Granite 4600Kv motor w/3s = mangled spur

[bicketybam]

I've been running a 4600Kv motor with a 2s battery on a stock Granite for 2 weeks now. Ive also went to a 17t pinion. Other than me busting a front shock shaft, nothing else has broke from the bl swap. Today I decided to try a 3s battery. It lasted about 10 seconds. It wheelied a few times and then that terrible stripping gears sound. I took it inside, disassembled and found that the spur was toast.

So where do I go from here? Should I have gone back to the stock pinion before I attempted 3s? Would that have mitigated the damage? Or is 3s and a 4600Kv motor just too much for the truck? Do they make a metar spur? I have a feeling that would just transfer the breakage to some place else in the drivetrain.

I can beat the hell out of the truck with the 4600Kv motor and a 2s battery. I'm thinking I should go back to that and call it a day. Thoughts?

 

[bicketybam]

Can I run either the Arrma 48P 81T spur or the Arrma 48P 87T spur?

 

[Mentolio]

Too much power? I dunno, there are more than a few cars out there running plastic 48 pitch spurs that are 3S capable (just about everything Traxxas comes to mind). Could Arrma gears be inferior? Not impossible, but really doesn't seem likely to me. Speaking strictly from my limited experience with my Granite 4x4: I think that the gear mesh, as determined by the numbered pre-drilled holes is too tight. So far I've only run 14 & 17 tooth sprockets in the stock positions, and a 25 tooth sprocket in the 21 tooth position. In all positions I took a small, round, rat tail file to one of the holes in each mounting position, and enlarged them slightly in one direction to allow me to pivot the motor slightly. In this way I am able to loosen-up the gear mesh a bit, which I think will help with gear longevity once I switch to brushless (some day).

 

[bicketybam]

I had the slipper clutch cranked all the way down, which probably wasn't the smartest thing to do.

I have to say that parts availability for this truck is pretty lousy. All the common parts that break are back ordered everywhere. I totally get that breaking things is part of the RC hobby but not being able to source parts is a huge negative for the brand.

 

[GuyFromCanada]

Don't worry, I just did it on 2S...

For spur gears, I found a place that had them, and bought 6

 

[bicketybam]

Don't worry, I just did it on 2S...

For spur gears, I found a place that had them, and bought 6

Want to sell me one? lol.

You have a Castle 3800Kv motor, right? Or am I confusing you with someone else?

 

[GuyFromCanada]

Want to sell me one? lol.

You have a Castle 3800Kv motor, right? Or am I confusing you with someone else?

Yeah, I'm running the CC 3800 kV. If they are giving stupid wait times like a month, then I could try mailing a couple down, I think I have 4 left (I experimented a few times). I need to buy some more pinions as well, so I could probably just order some more spurs.

 

[bicketybam]

Yeah, I'm running the CC 3800 kV. If they are giving stupid wait times like a month, then I could try mailing a couple down, I think I have 4 left (I experimented a few times). I need to buy some more pinions as well, so I could probably just order some more spurs.

It's all good. I back ordered a few and there is one LHS 60 miles away that shows them in stock. So if I get desperate I will make the trip.

How are you chewing through the spurs? You shouldn't be throwing down more power than my CC 4600/SW4 combo on 2S. I drive the heck out of my Granite with the 2S LiPo. It wasn't until I put that 3S in there that things went south. On 2S you should be fine, no?

 

[GuyFromCanada]

60 miles isn't too bad, it could be much further I'm lucky since my LHS is about a 20 minute drive, mostly highway.

The 3800 is a slightly longer motor case, so it is possible it puts out a little more torque due to rotor design or something. This time, I was being stupid trying to wheelie by going in reverse, then full throttle forward. This is with a Mamba X ESC with no decrease in throttle punch setting...I think. It barely breaks a sweat so I'm glad I went big with the ESC in some respects.

