Saturday, November 1, 2014

Something to Show

Over the past couple of weeks, I've been slowly doing work on my bike. I installed and learned Autodesk Inventor, which is surprisingly similar to Solidworks, after trying to use AutoCAD and getting incredibly frustrated. A tip for anyone doing CAD work, the online stores Mcmaster-Carr and SDP-SI publish CAD models of most of their parts, so you never have to model a screw or bearing again. Inventor is pretty awesome, I played with the realistic rendering settings and attempted to use the amazing Finite Element Analysis.
This is a view from the front right of the motor unit, the main power switch and motor controller are the things on the front of the box. You can see the back of the motor through the large hole in the side of the box, and on the motor's shaft on the other side is the small pulley. The belt connects that to the large pulley, the big round thing in the back, which turns the shaft and then the sprocket on the side closer to the camera, which goes to the pedals with a chain.

Making the CAD model forced me to think about this more carefully, and I made a few changes, most notably moving the shaft backwards so it hopefully won't hit your leg while pedaling, and changing the belt tensioning system from motor mounting slots to a spring loaded idler. Last week I ordered the last of the electrical components I need to do some tests, just the motor (which still hasn't shipped yet!) and some connectors.

Moving the shaft back allows the controller to go inside the box, against the front wall, which I think would be a better spot. The hole on the side is for putting the motor through when assembling it, because I'm not sure if it make the turn if you put it through the bottom. I was planning on putting a fan over that hole, but I realized that would conflict with the chain going down to the crank, so right now I'm thinking of just covering it with a thin plate. I moved the motor so close to the bottom that I might not even need to drill the hole, I'll see once I get the motor as the dimensions were a little vague.

I'm still not done with the design, I need to figure out the belt tensioner, cooling fan, and rain/splash covers for the top and bottom that still let air through. I have no idea how to design torsion springs for the tensioner so that'll be fun. Now that I have dimensions to what I'm doing I'm going to start drilling holes in the tube this weekend.

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