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  1. #1
    RC Competitor
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    Help me understand "gearing"

    Hi, I've been doing a lot of research without too much luck about gearing my Brushless Revo. Right now I'm running stock NiMH batts on stock gearing 18/65 I think? *
    BUT I ordered 6s ******* batteries for real power....*
    I've read a lot about different combinations but I'm confused at what changing the pinion only does and what does changing spur do?
    Like what's the effects on each one going up or down in teeth?
    As far as is a 54 spur faster or slower than a 65 and what generates more heat/torque etc?
    Some notes that I've made from reading others people's set ups are
    19/54 good
    24/54 faster gets hotter?*
    21/54 runs fairly cool?*
    22/58 warm
    22/62 hot

    I'm trying to make some sense of this so I can make an educated decision as to what spur pinion to try for my Revo.
    Im stock with big joe 6.39 40 series tires on 6s batteries.

    Can someone help educate me and explain as well as offer a gearing to start at?
    I'm a basher with the truck in fields, street and forest and whatever else I can find.*

  2. #2
    RC Turnbuckle Jr. 87 GN's Avatar
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    2/3s & big Joes. gulp makes for some high temps.. you will need to watch your temps closely..

    smaller spur faster
    larger pinion faster


    Diff ratio

    BrianG speed chart:
    4s = 40 mph
    5s = 50 mph
    6s = 60 mph

    http://www.scriptasylum.com/rc_speed/top_speed.html

    Import this:

    Differential Ratio: 2.8461538461538463
    Transmission Ratio: 1.8333333333333333
    Other Ratio: 1
    Spur Tooth Count: 54
    Pinion Tooth Count: 21
    Total Voltage: 22.20
    Motor KV: 2200
    Tire Diameter (inches): 5.9
    Tire Ballooning (inches): 0
    Motor Current Draw: 0
    Motor Coil Resistance: 0.006
    Spur/Pinion Ratio: 3 : 1
    Total Ratio: 15.65385 : 1
    Tire Circumference (inches): 18.54 inches (470.8 mm)
    Rollout: 1.18:1
    Total Motor Speed: 48840 RPM
    Vehicle Speed: 54.76 mph (87.97 km/h)
    Effective KV Value: 2200
    KT constant: 0.61 oz-in/A
    Would you go flip my truck back over??

  3. #3
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    That's great thanks for the help, but I still would like more clearance.
    According to the monster mamba chart running 24/54 with 6s is 65+mph.
    Because I have big joes that have a larger rolling diameter is it correct that I would not need quite the jump from my 18 to a 24 tooth pinion*perhaps?
    I would play with the chart you gave me but what exactly as far as numbers am I looking for?
    I would like to be able to reach 65mph. Not that I will but it's nice to have the option. * I also want to have enough low end torque for wheelies and bashing fun. *Can I have my cake and eat it too?
    And once I get running what is too hot and what is acceptable? Can I do a touch test? What is normal fan run times? If it comes on is that a sign of too hot etc?
    I don't have a temp gun but perhaps I should invest?*

    What is a recommended setting to try starting with. What are ppl using with 6s and big joes?
    Is the factory 24/54 too fast? *Maybe a 20/54?

    Thanks for any advice given*

  4. #4
    RC Champion
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    Perhaps,around 55mph,yes you can eat it too, 170f on the motor is getting hot,no buy a IR gun,depends on ambient temps(under 2min after stopping),no and yes.

    20/65 run 5 min, read the motor temp, run another 5 min, read the motor temp,more fun for 5 min then read the motor temp again. Do this for the whole 5s, 6s, 3s or whatever pack you use. Then do it all over again using 20/54 or smaller tires, yes too fast with the larger tires on, 20/54 would be better.

    Those temp reading results will be your beginning to understanding gearing.

  5. #5
    RC Competitor
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    Ok great so how much does an IR gun go for?
    I could borrow one probably of they're $$

  6. #6
    RC Qualifier
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    I don't have a temp gun wanted something small easy to carry in the pocket I
    So 'm using a Losi temp/adjustment screw driver it was around $25
    ERBE,Losi 8ight,Slash 4X4

  7. #7
    RC Racer
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    I got a duratrax infered temp digi meter for $25. at the lhs.Their kind reasonably priced.

