Same here... I like the challenge!
I was thinking at first of something like a sideways barn door type system for the base - a length of 20x1/4 screw running through a rotating nut attached to the top dob base plate and fastened at another rotating thing attached to the bottom plate - so the main screw is at a tangent to the dob base.
The drawback here is that it's hard to slew (pick up the dob and move it
and you'd have to reach to the ground to turn it.
I've also thought about attaching some kind of teeth to the dob base and turning it with a gear, but that starts to get out of the realm of easy DIY - unless I can find some old piece of rubbish that has some length of flexible teeth in it.
A better idea would be the friction/spring you mentioned Darryl. A rollerblade wheel held against the top plate of the dob base by a strong spring would work (but might be too clumsy; would it be slow enough?) - and you could release the spring tension to slew it. Same deal for the altitude, but with a smaller wheel.
The friction solution is simple, which is why I'm leaning this way - no need for finely machined parts, and wheels of various sizes should be really easy to find in recycling places. Hmm. I found this, which was an interesting idea:
http://www.atmob.org/library/member/...MoControl.html
I guess my main desire here is less about fixing a problem than refining something that already works well. My dob is smooth and easy to push/pull - I just like the idea of being able to keep my view as steady as possible with a few little twiddles of my fingers. It's also about gadgetising everything... XD