Big Rock Truck took off by itself - no throttle - why?

[kantonburg]

So my boy got his big rock for this birthday today. It's pouring so I'm downstairs checking screws and checked the mesh. Simple stuff before he took it out.

I noticed if I gave it just a smidge of throttle it would keep moving forward till I hit the brake. So I did the reset the transmitter. Still moving on it's on if you give it just a smidge of throttle. If you hit it hard (holding it) it would just stop on it's own. I sat the truck on the floor and started to turn the throttle trim knob a little (no throttle) and the truck took off full speed and ran right into my wife's secretary and bent the front left shock about 20 degrees. Did I do something wrong here?

 

[Brisbane_North]

doesn't sound like you did anything wrong - terrible luck though!

would try recalibrating the hand controller with the truck and maybe also reset the ESC to default.

maybe also swap out the batteries in the hand controller...

also check the lights on the ESC when applying throttle and brake and make sure they are correct...

 

[kantonburg]

doesn't sound like you did anything wrong - terrible luck though!

would try recalibrating the hand controller with the truck and maybe also reset the ESC to default.

maybe also swap out the batteries in the hand controller...

also check the lights on the ESC when applying throttle and brake and make sure they are correct...

So I did the re-calibrate the hand controller to the truck. I thought that was maybe why it was moving on it's own when just tapping the throttle.
I can try different batteries in the controller. Got brand new duracells from a new pack. Will try new ones anyway.

As far as the lights on the ESC. (First Arrma here) When going forward it just lights up red. When going in reverse it lights up red. Should it be green? The only time I saw green was when I re-did the throttle setup.

For what it's worth I tried resetting the ESC multiple times

I could never get red and green lights to flash simultaneously as if it wouldn't reset. This doesn't seem all that complicated and pretty straight forward.


Here is the shock. Can you bend this back till I can get a new one? Also would horizon cover this if found to be something faulty? I was on maybe 15 minutes trying to figure out why it was moving forward on it's own when I turned the throttle trim and it just took off full speed not even touching the throttle.

 

[Brisbane_North]

one of my RC cars took off on its own once - my kid was playing with the switches on the hand controller - very unsettling!!

regarding the shock - possibly using a pair of pliers or multi-grips - see below...

 

[kantonburg]

one of my RC cars took off on its own once - my kid was playing with the switches on the hand controller - very unsettling!!

regarding the shock - possibly using a pair of pliers or multi-grips - see below...

Thanks for the vids.

I'm going to try a different battery tomorrow. It was a zero 2S in it. I have two of those for him to learn a slower speeds.

It's just unsettling that it just took off like that. I'm going to block it up tomorrow. I'll take bide if it keeps moving on its own.

 

[slick2500]

So I did the re-calibrate the hand controller to the truck. I thought that was maybe why it was moving on it's own when just tapping the throttle.
I can try different batteries in the controller. Got brand new duracells from a new pack. Will try new ones anyway.

As far as the lights on the ESC. (First Arrma here) When going forward it just lights up red. When going in reverse it lights up red. Should it be green? The only time I saw green was when I re-did the throttle setup.

View attachment 117245


For what it's worth I tried resetting the ESC multiple times

View attachment 117252

I could never get red and green lights to flash simultaneously as if it wouldn't reset. This doesn't seem all that complicated and pretty straight forward.


Here is the shock. Can you bend this back till I can get a new one? Also would horizon cover this if found to be something faulty? I was on maybe 15 minutes trying to figure out why it was moving forward on it's own when I turned the throttle trim and it just took off full speed not even touching the throttle.

View attachment 117246

The throttle trim basically is the center of your throttle range if you turn it up the car will start to drive forward, if you turn it down it will start to drive backwards if you have the remote and the car on. https://racenrcs.com/rc-cars-throttle-trim-explained/

 

[L3phturn]

When you calibrate the ESC with the throttle be sure you have it set at 100% and throttle trim centered. If you calibrate with the trim off center and throttle rate at 50% weird things can happen.

