mainsource said:
the MAC is modded with liberal ventilation holes freewheel side
IMHO this is not a good plan. You are opening up the gears, clutch, and bearings to roadside contaminants. The grease will capture anything circulating about in the air, trapping it into an abrasive slurry. Beyond the gears, the inner clutch bearing is completely exposed (no seals) and shares the same cavity with the sprags of the clutch - also open to the inside of the motor. This seems rather like pouring sand into an auto transmission.
Moving on to projected speeds:
mainsource said:
...a lot of people are forgetting that my wheel diameter is 22.5 inches...
Tires are Michelin Gazelles; 2.5 x 17
- From an authority on MAC operation:
cell_man said:
The other thing to consider is that there is a limit to the rpm these motors will efficiently operate to. There are 80 electrical cycles per revolution with the 16 pole motor and 5:1 gear reduction. If you run the motor much above 400rpm the motor will get hotter due to inefficiencies in the stator that are unavoidable. I would say that the max rpm you should operate is maybe around 500rpm which equals about 60kph in a 26" rim, but closer to 50kph is advisable. If you are really obsessed with having big power, fit dual motors, it really flies and the motors will not be stressed doing it, but the motors will still be limited by the max rpm of the motor. They can handle it, they just get hotter than they would operating at the same power levels, than they would operating at lower rpm.
Your 22.5" tire is not working for you if you are looking for speed because of the recommended rpm limit of 500. A quick back-of-the-envelope table calculation shows this:
Here your tire size would appear to limit operation to about 33-34mph - above this speed you are just shoveling Watts into heat. As Paul points out, you can exceed these rpm recommendations, but you are moving into a region of diminishing returns. This limit arises before any of the heating issues previously mentioned - here rpm and the motor core are preventing additional useful power conversion. (The new thinner laminations may improve this situation a bit, but I doubt you will see a substantial increase in the recommended rpm).
mainsource said:
...I already got LiPo and do plan to manage the motor current draw using a cycle analyst.
In my experience, the clutch is the new 'weak spot' since the gears were strengthened over the last couple of years and damage (seizing) occurs on dead-stop getaways and forceful re-engagements at speed. Unfortunately, simple CA V2 current limiting does nothing at all until the current limit is exceeded. This means that the CA will not be in play as you initially accelerate off the line or re-engage the clutch - which is the time you need the protection.
To address the getaway torque, you can fiddle an EM3EV or Lyen controller to:
- Set the controller Block Time as low as possible (preferably zero) to suppress the period when WOT off the line causes the controller to ignore programmed current limits
- Reduce the phase:rated amps ratio to 2:1 or less to reduce torque as the bike begins to accelerate
Unlike basic CA V2 limiting, a
V3 set up with throttle ramping can soften the getaways and re-engagements. Also, running with Current Throttle (either V2 or V3) will get you some linearity to throttle control - with the MAC over-volted, the throttle will otherwise have a pretty steep step in the midrange. Current throttle will also more effectively limit getaway torque since the CA is providing the throttle signal. If you have one of the new upgraded MACs with the temp sensor, getting a V3 so it can do temp-sensing power rollback will at least alleviate your heating worries...
Just some thoughts....
