Introduction: DIY Electric Bike // Bionx Conversion

About: I am a maker and here I am sharing the fun stuff of making and creating! Apart from fun my goal is to share knowledge and acquire it. My topics are woodworking, metalworking, maybe some composites, electronic…

Hi Everyone!

This Project is one I am very excited about. I have been thinking about this long before I understood the meaning of Instructables or Youtube :p
I very happy that it did work and the process went as I intended. That is not business as usual for me.

7 years back I was a great cycling enthusiast and bike mechanic I spent all my free time working on my bikes or riding them. At that time there were electric bikes but they were expensive or plainly dull. At that time I didn't had the know how or imagination how to make one, I am very proud I succeeded!

So Lets begin!

I don't have plans available for this project, this article is the plan in fact. Please feel free to visit my website and check other interesting stuff!

Step 1: Concept

So the whole idea or concept was. I have a favorite bike but I want an electric bike for commuting or sportsacvtivity. Buying a new one is always possible but usually that is expensive. And there is no guarranty the bike will actually 'feel' nice. You could buy a new conversion set but here in the Netherlands that is still 1500 euro's without installing.

The next step is then finding a used bike and swap those parts. So this was my most suitable option.

The next paragraph is a more in depth view on DIY e-bikes, skip to the next build step if you are only interested in the actual build.

There is still one other option, buying individual components not specific to bicycle construction or mounting interfaces. This option is only suitable for when you want to develop an e-bike not so much riding one. But one day I will do this kind of a project, I think that will lean more to a electric moped than a real cycling bike. This options is also a bit more costly, not so much on parts but also resources like 3d printing and machining of parts.

Step 2: When Buying a 2-hand Donor Bike...

There are a few points which are relevant when buying a donor for your bike:

1. Wheel Diameter

2. Hub Width

3. Cassette Gears

4. Battery Lifespan

In my case my bike has an wheel diameter of 28 inches; you can check this by looking at the tires of a bike. Not even at the rim. An 28 " bike has the following marking 28x1.5 (for instance) or 700x38 (in milimeters). In this situation the wheel is 28" of course and the tire width is 1.5".

Hub width, the hub width for this type of electric motor form Bionx was 135 mm. In this situation is about the back wheel, if you want to use an (electric) front hub for your bike widths are different from this example. I was making a wrong assumption for myself thinking that it was 125. Eventually the wheel fitted in my bike where it needed to be so problems. 135mm hubs are standard for touring/trekking bikes and mountainbikes. 125mm is standard for racing road bikes, maybe even for normal commuter/city bikes (i am not sure).

The ammount of cassette gears are relevant for rear wheel motors not for front wheel motors of course. In my situation my bike had a 9-speed set-up.

Battery lifespan, this one is quite interesting. Your goal is getting the most 'fresh' as possible battery from your donor bike. When looking at your possible donor's you can make the following calculation and observation. A normal electric bike can show the total amount milage or kilometers done. In my situation 3000 km. You need to devide this by the autonomy (the amount of km before recharge) of the donor in my situation 50 km. so 3000/50 is 60. This is the amount of charges performed. My battery cell technology is Nickel Metal Hydride (NiMH) and lets say you can charge about 400 times with a system like that. Modern Lithium-ion cells can charge up to 600 to 800 cycles with a proper BMS and 'healthy' current surge and request by the motor. So 60 devided by 400 is abuot 15% so my battery has not yet passed 25% of it's total lifespan (give or take) This is not bad considering this bike is from 2011.

Don't let my rattling on discourage you, these are points to think about and research about.

Step 3: Removing Electronics

The first step in making your hand dirty is removing the electronic parts from you donor. Always start with the Battery. This prevents any situation to shock or whatsoever.

My system is working on 24 VDC this is low voltage range and fairly safe. If you make a short circuit at this level there is no big problem. Above 42 VDC then it is starting to become dangerous. A battery like this is supposed to be designed that in an event of short circuit the battery will burn it's fuse.

After the battery the computer and be removed and then the wires between the battery mount and the hub motor.

Step 4: Removing Wheels

Before removing the wheel usually you must disengage the brakes. With disc brakes it is wise to put a spacer in your disc slot, just do that, ask no questions.

Then you can release the bolt from the hub and you can gently wrestle out the wheel. don't overdo this you don't want to damage your tires or spokes.

Step 5: Removing the Battery Mount

After this, you can remove the wireloom on the bottom tube from the main frame triangle. With this Bionx system the battery mount is held in place with two screws where normally your drink holder sits.

When the package is loose gently pull the whole wire loom through the frame, don't be excessive. The connectors are delicate.

Step 6: Replacing the Cassette

Only if necessary and the chain is in bad condition. You can measure this, google will know the asnwer for the distance. Checking by testing is easier, if your drive system is not shifting gears well or the chain skips tooths. Then you definently need to replace the cassete and chain.

This is an older system Bionx hub, where the cassette and freewheel mechanism are one part. Modern systems have this removealbe from one and another. I needed to remove a nut and then I could place my hub removeal tool (the hex shaped nut) on the cassette. Then with a spanner 24 mm, I could disassemble it.

Step 7: Preparing You Bike

Start by removing the back wheel and then the drink holder.

Step 8: Fit the Battery Mount

This Bionx system has an array of holes for assembly on different bikes so in most situations you can find a hole distance fitting your bike. Or otherwise you can enlong a hole or trill another one. I only needed to drill through the rubber 'bed'.

When assembling start by gently feeding through the wires in the frame and then position the battery mount over the holes. Be gently screwing when in the bolts, you don't want to be damaging the threads in your frame.

Step 9: Wiring Up

At this point you can mount and zip all the wires to nice positions on your frame. Be mindful around the handle bar, you need some freedom because this will move ofcourse.

Step 10: Placing the Wheel

At this point I was caught off 'guard', the wheel was a lot heavier than the old one so I had some difficulties holding it up while attaching the hub bolts. Be mindful of that.

Then the wheel was in place, the wires between the motor and battery mount can be attached. I am expecting the motor controller is in the hub because there are only 2 power lines and 5 communication lines 'going' to the motor. And the motor is definetly a brushless DC motor. The hub is quite large in diameter so I am suspecting there is a epicyclic or planetary gear set in this system.

Step 11: The Final Touches

Then you can place the computer mount and when the battery is charged it's time for a test run!

Step 12: The Ride

So I was supprised the disassembly and assembly went so incredibly quick. It worked out in 3 hours so that was no hassle!

The ride is very nice. I put thin tires on my bike so the cruize speed is easily maintained at 28-29 km/h. The standard pedal assist goes up to 25 but I do still feel a gentle force when going up to 27 km/h.

I haven't checked the autonomy of this set-up yet. Didn't reach the distance yet. But I am very pleased with the reuslts!

I hope you enjoyed this instructable. To project on itself was worth the effort!

Wheels Contest 2017

Participated in the
Wheels Contest 2017