Pinion advice needed for crawling with 3S

[theTman]

I just got a bomber yesterday after being out of the hobby for a while. I decided to go with a 3S lipo, but I don't like how much wheel speed the stock gearing gives it. I'm running the stock motor until it dies fyi. I am debating how much I should drop my pinion size. I don't have a lot of experience with gearing, and I am not sure if going from 12t to 11t would be enough to get me the slower speed and torque for crawling. Maybe a 10t or 9t? Trying to avoid buying multiple pinions as I am on thin ice with the wife when it comes to upgrading things right after getting the bomber, a charger, battery, front cvd's, and a better servo.

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[SCREAMER]

I'd try a 10t. 11 won't be that much of a difference and a 9 tooth pinion is very small and will wear quickly. I also feel gear engagement is compromised when you get down to that small of a diameter pinion. Probably why it's the smallest I've seen available in 32pitch. I'd suggest Robinson racing extra hard pinions. Are you familiar with setting gear mesh?

[WHITE-TRASH]

11 tooth pinion and up size the spur.

[theTman]

Originally Posted by SCREAMER

Isn't the stock pinion a 14t? Dropping to a 12 will be a significant difference.

Edit: stock pinion is 12t. I'd try a 10t. 11 won't be that much of a difference and a 9 tooth pinion is very small and will wear quickly. I also feel gear engagement is compromised when you get down to that small of a diameter pinion. Probably why it's the smallest I've seen available in 32pitch. I'd suggest Robinson racing extra hard pinions. Are you familiar with setting gear mesh?

Yep, I know the old paper trick for setting gear mesh.

Originally Posted by WHITE-TRASH

11 tooth pinion and up size the spur.

What is the benefit of this over a 10t pinion and stock spur? I believe the stock spur is 64t, and biggest spur option is 68. With 11/68 it isn't as geared down as 10/64.

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[WHITE-TRASH]

11 tooth spur is readily available in any hobby shop. 10 tooth is out there but harder to find. If you can find a 10 tooth then it's of course a better option.

For the money spent you could easily drop a higher turn integy motor into the rig and go slower.

[theTman]

Hmm, I wonder if 45 would be good, or perhaps 55. I have an old integy 55t in my ancient crawler that I could pop in for a test. Is there a benefit of going up in turns on the motor versus gearing down?

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[WHITE-TRASH]

Larger pinion will have more tooth contact on the spur and be stronger. Higher turns with more voltage is more efficient and provides a smoother bottom end without sacrificing top end.

I've found my sweet spot is 35 turn on 4s. The bomber trans is geared differently than the scx style trans I use so your results will likely be different.

[SCREAMER]

You could also switch to smaller tires or regear both diffs. Maybe a two speed transmissions? Geeze, both of you are making this way more complicated than it needs to be. Leave the motor in there, use the battery you have, leave the spur alone, just drop 2 teeth on the pinion. It's like $8 for a quality pinion.

[WHITE-TRASH]

The problem is that 2 teeth on the pinion isn't going to make much difference. It'll help but it's not going to turn a bomber into a crawler.

[SCREAMER]

Thats really for Tman to decide. For me 2 teeth made a huge difference. At least it's the cheapest simplest option to start with. I'm betting he doesn't have 4s batteries and swapping the motor or spur will take more effort and money than just trying a smaller pinion. Start small, change one thing at a time, then move to the next component.

[WHITE-TRASH]

Sure starting off with a smaller pinion is the cheapest solution. It will help too. Adding a larger spur will help even more and dropping in a higher turn motor will help even more than both gearing solutions combined. So far we're only talking options, not required mods.

I didn't recommend going to 4s batteries at all. That would be completely counter productive to making his bomber slower. I simply mentioned that it's what I run to put my rig in the sweet spot, nothing more.

