Turning Radius Vs, Wheelbase

[BMX1253]

I just wanted to know what ya'll think a good turning radius is compared to the wheelbase of the rail.

At what point do you think it becomes unsafe to have the wheels turn to tight?

Just want to know what ya'll think, is there no point where turning becomes to tight?

[nutz4sand]

I have actually drove a Desert Karts panther that would turn the OUTSIDE tire in a turn almost dead 90 degrees (BAD reverse ackerman. Inside tire should have been sharper of course). It was well past 80 degrees! It was/is almost pointless as at those angles the tire is acting far more like a brake than a tire. Its so sideways that its trying more to drag the buggy that way (outside tire of the turn remember) than the way it was pointing (which is basically the opposite way)

Say you turned it to the left. The right tire goes from rolling on its bearings and trying to push the front end to the left and as it gets so sharp compared to the rear end it can not longer roll on its bearings as its being literally drug sideways itself as the buggy went forward. Then it tends to try to drag the front end back to the right. Makes for poor steering.

What was even more amazing was that it would steer to this sharp. Then steer back to straight with no other issues other than MESSED up ackerman. No locking of the spindles as they moved the tierods past the spindles pivot!

Chances are and this is what many/most buggies seem to do. If you steer TO sharp. The front tires will actually overtravel the design and one tire will LOCK as it goes past the tierods limit! Once tierod goes inside the line of the ball joints i often will not come back out unless you kick the tire back the toher way. Very bad and dangerous.

Many times the rack does not have enough travel to do this but if it does and you go to sharp the tires are near perpendicular to the rear.

Mush less angle is actually needed if you have a spool and not a diff. An open diff or LSD that can slip will turn sharper and can us more steering angle to actually steer. With a spool my expieriences have been been that turning to far and getting on the gas (Heck even coasting) makes for it trying to go straight with the brakes on the front only and it feels like with the tiniest steering input "KINDA" guiding you toward the way you are steering. But it will usually be squirrely as hell.

Each chassis will be different.

[evan]

IMO...make the spindles turn as sharp as possible. The extremes aren't used for tight turning, but instead for countersteering while in a slide. Nothing will piss you off more then spinning out in a perfectly controllable slide because you run out of steering angle. Just be sure to make stops that prevent over-travel and tie rods breaking over center as mentioned above.

[BMX1253]

That's a good point Evan. I am in the middle of building a small cart with a 5hp motor for something to learn on and I researched all the other angles, Camber, Caster, KPI, Ackerman, All the fun stuff. I just forgot when attaching the front clip to the frame, that when wheels turn, they go into where the frame is, lol. Noob mistake, but I'm learning and I want to learn on this small buggy with 5hp not the one I build with a GS1000 I also have.

I measured the angles I have now and it looks like on the inside tire I can have 40* and on the outside tire I belive it will give me 31* with a correct ackerman position. With a wheel base of 56" and a width (center of tire to center) of 26" it gives me a turning radius of just under 8'. Roughly, I can turn a circle in 3 lengths of the cart.

Should I design it to turn tighter, or do ya'll think that is enough? It's not going to be a highspeed cart or anything. Just something to learn on and have some fun with.

[Glock n Ballz]

Just in case here's the Ackerman link:
RcTek - Radio Controlled Model Car Handling Main Section Page

[RickS.]

I measured the angles I have now and it looks like on the inside tire I can have 40* and on the outside tire I belive it will give me 31* with a correct ackerman position. With a wheel base of 56" and a width (center of tire to center) of 26" it gives me a turning radius of just under 8'. Roughly, I can turn a circle in 3 lengths of the cart.

Should I design it to turn tighter, or do ya'll think that is enough? It's not going to be a highspeed cart or anything. Just something to learn on and have some fun with.

Something to consider if you plan on using heim joints mounted like this on your spindle uprights.

The sum of the inside and outside turning angles cannot excede the angular limits of your High Misalignment Spacers. For example: A 3/4 HMS with 1/2" bore typically has somewhere around a 60 degree limit. Therefore if your inside wheel were to turn 35 and outside 25 you would be at the 60 degree limit of your HMS.