Results 1 to 9 of 9
  1. #1
    RC Racer
    Join Date
    Jan 2014
    Location
    Irvine, CA
    Posts
    142

    Question Need help to understand pinion / spur gearing.

    I have a Tekin Pro4HD. I'm reading a lot and I'm seeing 41/16 gearing. What does this mean? 41 Pinion
    16 Spur? What pitch should be suggested?

    Appreciate any help.

    I will be racing indoor clay.

  2. #2
    RC Turnbuckle Jr. O.G.'s Avatar
    Join Date
    Nov 2010
    Location
    South of St Louis
    Posts
    6,369
    The pinion is the small gear, spur is the larger. Making a single tooth change on the pinion has a bigger impact on gearing than one gear on the spur.

    Mod .8 pitch is generally more popular on 1/10 trucks than other gearing. Keep in mind you'll have to match the two gears pitch-wise or they won't mesh.

    16 refers to the pinion, 41 to the spur. On this forum we put the pinion first so you would express it as 16/41.
    Last edited by O.G.; 03-25-2014 at 09:10 PM.
    My Black & Blue Rally is faster than your color...

  3. #3
    RC Qualifier
    Join Date
    Dec 2013
    Posts
    329
    pinion is the small gear attached to the motor while the spur is the big gear. when the numbers are closer together it will be fast but less acceleration and farther apart numbers will decrease top speed but with good accelration. i run 18/54. i sued to run 13/54. 18/54 increased my top speed by about 5mph im guessing.

  4. #4
    RC Qualifier
    Join Date
    Dec 2013
    Posts
    329
    i think 16 would be a good pinion for racing.

  5. #5
    RC Champion thesmogman's Avatar
    Join Date
    Oct 2013
    Location
    Dublin, CA
    Posts
    1,246
    Hi Erik, I am running the Tekin pro4 4000kv with a 15/50 with 2c lipos. I also have a Rx8 gen2 but when I ran this motor with the stock system I ran 15/54 for racing this is! Indoor clay med/small track

  6. #6
    RC Competitor
    Join Date
    Jan 2014
    Posts
    70
    Gear ratios are the balance of speed vs torque. If you want to compare different gear combos you divide the spur by the pinion to get the ratio. Stock is 54/13 = 4.15:1. Your proposed gearing is 41/16 = 2.56:1. You can compare the 4.15 to 2.56 to see the difference. In this case your proposed gearing would be roughly 1.5 times faster than stock, but would also work the motor 1.5 times harder (more current and heat).

    There really is no right answer only a range of what your motor can handle. The car will have the highest top speed if you use the smallest ratio that will not overheat your motor, but you may not always want that. If you are running someplace with many tight turns it may be better to trade top speed for acceleration out of corners. This is a series of trial and error.

    The math to figure out the top speeds for different ratios is listed below. This is not exact because it ignores things like how much power your motor can actually produce, car weight, aerodynamic drag, etc. It is still useful to give you a general estimate to make relative comparisons on the same car. For example if you put bigger tires on you can possibly get x% more top speed.

    Code:
    Spur / Pinion * 2.85 Slash 4x4 Diff Ratio (this can vary for different cars) = Final Drive Ratio
    
    Tire Diameter in inches * PI = Tire Roll Out in inches
    
    Motor KV * Battery Voltage = Motor RPM
    
    Motor RPM / Final Drive Ratio = Wheel RPM
    
    Tire Roll Out * Wheel RPM = speed in inches per min
    
    Inches per Min * 0.000946969697 = Miles Per Hour
    
    -------------------------
    Example for 13/54 with 3300KV Motor on 2S with 4" tires:
    
    54 / 13 * 2.85 = 11.83 
    4.0 in * 3.14 = 12.57 in 
    3300KV * 7.4V = 24,420 RPM
    24,420 RPM / 11.83 = 2064.24 
    12.57 in * 2064.24 RPM = 25947.5 in/min
    25947.5 * 0.000946969697 = 24.57 MPH
    
    -------------------------
    Example for 16/41 with 3300KV Motor on 3S with 4" tires:
    
    41 / 16 * 2.85 = 7.3 
    4.0 in * 3.14 = 12.57 in 
    3300KV * 11.1V = 36,630 RPM
    36,630 RPM / 7.3 = 5017.81
    12.57 in * 5017.81 RPM = 63074 in/min
    25947.5 * 0.000946969697 = 59.72 MPH

  7. #7
    RC Qualifier
    Join Date
    May 2013
    Location
    Uk
    Posts
    742
    Great piece of info geek.....that's is the best way to work out your pinions and spur combination...

  8. #8
    RC Turnbuckle Jr. billy-bones's Avatar
    Join Date
    Nov 2012
    Location
    Michigan
    Posts
    8,205
    Thats nice G,W but I use this sight as my brain tends to start smoking when over taxed
    http://scriptasylum.com/rc_speed/top_speed.html
    Built Ford Tuff With Chevy Stuff.

  9. #9
    RC Qualifier
    Join Date
    May 2013
    Location
    Uk
    Posts
    742
    Billy.....holy smoking brains.....what an amazing web site...that's brilllllllllllllllll....

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •