Do you go to the Bellis Fair Mall?

yep:)

They roxors. There is getting to be a nice selection of Zip-Zap stuff there. I seen Jeeps and audi and all of those yum yum things.

Well, I think I have narrowed down the steering problem..

It seems that of the 3 ZZ SEs I have bought and returned that the problem stems from the steering sensor pot..

The ones on the are total junk.. They have HUGE dead spots as you turn them through their range, going from like 1k ohms to zero ohms then back up to 900 ohms...

Basically, the feedback to the sensor is what is making this cars act crazy..

I am trying to find a place to buy precision minipots to replace these with but having come up with anything yet unfortunately.

Rob

What is the total range of these pots? I have many micro pots layin around. I may be able to try this and see what happens. A 1k pot is close if it maxed out around 900ohms.

no, they are unfortunately 10k pots..

I'll look through my stash. I've got em up to the meg range. Might be something in there to test with. I've got a crippled SE lyin around with a busted knuckle that would make a good victim. I might do some tinkering.

More findings and I like it!!
 

Well, I broke down and bought my first ZZ SE yesterday. I got the gray/silver Audi TT. I got it home and found it had all the steering problems. I got about 5 to the right and 1 to the left and the center chattering was absolutely obnoxious. I almost took it back because it was sooo bad, but I couldn't resist the need to tinker with it and I'm glad I did. I started to experiment with the mod to the wiring/feedback resistor in the car (steering fix on the other forum). Here are my findings. Please pardon as I do not have a camera for photos, but will do my best to explain.

In the "other forum" they talk about the bridge between the center pin/blue wire and the passenger side pin/green wire. To breifly sum up, you remove the blue wire and break the bridge between the pins and recenter the servo. Well, it looks like RS is now putting the blue and green wire on the center pin and no bridge between the two pins. Electrically, this is the same result. From my experience with servos, typically the pot is wired for three wires, a left, right and center. This is for proper feedback of the servo positioning. The pot has to be at an electrical center, meaning the resistance value between the left and center pin equal the resistance value between the right and center pin. When you are turning left or right, resistance will increase on one side and decrease on the other proportionally. With the kunkles and the steering bar removed, I adjusted the steering screw on the car which actually turns the pot and adjusts the resistance values between the pins. I found the electrical center of pot to start with. It does not have to be exact, just as close as you can get it. The appearance of the pot was the center pin being towards the top, instead of being over to the driver's side. Then I soldered the green wire to the passenger side pin and the blue to the center pin. Remember that the pot on mine does not have the solder bridge between those two pins. When I turned on the car and TX, the servo centered it self and I found that all the chatter was gone and I actually had smooth proportional steering in either direction. It might have been a little steppy but far better that what it was stock. Also, the actual travel of the servo is greater than what the steering bar allows. I did shave the tiniest bit on the bar to allow a little bit more travel to the left and right. That's when I also noticed that the bar actually stops the servo, which puts a small load on the servo motor, instead of the servo reaching a stop point on it's own at the exact point of the bar hitting the stopping point. More ideas on how to fix this down below. When I put everything back together, I had much sharper turns to the left and right and solid, smooth control over the steering. Steering overall was very equal. The steering is more sensitive but I like that and it's too be expected I think when the servo is working the way it's suppose to in such a small car. It feels like some of my other cars now, epoch/drr's only smaller.

There is a little bit of a centering issue, but this is actually due to the transmitter. The transmitter does not come back to an exact electrical center, so it does require a little bit of steering to straighten out. To me, it seems pretty minimal. It does feel like there is a little to much friction on the wheel and this is keeping it from returning to a solid center point. I think the springs are doing their job, but do to some sort of tight fit of the wheel itself, the springs can't get the wheel back to center. My next step is take the controller apart and see if I can solve this issue. I've seen people talk about the possibility of changing the resistor value on the transmitter to decrease the sensitivity, but actually, it would be fairly simple to put in a parrallel pot to use as a travel volume adjust instead (steering rate like on the xmod or other higher end RC's). This would allow you to further dial in the rate of the servo so you could actually get an end point that would equal the travel of the bar and this would take the load off of the motor and probably allow for a little bit better performance.

I really just wanted to further add info to the fix found on the "other forum" so everyone could have a deeper understanding of not only how to fix the issue, but what the fix was actually doing. I hope this helps everyone and I didn't confuse anyone. Feel free to ask questions.

Now I'm really liking the SE alot. I had no problems on my more technical track with it. Stock to me was terrible, for a 5 year old, it's fine, but for all us who demand the utmost perfomance from our cars, it's worth tinkering with. With the success I've had, now I'm thinking about buying another one and not worrying about whether or not the steering will be good out of the box because i can fix it the way I want.

Interesting stuff! I'm printing this out so I can try it myself. I've read about this fix but was a bit dubious about trying it. I think I'll give it a go. I never understood why the SEs were made this way to begin with. Soldering the pins together seems to have been a last minute fix for something, but what is beyond me. I'd lay odds that new models will address this problem in the future, as RS seems to rush whattever they have to market bugs and all and slips in improvements as the shelves empty. Your results seem to be similar to what others have gotten and I'm now curious as to the extent of improvement to the steering. Thanks for the info!

Azimov,
I'm really happy with it. If you decide to trim the steering bar for further throw, be very careful. If you shave off to much the wheels could turn to far in to where they hit the car and won't roll. I don't think it's absolutely necessary to do it, but i wanted to try it. My turn raidius is about the same as my bits and regular ZZ, maybe 5 to 6 inches. With the bar in place, you can see where it hits the wheel mounts for the stop positions and this should give you an idea of little to shave, if any at all.

