I was looking for a cheap BMX like all steel bike with a full drive train capable of 11tooth rear freewheel, for an urban mini-velo like shopper concept bike, with ape-hangers, a very long seat post, folding, with decent cargo carrying capacity, for general city-riding and mayhem. I found this Bazooka folding bike on Craigslist - sort of like a poor-man's Xootr Swift. I needed a cheap powerful front hubby that would have excellent torque for urban stop/go riding.
Here's the result - I call it the "Conhis Bazooka"...
With double front fender eyelet torque arms from ebikes.ca
Here's the rear end...
The bike has a lot of custom stuff I had to do, to make it fit me - I'm six feet tall..
Extra long stem with ape-hangers. Just right. I can lean forward into the gap in the ape-hangers for better grinding and front traction...
Extra long 450 mm steel seat post. Due to the leverage of the seatpost, I compromised the frame after a few ride, and had to hack off 2 inches of the downtube, and insert a big chunk of cromolly steel into it - I then expoxied it into the downtube and bolted it in - cut a vertical 1/8" channel in the top of the cromolly, and thus rescued the frame by fashioning a new extension to the downtube for the seatpost. I used Devcon plastic steel expoxy which is probably similar to DP420 - sets up very hard in 1 day - 2900 pounds psi holding power, distributed over 20 square inches of cromolly should hold the downtube extension in there, with an extra bolt through the downtube. I now have a bulletproof seatpost/downtube interface.
The Conhis (48V model) runs nice and smooth on the KU123 controller (sensorless mode) from BMSBattery at 48V - very little cogging - I was pleasantly surprised that I can ride the bike quite easily with no power applied. It starts up almost immediately. The bike tops out around 24 mph with moderate assist and is very torquey - about equivalent to a Crystalyte 408 in a 20" wheel. Awesome torque.
The Conhis is roughly made - not up to the standard of a 9C - its the first one I bought, just to try one out, and I had to open it up from the factory as it turned with a grinding sound. Adjusting the cover plate solved that. There was also paint covering two of the spoke holes. The torque is excellent, but top speed is only around 22 with no assist in a 20" wheeled bike, which isn't too bad. I do need the 11tooth freewheel to keep up with it. The Bazooka has standard 100mm spacing, so no issues with the Conhis, which is narrow at only 90mm. A few spacers from ebikes.ca filled the gap. Doubled up on the fender eyelet torque arms from ebikes.ca
A bit louder than a Crystalyte 40x series, with a slightly higher pitch, but much quieter than a Bafang BPM. I had to build the wheel myself, and I mis-measured the spokes on the first attempt - needed 76mm instead of 72mm spokes. I'm using the black spokes from ebikes.ca, with Maxxis Hookworm on the front and a Big Apple on the back (20x2.0).
The Xootr cross-rack on the back is kind of nifty, with a big removeable wire shopper basket. I had to zip tie on a wire basket quite far back on the rack, for the battery, so it wouldn't heel strike - a problem on small bikes. It is a good solution - nice and low, and well balanced with the front motor, and also the wire has some spring in it which tends to act as a suspension for my Headway pack 48V 10Ahr.
So the result is a great little urban runabout for shopping, which can out-accelerate cars. I think it has lots of personality as well - I recommend these small 20 inch wheeled bikes - they make a fun little ride. The small wheels are tough, and the steel frame of a cheap folder is not too harsh even unsuspended, and the long seatpost and apehangers all help to give you a springier ride.
In spite of the steel in the bike, there is less bike to begin with, which makes this one of my lightest e-freakbikes.
I also had some chaindrop issues to the outside of the ring with the biopace ring I'm using (52) on the front, and I made a chain retention bracket just outside the ring which is pipe clamped to the downtube. You can see the clamps. No chaindrop since.