Steering Issues

[SMR 510RR]

Hey everyone,
So I recently redid the steering on my berg, basically 86 jeep style but clocked 20 deg. I added the RCbros ZA enlarged bearing knuckels to replace my old vanquish berg knuckles. I also took apart the super 300's and cleaned up all the surfaces inside the slots because they were getting a bit rough. Then I made a new mount for my new 7950TH (powered directly from CC BEC @ 7.2v, 7.4v was glitchy) to stand it up more than my old cs-170 was to get the horn out of the way while approaching rocks. Of course standing it up meant I would have to grind more out of the tube so the servo basically sits maybe .025" away from the super 300's shaft and it is literally touching my front motor.

Now onto my problem, when I first run the truck everything is great. Steering angle is ridiculous and the servo has no problem controlling the tires no matter how far I have them turned. Then after 5-10 minutes of running it I start to lose authority over the front wheels and the servo gets super hot to the point that if I touch the metal part of the case I cant hold my finger on it at all. When turn left everything is good but when turning right the tires end up turning back and forth maybe 1/4 inch.

Originally I thought it was a burr in the slot of the super 300's causing it but I disconnected my servo from power and turned the wheels by hand and everything was ok until I put a load on the wheels. I guess it still could be a burr in one of the slots and I will pull them out again and check but I think it could also be something else going on.

Here is a pic of my setup, any help or suggestions are appreciated. I would really like to practice for an hour or so at a time without having to worry about burning up my new servo, the motors and esc's are not even warm when the servo is on fire.

[TANK]

take your wheels off and set your end points on your servo. If you're pinning your servo to one side or the other during a run its going to heat up. But my guess is your end points are beyond the degree your 300's and your wheels and tires will let it go.


but I really don't know what I'm talking about, just my opinion.


also from you pic you need to fix your toe angle. the point of zero ack, is to have the tires even when turning, and having the toe out like that defeats that purpose. but like I said, what do i know.

[gunnar]

I was having the same problem too, switching to a front mounted tierod seems to be more efficient. Your setup is fairly close to what I had.

You can see everything is more in line with the servo horn, and I have noticed much cooler temps and stronger steering power. Even with a 5/16" diameter, the tierod only sticks out beyond the axle housing around 1/8" when the wheels are straight. Using a 1/4" tierod will give a bit more clearance:




The damage you see by the servo sticker was from my old setup, the new tierod uses less servo throw, and a shorter Robi horn too.

The draglink stays right on top of the tierod throughout the whole travel cycle.

[SMR 510RR]

Thanks for the replies guys. I took everything apart and turned the knuckles by hand while spinning them with the front motor to find the limit of the 300's. I did this for both directions and marked it with a pen, then put everything back together and checked how my endpoints lined up with the marks. Basically I had a little extra room that I wasnt using so that isnt the problem.

While I was turning them by hand I did notice that turning the left knuckle to the right was binding so I am going to try and figure out what the deal with that is, feels like the hinge point of the knuckle and axle hinge are off a little bit but only when turning right. One of the mounting holes stripped so I helicoiled it, it might not be perfectly centered although I doubt it would be off far enough to make that big of a difference.

Oh yea I know my toe was a little off, I just rigged that up to do some testing before bending up a new tierod.

Gunnar, I may have to try something like that out. It looks like you have a bunch of caster going on there, are those axles clocked 20 or more?

What do you guys think about running the draglink all the way to one of the knuckles with them pointed rearward? I think maybe the longer drag link would minimize the effects of the servo horn and knuckle rotating opposite directions if that makes sense.

[gunnar]

Originally Posted by SMR 510RR

...It looks like you have a bunch of caster going on there, are those axles clocked 20 or more?...

Axle tubes are clocked 30, then the axle is mounted up 10 degrees.
The bad part is the link mounts are too low, I still have to make raised link mounts to work better, sort of like what the Droid chassis uses, but tilted slighty.

You can just see the bottom of the lower left link in the top picture.

[RcBro]

Just want to make sure you have berg specific axles on your 300's and not axial specific correct?

[Cycleeric]

I agree with Gunnar

Move the tierod out front, reverse the knuckles and run a little toe in to increase your turn angle. If the servo isnt centered properly it could se an exxcessive load trying to keep itself centered or check your radio to make sure the trim isnt turned way up so you're not really centered. Just make sure everything move smooth throughout the range of motion

[SMR 510RR]

Originally Posted by RcBro

Just want to make sure you have berg specific axles on your 300's and not axial specific correct?

