Frustrated RC guy with steering end points
 

Hey guys,
For weeks I've poured over threads regarding poor turning circle on full lock etc and been through all the checks and measuring suggested. I have the same problem on two different cars and think it must be me :rolleyes:. I have a LCG slash and a Mugen mbx7 running off a DX4s with AVC.

Both the Mugen and slash has terrible turning circles. I built my Mugen at the same time as my mate with all the same components except he has a DX3. We have Hi-tech 7955tg servos and Traxxas MXL-6 esc and 2200 motor (traxxas cos it's water proof).

When I turn full lock it doesn't turn all the way. I can manually force it further (when turned off) I've tried maxing out the end points and playing with the turnbuckles but to no avail. My mates turns on a dime and mine takes most 1.5 meters lol. I'm starting to think its my servo but it's only had about 10 packs through it at most.....

I went a good servo to prevent that kind of problem but I might have to man up and spend some more $$$$:mad:.

Any ideas before I go don that path???? And yes my slash does the same thing but it's only a SC so I'm not too stressed about it.

I don't really kow what AVC is precisely, but it sounds weird. Have you tried turning it off? Also, max out your dual rate (or whatever it's called in a Spektrum). If you can manually force more steering it's nothing mechanical or the servo, so that just leaves transmitter settings.

Airtronics have a VR Adjust function that recalibrates physical radio end points if they drift. Does the Spektrum offer a similar feature in one of the menus?

Aside from Monaco, have you ever seen a F1 car plow through a turn with the steering locked all the way over? Neither have I.

The 7955 is the best servo ever made. Unless someone programmed the wrong endpoints INSIDE the servo. Make sure it throws as much as your buds servo.

There's more to steering than the front wheel angles of the car. A Mugen should turn around in the width of an Rc track easy at slow speeds. You really shouldn't need full lock steering too often.

Set your end points with suspension level. Make sure your saver is tight. Hopefully no weird EPA nonsense hurt the servo.

Then:
Move steering links rearward on ackerman plate
Stand up the front shocks on the towers.
Thinner diff fluids
thinner shock oils
ride ht set properly?
Entering the turn at the proper slowed down speed?
shorten the rear camber links
increase or decrease caster, try more camber in the rear
slight toe out
proper tires?
move rear hubs rearward increasing wheelbase
try more rear droop, brake then turn.
make sure the traxxas ESC outputs enough voltage to the servo under load


How much lock is it missing? 1/4"? Try moving out on the servo arm for more throw maybe. Need pics.

We had some problem when we started out in RC. We didn't know the controller (Spektrum) went past 100% on the end points. Maybe your controller is the same?

I'm always checking my Dual Rate setting before I hit the track 'cause my thumb button/switch is located at a weird angle on "flimsy" FlySky radio. If I don't think about it when I lean over to pick up my ST, my thumb sometimes flips the sensitive dual rate's switch.

Yeh I've been right past 100% but to no avail. I still think there is a lot more to know about the DX4.... time for more playing lol

Good idea, I don't even know what switch adjusts it but it would be fair to say I've flicked something in my haste lol

AVC is cool little feature on the Spektrum, basicly a G sensor in the receiver that can assist in traction control and cornering on loose surfaces. Ill have a look for the D/R function on the controller and have a play. Thanks

Wowsa, you have given me a lot of testing to do thank you. The Buggy has barley been driven. It was awesome when I first put it together and turned great. I was using a Traxxas TQi until I saved enough $$$ for the DX4. I am a bit more familiar with the TQi than I am with the DX4, in truth I've only used the DX4 for about 2 hours in total. I'll start looking at it tonight and see how I go, if im still having problems ill take a few pics and vids and see what ya think. thanks.

Well for what I can tell spectrum dx4s does not have a duel rate function. I've reset all settings on the controller and nothing has changed. I've moved the steering arms back on the Ackerman plate and nothing. I don't want to go changing too much or the diff fluids shock oil etc as it was all sweat a few drives ago (pre the dx4).

I think I'll just have to live with it, I'll post a few pics tomorrow as a last ditch effort. Maybe I'm just chasing a ghost

Make sure you throw in a pic of the servo horn and link in the mugen. Try turning the travel up even if it goes past 100 and see if you gain anything, it goes up to 150.

Adjust the travel setting on your transmitter then you need to rebind and calibrate the receiver.

Spektrum calls it "steering rate". It is an override feature measured in percentage. If S/R is set to 25% your steering will only go 25% the distanced of steering EPA/Travel setting.

Here are some pics of manually turning the wheels to full lock and the other is when turned to full lock with the controller. It doesn't look like much but it make a massive difference to the turning circle. It seems to be mainly the inside wheel that is not turning as far???? what do ya think?

Attachment 1246964Attachment 1246965Attachment 1246963Attachment 1246966

Mark the servo horn relative to the case and see if it's turning the same amount when steered by the radio or manually. We can't tell by the pictures, so you're going to have to look at that yourself. EDIT: although looking again at the pics it seems like the servo has a limited steering (dual) rate.

It's either the steering rate as previously described, or just the kinematics of the linkages as they get to full lock. Around full lock the linkages lose stability as the tie rod begins to intersect the kingpin. It's hard for the servo to control at this point as there is no mechanical advantage. Hence, possibly you can turn the wheels farther by hand than the servo would if you're grabbing the tire. Nevertheless, if you have the same rig as your buddy (and built the same) and if this is happening on your other car, it seems to point towards radio settings. I recommend spending a little time in the manual to familiarize yourself with the radio.