who can explain gearing?

[04zrx]

So I recently bought two new brushed (1 Brood 21t and a 27t Holmes Torquemaster) motors for my Crest. I don't want to burn them up but want to get as much wheel speed as possible. If I understand things correctly impropper gearing is the best way to burn up motors. I have 2s,3s and 4s to use, what fun! My esc is a BRXL and I'm running Mayham 2.2 wheels with Irock tires.
Thanks for helping point me in the right direction.

 

[04zrx]

...then there is pitch. does that really matter? I don't know that it does, I'm thinking it is much more about ratio.
What is the Ridgecrests gear ratio any way?

Yah know something, it might have more to do with running it full throttle than the gears, help !!

 

[JeremyH]

...then there is pitch. does that really matter? I don't know that it does, I'm thinking it is much more about ratio.
What is the Ridgecrests gear ratio any way?

Yah know something, it might have more to do with running it full throttle than the gears, help !!

Of course pitch matters. 48p will have smaller gears. Personally, I prefer 32p.

With those low turn motors, I would run as large of a spur and as small of a pinion as you can get. Probably somewhere around a 5:1 ratio....

 

[04zrx]

so your saying that ratio is what matters. In terms of pitch 32 p should hold up better less chance of stripping out?

 

[Solitaire]

Ratio will determine motor longevity (among other things) and pitch will determine gear strength. 32P is much stronger, but also quite a bit noisier.

 

[JeremyH]

Bah, you won't notice any extra noise with 32p....especially with a delrin spur.

 

[isyeskeert]

Rock beats scissors, fun beats noise! Rock on!

 

[Solitaire]

Bah, us Canucks just have better hearing than you Texans.

 

[04zrx]

noise isn't an issue since it will not be right next to me... Loud is GOOD!!! "what?"

 

[04zrx]

Ratio will determine motor longevity (among other things) and pitch will determine gear strength. 32P is much stronger, but also quite a bit noisier.

so if I gear down I'll be full throttle more often...heat...burned up motor? Full throttle is bad no matter what?

 

[gottorque]

so if I gear down I'll be full throttle more often...heat...burned up motor? Full throttle is bad no matter what?

RC's are not light switches. Use that ESC and modulate the throttle, roll into the power and don't do too many high powered launches...that will save your motors

Sent from a rock

 

[04zrx]

RC's are not light switches. Use that ESC and modulate the throttle, roll into the power and don't do too many high powered launches...that will save your motors

Sent from a rock

What... not light switches? You mean to tell me It isn't on or off, this is very confusing to me :shock:

 

[JeremyH]

He was saying that the throttle is not full throttle or full brake...that it is a variable speed.

 

[K-Note72]

Throttle control is a virtue. It can be the difference between longevity and a trashed motor/gear/shaft. My ax-10 is brushless so i set it under 80% max throttle and moderate drag brake.

 

[bigstu]

You have to think about gearing this way.
When you gear something down (12t pinion and 97 tooth spur for exanple) the mechanical advantage of the gearing multiplies the torque and allows you to put more to the tires.
Increasing the gearing, or gearing up (18t pinion and 87 tooth spur for example) reduces the mechanical advantage and makes the motor work harder (A.K.A. draws more power from the batteries).
Any time you make the motor impart more work, it pulls more power in the form of amps and makes heat. Heat makes resistance which draws more power, which makes more heat, which draws more power, and so on...
Having a motor at 100% throttle isn't necessarily a bad thing, as long as it is geared properly.

First things first, pick a combination and stick with it. With two motors and three different battery packs, you can't possibly gear the car for all those combinations.
Those motors are going to be very different and you're only going to smoke one of them if you constantly change batteries and motors.
So pick a combination and stick with it. My suggestions would be the 27t and 3s. Just my $.02 worth though. I like to crawl, sounds like you are in for high speed...

Here is my suggestion on how to tune the gearing on a motor. I learned by burning up a couple brushed and brushless motors.

Start LOW. 12-93 to 15-93. Do a typical run. While running the vehicle, use an IR Temperature gun. Something like this.
CE Compass Temperature Gun Infrared Thermometer W/Laser Sight - Tools - Electricians Tools - Multi-Meters & Meters
Through the run check the temperature. When it gets up to about 130-140 it means you are getting close to the limit of your gearing.
You can also use the finger touch method, if you can touch the motor with your finger and count to 5, slowly, you're good on temp..
I'm an engineer, I like the temp gun.. SO, If you only get to 90 degrees through the entire run, gear up a little more. Move from 14-93 to 14-87 and do the same thing.
Gears are cheap. Pick up a few and try some combinations. Let it completley cool down between runs and run it under the same conditions each time.
Remember, if you gear it for running at high speeds on cement, and then use the same gearing to go rock crawling or hill climbing, you're going to be risking a smoked motor.