[SCREAMER]

I understand what you're saying. The title says pinion advice. He was asking about pinions. WT, you have this habit of cluttering a simple answer with a bunch of extraneous info. You're talking about 4s and SCX transmissions. We both know there's 15 different ways to speed up or slow down wheel speed. He asked for this one.

[WHITE-TRASH]

Originally Posted by SCREAMER

I understand what you're saying. The title says pinion advice. He was asking about pinions. WT, you have this habit of cluttering a simple answer with a bunch of extraneous info. You're talking about 4s and SCX transmissions. We both know there's 15 different ways to speed up or slow down wheel speed. He asked for this one.

I like to make sure the bases are covered so more questions that are related to the original inquiry are taken care of to save time. I simply answered the original question and was asked to expound further on my answer. The snowball took off from there.

[cmbscx10]

Dang it. I had my popcorn all ready to go for a lunchtime snack and some fun reading.

[2-shot]

Personally, here's what I would do...

First - Drop two teeth on the pinion gear and try it (this is the cheapest option).

Second - go up (bigger) ton the spur gear and try it. You may have to put the stock pinion back on depending on the next biggest spur gear (the second cheapest option).

Third - I would go with a higher turn motor (this will be the most expensive option - buying a motor).

I'm not a gearing guru, but I would start with the cheapest, easiest option and go from there. No need to over think it!


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[theTman]

I have a robinson 10t pinion arriving tomorrow. If it isn't enough then I will go for an integy 45t pro motor for 30$. All the 68t spurs I could find for yeti trannys were metal and about 20$. Might as well upgrade the motor at that point as the stock one doesn't last long I hear. I also think keeping the spur plastic would be best as it is easier and cheaper to replace if it shreds versus going metal and having another driveline part become the weak link.

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[SCREAMER]

The stock motor will last longer with a smaller pinion. Let us know what you think about the 10t.

As far as the spur goes, that's what the slipper is for. You don't have to worry about engineering a "fuse" in the driveline with a slipper. I run Robinson Racing hardened steel slipper spurs on 7 rigs and have never had driveline breakage with half those motors being brushless on 3s. Don't be afraid to run a steel spur as long as it's a slipper spur. If you were running with a slipper eliminator it'd be a different story.

[theTman]

Originally Posted by SCREAMER

The stock motor will last longer with a smaller pinion. Let us know what you think about the 10t.

As far as the spur goes, that's what the slipper is for. You don't have to worry about engineering a "fuse" in the driveline with a slipper. I run Robinson Racing hardened steel slipper spurs on 7 rigs and have never had driveline breakage with half those motors being brushless on 3s. Don't be afraid to run a steel spur as long as it's a slipper spur. If you were running with a slipper eliminator it'd be a different story.

I always thought that with crawlers you tighten the slipper all the way down so you don't slip. Do these trannys made for rock crawlers have slippers with a higher force threshold? My last crawler was built before any company made rock crawlers so we scavenged trannys from other rc's.

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[Mega Fattie]

I was running a 11T steel pinion and a 64T hardened spur. It worked great, but i was worried about the 11T pinion getting chewed up. Now i am running a 13T hardened pinion and a 64T hardened spur. Still crawls as before with a little more top speed, and i feel better knowing it might last a while.

[SCREAMER]

Originally Posted by theTman

I always thought that with crawlers you tighten the slipper all the way down so you don't slip. Do these trannys made for rock crawlers have slippers with a higher force threshold? My last crawler was built before any company made rock crawlers so we scavenged trannys from other rc's.

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I wouldn't tighten a slipper down until it locks up, it's there to save your driveline. Let it do its job. I tune the Robinson slippers on my trucks to give the exact amount of slip I want. I did the same thing with my Summit running a Castle monster combo on 6s. The slipper is adjustable to your preference and needs. The biggest reason to replace the stock plastic spur is because it will flex like crazy and the paper slipper pads are a joke. For just over $30 you can have a Robinson spur that will last forever and keep your mesh constant. For the most part, on a brushed setup the stock slipper is fine though.