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Author: Subject: stability, c of g and suspension
Delinquent

posted on 9/9/08 at 06:10 PM Reply With Quote
stability, c of g and suspension

Anyone have any good sources for info on any of the above in trikes? Obviously the lower the C of G the more stable it's going to be in corners, but more interested in effects in a straight line on a vehicle with a below ideal wheelbase to track ratio!

Currently c of g is looking to be spot on axle height (which I don't think is too bad really) just trying to work out if it's worth making sacrifices to lower it further.

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Stott

posted on 9/9/08 at 06:43 PM Reply With Quote
My best mate builds trikes for a living for:

http://www.netupandgo.com/hankschopshop/

(check the V8 in gallery, the owner scrapped a good XK8 to make that!!!)

My experience of them is that they all handle a bit funny, but are often with unfavourable w/b to track ratios so I wouldn't think it would warrant further lowering

Beware of the car drivers who think your a bike head on then brick it and swerve at the last minute upon noticing your rear wheels hanging out, unnerving to say the least!......................

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Delinquent

posted on 9/9/08 at 07:59 PM Reply With Quote
Cheers stott,

I should have been a little more "giving" on the info side though, I'm looking at reverse trikes rather than normal so it'll be a wide front end!

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smart51

posted on 9/9/08 at 08:29 PM Reply With Quote
Cornering stability of 3 wheelers is basically governed by C of G height, track and wheelbase. Imagine a triangle drawn on the floor round your three wheels. Imagine a plumb line hanging from your centre of gravity. Acceleration will pull your plumb line backwards, braking will pull it forwards and cornering will pull it sidewards. Braking whilst cornering etc will pull it diagonally. If the point where the plumb line touches the floor is inside the triangle, your car will stay upright. If the point moves out of the triangle, it will tip over. Soft suspension makes the car less stable. The same rule applies to 4 wheel cars too by the way.

If your C of G is near to the 2 wheeled axle, you will have more stability. If it is low down, you will have more stability. If the triangle is wider, or to a lesser extent longer, you will have more stability.

A simple worked example. Your centre of gravity is 1 metre high. It is exactly half way along the wheel base of 2m long and exactly on the centre line side to side. Your track is 2 metres wide. The width from the centre line under the C of G to the "triangle" is therefore 1 metre, the same as the height of your centre of gravity. In a 1g steady state corner, you will be just on the edge of tipping over.

in the same example, let us assume you have 2 wheels at the front. If you brake, the imaginary plumb line moves forwards towards the wider end of the triangle. You can therefore corner a little harder before tipping over. However if you accelerate, the plumb line moves towards the narrow end of the triangle and you tip over.

lowering your centre of gravity will help, but moving it towards your 2 wheeled axle may help more.

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Delinquent

posted on 9/9/08 at 08:41 PM Reply With Quote
smart51 that's a great bit of info, many thanks - I'll have to move a few things around in that case as the cofg is a bit far back at the moment.
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dodgedartgt

posted on 11/9/08 at 12:20 AM Reply With Quote
Here is a good tutorial which also includes info on leaning three-wheelers. Check out the website while you're there. http://www.rqriley.com/3-wheel.htm

Mike Bynum

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Delinquent

posted on 11/9/08 at 08:47 PM Reply With Quote
Cheers, the more info the better
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