elo wrote:Hi Jonny
I too have had different experiences in design and transformation into electric vehicles.
I would like to give you some my opinion, so in general, and discuss some Reference datas to compare our projects.
The RV-120pro is a motor designed for the RC aeromodeling, therefore has special characteristics for this use, that are:
1) The propeller requires little torque at low revs, and this coincides with little cooling at low RPM of the motor.
2) The required torque rise by increasing the rpm, but has never sharp peaks.
3) Increasing the RPM, increases the torque and therefore the current in the stator, but also increases the speed of the model and then increases the cooling of the motor.
From this short list i can deduce that, to use RC aeromodeling motors in to "terrestrial" vehicles you must take care to:
1) Run the engine at high rpm, using short trasmission rate (and this applies to all air cooled engines).
2) Consequently use voltages the highest possible, and currents relatively lower.
3) Cool with an external source the motor (air and/or water) that cool it even at low RPM or even when stationary.
elo wrote:I have in the garage a bike that uses a chassis similar to yours, then i would imagine that it also has a base weight very similar.
On this bike (is that of my Avatar) i mounted a motor with nominal 7.5Kw (PERM Motor PMG132) at 3400rpm and with 20.5Nm nominal.
What is interesting is that to obtain the best performance, in Off-Road, i had to put a rate transmission of Z12/Z72.
The same rate we used on the motocross prototype "ROBO Stone 1.0" that uses a motor with 30KW and true 80nm peak.
elo wrote:I do not know if the rate that you are using is the definitive one, but it seems to me much longer than the engine can withstand a 6Kw (?) motor.
elo wrote:Here is instead a youtube channel that speaks of some electrical trial.
- provide an airflow capable to manage at least 1 Kwatt of heat disspiation. I am looking at tangential fan (for server) or trying to put a fun directly attached to the engine shaft (not so easy to found).
The engine, at least from Revolt datasheet, is able to keep a 15kw of peak power (250amp @60v), I choose reduction to have 320 nm at wheel. I am going to review this values in a real world scenario
upek wrote:My two bits:
- you can't have 6kW continous with 1800RPM, expect no more than 4kW continous at that speed
upek wrote:- this motor is quite hard to drive, lots of guys are struggling with controller settings
larsb wrote:I think the deep position of the halls are a problem. They get shadowed by the tooth and distance to magnet is ~4mm.
I originally planned to put the new halls on the outside surface of the stator, meaning gap will be ~1mm
Cable shielding can be done outside of motor but is not easy inside as the wires are 1mm in dia and space is limited.
After seeing my signals i think about putting sensor magnets on the outside of motor and building a small sensor board.
larsb wrote:i'd use high temp epoxy for the sensor glueing. Like UHU endfest 300 or JB weld. Care must be taken with the JB weld as it is metal filled and leads current slightly.
And for the sensor board, i have my own CNC
I plan to mill in magnets into the end cover and place halls on the motor bracket. See the 14 purple holes in picture:
I will use a bipolar latching type hall sensor Honeywell SS460P and mount them on the inside of the motor bracket.
larsb wrote:i am just pretending to be electrical engineer
There's so much info out there to read up on, eventually you learn something.
When i have a board design i'll post it as a step or STL so it can be CNC:ed or 3D printed. I wont make a silicon board but mill it from alu and do the wiring separately.
I will probably do it to both motors if it turns out well. It should be easy to get a clean signal compared to the environment inside the motor where you have coils with 200A current and the hall wires are right on top of them.
I have seen a lot of positive feedback about the revolt from you, and even some close to impossible acceleration claims etc.
I would like to see some documentation to back up your claims. Some real test results with numbers, not just subjective opinions.
Even better would be a video to see what you are talking about. Got any of those?
larsb wrote:In my bike design i haven't got a good surface to mount on the rear side. It would be cleaner on rear side but i think it will be OK on the front side. The space occupied by cables are only half the circle.
It's in green in the pic, front end of mounting bracket
larsb wrote:What are your plans now?
I'd get a hall readout, if they're not good then either claim warranty by revolt or change the hall position.
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