Wow, you have a lot of experience with this! When you say ‘we were just asking it to do something it wasn’t designed for,’ apart from all the climbing and long hours, what else do you think was pushing it beyond its limits?
Just those two things, particularly the long, steep climbs, but it's a fair question because I don't KNOW that for sure. It's just an educated guess.
Everyone told me, 'hub motors aren't designed for steep climbs!' but I ignored them, and it seemed to be fine... until it wasn't. I sometimes think, "Well, Bill didn't do the subtle little things I did, like back off the throttle a bit sometimes even when I didn't feel like it, just to rest the motor. Maybe it would have survived if I'd been riding it." And he's also at least 20 pounds heavier than me.
But he's also stronger; he's a drummer, works as a contractor, also works out at the gym, and is totally ripped. After the motor died, he insisted on riding Survivor unpowered to the top of the hill and most of the way home -- and with motor and battery, that bike was 40 pounds.
I think I MADE him get off the bike and walk it slowly up the last hill, right before my house. I didn't want him to die, he was 65 at the time, and I was 63. We're both crazy as bedbugs.
But the damage was probably cumulative. I bet it would have died a few months later anyway. I should add: what actually got fried was the controller, but I think the motor was never quite the same after that, either. The controller was under warranty, Clean Republic / Hilltopper replaced it, and it ran for another hundred miles or so out of it before it failed completely-- the wheel would spin under no load, but not under load, Hiltopper said it was the battery BMS, but...
Oh, I don't need to go down the whole rabbit hole! The point is, controllers do fail due to overheating, and the system is not designed for quite such extreme load.
Dunno, lightweight low assist systems seem pretty popular. Part of the issue may be that the more power you have, the more battery you need to actually have a usable range. And battery is generally where most of the system weight comes from.
Catalyzt is absolutely right that I'd be very wary about retrofitting a super light carbon road bike. Hub motors have to turn against something when they are running. More powerful ones have a torque arm to brace against the chainstay, some less powerful ones seem to just brace against the dropout itself. But they all are trying to twist the rear triangle of the bike (newtons 3rd law: for every action theres an equal and opposite reaction; turning the wheel is going to try and turn the frame the opposite way). Super light bikes try and minimize carbon in areas where the frame doesn't need it. Whether the frame can handle those twisting forces, well, who knows. They definitely were not accounted for when the frame was designed though.
I mean, if the Scott Addict eRIDE is too heavy for you, you're probably best off just waiting for that class of bike to get lighter as tech progresses (which it will).
It's not that it can't be done. Plenty of manufacturers make carbon framed electric bikes. The issue is, they are designed from the frame up for this purpose.
Carbon fiber is manufactured as a woven material. The weave itself is geometric, with various densities. The material itself, along with the resin that binds it together, does not have a lot of strength by itself. It derives its strength by laying up multiple layers of fiber in directions (vectors) that are perpendicular to the expected forces. Each frame design takes these forces into account. It's not that different than the way steel frames were built, its just more complicated with carbon fiber. Because it is a laminate material, if you get the force vectors wrong, the material de-laminates. That's very dangerous.
Now add the instantaneous torque of an electric motor, and now you have two independent sets of torque vectors to design around. The motor, and you. Add the weight of the battery, and you have another set of vectors to consider. You could overkill the design, but then the weight goes up.
A properly designed carbon fiber electric bike is an engineering marvel. Carbon bikes even without motors are as well.
You can cobble something together, and it may work for a while. My concern would be what happens when it doesn't.
Whoa-- and you guys just explained that in a way more granular way. Appreciate the more detailed description, I couldn't quite put it into words.
I've always been freaked out by CF, though I do ride a CF seat... it cost me all of $35 to save nearly a pound of weight, seemed crazy not to do it. I've had no problems with it.
When I heard about the Ocean Gate / Titan disaster, I happened to be across the street from the submarine base in Groton, where they build REAL submarines, playing a show (with Bill, of course.)
A lot of the guys in the local music scene have worked on subs, or worked at Electric Boat, it's the kind of town where people really take pride in doing things carefully, correctly and safely-- if you're working under your car in a driveway, and it's only supported by the kind of jack you'd use to change a tire, someone's going to cross the street and yell at you. So everyone was furious, obviously, that accident was totally preventable. Anyway, I got unreasonably spooked by the whole story and it activated my CF phobia. Terrible tragedy.
A lot of my friends on this board were talking me down for months: "You aren't riding your bike 12,000 feet underwater!"
