Big Rock 4x4 Big Rock metal spur gear catastrophe

[chaosmage]

Hi all,

I'm an RC truck noob, just got a Big Rock on 3S, swapped a spur gear for "ARRMA HEAVY DUTY 57T SPUR GEAR 0.8MOD" and it killed everything inside after a few rides. I've tightened it pretty hard, as it was slipping all the time.
Now I see both bearings are gone, gear enclosure, pinion gear. I would appreciate if someone can help me to figure out how to fix that.

1. what did I do wrong?
2. what parts do I need to buy? and where do you usually get them?
- someone was recommending Robinson Racing Extra Hard Steel .8 Mod Pinion Gear w/5mm Bore (13T)
- Arrma 4x4 Composite Motor Mount Set
- no idea what bearings are those
3. it has chewed the center driveshaft too, but that was since the very beginning ...

Thanks a lot!!

P.S. I think I've got it. Tightened the slipper way too much, and here is the result.

 

[skt07]

What were you hoping to achieve with the metal spur gear? In everything I've read, putting a metal spur gear in a Big Rock seems to cause a lot of problems with no real benefit... Maybe just put everything back to stock?

 

[chaosmage]

What were you hoping to achieve with the metal spur gear?

Plastic spur gear didn't last a few weeks, I was hoping to get more durability and less maintenance.
And stock ... stock ... doesn't sound fun?

 

[skt07]

Plastic spur gear didn't last a few weeks, I was hoping to get more durability and less maintenance.
And stock ... stock ... doesn't sound fun?

I'm all for upgrades (see my other posts lol).

Are you using the stock motor?

I've run many many packs on my Big Rock and the spur gear seems fine. Maybe yours is getting chewed up by sand or the type of terrain you're driving on? Check out the posts on protecting dirt from getting to the spur gear or alternatively cutting a hole in the bottom of the chassis to let debris fall out. And then use the plastic spur gear...

 

[Stevenj76]

Did you add the extra slipper pad needed when you go steel ?

 

[chaosmage]

Are you using the stock motor?

Yeah, the motor is stock. I'd love to move towards 6s tho, as I have a lot of batteries from my Drone FPV hobby.

Terrain - maybe you're right, I'm always on sand. When I've opened the motor mount for the first time it was full of plastic "sawdust", but no sand particles or anything else.

Did you add the extra slipper pad needed when you go steel ?

No .........

 

[Stevenj76]

That’s your reason for failure

 

[chaosmage]

That’s your reason for failure

should it be just a regular slipper pad like ARA310908? and where should it go?

 

[Stevenj76]

Yes , four are needed for the metal spur , it’s been constantly slipping hence the burn . Search Jon’s slipper setting video . Thats how I do mine now

 

[bicketybam]

Your bearings might have failed first and contributed to that mess.

 

[Cheapbastard]

should it be just a regular slipper pad like ARA310908? and where should it go?

You assemble it using the exploded view of a 4s Outcast and Kraton, the only difference between the two assemblies are the metal spur and one extra slipper pad in the front. In your first pic you can see where the rear slipper plate was rubbing on the back cover plate.

 

[chaosmage]

You assemble it using the exploded view of a 4s Outcast and Kraton

Makes sense now! ordered the parts, thanks a lot

 

[Surchaufeur]

I don't see why it would fail like that even me with a trash gearmesh never achived that destruction so far my plastic spur on my typhon is doing great doesn't look great but the noise it makes never changes so to that means the spur gear is not getting destroyed

 

[JAM]

Did you order a new motor housing?

Jennys rc is the way to go if not.

 

[chaosmage]

I don't see why it would fail like that even me with a trash gearmesh never achived that destruction so far my plastic spur on my typhon is doing great doesn't look great but the noise it makes never changes so to that means the spur gear is not getting destroyed

The noise it was doing was terrible after replacing the spur gear, I need to learn to open it BEFORE it stops moving from a malfunction haha
Plastic spur got all shaved off in 2-3 weeks - photo attached.

Did you order a new motor housing?
Jennys rc is the way to go if not.

Yes, took it off eBay - RCExpress, eBay had better price than their website surprisingly.
Will check JennysRC next, thank you!

 

[Shazz4321]

I love modding and upgrading with everything however sometimes stock is good (ish).

I have run 100s of 3s packs through my BRCC now and I have only recently replaced my Spur.

Something good also is to get the stronger loctite and be generous on the pinion grub screw and motor mounts and casing bolts ( the ones that go into the metal motor mount at least). Any slipping of gear mesh and a spur dies.

In a bad crash, a stock plastic spur may break. If you have a bad landing and the gear mesh gets mucked a plastic spur will just melt or grind away and leave everything else mostly in tact.

A metal spur will not be the weakest point as you have found out and so the death moves to different and probably more expensive things like motors, bearings, clutch plates, driveshafts or casings etc.

For me a plastic spur is a good cheap breaking saftey point should things go crazy.

Don't get me wrong, I have a few good mods on mine however I feel trying to go 6s on the BRCC for me is a little too much. 4s I can get behind as I have seen it but you basically need to replace every key component (ESC, Motor, Gears, shafts etc) and by that point you are a good way to a 6s.

 

[2fast4u]

Looks like in both photos that the pinion needed to be a little farther out on the motor shaft so the teeth are completely engaged. That along with improper backlash due to the fixed (un adjustable) motor mount would explain premature failure of the pinion, spur, or both. That said, @bicketybam has also made a point of another potential root cause.

 

[bicketybam]

Looks like in both photos that the pinion needed to be a little farther out on the motor shaft so the teeth are completely engaged. That along with improper backlash due to the fixed (un adjustable) motor mount would explain premature failure of the pinion, spur, or both. That said, @bicketybam has also made a point of another potential root cause.

I've had great luck with my plastic spur gears. The ones in my Granite and BRCC are at least 18 months old. Even when I ran with an overtightened slipper, the wheel driveshafts would break before the spur would strip.

 

[dude]

Since I shredded 3 plastic spur gears within a few weeks, I've upgraded to a Robinson Racing pinion gear and a Hot Racing spur gear. So far (~5 Packs) no problems. I added a hole in the chassis plate for dirt to get out and now i can see if the spur gear is ok.

And i had to modify (making long holes since the sliding motor mount isn't availible atm) the motor mount since the stock hole were too close so the gear mesh was way too close. The second spur gear did last for about 1 pack So either the spur gear had a diameter which was too big or the distance is too close. I experienced inaccurate tolerances in the arrma parts.

Adjusting gear mesh is kind of hard in the 3S rigs since the spur gear is wobbling until the case is closed - but now you cant see / feel anything ;-)

 

[RCbuzz]

I agree with you 100% there.

Adjusting gear mesh is kind of hard in the 3S rigs since the spur gear is wobbling until the case is closed - but now you cant see / feel anything ;-)

After I sealed up my power module using some double sided tape and leaving the protective film down it helped alot. One thing, I am surprised how quick the stock metal pinion wore down and wonder if that contributed to early spur death.

I like to test mesh after the power module is back together and move the spur (listen for the clicking).