  8. #8
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    The gearing u run really depends on a lot of factors. For instance, today i ran 6s onroad geared ~21/54 on road rage tires. I had no Cover on it so the temps stayed under 150*f on esc and motor.

    With a completely stock body covering up everything i would have been well into the 180*f with the motor.

    IMO A good starting spot for 6s with big joes should be around 18/54 onroad. Offroad id try 18/65 first.

  9. #9
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    Quote Originally Posted by anr2442 View Post
    The gearing u run really depends on a lot of factors. For instance, today i ran 6s onroad geared ~21/54 on road rage tires. I had no Cover on it so the temps stayed under 150*f on esc and motor.

    With a completely stock body covering up everything i would have been well into the 180*f with the motor.

    IMO A good starting spot for 6s with big joes should be around 18/54 onroad. Offroad id try 18/65 first.
    thanks for the suggestion....so question why would you recommend a 18/54 for on road, in my mind this will be slower than the 18/65 and it will have more bottom end and less top end.
    and vice versa for the off road?

    is the general consumption that offroad is harder on the vehicle and it generally runs hotter (with less speed and less cooling)
    or am i way off here?

    i DID buy a little infared temperature gun today from canadian tire, it was $25 and has awide range. it is small and pocket sized too.

    temperatures that i will be looking for would be
    anything below 150??

  10. #10
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    OK i just tested out the calculator and i think that i entered all the values correctly.
    truck is stock running on 2 ******* 3s packs. with big joe 40 series tires
    what do these numbers mean?

    with Big Joes with 18/54 gearing i got the following:
    rollout: 1.28:1
    Total motor speed: 48840 RPM
    Max Speed: 59.4mph


    with Big Joes with 18/65 gearing i got the following:
    rollout: 1.28:1
    Total motor speed: 48840RPM
    Max Speed: 49.35mph

  11. #11
    RC Turnbuckle Jr. 87 GN's Avatar
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    break it down to just the spur, then just the pinion. Meaning

    spur: smaller is faster & bigger is slower
    ========
    pinion: bigger is faster & smaller is slower


    so as you can see in your ##'s
    same size pinion for both gearing all you changed was the spur count.(number of teeth)
    your tooth count went down 11 teeth. so a smaller spur is faster.........
    54 = 59mph
    65 = 49mph
    Would you go flip my truck back over??

  12. #12
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    smaller spur and larger pinion= more speed captain
    larger spur and smaller pinion= more torque, wheelies

    Im running 14 pinion 68 spur with 6s pretty decent speeds but with in ten min i can be running at 110km

  13. #13
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    Quote Originally Posted by olliewog View Post
    thanks for the suggestion....so question why would you recommend a 18/54 for on road, in my mind this will be slower than the 18/65 and it will have more bottom end and less top end.
    and vice versa for the off road? I think the guys answered this one above.

    is the general consumption that offroad is harder on the vehicle and it generally runs hotter (with less speed and less cooling)
    or am i way off here? Onroad is a smoother surface so that equates to less resistance.

    i DID buy a little infared temperature gun today from canadian tire, it was $25 and has awide range. it is small and pocket sized too.

    temperatures that i will be looking for would be
    anything below 150?? Well... The fan comes on at 150*f so thats a tell tale of the escs temp. I will say.. For 6s and Big Joes keeping it under 150*f will NEED a fan on the motor and a couple of holes cut out of the back/front windshield.
    Hope that helps
    Last edited by anr2442; 02-19-2012 at 07:50 PM.

  14. #14
    RC Turnbuckle Jr. 87 GN's Avatar
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    Quote Originally Posted by savge4404 View Post
    Im running 14 pinion 68 spur with 6s pretty decent speeds but with in ten min i can be running at 110km
    that is 33.82 mph, 48,840 rpm, & Spur/Pinion Reduction Ratio 4.86:1

    Geared way to low, what are the motor & ESC temps..
    BrianG speed chart:
    4s = 40 mph
    5s = 50 mph
    6s = 60 mph
    Would you go flip my truck back over??

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