHunter
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| posted on 8/9/04 at 07:07 PM |
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*Cough* Anyway..... Anyone? Please! 
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Peteff
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| posted on 8/9/04 at 07:18 PM |
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A blowlamp should remove your old ones. You could just make the bushes in poly and put washers either side of the centre tube to stop sideways
movement.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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MonkeyHunter
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| posted on 8/9/04 at 08:51 PM |
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quote:
Originally posted by Peteff
You could just make the bushes in poly and put washers either side of the centre tube to stop sideways movement.
I was under the impression that the ends needed to have some elasticity, so that the bushes can absorb some lateral forces from the wishbones? Though
i suppose you dont get that with Rose-Jointed set ups.
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Hugh Jarce
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| posted on 9/9/04 at 06:13 AM |
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If you could be absolutely certain the wishbones would only move in one plane then you could get away with steel washers at each end. As the wishbones
will flex all over the place, washers would impede the movement and start chewing up the wishbones or brackets.
Making top hat style bushes is quite easy if not a bit time consuming. You'll need to make a two-part steel mould on the lathe and then just
pour them one at a time.
Peteff is correct about the old engine mounts. Just burn them out with a blow lamp or the gas axe. You will then have to build a tricky little setup
to support both steel elements of the engine mount while you pour the urethane around them.
The pay isn't very good , but the work's hard.
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MonkeyHunter
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| posted on 9/9/04 at 11:02 AM |
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quote:
Originally posted by Hugh Jarce
If you could be absolutely certain the wishbones would only move in one plane then you could get away with steel washers at each end. As the wishbones
will flex all over the place, washers would impede the movement and start chewing up the wishbones or brackets.
Making top hat style bushes is quite easy if not a bit time consuming. You'll need to make a two-part steel mould on the lathe and then just
pour them one at a time.
Peteff is correct about the old engine mounts. Just burn them out with a blow lamp or the gas axe. You will then have to build a tricky little setup
to support both steel elements of the engine mount while you pour the urethane around them.
The thing with making a single mold is i would have to mix up the polyurethane a bit at a time, and it would only be a tiny ammount, so its not very
practical.
I tried burning the Rubber out of one of the mounts, with a mini propane/oxy tourch, and it doesnt want to melt, and it burns very slowly and keeps
putting itself out  I currently have it imersed in paint stripper, to see if that will do the job.
To support all the bits of the mounts while i pour the polyurethane in, I was just going to use plasticine.
Come to think of it, i wonder if i could use a "Metal Top Hat" to punch out moulds in a big block of plasticine so i could pour all my
bushes at once??...
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chrisf
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| posted on 10/9/04 at 01:09 PM |
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3 part mould
I actually considered this myself. My reason was so I could mix graphite in with the poly. As for the mould making, here was my idea...
1.) Pin the two blocks of 6061 together and bore the holes in. It is actually two holes because of the shoulder on the poly bush. My block would have
made 8 pcs.
2.) Pin a third block to top off the bush holes.
3.) Drill small air hole through the top, one for each bush.
4.) Flip the mould over and drill a very small hole in the bottom of the mould, one for each bush.
5.) Use a syringe to inject the poly through the small hole on the bottom. When the polly begins to squirt ot the top air hole, place a piece of tape
over it.
My mould was a bit more detailed because I placed a male pin where the crush tube would go. In the end, I figured this was more trouble that it was
worth. I took my already-purchased Delrin rod to the CNC shop and they turned it for me based on a SolidWorks file.
--Chris
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givemethebighammer
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| posted on 11/9/04 at 04:05 PM |
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quote:
Originally posted by Peteff
A blowlamp should remove your old ones. You could just make the bushes in poly and put washers either side of the centre tube to stop sideways
movement.
Is there not something nasty that gets released when you set fire to automotive rubber components ? Seem to remember reading about hydrofluoric acid
and people having to have limbs amputated ?
yes could be hazardous see here:
http://members.ozemail.com.au/~sparrow/viton.htm
[Edited on 11/9/04 by givemethebighammer]
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Peteff
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| posted on 11/9/04 at 05:58 PM |
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Internal components use that.
Stuff is used inside engines and is bad news. It eats you alive.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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givemethebighammer
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| posted on 11/9/04 at 06:32 PM |
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internal components only ? so it's definately not used in suspension bushes, engine mounts etc, I've seen them turn to a black sticky mess
as described after they have been exposed to excess heat.
just did a search seem to be that mainly sealing components (oil seals, gaskets etc) are made of this evil Viton stuff. Makes you think though
[Edited on 11/9/04 by givemethebighammer]
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silex
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| posted on 14/9/04 at 11:44 AM |
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Try the following for polymer bushes / bearings
www.igus.co.uk
Murphy's 2 laws
1. If it can go wrong it will
2. In case of emergency - refer to rule 1.
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andkilde
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| posted on 14/9/04 at 01:08 PM |
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Hey guys
The folks I work for cast poly components -- I've been on them to make some tophats for me, it's a no go in small quantities, cost
prohibitive for runs under 1000 pieces -- anyroad we make three styles of moulds for poly.
1) CNC cut open top moulds. you could probably do this nicely on a drill press, though a bridgeport would be better. Basically drill and countersink
concentric holes in a thick sheet of ally, drill the centre as a through hole (later filled with a metal dowel) with the tophat at very top. These
moulds are gravity poured and the excess trowelled off even with the top edge of the mould.
2) CNC cut closed moulds (necessary if you need tight controls on the part height). similar mould to above, leaving the centre dowels longer. A top
plate with the dowel holes cut fits over top after the urethane is poured into the bottom half of the mould, excess poly squirts out a small relief
drilled beside the dowel hole.
3) Hard poured urethane mould. Exact copies of the part, called hobs, are cut from ally set upside down on a flat plate, dammed up around the edges
with more ally and hard urethane is poured into a thick slab around the hobs. Once cured you have an open topped mould.
All require use of a release agent, silicone works best but gives auto plants the willies (smallest bit of silicone will fisheye paint) so we
don't use it.
Also, you need to design your part with a slight draft angle (ie. slightly tapered going into the mould). Only a very tiny amount is required -- helps
get the parts out of the mould. Parts are generally popped out after initial cure using compressed air blown around the edge of the parts & mould
-- then placed back in the oven for final cure. Urethane shrinks a bit as it cures, the percentage should be given by the urethane supplier. Your
mould will have to be adjusted in size to compensate.
On this side of the ocean Acklands Grainger (www.grainger.com) sell inexpensive kits of pourable poly in 60A and 90A. Not sure where you'd find
it in the UK but poke around at your local industrial supply and bearing shops -- they won't stock it but should be able to order it in for
you.
Hmmn, all this fussing makes me think it might be far easier (in small quantities) to have someone carve them out of delrin on a lathe...
Cheers, Ted
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