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Gear for motor and battery question

Old 05-21-2020, 10:56 AM
  #1  
bline22
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Default Gear for motor and battery question

Hello,

My son has a car he has been building and we are at the point where we noticed the motor did not come with a gear for the end of the motor. What type of gear do we need? The car he has is the following: PR S1 V3 FM SPORT 2wd Buggy kit

Here is the motor:
Hobbywing XR10 Justock Sensored Brushless ESC/SD G2.1 Motor Combo (17.5T)

Also, we noticed that the Engine controller does not have ends to go into the lipo battery it is just bare wires. I would guess I need to crimp or solder something on here?
Battery:
HobbyStar 3700mAh 7.4V, 2S 100C Hardcase "Shorty-Lite" LiPo Battery

Thanks for the help
Old 05-21-2020, 05:02 PM
  #2  
seedygreenute
 
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Yes , you will need to solder on a plug .
The one I googled had a " Deans " connector / plug on the battery . ( red T shape ) .
The battery will be the female side so the tabs are not exposed and able to short out .
The website for the car showed the pinions but a quick look at the manual didnt show anything .
It showed them as 48P .
This is the gear Pitch ( the size of the teeth ) .
Motor shaft should be 3.17mm ( 1/8" ) .
These are a common size , and available online or at your local hobby shop .
81 tooth spur gear , if I read the manual right , so some where about 20 Teeth would be a starting point . You can get gears individually or sets ( eg 5 gears from 17T - 21T ) .
If Bill jumps on , listen to him ! He is a very technical racer and will help with your setup .
Old 05-21-2020, 05:27 PM
  #3  
bill_delong
 
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The user manual for the motor you bought provides you with the recommended gearing here:
2-HWA38020241%20Hobbywing%20Justock%203650%20SDG2.1%20Manual.pdf



The manual for your buggy provides the information for the drive ratio on pages 11-13:
PR RACING

Gear Diff = 55T
Top Shaft = 20T
IDR = 55/20 = 2.75

Spur = 81T
Pinion = x

FDR = 2.75 x (81/x) = 6.0 = recommendation by HobbyWing

x = (81 x 2.75) / 6 = 37T pinion

Only problem is that you can't fit a 37T pinion so you'll need a smaller spur to get proper stock gearing, I don't run 2WD so I don't know for sure, but I would probably go with a 73T spur so the math would go like this:

x = (73 x 2.75) / 6 = 33T pinion which should fit

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