Has anyone used a mid-drive with old style bottom bracket?

[benend]

I have an old Worksman frame with the one piece crank style bottom bracket. I know there are converters to make it a standard 68mm 3piece crank style, but I'm afraid that adding that much space would be too wide for a mid drive, like the Bafang BBS02.

Has anyone done it?

 

[ddk]

If your trike frame is a single speed, you gain -o- benefit from a somewhat pricy mid-drive system.

But if you insist you can :
(these are things I've done)
-R&R the BB for a 68mm version (welding and cutting required, not in that order)
-just add a BB leaving the bulk of the old one in place

But trikes are BIG with (usually) room to add a jackshaft which one can motorize
... at a significantly lower cost.

 

[Voltron]

I did just what you were asking about...using a one piece (bike trivia...also called Ashtabula crank) to three piece crank conversion kit to mount a bbs02. Did what I could to talk the guy out of it, and it turned into a giant pita to install. And like ddk pointed out...The real benefit of mid drive is running thru the gears to keep to motor in a good rpm band.... I think you'll find a hub motor cheaper, easier to install, and better suited to the project.

 

[Voltron]

And your worries were well founded... The extra width was one of the main problems. It's hard to find a converter that sits flush with the bottom bracket shell...you could maybe narrow the bb shell on yours tho...on the one I did it wasn't an option with where the chainstays were welded.

 

[benend]

You guys are talking me out of it. I wanted to use a 3spd hub and the mid drive to get the benefits of shifting. The other option is to bend the rear fork 10cm each way - 20cm! - to fit the 135mm hub - and I'd have to deal with rebuilding the wheel, converting it to single speed, aligning the offset, etc. I was hoping to avoid that...

 

[Voltron]

Well, the three speed changes it a bit.. It might be worth it, and if your other frame tubes are in far enough from the ends of the bottom bracket shell, trimming it down a little might not be too much trouble.

 

[tahustvedt]

I think a mid drive often is a better option than a hub drive even with single speed because it means you can keep using easy to remove wheels for easy flat repairs, and keep the mass centralized.

 

[Voltron]

But he's having to balance those advantages out against the hassle of making one work in an old one piece crank frame. And the mass location issue is not as big a factor on an old heavy trike...

 

[ddk]

imo front motors on delta trikes, especially like the op's frame, works best. Better than a rear motor drive for stability and reducing the effects of 'riding down the crown' which all standard delta trikes exhibit to various degrees. (mainly extreme degrees lol)
I has some experience with this, having built a dozen or so trikes and currently possessing three crank-forward deltas with both kinds of drives. Front and Rear drives for all my trikes.

 

[benend]

Bicycle not a Tricycle

 

[ddk]

doh!
...how's your welding skilZ?
Seriously, with the frame you have use a mid-drive but it would be less expensive to just use a different frame and a rear hub.
Or front wheel drive...
imo of course.
And my opinion is just like any other idiots', although I'm more the idiot than most others.