@Mellow Thank you for the support. In a product oriented community, its not often that we get support in development/pioneering a project, since its easier for people to criticize and throw money at problems.
So guys, its clear that we need a half decent bench testing solution we can all reference. Laser Cut aluminum or CNCed aluminum frame dynamometer. We need a community effort to build one for BLDC testing.
Boosted’s in house Dynamometer from their early days:
Preliminary VESC Based Dynamometer (DATED, but useful):
With the VESC 6.0, we can have higher resolution data from the motors we use in testing. While we wait, lets consider the best way to test motors by considering how to BUILD a rig for hub motors. We could build a custom can/rotor that connects to the shaft, but thats additional milling for every motor. A Wheel-to-Wheel test might work, but we have mechanical losses. I’m pretty good at AutoCAD and Solidworks, but I need someone to do the mechanical engineering here to reduce losses. Anyone with me? If so, PM me. Otherwise, I’ll create a new thread about a community driven Dynamometer.
I’m in but let’s keep all open, and I can help on the mechanical part
In my opinion the better aproach to be cheap and easy and to make is to use friction, a bike disc brake and caliper, a load cell taken out os a cheap scale or bought, an arduino and we are done
The vesc send info to the arduino, same for the load cell, with that info we can make a simple mechanism to apply brake, that can be manual or servo driven, on the latter we can make a routine to automatically generate a torque/current/efficiency curve
I think a generator would be better. It will be hard to use a disc brake as sort of standard.
You want a well defined and measurable resistance. You need to know the output power to measure the efficiency. If you know your generator it’s easy to straights out the numbers. Define a cheap generator everyone has access to and standard is set.
Mechanics should be easy to sort out. Some alloy and wood…
The programming will be quite simple, seen in the image bellow, we just have to test how stable is the torque using the brake
The test will be completely automatic and will generate in one run torque vs speed vs efficiency
I’m just a bit worried if the brake disc will end the test on a acceptable temperature, I think a big fan pointed at it will be needed and incorporate cooling time and stabilization time, or in another aproach, make each measurement so quick that it don’t have time to heat up, Just have to check if the data is stable in short periods or if we will have to round and filter it over a period of time
The disc brake doesn’t matter, what we need is the torque that it generates, so the load cell matters, but that can be easily calibrated using a portable dynamometer, the ones used to tighten bolts
Is the stator on your website the same one that’s in your motor or is that just a dummy stator with unrealistic pole count and such you used to camouflage your design?
This is how a hub motor should behave. It’s only taken a few months of simulation to get here. With a 4WD setup, less heat is generated per motor when starting so the temperatures tend to stay pretty cool. Practically, the thermal results indicate you wouldn’t want to push more than 1.5 hours of riding time and definitely half that if you’re going up hills constantly. Two motors aren’t strong enough and wouldn’t stay cool under those conditions with 100kg of human… Looking at the data, I wonder how close these results are to the specs from the Action Blink Quatro.
Easy to replace stators/inexpensive recycling or rewinding would be a victory.
And what about a forced air cooling? I think going 4wd is a major drawback that most people, incluindo me, would not do
But sure that flat torque curve is pleasing
The loses are linear with torque? Maybe you could could run the simulation with 1/2 and 1/4 of the current just tô see what we get, in the average course you would never be using full torque constantly
I noticed that the torque versus grade that you are using are significantly higher than what I calculated(80mm wheels 90kg person and taking in account aerodynamic drag)
Isn’t it that the cooling effect get’s stronger the higher the temperatur difference is between the motor and the air. Because it seems that this isn’t taken into account in your graph.
@Pedrodemio, I want the motor to achieve kick ass at 75%, not 100%. This is going to make the motor survive for longer and perform better. More head room.
@Ackmaniac, It is, but I can’t calculate forced air Coolings efficiency for something this small. It would have to be measured, not calculated then included in the simulation. I do not know how well ventilated my rotor will be since I am still playing with cap designs. I am limited by the 5Axis CNC mills I can use. An impeller seems like the best idea, but idk if it would survive 100kg hitting a crack at 30mph. Solidworks syas it would, but it assumes perfect quality aluminum. Titanium is too expensive and hard to mill right now, so I’ll look into that later.
@anon94428844 it’s been a while since you logged here, but what end become your hub?
For anyone wanting to play. Infolytica was bought by Siemens recently and now the MotorSolve online trial is much more powerfull, with the thermal module included and lasts for 15 days
