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q128c @52 volts?

Posted: May 16 2019 2:13pm
by RyanC

I'm planning to do a "bike like" edgerunner build and am debating motor options. I will need to be able to pick it up and get up 1 flight of stairs (had a bike get stolen locked outside).

Anyway I would like to get into that ~28mph sweetspot, in a 20" wheel. I was hoping (maybe optimistically) for the 36v 328 rpm with a 52v pack to get me up to ~28mph. Any thoughts on that (rated/unloaded speed vs real world)?

Also has anyone used the BMS battery torque sensing BB?

I was thinking about the infineon 12fet+bb torque+q128c with a 17.5ah 52v pack-


Re: q128c @52 volts?

Posted: May 16 2019 2:58pm
by amberwolf
q100 328 in the simulator can't do it in 20" (says it could in 26"), but the 128 isn't in there so dunno: ... &wheel=20i

Just remember that 28mph takes around 750w (at the motor, more from the battery) to maintain on levle ground no winds. So if the motor you want to use can't handle that continuously, then you can only do taht speed until it overheats.

So if you want a small motor to do it, you probably want to use a middrive. Better performance, probably lighter weight (higher cost and maintenance, though).

Re: q128c @52 volts?

Posted: May 16 2019 4:42pm
by RyanC
Hmm yeah-

I had a q128c in my radwagon and I could hold 27-28mph on flat ground and show about 300w from the LCD (06)...that's the bike that got stolen. This was about where it reached max rpm, so you couldn't get more than about 300w into it. It doesn't seem possible that I was putting in 450w with my legs, I have pretty strong legs but not that strong...But the air is a little bit thinner up here in the mile high city. Could also be that the mph and watt readings on the LCD-06 weren't all that accurate.

In any case, I'm thinking maybe a mac 8t and a 60v battery would be the best bet-

My priorities are-

Reliability/low maintenance
not too heavy
coasts reasonably well
and torque sensor

Hard to get all that in either a DD or mid drive...I haven't had a chance to try a TSDZ2, but it feels like asking a lot of it here.

Thanks for the input!

Re: q128c @52 volts?

Posted: May 16 2019 4:50pm
by RyanC
Do you think the 6T Mac in a 20" wheel would be asking too much for it on a cargo bike?

Say maybe 400lbs total at most, and typical more like 320...

Re: q128c @52 volts?

Posted: May 21 2019 10:41pm
by amberwolf
i don't know, but you can check it out on the simulator at and see what it shows.

there is also the gmac version at grin tech, that has no clutch to break, if your'e always going to be using motor power anyway.