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Old 03-04-2014, 03:33 PM   #76
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Originally Posted by Martin Crisp View Post
Hi,

I would change from 2 degrees caster to 4 degrees caster. That should help the push feeling you have at speed. It may even help with the low speed twitchy feeling you mention. I think the low speed on power twitchy feeling you have could also be a result of the rear toe not being enough...so moveing to 3.0 rear toe will help keep the rear planted on hard acceleration out of low speed corners. I also think you are on the right track about potentially lowering the rear roll center, but try the rear toe first and then add the lower rear roll center.

Martin.
Thank you for your input.

Re caster the change from 4 deg to 2 deg caster was to improve turn in at low to mid speed and reduce exit steering at low speed to help with the rear end.

The car was twitchy with 4 deg caster as well and I consider the change was an improvement to compensate for other issues that I was not able to resolve at the time (new car and I didn't have any blocks to increase rear toe in or shims to adjust roll center).

Last edited by frozenpod; 03-04-2014 at 03:53 PM.
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Old 03-04-2014, 04:22 PM   #77
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What about servo speed?
With my old vta car few yrs ago I slowed the speed of the servo response down to help the car transition better expecially on outdoor tracks. Now vta is a super slow class overall but is there something to this or was I just patching up a bad setup or bad driving ?
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Old 03-04-2014, 08:58 PM   #78
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I have your app and I love it. Today I decided to go ahead and subscribe to learnsetup.com

This may be asking too much but if you every get the chance to blog, maybe do a quick writeup on droop setup and clarify the difference between using blocks and over ride height method.

I do both according to manufacture, on my xray I use the block method as recommended and my Tamiya I measure to the pin of the arm, on my yokomo I measure orh. When I actually go measure droop on each car I find myself between 2-5mm depending on conditions. To make sure it short, is there a squash all method of measuring droop?
The block approach is probably the most accurate way to do it, but I prefer to use the "over ride height method" because you don't have to take the wheels off, so I can do it faster. When I first build a car I will use the block method, but when I am at the track I tend to just use the above ride height method because it is quick.

The way I do the above ride height method is to first check the ride height when the car is just sitting on the table (assume it is 5mm). Then I lift up that end of the car until the tires are just about to come off the table...then I measure the ride height at that point (assume it is 7mm). The difference of 2mm is the droop.


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Hi Martin,

What handling characteristics make you decide that a car needs harder or softer shock oil? Same question for rebound?

Thanks!
Rebound seems to have a different definition in the RC world than in full size car racing. If by rebound you mean how much the shock will extend after being fulling compressed (without any springs on the shock), then my answer is I never run rebound as the purpose of the shock is to slow down the spring, not speed it up.

If you have too much dampening in the shocks the car will tend not to absorb bumps well in the corners and you will find it harder to put the power down. Keep in mind there are many other causes of those handling traits and your dampening might be just fine.

If you have too little dampening the car will transition "flop" too quickly into 'taking a set" when cornering, unsettling the car when it reaches the set because of the transition speed. Also the car will likely take multiple sets as you enter a corner.



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What about servo speed?
With my old vta car few yrs ago I slowed the speed of the servo response down to help the car transition better expecially on outdoor tracks. Now vta is a super slow class overall but is there something to this or was I just patching up a bad setup or bad driving ?
Slow servo speed may sound like it will smooth out your driving, but it will make your driving less precise. Imagine if you are driving your real car on the road but instead of holding the steering wheel directly you attached one end of a big elastic bands to your steering wheel and the other end to your two hands. Your car would be much slower at reacting to your inputs. This is what it like driving with a slow servo. Always invest in a fast servo.
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Old 03-06-2014, 07:28 AM   #79
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Default March 4th update to LearnSetup.com app

  • Added a section providing more details about Weight Transfer
  • Simplified the “ride height section“

http://www.learnsetup.com/march-4th-...setup-com-app/
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Old 03-06-2014, 01:59 PM   #80
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Hi Martin, I have sort of a radical question.
Does a TC have enough roll in it, to unload the inside tire enough that Anti-Ackerman would be beneficial?
In theory if the car rolls over enough and the vertical load is reduced enough the slip angle decreases and the extra steering angle from the Ackerman effect is just scrubbing speed. before I sat down and actually tried to do this on my T4 I wanted a second opinion.
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Old 03-06-2014, 04:16 PM   #81
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Hi Martin. When I first got into Touring Cars ~2004 I bought your Chassis Setup Guide. Thanks for providing a comprehensive and easy to understand source of information on how to tune a car. I've found the advise transfers to offroad vehicles too. I probably should ask for a commission for all the people I've referred to your book over the years HAHAHA. Look forward to following your thread.
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Old 03-06-2014, 06:52 PM   #82
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Originally Posted by patorz31 View Post
Hi Martin, I have sort of a radical question.
Does a TC have enough roll in it, to unload the inside tire enough that Anti-Ackerman would be beneficial?
In theory if the car rolls over enough and the vertical load is reduced enough the slip angle decreases and the extra steering angle from the Ackerman effect is just scrubbing speed. before I sat down and actually tried to do this on my T4 I wanted a second opinion.
Awesome question. You could setup your car to unload the inside tire that this would likely make a difference. I have never really tested it however. I like to play with ackerman to add or take away front steering, so it is as a good thing to experiment with.

In general however if I am trying to get more lateral grip from the front, I would being trying to decrease the unloading of the inside front tire to maximize lateral grip. One of the best ways to do this is to raise the front roll centre. Adding a stiffer front sway bar by the way would make it worse.

