I have some large DC gearmotors that would make an insane version of the Maslow if anyone is looking to build something like that. You’d have to add the encoder and a higher voltage IC but that’s about it. at 130VDC the current that would need to be driven is rather low, less than 2 Amps. These are out there cheap at $99 because I got them from a salvage of almost new X-ray film readers that were never used.
(I think you’d want to add a final drive worm gear as I think 250 RPM is still a little too fast for this application plus it would lock the position when power was off.)
Here’s the eBay link to the motors:
http://rover.ebay.com/rover/1/711-53200-19255-0/1?icep_ff3=2&pub=5575378759&campid=5338273189&customid=&icep_item=183368893634&ipn=psmain&icep_vectorid=229466&kwid=902099&mtid=824&kw=lg&toolid=11111
I have no space for a larger maslow. Even a full-size maslow might be difficult.
But I DO have a big garden. I was thinking about Maslow’s chain system, and the limitations of farmbot (it’s a flatbed-style CNC with farming tools, that works within a raised bed for growing veg). Neat idea, but you have to buy one per raised bed. Some sort of large-scale chain-driven system might be used to place farmbot over whichever bed you want and thereby expand the system to proper farming-scale applications relatively cheaply.
Accuracy might not be great at that scale, but if the beds are designed so that the CNC drops down onto it (z-axis), slipping into the right position via cone-shaped fixing points, for example, then it could work accurately as a separate CNC within that area. You could even make farmbot a lot smaller.
However, at some point, it’s probably worth looking at systems with unlimited size, like the handheld CNC routers and wheeled ones.
130VDC is the maximum rating, they work nicely on lower voltages at a slower speed and can still handle the same current. There’s a lot of torque on these motors.
An arduino with a 48V H-Bridge would be a nice controller.