steering linkage design issue

[xlDooM]

I love my amp. However, one thing that just annoys me is that it turns left better than right. When you're making a lowish speed turn on a high grip surface, the turning circle is just massively better for a left turn. This can not be fixed with trim or an upgraded servo as far as I can tell. The problem is that the part of the servo horn that goes over the servo's outer drive gear collides with the underside of the steering arm, effectively stopping the rack from turning further.

I might take a file to the bottom edge of the steering arm, unless someone has a better idea?

 

[X]

I believe I've noticed this as well. I'll take a look at mine and see if I can come up with anything.

 

[xlDooM]

After looking at it more closely, I don't think the problem is that the steering arm hits the servo horn. When you move it with unloaded wheels, it has about the same lock on right turns as on left turns. What does happen though, is that the servo horn twists a LOT. I'm thinking because the linkage is "folded up" on that side, the whole assembly loses a lot of torque. With the less than stellar stock servo this results in weak steering in right turns, ok steering on left turns.

That said, changing the linkage so that the steering arm and the servo horn no longer collide may bring relief to this issue, by giving more lock on that side than the other, offsetting the mechanical weakness. I figured if you put a little spacer (something like 1mm) between the servo mounting blocks and the vertical bulkhead they screw to, it should be fixed. The stock servo has a little bit of room in the chassis to move backwards. I will try this mod one of these days and update again.

I will also buy the next-crummies servo on my list, after the fiasco that was the mg996r. Bring on the power hd 1501mg!

 

[xlDooM]

So, I fixed it.

Here's the problem:

You can clearly see how on full right lock, the horn and the bottom of the steering arm collide, making it impossible for the servo to move over further.

This is the steering arm (still attached to the front cage of the chassis). As you can see it is fairly sturdy and it wouldn't hurt to take off some material.

So I took a cutter to it and took off a good chunk:


The issue is now gone, there is come clearance between the two parts at full right lock:


I tested it on my lawn and the difference was immediately clear. I can now do figure-eight tracks either direction around the jump, as it should be.

 

[X]

Nice work! Thanks for figuring this out.

 

[Vivendus]

Damn good work detective... but seriously what a design flaw.

 

[WoodiE]

Great info, I've copied the fix into a new thread and stickied it!