Senton steering servo SPMS651 upgrade

[ramack]

This is for my son's 4x4 Senton 3s BLX, looking for what to upgrade/replace since the steering servo is shot. How to you guys know what to cross-reference in finding a alternative servo? This RC hasn't had much usage, he bought it last December, probably has less the 8 hrs on it. The drive motor has already been warrantied and replaced by Horizon. Just put the motor back in and the steering servo puked.

I've found this on youtube/amazon:
https://www.amazon.com/ZOSKAY-Water...3068aab8dae6b389e1911f9d4e07ce&language=en_US

What's a good replacement for this servo?
Thanks,

 

[morrjr71]

That is a 25 tooth spline, and the stock servo is a 23 tooth spline. You will not be able to use the servo saver that comes with your vehicle. Others here with more experience can tell you what is needed for a 25 tooth splined servo to work with your vehicle.

 

[ramack]

Thanks Morr. This replacement is also labeled as a digital servo, is that a compatible replacement?

 

[morrjr71]

That servo will work just fine once you figure out the servo saver or servo arm issue. Do a search on the forum for "replacement servos" and you should find where folks have replaced a 23T servo with a 25T servo. It does require some modification to make it work. If you aren't comfortable with modifying your vehicle to accommodate a 25T servo you can also go with a stronger Spektrum servo, most of which are 23T.

 

[Kla912000]

The Amazon ds3225 or ds3235 servos are fine. But as stated, they are both 25t spline servos and you will also need to get a new 25t servo saver. The Kimbrough 123 servo saver works great with no modifications. But a lot of people like the Kimbrough 124 HD servo saver cause it is a little bit stronger, but needs trimmed a bit to match the stock servo saver. Not hard to do and only takes a minute. Both Kimbrough servo savers come with a 23t, 24t and 25t adapter. Just have to use the 25t that fits on your new servo.

 

[ramack]

Thanks for the input! Trimming the K 124, is this just trimming some excess off with a blade for clearance? Doesn't sound like an issue.

 

[Kla912000]

Thanks for the input! Trimming the K 124, is this just trimming some excess off with a blade for clearance? Doesn't sound like an issue.

Yes, that's all you have to do. The part of the Kimbrough 124 where the steering link bolts on is a big rectangle. You just have to trim it into a triangle to match the stock servo saver for clearance. Very easy, only takes a minute.

 

[ramack]

Yes, that's all you have to do. The part of the Kimbrough 124 where the steering link bolts on is a big rectangle. You just have to trim it into a triangle to match the stock servo saver for clearance. Very easy, only takes a minute.

Awesome, thanks for the input!

 

[Kla912000]

 

[ramack]

Parts on order, should arrive by Tues.

 

[ramack]

I ended up buying 3 Kimbrough servo savers, 123, 124 and 201. Then selected the 123 after trying them. When pushing on the end of the servo saver, the 124 and 201 "felt" too stiff and didn't provide any damping before the servo began to rotate. The 123 would not deflect and the servo would rotate when pushing very slowly, but would slightly deflect without the servo rotating when pushed harder and in more of a shock/impulse input. The 123 did not require any trimming to fit.

Last weekend, my son and I assembled the RC back together, then he took it out for a test drive. He did say it responded and steered better than with the stock Spektrum servo, not swerving left & right while driving straight. I'm guessing that due to the higher force servo.

While looking at a replacement servo, I've noticed the torque rating on these servos is kg*cm and not N*cm. Odd, because that's mass x distance and not force x distance.