DIY Super73 inspired ebike!

This is my second venture into EV and wanted to document the process as I go along. This build thread is going to be chaotic as I'm working on different parts of the build at different times as I wait on parts to be shipped.

Inspiration
The style of the Super73 bike frame caught my eye. I liked the easy rider frame shape especially for city riding, but didnt want to pay premium for a brand. I also like the look of the Onyx moped so wanted to combine the two for my own custom bike to carry two people.

The frame
I picked up a second hand BMX for £40. Only reason this was preferred was because of the disc brakes. Most of the frame was going to be chopped off anyway.


I wanted to extend the frame so two people could comfortably sit on it so welded a 6 inch box section extension to the bottom bracket and made a swing arm so I could attach suspension springs.


I cut off the top tube so I could mount my own top tube at a rake and open up the space for me to comfortably slot in a battery.


Here is the current frame so far with some cheapo RFY suspension springs:



Hub Motor
I didnt know what to expect or what I should buy. So I found the cheapest hub motor kit on ebay. I ended up buying a Voliamart 26" 1500w kit which will be laced into 20 inch fat bike rims.

Wheels
20 inch fat bike rims / wheels are hard to come by in the UK. I had to buy a junior sized fat bike for me to use the wheels. Original rims were a horrible blue colour which I sanded down and painted with 3 coats of matt black paint and 3 coats of clear lacquer.



Battery
Battery pack is going to be made out of Samsung 22p cells bought from a seller here on ES.


I dismantled the packs and did a charge / discharge cycle to work out capacity and internal resistance and repacked the cells usinghttps://www.repackr.com/.


Going for a 13s pack with 11 cells per parallel group for a total of 22Ah. Theoretical amp draw will be 110amps but given these are repurposed cells, I doubt I can pull that much or will need to.

BMS will be a bluetooth one from AliExpress.

Paint scheme I think will most likely be black and if anyone has name suggestions for this build, it will be highly appreciated!

The build continues!

Great project. Frame is aluminum; are you going to heat treat after welding?

2old said:

Great project. Frame is aluminum; are you going to heat treat after welding?

Click to expand...

The new sections of the frame is made from mild steel. I'm not aware if mild steel can be tempered?
I wish I had a TIG welder so I could make the frame from aluminium

Sorry, my mistake. Thought the add-on was aluminum welded to the frame.

2old said:

Sorry, my mistake. Thought the add-on was aluminum welded to the frame.

Click to expand...

Aluminum would have been my preference too given the weight savings but unfortunately no access to a TIG to get it welded up. The steel pipe i am using now is 20mm OD x 16mm ID, so the frame is pretty hefty currently.

Managed to get Part 1 of the build into a video to show how the frame came together!
[youtube]VlYdwt8jNgM[/youtube]

Part 2 of the build. First time lacing a rim. Think it came out alright!

[youtube]675Iayob7uo[/youtube]

I think you might have inspired me to paint the rims on my bike....although unlacing and re-lacing sounds like a pain Cool project man!

reedgen said:

I think you might have inspired me to paint the rims on my bike....although unlacing and re-lacing sounds like a pain Cool project man!

Click to expand...

Honestly I was dreading lacing the bike but it wasnt so bad. A couple youtube vids on how to lace properly will help you prep!

Ah I love build threads that start with chopping up a perfectly good frame :wink:

Nice work though!

I keep forgetting to update this thread.

Project priorities keep changing. I came across a rolling chassis for a supermoto 125cc bike, which I couldn't help but think about converting into electric, so things on the original super73 inspired bike has taken a pause.

Planning to make the motorbike road legal, with the following specs:

• QS138 motor

• Kelly KLS7230NC controller, though I have ordered a FarDriver ND72330 controller to upgrade to, and move the Kelly to the Super73 bike

• 72v 300amp BMS 25ah battery, which is yet to be built

The original bike can been seen in action in the below video near the end. The current frame is just too heavy, so picked up some 12mm OD steel tube to build a trellis style frame, changing the geometry from the original bike and keeping the overall frame build under 15kg.

[youtube]jrZMLvs-zbo[/youtube]

[youtube]t7YKb9_GxAQ[/youtube]