Wednesday 29 June 2016

Ghetto ebike: designing bike battery holders

So I guess the next step I have to take while I wait for the ebike motor to arrive in the post, I should probably start thinking about some type of holder for the bike batteries allowing me to mount them securely to the frame, first step would be to measure the bike down and seat tube diameter with my digital calipers. I scraped the numbers down with a pencil on some cereal box card

That's the basics. I have to remove the front gear derailleur when mounting the ebike motor as there is no point keeping it with a single chainring. Removing it will mean one thing less to worry about when designing parts, it saves me time from having to measure gaps and spacing in my design. I figure all I really need is a couple of frame clamps and bottle mount holes

So I figure that's all the pen doodling we need to do. Next we open up sketchup and start using our measurements to get a design idea created. When I design, I don't have a concrete plan, I allow a large amount of creation to happen as I get through stages, if by the time I get to the next design stage and feel unsatisfied then I CTRL + Z (Undo) and start that step again.

Some of the things I think about are alignment of holes, correct sizing of holes, I'm thinking about structural strength so I think about clamp thickness (but also not going too far as to add too much time to my 3D print), I also think about whether or not I feel the printer will encounter problems with the design such as overhangs and bridges. I try to avoid those if possible just to get a print done with less hassle. Simplicity is key.

Here's some parts on my printer software (Repetier Host). There are other printer software packages to use if you want to try others. I really only use this because I have a Delta printer and it has a preset for it. 

 Once we're happy with design attempt #1 (be prepared for having to refine it until it's functional. If you hit the bullseye first try you can feel really happy, applaud yourself) we can then use the software to slice it up into layers and have our printer make it. My software estimates that these two parts will take approximately three hours, and 45 minutes respectively. My printer time estimation is sometimes out by up to 20 minutes so don't think about it too accurately. I'm going to print in PETG which is popular for tough engineering parts, PLA is okay too but will crack and snap at it's tensile limits. PETG seems to not snap, but bend/warp when near its limits.

So now I have some printing and mount testing to do. Please come back in a few days to see how I get on with that. 

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