Long range off-road adventure bike? Max efficiency

[Boreal Wanderer]

I am keen to try a few adventures, typically on atv type trails, old logging roads, and gravel. Also in the spring on hard pack snowy trails or the magic of rideable snow crust when it happens here in northern Ontario. Both day rides and bikepacking over nighters. I am 55 and my one knee can get sore if I over do it on the hills, distance or hard effort so I am looking to "boost" my experience.
I like to stay in shape so I do like to pedal as much as I can. I don't need to go fast and don't mind pushing the bike up nasty hills to extend range and get the butt off the saddle for a bit.
I was able to ride a 40 km trip this late fall in a bit of snow in quite hilly terrain on my fatbike.
I have a Trek Farley 7 fat bike which has the 27.5 wheels (with a 2nd wheelset) that I could convert.
Also an older Kona Caldera with 26" wheels.
I'm not sure how well cadence sensor systems work but think proper torque sensing would be my preference.
So I'm up for converting a bike or buying a new e-bike.
My dreambike would be the fat Samedi Fat 4 but it is ridiculously expensive.
Frey fat bike well priced but probably a 5 kg weight penalty?
I did try a Rocky Mountain Growler 30 on the sidewalk so not much of a test but they are quite common slightly used and the format would do the trick I'm sure.
I do have e-bike experience from way back. I had a nicad powered front CY hub conversion on a Bridgestone mtb commuter that I rode for several thousand km's. Then I thought I was upgrading to an iron phosphate pack from ebikesdotca which was the worst 700 bucks I've ever spent and created a 10 year black hole for ebikes. The battery would self discharge in a few days so I sent it back and they tested it and said it was fine but it just pooped dead. I have plenty of experience with batteries as I'm a RC flyer and experienced the lipo revolution from the start.

Plenty of blabble but too many options! I want to set my wife up with a conversion so it may be economical to convert the Kona with the 68 mm bottom bracket and 135 mm rear hub as it would swap to her bike. Seems like there are many torque sensing BB's but not sure how well they work. Trek has a 120mm BB but I bumped into a fellow riding a Cyclone fatty conversion who informed me that it is available by Bafang and others. Not sure if a Bafang rear geared hub is worth considering or would even fit the 197 mm thru axle.

 

[pwd]

If you are sticking to those types of trails, a mid-drive will be more suitable than hub-drive since you can get away with lower power keeping the battery pack size and motor weight down. Torque sensing does sound like the best option for you (most natural feeling to a cyclist) but it may limit some of the conversion options; the TSDZ2 is the only motor that comes to mind. In my case; I have never used PAS on any of my own setups; throttle only. I can modulate the motor power with the throttle while still contributing via muscle power but that is just my own preference and takes some getting used to. I think I may know the guy who you bumped into 8). There is the Bafang Ultra mid-drive (in addition to the Bafang BBS02 or BBSHD) too but the frame needs to be built to handle the motor. There are some members here that have build their own frames to accommodate a motor like that.

It may be possible to use a torque sensor with certain mid-drives (non all-in-one drives like a Cyclone) but a 120mm bottom bracket may present more challenges since most mid-drive have a longer crank spindle/axle to accommodate another chain ring and crank freewheel etc... but I did see this example: https://endless-sphere.com/forums/viewtopic.php?t=96108

 

[Grantmac]

Once its available the Lightest (product name) drive will probably be the easiest torque sensing drive to add to a bike since it doesn't replace the bottom bracket.

 

[markz]

I've ran across many times I needed an extra boost of power while off the bike, especially so while offroad.
Having assist would change up the dynamics of riding if you need to get off the ebike.

 

[fatty]

Long range off-road adventure bike is sort of antithetical to max efficiency.

For conversion:
Regardless, for long range off-road adventure hardtail, I don't think the insignificant decrease in weight and theoretical increase in efficiency justifies mid-drive sacrifice of reliability. Long range off-road adventure hardtail calls for simple, reliable hub drive.

Speed/aero and weight will play larger factors in efficiency than drive type. Improve efficiency by running as small a motor and controller as possible for less weight/volume; extend range with more batteries; assist both with more pedaling.

 

[Boreal Wanderer]

How much pedal drag is there with certain mid-drives? Certainly an advantage to a geared hub would be very low pedal drag! How many watts of human effort is there to put along? Guessing 150-200w. I read a comment that a fellow had both Bafang hub and mid-drive and found that the mid gave him about 30% more range. However, I could see that the loss comes from over-taxing the hub for speed on hills or just high speeds. Not pedaling much from a stop.
What about battery voltage? I would think higher voltages are more efficient but again it would perhaps push the motor speed higher than I desire to go. I
I rode 26 km yesterday on our groomed fat bike trails on the ridge and the avg speed was 10 kmh. 172 meters of climbing, was -10 C and I didn't need to ride much faster! Some beauty downhill runs up there.

 

[dogman dan]

Mid drive would best fit your needs. It allows you to run slower, while remaining in efficient motor rpm. Any hub will require you to charge the hills faster, using more of the batteries power.

Should be no drag from a mid drive too, since it also lets you retain the normal rear wheel cassette and gears. It will freewheel like normal.

2nd choice would be a lighter, internal geared hub motor, in the 500w rated class, this size motor runs on 1000w easily. A bit less efficient, than mid drive but it also has freewheeling, is lighter, and can be run at 10 mph up hills.

Ideal would be a mid drive on the fat bike, but much easier to get hold of a mid drive kit for your other bike, and, like you said, it can go to your wife's bike, or you can start applying the bike plus one rule. The number of bikes you need is the number you have, plus one more.

If you want to convert the fattie, it should be possible to find a rear geared motor that fits the fat bikes wide rear frame.

 

[HrKlev]

Unfortunately there's not much to choose between if you want torque sensored mid drive for 100mm+ bottom brackets. Do not get the tsdz2 unless you really like broken spindles. The lightest.bike kit as mentioned before looks super interesting, but I dont think they are shipping those out yet. Its always the possibility to DIY something if you are into that

 

[dogman dan]

Re torque sensing, I did not mention it, but the very very best way to get the longest range is to have the motor off as much as is possible, without blowing out that knee.

So a throttle remains the very best way to keep that motor running as light as possible. The idea is to pick a gear you like, and ride it in the cadence you like. Then continuously adjust throttle to keep the knee happy, while never ever using more motor than you need.

Human brain man, still the best computer you can get, at cheap prices. Wah wah, I don't want to think about a throttle while I ride. But seriously, your brain is pretty smart, and its very quick to learn this new thing. Then you don't think about it any more at all, any more than you think about keeping your balance while you ride. That was hard at first too, but you learned it quick, and never need to re learn it for life.

 

[Boreal Wanderer]

Re torque sensing, I did not mention it, but the very very best way to get the longest range is to have the motor off as much as is possible, without blowing out that knee.

Very good point Dan. My front hub commuter was only throttle, and certainly worked well. I had an elastic on the thumb throttle for cruise control and usually pedaled like a fiend. added about 4 kmh over my throttle only speed. Fwd was great in the snow, effectively being an all wheel drive bike.

 

[Boreal Wanderer]

I read a comment on a Rocky Mountain Altitude Powerplay with 632 wh battery and the fellow said best he could get on low was 55 km on normal trails. Also interesting to read about the extra range with the Archon X-1 Bafang mid-drive. I can always stuff an extra battery along the route or just chug the extra weight along.