Timo's Service & Warranty Corner

This is a thread where we go through cases that we encounter and process at our Warranty and Service corner. Starting from problem description  we document and track down the defect and do our best to figure out the cause. 

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17-11-2023

Case and symptom: Motor runs but no movement

This case did not arrive from a customer, it was actually one of our own demo crawlers which was on loan for the summer. We got a word that it made some clicklike sound when it was driven. We adviced to check the drivetrain and gears that there was nothing between the teeths which could have caused the sound. Sound stopped and everyone assumed that it was ok. Until car stopped moving and motor just spinned free. Car was put to side for the rest of the day and only one demo car was running.

When the car arrived to my desk for service, the drivetrain was actually completely stuck. Car did not move front or back when pushed on the table. I took the car under inspection strating from gear case and the cause for the problem was obvious. Pinion gear had got loose and started to slide forwards. First the unscrewed set screw shcewed the spur gear and eventually pinion gear slidede against the gear cover and melted the gear cover completely. When it stopped the plastic was melted and when it arrived to my desk the pinion was stuck on the plastic cover.

All in al, al simple fix at the first place would have saved reasonable amount of spares. Now we had to replace a bunch of parts which would have been prevented by one screw tightening.

- Spur Gear plus mounting hardware

- Pinion gear

- Gear covers

This is kind of a reminder that it is important to fix those small things immediately and not wait until the car won't move anymore.

8-11-2023

Case: Overcharged 3s lipo

Symptom: Customer states - Charger refuses to charge battery and demanded a refund.

When this battery arrived to us we were quite confused and a bit scared. All looked basically ok but after measuring the battery voltage we got a bit scared. Battery was way over charged.

We of course immediately discharged the battery to safe storage voltage before started to track down what has happened. Keeping in mind that customer shipped the battery to us for return. Ok , normally lipos are very stable when stored correctly and charged in right voltages but this one was quite scetchy situation.

We did a inspection to the battery and noticed that the battery connector seemed to be modified. This raised a suspicion about the charger which custmore might have used for charging. After consulting the customer it came to our attention that Connector was modified, so that it fitted to the Traxxas RTR Nimh DC charger - This was a really scary moment to realize that customer has been trying to charge the Lipo with a Nimh charger. After multiple attemps he ended up getting the lipo "only" to over voltage for regular 3s Lipo. Everyone can google / Check on youtube how Lipo reacts when charged with Nimh mode - > spoiler alert: it will end badly.

It is clear that there has been more than good luck that nothing bad had happened even though customer had left the battery on charger to charge. Luckily the Traxxas Charger had always went to a protect mode.

Dear customers, Please READ the manual before doing things and you never will not need to modify connectors to make them fit. If there is clear limitters molded, those are there for a reason. Someday the good luck will just run out.

Result: We ended up refund the battery and replaced the battery to Nimh

6-11-2023

Case: Burned Savöx 1251mg

Symptom: Servo went mute before the new car reached the first trails.

Backing information: Servo was used in a crawling rig to control gears. Servo replaced bigger servo which was mounted before this but was switched to LowProfile due to the limited space inside the body.

When servo comes in I connect it to our setup system (uses 4x AA battery power supply to ensure the clean power source) and see if the defect matches the description. In this case it was clear that servo was mute.

Next step is to check manually the servo's functionality. In other words mounting a servo horn and carefully trying to turn the main axle. This was completely stuck -> possible gear issue.

I opened the gear case and gears are like new (matches the amount of use described by the customer) and it turns out that the motor is seized up.

Looking at the circuit board shows that it is clear that there are damaged components on the center of the board. Not on the power fets alone which usually indicates stuck gears or over stressing the servo (EPA setup set wrong). Next step was to figure out what could cause the such a defect on the electric component in new servo. After going through the speedcontroller setups (Hobbywing Fusion) with the customer it turns out that the BEC voltage was set on 7.4V (for HV servos). Savöx 1251mg is designed before the time of HV servos, so the powersupply is built for 6V systems which do not handle the higher voltage. Simple unfortunate mistake in many builds when other servos (steering and old gear servo) are HV capable and when replacing one servo with non HV capable servo.

In this case Savöx power supply design can not withstand the higher voltage which will cause the burnt electronics. Luckily nothing in same power system (ESC, receiver and other servo) were not damaged due to this broken servo.

Result: This was not covered under manufacturer's warranty since the defect is not material- or assembly defect based.

3-11-2023

Case: Traxxas Xmaxx Servo is not turning
Symptom: Servo's motor is working and it runs all the time but servo's axle does not move

First when servo arrives to service I connect it to a test setup, so I can test the servo and repeat the reported issue.

In this case it first sounded like a simple gear issue. If gears have lost most of the teeth the main axle will not turn the potentiometer which would stop the motor from turning beyond the center point. After taking the servo apart it looked like that all the gears were ok and no clear issue was seen.

Next step was the check if this was a potentiometer issue. Potentiometer tells the servo's controlboard the position of the axle and if there is an issue with the potentiometer usually servo's motor ends up just running in some direction because there is no signal to stop to the center point. After I tested the potentiometer and realizing that it is working as it should, next step was simply looking through the electronics. Without proper "electricgizmo"testers it is impossible to say is the electronics working or not unless there is clear component failure or maybe moisture etc. None of these were found in this servo either.

So we were back at square 1 again. If motor is constantly running but gears are not turning the issue must be in the motor or motor's axle. But no, all looked fine at first glance. Going through the parts once more and cleaning the gears from grease I noticed very odd marks on the metal gear which is next from the motor. Gear's teeths were like new from most of the surface but clearly worn from one corner. After some cleaning and test fitting the cause revealed itself. It turns out that the gear on the motor's axle was moved upwards or mounted incorrectly at the factory causing the gears to be in contact on only for slight amount and had eventually given up and caused the servo to malfunction.

Result: This case was determined to be covered under Traxxas warranty after consulting Traxxas service.

This was quite an interesting case since basically everything was ok but then a simple assembly defect at the factory caused the servo to malfunction. Servo was replaced and customer's ride kept on bashing.

1-11-2023

Case: Hobbywing D10 motor is not running properly

Symptom: Motor does not start to run without a push.

Tracking down the issue:

- In most cases problems with low rpm and cogging issues are sensor related, so first we checked the sensor cable, then tried with another speed controller. This time problem did not get sorted out with those. After taking the motor apart and inspecting all components I noticed that one of the coils was cut near the electric board. Very rare case since the motor has no moving parts there and everything is mounted solid.

Further inspection showed that there was signs of vibration on the rotor axle where the front bearing is. Bearing was mint and had no play on the axle, so most likely only cause for the vibration can come from car's drivetrain. Since Drift motors are run with high rpm and maximum Turbo timings it can cause vibrations and generate heat. Heat- vibration - Cooling - Repeat will eventually cause the stress cut to the coil wire.

Fix:

As soon as the problem was found it was easy soldering job after that. Just cleaning the insulation and soldering it with a fresh tin and a drop of flux. Testing and motor runs like it should.

Result: This was covered under our own support.