T4.1 terrible turning radius!

[sbsyncro]

Hey guys,

I just finished building a T4.1 from parts I acquired. Part of my build was to add new RPM front A-Arms. Once I put it all together I took it down to the track today just for a quick spin and I was SHOCKED at how bad the turning radius is! I have to wonder if maybe I set something up wrong, or if these just typically don't turn-in very well. Just for testing I have the camber and toe set pretty much at zero just as a starting point. My son and I frequently run around a small outdoor track with our Rustler, Stampede, RC18T, and Slash with no problems, but the RC10T4.1 can't make it around most of the sharp turns unless I push the back end around by spinning the wheels…

I set the camber and toe link lengths according to the manual (and incidentally, they were sitting in the box of parts already within a few mm of spec, so I'm pretty confident I have that right).

Any ideas? Could a wimpy servo cause this? Even at slow speeds, it can't make a hairpin turn on a regular 1:10 track… I love the way it handles otherwise - so low and stable compared to the Slash. I wanted to put a brushless combo in it, but if the RC10T4 steers like this, I might not want to make the investment….

[RC10th]

Is anything in the steering binding? Possibly over tightened the two steering rack screws? If the servo saver nut threads in the bellcrank are stripped the rack will bind due to the spring forcing the nut to bind on the top plate.

Pop the steering link ball cups off from the ballstuds on the steering rack and the ball stud from the servo arm off. Does the rack move freely on its own? Do each of the wheels turn side to side freely?

Also check that the servo performance is good without anything attached to it. I've seen some horns actually bottom out on the servo case when tightened down causing the servo to bind.


Failing all those things it could be a set up issue.

[sbsyncro]

Is anything in the steering binding? Possibly over tightened the two steering rack screws? If the servo saver nut threads in the bellcrank are stripped the rack will bind due to the spring forcing the nut to bind on the top plate.

Pop the steering link ball cups off from the ballstuds on the steering rack and the ball stud from the servo arm off. Does the rack move freely on its own? Do each of the wheels turn side to side freely?

Also check that the servo performance is good without anything attached to it. I've seen some horns actually bottom out on the servo case when tightened down causing the servo to bind.


Failing all those things it could be a set up issue.

Thanks. When you say "two steering rack screws" do you mean these?

If so, I didn't have to assemble that part but I'll go back and check it.

Going back through my setup, it looks like I have the front camber posts set up on washers, which sounds like it "deadens" the steering. I also inadvertently put the steering servo horn on at 12:00 instead of one-spline off, which meant I had to correct for that using the toe links (need to fix that), which probably isn't helping either.

How does one check servo performance (other than simply verifying that it works)?

Thanks again!

[RC10th]

Yes, those are the screws. If they are too tight the rack will be stiff to turn ( same if the servo saver nut strips).

With the servo disconnected from any steering linkage apply a bit of pressure to the servo horn while turning the wheel. Does it stall without much pressure or does it feel like it has ample torque?

Edit: Something else to check would be the "Dual Rate" or the "EPA" adjustments on the transmitter. Turn them to max or high as if they are turned down could cause similar symptoms.

[sbsyncro]

Well I think I figured it out today after going through everything. I put in a slightly better airtronics servo and set the horn one spline clockwise. There was also a hairline crack in the steering horn that was only visible while at the far end of the servo travel in either direction when it would flex open. I scrounged up a replacement and it seems much, much better now. Need to take it on the track to be sure.

One other thing I'm struggling with is setting the toe-in. The front end seems so wobbly that it is very hard to eyeball. What tricks do people use to set the toe other than just eyeballing it?

[RC10th]

I just eyeball it with about 1* toe out and about -2* camber. You can get fancy with set up stations etc but in offroad close is good enough. Adjusting camber affects toe slightly and vica versa.

I set my camber first with a camber gauge on the left with left wheel straight ahead, then set the right side with the right wheel straight. Set the toe then go back and make final camber ajustments.

[sbsyncro]

Thanks!

[Chris00gt]

You might have to adjust your controller to allow the servo to turn more. I had to adjust my Spektrum DX3R pro to 120% travel so it would turn the whole range. One other trick you can do is glue your servo save to make the steering feel more accurate.