Laser photo tachometer arrived, playing around with it

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Well, the postal carrier came and left without leaving me an ESC + servo tester, so I still can't install the HXT outrunner. But, she did leave me a little package from Hong Kong that contained the laser photo tachomoter that I ordered from ebay. I'm still amazed at just how cheap Chinese manufacturers are pumping things out. A laser tach would have cost me over a $100 just a few years ago, now I can buy one for $23 w/ shipping from Hong Kong. Incredible.

The quality of the unit is quite good. The laser beam is nice and coherent with minimal spread. The unit is sensitive enough that I could do my motor readings using some duct tape rather than expensive retroreflective tape (that they kindly include a small sample of with the unit).

This will be lots of fun.

Anyway, I went ahead and did some motor speed readings on my Boxer to check out my gear ratios. This is with the back wheel raised on the center stand (no load test):

Motor spindle speed / front hub speed: 3272 rpm
Rear spindle speed / flywheel speed: 2091 rpm
Wheel speed: 168.8 rpm (14 mph)

Motor amp draw was 5 amps, so close to no load. From this, I can see that my motor to wheel ratio with the 1.5" front sprocket is 19:1 rather than the 39:1 calculated by using the gear ratios (I think there is another gear inside the flywheel that I didn't consider). When the motor is at full speed, the wheel is going at 14 mph.

Anyway, I'm glad I got the tach since it's telling me the real motor:wheel ratio rather than the calculated one, which was always a bit iffy since I had a centrifugal clutch and could never test the entire system.

For $23, the laser photo tach is definitely a good buy and it'll be even more useful when I get the HXT mounted and have a variety of volts and amps combinations to play with with the new controller.


After zapping the moped with the tach a couple of times, I decided to take it out for another spin. Seems like the battery is coming up to speed after a couple of charge/discharge cycles as I was able to get 5.0 Ah out of it today.

Trip distance: 5.3 km (3.3 miles)
Moving time: 26 minutes
Moving average: 12.2 kph (7.5 mph)
Max speed: 18.3 kph (11.1 mph)

Total energy: 5.0 Ah
Total Energy: 0.11 KWh
Peak amps: 22.14 A
Min voltage: 21.05 V

km / kWh: 48 km / kWh (30 miles per kWh)

I have some NiMHs on order, I can't wait until they arrive too! Running on two 7 Ah SLAs stinks!

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About this Entry

This page contains a single entry by Karen Nakamura published on July 19, 2008 7:29 AM.

Boxer Test Run 1 (250 watt Razor MY1016; 30a controller; 24v 7 Ah SLA) was the previous entry in this blog.

Servo tester and Smart Temp arrived is the next entry in this blog.

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