Electric Bike Build

In the Beginning. I had a dream. A great way to start my work day. Ride a bike to work! 17 miles of bike paths each way. I'll cut that down with some extra power.

Since there is power- the bike can have the comfort of good suspension- Specialized Big Hit Down Hill donor bike, 48V 20AH stock china bicycle battery, with a Bafang 750W mid drive. Only a single horse power. Some hot rodding might get that up a half horse. Nice range though. Enough to get me to work, and probably back without being a late and covered in sweat. Mid drives are great, as your not adding un-sprung weight to the suspension, you gain efficiency from utilizing the bikes gearing and these Bafangs are just about silent.

Test ran this taped, strapped, glued and chewed up mess. It passed the test at 32 miles per hour. Heat is the wall it runs into. It also is becomes really difficult to pedal at that speed. So cooling and then gearing, climb to the top of the list of problems to solve. Pencil sketches turn to Computer Aided Drafting and these thoughts begin to consume my minds eye. I dream about it during the day and night. While I'm talking to you, and while I'm driving to work, it is driving my thoughts and my talks, every where I go. I go to work- with some very talented Industrial Designers. Stephen Lambert saw this image from my thoughts.

Did I say he was talented? While I could not exactly replicate image because of some geometric constraints in the off the shelf parts- the design intent was understood. Retro - Modern - Futuristic he called it. Here is the computer model.

There are subtle curves on the outside edges of the front view. Slight twists in the tail. While this bike looks like a bunch of straight cuts, it is not. Every piece has just a little curve or twist in it. Those detials would reflect light off the surfaces nicer than a flat- Stephen shined that light on my design.

The neck had to be thinner for steering, base is wider for battery, tail turned up so the rear tire won't hit it at the end of it's eight inches of rear travel. It has room for a radiator, pump, DC converter, battery and a hefty skid plate to protect the electric motor. It's not completely detailed out yet- but good enough to start cutting metal. Only $325 for all the parts water jet cut out of flat Aluminum.

The pieces fit together like a puzzle. The welding was difficult. I learned many things the hard way. Like using aluminum tape to hold this headlight case together. The glue melted off, right into the weld joint leaving contamination in the weld that was impossible to get out. Lot's of warping, cracking, sinking and practicing on scraps. The welds had to be on very clean metal and the arc extremely close to the fill. I would prop my hand up on a wooden block to gain precision

.

The design was based around my ability and resources. To keep the seat post, cranks and steering tube oriented exactly like the original donor bike- only one member of the triangle was cut out at a time. Then when a new frame member was welded in the gap, the next section could be cut. This procedure avoided the need to make a frame jig thus saved time and money.

Here the second triangle member is getting welded on. Those boxes are for a battery and radiator. Quarter inch thick Aluminum plates for those parts. Went a little overboard with that. Would rather feel safe than save a few pounds in weight. Same reason I have this tire round my gut. A little padding and I float better too. The skin is a 0.09" thick exoskeleton that would probably be enough with out the internal plates. No worries.

Clamp

Tack

Weld

Grind

 

Didn't that look easy? Just slap the wheels on and it lives!

Copper rims set the theme of raw materials.

It's riding nice, but heat is still the main issue. It's 110 F in Phoenix. The inside of my truck can hit 160 F and this motor should stay under 140 F.  I can barely keep 20 mph going without getting too hot to touch the motor. I have no way of measuring- yet.

The battery has incredible range. I rode 50 miles and still had juice. That is too far for me. It might be better to go faster and have less range. It's so quick and easy to swap a battery if I needed. I need to drink more juice, and that can't happen until the motor cools down.

Onto the heat ex changer = thin copper water jacket to cool the electric motor. I drew this up in CAD and cut out the pieces with a band-saw, sanded burs, and chemically cleaned for welding prep.

Threaded hose connections.

Fit a thermo couple on a FET and sealed with Silicone, filled the Motor with 20ml of Mineral Oil to get the heat off the coils and into the housing, sealed it up with high temp gasket sealer and lubed the gears. These details might add up to something....

The copper welds seeped water when installed. I welded, re-welded, grind-ed off and welded again. The welds leaked. I guess some contaminates must have entered. At this point- I'm too far in to start again. I fired up the big torch and tinned the copper to seal it up, similar to copper cookware, except toxic.

 More copper! This time in paste form to prevent corrosion and ensure thermal transfer from motor housing to heat ex-changer.

Another thermal couple on the radiator.

More copper paste to thermally connect the heat exchange to the bike frame. That is a lot of thermal mass to keep things cool.

 Here is the radiator that is under that pile of spaghetti. It's a Alphacool NexXxoS XT45 Full Copper Dual 80mm Radiator. It was made to liquid cool computers. The pump, connectors, tubing and fans were all purchased from computer cooling companies. This system is rated to dump 750 watts of energy. That should be plenty for stock 750 watt motor with some hot rodding that will bring it to 1200 W.

Just in case- a small amount of copper into the antifreeze.

Simplest jig there could be to make a few carbon fiber body parts. This single small bar of aluminum was used to give the radiator a contoured cover.

 Wrapped the cloth around the bike as the mold. Taped with packaging tape and painted with resin.

 Filled the spot for the bolt with a mix of carbon threads and resin and pressed it onto the bike for a perfect fit. Same type of process for the top parts.

Drill some holes and screen them with... more... copper.

In the Endless-sphere tradition- I put a banana in the picture for to help visualize scale :)

  Back on the road.

And Finally, the road less traveled. Liquid cooled, Pedal Sensors, Heat monitored, Blue Tooth enabled Speedict Mars computer and SpyBike GPS Tracker.

This project still has a way to go. Things to correct, perfect, upgrade and clean up. More to come...

.