Could chainless drives have a viable future?

[palinurus]

A crude consensus says that reasonably maintained chain+derailleur-based drive will be about 90-98% efficient.

I will check when I get home, but I remember some data in 'Bicycling Science' (assuming it hasn't been taken to the charity shop in one of my periodic book clearances) with conclusions that even dry, rusty chains are quite efficient.

 

[Petrichorwheels]

Without going into too much of a deep dive, I had a bit of a hunt across that universal source of truth known as the internet.

A crude consensus says that reasonably maintained chain+derailleur-based drive will be about 90-98% efficient.

In contrast, a good ebike motor seems to be about 75% efficient, while you can get about 95% from a decent dynamo (this number is higher than I expected but I found it quoted in two separate sources). I’d be surprised if the power generated at the dynamo was transmitted directly to the motor. At the very least there’d be some small power loss from the associated electronics, but I’d also expect some significant drops for current/voltage mangling and regulation, so let’s allow a couple more % for that.

All in all that gives an efficiency on or below 70%, and I think I’m being generous. Thats an awful lot of extra effort doing not much apart from saving you some occasional chain cleaning.

90 to 98 pretty good.
How do hub gears rate?
I have a dual-drive on one bike (three speed hub) linked to rear mech and though I liked it in many ways always had the impression that it was sucking energy - had the idea that it needed to be "driven" more than I would expect from a "normal" bike with well maintained hubs.

 

[Bollo]

This article from the rohloff website has a few charts that claim to show the efficiencies of their hub gear vs generic “7/8 speed hub” vs derailleur.

https://www.rohloff.de/en/experience/technology-in-detail/mechanical-efficiency

Despite Rohloff’s generally good rep I’d use a dollop of critical thinking while reading this, as ultimately it’s there to serve a marketing purpose.

I’ve got two bikes with Rohloffs - a flat bar tourer and a kiddyback tandem. The tandem is just being kept for future grandkids now, but I used to use the tourer for a longish, loadedish commute. I’m not going to do a full critique on Rohloff here, but it’s my least favourite bike partly because the lower 7 gears feel a lot less efficient than anything derailleur-shaped, well-maintained or otherwise. It might be psychological due to the additional noise, but you can actually feel gear 5 through the frame.

 

[rogerzilla]

That's how diesel-electric locomotives work, so why not bikes? After all they are almost identical uses. OK, locomotives are slightly bigger - but not much.

They use electricity because it simplifies all-axle drive, facilitates starting from rest (a mechanical clutch wouldn't deal well with 3,000hp) and it allows the prime mover to run in its narrow power band. Losses are still fairly high.