Yea that is correct. Like I said in the OP everything is great until the servo gets super hot and doesnt want to hold the tie rod straight anymore. Also I can hold the tie rod straight by hand as long as there is no load on the tires.

I will try the tie rod out front and report back after I test it out. It does make sense because if they rotate the same direction you get 1:1 movement assuming that the horn and knuckle are the same length but with them going opposite directions it gets all screwy since the drag link is angled all crazy and the servo does have to work much harder to hold everything solid.

[SkaldidDog]

Originally Posted by SMR 510RR

While I was turning them by hand I did notice that turning the left knuckle to the right was binding so I am going to try and figure out what the deal with that is, feels like the hinge point of the knuckle and axle hinge are off a little bit but only when turning right. One of the mounting holes stripped so I helicoiled it, it might not be perfectly centered although I doubt it would be off far enough to make that big of a difference.

Make sure the stubs are seated all the way into the knuckes. You can gently tap the margin of the CVD cup to seat them all the way. Sometimes my knuckles have a tight spot and this usually corrects it. Just cranking down the lugnut does not always work.

[SMR 510RR]

Ok, so I moved everything out front and tried that out...It got worse, at least the amount of deflection in the steering did. I know for a fact that I should have more angle, the tires arent even in the shocks yet when it starts to wiggle back and forth.

Im beginning to think that I just need some new 300's, as much as I dont want to throw out the coin for a fresh set I really dont feel like banging my head against this wall every time I try to drive this rig. I took apart one of the 300's and I can see that there is some heavy wear between 20* right and left, its all dished out probably .01-.015" and I think that is what is causing the issues.

Take a look, I managed to snap a couple pictures of it. Check out the right side compared to the left side, the right side is the side the pin rides on when the truck is going forward.





I am interested to hear what you guys think. I bought these in a set of axles so I have no idea how old they are or how the guy before me took care of them. I have had this issue since I got them and I really need to get to the bottom of it.

[Cycleeric]

Send a PM to SDS and see what they think about the looks of the pivot and if they have an idea on what may be causing your problems

[RcBro]

You can see the edges have rounded. I had a set that did this, but it came from breaking a pin and still running the rig. It chowder it pretty good, but I filed the curls off back to smooth. Used lots of lube and it didn't affect my permance, although I did begin breaking pins on the same side. I ended up purchasing a new set and have these in my other berg.

Can you simply suspend the rig and turn your servo left to right over and over. Does it still get hot without the tires spinning? With how fast your servo is getting hot from what your saying, I'd be more inclined to think the board on your servo is toast.

[Aggie01]

I agree with RC Bro, disconnect your tie rod from the servo and see if it gets hot. If so you know you need to send it to Hitec

[4xFord]

Originally Posted by RcBro

Used lots of lube and it didn't affect my permance

Originally Posted by Aggie01

I agree with RC Bro

[jlsandkes]

Originally Posted by RcBro

Just want to make sure you have berg specific axles on your 300's and not axial specific correct?

How can I tell which version 300's I have? I have a set I purchased a while ago and I am finally going use them but I can't remember which version of knuckles they were suppose to be used with.



.

[SMR 510RR]

Again, thank for everyones help.

Ok, I have my servo going back and forth right now on my servo tester. We will see if it gets hot. Its been on there for a couple minutes and it is cold as ice so far so I dont think that is the problem.

Just in case I took some axial knuckles and threw them on there just to make sure I am not an idiot running the wrong knuckles. It was way worse so I know that isnt the problem.

Now here is a question for you guys, should it be hard for me to hold the tie rod (without the servo attached) so the wheels are turned while they are spinning? Right now there is quite a bit of resistance trying to straighten them out, that is what I think the problem is. I already filed the slots as straight as I could and that didnt help much. Also while turned and driving forward my front motor slows when it reaches the tough spot.

[RcBro]

No it shouldn't be hard to hold manually.

[SMR 510RR]

I ended up taking everything back apart and cleaning the slots up a bit more. Lubed and reassembled and tried it out and it is way better. It isnt perfect but it is good enough to drive. Ran a pack through it (15 min or so) and the servo was warm but not hot, should do for now.

I think I will invest in some new 300's to freshen up the front axle, I can throw the old ones in the backup rig I am accumulating parts for.

Thanks everyone for your help, BTW RcBro I am loving your enlarged bearing knuckles!

[RcBro]

Right on, glad you got it figured out. Enjoy the knuckles!