CMS limits steering?

[SynisteR6]

Hey guys, still a bit of a newbie here but thanks to all the great threads and advice in the forums I feel far more confident then I ever used to.

I installed an RC4WD CMS/Panhard kit on my wraith. I know there is no performance gain, but I like the idea of being able to easily separate the chassis from the body easier with the CMS kit. My issue is that due to the change in angle from the servo to the ackerman, it seems to have limited my steering, especially to the right. Its almost that the servo turns beyond usefull stroke. I haven't take any pics of my setup but here it is from the RC4WD site. Has anyone else battled this or have any suggestions? Any help is greatly appreciated. (one is with the bent link, one with the straight - I don't think that makes a difference)

 

[cincycrawln]

try powering up the servo and centering the servo horn to have equal steering both ways. hard to say what the true issue is without knowing your set-up

 

[SynisteR6]

Thanks for the reply. I hae done that with the original setup and have gone back a few more times to make sure.

I wonder if the issue is that even though the servo has equal swing both ways, the relation of the arc of swing from the ackerman arm is not the same side to side, does this make any sense?

 

[cincycrawln]

What c-hubs, knuckles, and steering link are you running

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[SynisteR6]

stock chubs and knuckles are the stock kit plastic ones, link from the servo to the ackerman was supplied with the rc4wd kit, and the link between wheels is STRC

 

[cincycrawln]

Do you have stock dogbone axles

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[Scocrawler]

May just be the angle of the pic, but appears you axle is not centered under the chassis. If the axle is offset to the right that could be some of the issue. Good luck!

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[cincycrawln]

The pic was from rc4wd to show his cms kit. That's not his actual truck

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[MexicanMarauder]

Its look to me that your truck height needs to come down. I was having the same problem with mine. Just lower the truck down a little and you will gain turn radius.

 

[SynisteR6]

Do you have stock dogbone axles

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I believe where it is a kit it has universals in it, not dog bones. But I'm still a newbie and not home to check right now

The issue to me looks as though when the servo is pulling the steering link (to make it turn left) the servo arm has lots of throw. However when the servo is pushing the steering link (to make it turn right) it seems to hit its max arc of swing and that's it.

I'll try to take some pics and post tonight. Also, I'm only running on the middle hole of the axial aluminum servo arm, maybe I should try the one furthest out.

Thanks guys, keep the ideas coming...

 

[pstar26]

I found my servo doing the same thing. Turned out to be fouling on the chassis cross member a little and the bolt for the steering link was just a little to long. After I trimmed it down to be flush with the rear of the servo horn and it was fixed. You might have probably already checked this tho.

 

[cincycrawln]

Yeah definitely furthest hole out. You're right, it has universals. Try clocking the servo horn so it doesn't hit max arc to the right. Or maybe a longer steering link instead of the ones in your kit

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[SynisteR6]

Here are the pics, it seems when turning right instead of pushingi the steering further it just lifts the link, as if its out of reach... have a look from the top at the difference. And yes, the horn is centered on the servo. Now that I looked at it in the pics it doesn't look that bad... but very noticable driving..



straight:


right:


left:

 

[cincycrawln]

Maybe try turning the horn more to the left when the servo is centered so you get more push to the right. Then you could adjust it back to straight with the trim

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[allanon1965]

You need a little longer rod from the servo to the right wheel..or straighten that a little bit...the one u have is not at the same angle as the panhard rod...i personally would bend it enough to be parallel with the panhard....that will help some. If its not enough get longer ends or a longer rod...its that simple

 

[Rockridge]

Your tierod should run parallel to the pan hard bar.... Get rid of that bent one and put in a straight to run parallel and that should help

 

[Squatchy]

Your tierod should run parallel to the pan hard bar.... Get rid of that bent one and put in a straight to run parallel and that should help

The first part of that statement is true, the second is not.

Straight or bent doesn't matter, the bar could be bent to look like a chicken and it would act the same as a straight bar assuming it's rigid.

As high above axle centerline as your servo is, try setting your servo horn one or two teeth the the right when looking front to back, or, to the "drivers" side. By setting it straight vertical you're POSSIBLY losing some steering throw to the right.

 

[SynisteR6]

Thanks guys, I'll try moving the horn tonight.

The RC4WD kit came with a straight link and a bent one, I thought the bent one looked nicer and as Squatchy said, it shouldn't make a difference what the shape is as long as the distance between the two connection points is the same.

 

[allanon1965]

thats just it, the distance will not be the same. if you take the bent one and measure between the holes in a straight line and get the measurement of say...2-3/4 inches. now if you straighten that rod and remeasure, it will now be longer between the holes...how much depends on how straight you make it. It DOES make a difference..in my example it is now 3 inches long. a gain of a 1/4 inch.

I am saying to straighten the bent one first, not replace it with a straight one as the straight one might be just the same length as the bent one when measured hole to hole. These kits sometimes need slight modifications to work as intended, due to differences in every ones setup...

 

[Scocrawler]

The pic was from rc4wd to show his cms kit. That's not his actual truck

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Ahh. Correct you are. But now that I see the actual truck it still looks off center. looks really bad viewed from the top. Anyway I would try to put a little bend in the panhard bar to shorten it up if you cant make a new one. Leave the Tierod the length it is (bent one or straight doesn't matter, imaginary line drawn through the mounting locations needs to be parallel, not the bars per say, and same length) and then you can clock the horn a tooth on your servo. Your steer ahead will be straight, axle will be centered, and have increased steering to the right. All should be good as long as you are not already maxed out turning left.

Another thought I had is disconnect the steering linkages and make sure there is no binding when turning right at the knuckles. If there is it could be the servo lifting the chassis instead of turning the wheels. Much more prevalent on vehicles with taller ride heights

Anyway, Good luck!