Help understanding servo and servo saver

[Fdnavy]

ok my sons amp burned up the servo. One minute it was working the next minute the steering gave out and after that smoke came from the servo. I just ordered a JX Servo PDI-6113MG with metal gears and I have a few questions. First off how hard is this to install. I don’t see any YouTube videos or other instructions out there. Next I see people talking about installing the rpm servo saver eliminator bellcrank. Is that the same as a servo saver? Or is it instead of a servo saver? Do I need this? Do I need that and a servo saver? If so what exactly do I need? What other parts should I replace while I am doing this? I really want the car to run more than a few times before it breaks down again. We haven’t had much luck.

 

[xlDooM]

The servo saver is basically a steering bellcrank that bends when too much force is applied on it. This stops excessive forces on the wheels (e.g. when crashing) from stripping the gears in your servo. It also means the car can not steer hard at speed. The "servo saver eliminator" is a solid bellcrank that does not bend. It makes the car steer much sharper, but it transfers all collision and impact forces to the servo as well, so you must have a servo with metal gears. Since you have a metal geared servo, you might want to get the servo saver eliminator, or you can attempt to sabotage the servo saver so it no longer bends. You can zip tie the U-shaped spring to make it much more rigid, but the zip tie tends to slide off so you need to secure it in place somehow. It should become clear when you take the bellcrank off.

Replacing the servo is easy. I don't recall the details, but the servo is attached with two blocks that bolt to the chassis floor. First you unbolt the blocks from the floor, then you unbolt them from the servo, bolt them onto the new servo, bolt them onto the chassis. Be sure you get the servo horn on it with the correct spline count, you get differently splined servo horns with the amp in a little bag of spare parts (the spline count is engraved in the plastic of the horn). Look up the spline count in your new servo's data sheet.

 

[Fdnavy]

Thanks that helps. Hopefully I can buy replacement servo horns, I have no idea where the spares went. I don’t remember seeing them. Would an aluminum horn be better? The Data sheet says 25t I am assuming that’s the spline count. Is there anything specific to look for when buying the servo horn other than the spline count?

 

[X]

Would an aluminum horn be better? The Data sheet says 25t I am assuming that’s the spline count. Is there anything specific to look for when buying the servo horn other than the spline count?

If you get a servo saver eliminator I would stick with a plastic servo arm. That way the servo arm can act as your weak part in the system, keeping your servo safer.

Yes, your new servo is a 25 tooth. Just look for a servo arm with 25T and something that looks similar in size to stock and you'll be fine.

 

[Fdnavy]

Thanks for your help. I can’t seem to find just the plastic Servo horns. They sell a complete Servo saver kit. In the picture it looks like it includes the Servo horns. Is this correct?

 

[X]

For $7 that's not a bad way to go, but it only has one servo horn you can use. I suppose it gives you alot of spare parts too.

Other option is to buy a set of 25T horns, but it looks like those tend to cost $15-20. It's not a bad thing to have a few extra as they will be your sacrificial part in the system.

https://www.amainhobbies.com/mikado...-arm-25t-futaba-savox-protek-mik04021/p298148

 

[Biz73]

Isn't the stock servo 25t? If so, you just use the servo horn that's attached to your stock servo.

 

[Fdnavy]

I’m not sure I will check once I take it apart. I will probably buy those spares. Can’t hurt to have them on hand. Thanks for all the help. Until the next breakdown!