Diff cases wiggling inside bulkheads on Summit

[fyrstormer]

With the stock servo-saver, 2x400oz-in wouldn't really do more than 1x425oz-in. Even with the stock servos my Summit's servo-saver unlocks when climbing over rocks.

[BlackIce05]

That makes sense, I've noticed the servo saver unlocking more frequently since I put that single servo on. Think I read somewhere about putting a washer on it, might have to try that.

[fyrstormer]

Yeah, shimming the spring will increase the force necessary to unlock the servo-saver. Basically the equivalent of tightening-down the spring collar on an adjustable servo-saver. Unfortunately, I don't know if the stock servo-saver mechanism can withstand more force; there's a top piece and bottom piece that bolt together to contain the servo-saver spring, and those two pieces get stretched apart really hard when the servo-saver unlocks and the spring compresses. Preloading the spring may exceed the load-limit of the top and bottom pieces, which are held together by screws driven into plastic.

[BlackIce05]

Good point, I've already replaced the top part with aluminum for fear the plastic wouldn't handle the higher torque very well, maybe I should look at replacing the other piece as well, and a shim, or maybe heavier spring?

[fyrstormer]

My general rule is "don't have aluminum scraping against aluminum." When I have to reinforce servo-savers, I make sure to leave one of the two mating parts plastic, because aluminum parts pressed together will grind each other to dust in short order -- if they don't weld to each other and get stuck. I would say, probably the best combination of aluminum and plastic parts for the Summit's servo saver is to replace the upper and lower parts with aluminum and keep the plastic lever that connects to the servo linkage. I haven't seen anything to indicate that the plastic lever is weak, especially if you have two servos connected so each arm of the lever is only handling half the load.

I'm not sure there are any stiffer springs available. If you find one, let me know. Shimming might be the only way to stiffen the servo-saver, but that's not really a bad thing, it's just more fiddly than dropping in a stiffer spring.