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Old 12-11-2017, 05:29 AM
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Originally Posted by heretic View Post
Late to the party again, Paul.



Hey at least looks like it could be a sensible idea no matter what... unless we're both wrong, of course, which isn't beyond the real of possibilities

But, yeah, I'd get rid of that SS... the trick is, if the OP's car ackermann is optimal-ish by now, a single pivot point would whack the geometry off. This means a dual-point servo arm, or an extra bit of pivoting kit (a tiny bit of cwf for instance) to partly mitigate it.

How about just making it solid? a beefy tie-wrap tightened around the spring can do the job in a few seconds to already give you a feel of what driving without that likely springy link feels, and is easily reversible

(I always drove with a hudy "extra stiff" SS up until a couple of years ago on all my touring cars, be they xray or others... then I switched to a solid arm in the middle of a race day once as I was looking for a tiny bit more steering - I never went back as the car was very different, and much better.... and I haven't broken any servo either. SS do "open" during normal driving, not just when crashing)
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Old 12-11-2017, 06:38 AM
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So much details... I am lucky to have you around. Servoposition and servo arm are in my focus now.

Edit: I played around with the servo position and found no positive effect on Ackermann. Package wise a 1/12 sized servo brings no benefit because in one dimension its size is greater than of a normal low profile one.

Having a standing servo seems to have a positive effect on bumpsteer, but would need a new complicated mount. Right now I am not motivated to build one.

The solid servo arm is easy to do as I found an old Xray arm which was too short for the T4 and now will serve as base element for a carbon plate.

Last edited by wtcc; 12-11-2017 at 10:08 AM.
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Old 12-11-2017, 11:05 AM
  #108  
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Car looks great! You might try a higher rear roll center to free up the rear, especially going into turns. Also, if there's a way to sweep the front bones backwards a little, either through moving the arms back or angling them back, you might be able to increase your front traction under acceleration. It will cause the front bones to twist upwards, which lifts the tires but keeps the front of the chassis down. It works great in 4wd, worth trying in Fwd. It can also increase working steering angle, although you shouldn't need that for on road.
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Old 12-12-2017, 03:15 PM
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How did you setup the ackermann? True,less or more ? I have the same issue with my mf-fwd.
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Old 12-13-2017, 07:57 AM
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Good question

My inner tire can turn up to 26.5*, my outer tire then has 23,0*. True Ackermann would be 26.5*-20.5*=6* at a wheelbase of 259mm and a trackwidth of 172mm in front. So the KR-MF is 2.5* on the agressive steering side.
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Old 12-13-2017, 08:50 AM
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Originally Posted by wtcc View Post
Good question

My inner tire can turn up to 26.5*, my outer tire then has 23,0*. True Ackermann would be 26.5*-20.5*=6* at a wheelbase of 259mm and a trackwidth of 172mm in front. So the KR-MF is 2.5* on the agressive steering side.
Can you define "true"? do you have zero rear toe?
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Old 12-13-2017, 09:18 AM
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Indeed... 0* rear toe (at the moment). But I am no engineer... can you explain the geometry change through rear toe in on the front ackermann angles? Please.

Last edited by wtcc; 12-13-2017 at 09:50 AM.
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Old 12-13-2017, 01:43 PM
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Lonestar, take a look on RCCrewChief videos on ackermann, you will see what "true ackermann" is...
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Old 12-14-2017, 08:33 AM
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Originally Posted by Airwave View Post
Lonestar, take a look on RCCrewChief videos on ackermann, you will see what "true ackermann" is...
I know what "true" Ackermann is, mon ami


One can't have have all four "wheel median" lines (not sure how to call them, really...) intersect in one point if one has rear toe. You can maybe get the two fronts and the "overall rear" intersect in one point, that'd be "semi-true", but not truely true Or you can think about having the 2 front and the one outside rear, maybe that could be a good idea, outside wheels matter most anyway.

This gentleman has zero rear toe on his (gorgeous) car, so it can be "true" for real
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Old 12-14-2017, 01:48 PM
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Very interesting detail! That would mean that with 3* rear toe in you get a crazy far away intersection point from the three tires. Does any of the engineers really care about that? I can't even find pictures on Google that show rear toe in when describing Ackermann.
And will there be an effect just through the real Ackermann change through toe in?
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Old 12-14-2017, 03:51 PM
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Originally Posted by wtcc View Post
Very interesting detail! That would mean that with 3* rear toe in you get a crazy far away intersection point from the three tires. Does any of the engineers really care about that? I can't even find pictures on Google that show rear toe in when describing Ackermann.
And will there be an effect just through the real Ackermann change through toe in?
In hard cornering when you lift the inside rear wheel it might have an effect, but otherwise the rear toe effectively cancels itself out and you can ignore it.
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Old 12-14-2017, 04:17 PM
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Given how much I love homebuilt vehicles...

We used to drive a certain Dirt Oval car, which had its steering servo in the front as well!

But if you wanted to play with Bump Steer etc. the Custom works sliding steering rack is a huge space saver, and simple, can be easily cloned in Delrin too.

Just as an Option, as if you stood the servo up you have a bit of room

- yes it was the best dirt oval car hands down - the SRP-1!

These are of Dougs car!
Attached Thumbnails wtcc's FF project-cw-steering.png   wtcc's FF project-cw-steering-rack.jpg   wtcc's FF project-srp-1_002.jpg   wtcc's FF project-srp1_restoration_003.jpg   wtcc's FF project-srp-1_004.jpg  

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Old 12-14-2017, 08:06 PM
  #118  
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Again, what a great thread!
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Old 12-15-2017, 12:15 PM
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The 60mm turnbuckle shafts arrived from Denmark:






Right now I am sitting in front of my computer trying to make a steering racket for the little space between servo and differential... This time I am not sure if this "story" called "collisions everywhere" will have a happy end.
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Old 12-15-2017, 12:17 PM
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Originally Posted by wtcc View Post
The 60mm turnbuckle shafts arrived from Denmark:






Right now I am sitting in front of my computer trying to make a steering racket for the little space between servo and differential... This time I am not sure if this "story" called "collisions everywhere" will have a happy end.
Awesome stuff!
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