Need for a panhard?

[Armistice]

Ok, I was having a small debate in another thread, but I don't want to totally derail it or cause an argument

Could someone explain the reasoning behind a panhard? I understand the principle of a panhard, but seems unnecessary to me (in an RC crawling application)

I've been told it's to locate the axle. That's great, but doesn't the 3/ 4-link locate the axle? Aside from slop in the rod ends, I can't see how anything would move far enough to cause problems

I have heard it's that in a high bind situation the servo will just shove the chassis/body around and not turn the tires. Trying to turn bound tires would prob lead to broken/ stripped gears. I'd rather have some give with the chassis moving than trying to turn bound tires (in that case, maybe stop trying to turn your tires and back out?)

It's to eliminate bumpsteer. Bumpsteer while racing at high speed= bad. Bumpsteer at crawling speed= too slow to matter in my opinion

I hope that what I've said makes sense. If someone is able to get a small video to show me, or maybe explain a little better, that would help

I have RC4WD's CMS on my Honcho, and have seen no problems while crawling

 

[Devil Inc]

I suppose if you're comping and going for scale points, yes run one. I run one in my trucks for realism, sometimes it helps create a bit of a challenge. With the RC4WD CMS, it's not a requirement, if you're using the stock Axial 3-link "Y" piece. Simply put, the front axle will remain centered because the upper links are connected to both sides of the chassis.

I don't see an issue with slow speed bumpsteer, just my opinion.

 

[Gen3_Teg_88]

it is mostly for true 3 link setups. with a traditional 3 link there is only the link going from the top of the axle to the skid plate/where ever you decide to mount it. what that means is that the axle just flops around side to side; so the panhard keeps the axle centered under the chassis. i dont really consider the axial "Y" upper link a 3 link because it acts similar to a 4 link(call it...3.5 link? lol) so it does not require a panhard.

 

[heavychevy]

adds more horsepower... everyone knows that

 

[Harley]

If you have a CMS then you need one for what I would consider acceptable performance.

Even when in low bind situations a CMS without a panhard will transfer force through the suspension instead of just the linkage.


Bump steer is still noticeable when crawling, even at trail speeds.

 

[Armistice]

it is mostly for true 3 link setups. with a traditional 3 link there is only the link going from the top of the axle to the skid plate/where ever you decide to mount it. what that means is that the axle just flops around side to side; so the panhard keeps the axle centered under the chassis. i dont really consider the axial "Y" upper link a 3 link because it acts similar to a 4 link(call it...3.5 link? lol) so it does not require a panhard.

I'm from a desert racing background, so it's a true 3-link to me, but that's beside the point, haha

It sounds that a "true" 3 link is just a single bar? Sounds odd as it would only locate the axle "pitch" I'll say (aeronautical term, lol)

Bump steer is still noticeable when crawling, even at trail speeds.

I'm not arguing with you, but even if noticable, I can't see it being a problem because speed is so slow

I guess that in the end, it's working for me, and that's ok

 

[Gen3_Teg_88]

I'm from a desert racing background, so it's a true 3-link to me, but that's beside the point, haha

It sounds that a "true" 3 link is just a single bar? Sounds odd as it would only locate the axle "pitch" I'll say (aeronautical term, lol)

touche, lol. im no professional in the real stuff, just the way i viewed it, lol. i guess it is technically one link. when i think of 3 link in RC crawling i think of one upper link keeping the "pitch" of the axle and one panhard keeping it center; though there are other ways of going about it.

like this.

 

[Armistice]

That looks stupid, haha. I'd agree a panhard would be needed in that situation

Thanks for the information everyone

Hmm, for scale looks, I wonder if a panhard could be made to act like a driveshaft. At least for me since I don't want to run a "true" panhard, I could still get the look with having one that slides within itself. It wouldn't be functional, just for asthetics... again, if I really wanted to have the scale look without functionality

 

[dittohead]

The pic above shows a 3 link with panhard well(well thats a watts link but its similar to a panhard), even though its a drag car rear suspension setup. Why a 3link with panhard works well on a steering axle with a frame mounted servo is because your draglink comes down at an angle to the knuckle (obviously). Now in a properly designed 3 link/panhard setup with the panhard matching the length and angle of the draglink, the steering stays consistent throughout the articulation of the suspension, eliminating binding and bumpsteer. I completely agree that this isnt the most important thing in the world in a r/c crawler, but i come from a 1:1 wheeling background and if you are building a truck with conventional steering (box on the frame) a properly designed 3 link/panhard is the best way to have a truck that will have any semblance of drivability at speed. Same thing applies to a r/c truck. On the other hand, a r/c truck with an axle mounted servo, which is fundamentally the same as full hydro steering in a 1:1 truck, you can use any link setup you wish since you dont have that mechanical steering link to contend with suspension movement.
In the other thread i wasnt trying to start any argument, the original posters picture showed a hand bros. CMS kit, which is a TRUE 3 link/panhard setup. His highsteer knuckles wont let the draglink play well with the panhard, causing bumpsteer and binding. You suggested removing his panhard bar, which obviously wont work. Your truck has a sort of mix with the stock scx10 upper Y link and a frame mounted servo. It works but its not ideal, and under heavy steering loads i bet that plastic Y link is flexing like crazy. But again its just a toy car so its not a huge deal and obviously it works

 

[indiana mudcat]

Bump steer doesn't only happen at speed. It also changes your steering endpoints. Drop the tire the draglink connects to and you won't get full steering, lift that same tire and you'll go past your set endpoints, possibly burning your servo out.

 

[Meatwad]

When you're in a precarious situation, bound up and all the servo is doing is raising or lowering your chassis... You will appreciate a panhard bar. True in some situations you can get away with not having one, but the chassis is rarely static or level to the ground in a crawling situation.

For rc crawling applications, the axial y link is still considered 4link. What's keeping your axle located under your chassis is that rod end on the end of the y link along with the rod ends at the other end. Essentially the binding of the rod ends is what's doing the work. A true 3link with panhard has one link from either side of the chassis as your top link and the panhard to keep the axle located.

 

[Grizzly4x4]

If you have bumpsteer it will show up during articulation and change your steering throw.
Imagine trying to make a right turn over a rock and every time your right tire goes up, the tires turn back to the left a little bit.

 

[Rook82]

SCX10 :: Movie.mp4 video by Markc1016 - Photobucket

That vid shows my SCX10 with a HB CMS. You can see as the suspension cycles up and down whether 1 side or both, the steering is not effected. The pan bar keeps the axle in the same relation to the steering linkage. The axle does move a bit left to right due to the arc of the linkage. But because the steering drag link (from servo to knuckle) follows the same path on articulation as the pan bar, the steering is not effected. Not sure if that makes sense or not?

 

[Armistice]

Wow, there's nothing. Not sure what else I expected, haha. Thanks for the video

I do agree with everyone's statements though. If I do change my mind, it's the last thing on my list

Maybe I'll put up a quick vid of how my CMS affects my steering later