Hi there- I just registered after reading through every post on this forum, and let me say that I'm glad something like this is here. I haven't found many good sources for feedback on automated litter box systems.
I used a Littermaid for about a year (Dec 2001 - Sept 2002), and went back to using a standard litter box (Boodabox). I had two cats (now 3), each about 8-10 pounds. One is a tabby, and the other is a Maine Coon.
My problems with the Littermaid:
1. Rake doesn't go low enough, doesn't scoop out all the clumps (same problem lots of you have noted here on the board)
2. Waste "receptacle" doesn't close all the way
3. Waste "receptacle" is too small
4. Motor is too weak
5. Smells really bad between cleanings
6. Litter gets tracked everywhere when the cats leave, even with the hood/ramp/carpet options all in place
After reading through all the issues everyone on the board has had with the Littermaid, I figured these modifications might serve as an alternative to ditching the box and buying something more expensive:
1. Make the main pan a little less deep- install a board or something to raise the floor level so that the rakes don't chop off the tops of the lower clumps
2. Replace the motor with a higher powered unit
3. Build a larger waste receptable out of wood that actually shuts, maybe something that continues under the litter box to increase storage capacity (someone's already done this I think)
4. Build a box with a lip around/under the Littermaid to catch the stray litter granules from the cats' feet
These are just a few ideas I thought of... but I'm not going to try them. I have a buyer for my Littermaid setup, and I'm getting rid of it ASAP. I'm going to try out the Litter Robot soon- I just don't want to deal with the Littermaid jamming up anymore.
Let me know what you think, and if any of you try these mods out. If my buyer flakes out, I may just rip the Littermaid apart and give it the Tim Allen treatment!

