Which is more stable? 3 wheeler with differential steering, or...

[TheMadMonk]

3 wheeler steered by turning either 1 or 2 wheels.

All cases are bum between 2 x rear wheels and feet either side of front wheel, because I can't believe anyone (except the British) would seriously think shifting the center of gravity toward the apex of a triangle like the http://en.wikipedia.org/wiki/Peel_P50">Peel P-50 is actually a good idea.

1) 3 fixed wheels. with separate drives on rear wheels and steering by DRIVING one rear wheel faster than the other.

2) 2 driven fixed rear wheels with differential and steered by turning front wheel.

3) Power wherever you please. Fixed single front wheel, steering by turning rear wheels in unison.

4) Let's ignore the case or 3 x steered wheels.

[ChairmanAgnostic]

1. none of the above.

instead of turning a wheel, have a speed variable leg shortening system. Once you start to steer, depending on the speed, the leg in the direction of the turn will shorten. Slow speeds? less shortening. Higher speeds, greater shortening. The center of balance is always maintained, turning is accurate, safe, and easily accomplished.

[muriel_volestrangler]

2. Are you saying that a 3 wheeler is always more stable with 2 rear wheels and 1 front wheel?

That's what your sentence "All cases are bum between 2 x rear wheels and feet either side of front wheel, because I can't believe anyone (except the British) would seriously think shifting the center of gravity toward the apex of a triangle like the Peel P-50 is actually a good idea" appears to say.

Where your 'bum' is doesn't really matter. The mass of the engine or other car parts is more important; but more than that, when a vehicle brakes, weight is thrown to the front. If you only have one wheel there, it's unstable if you're also trying to turn. And braking always moves the weight around more than acceleration.

If you look at a list of three wheeler cars, you'll see many, and not just British ones, have 2 front wheels. Including the Canadian, 157 mph, Campagna T-Rex.

[DCKit]

3. What you said.

You've been looking at these things for awhile, eh?

[muriel_volestrangler]

4. It was pointed out to us when I was an engineering student

We were discussing stability under braking. And the Reliant Robin was a running joke in Britain then.

http://www.youtube.com/watch?v=roAKRTR69zU&feature=related

[TheMadMonk]

7. When your vehicle weight is less than passenger weight, yes bum...

between two apexes of a triangle is going to be a hell of a lot more stable than a bum right on top of one apex of the triangle.

Bwtween apexes aditional weight can only add to stability. over an apex it matters not a single whit whether it's 1 kg or a million. It's on the fulcurm it's irrelevant.


Weight thrown to the front in braking is a valid point, but we are looking at it from two different directions. At 1000kg plus gross vehicle mass, it is hellaciously advantageous to apply extra braking force at the front and "dig in" when stopping. At <200 kg gross (with passenger) vehicle mass the need to "dig in" to stop is much reduced, juddering and shredding rubber on the rear wheels will suffice to bring you and your vehicle to a stop in sufficient time to avoid serious injury to others in an emergency AND maintain vehicle stability. I leave it as an exercise for the driver to avoid taking their vehicle into oncoming or cross traffic. (Think bicycles (and a stick in the front spokes) not cars here.)

I'm thinking small (possibly embarrassing to "real men") electric personal people movers here, not a publically visible surrogate for wedding tackle. At 157mph I want either Shumaker beside me or 40 lb/ft steel rail (or 1000+ ft of atmosphere) under me. (Sorry, I've seen one too many vids (that would be one) of Romanian truck drivers on youtube.)

[muriel_volestrangler]

10. If this is something you want to knock up yourself, then 1 front wheel may be fine

because it's simpler, and you're looking at low speed anyway, so the stability isn't a real issue. And the simple bit is steering with that one front wheel - just like the front wheel of a two-wheel scooter.

You could be looking at a design like the Sinclair C5: http://www.youtube.com/watch?v=0EQetm_qWDg&feature=related

They were a flop, in 1985.

[PJPhreak]

5. I don'y know about all this But,

This looks like a Hoot to ride...



And it is powered by the same engine as the Aprilia RSV 1000 R Superbike,So you know it will RUN!

[TheMadMonk]

8. Where's the rider, and hence any contribution his weight might have ...

...to the centre of gravity?

This is the question I'm essentially asking.

Assuming minimalising elsewhere: overall mass, length and width (and not presuming a prone or recumbant rider.)

[Occulus]

12. I just went to the website for that

That is one nice bike.

[Fumesucker]

6. The Piaggio MP3 gets good marks for handling..

[TheMadMonk]

9. Not a three wheeler in the traditional sense.

What I'm working towards is something I can knock up in the back yard with a hammer, shifter (adjustible spanner) and whatever's left of a socket set after a three year old has "repaired" his toys.

[hunter]

11. Why not four wheels?

It may or may not be related to what you are doing, but if a three wheel motor vehicle can be a "motorcycle" by law, why not have a class of four wheel motorcycles?