In my other cases, something in my gear mesh wasn't right and I don't know what it was...something caused me to chew up a couple spurs that way, and that last pinion in that scenario looked all mangled as well.

 

[Jerry-rigged]

Here is what I did -

Worth noteing, that spiral aluminum can spacer was not a great idea, long term. Better would be to us the inner race from a 10x15x4 bearing, or get some 24g stainless plate (available at craft stores, and some hobby shops) and cut something similar to my spiral spacer, but just a single circle, not a spiral.

Also, if you have not done it -

 

[bicketybam]

Thanks, Jerry. I ordered the parts for the Yeti spur mod and I'll give it a go.

I went back to my LHS to see if he could get the stock spur from the other Hobbytown that is 2 hours away from me. Turn out he had one stock spur sitting in the back that he never put into inventory. I just put it in and changed back to the stock 14t pinion. The 17t pinion I was using didn't quite mesh with the entire width of the spur. The stock one does. I'm going to set the slipper a little lose and try the 3s pack again. Hopefully I don't strip the spur again. Fingers crossed!

 

[GuyFromCanada]

Is that a Robinson racing 17t? I noticed they seem to cover the spur maybe 66% any other good pinions to consider?

 

[bicketybam]

Is that a Robinson racing 17t? I noticed they seem to cover the spur maybe 66% any other good pinions to consider?

I'm not sure except that I know it isn't an Arrma pinion. The set screw is big and sticks out, which prevents me from getting it to match up with the entire spur.

 

[GuyFromCanada]

I'm not sure except that I know it isn't an Arrma pinion. The set screw is big and sticks out, which prevents me from getting it to match up with the entire spur. View attachment 20221

I have the same issue with my Robinson, it is off to the side because of the screw. Did your pinion get damaged too? Looks like the teeth are broken a bit.

 

[bicketybam]

I have the same issue with my Robinson, it is off to the side because of the screw. Did your pinion get damaged too? Looks like the teeth are broken a bit.

Hard to tell but I'm not going to use it anyway. I don't like that it doesn't cover the whole spur. It might be a little chewed up.

 

[bicketybam]

The spur survives!

I set the slipper tight but not locked all the way down.



I then used the castlelink software and my laptop to set the punch control at 25%. This combination was perfect for me. I used an 11.1V 5200mAh 50C LiPo. Holy hell it was fast, even with the stock 14t pinion. I had been running a 17t pinion with a 7.4V 7600mAh 75C LiPo. The difference is night and day. It wheelied (and flips, lol) from almost anywhere in the throttle. I tried a few speed runs and ran into two issues. One, it was very hard to control and two, the tires looked like they were going to explode. I ran mostly in dirt and grass with a little asphalt mixed in (my driveway). I ran the truck hard until LVC. The hottest point on the motor was 214 degrees Fahrenheit and the SW4 ESC was 114 degrees. According to Castle's website the SW4/1406-4600Kv combo is not to be used with 4WD short course trucks. It only recommends 3s for limited runs in 2WD stadium trucks and buggies as temperatures will rise quickly. So I'm really pushing my luck running this combo on 3s in a 4WD monster truck. But man is it fun!

 

[GuyFromCanada]

Holy hell it was fast, even with the stock 14t pinion.
...
The hottest point on the motor was 214 degrees Fahrenheit and the SW4 ESC was 114 degrees.

Are you using the predrilled pinion holes or did you adjust the mesh at all?

214 F is crazy...need water cooling!

 

[bicketybam]

Are you using the predrilled pinion holes or did you adjust the mesh at all?

214 F is crazy...need water cooling!

I used the predrilled 14t hole. I am running the pinion and spur that came stock on the truck.

I know 214 is super hot. I've already speced out my next esc/motor combo.

 

[Bri26]

Personally, I would stick with 2S. Maybe use a 2S HV pack which get you a little more speed.

Best regards,
Brian

 

[Jerry-rigged]

For a 4600kv motor, yeah 2s only. If you really want 3s, run a lower kv motor.