Just built TT02 Rally has bad wobble issue!

[jongrill]

Hey friends,

 

 

I just finished  building a TT02 Rally Subaru Impreza and was super excited to take it out for a run. I was sad to learn that I have a bad side to side wobble issue going on that I can’t figure out. It’s happening during straight line runs. I’m using the Tamiya aluminum servo horn, and all the Tamiya aluminum steering upgrades as well coupled to a Savox high torque servo.

I’m pretty new at building kits so any advice would be appreciated!

 

Thanks! 

 

[Juggular]

Something like this?  or worse?

https://imgur.com/tREAWvC

[jongrill]

Negative. The whole car wobbles and swerves while driving!

[Juggular]

[1]  You could take off the wheels.  Lift the car off the ground and run it to see if the shafts are wobbly.  Shafts wobbling would be very rare.  

[2]  Steer to see if the steering servo glitches.  (still no wheels)  Steer while running it too, sometimes ESC can cause a glitch in the servo.  

[3]  Check the play in the dog bones.  If they are metal and bent, then it could wobble.   

[4]  If 1, 2, 3 check out, then put the wheels back on and.  Run it off the ground to see if wheels are wobbly.  (you'd have seen it, if it was this easy)

[5]  If A-arms of the double wishbone suspension are not the right lengths, it could cause uneven rotation. (Phasing issue)  But that's hard to do for TT02 because the arm lengths should be the same. The front and the rear are nearly identical in TT02.  

 

[jongrill]

10 minutes ago, Juggular said:

[1]  You could take off the wheels.  Lift the car off the ground and run it to see if the shafts are wobbly.  Shafts wobbling would be very rare.  

[2]  Steer to see if the steering servo glitches.  (still no wheels)  Steer while running it too, sometimes ESC can cause a glitch in the servo.  

[3]  Check the play in the dog bones.  If they are metal and bent, then it could wobble.   

[4]  If 1, 2, 3 check out, then put the wheels back on and.  Run it off the ground to see if wheels are wobbly.  (you'd have seen it, if it was this easy)

[5]  If A-arms of the double wishbone suspension are not the right lengths, it could cause uneven rotation. (Phasing issue)  But that's hard to do for TT02 because the arm lengths should be the same. The front and the rear are nearly identical in TT02.  

 

I will try all these things and see what happens! 

[Kingfisher]

Do you have a gyro hooked up on it? 

[Jason1145]

Sounds like it could be two different problems if it’s 1) wobbling and 2) swerving.

I just built a Striker and used rear tyres that had a flat spot and that caused it to bounce down the road... but only that one issue of bouncing like mini hopping!

Your wobble, is it up and down or left to right and does it get more intense as the speed increase?

[Bromley]

Try pulling the steering servo plug out and see if it still moves side to side. If it tracks straight, it could be motor interference.

[jongrill]

5 hours ago, Kingfisher said:

Do you have a gyro hooked up on it? 

I do not. I just researched one. See below the quotes! 

1 hour ago, Jason1145 said:

Sounds like it could be two different problems if it’s 1) wobbling and 2) swerving.

I just built a Striker and used rear tyres that had a flat spot and that caused it to bounce down the road... but only that one issue of bouncing like mini hopping!

Your wobble, is it up and down or left to right and does it get more intense as the speed increase?

So the wobbling is side to side when the car is driving in a straight line. No flat spots on tires! 

56 minutes ago, Bromley said:

Try pulling the steering servo plug out and see if it still moves side to side. If it tracks straight, it could be motor interference.

I will look into this but:

 

So I think this is why is going on. Upon more observation - it is the servi that is wobbling while driving. This is my first time using a Savox digital servo and after doing some research it seems like what I need might be an external BEC. The stock Tamiya ESC that came with the car is the TBLE-02S which apparently does not have a powerful enough BEC or one at all. 

Of course - this is my first encounter with a BEC or a digital servo so I might completely wrong. Please tell me if I am! 

 

Quite honestly, I might pull this servo and go back to a regular one. Maybe I’ll save this super powerful servo for a CR01 build...

 

Thoughts and help is always appreciated! 

[Juggular]

Ah, Savox is known to be power-hungry.   

[svenb]

I have encountered this a few times, the digital servo not being compatible with the ESC. 

Swerving and self steering.

Last time I had this was when I used a Alturn servo and a TEU105 speed controller.