Once I play with the transmitter, I'll post my findings on that too. I think replacing both pots with better quality pots could result in even smoother control, but I don't know if it's really necessary in this small of a scale. If you have any questions, e-mail me. I'm in my hotmail constantly during the day at work. Like I said, there is a little bit of stepping in the steering still, due to the quality of the pots in the transmitter and the servo, but it's not as noticeable as before the mod. I think I counted about 8 to 9 on each side but it was subtle, this is before the bar is in place. With the bar in place it's like 6 to 7. I'd say getting even 5 to each side and no chattering is worth it. I think results will vary based on the pots. Good luck. I hope you have the same results.

OOOPS!!!
 

Azimov,
I forgot to include my e-mail addy. Sorry.
cool_guitars@hotmail.com

later!

More stuff
 

I bought a Savanna lastnight and the steering on it was actually quite good compared to the Audi TT before the mod/steering fix. The stuttering was still there, but not as much and I actually had about 4 steps to the left and 5 to the right. So I opened it up to see what the difference was between it and the Audi.

This one had the pot centered, was wired with green on the passenger side pin, blue/center, yellow on the other pin. This one had the bridge or jumper between the green and blue pin. So, I'm thinking that most of the steering issues is the actual placement of the pot. If you don't want to or don't feel comfortable soldering, another fix may be to just remove the wheels and steering bar, center the pot, turn on the car/TX to allow the servo to center, and then put things back together and ensure that everything is working ok. You will still have the stuttering, but IF I'm right (RS keeps us guessing) the stuttering should not be as severe and you should have 4 to 5 steps in either direction. Infact on the Savanna, you couldn't even see the wheels move when it was stuttering to center, the Audi shook severely.

I guess the question is, which one of the wiring configurations is the new one and the old one. Hopefully it's the configuration on the Savanna and overtime the old one's will get phased out.

Because I like the way the car drives without the stuttering, I did mod the Savanna. All I had to do was cut the bridge, removed the wheels and steering bar, turned on the car/TX and allowed the servo to center, trimmed the steering bar for further throw and reassembled. It drives exactly like the Audi does now.

I tried to take the TX apart lastnight too, but it didn't want to come apart, so I quit on that. I'm going to do some other experiments with adding parallel resistance to the servo pot to see if that might take out the sensitivity. Based on what I've seen so far and the way the steering reacts depending on the placement on the pot, this MIGHT be the missing link. Later!

This is a question that I still had about this mod. It has been reported that the pot in the car is very cheap and has dead spots in it. This lead me to believe that replacing it would get better results. But, since the rearranging of wires and recentering of the pot has produced good results, I'm unsure at this point. I have many pots in different ranges, but none of them have the proper length and diameter of shaft to simply pop one in to replace the stock pot in the car. I could order replacements with the right size and shape, but am unsure if it's needed. Please keep us posted if you see a dramatic difference in performance by replacing the pot altogether. And, thanks for posting your results thus far.

I agree about the quality
 

Azimov,
I agree, I'm not sure the quality of the pots seem to be the issue either now, but rather the value of the pot. 10kohm variable resistor is a common, easy to find value. Makes sense that RS would use a common value, easy sourcing and cheap. What I'm thinking though is that the value is a little too large and with the fix makes it too sensitive. They probably realised it too so they tried to "fix" it. When the pot is wired stock and depending on where the pot is positioned, it's almost like they're trying to fake a smaller value, maybe around the 5K range. The blue and green wires tied together cause the stuttering in the center, basically causing the servo to hunt for a moment due to the small variance in the return of the steering wheel. I'm thinking if I dropped the value to a halfway point, say roughly 7k to 8K, it might sill have a good throw on the servo but not be so sensitive in the center and the stuttering would still be gone as blue and green are still separated. The other thing I noticed about this fix/mod is that to reach full left or right, the steering wheel has to only be turned about half way. In stock setup, it's almost full throw of the steering wheel in relation to full left or right turn of the car. That does make the steps more noticeable too. This is all just theory though until I can test it further. Hopefully this weekend.

Although I'm happy with the way my cars drive, I'm curious to see if a mod can be reached that would provide a good result that everyone would like.
1. elimination of the stuttering
2. equal steering to both sides
3. reduce the sensitivity a bit with better centering

RS may or may not ever reach this and why should they. They have to pay people to find a solution and then fix or replace/phase out thousands and thousands of cars plus change prodution. That's alot of money. Plus, it's a $25.00 car and like I said before, for a child, it's fine.

I can understand if someone has a car that is stock with a little stuttering in the center and equal turning (Basically a good car). Why fix it? I almost thought that about the Savanna too. But curiosity got the best of me on that one. My point is, what if no one thought of the dual cell mod, the fet mod or all of the other mods for the cars? We may be on the brink of a nice break through mod for the SE or maybe not. I really like the car and I can see some excellent potential with it. The fet mod is something I'm also considering with these. Anyway, I appologize though for the length of my posts. It's just alot of ideas I'm trying to share and hopefully it'll help someone with a bad car.

Azimov,
Have you looked at your cars, just to see how they were wired, maybe at least comparing the better ones to the bad ones? I'm just curious to see if you've found the same situation as I found between the Savanna and the Audi. Or anyone for that matter? It would help with us trying to determine the bad from the good and the solutions one can take on these. Well, I'll check back in couple of days, hopefully with more results. Later all

I guess I must be one of the lucky ones. I bought an Audi SE (my first ZZ) and right out of the box, It's run straight as an arrow with no stuttering whatsoever. Even after I performed a wheel mod, the thing still runs sweet.