 

[TheBadazz]

Follow this rule, take wheels off or have on a stand whenever you play/adjust anything with the throttle. I've had a DHK Zombie go nuts on me, after I set the lash and wanted to bump the motor a bit. Come to find out the transmitter went bad. After that I take the wheels off on the stand.

 

[kantonburg]

When you calibrate the ESC with the throttle be sure you have it set at 100% and throttle trim centered. If you calibrate with the trim off center and throttle rate at 50% weird things can happen.

Ok I just looked and it was set at 50% and when I re-calibrated I can't say for certain that the trim was not centered. I believe it was because I felt like I centered everything even the steering trim.

@Brisbane_North mentioned the lights on the ESC. Should it just light up red anytime you go forward or reverse? I've seen videos of the ESC count the number of cells you have connected. Is that on the higher end BLXs?

I'll try again in the morning and report back. Thanks everyone for their help.

@slick2500

Thanks for the article.

@TheBadazz
No kidding. Lesson learned.

 

[Brisbane_North]

Should it just light up red anytime you go forward or reverse? I've seen videos of the ESC count the number of cells you have connected. Is that on the higher end BLXs?

Hi, after looking through my manual and on the internet - could not find info - so...just connected by BR V3 and had a look lol - a lot quicker!

As you say, the red light comes on and stays on whenever you touch the throttle - go, reverse or brake...

the 6s ESC's play the tunes lol...my Typhon V5 does a little jingle and then counts the battery cells...

 

[kantonburg]

Hi, after looking through my manual and on the internet - could not find info - so...just connected by BR V3 and had a look lol - a lot quicker!

As you say, the red light comes on and stays on whenever you touch the throttle - go, reverse or brake...

the 6s ESC's play the tunes lol...my Typhon V5 does a little jingle and then counts the battery cells...

Thanks for the update. I'm going to re-calibrate here shortly.

 

[kantonburg]

@L3phturn & @Brisbane_North

So I re-calibrated after charging the battery. Made sure it was set to 100% and the throttle trim was neutral. I experimented after it was calibrated and blocked up. Turned the throttle trim to the left some (reverse) and it didn't do anything. I expected the wheels to move backwards some. Then I turned right and after it went slightly past neutral the wheels started moving. Then moved it all the way to the right real quick and it ramped up quick.

Now I understand why it was moving on it's own last night when bumping the trigger. I must have had it JUST past neutral. Not enough to move on it's own, but when it got a push it would keep moving.

edit: I got the shock straightened enough that it functions. It's still BARELY bent, but works.

The grass was still wet, but the road had dried so we took it out and I ran it up and down the road. Everything worked as it should. Though I have one question about a sound my boy asked about. When it was driving by we heard a faint ticking. It may be normal and you can hear it some in the short video here minus the neighbors dogs barking.

Normal sound?

 

[Brisbane_North]

Normal sound?

not really - but should you be concerned about it...not sure...

can be difficult to troubleshoot - try and work out if it's coming from the front or back of truck - does it get worse when accelerating or braking or turning...maybe run it on some super smooth tarmac and if it goes away it may be shock/suspension related...

check the truck over and look for anything that's binding or anything in there that shouldn't be - does it make the noise when you hold it off the ground?...maybe give it a blowout with some compressed air...

 

[kantonburg]

not really - but should you be concerned about it...not sure...

can be difficult to troubleshoot - try and work out if it's coming from the front or back of truck - does it get worse when accelerating or braking or turning...maybe run it on some super smooth tarmac and if it goes away it may be shock/suspension related...

check the truck over and look for anything that's binding or anything in there that shouldn't be - does it make the noise when you hold it off the ground?...maybe give it a blowout with some compressed air...

@Brisbane_North

So we just went to the park and ran a pack through. Didn't notice the ticking, but my daughter had her Slash out also so there was extra noise. Truck seemed to run good. While batteries are being put in storage mode I made a quick vid pushing the chassis back and forth.

One item I didn't mention. I used @jondilly1974 method of checking the slipper. Held hex in and backed off the slipper then pushed till the tires slid.

Back and forth - Notice the sound is less the faster it moves.

