It is all about approach and personal preference, but more importantly the individual dog itself.

I'm a carpet mill guy at heart. It is what I prefer as it is what I first learned way back when. Some years ago I talked with a guy from the 60's and 70's who put his stock in a turn table. I was intrigued enough, so I built one.

I am not the biggest fan of the really free spinning slat mills. I think they have their place and can compliment other work.

If a dog is running the mill all out and you pick that dog straight up the mill will continue to spin. So at some point the dog is keeping up with the mill rather than driving it. Again, personal opinion, if the dog were picked up the longer that free turning mill spins, the less I prefer it.

I think everyone who is passionate about working a dog has done some research, cataloged information and made changes along the way to make things better. Me, the same.

The first carpet mill I used as a piece of sanded plywood, with a heavy jute back carpet (70's shag carpet) sliding over two pieces of PVC pipe. It was a grueling work out for the dog and being it had that much resistance the 'times' were short to begin with, and then got shorter as that days work moved forward.

For the next few years I built a number of mills and changed surfaces and roller design until I ended up with the mill I currently use. I call it a carpet mill but in reality it is more in tune with a belt mill. It turns free enough where the dog can all out sprint, in his normal sprint gait, and he does not look like he is towing a boat behind him. Yet, he is driving the mill with every step. If I pick him up in the air, the mill will come to a stop, almost immediately.

I prefer this over a free turning mill.

What i would prefer more than that is if I can safely get a dog to all out spring after a ball 20-30-40 times a day. That would be ideal. Nothing artificial. He is propelling his body weight, yet he is going all out and He comes to a stop and then explodes into a sprint. My worries is that a squirrel or rabbit would happen by and the chase would be on.

Great topic.

https://www.youtube.com/watch?v=nq7h6nQmKoM

This is an older video. The mill is sitting on an extension cord so it has some wobble. Other than that it turns well enough for the dog to open up yet she is driving the mill with every step.

S