Originally Posted by
Winfried
In the thread, people said even a geared rear motor wouldn't provide more torque than the current 90Nm mid-drive
Exactly this. The biggest, most powerful geared hub motor is going to put out 85 Nm (that would be the fat Bafang G062, which needs at least 175mm dropouts). You can beat this if you go really extreme and say put on a QSv3 direct drive hub motor... which with the right controller is 3000-5000w. And of course a really big battery with much higher voltage than you have now (at least 60v). Thats how you overcome the hub motor's lack of ability to use gearing. Your 90 Nm mid drive is doing more Nm, AND you have an IGH that lets you downshift a couple of gears. So thats a bonus on top. Yes it can be argued that the on-paper specs for your mid drive work out for reals to less than 90 Nm... but that is also true for everything. Go to Area 13 and look for his dyno runs (or just use the manufacturer's numbers as a basis for comparison and don't waste time overthinking it).
For a wheel like what you have on your bike, something like a Bafang G020 would be the not-fat-bike generic-level choice. 45Nm. Or you could at least triple your investment and go with a Grin GMAC. Which is a great hub motor but go to the bathroom first before you price it out. I'm not going to get into other high power options like BAC controllers and whatnot as I am assuming you aren't interested in going down the powerful hub motor rabbit hole. Suffice it to say a hub conversion makes no sense if you pay attention to the bike config now vs. what you would replace it with, and you can read spec sheets.
Originally Posted by
Winfried
and the (aluminum) frame with a too-powerful rear motor could be a problem
I suspect that your bike's replaceable dropouts are steel. You'd be fine I think, even if a hub replacing the mid drive is a bad idea to start with.
Originally Posted by
Winfried
Two motors on the bike is way too complicated a solution for the user and the LBS.
As someone who has built many 2-motor awd bikes, and a 2wd cargo bike is my daily driver, its an excellent solution... but not one suited in any way to your trike.
Originally Posted by
Winfried
Even reinforcing the frame is very unlikely: We're talking LBS who only sell MTBs and road bikes, and refuse even to look at a cargo bike with a gear hub.
The only reinforcement necessary or desirable would be two torque arms. Pretty much entry level DIY stuff. Very easy to do. The term 'frame reinforcement' implies some kind of major work on the frame and thats not what you do with a hub motor.
By the way, if you DO decide to go with a hub motor, 'frame reinforcement' (aka torque arms) are absolutely, positively required. They are not optional. A motor whose axle spreads your dropouts and then spins within them... at that point the dropouts are ruined since metal fatigue means they will spread real easy the next time no matter whether you successfully hammer them back into place. Your bike has replaceable dropouts so (if you can find replacements) the frame will not be effectively ruined with no economical recourse for repair. But I promise you will regret not spending about US$50 on two (!) torque arms to ensure that problem never happens.