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Gears, pinions and spurs

Discussion in 'Chassis & Drivetrain' started by Aflan, Jul 13, 2015.

  1. Aflan

    Aflan Well-Known Member

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    I don't understand anything...Could somebody give me a good 1 on 1 crash course?...

    The thing I would like to do to my Mojave is to give it more power and a bit less speed...
     
  2. Walter

    Walter Well-Known Member

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    Check out the below thread. Especially the chart in the linked post.

    http://arrmaforum.com/threads/anyone-changed-the-gearing-on-arrma-granite.75/page-2#post-1100

    Basically, divide the number of teeth on the spur by the number of teeth on the pinion and with the resulting number the lower numbers will give more torque and less top speed and the higher numbers will give less torque and more top speed. Gearing down (lower number) will also typically give lower temps on your motor/esc but it is possible to gear too low which can increase temps.

    Hope this helps some.
     
    Aflan and Blxer like this.
  3. Aflan

    Aflan Well-Known Member

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    Its another step...Thx for the info Walter... :)
     
  4. Darren Wes

    Darren Wes Well-Known Member

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    From what i know this is how gearing goes... only going to change pinion and spur gear

    First thing you have the drive lines coming from the outdrives to axels and hexes and wheel....make sure you didnt put the wheels on too tight and bearing are greased and free no its as smooth as posible.

    Next you gotta decide why you are changing (heat issue, speed, torque)

    Know what you are running for a motor
    2-pole-vs-4-pole-motor.jpg
    Because of the efficency 4 pole will create more low end torque. 2 pole motors are very much like stock, but a for sure upgrade for first time (looking back i would have saved time and money just staying 2 pole!) 60a esc and 2 pole are fine but 4 pole needs more amps and 60 is right n the line.

    Next...the meats
    So torque is the easiest...need some add either a larger spur(slower) and or smaller pinion (slower) you are trying to "legnthen" gears

    Speed is next...easy way add a smaller spur(faster) or a larger pinion(faster) the idea is trying to make them "shorter"

    Here is a pic of a normal traxxas 2wd this is considered tall gearing
    (This is might not be stock but looks tall enough)
    IMG_20120722_225217.jpg
    Here is a pic of a speedster traxxas 2wd
    This is considered short gearing (this is acctually a 1:1 gearing maybe called somthing else but for learning call short)
    RustlerGearingModded27.jpg
    Notice that the spur is small and the pinion is huge(seen other variations just found this first)... this is 100mph+

    Tall gearing is best for climbs, trails, being all about that torque

    Short gears are best for speed...

    If your system is running "ok" you wont have to change much just go a tooth up or down for whatever you want to do

    Heat is next thing in gearing!
    comfortable ranges after you have desired results from spur and pinion choice
    Motor~120-150° farh. (180+ will start to degrade your motor)
    Esc~110-130° (about 140 heat cutoffs come in, and where im having issues at)

    Easiest was to describe whats going on with heat issues

    Hot motor + cool esc = under geared
    Cool motor + hot esc = over geared
    Everything warm just right
    (Should help as a general)

    Have heard that 1 tooth change on pinion can change temps from 5~10° farh.
    And 1 tooth on spur can change from 1~2°

    You can also get heat from drawing too many amps. This is what walter was talking about "lower speed high temp" (seems to be a 4 pole problem, but could happen woth a 2 pole) also not using a fan on the esc (or larger esc) and motor both (sidekick: if both fans are being powered from the same place you need to install a bec!)
    If you draw too many amps youll get heat too and your esc will act funny and glitch. You can draw too many amps by having either having a esc that cant handel the power of the motor or your pinion/spur ratio is so off the motor is not using all the energy sent to it (too tall)

    This is because of some form of a reverse feed (like static on cable television) the motor isnt going fast enough to displace the current provided by the ESC and the extra energy is sent back causing line static and heat. This can fixed by adding a larger pinion (or smaller spur) "shotening" so that the motor uses more energy(motor will get hotter and faster and loose some torque) thus cooling the system by converting unused energy to more power. (Note: this usually is only the case with a new powerful motor on stock gears or during a change from crawler to racer)

    if the desired result isn't working out because you cant get enough torque without heating up the esc too much from the tall gearing you may need a new/different 4 pole style motor and esc to work it so you can get mudding

    If the desired result isn't working because you cant get enough speed and shortening the gears are causing too much heat you'll need to look at maybe a higher kv motor maybe more voltage. start with stock gearing and voltage again and work up into it

    If heat issues are still happening after testing in a semi scientific way, adding fans , and gearing down first and gearing up. You may need to talk to someone in person because somthing is probably failing.

    Rewireing your truck will also help on your final gear choice...less cabels less heat less mess

    So. Gearing goes from your tires up...make sure your drivelines are good know your system and what you may want to accomplish

    Finally get the right stuff and know what you choose can be undone and changed if it doesn't work, maybe just a tooth lower pinion that fits on the motors shaft, maybe a larger esc larger pinion and small spur, or even a small change just by changing the spur for fine adjustments....
     
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  5. Aflan

    Aflan Well-Known Member

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    @Darren, wauw, thx...I am getting to understand it now...Thx again...
     
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  6. Darren Wes

    Darren Wes Well-Known Member

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    No problem... was bored and wanted to help. Its not the end all of gearing but enough to get you moving... tire size chocise plays a big part, hear ceramic bearings play a big part, also weight.... you know

    Btw i could use some suggestion...
    So i have a mega with stock gearing (15/87) and when i switched to a 2 pole motor i really didnt need to change anything.. (felt as if i could gear up to bls 18/87 but didnt)

    Now i have a 4 pole (like blx) and am getting esc heat issues

    Should i try and gear it like a blx to start testing (since im kinda building up to it) or stay stock and start there

    Right now after 15 min my motor is ambient temp and my esc is around 150

    Which way to start?
     
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  7. Aflan

    Aflan Well-Known Member

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    With my limited knowledge I would say start with BLX type of set-up...But perhaps there's some one wiser about this subject who can advice you...;)
     
  8. Darren Wes

    Darren Wes Well-Known Member

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    Went to the shop. Said that the esc cant really handel the 4pole on 3s so thankfully I was already prepared and have an 120a esc on the way. Said the stock gears are ligit. So by next weekend I should have a fully functional truck and a full blx transformation in the next couple months
     
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