I bought john's plans too and made my own sojourn machine. *Edited here by Kong* I revised my tray design to use bearings instead of square hunks of plastic.
I did manage to learn a great deal and it was worth what I paid.
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Anyway; I found a supplier for the store front aluminum in camden, NJ. I found this store by driving up to every WINDOW frame and supply store around my usual driving routes and asking them to buy some scrap. After about 5 stops to different shops, I was eventually pointed to this place and was given some free scrap.
After I returned 2nd time I was charged, but I asked for a 6' rail; and the price was fair.
WWW.RAIDGEAR.NET - FFC cables, foam headset replacement parts, and other gadgets.