considering changing my Edgerunner mid Cycle Stoker...

kEV

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Mar 14, 2020
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Greetings - I have an Xtracycle Edgerunner from 2014 (non e-bike version), and purchased/installed a Grin Cycle Stoker system (https://www.ebikes.ca/product-info/cycle-stoker.html) in 2015. I've generally been happy with it for the last 3,000 km; however, this year I've started to have some mechanical shenanigans act up (which seems like why they discontinued the kit).

- I've worn through a few chains (not unexpected given the power through the chain), and a cassette.
- Grin graciously sent me a stronger eZee motor (I'm unsure exactly which model) as part of a recall where the initial motor casing on the drive side were failing due to the lateral loading (sure enough mine had cracks when I knew where to look)
- I added a nice (expensive!) White Industries freewheel to the new motor (since the first el cheapo one I bought lasted about 50km!)
- I finally wore entirely through the idler pulley gear this spring, and bought a replacement from Grin

Lately my chain and cassette combo is starting to skip again in the lower 3-4 gears, which is driving me crazy as I only have 300 km on the new stuff.

As a bit of background on my riding:
- I live at the top of a 150 m high hill which has some pitches of almost 15%
- once I get down the hill, I have a 12 km ride into town of rolling hills totalling roughly 150 m up/down
- I'm often lugging one or two kids (although now that they are totalling 150 lbs, I try not to do that very often); or one kid and a significant load (e.g. 100lbs) of groceries/hardware store stuff either on the bike in the cargo bags or in my trailer
- the bike must be close to 75 lbs, and I'm 150 lbs, so base vehicle weight is 225 lbs
- side-note, we bought a Faraday Cortland for my wife last year, and it's fairly annoying to have her zip by me up the hill even when I'm unloaded! I'd like to have my bike keep up with hers.

What I'm considering, based on the hills I climb with the amount of weight:

A) Stick with mid-drive: Buy more expensive chain and cassette, possibly changing to something thicker that would handle the power better

B) Stick with mid-drive: Buy an internal geared hub of some kind, which should make the chain/freewheel last longer without the shifting ramps etc; plus I could probably mount a beefier chain etc? I had done some research here a few years ago and came to the conclusion the Rohloff would be the best bet, but I see they now retail for almost $3k in Canada, ouch! And Nuvinci seems to have gone under - I don't see any new ones for sale anywhere. Where would that leave me for options?

C) Convert to a hub motor: Take the existing eZee motor and lace it into the 20" rear wheel; thereby removing the stress from the drivetrain and reusing as many parts as possible (I would need to buy a new torque sensing BB I think? The existing set-up uses some kind of strain gauge on the motor bracket assembly.) I'm concerned about overheating in the rear wheel in between the cargo bags, pulling that consistent grade fully loaded after a ride back from town in the afternoon when it's >30C outside (most days for July/August). I have thought about putting the motor in the front wheel, but I think traction would be a real concern.

D) Convert to hub motor: Get really elaborate and either buy a fancy new rear wheel motor, or even a dual-motor setup? (I'm pretty naive to the implications of the last statement, though it sounds fun!)

I'm really hoping for some insight here - thanks very much in advance :)
 
I did a version of (A) back in 2020, but have worn through a second idler pulley wheel etc. Reached out to Grin and turns out the motor I have won't really be amenable to building into a wheel, so now I'm looking at buying a new motor.

I was thinking of buying the GMAC 8T and putting it in the 20" rear wheel, but ran across a thread that didn't really recommend that combo for climbing any significant hills. So I'm hoping someone could provide some general suggestions for me to consider and research further. Thanks!
 
Is there anything that would prevent keeping *both* systems on the bike? Using each for it's best usage scenarios?

If you had a front hub, with a long bike like that, it would have better traction (than a shorter bike) during rear wheel acceleration scenarios (which would lift the front of a shorter bike more easily), based on my experiences with CrazyBike2's 2WD setup, using a front and rear hubmotor.

You could use both of them together for worst-case scenarios, to spread the loading across both, which would help with drivetrain wear on the rear. You could use the hub for cruising scenarios where it's "natural speed" at the voltage it's run at in the size wheel it's in matches the speed you're going to go (and if you match those to the speed you most often ride at, it would be easy for it). Then use the middrive (or it and the hub) for other scenarios.
 
Depending on how much the existing system limits the power, the power usage may not be significantly different using both systems to take the same load as just one, so your battery might support both of them. If the power usage is higher because the existing system is severely limiting power vs what the load on the system *could* pull if it were unlimited, then the second drive system (when in use and under max load as well) would add it's own max power limit usage load to the battery as well, and if the battery isn't made for that, it would be a problem.

One way to deal with that is to limit the current on both systems to what just the one system would normally take. This prevents the battery load from ever being greater than that the one system presents, but it also means neither system can do it's full work on it's own. A switch could be used (depending on the current limit method) to change from the limit mode to turn this limit on or off for them, possibly even automated so that when only one system is in use the limit is not engaged but as soon as the other system *also* is engaged it would limit both to prevent problems.

Another is to add a second battery to handle the second system, or upgrade the existing battery to handle both.

I just used a single battery for both on CB2, as I also do on the SB Cruiser's 2WD system. For mine, CB2 had separate throttles for front and rear (right front and left rear just like my brakes), but SBC has just one control (via the pedals thru a CA3, and a throttle for situations I can't pedal to startup in, etc.). But this battery is easily capable of handling both systems.
 
I personally don't recommend the hubmotor in the smaller higher-loaded rear wheel. I don't have too much in the way of wheel problems (other than broken axles because of crappy hubmotor design and manufacturing) on SBC, with the load across two smaller rear wheels, but on CB2 with just the one it caused me endless problems, even when built with good spokes, rim, etc. (though less with those...still had problems).

A good hubmotor wheelbuild on the front, where there is much less load, and a larger diameter wheel that isn't as easy to beat up, is probably going to be more reliable than in the rear.

Not everybody agrees with this, and it depends on your specific scenario which would work out better.
 
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