DIY Long Tail EBike - Chapter 2 - The Frame
The mechanical elements and the electrical elements of an e bike overlap some what. You may have to add in extra mechanical elements (extra rear sprockets & battery storage) to allow for conversion.
I have ordered most of the electrical parts needed, but some are coming from Germany etc. so for now I am concentrating on the frame. In Chapter 1 we saw the basic concept of the bike, and the initial welds, over the last few weeks I have been "sourcing" some thinner tubing and building the rear seating and battery housing section. If you would like to learn about the electrical system the please go to chapter 3.
The main consideration is a large area in which to place the batteries. I had originally looked at using leisure batteries at around 50ah, but these were very heavy and so have opted for 22ah AGL Lead Acid Batteries, which seem to offer a good compromise. I am opting for a 24 volt system.
I have opted for a a brushed motor, rather then a hub motor. So there is a space requirement for this too. Below is shown the space allowed within the frame for the batteries and motor. Note Duplo Brick for scale, or size 10.5 plimsoll trainer if you prefer.
|A large area needed for batteries and motor.|
The whole design of the bike is based around allowing enough space for large batteries, which should give very good range during use. For more detail on specification of electrical systems please see Chapter 3 (coming soon). The width of the rear seat makes it look as though it will be comfy.
|Do not Underestimate Heel Clearance|
|Rear Frame (needn't be this complicated)|
The main tubes (dark grey) are a strong carbon steel tube around 25mm in diameter, with a 2mm / 3mm wall. These were left over from my other cargo bike build and so they are tried and tested as strong enough.
Allow for chain routing. Run a string from the top of the chain cog to the place where the rear sprocket will be, this area needs to be kept clear. I have opted for a smaller front chain ring to allow for a lower rear deck.
For welding I have been using by old gas-less MIG welder, which is cheap and reliable. TIG welding would be neater, as would brazing, but both are more expensive. and TIG welding I have found tricky to master. A gas-less MIG welder can be had cheaply on ebay, and is useful for so many things, particularly if you like fixing things.
|The supports rear of the rear axle - Not so good.|
After welding and brushing of joints comes painting. I had some orange metal paint left over from the last bike I built so I used that. TEMAC Howard Rotovator Orange from Mole Vally Farmers.
DIY Long Tail EBike - Chapter 2 - Kit List
Ingredients for frame:
- BMX Frame
- 15mm Metal Tube Mild Steel (Galvanized Electrical Conduit £11 for 6 meters)
- 10mm Mild Steel Tube (sourced from child's play pen, or similar)
- 25mm Carbon Steel Tuve (bought from steel stock holder)
- Gasless Mig Welder
- Wire Brush
- 4" Angle Grinder with flap disc
- Tape Measure
- Permanent Marker
- Spirit Level
- Straight Edge
- 2 roles of 0.8mm MIG wire
- Hack saw
- Approx 12 hours of time.
DIY Long Tail EBike - Chapter 2 - Lessons Learned
- Always wear gloves when working with metal. Sharp edges can delay things if you cut your hands.
- If your garage floor is flat then assemble the parts on the flat floor and then add them to the main assembly.
- Once you have a few parts lined up using measurements or spirit levels, line up the other parts by eye, it is quicker.
- Cutting tubes badly and filling with weld is quicker than filing tubes to fit curved edges.
- Even thin tubing can be very rigid is the framing supports are closely spaced.
Learn about the electrical system in CHAPTER 3.
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