First Post

Joined
Jan 20, 2023
Messages
3
Hello, my name is Preston and I am a new member. This is my first post.

Because my balance is gradually failing, Last July I decided to build a trike. But I didn’t want it to be a full recumbent and also not a delta style that old people in Florida might cruse around on.
So far I have built and rebuilt a development prototype 4 times using conduit tubing and junk parts to get the layout to work the way I want it. Here’s a picture of the final layout. It’s ugly for sure, but low enough to be stable even in hard fast turns. And, I can see and be seen.

The riding position is much like that of a road bike, except turned 90 degrees to make the torso upright. I find this position works the back of the thigh muscles and the butt muscles (gluteus maximus and gastrocnemius) more than the recumbent position which seems to work mostly the quadriceps.

Note the mid-drive eBIke setup and the disc brakes.

I am using the Street Fox plans as a guide. I think Brad has done a wonderful job of explaining everything and photographing the entire project. Right now I am waiting for the steel I ordered plus some other parts so I can start the new construction, this time with mostly new parts and quality material.
I will be grateful for any comments or suggestions. Thank you.
Bike Geezer 2 pictures
 
Joined
Feb 7, 2008
Messages
4,541
Location
Nottinghamshire England
 
Joined
Oct 19, 2012
Messages
2,376
Location
Wakefield, UK
Thanks Paul. That's different. Why use the mid drive as an actual MID drive? Why not mount it on the bottom bracket? It's a bit Mad Max and I like it.
 
Joined
Jan 16, 2011
Messages
708
Location
Vilvoorde / Flanders / Belgium
If you use the Bafang as Mid drive, you can adjust the cadance.

My 48V BB02b can run up to 135 rpm, trying to follow that pedaling, is just flailing around with your feet. But if you use a very small (30 T?) chainring on the bafangs pedal shaft, and a large one on the bottom bracket (52 T), you can pedal a way more lower cadance, and benefit from the increased efficiency of the motor.
 
Joined
Oct 19, 2012
Messages
2,376
Location
Wakefield, UK
The obvious question from that would be why isn't the motor geared to spin faster when used as designed if it becomes more efficient to do so?
 
Joined
Jan 16, 2011
Messages
708
Location
Vilvoorde / Flanders / Belgium
Because the core is a 36V (42V peak) brushless inrunner with a 21-1 2 stage reduction gearing while aiming for a cadance of 110 rpm (fast for normal recreational user). Meaning a KV of 60.
Upp the voltage to 48V (54.4V peak) increases the end RPM to 137rpm.

Increase the load (more amps) lowers the RPM, and decreases efficiency. With the "rating" on the motors giving the best combination of power and cadance to real cost of electronics.
 
Joined
Oct 19, 2012
Messages
2,376
Location
Wakefield, UK
Are you saying that the bafang is designed to run below it's peak efficiency for any user not hitting 137rpm? Is there a reason for that or bad design?
 
Joined
Jan 16, 2011
Messages
708
Location
Vilvoorde / Flanders / Belgium
No, I'm saying that the lightly loaded rpm of a Bafang BBS02b 48V 750W motor in highest assist setting 60 KV is. ( KV=RPM per volt)

I used a magnet and hal sensor on the crank, and tried to follow the motor. At 137 rpm I felt resistance and started adding my own power to the drivetrain. It worked for a short while, and only because I use SPD's. Otherwise my feet would have flailed away.

My wife tried the same trick, and came out on the 110 RPM with the 36V 500W setup.

I also have opened those up (and a few more) to grease the innards. Mechanicaly they are the same.
The BBSHD is only a little different.
 
Joined
Jan 20, 2023
Messages
3
Thanks Paul. That's different. Why use the mid drive as an actual MID drive? Why not mount it on the bottom bracket? It's a bit Mad Max and I like it.
I had it out front for a while but it made the trike nose-heavy. The rear wheel would lift under heavy braking. Also it allow me to use a large chainring on the BB and pedal slower.
 
Top