Sunday, February 22, 2009

Wheels and Bent Tubes

I found some of the dimensions of the original Motorwagen on the web today. This table shows those dimensions, plus the 5/8 scale version of them (metric and US). The last column is how I adjusted them for easier building / measuring:

I found that the Sketchup model I found before was not drawn very well to scale. So, I started from scratch. Here is the current dimensions (you can find a PDF here):

I also added the wood slats. It's starting to look like the Motorwagen...

So, with design well underway, it's time to buy some parts. I got wheels at my local Recycled Cycles store - two 700C, one 20" BMX front wheel (the smallest they had):

The 700C wheel have "flip-flop" hubs. They have standard 1 3/8" x 24 TPI freewheel threads on both sides, but one side has a reverse thread for a lockring for a fixed speed gear. I threaded the axles through in such a way to leave a long stub for threading into the live axle. This is standard very fine pitch 10mm x 1.0 thread:

I also bought 1" EMT conduit to build the main frame. Using a conduit bender, I put the appropriate 30 degree bends into the tube:

Using setscrew-tightened conduit interconnects, I temporarily rigged it up to test fit a few things. This is *not* how the wheels will attach. And I will weld the frame permanently before I'm done. But it was fun to see it starting to look a little like the Motorwagen:

Next up - probably more modeling, plus the rear supports / rear axle.

Saturday, February 21, 2009

Side Track - Benz Patent Motorwagen

I've taken a break from the ElectroJeep to do a sprint project - a 5/8 scale Benz Patent Motorwagen powered by a 1 kilowatt electric motor. The Benz Patent Motorwagen was the first automobile designed from the ground-up as an automobile. Invented in 1886 by Karl Benz (of later Mercedes-Benz fame), it was a tricycle, with a 1-cylinder gas motor and wire spoke wheels:

Benz's original drawings can be found in his 1886 patent. Here is a side view:

And here is a bottom view:

Note that the one he actually built and put into (handmade!) production was slightly different, and that's the model I'm going to build (because there are so many more pictures of that model). There's even a Sketchup model of it. I snagged it and scaled it to the size it will be, with a human figure next to it for scale. I chose 5/8 scale because that's pretty close to the ratio of the original wheel size (1260 mm) to typical bicycle road wheels these days (700 mm):

I'm redrawing it to exact scale so I can get the right bits-n-pieces - here is how it's looking so far:

I've ordered the motor, controller, cables, etc. and the fully elliptical leaf springs for the rear axle. I'm now off to buy bicycle wheels (700C for the rear, 450C for the front). Deadline: three weeks and counting...