Assist via pedals
Funny you mention that: I would say “yes”
. Going through the analysis of my next 2WD incarnation I’ve considered having pedaling as an option
rather than a requirement
I would also agree that as a bicycle mod, 2WD creates an experience closer to moped and motocross that is certainly EV-grin worthy! You are right: Adding a second motor will increase the frame weight by another 14-20+ pounds, and that too is a good point of discussion. Let’s talk about weight:
As a cyclist, we work very hard to shave off grams & ounces from our frames, all of which factor against us when beginning from a standing-stop, climbing hills, and endurance. Depending on use, a typical complete bike assembly weights between 26-40 pounds before rider & accouterments.
As an electric bike, we give up double that at the onset due to the mass of the motor, the controller, the batteries, the wiring, and the minimal accessories to go just 20 miles. I recall fretting that my first commuter battery pack was about 9 pounds and thinking THAT was heavy! And I could feel the difference in the way the bike handled when I strapped on the 13-pound extender: If I pedaled aggressively it was possible to go 50 Seattle-miles on a charge (using LiFePO4). For a noob coming from the bicycle world, this extra weight was difficult to accept, although the electric augmentation that came with it is so enticing, well – it’s only weight and within a few weeks our muscles will adapt, our chests will expand, our arms and hands become stronger, and our senses – become more alert.
Now we throw in another motor to complete the architecture: Twice the torque to the ground. The economies of efficiency begin to go by the wayside because a person that accepts this additional weight understands that they are improving the performance with a penalty, just as if I were to bore out the cylinders and drop in oversized pistons on an ICE. We add more batteries to compensate for the loss of distance, and this is not a 1:1 exchange: It’s closer to the inverse/cube-root function where the first and second doublings are profound, but then the weight of more battery additions are in fact their own flaw, and we’re back to counting grams & ounces.
If we’re talking about just bicycles modified for 2WD, then the weight limits of the frame and the safety of the experience comes about rather quickly, especially if the rider has a large body type: The effects of weight create self-limiting configurations that have their best utility in commuting and sport where the distances & duration are reasonably short.
These past few weeks I’ve been working at the other end of the weight problem: I need to go the distance at speed for hours. I can find/make a frame to handle the weight & speed. The problem is how to charge it at the end of the day. But this is a conversation for a slightly different 2WD application. Regardless – weight factors large, and the way to reduce that is to increase the efficiency of the system as a whole by examining the components. During that process of discovery, everything must be suspect to improvement.
Yikes, another novella! I’ll stop now to brew another pot.
<mmm> Fresh cup! KF