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Originally Posted by John Wallace2 View Post
Hi Martin. When I first got into Touring Cars ~2004 I bought your Chassis Setup Guide. Thanks for providing a comprehensive and easy to understand source of information on how to tune a car. I've found the advise transfers to offroad vehicles too. I probably should ask for a commission for all the people I've referred to your book over the years HAHAHA. Look forward to following your thread.
Hey John. Thank you! You did not get the cheque?

Yes, for sure the theories outlined in the book/app applies to offroad as well. There major difference is really understanding what a good baseline setup would be. Also although I only did off-road for one summer, I found tire knowledge/selection for track surfaces is a new skill you need to learn for off-road.
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Old 03-07-2014, 02:35 AM   #83
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Hi Martin,

I heard some Pros tuning the damper piston position by changing shock's length, do you usually do so and how does it affect the car balance? Thanks.
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Old 03-07-2014, 06:58 AM   #84
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Originally Posted by Martin Crisp
Hi,

I would change from 2 degrees caster to 4 degrees caster. That should help the push feeling you have at speed. It may even help with the low speed twitchy feeling you mention. I think the low speed on power twitchy feeling you have could also be a result of the rear toe not being enough...so moveing to 3.0 rear toe will help keep the rear planted on hard acceleration out of low speed corners. I also think you are on the right track about potentially lowering the rear roll center, but try the rear toe first and then add the lower rear roll center.

Martin.

Quote:
Originally Posted by frozenpod View Post
Thank you for your input.

Re caster the change from 4 deg to 2 deg caster was to improve turn in at low to mid speed and reduce exit steering at low speed to help with the rear end.

The car was twitchy with 4 deg caster as well and I consider the change was an improvement to compensate for other issues that I was not able to resolve at the time (new car and I didn't have any blocks to increase rear toe in or shims to adjust roll center).
Update, I went to 3 deg rear toe in and which was a considerable improvement, added 0.8mm shim in to inboard upper rear link and the rear end was glued to the track at all speeds.

To improve on power steering I went with stiffer rear springs, thicker rear diff oil, stiffer sway bar and 4 deg caster.

Car was well balanced through high speed sweepers but still lacked inital turn in.

I added 0.8mm shim to the inboard upper front link resulting in extra steering all round still a touch lacking inital turn in.

Almost dialed.
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Old 03-07-2014, 07:52 AM   #85
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Originally Posted by frozenpod View Post
Update, I went to 3 deg rear toe in and which was a considerable improvement, added 0.8mm shim in to inboard upper rear link and the rear end was glued to the track at all speeds.

To improve on power steering I went with stiffer rear springs, thicker rear diff oil, stiffer sway bar and 4 deg caster.

Car was well balanced through high speed sweepers but still lacked inital turn in.

I added 0.8mm shim to the inboard upper front link resulting in extra steering all round still a touch lacking inital turn in.

Almost dialed.
Sounds like things are getting better

Try adding a little bit of toe out on the front to help with the initial turn-in.

What are you running for front and rear droop in the car?

Also - I am surprised to hear that adding more shims to the inboard upper front link added more steering all around. Typically that will take away steering especially in the middle of the corner, but might feel like you have a little more initial turn-in.
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Old 03-07-2014, 08:14 AM   #86
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Hi Martin, I would like to know when do you use the hard arms and the soft arms or the medium arms?
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Old 03-07-2014, 08:16 AM   #87
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Since you've raced real an r/c cars, how do you translate "picking your braking point" to r/c? The hardest thing I find is consistently hitting the spot to slow down, and slowing down the same amount, each lap. It turn that also relates to reacting to what car has done in a turn instead of making the car do what you want it to, got any tips on that?
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Old 03-07-2014, 09:26 AM   #88
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Hi Martin,

Great thread and a great app too. I have some things which have been on my mind for a few weeks, perhaps you can clear things up for me.

Raising/lowering camber link both inner and outer positions, changing the camber link length and altering wishbone height all change roll center and camber gain. My question is what is the difference between these settings, or do they all behave the same? In what situation would you choose to change one of these settings in preference to another?

I read a lot about RC setup and rarely if ever see a mention for steering axis inclination or scrub radius. Are these things not important in RC?

And my big question is without any prior knowledge or base set up for a car how would you approach initially setting the car up and finding a base set up? Where do you start?!

TIA!
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Old 03-07-2014, 09:30 AM   #89
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Since you've raced real an r/c cars, how do you translate "picking your braking point" to r/c? The hardest thing I find is consistently hitting the spot to slow down, and slowing down the same amount, each lap. It turn that also relates to reacting to what car has done in a turn instead of making the car do what you want it to, got any tips on that?
Hitting the same spot and applying the same amount of brake force lap after lap is difficult. Easiest way to slow down the same amount is using drag brake. Or to set your brakes to slow down to a setting that doesn't upset or make the car spin in turn.



Hey Martin.. Long time no talk... Gonna come race off-road with us?
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Old 03-07-2014, 10:09 AM   #90
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Hey Martin.. Long time no talk... Gonna come race off-road with us?
I think you should come race onroad, Dino. Get a couple of those Durango TCs for you and Glenn.

Martin, I must applaud you for not only all the hard work you put into your app and the original setup book, but also into replying to questions on here. I only vaguely understand all the setup stuff, which is why I rarely stray too far from the kit setup (aside from also being lazy), but I'm hoping one day it will eventually sink into this thick skull of mine.

See you next weekend!
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