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Author: Subject: Rear-Suspension...
scootz

posted on 26/6/10 at 05:04 PM Reply With Quote
Rear-Suspension...

How important is the rear suspension on a Reverse-Trike?

Has anyone built one, or know of a design using a hard-tail (no swinging-arm or damping whatsoever)?

I can't see how a vertical suspension movement would really improve the handling over a hard-tail set up... sure, maybe an issue for comfort, but let's be honest - is a Reverse Trike based on a Formula single-seater going to have any real levels of comfort anyway?

Would be interested in any thoughts!





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zilspeed

posted on 26/6/10 at 05:26 PM Reply With Quote
quote:
Originally posted by scootz
How important is the rear suspension on a Reverse-Trike?

Has anyone built one, or know of a design using a hard-tail (no swinging-arm or damping whatsoever)?

I can't see how a vertical suspension movement would really improve the handling over a hard-tail set up... sure, maybe an issue for comfort, but let's be honest - is a Reverse Trike based on a Formula single-seater going to have any real levels of comfort anyway?

Would be interested in any thoughts!


Don't quote me.

But, I thought hard tails were now banned for IVA or whatever the bike one is called.

In any case, the suspension isn't about keeping your sphincter comfortable, it's about keeping that tiny little tyre patch working.

Fast corner, dab of power, bump in middle of road, single rear tyre. Wooooaaaaahhh.

Fit rear suspension if you really must build this trike.

Enjoy

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smart51

posted on 26/6/10 at 05:28 PM Reply With Quote
It would improve grip to have suspension. Roads are uneven and an unsprung wheel has the tendency to skip off the top of bumps. The suspension pushes the wheel down more quickly than gravity alone so it stays in contact with the road more. Other than that, there's no twist so you don't need it to adjust the height of 2 wheels on 1 axle.

With no bending of joints or compressing of bushes, the rear wheel will stay pointing straight even in fast corners.






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scootz

posted on 26/6/10 at 05:34 PM Reply With Quote
Cheers guys!





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James

posted on 26/6/10 at 08:14 PM Reply With Quote
quote:
Originally posted by scootz
is a Reverse Trike based on a Formula single-seater going to have any real levels of comfort anyway?



I thought you had a bad back or something?

You *sure* this is a good idea?

Cheers,
James





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scootz

posted on 26/6/10 at 08:44 PM Reply With Quote
It is a ridiculous idea James, but it keeps my brain busy!

You don't actually think I'll want to get in it, far less drive it do you!?





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v8kid

posted on 26/6/10 at 09:06 PM Reply With Quote
Hmm... interesting! Conventional wisdom says that the driven wheel suspension frequency (read stiffness of suspension since we are being approximate) should be approx 20% or so less than the non driven wheel.

But that is for 4 wheels and assumes that the rear wheels follow the same approximate track as the front wheels.

Clearly for this (reverse trike?) this is not the case. Are we to assume that bumps always extend across the track radially or tangentially? I think neither, at least not always.

In short I havn't a bl00dy clue to the answer!

If I were to guess I'd say.........make it 40% softer but damp it twice as much - but thats just a guess.

Cheers and enjoy your musings

David





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hexxi

posted on 9/7/10 at 05:49 AM Reply With Quote
I`m also building a reverse trike. What kind or role does the lenght of the rear swingarm play?

To keep the overall length of the vehicle as short as possible, I`d like to use as short swingarm as possible. Is it bad in terms of handling or is longer swingarm better in general?

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smart51

posted on 9/7/10 at 07:05 AM Reply With Quote
With 3 wheeled vehicles, long and wide is good for stability. I'd want to keep the wheel base in proportion to the track though. 1.6:1 is supposed to be a good balance between straight line stability and eager cornering. I can't remember where I heard this though.






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iank

posted on 9/7/10 at 07:59 AM Reply With Quote
quote:
Originally posted by smart51
With 3 wheeled vehicles, long and wide is good for stability. I'd want to keep the wheel base in proportion to the track though. 1.6:1 is supposed to be a good balance between straight line stability and eager cornering. I can't remember where I heard this though.


I've seen that figure used and it's probably reasonable as a first approximation but a little naive as it doesn't address either driver preference or what use the car's being used for - that's why top fuel dragsters are long and narrow while karts are short and wide. Problem is it's difficult to change once built and tested - reverse trikes being the easiest cars to adjust with different swing arms and wishbones for aspect ratio. BUT I don't know if the aspect ratio's for 4 wheelers translate into 3 wheelers in a straightforward sense

On the subject of swingarm length. One thing to consider is the range of movement at the shock and the spring rates you'd need, without pushrod suspension a short swing arm would have very little movement at the shock which is a bad thing. I'd be looking at how the motorbike boys work out the optimum.





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hexxi

posted on 9/7/10 at 08:03 AM Reply With Quote
I`m not trying make the vehicle short, I`m just trying to keep the vehicle from getting ridigulously long. There will be two seats behind each other, the engine behind them plus the rear wheel. Therefore I`d like to use a short swingarm.
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smart51

posted on 9/7/10 at 08:26 AM Reply With Quote
quote:
Originally posted by iank

I've seen that figure used and it's probably reasonable as a first approximation ... Problem is it's difficult to change once built and tested - reverse trikes being the easiest cars to adjust with different swing arms and wishbones for aspect ratio. BUT I don't know if the aspect ratio's for 4 wheelers translate into 3 wheelers in a straightforward sense



Quite true. Short wheel bases with wide track are a bit twitchy but turn in well. Over do it and they turn over well though. Longer vehicles are more stable in a straight line at speed but tend to stay in a straight line even if you want to turn. I can't see a reason why a trike would be different about the straight ahead.

Top design rules for 3 wheelers are keep the weight low and near the 2 wheeled axle.






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