Mid Drives kits suggestions which will not affect the Q Factor?

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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mister   1 µW

1 µW
Posts: 1
Joined: Feb 21 2021 2:32pm

Mid Drives kits suggestions which will not affect the Q Factor?

Post by mister » Feb 21 2021 3:12pm

Newb 57 years old here and looking to convert my Fat Bike with 100mm BB.
I ride all year round not very far from my home, never over 15 km's in summer in the city (lot's of stop and go) and less than 7 km's in winter (in a park, single trail ridding on snow, mostly flat terrains, no hills).

I'm looking for a part time assist motor when in need, like coming off from a dead stop and/or going thru deep snow. Top speed is not a factor, torque is.
Since I have a small knee problem, I know that Fat Bikes have already a bad Q Factor and that does not help my knee problem but hey, I love riding my Fat Bike!
That's why I'm looking for a Mid Drive that would not add to the Q Factor of my bike.
Any suggestion?

DingusMcGee   10 kW

10 kW
Posts: 619
Joined: Feb 23 2015 7:11am

Re: Mid Drives kits suggestions which will not affect the Q Factor?

Post by DingusMcGee » Apr 11 2021 10:16am

For a 68mm BB shell the square taper axle is 112 mm long and this translates to a crank arm separation of 155mm which is about 20 mm to short to fit a Cyclone 3K (motor & axle end). See photo.

Options for mid drive kit with no change in Q-factor would be:

1) find a kit that the motor & pulley of the kit fits in less space than 155mm

2). with modification one could move the motor within the triangle beyond the crank arm rotation space.
IMG_0978.jpg
An almost Minimun Q-factor crank spacing
IMG_0978.jpg (4.09 MiB) Viewed 61 times

You have 32mm BB shell length longer than a 68mm shell. I find you need about 20 mm beyond a 68 mm BB shell making for 88mm to fit a Cyclone 3K.

Adding a Cyclone 3K to a fat bike with an BB axel length of 100mm fitted properly would preserve your Q-FACTOR if you have normal bowed outward pedals cranks.

You may have trouble finding/adjusting the specific axle length & bearing locations to both add kit sprockets and preserve Q.

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