ackerman for drift cars

[Swiftmini]

Hi, I have got pretty involved with drifting over the last year. I have been playing around with the ackerman angle to see what happens.

Has anyone on here got any experience, ideas, thoughts or opinions? please share.

Kev

 

[patprimmer]

When you are going sideways Ackerman does not matter at all.

Regards
Pat
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[GregLocock]

Ok there's two parts to a drift, getting into it, and then holding it.

In order to encourage rotation into the drift (say left hand turn) you want to stall the right wheel, one way (other than fiddle brakes), is to turn it in too far, which is >70% ackerman.

Once you are in the stable drift then you want approximately zero ackerman.

So you need to know what your steering angle is in each part of the turn, then set your ackerman curve up appropriately. One minute's thought suggests that one approach might be to use lots of negative toe out (I mean lots) and then negative ackerman to zero it out at high lock angles.

That will be very slow on the straights and give you even more horrible tire wear and will be an unstable pig, but I suspect that all of that is acceptable.

what sort of lateral (vehicle axis) g do you pull in these corners?



Cheers

Greg Locock

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[patprimmer]

I think sprint cars which are also in an almost continuous drift run the front wheels parallel at all times, however they are set to turn only one way by rear wheel stagger (big rolling dia on the outside wheel) and the brake on only the inside front wheel so they have several devices to assist turn in.

Regards
Pat
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[Swiftmini]

Thanks for the replies!

The majority of drift cars run lots of negative camber to try and keep the leading wheel upright when on opposite lock. This doesn't help the turn in very much.

Iam running 3 degrees of negative camber because I use my car on street sometimes, driving to shows and practice days etc so I make a compromise for tyre wear. Some guys are running 8 degrees on pure track cars.

To overcome poor turn we use weight transfer, clutch kick, dropping a wheel off of the track, down shifting hard too momentarily break traction and handbrake. Also setting the car so you can use the brakes to innitiate the drift. So starting the drift isn't really to much trouble.

Holding massive angles through corners with lots of speed is more what we need and having good feel through the steering.

So going by what iam reading above it would appear that zero ackerman is pretty ideal.

Iam not too sure how many g's to be honest.

An opinion that I was given by someone that's has been drifting for sometime is that for slow second gear corners it is nice to have some ackerman for transitions from one corner to the next. Also when drifting around a faster corner the trailing wheel is almost unloaded and probably doesn't matter very much!

The mods that I have carried out have made the curve quite weird. A third of steering lock is made in one turn of the steering wheel and the last two thirds are made in half a turn. My car turns the front wheel about 50 degrees on full lock, which is pretty good.

Iam in the process of deciding what too do next.

Thanks, your post have given me somewhere to start.....more reading of good books are in order.

Kevin

 

[Swiftmini]

Hi guys, I have been experimenting again and I have messed up somewhere!! I think!?!

Basically my car is superb when sideways but it has a straight line stability issues coming from the front end.

Its almost like really bad bumpsteer but my steering rack tie rods are nice and parallel.

I have shrtened the steering arm length by half (on the hub) lowered the mount point by 50mm to correct bumpsteer and removed a load of ackerman.

The grip when cornering is great and also whilst side ways.

I put a set of part worns on the front with 6mm tread and it has worn the drivers side to the wear markers and the pass side is worn smooth, it did this in 7 days of road use. The treads are heavily feathered.

I got the car aligned at protyre. The front toe is 1mm overall toeing in on the front edge.I actually asked for the toe to be set parallel

Wear is across the whole contact patch.

I need help to start looking in the correct direction.

Alignment? Play in a component? Ackerman?

Could a slight variation in ackerman side for side make a lot of diference?

Thanks guys I'll add pics of the tyre wear tonight.

Keving

 

[GregLocock]

In my post I should have said to stall the left tire going into a left hand turn.


"Its almost like really bad bumpsteer but my steering rack tie rods are nice and parallel."

Doesn't mean much to me.

Cheers

Greg Locock

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[LionelHutz]

Doesn't mean much to me.

Doesn't mean much to the bump steer curves either...

What diagrams or analysis have you done on the front suspension to see what's going on?

 

[Swiftmini]

Sorry guys I was generalising in a rule of thu.mb sort of way.

I cured the odd bump steer/tyre wear issue. It was play between two components.

Iam going back to the books though because I have realised the sheer size of the mine field that I have jumped into.

The stuff I was taught at uni has obviously only scratched the surface and I really need to read a few more books. Iam very happy with what I have achieved so far but there is always room for improvements.

As for plotting the suspension to get an idea, I started on autocad but soon got stuck because I wasn't sure on how to simulate the effect that the tiebars and position of the rack(moving it closer to the front or rear) would have when drawing the suspension looking from the front.

I will be back when I have done some more learning.