Throttle Servo Question

[aoennn]

Hi guys,


Just got a Redcat Rampage XB (gas). Having a major blast!


I broke in the car properly (1:~25 oil to gas, ran it idle for 1 tank, then low speed for about 3-4 hours). After that, I started going hard on the acceleration. After that, the idle RPM was too high so with a little adjustment, the car became perfect all around.


A few hours ago, I was going really tearing the road up. I went top speed 4 to 5 times for about 1 to 3 seconds each time. The car did it seamlessly and nothing seemed out of the ordinary when I drove it close to me to take a quick look.


However, on the very last hard acceleration, I stopped the car and wanted to go hard again but it began acting erratically. It would brake and the RPM fluctuated. I could quickly tell the throttle servo wasn't responding to the input so I shut it off quickly to avoid a runaway.


I turned on the receiver and the transmitter and began troubleshooting and here's what happens:


1. The throttle servo "hangs". It suddenly stops responding to input.


2. When it does respond, if I press all the brake for example and then let it go, it would return but it's sloppy (it jerks a little around the neutral position).


3. I can tell the steering servo is fine since it has a crisp response and doesn't miss or ignore input.


I messed with the transmitter and receiver units but to no avail. I unplugged/plugged the wire sockets, tried messing around with the transmitter's tuning knobs but the throttle servo wouldn't have any of it. I left the car for a couple of hours, came back and it still did the same thing.


So, before I up and decide that it's broken, I wanted to get some feedback from you guys. I'm a newbie to the deal so I don't want to jump to my first conclusion.


So to wrap it up:


1. What do you think the problem is?


2. Do you think it can be fixed?


3. If not, I looked at another thread called "Servo Alternatives" by Dreggsta and the XQ4013 looks like the best choice since it's a direct fitment. I'm not exactly savvy in terms of fabricating stuff. The value also seems nice. Do you think the XQ4013 is a good alternative?


Apologies for the wall of text guys!


Thanks

 

[Guest]

Definitely the servo is on its way out. Make sure the end points are set when you install a new one.

The Hitecs also are direct fit for the throttle / brake servo.

I like the 5645 or 5685 for the higher voltage lipo receiver battery packs.

 

[aoennn]

Thanks for your quick response, RCDAD.

I will definitely consider the Hitech servo.

Can you please tell me what are the endpoints and why do I have to set them?

Thanks!

 

[Guest]

The EPA (end point adjustment) it the position where the servo stops are set.

You want the servo to stop right before or at end of linkage travel. If the servo is still trying to push when the linkage stops moving it will burn out. It's safe to say that is what probably caused your servo failure since it happened after full throttle passes. In any RC vehicle the EPA should always be set before running.

 

[aoennn]

Ahh alright, that figures!

I adjusted my steering servo so that it doesn't make a crunching sound when I go lock to lock but the manual never said anything about the throttle servo.

Ok, time for a new servo I suppose!

Thank you very much for your quick and spot on replies, RCDAD.

I saw on RCpitstop.net that you guys sell a belt drive system. I was wondering how does that improve performance/reliability. I understand lowering the rotating mass allows the engine to reach target RPM faster but what about reliability? I saw a couple of videos where people using the stock gear plate absolutely ruined the gears in that area due to the bearings being too small and seizing.

I'm debating buying one of them Jetpro exhausts and installing an aluminum gear plate with bearings so that that part of the car doesn't get destroyed with the extra power.

Which do you think is a better choice? The Jetpro exhaust + aluminum gear plate (about $240 total) or the belt drive system?

If this is not the appropriate place to discuss it, I'll sniff around or PM you. My bad if this has been discussed elsewhere.

 

[Guest]

For longevity, I'd say aluminum plate for sure. The gears will last longer than a belt as well. However, you can get a lot of time on the belts. Performance is always a trade off.

The belt drive can increase performance as it helps with responsiveness, but it does not compare to the gains a tuned pipe give.

So if you need to choose between a pipe and a belt drive I would recommend the pipe. A good tuned pipe makes a night and day difference in performance.

 

[aoennn]

Thanks for the response RCD. I slapped in a Hitec 5645MG for throttle, worked like a charm. My car came with a 2500 capacity NiMH battery that had 6 volts so it worked out well. I also put in an aluminum gear plate and Jetpro rear mount pipe. Absolute beast now!

Thanks again

 

[Guest]

Good to hear....

Jetpro makes some nice pipes.