uberf1end
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| posted on 20/5/03 at 09:28 PM |
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Suspension Setup (and noisy bushes)
Anyone know of any online guides to suspension setup?
I fancy doing a but if reading but cannot find anything particularly useful. I know of a few books but, sticking to the Locost philosophy, I would
rather not pay 
A cursory search has revealed a lot of sites on how to set up your radio controlled car!
Also, my car creaks and squeeks a bit with any suspension movement. I assume this is the bushes which I would like to replace (or just grease up  ,
depending on their condition).
I remember reading somewhere that, when fixing wishbones on, you need to only tighten them up when the weight of the car is going through the
suspension (IE not on jacks/stands).
a) why is this?
b) Is this also the case for the shocks themselves and for the trailing arms on my live-axle?
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stephen_gusterson
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| posted on 20/5/03 at 10:00 PM |
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look at rortys posts re bushes - use the posts search option.
looks like we have lost rorty ..... 
atb
steve
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bob
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| posted on 20/5/03 at 11:10 PM |
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http://www.locostcarclub.co.uk have a section in HELP under HANDLING that might help a bit
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craig1410
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| posted on 20/5/03 at 11:21 PM |
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Hi,
In case you can't find Rorty's posts or get caught up in some of the long debates on bushes...
Basically you only tighten Metalastic bushes with the car at normal ride height because:
A metalastic bush has(usually) an outer metal tube separated from an inner metal tube (or crush tube) by a rubber moulding. When you tighten the
mounting the crush tube is...well...crushed! That stops it moving and since the outer metal tube should be a very tight friction fit inside the bush
tube, the only thing that can move during suspension travel is the rubber which distorts. Now since your car spends most of it's life standing
still it makes the rubber bush last longer if the rubber is in the relaxed position. Just think, if you tightened the crush bolt when the suspension
was in full droop then at normal ride height it would be under torsion and at full bump the rubber may shear especially when it gets older.
By the way, if you do decide to buy a suspension book, check out ISBN 1-903706-73-4
It is a book by Des Hammill and is very very relevant to the 'seven' design. It's about £17 IIRC but worth it in my opinion.
I hope this helps,
Craig.
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kiwirex
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| posted on 21/5/03 at 01:28 AM |
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There's an article called
"Automobile Ride, Handling and suspension design" with implications for low mass vehicles at:
http://www.rqriley.com/suspensn.html
There are a few other docs on his site, value of which I'll leave you to decide:
http://www.rqriley.com/docs.html
Rorty has a bunch of stuff on his web-site:
(technical page)
http://home.iprimus.com.au/IP-PWP03/65/rorty/index/tech_page_3.htm
Although it's mainly aimed at "do it in the dirt" racers most of it still applies.
(Rorty posted a while back that he was going to have an op, not life threatening, but with a long recuperation time, so hopefully we'll see him
again... ) - a series of columns written as "Ed McCannick"
Or you could try firkling through eng-tips suspension forum. (this link might not work if you're not registered).
http://www.eng-tips.com/threadminder.cfm?SPID=800
Lots of the stuff about tuning an RC car suspension still works for grownup cars, e.g.:
http://home.mweb.co.za/ef/effecta1/rollcent.html
(Although what a roll centre is for is still a bit fuzzy).
Alan Staniforth's book "Race and Rally Car Sourcebook" has a pretty good chapter or two on the subject if you can afford paper (or
the library has it), although I found a few things confusing.
Good luck, let us know if you find anything else interesting.
- Greg H
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craig1410
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| posted on 21/5/03 at 08:42 AM |
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>> Alan Staniforth's book "Race and Rally Car Sourcebook"
Yes I'll second that book reference, I actually understand about roll centre's now thanks to this book. I forgot I even had this book
until I found it up in the attic the other week.
The bit about roll centres which I really found useful was where you can draw a line between the front RC and rear RC and this effectively becomes the
pivot through which the whole chassis rotates during pure cornering (ie. no accel or braking). This explained why some cars lift a back wheel (ie.
Mini) because the front RC and rear RC are at different heights.
My advice is still to buy a reputable book because it is cheaper than getting your design wrong and having to rework your chassis!
Cheers,
Craig.
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uberf1end
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| posted on 21/5/03 at 07:12 PM |
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Cheers guys, helpful as always.
I think I will be investing in a couple of books. A friend of mine has recommended 'How to Make Your Car Handle' by some chap called Puhn
so I reckon I may take a look at that and those you recommend.
Craig, I think I get what you are saying about bushes.
A normal bush - from the outside in, there is Rubber/PU, metal, rubber, metal. Is this right?
In 'Which Kit' this month and there were pics of a wishbone bush being put together (on an MK build) and it appeared he was simply pushing
a metal tube into a rubber outer (with a vice). There was no sign of two metal 'layers'. Does that sound right? Is it simply another
option to only have the two components to a bush?
Or am i missing something?
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craig1410
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| posted on 21/5/03 at 07:29 PM |
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Hi,
There are many different kinds of bush for many different purposes but the ones I'm referring to are the ones used as in the "book"
locost in all the usual places such as wishbones inner mounts, trailing arm ends and panhard rod ends.
They consist of a metal outer tube with a metal inner tube and these two tubes are bonded together by a rubber sandwich. There is no rubber on the
outside of the outer metal tube as you are suggesting.
I hope this is clearer than my last explanation. Doesn't anyone have a picture of a Metalastic bush? I don't because I don't use
them myself.
HTH,
Craig.
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uberf1end
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| posted on 21/5/03 at 07:42 PM |
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Cheers Craig.
I have just been reading all the old dicussions on bushes....there was a little friction there (if you'll pardon the pun) but Rorty's (and
others) posts were most helpful and I think I get it now.
I bought my car second hand (built) and am trying to understand before I take it to bits but I really should just whip 'em off and have a
look.
I am going around the car, doing bits and bobs and generally learning about it. Problem is, having it off the road while I do my research is a
shame....the damn thing is so much fun I just want to drive it 
As many people have said, you really do never finish a car like this (even when it was 'finished' when you bought it).
There is nothing really wrong with it, there's just so much you could change.
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craig1410
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| posted on 21/5/03 at 07:45 PM |
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Fix it in the winter would be my advice and enjoy it in the summer. Hopefully I'll be able to do just that next year...
Cheers,
Craig.
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John
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| posted on 23/5/03 at 10:09 PM |
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Good Suspension Book
I would agree with Craig's endorsment. I have a copy of the Des Hammill book and find it excellent. Goes to town on all types of suspension
and set up, very relevant for Locosters.
ATB.
John.
Working on a CVH 1.8 engined Locost. Hoping to use as much as possible of Sierra donor. £210 left.
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