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May 22, 2013, 4:30pm

UKGSA.org Forum :: Disciplines :: Soapbox :: Suspension. Is it necessary?

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Topic: Suspension. Is it necessary? (Read 2,131 times)

peasnbarley
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Re: Suspension. Is it necessary?
« Reply #20 on Sept 29, 2010, 12:46am »

Andy I don't believe anyone would suggest you were ever a JESSY.

If you don't think things are right with your cart, sort it out.

"Take it on board, deal with it and move on."

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andy
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Re: Suspension. Is it necessary?
« Reply #21 on Sept 29, 2010, 5:50pm »

Thanks for all your comments.

There is some major food for thought there.

We are at Cadwell in November and as the track is very smooth I don`t think I will be making any alterations to the carts set up just yet.
Over the winter I plan to make some changes, tho as Rich so rightly says, only one at a time !! I now have some ideas and will try and just build a bit more "flex" into the cart, rather than any major tweeks.

I realised there was a problem....I have taken everyones comments on board.....The situation is now delt with.......I`m already moved on !!!

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Organgrinder
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Re: Suspension. Is it necessary?
« Reply #22 on Oct 8, 2010, 8:08am »

We have been running the same chassis and running gear with different body styles for the last seven seasons. We have no suspension, other than that provided by the tyres. The chassis is stiff and we have very simple steering - all vertical/horizontal like Andy's.

What has been interesting to us has been the effect on handling of weight distribution. Our basis cart is very light, but for one season we ran an all enveloping body with a long tail for maximum straight line speed, which took it up to about 100kg. It was very quick, but handled like a greased pig. At high speed on a road with any sort of crown the cart was darting from side to side and took massive concentration to stop it flying into the scenery. When the body was removed the handling reverted to the benign characteristics that allowed Dick to be very fast in the wet at Catterline and Moira to go well in the rain elsewhere - oversteer yes, but nicely controllable. The weight of the enclosed body altered the weight distribution such that the back wheels were always fully loaded sufficiently to keep them on the road, but the front wheels seem to have been taking it in turns to do any work, resulting in very interesting "bump-steer" type effects.

The conclusion we have drawn from this experience is that for the thing to handle and steer well it is vital that the front wheels both remain in contact with the road at all times, but that complex steering geometry is not actually that important.

If I was to build a new cart (which I do not plan to do as I'm now running a sidecar outfit) I would seriously question whether the effort, cost and precision needed to to get a front suspension set up and working properly is worthwhile. After all, most carts have a rearward weight bias anyway, forced on the designer by the size of the driver, his C of G and the relatively short overall length of a cart. I would build in inclined kingpins for zero scrub radius and some caster angle (11 degrees seems to be the accepted wisdom), but wouldn't bother with suspension, as this just brings more complexity, especially if you want to eliminate bump steer. What I would do however is fit suspension to the back end.

Fitting suspension to the axle that is carrying the greater load makes sense from the point of view of reducing losses due to the need to accelerate the mass of the whole vehicle over a bump in the road and will assist in keeping all four tyres on the road. The suspension would have to be fairly stiff to resist roll, which would spoil the handling, but if the C of G is low enough this shouldn't be a major problem. The simplest and cheapest was to do back suspension is probably a beam axle located by two trailing links and either a Panhard rod or a Watts linkage, with vertical, or near vertical MTB type suspension units.

Food for thought and further debate to keep us on our toes during the closed season.

Best wishes to All. See you at Cadwell

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carnuts
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Re: Suspension. Is it necessary?
« Reply #23 on Jan 3, 2011, 5:03pm »

I have built several karts and found the three wheel phenomenon and the cart leaping across the road. I am building a new cart this year and will fit suspension, as this will avoid the bent axles suffered at Leeds & Goodwood. Suspension will be by Honda 50 shocks and springs with drag links, although I will experiment with bungy cord. You may laugh at this but several aircraft use this system and if it's good enough for them etc. one bonus is that it is really easy to alter the rates.
I have built several kit cars from scratch, and it does not take a genius to set up front suspension, so don't be put off. ( the side effect is a nice ride and the ability to control the vehicle without your eyeballs vibrating out of focus.

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gunnerhoots
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Re: Suspension. Is it necessary?
« Reply #24 on Jan 8, 2011, 1:26pm »

Why not build one like this. No suspension needed for comfort
actually dont even need a hill!

http://s223.photobucket.com/albums/dd11/....nt=MOV00014.flv

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kingkay
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Re: Suspension. Is it necessary?
« Reply #25 on Jan 8, 2011, 8:22pm »

Just thought I'd be the first to suggest Andy is infact a jessy.

I was thinking of the beam axle with the MTB springs on for the fron and rear. same set up as a range rover. Front leading rear trailing. Not perhaps the most sporty of cars but smoother than a leaf spring motor. This way the bits of axle outide the body could be just bar and so streamlined. no double wishbone stuff. I know its not fully independent but better than nothing.

If the steering rack was mounted onto the front beam axle then the steering geometry wouldnt change when the bumps hit - just a slight wobble in the steering wheel - so no change there then!

any thoughts?

TDR

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andy
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Re: Suspension. Is it necessary?
« Reply #26 on Jan 8, 2011, 11:39pm »

get some coffee toby

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caisse433
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Re: Suspension. Is it necessary?
« Reply #27 on Jan 15, 2012, 11:49am »

two video with my suspension
http://www.youtube.com/watch?v=R9dbFJA4hQ8
http://www.youtube.com/watch?v=IwQr1CrTY....26&feature=plcp

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hello,I'm belgium driver since 32 years,winner of the 2011 belgian championship

paulw7
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Re: Suspension. Is it necessary?
« Reply #28 on Jan 15, 2012, 6:34pm »

My 'old' trolley had a pivoting rear axle to keep all four wheels on the road, worked fine until a big bump in the road launched us into the path of and oncoming car whilst testing.
Current setup is double wishbones front and rear, testing has gone well and we've hit the same road without being launched. Just waiting for a race now to prove it.
KPI 15 deg, lead 40mm. 20inch bike wheels.

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caisse433
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Re: Suspension. Is it necessary?
« Reply #29 on Jun 10, 2012, 12:26pm »

a new video on my suspension,
http://www.youtube.com/watch?v=aEbMYeos3-o

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hello,I'm belgium driver since 32 years,winner of the 2011 belgian championship

caisse433
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Re: Suspension. Is it necessary?
« Reply #30 on May 20, 2013, 10:14am »

a video fron Bruno Menzi, swiss driver, made at On, europeen cup 2013
https://www.youtube.com/watch?feature=player_embedded&v=sfIRHUqDZYo
the track:
http://www.youtube.com/watch?v=9bk07Ypx7GE
an other:
https://www.youtube.com/watch?v=ZAnU2xID9ZM&feature=youtube_gdata_player

« Last Edit: May 20, 2013, 10:25am by caisse433 »

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hello,I'm belgium driver since 32 years,winner of the 2011 belgian championship

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