Berg / 300 / VP / RCI OTA

[Shorty40]

Hey guys

I remember seeing some comments in my forum surfing but can't seem to re-locate them with a search......

I have the 300s, VP Hi steer knuckles and RCI OTA steering setup. Knuckles are facing forward.

I had no problems with the setup......until recently. I modified the front end with wider hubs to gain some clearance between the steering arm and my tyres and also my tyres and springs at full lock.

The problem I have now is at full lock (on throttle) I get MASSIVE wheel shake. It wasn't there with the previous VP hubs (narrowest offset).

What's the story ? Is there a fix ? Or do I go back to the narrow offset hubs.

[4xFord]

I copied this from another thread for you.

Originally Posted by RcBro

Zero Ackerman and 50* of steering with 300's on my rig. Not sure how much you can possibly get !! SDS has got 55* lol. Insane! Ackerman in crawles if often looked at the same as a vehicle or off-road/on-road rc car, however crawlers can not be looked at in the same way.

If you have ackerman, either positive or negative, only one wheel will reach max steering angle, the other one will be less, always! With zero ackerman both wheels can go to max steering angle. Whats not taken into account is the addition of traction on the rocks, (AKA Scrub Radius) at zero the crawler steers easier. If your running regular knuckles and your tire with less steering has the most traction your crawler will almost always tend to follow this tire. Take into account a rig not running zero ackerman knuckles and digging up hill in high traction, the knuckle that is not maxxed almost always hops and slaps around causing negative and unpredictable results.

With zero ackerman whichever wheel has the best grip will be at max steering angle and the truck will seem to steer a little better in most situations, but also when digging you no longer have this slapping action which aids in predictable results as well as non broken parts. I first discovered this first hand when I initially built my berg and ran the RC innovations link with regular high steer knuckles. I snapped 2 300 pins from the slapping effect, mostly always on near vertical digs under throttle trying to move the rig left or right to get to a traction spot that I needed to continue the climb or clear a gate. After talking heavily with SDS he highly suggested trying zero ackerman knuckles which he told me would give me better steering and to eliminate this issue. I bought the knuckles and increased the width of the link and it truly was night and day. I got both things I wanted and needed badly.

I'm not trying to bash you or anyone, just trying to help inform. I have sat and watched SDS measure steering all day long to test his 300's in every situation and when it comes to steering I trust everything this man has said, but not only from his words, but it shows on the rocks as well.

On a great note, the rig is looking good, I want that chassis so bad, just don't want to touch my rig as its working so good, but I'm sure soon I'll add it to my arsenal. I too like a soft rig, however to soft and you find yourself in a hole and the rig just binds itself up to no end. Not sure what type of rock your crawling on in your area but we run alot of loose stacked rock and holes are a nightmare! Good to see I'm not the only one running a punk these days lol.

[Shorty40]

So I need zero Ackerman knuckles ?

But this steering kit was designed for the VP knuckles.

That sucks

[ram_tough]

If the CVD's are hitting their limits, you could turn down your EPAs.

[JeremyH]

Have you pulled apart the CVDs to see if they are damaged? Since you are getting more throw now, it could be that any damage wasnt noticable before.

[SMR 510RR]

I had the same problem. Check the CVD pins, mine were a bit fed up so I replaced them and made sure the slots were smooth. It helped out a ton. Also make sure that your knuckle bushings (the little top hat guys) fit well in your kuckles. If there is slop there then it really contributes to this problem, locktite the screws tight also...Once mine loosen up the front right tire goes crazy.

[Shorty40]

The CVDs are almost new.

I don't get the wheel shudder/shake with the narrowest hubs on the SLWs. Only when I put the wider hubs on.

[SMR 510RR]

Originally Posted by Shorty40

The CVDs are almost new.

I don't get the wheel shudder/shake with the narrowest hubs on the SLWs. Only when I put the wider hubs on.

Interestingly that is when I was having the problem as well. Havent tried my new dh's yet (stupid rain) but i think they will be better. I was way wide though with .7 SLWs. For me making sure everything was tight and backing off a couple clicks on the steering endpoints solved my problems 95%.

Is there any wobble in your knuckles? Can you shake them at all?

[Shorty40]

I took the knuckles off and cleaned the CVDs.

They rotate smoother in hand. But I put them in the axle and power it up and they grind and vibrate. And I don't think I am near maximum angle of the CVD.

I tried to disassemble them but I can't get the ring off. The grooves for the pin appear to be clean and clear (I WD40'd the crap out of them).

Think maybe buggered CVDs ??? But they are practically new.

EDIT - It is doing this no matter which hubs I use. So it isn't the OTA steering, the hubs or the knuckles. I am confident it is an issue with the CVDs.

[romulus22]

Do you have a bent axle tube or is the actual axle shaft bent?

[Shorty40]

Pretty sure neither are bent as they run true with the wheels at straight ahead. The vibration appears from about half lock and increases as the lock increases.

[SMR 510RR]

Can you make a quick video of what it is doing. I am almost positive that you are having the same problem that I had. If so I can give you some other advice.

Is it like this:

[Shorty40]

Way more violent than that !

Trying to upload a short vid now

[Shorty40]

[SMR 510RR]

I think your just looks worse because you were spinning them faster. Here is what helped mine.

Making sure the knuckles had no play on the bushings and the screws are always tight.
Putting 2 orings around the balls in the ball ends to add some resistance.
Moved the tie rod to the closest hole to the knuckle mounting hole.

After all that my problem was solved. The problem happens because of the angles in the steering linkage. When the steering is at the lock the inside knuckle (Worse on the right side) is turned so far that the tie rod can pivot and move that knuckle because the knuckle follows closely enough to the arc that the tie rod is on. The shorter the link is from the servo to the tie rod the less you will notice this issue and adding the o-rings quiets down the movement. Any extra slop in the knuckle bushings allows the knuckle to flex outward or inward allowing the angle to change as the tie rod swings.