Great work man. Very simple effective design. Grinder and knives. ;~)
Two suggestions for down the road.
First, the way you designed it, it would be a simple thing to make a interchangeable 6, 8 or 10 inch contact wheel attachment to replace the flat platen you have on it now. I know flat grinds are all the rage, but having the ability to do hollow grind will serve you well as you progress as a knife maker.
Heck, for the price you have in that one, you might even just build another one just like it with contact wheels and not have to change anything but wheel size. Very cool!
Second, I can't tell from the pics if you've done it already or not. So just in case...If you have any problem with the belt walking back and forth when you put it under load, which is very common with home builds, it's pretty easy to fix. Just put a little crown on your drive and/or idler wheels. And nope, you don't need a lathe or mill to do it. You can just put a temporary axle through the wheel and put it on a 4x36 belt sander at a slight angle and let er spin. Just put a finger against the side to add slight pressure as it spins and it will sand it right down and stay perfectly round. Just coat the wheel so you can tell what you've removed.
You have probably already thought of both those, but I thought I'd mention them just in case. As you progress with your knife making your gonna think of all kinds of stuff you want to try. The way you've designed your grinder is going to make it VERY easy to add new gadgets. Very cool!
Don't be afraid to try new stuff and innovate. You're off to a great start!
JD,