Granite Grinding spurs all of a sudden

[GuyFromCanada]

Hi all, my Granite Mega 4x4 is grinding up spurs for no good reason as far as I can tell. A couple days ago, things were running fine until I blew the servo. Okay, fine, today I swapped with my other truck today. Now when we went out, the gear mesh was making an awful sound and within a few minutes, the spur teeth were mostly gone.

I swapped the spur for another. Same thing. I'm using a Robinson racing 14T pinion with the original spur on 2S. This is a Traxxas Titan 550 12T motor instead of stock Arrma brushed motor. The motor shaft feels nice and tight, unlike the last Arrma brushed when the bushing went.

Any thoughts? I didn't touch any of the drive train when working on the servo, so I don't see what could have changed since the last time it was meshing okay.

 

[ThatDrewGuy]

The first thing I think of is how tight the pinion is against the spur. That will cause it to grind apart. There should be about a sheet of papers space between the 2. I can almost assure you that's what happened.

Here's a quick link to help you out with that.

http://www.rcdriver.com/set-gear-mesh-rc-car-truck/

That should fix it for ya!

 

[Dustin Mustangs]

I agree with the above and will add that you should double check that both gears are securely held in position. I had a string of stripped spurs, with properly set gear mesh, and it was because a couple of loose screws were allowing the motor plate to slightly rock back and forth. A bad bearing on the transmission input shaft could do the same.

 

[GuyFromCanada]

Screws all seem to be in place, and when I close up the motor mount, it all seems nice and tight. The Mega 4x4 has predefined motor mount holes for a given pinion size, so I'm not sure how to go about adjusting it.

When I get some new spurs, I'll try slipping some paper through to see...

 

[GuyFromCanada]

A bad bearing on the transmission input shaft could do the same.

I was thinking about that this morning. The slipper shaft seems to turn pretty well, though still on stock bearings. Unfortunately there is no way to fiew the gear mesh vary with spur rotation when the case and bearings are in place...

 

[larrys4227]

Is sand working its way into the housing? When you took the assembly out, did alot of dirt/sand fall out? Debris gets in there and has no way to get out and the spur just grinds itself to death. I cut a relief slot in the chassis, right under the spur, to allow debris to escape. I am still on my original spur after dozens of battery packs. I run brushless with 22t pinion on 2 and 3S

 

[GuyFromCanada]

Is sand working its way into the housing? When you took the assembly out, did alot of dirt/sand fall out? Debris gets in there and has no way to get out and the spur just grinds itself to death. I cut a relief slot in the chassis, right under the spur, to allow debris to escape. I am still on my original spur after dozens of battery packs.

My spur was working great too, until it didn't There has been sand, but not very much. When I opened the motor mount after the carnage, there were spur bits falling out almost like sand...I didn't even have a change to drive it and get sand inside before the spur died. The spur wasn't smooth, just most of the teeth were gone.

What is most puzzling is that I didn't touch the motor mount between when it worked and when it didn't. I did a water break-in with this Titan 550 and it definitely had a lot more torque and power than when I didn't do a break-in. Could my slipper be too tight? I sort of doubt it because there is lots of room left to tighten it.

 

[larrys4227]

I saw a post from Arrma direct once that the correct slipper adjustment on the MEGA's is too tighten it all the way, and then back off 1/2 turn. I back it off 3/4's and still on my original of everything, including plastic input gear. I, as well, run a Robinson Racing Hardened 22t pinion. Maybe I don't beat on mine hard enough .... LOL

 

[GuyFromCanada]

Maybe I don't beat on mine hard enough .... LOL

Well, in this case, it was making the higher pitched whine as soon as I started driving and continued on straight driving. I thought it sounded strange, but continued with it anyway and destroyed the spur gear. After two gears, I know the sound that means death, so I'll avoid that once I get new gears and try fixing it right away.

I also ordered some Fast Eddy bearings, so I can swap those out as part of debug when they arrive.

The spurs are pretty cheap, so I order 4 more...hopefully I can figure out by the end of that!

 

[GuyFromCanada]

For some further input, these are some pictures of a new pinion with new spur, and old pinion with old spur. Guess what is which Both pinions are Robinson Racing...I don't recall if the pinion looked like that when I installed it or not but clearly there was a problem. Could the plastic spur have done that to the pinion?

 

[GuyFromCanada]

So I just tried the truck out, and there is no more high pitched whine from the gear mesh...makes sense since the pinion doesn't look like crap anymore. Everything lasted until ESC thermal...hopefully I'll actually be able to finish a battery pack with my new CC ESC and motor after I install them!

 

[ptr1ck]

I just got back from the beach with my truck. Sand is this things enemy for sure. I wasn't running and protection and destroyed a spur in half a pack.

I've since got some knee-high ladies hose, cut the toe out and have it over my chassis. I had to take the front wheels off to fit it. It's pretty tight and has good coverage but got a bunch of sand still within 2 minutes of driving.

There's no good way that i have found to keep that open bottom transmission from picking up stuff.

 

[bicketybam]

It's not a dune buggy!

 

[ptr1ck]

Oh wow it's not?

"Honey, I need another one for the beach!"
"Whattt?!"

 

[Jerry-rigged]

Any excuse to add to the fleet, right? LOL

After I burned my first spur gear, I went with Megasty's solution - a 32p gear from a Yeti. Get the 60t for the stock motor.

 

[ptr1ck]

I was doing OK until the truck hit the edge of the surf. The water rushed to the back in the chassis and carried the sand right into the spur.

 

[bicketybam]

Oh wow it's not?

"Honey, I need another one for the beach!"
"Whattt?!"

What she doesn't know won't hurt her

 

[larrys4227]

Thats not the right pinion for that spur gear

 

[GuyFromCanada]

Thats not the right pinion for that spur gear

That's what I figured out But it's all good now, and I know to check the pinon regardless of what the packaging says!