GolfGTIforum.co.uk
General => Shows, events, track days, motorsport => Topic started by: danny_p on 14 October 2012, 22:56
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just looking at the price and possible lack of avaliblity for polybushes for the arse end of my syncro.
so thinking about makeing them, has anyone used nylon ? iirc its sort of halfway house between poly and bearings
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http://www.vwheritage.com/vw_spares_Bush-Rear-beam-mount-Powerflex-Golf-Rallye-G60-Syncro-WC50185260_act_shop.product_pID_16409659_lang_EN_country_GB.htm
Any good? :huh:
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That's what I have on mine, but I think Danny's talking about making himself something stiffer, Dave.
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Not familiar with the layout but going to assume there are 2 bush locations/pivots... As long as the two pivot points are in line on the arm, nylon (6 or 66) or delrin/acetal will be fine though dont run it direct on the bolts as the nylon/delrin will wear the bolt out (not that I would think you would anyway), amazingly resiliant stuff nylon.... If the pivots are not in line, dont bother, it wont work and Polybushes wont either as the arm will bind up/the bushes will break up. Expect spherical levels of noise and harshness...... Also make sure not to get glass filled nylon as it will chew through anything it runs on! Its not that common but you never do know lol.
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Maybe look up the layout first, then you could make a relevant post?
(http://www.northloop.co.uk/forum/images/smilies/thumb.gif)
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:rolleyes:
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My sentiments entirely.
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Nylon absorbs water.
It will shrink and grow with the weather causing it to bind if you require a sliding/moving fit.
You will need to have so much clearance that it will be a sloppy fit when "dry"
If you machine it across the grain it can crack, if it dries out it can crack, if you do both it will crack.
Other plastics can be used but you always get a trade off against other failure modes, elastomers are used in the suspension of cars for this reason along with natural rubber
Polyurethane can be bought in different hardnesses shapes and lengths and fashioned on a lathe or Mill.
I take by wanting to make Nylon bushes you have access to this sort of equipment :smiley:
2 secs on google found me this, although I have a supplier in West Sussex
http://www.bonaprene.co.uk/shop/13_Polyurethane_Tube__Rod
I suggest maybe looking at the quoted harness of Brands like Power flex and selecting where you want to go from there.
The softer you go the harder it is to machine, practice on a little bit first :wink:
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i was thinking of making inserts or tubes to go trough the bush out of bright bar or possobly even stainless depending what i can get my mits on at time of construction.
- VW bush
thats some usefull infomation on the downsides of nylon, i've heard of it been used but not haveing any direct experiance of useing it for such appications thought it would be good to ask. by the sounds of it poly is quite a sutable material for some of the bushes.
was considering sperical bearings but i can't be arsed with the ballache they cause lot of work doing the conversion right and unless it's kept warm dry and never played with in the wet and allways cleaned they seem to have a sub optimal life :( and stuff cracks so allways inspecting for fatigue :(
as for the lathe and mill i have a crappy lathe of my own thats good enough to do bushes on got accses to a better one and a mill, but it's more to the point i cant bring myself to spend £50 on a pair of bushes , chould put that towards a fat bastard size seat :)
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Don't get me wrong Nylon is great stuff, id just go for PU as its proven and has some give.
Anything solid as a bearing/bush will give you a rear beam with no give or twist, which will require a cushion in your seat but may give you something desirable on the track or piles :grin:
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Ahem.
Syncro.
No beam.
Trailing arms, on subframe.
Big expense is the bushes on the subframe.
Like this:
(http://img.photobucket.com/albums/v627/diamondhell/Post-Crash/20121018_230514.jpg)
Big fat fookers.
I seem to recall that freezing poly material makes it easier to cut down to fit, doesn't it?
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Deffo poly in that application with that range of movement.
PU generally has a glass transition lower than your freezer will go so you wont crack it :grin:
It will get stiffer the colder it goes, but to be honest your best not putting too much heat into it while cutting as freezing really only works on small diameters and harder pu.
Freezing it to doof it in works a treat though.
There is a knack to machining soft polys, you need to get a cut on (don't be shy), and need to support to stop the deflection if its hanging out the chuck or vice
Use a tool with a fine honed cutting edge (no rough grinding), 2 ish mm tip radius with all the faces cut back to clear the poly rod and a narrow tip angle.
High surface speed and a light feed is a general starting point but hardness of the Poly will dictate this.
The poly should come away in a clean long ribbon and try to drag your face into the chuck :grin:
Milling is best as the material comes away in smaller chips/strips but if you dont have turntables etc then anything round becomes a ball ache...
If it comes off all scabby and stringy leaving a badgers arse behind you are doing something wrong :grin:
If you could lay your hands on a set of powerflex bushes to measure them up, you would be in a good position to try harder PU materials and cost it up properly.
Let us know how you go :smiley:
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Deffo poly in that application with that range of movement.
Those are just the sub-frame mounting bushes. They are pretty much static and have nothing moving in that application - those are different bushes, which are much like the small bush on the front control arms.
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not afraid of getting a cut on..... if anything i usally get to ambitious ( mainly due to getting bored stood there watching it )
for the subframe to body bushes i've thought about solid lumps of ali once or twice but something with some give will be better i think, lump of the hardest poly i can find is the order of the day i think, due to the nylon / water issues mentioned.
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Deffo poly in that application with that range of movement.
Those are just the sub-frame mounting bushes. They are pretty much static and have nothing moving in that application - those are different bushes, which are much like the small bush on the front control arms.
You will have to forgive my lack Syncro running gear knowledge, I am a virgin in this area :grin:
I would still stand by a "rubber" bush if that's what the car was designed with.
Solid will pass a lot of vibration and stress into the surrounding components and fixings and maybe cause a failure under load
Obviously you can get round the Increases in stress, In pretty much the same way you go about using bearings but this blows dannys seat fund out the back of his pants :grin: