Motor/gearing help

[Bliss_RC]

Whats up folks,

So I decided to purchase a holmes hobbies trailmaster 550 21t brushed motor for my bomber. Based on their recommendations, I should be running an 11t pinion and 68t spur gear. Couple of questions here....

1. Will an axial 3mm spur gear fit on the 1/8" HH motor shaft? Its pretty damn close when you compare both in mm but I just want to make sure.

2. Is it possible to find a 68t plastic spur gear? I've tried looking all over the place and all I seem to find is metal.

Also I plan on getting an aluminum motor mount to go with it all.

[BOMBERINOZ]

Originally Posted by Bliss_RC

Whats up folks,

So I decided to purchase a holmes hobbies trailmaster 550 21t brushed motor for my bomber. Based on their recommendations, I should be running an 11t pinion and 68t spur gear. Couple of questions here....

1. Will an axial 3mm spur gear fit on the 1/8" HH motor shaft? Its pretty damn close when you compare both in mm but I just want to make sure.

2. Is it possible to find a 68t plastic spur gear? I've tried looking all over the place and all I seem to find is metal.

Also I plan on getting an aluminum motor mount to go with it all.

1 Yes they are typically 3mm for the smaller motors & 5mm for the larger brushless motors

2. Closest you will find in plastic will be a 64T

The motor mount is a good upgrade, helps soak up & dissipate some of the heat from the motor & also keeps the pinion & spur gear mesh better aligned via less movement
I have an ST Racing aluminum motor mount for my Bomber & my sons Yeti Score

[Bliss_RC]

Originally Posted by BOMBERINOZ

1 Yes they are typically 3mm for the smaller motors & 5mm for the larger brushless motors

2. Closest you will find in plastic will be a 64T

The motor mount is a good upgrade, helps soak up & dissipate some of the heat from the motor & also keeps the pinion & spur gear mesh better aligned via less movement
I have an ST Racing aluminum motor mount for my Bomber & my sons Yeti Score

Thanks for your input. Now that I'm looking into it, it seems the stock gearing is 64/12. I know I'm new to this stuff, but that doesnt seem like much of a difference from a 68/11 setup. Please correct me if I'm wrong.

[durok]

68/11 with stock HD diff gears = 35.03 which is slightly slower but torquier than 68/12 = 30.22 stock gearing...

You could always pick up a 11t or 10t pinion for the 64t spur to bring the ratio closer or basically equal to it.

64/11 = 32.97, for example. These numbers are in the back of the RR10 manual...

[Bliss_RC]

Originally Posted by durok

68/11 with stock HD diff gears = 35.03 which is slightly slower but torquier than 68/12 = 30.22 stock gearing...

You could always pick up a 11t or 10t pinion for the 64t spur to bring the ratio closer or basically equal to it.

64/11 = 32.97, for example. These numbers are in the back of the RR10 manual...

i ended up just ordering a 68/11 setup based on holmes hobbies recommendation. thanks for your input. i didnt realize there was actually any useful information in the manual...lol everything ive tried to look up before wasnt able to be found in there so i kinda gave up on it

[durok]

Here's a fun site to play with gearing numbers, if you want to go further with your research:

R/C Calculations

[BOMBERINOZ]

The gearing ratio's are one thing but the actual dimension / OD of your tire determines the final ratio also

Fitting small SC tires vs very tall crawler mud tires will be worlds apart in terms of changing the overall speed & gearing

[CoolRunning]

I have a 21T 550 Titan in a stock (light) Bomber with stock 12/64 gearing. IMPE, that gearing will probably not play well for crawling on 3S. Go's like a cut cat for a cheap brushed setup on 3S though.

I installed a 2 speed and that can crawl all day and zoom around flat out all afternoon without problem. Fantastic setup and nearly a year later works perfectly even going in numerous creeks and driving in wet weather. My son has a similar setup in his SCX10 and when he once forgot to shift into low gear for some crawling, the motor got very unhappy very quickly.

[Bliss_RC]

Originally Posted by CoolRunning

I have a 21T 550 Titan in a stock (light) Bomber with stock 12/64 gearing. IMPE, that gearing will probably not play well for crawling on 3S. Go's like a cut cat for a cheap brushed setup on 3S though.

I installed a 2 speed and that can crawl all day and zoom around flat out all afternoon without problem. Fantastic setup and nearly a year later works perfectly even going in numerous creeks and driving in wet weather. My son has a similar setup in his SCX10 and when he once forgot to shift into low gear for some crawling, the motor got very unhappy very quickly.

do you mean the stock gearing will not be good for crawling, or the 68/11? I'm trying to avoid going to a 2-speed because I want to try and keep it as simple as possible (mechanically speaking). Eventually the plan is to go to a sensored brushless setup, but I've already put more money than I wanted into this thing in a short period of time, so I figured I'd play around and do some experimenting with cheaper options. Thanks for your input!

[Bliss_RC]

Ok, so all the parts came in that i ordered, I put everything on yesterday.....and its barely any faster if at all. I guess the gear change negated any increase in speed. I'm thinking about going back to the stock gear setup to see how it runs. My concern comes with the fact that holmes hobbies reccomends the 11/68 gearing as to not overheat the motor or esc. Thats the only reason I switched up the gearing, because I didn't want to burn anything up. If I switch back to the stock gears do you think it'll be safe to run or will I risk overheating?

[slickwill16]

I have that same Holmes motor in my bomber. It is a brute. I am running the stock spur with a 16t pinion on 3s. I still have great low speed control, and enough top end wheel speed to make it fun in the open areas. I crawl and trail run with it and have had no heat issues so far. Have been running this setup for about 4 months now. Give it a shot and experiment. That is half the fun.

Sent from my SM-G950U using Tapatalk

[Bliss_RC]

Originally Posted by slickwill16

I have that same Holmes motor in my bomber. It is a brute. I am running the stock spur with a 16t pinion on 3s. I still have great low speed control, and enough top end wheel speed to make it fun in the open areas. I crawl and trail run with it and have had no heat issues so far. Have been running this setup for about 4 months now. Give it a shot and experiment. That is half the fun.

Sent from my SM-G950U using Tapatalk

Ok cool, thank you for your response! I'm just cautious because I've sunk a lot of money into this thing already and I don't want to break anything because of my own stupidity lol

[Bliss_RC]

So I switched back to the stock pinion/spur gear. It definitely made a difference! Thinking about maybe picking up a 14 or 15t pinion gear to try out.

[CoolRunning]

Essentially yes.

It's heat that is the issue here. The mod hates me talking about it but it's an issue. Brushed motors with high gearing and 3S get really hot, really quickly.

I've read so many threads of guys regularly burning out brushed motors. It`s like a rite of passage. Burn out X brushed motors, go brushless, rave about brushless. lol

Anyway, we`ve not burned out one motor. Our two crawlers have spent probably 30-50 solid hours just screaming around spinning the wheels drifting let alone all the crawling and trailing. They've been totally underwater many times and driven through creeks for hours. My Bomber motor has never gotten over about 55C even in hot Aussie weather.

The 2 speed is often available cheaply new or even second hand (you can pickup kits dirt cheap) and it add negligible weight to the Bomber. A servo is required which adds a little though going by two trucks with the 2 speed, it's a fantastic mod.

Running 2S with stock gearing with a 21T 550 motor is going to add speed (as it's ~28T) compared to the 35T stock. Adding 3S will add 50% again so you end up with a brushed Bomber on 3S that is just about as fast as a Yeti on 2S with a 3150kv brushless setup.

For a brushed crawler that's pretty cool IMPO. Brushless will add speed again but then you have to spend up getting the rig to not tear itself apart and you won't have the low down control of a brushed 2 speed rig. Not even close.

I really like it anyway. I have my Yeti and Rock Rey for the fast stuff and the SCX10 and RR10 for the slow and mid speed stuff. The crawlers get the lions share of the run time.

I`ve crawled with guys that have trucks geared for crawling and it`s pretty boring once you`re not crawling. The 2 speed transforms the truck as they can crawl like really geared down trucks on 2S and scream around like the crawlers with brushless setups.

My son and I are both careful but also reasonably abusive (watched far too many rock bouncing videos) and my Bomber is still totally stock a year later. It`s kind of amazing TBBH considering how many times they`ve fallen down rock faces and smashed into things and been jumped etc.

Originally Posted by Bliss_RC

do you mean the stock gearing will not be good for crawling, or the 68/11? I'm trying to avoid going to a 2-speed because I want to try and keep it as simple as possible (mechanically speaking). Eventually the plan is to go to a sensored brushless setup, but I've already put more money than I wanted into this thing in a short period of time, so I figured I'd play around and do some experimenting with cheaper options. Thanks for your input!

[Bliss_RC]

Originally Posted by CoolRunning

Essentially yes.

It's heat that is the issue here. The mod hates me talking about it but it's an issue. Brushed motors with high gearing and 3S get really hot, really quickly.

I've read so many threads of guys regularly burning out brushed motors. It`s like a rite of passage. Burn out X brushed motors, go brushless, rave about brushless. lol

Anyway, we`ve not burned out one motor. Our two crawlers have spent probably 30-50 solid hours just screaming around spinning the wheels drifting let alone all the crawling and trailing. They've been totally underwater many times and driven through creeks for hours. My Bomber motor has never gotten over about 55C even in hot Aussie weather.

The 2 speed is often available cheaply new or even second hand (you can pickup kits dirt cheap) and it add negligible weight to the Bomber. A servo is required which adds a little though going by two trucks with the 2 speed, it's a fantastic mod.

Running 2S with stock gearing with a 21T 550 motor is going to add speed (as it's ~28T) compared to the 35T stock. Adding 3S will add 50% again so you end up with a brushed Bomber on 3S that is just about as fast as a Yeti on 2S with a 3150kv brushless setup.

For a brushed crawler that's pretty cool IMPO. Brushless will add speed again but then you have to spend up getting the rig to not tear itself apart and you won't have the low down control of a brushed 2 speed rig. Not even close.

I really like it anyway. I have my Yeti and Rock Rey for the fast stuff and the SCX10 and RR10 for the slow and mid speed stuff. The crawlers get the lions share of the run time.

I`ve crawled with guys that have trucks geared for crawling and it`s pretty boring once you`re not crawling. The 2 speed transforms the truck as they can crawl like really geared down trucks on 2S and scream around like the crawlers with brushless setups.

My son and I are both careful but also reasonably abusive (watched far too many rock bouncing videos) and my Bomber is still totally stock a year later. It`s kind of amazing TBBH considering how many times they`ve fallen down rock faces and smashed into things and been jumped etc.

Great info, thank you! I ran around yesterday for a while on the stock gearing, running wide open for the majority of the run, and the motor didnt even feel slightly warm. Granted, its in the 30's here and theres snow on the ground...but I think if it were to be an issue it would've shown up yesterday. I did add an aluminum motor mount to help with heat dissipation so I'm sure that had a small role to play as well. Either way, I think the speed that I'm getting now is much more enjoyable than before. Its a good balance and I still have a ton of low speed control. I did order a 15t pinion gear to try out and see how that makes it act. I'll hopefully get it by the weekend and try it out and check motor temps. In the future I do plan on going to a brushless sensored setup, but until then I just plan on enjoying this thing