smart51
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| posted on 27/5/10 at 11:14 AM |
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Donor brake master without the servo
I'm drawing up plans for a super light weight 3 wheeled single seater. 200 - 250kg target weight. I've been told that a cinquecento
steering rack is the best for the job and a process of thought has led me to think, why not use the fiat's front upright and ARB and brakes and
wheels and eventually, the master cylinder and pedal box. All cheap, chearful and bolt right in from the donor.
The fiat master cylinder comes with a servo built in, which I won't need for such a light weight vehicle. Can it be dismantled to remove the
servo bit and use the remainder?
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jossey
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| posted on 27/5/10 at 11:38 AM |
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yes you can as far as i know but you will need to build a new push rod.
why not use it anyway. it will be well fun with the servo. :O)
good luck.
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iank
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| posted on 27/5/10 at 12:41 PM |
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Weird coincidence, I've been working on a 3 wheel (tadpole/reverse) single seater trike along the lines of the Hudson Freespirit over the last
couple of nights. Though I'm still at the very high level concept stage.
Are you going FWD or RWD? BEC or CEC?
Presumably BEC RWD from the target weight.
Personally I'd get a BMC4020 master cylinder, from brakesint it's only about £17+VAT and designed for un-servoed operation. (From a
Fiat124)
[Edited on 27/5/10 by iank]
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Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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prawnabie
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| posted on 27/5/10 at 01:10 PM |
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Will the pedal feel ok as the m/c I assume would be a larger bore size than non servo.
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smart51
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| posted on 27/5/10 at 01:11 PM |
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Iank, thanks for the tip on the MC. Do you have any sketches of your 3 wheeler ideas? Mine will be scooter engined, so rear drive. I'm told
front engined FWD is the best layout but I already have the scooter drive train.
To get that weight, there'll be virtually no bodywork. I'm thinking of a space frame of 12mm tubes in a geodesic arrangement with
something like tent fabric over it to keep some of the weather out.
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iank
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| posted on 27/5/10 at 01:43 PM |
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Only sketch I have is a very basic 1st cut drawing for packaging to get an idea of size/layout. I want it to be low and short but may have gone too
far with the first cut. Triangulation isn't even started yet before anyone mentions the distinct lack of triangles 
 
Current thinking is FWD but I need a small, low, lightweight engine gearbox with a cable change gearbox tunable up to 100-120bhp ish which should be
plenty at my 330kg target weight.
Possibly BEC if I can find something that connects easily to a diff (Quaif make the idea box of tricks but as usual they want a kidney or two for it).
There's not a lot of room but I know an R1 with chain driven diff can be squeezed into a mini front subframe so maybe that's the right
route but chain length will be very short which isn't ideal.
I figured you'd be avoiding bodywork on your project but your fabric/frame idea is fascinating (from what I remember there was something East
German that used a similar fabric idea).
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Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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iank
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| posted on 27/5/10 at 01:48 PM |
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East German car was the Velorex and was actually Czechoslovakian 
http://www.absoluteastronomy.com/topics/Velorex
[Edited on 27/5/10 by iank]
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Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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smart51
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| posted on 27/5/10 at 02:33 PM |
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Interesting idea you have there. You'll need a very low engine if you want to recline that far back.
I've seen pictures of the velorex before. I'm thinking more like
Thi
s with tube lengths of about 200mm. The gap might be small enough to keep out the MSVA tester's sphere, which will be a bonus.
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alistairolsen
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| posted on 27/5/10 at 02:34 PM |
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Why is FWD considered the choice for weight? Surely a 600cc bike engine and rear suspension would be the lightest most integrated solution? The only
issue I can see with my idea is your feet become the crumple zone essentially.
My Build Thread
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iank
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| posted on 27/5/10 at 02:48 PM |
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quote:
Originally posted by alistairolsen
Why is FWD considered the choice for weight? Surely a 600cc bike engine and rear suspension would be the lightest most integrated solution? The only
issue I can see with my idea is your feet become the crumple zone essentially.
It's not about weight it's about stability. To achieve stable handling in a trike you need the weight as close to the front as possible,
so you either need the driver up front with his feet in front of the wheels or put the engine up there. Scope for a tunnel in a single seater is
limited to say the least so FWD is a good compromise.
RWD reverse trikes also have a handling issue when accelerating hard out of a corner as they tend to lift a front wheel and tip over.
The maths is all here
http://www.clevislauzon.qc.ca/Professeurs/Mecanique/ethierp/3-wheels/index.htm
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Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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coozer
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| posted on 27/5/10 at 03:11 PM |
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Ian, for FWD it is possible to use a FJR1400. The gearbox output shaft runs across the engine and from what I know (very little ) can be adapted to
provide an output. No diff though....
I seem to remember a thread somewhere with one being used BEC style for AWD.
1972 V8 Jago
1980 Z750
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alistairolsen
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| posted on 27/5/10 at 03:13 PM |
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interesting reading! 3 wheelers aren't something Ive ever looked at.
Its probably far too heavy but the layout of a merc a class would lend itself to this!
My Build Thread
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iank
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| posted on 27/5/10 at 03:26 PM |
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quote:
Originally posted by coozer
Ian, for FWD it is possible to use a FJR1400. The gearbox output shaft runs across the engine and from what I know (very little) can be adapted to
provide an output. No diff though....
I seem to remember a thread somewhere with one being used BEC style for AWD.
Thanks for that, I'll look for info, maybe a quadbike diff can be hooked up. Still well in the 'maybe the next project'
category.
This is the perfect unit, but a significant chunk of change, well out of my toy budget range.
http://www.quaife.co.uk/catalogue/products/qba11r-0
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Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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