View Full Version : How to dyno a BL system
OptimaMan
03-04-2004, 10:30 PM
Hello guys - we all need to figure out a way to dyno a BL system. So, we *can* have a way to directly compare one brushless motor to another in a simple cheap practical way.
Here's what I was thinking:
Run a motor with an airplane propeller and measure the RPM with a tachometer. Plot out a chart of RPM vs. wattage input.
So, by knowing how much power (RPM) is coming out vs power in, I can figure out relative efficiencies at different RPMs vs. different motors.
What do you think, drawbacks? Limitations of the system? I know there are a LOT of limitations, but I figure this would be a nice rudimentary "dyno" of sorts so at least I can compare the motors.
Would anybody be interested in the results?
How bout making a set of rollers for the front and back wheels. That way you get a real close loaded motor performance. Then measure current draw from the batts to the controller, while actually running the motor in a car.
Just a thought.
havy
http://www.land-and-sea.com/images/dyno/auto/chassis/model_rc_car_on_chassis_dyno_600.jpg
DFF
OptimaMan
03-05-2004, 09:44 AM
I just called them up - they don't actually make that dyno. One of the customers made it for personal use.
I didn't know, that's an old link I had in my computer...
Otherwise, I do remember seing something similar like a dyno for Monster Truck, based on the same roller principle.
DFF
yep I've seen that one at my LHS. The rollers look like the ones used on maual convayer belt to unload boxes from trucks at the grocery store (only no belt, just rollers). I'm sure those type rollers should be readily available, just got to construct a box to position them at the right length.
2 rollers per wheel w/ the wheel resting between the two.
havy
billmck
03-05-2004, 06:46 PM
maybe putting a belt on would help out more to simulate things like: take off amp draw, off throttle and breaking responce, etc. just strap it down and yor're set. heck maybe even find a way to load up some resistance on the belt for other testing.
bill
scrubnick
04-25-2004, 04:42 PM
How about a constant force dyno? Have the motor run a fluid pump with an adjustable valve to apply a load. Then, use a hall effect sensor to measure RPM and a strain gauge to measure torque. That's the setup we use in the engineering lab.
glassdoctor
04-25-2004, 11:55 PM
You could do just like the airplane guys, with a prop like you suggested. That seems easy enough and there a replenty of guys experienced in doing it this way to get any help you need.
My guess is that you probably want an oversize prop to simulate the higher torque strains in car instead of looking for a constant efficient setup like airplanes need. Trial and error there I'm sure...