Ed of all trades said:Do you want a digger or a potato plow?
I'd just browse photos on the internet until you find something that looks like it will suit your needs. Then copy it and customize it to suit your needs.
It looks like many of the older systems had a complex conveyor system, but many of the newer ones are designed to simply pull them up and leave them sitting on top of the ground for someone to come and pick up. And the whole system may be quite passive.
How much is the Herman Jones potato digger?
Looks like they run between $400 to $700. I think one could be built for about $175 plus labor.
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