I also pulled the power module again. I checked the mesh last night and here is me clicking the spur. I can already see debris inside the module from this afternoon. I've already decided I'm going the cutting the bottom of the chassis method instead of trying to seal the module. The higher end Arrmas already do this. Not sure why it's not across the board. Anyway here is the vid of me with the power module open

Here is a pic of the drive shaft. No lateral movement. Should the O-Ring be right next to the bearing?

EDIT:

Added video with the drive shaft removed - Normal?

 

[jondilly1974]

So we just went to the park and ran a pack through. Didn't notice the ticking, but my daughter had her Slash out also so there was extra noise. Truck seemed to run good. While batteries are being put in storage mode I made a quick vid pushing the chassis back and forth.

One item I didn't mention. I used @jondilly1974 method of checking the slipper. Held hex in and backed off the slipper then pushed till the tires slid.

Back and forth

I also pulled the power module again. I checked the mesh last night and here is me clicking the spur. I can already see debris inside the module from this afternoon. I've already decided I'm going the cutting the bottom of the chassis method instead of trying to seal the module. The higher end Arrmas already do this. Not sure why it's not across the board. Anyway here is the vid of me with the power module open

Here is a pic of the drive shaft. No lateral movement. Should the O-Ring be right next to the bearing?

View attachment 117439

Oring just retains the bearing on the shaft. It doesn't matter where it is.

 

[Brisbane_North]

I used @jondilly1974 method of checking the slipper. Held hex in and backed off the slipper then pushed till the tires slid.

I adjusted the slipper on my 4s Outcast and really wish I hadn't - I suspect it loosened itself afterwards or I didn't adjust correctly - doesn't wheely as much as it used to lol! (and I squeezed in a bigger motor and ESC which unfortunately makes it harder to take apart lol)

regarding the ticking - up to you but would probably just monitor it and see what happens after it gets a good service in a few months time - if it gets worse then investigate sooner...

 

[L3phturn]

I adjusted the slipper on my 4s Outcast and really wish I hadn't - I suspect it loosened itself afterwards or I didn't adjust correctly - doesn't wheely as much as it used to lol! (and I squeezed in a bigger motor and ESC which unfortunately makes it harder to take apart lol)

regarding the ticking - up to you but would probably just monitor it and see what happens after it gets a good service in a few months time - if it gets worse then investigate sooner...

If you made it heavier and put in a bigger motor then you need the slipper tighter than it was on stock weight and power. Thread lock that nut and let it set up overnight and it won’t back off.

 

[kantonburg]

I adjusted the slipper on my 4s Outcast and really wish I hadn't - I suspect it loosened itself afterwards or I didn't adjust correctly - doesn't wheely as much as it used to lol! (and I squeezed in a bigger motor and ESC which unfortunately makes it harder to take apart lol)

regarding the ticking - up to you but would probably just monitor it and see what happens after it gets a good service in a few months time - if it gets worse then investigate sooner...

@Brisbane_North

Is that regarding all the vids I posted or just the one from the road?

So I already had 10,000CST diff fluid waiting. I know Arrma treats that like gold and never fills them properly. I'm going to let him run while the weather is good then get at each diff and fill properly.

 

[Brisbane_North]

difficult to pick the noise up on video - if you can hear the ticking with everything installed then removing the power module and running it back and forth on the front wheels only and rear wheels only may help tell you which end is ticking (or if no ticking then it's the power module).

also check every individual tooth on the power module i.e. spur and pinion - if one tooth is broke/chipped then it would produce the ticking...the gear mesh looks good from the video I think...

 

[kantonburg]

difficult to pick the noise up on video - if you can hear the ticking with everything installed then removing the power module and running it back and forth on the front wheels only and rear wheels only may help tell you which end is ticking (or if no ticking then it's the power module).

also check every individual tooth on the power module i.e. spur and pinion - if one tooth is broke/chipped then it would produce the ticking...the gear mesh looks good from the video I think...

Definitely no noise with the power module removed. Spur and pinion look good. Will run a few packs through and report back. Weather permitting.