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.