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Razor PR200 Drivetrain (Stock)

This includes the specification on the stock parts and research on alternatives.

Motor

Stock Motor
Model Zhejiang Unite Motor Co. Ltd. #MY1016
Type Brush
Voltage 24 Volt DC
Output 250 Watts
Efficiency ≥78%
Rated Speed 2750 RPM (3350 No-Load)
Rated Current ≤13.4 Amps (≤1.6 No-Load)
Rated Torque 0.90 N-m
Sprocket#25 Chain, 11T
Body Dia/Length 101 / 108 mm (4 / 4-1/4")
Shaft Dia/Length 10 / 26.5 mm
Mount Points 4-1/4" x 2-1/8", 4x M6x1.00 [Detail]
Weight 2660 g (5.86 lbs)
DC Motor Formulas
Power V x I x EFF
Horse Power(V x I x EFF)/746
Current P/(V x EFF)
Efficiency (746 x HP)/(V x I)
  • V = Voltage
  • I = CURRENT (amps)
  • P = POWER (watts)
  • EFF = Efficieny
  • HP = Horsepower

1 Watt(w) = 1 N-m/s or 0.738 Ft-lbs/s or 1.341E-03 hp
1 Horsepower (hp) = 746 Watts or 550 Ft-Lbs/s

check the internal resistance of your motor by DMM(ohms)across the two input wires. V/R = stall current (maximum current you can push through it at a particular voltage)


It looks like the 36V 350W Unite MY1016 motor is the biggest that is a straight bolt-on. It's specs are nearly identical except for the 1.22 N-m of torque (136%). Bigger motors (MY1020) should fit but, you'll have to drill new mount holes and make a spacer (~1") because they're too long to fit between the frame rails. The bigger motors are a better use of your money.

Motor Links

Gearing

Stock Tire: 3.00-4 (10"x3.5" / 260x85mm)
Tire Circumference:800 mm (0.0005 or 1/2000 mi)
Stock Gearing: 11/65 (1:5.91)
Stock Chain: #25 Chain, 126 links

#25 Gearing available from tncscooters.com: 11-15/55,65,68,72,80

11/551:5.00 12/551:4.58 13/551:4.23 14/551:3.93 15/551:3.67
11/651:5.91 12/651:5.42 13/651:5.00 14/651:4.64 15/651:4.33
11/681:6.18 12/681:5.67 13/681:5.23 14/681:4.86 15/681:4.53
11/721:6.55 12/721:6.00 13/721:5.54 14/721:5.14 15/721:4.80
11/801:7.27 12/801:6.67 13/801:6.15 14/801:5.71 15/801:5.33
MPHWheel
RPM
Motor RPM*
1:5.91
(11/65)
1:500
(13/65)
1:4.33
(15/65)
1:3.67
(15/55)
1:3.06
(18/55)
10 3321,9621,6601,4381,2181,016
15 5002,9552,5002,1651,8351,530
20 6673,9423,3352,8882,4482,041
25 8334,9234,1653,6073,0572,549
301,0005,9105,0004,3333,6703,060
351,1676,8975,8355,0534,2833,571
401,3337,8786,6655,7724,8924,079
* Depends on gearing.

Running the stock 24-volt, 250-watt, 3000 rpm motor at 36-volts got me to about 22 mph at 4,326 motor rpm. This leads me to believe that getting to 40 MPH may be difficult. Even with the tallest gearing available from tncscooters.com (15/55) we're looking at 4,892 rpm but, 35 mph would be a do-able 4,283 rpm based on this single reference point.

Mr. Exon claims to have hit 40 mph but, forum posts show him and others using a 34" (864 mm) wheel circumference based on his math that a 10" tire x pi = 34" (dπ=c) instead of 31.4". Assuming that he never caught that math error then his actual speed was closer to 36.9 mph. Whatever his actual speed was, it does tell me that it is possible to get 150% of the rated rpm for a motor and that the tires probably will not immediately disintegrate at 35-40 mph.

#25 Gearing Links:

Chain

The PR200 comes with a 126-link ANSI #25 chain stock. Generally speaking you would want to add/subtract links as you add/subtract teeth on your gearing but, you may be able to compensate for a few teeth with the chain adjusters on the rear axle.

Other small electric vehicles may use a T8F chain which I've also included in the table below for reference.

SizeStandardPitchRoller diameterTensile strengthWorking load
25 ANSI B29.1 / ISO 6061/4" (6.35 mm)0.130" (3.30 mm)781 lb (354 kg) 140 lb (64 kg)
T8F  5/16" (8.00 mm)0.180" (4.70 mm)2,293 lb (10.2 kN) 

Tires

Stock Tires
Brand Qing Da (Razor Branded) Street Treaded Tire
Size 3.00-4 (10"x3"x4", 260x85)*
Type Requires Innertube
Ply Rating (PR) 4
PSI 45
Load 264 Lbs under pressure
Overall Diameter254 mm
Section Width 86 mm
Certifications ECE E4 (vs DOT)

Tire Circumference: 800 mm
Theoretically, a 10" or 260mm tire would have a 797.6 mm or a 816.4 mm circumference respectively. I measured the circumference at 800 mm (within, say, ± 2 mm) and used this number when configuring my speedometer.

Tire Size*: 10x3x4 or 260x85
1st number is the outside diameter of the tire, the 2nd number is the overall width and the third number, if used, represents the inside tire diameter, or the outside diameter of the rim.

Speed Rating: Unknown


My initial searching suggests that your two options are the stock Qing Da tires or Kenda's as an alternative. Neither brand lists a speed rating but internet reports suggest that the Qing Da's can handle at least a few moments at 35-40 mph.

Tire Links:

Tire Speed Ratings: A5=16mph, A8=25mph, B=31mph, D=40mph, F=50mph, J=62 mph

In memory of Speedshop  LP Privateer  LP Racing  Aftershocks  Pirelli

January 25, 2012