Turbo Optima limiter gear problem

[Coelacanth]

I was doing some ultra-low-speed house-driving tests with the Barney car last night and I'm having issues with the OT-74 limiter gear nut always coming loose. After a few seconds of forward/reverse just to test steering & the ESC, the car would stop moving forward or back while the motor just revved. Everything was tight, all the set screws threadlocked into place, but opening the gearbox revealed the limiter gear reverse-threaded gold-colored nut was spinning loose. It seemed to me going in reverse was causing this more than forward.

The nut is described in the Turbo Optima manual as being an "M3 nylon special nut", but I don't see any nylon inside any of the 3 OT-74 limiter gear assemblies I have. I also don't think it's a good idea to threadlock the nut on, because it's needed for the torque limiter to function properly. I also don't want to downgrade to the solid shaft variety of gear, which is what the original Optima/Javelin used. I don't think it's capable of handling high torque motors.

So, what are some suggested fixes for this issue? I don't recall people having lots of problems with their Turbo Optimas running the very-high-torque Le Mans 240 series of motors, and this carpet-driving at low speeds was a far cry from blasting around at full speed with a 240SB.

Thanks in advance.

[ROH73]

That nut has left hand threads, so in forward it will stay tight (as the limiter gear is rotating counter-clockwise). In reverse, especially if you have a high speed type reverse, it could loosen up. A dab of thread lock should help...and it shouldn't affect how the limiter works.

In addition, I've always found that the limiter needs be kept quite tight. It doesn't function as a modern slipper for controlling acceleration, etc, as there are no friction pads...it's basically just to deal with the stress on the gear train during jumps and such.

[jwscab]

not sure how large the nut is, but for applications where i need a locknut but none is available, I'll stake the nut. So basically, get a really pointy center punch and tap on the closest flat edge I can near the threads to distort the metal slightly, in usually 3 places. The other option is to slightly oval the nut to make it lock, some military fasteners have this feature on half the threads. If you put it in a vise and lightly squeeze, check fit, squeeze, check fit, etc until the desired friction is felt.

I do agree with ROH73 though in that that 'slipper' function is more or less a 'don't break anything' last resort, I'd make it pretty tight.

[Coelacanth]

Thanks guys. I did have it on pretty tight initially, and as ROH73 said, it was the reversing that seemed to loosen it. I wasn't really reversing hard either (not about to do that inside the house, of course!)...and the ESC is programmed to reverse at 50% speed. I might reprogram it down to 25%, which was the factory setting.

I wasn't sure if threadlocking it would be a wise idea, but it's true--it shouldn't loosen with forward driving, so I'll give it a dab.

[ROH73]

Yeah, 25% is probably a good reverse speed setting.

[Mad Racer]

I never had any trouble with mine when I bought mine. ( That was when i was 15 though)

I locked it up. I do remember that the Turbo Optima kit had a 9t pinion with the 240S and 8.4v battery pack that it was marketed for. That's a hell of a lot of starting torque. I still never had a problem.

Let us know how you go.

[Coelacanth]

I re-bolted it on with some thread-lock last night...you can tell the reverse-nut only goes on so far and then stops, so there's no point in really reefing on it. I didn't get around to reprogramming reverse on the ESC or testing it, yet...maybe next week as I'll be out of town this weekend.

I thought it odd that the manual doesn't specify to use thread-lock when it's obviously a requirement, and also that it mentions the nut is a nylon M3 nut. There's no nylon material on ANY of these limiter gears' reverse-nuts.