To put my answer in perspective I designed and developed the suspension on two three wheeler solar cars, which had a single wheel at the front for good reasons, but safety and handling weren't prime considerations in that choice.
OK, how much money have you spent so far? It might be a really good idea to throw the plans away and build something else instead, the potential instability of single front wheel vehicles is well known. If you fit the batteries low then that will minimise this problem.
However, if you are determined to proceed, then you need to be aware that limiting the turning circle won't really help except at very low speeds.
Typically when driving at normal speeeds, or even racing, you only use about 1/2 a turn of the steering wheel. Most cars have around 1.2 to 1.5 turns from centre to lock. So you don't actually need much lock to generate the full cornering capacity of the tire.
I'll split the next bit into two parts - answering your question directly, and then some theoretical stuff which may or may not lead anywhere.
1) Limiting the lock is best achieved at the steering wheel, as the forces are smaller, but in practice that is difficult to achieve, so most people just fit a mechanical stop to the steering arm. That's fine.
2) What you really need is a way of limiting the max lat acc of the vehicle. The usual approach is gobs full of understeer. You can do that at the front axle or the rear. At the front you could do this by shifting weight forward, and so try to overload the front tire, or fit a smaller tire. Neither approach is good, and shifting weight around can make things worse. I can't think off hand of anything else that you can do there, mechanically. So, if we work with the rear axle the trick is to make it steer into the curve, using either the suspension geometry, or the suspension bushes, or more likely both. The other option is to increase the roll stiffness at the back (well, the front has zero roll stiffness) and then try and saturate the outer tire. This is a bad idea, as it will cause the car to spin, which might be less alarming than a roll, or it might not be. (our solar cars would spin, even though they understeered most of the time).
The 'proper' solution these days is active intervention, but that is not practical for a homebuilt project.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
