Stalker Ackerman

[RichardSpillman]

Anybody know if the Stalker XL has Ackerman steering?

[FastG]

Is this a trick question? What are you really trying to ask? I think all modern cars have some Ackerman, it's built into the uprights. What uprights does a Stalker use?

Graham

[RichardSpillman]

They use a upright designed by Stalker. And a steering arm they make. Not all race cars have Ackerman built in.

[KB58]

I'll ask my brother, he has one.

[KB58]

For anything driven on the street, I'd certainly want it. Have you ever pushed a car through a turn with zero Ackerman? It binds up good.

[Lonnie-S]

My question is, "How much Ackerman is good enough?"

It's not a meaningless question. The software I'm using specifies things in terms of Ackerman error. Now, I'm smart enough to know less error is good, but then the question becomes, in genuine practical terms, what percentage is good enough?

Cheers,

[KB58]

My brother's Stalker is a 2006 and uses Chevy S10 2" drop spindles (which he changed to), but regardless, it's highly likely that Ackerman is the same as a Chevy S10.

[FastG]

I have never heard of a race car or any car without Ackerman, even entry level karts have it.

Graham

[ajmacdon]

If you want to start a huge debate at a bar full of vehicle dynamics engineers just bring up ackerman.

There was a theory that was popular for a long time that ackerman was not good on a track car. The idea is that the lateral force vs slip angle graph for a tire is load dependent and the peak of that curve occurs at a lower slip angle on a tire that has less normal force (e.g. inside tire in a corner). So, if you wanted both front wheels operating at their peak lateral force you would want the outside tire to have more slip angle than the inside which would point you towards lower ackerman. Some pretty mainstream race cars (trans am, at least) occasionally would even run negative ackerman based on tire data.

However, my thought is that if there's been this much debate about it at professional levels it's probably such a minor issue on track that for anything short of a 100% race car I'd take the easier parking of higher ackerman any day.

Alex

[Miatav8,MstrASE,A&P,F]

Anybody know if the Stalker XL has Ackerman steering?

From the pics I've seen, yes.
If the left and right tie rods do not form a straight line across the car, yes.
Inner tie rod pivots on the rack aft of outer tie rod pivots = positive ack.

Steering arms are usually as close to the rotor/tire as practical for a rack and pinion car.
Steering arms on spindles for a car using a steering box and linkage are closer to the vehicle centerline.

Ditto on some positive ack for the regular bloke.

[KB58]

Carroll Smith wrote that he found that the more (above zero) they used, the faster the car went, to a point of course. I agree that at our level of driving and the events we attend, it won't make any difference. From a practical aspect though, I suggest using 100%, simply to be able to push the car with the tires turned.

All this aside, because we tend to use OEM uprights, they're already set up for full Ackerman, so unless you're going full-custom, this whole discussion is moot.

[davew]

" Ackerman is the same as a Chevy S10." The S-10 came in three wheelbases and used the same spindle on all three. Plus the S-10 spindle was a carry-over item form the older GM "B"-cars. So there had to variation with the WB changes but the spindle designed in Ackerman was consider sufficient for a lot of different WB's. Plus to add to the comments, the Pratt-Miller Vettes run as high as 200% Ackerman on some tracks.
As long as you are in the ballpark, because it would be hard to say one size fits all!

[RTz]

It's not just the uprights. Fore/aft location of the rack also plays a role in Ackerman.

I built my car to 100% and would do it again.

[papak]

FWIW, we always used zero Ackerman on Formula Vees as the inside tire has decreasing load on it as the turning radius tightens. Slicks also tolerate a higher slip angle in that scenario.

[Lonnie-S]

There is an assumption that everyone reading this thread might know what "zero Ackerman" or "200% Ackerman" might mean. I don't. Does anyone care to define those terms?

Cheers,