John St.Amant

iTrader: (1)

CraigM

iTrader: (34)

Can someone stick their car on a setup station and confirm this? I would but my setup station doesn't do steering throw

Reason I ask is because I was reading the Paul Liemaux (however the hell he spells it) thread and he said more ackerman = more off power, less on power. So I added some spacers and then one of my mates remarked how little ackerman I was running

... so I'm thinking Jimmy is right in his cause/effect but not the definition maybe?

More angled links = More Ackermann = tighter tracks/more steering = more off power steering.
More straight links = Less Ackermann = flowing tracks/less steering = more on power steering

would like to validate that though...

sagejyoung

i am unable to explain how it works but i would think that you would want more off power steering on tight tracks and hence you would adjust the ackerman accordingly.... i wait with interest for someone with more experience to validate the ackerman issue.....


also i would like to know of ackerman is more of a lateral adjustment? like when the links are more horizontally angled or if you can adjust ackerman via the vertical adjustment of the links..??? or both?

tonyv

iTrader: (1)

Ok, first the definition. The Ackerman angle is the difference in angle between the inside and outside front wheel during cornering. For simplicity think full steering lock.

The bigger the difference in angle, the bigger the Ackerman angle.

Knowing this it is easy for you to test yourself that:

More angled links = Less Ackermann
More straight links = More Ackermann

And that tells you exactly nothing about the actual effect. So let's first think about the basics. During cornering the inside wheels follows a tighter arc then the outside wheel. To prevent the inside wheel from scrubbing this means it needs to make a bigger angle then the outside wheel since a bigger angle means a tighter arc. This is where the Ackerman angle comes in.

The tighter the corner, the bigger the difference in angle needs to be between inside and outside wheels. I.e. the bigger the Ackerman angle. So normally you would run more Ackerman on tight tracks and less on large flowing tracks. In both cases you do that to minimise wheel scrubbing (efficiency, cornering speed) and as a result maximise steering.

Hope this makes a bit more sense.

sagejyoung

thats a solid explanation thanks. what im asking is could the ackerman angle change depending on the angle of the links horizontally or vertically? so in relation to the ground ackerman changes buy the more angled to the front or back of the car the links are, and also how angled the links are from the ground to the sky (vertical)?

John St.Amant

iTrader: (1)

Achermann does not effect on or off power... but slip angle and mid corner. If you want more on or off power you need to adjust caster or center shock.

veecee

iTrader: (34)

So does more Ackermann give more or less mid corner steering?

John St.Amant

iTrader: (1)

More Achermann means more mid corner... yes its measured at full lock too.

JimmyMac

iTrader: (2)

I guess it depends which chassis you apply this too. I know the more angled the steering links are, the more steering you get for tighter corners. This applies to both my 416 and my XRay. My quotes were from XRay manual/setup guide. But you can apply this to most chassis out there.

TryHard

iTrader: (4)

Bear in mind that the links angle differently on the Xray compared to the Tam... I.e. moving it forward on the inner piviot on the Xray gives more of a link angle, moving it back less.

Adding more angle to the link is effectively the same as shortening at full lock. So adding more angle to them does two things... reduces the steering angle of the outer wheel, and increases the angle of the inner wheel. So putting more angle on the links (losing spacers on the Tam), will give a bigger Ackerman angle. Good guide to what ackerman does is here

http://www.rc-truckncar-tuning.com/ackerman.html

Ackerman is strictly a lateral change, if you change the ball studs in hieght, your adjusting the bump steer characteristics, i.e. how much the steering turns under suspension compression.

HiH
Ed

tonyv

iTrader: (1)

Actually, that depends. In flowing corners increasing Ackerman would in fact decrease mid corner steering as the inside wheel will lose grip and start dragging. Either one of two things will occur at this point. Either the car will get understeer or it will snap oversteer due to the dragging inside wheel. In either case you lose momentum.

In tight corners on the other hand increasing the Ackerman will increase mid corner steering.

RC MARKET

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weekend back in stock

redbones

wouldn't a spool make this worse since it will drag the fronts no matter what?

John St.Amant

iTrader: (1)

Dont go confusing the subject..
But if you think about it.... A spool pushes mid corner and more Achermann will help that . And the inside tire never diffs out. But excess yaw angle makes for inefficient turning and yes it scrubs of loads of speed.

tonyv

iTrader: (1)

For the principle it makes no difference whatsoever. The only thing that may change is that the amount of Ackerman that is optimal for a given track will change. In fact several aspects of your setup may need updating due to the fact that the spool, as John indicates, will push off power compared to a front one-way. Depending on what you changed you may feel a bigger or possibly even a smaller Ackerman angle is needed compared to a one-way on the same track.

To put things in perspective, in one race I ran a one-way and spool setup back to back. With the one-way setup I managed to have the car understeer. Something that is quite difficult to achieve with rubber tyres on carpet in mod. With the spool I managed to get the car to turn in much better even with a touch of mid-corner oversteer. The latter possibly could have been solved by running a touch less Ackerman.