Julian B
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 posted on 26/3/07 at 07:41 PM |
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The Finer Points
Hi all
I have pretty much made up my mind and decided to scratch build my next car. I think my welding and fabrication are upto it and i'm fairly happy
that i understand the basics of chassis design (basics) but i think i may have fallen at the first hurdle.
How do you decide on the following
Wheelbase
Ride Height ( manhole safe )
Front and rear Track width
thanks agin
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nitram38
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| posted on 26/3/07 at 07:47 PM |
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quote:
Originally posted by Julian B
Hi all
I have pretty much made up my mind and decided to scratch build my next car. I think my welding and fabrication are upto it and i'm fairly happy
that i understand the basics of chassis design (basics) but i think i may have fallen at the first hurdle.
How do you decide on the following
Wheelbase
Ride Height ( manhole safe )
Front and rear Track width
thanks agin
For wheelbase and trackwidth, compare this to a known car and work it out from there. The driver's ideal position in the car is where his
head/body is centered between the front and rear wheels.
For ride height I wouldn't go below 120mm unless you are using air ride suspension to adjust your height( my next project!)
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JoelP
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| posted on 26/3/07 at 09:28 PM |
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for the sake of an argument you may as well have the same track front and rear unless donor items force differently. 'they' say that 1.6
is the ideal ratio for wheelbase to trackwidth, no idea as i didnt work it out myself. Ride height depends on your local conditions. I feel round
leeds i could get away with 100mm at the front, 125 at the back (bit of rake is good).
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Chippy
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| posted on 26/3/07 at 10:11 PM |
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Don't know if its still in print, but if you can get hold of a copy of:- "Designing and Building Special Cars" by Andre Jute, it
will answer all of your questions. Deals with all aspects of design very fully. HTH Ray
Local library may be able to get you a copy.
[Edited on 26-3-07 by Chippy]
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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Confused but excited.
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| posted on 26/3/07 at 10:42 PM |
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You can still pick copies up for between £10 and £25 plus postage form various sellers. Mainly in the States.
Tell them about the bent treacle edges!
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Doug68
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| posted on 27/3/07 at 05:08 AM |
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The wheel base - track issue is not that big a deal.
Just choose an existing vehicle that you think is close and use that to start.
In the end it will end up as wide as you think is sensible and no longer than you need to fit everything in and try and get the C of G where you want
it.
Difference in front to rear track is used to typically to try and promote under steer in vehicles that want to over steer which is most middies. The
difference typically is not that much I think it is ~20mm for the Ford GT for example. So its within the range of adjustment that can be achieved
with different offset rear wheels if required when it comes to testing.
Ground clearance at ~125 appears to be the way to go but with the car you already have you have an ideal way to test this by gluing polystyrene or
some such to the bottom of it and see if it gets knocked off.
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02GF74
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| posted on 27/3/07 at 09:33 AM |
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quote:
Originally posted by Julian B
Ride Height ( manhole safe )
It is speed bumps that you should be more concerned about.
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gttman
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| posted on 27/3/07 at 02:48 PM |
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Wheelbase and track will depend on what you want from the car....
Odviously both are dependant on the size car you are planning however the longer the wheelbase in relation to the track the more stable the car will
be at speed..... however the small it is in relation to the track the more pointy it will be in the twisties (as well as more twitchy example is a
lotus elise).
There are however a complete ream of other things that are also going to effect the dynamics so you really want to decide what kind of car you are
going for before you settle on anything as some things will be a compramise.
Ride height will be practicality driven and also dependant on you body shape.... a long nose = more ride height for example.
My Ultima had 90-100mm under the front splitter... my car is going to be 110-120mm.
Andygtt
Please redefine your limits
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thomas4age
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| posted on 27/3/07 at 06:20 PM |
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ride hight in concern to speedbumps is very much dependant on wheelbase.
a long luego needs to be much higher than my litle striker,
I have 90mm in the front (sump sticking out 1.5cm below that) and 105mm in the rear, only once had a problem on bottoming out but the steel sumpguard
caught the damage perfect, minor scratches)
I can go over pretty high speed bumps with 55km an hour without touching
grtz Thomas
If Lucas made guns, Wars wouldn't start either.
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Julian B
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| posted on 28/3/07 at 05:05 PM |
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Thanks for all the info
Just one other question. If i'm using donated uprights does the anle of the track arms matter?
I remember at school we built a gocart in metalwork ( Showing my age now ) and the track arms were pointing to the centre of the rear axle. If this
is true then is the wheelbase set by the uprights you use?
Cheers again
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nitram38
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| posted on 28/3/07 at 05:12 PM |
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My next project will be 75mm
I am waiting for it.....
At times it will be up to 150mm or even 0mm !
I am fitting air shocks with a compressor plus titanuim blocks under the chassis incase I spring a leak!!!
 
Description
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Doug68
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| posted on 29/3/07 at 12:35 AM |
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Julian B
I believe what you are referring to there is Ackermann steering basically no you
don't need to worry about that for any thing other than slow speed vehicles.
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