Hope this helps. Good luck. And don't be afraid to spend some time and read. See what others are doing and if they smoked a motor, you know what not to do..

 

[04zrx]

Bigstu: thanks, you have some knowledge to back up your answer. I ( noob ) didn't realize that is was that delicate of a thing. Part of my problem is that I'm trying to run with my friend and he has a p4de. Can you point me in the right direction for buying gears? What pitch should I use, do most spur gears bolt up to the Axial? I truly don't want to smoke a new motor so all this info is good, thanks. I did buy a ir thermometer to check temps with.

thanks!

 

[bigstu]

There are specific spur gears that will bolt up to the axial trans.
I usually go with Robinson, personal preference.

This is a REALLY good place to start reading.
http://www.rccrawler.com/forum/axial-wraith/346212-choosing-motor-esc-your-wraith-gearing-added.html

I know you don't have a Wraith, but the trans and axles are exactly the same. Your truck should be a little lighter than a Wraith, so you may be able to go a little more agressive on the gearing.
There are a lot of combinations described in that article.

Here is my $.02 worth on where you could start with gearing.
For crawling and or using a big brushless motor, 32 pitch gears are the only way to go. They take the abuse. Simple enough..
For higher speed, not so much crawling, I like 48 pitch gears. Even in my FOFF truck, with a brushless set up, I was running 48 pitch gears.
To be honest, they were smoother and I liked how it worked.
The wraith guys, with a 27t motor are going for a 56/12 32p combo. 56t spur, 12t pinion, 32 pitch gears.
If you want to stick with the 48 pitch gears it looks like guys are starting with 87/14 and working up from there.
Again, these are just the info I have on hand.
Give it a try, get your temp gun out, and see what happens.
Gearing isn't overly delicate, you just need to start conservative and work up from there.

 

[redsawacs]

something to keep in mind, AXIAL builds their vehicles with a lot of gear reduction. If you want to go faster, you'll have to really address the gearing. Consider the front and rear diff gears as a place to get a little more "wheel spin".

simple reminders.....
Gear on motor = pinion gear. Gear on transmission = spur gear.
Small gear on motor and big gear on transmission= torque and low speed
larger gear (than stock)on motor and smaller gear (than stock)on transmission = top end speed and low torque
high turn motor yields higher torque and less speed
Low turn motor yields higher speeds and less torque
Torque is strength...you need enough torque to get the vehicle moving and keep it moving so a really low turn motor may not have enough strength to even turn the wheels. Conversly, too much torque (high turn motor) will top out and simply leave you "wanting".

Add the gear issue on top of all this - SO MANY CHOICES!!!! UGH

 

[04zrx]

something to keep in mind, AXIAL builds their vehicles with a lot of gear reduction. If you want to go faster, you'll have to really address the gearing. Consider the front and rear diff gears as a place to get a little more "wheel spin".

simple reminders.....
Gear on motor = pinion gear. Gear on transmission = spur gear.
Small gear on motor and big gear on transmission= torque and low speed
larger gear (than stock)on motor and smaller gear (than stock)on transmission = top end speed and low torque
high turn motor yields higher torque and less speed
Low turn motor yields higher speeds and less torque
Torque is strength...you need enough torque to get the vehicle moving and keep it moving so a really low turn motor may not have enough strength to even turn the wheels. Conversly, too much torque (high turn motor) will top out and simply leave you "wanting".

Add the gear issue on top of all this - SO MANY CHOICES!!!! UGH

I hear yah! Good reminders thanks. I am looking for speed (wanna stay brushed) but want longevity also. I'll run cautiously at first till I figure out heat issues. I'm headed to the LHS tomorrow so I'll get some more gears to try.

 

[04zrx]

update: so yesterday I got my new gears in. I ordered 90t and 93t 48pitch gears I also have several new pinion gears. The gearing that led to my motors demise was 87/16. I installed 90/ 12 for starters and that worked well. I first ran it that way on 2s just to stay on the safe side and speed suffered but almost no heat build up"thumbsup". Then when I was feeling confident I installed 3s. Installing 3s got me the speed I was looking for, and Still no heat build up, this is all good!!! The thing that I need todo is change the drag break on the speed controller I want it at like 50% so it doesn't do an endo when I stop:shock:. I crawled on the rocks and the drag break is awesome! but when bashing I'd like to not have it so strong. I do have the field programmer so I'll be able to adjust it. I haven't tried to figure that all out yet...
It amazes me that there is almost no heat build up, even on 3s, I was not easy on this rig (I never am...) last nite but changing the gearing didn't make me loose speed and there is almost no heat. I used my ir thermometer and got readings of 92 that is all good. Hopefully this is exactly what I need if I can run this like this I have plenty of speed and a motor that lasts for a long time....
HAPPY BASHING!