Looking to get into a disk mulcher and have two sizes (44 or 60) on a high flow 325g (32 gpm @ 3450psi). The manufacturer has a motor sizes for each and I fall between two. Im over gpm on the smaller motor (by two) and right at the minimum for the second. So im debating on which motor to get first off, and the second was diameter. In my mind it would be better off going larger as the disc is going to store more energy and be as wide as the machine nearly, although would take longer to recover on the downside. Just seeing if there is something out there im missing? This is just personal use mainly, not planning on doing anything commercial with it, maybe side jobs later on down the road. Any thoughts?
My thought, sometimes stupid, sometimes not, get what matches with your machine or a little less. Methinks like putting oversize tires on trucks, looks good but does not work worth a *****. Some one else will give you a much better opinion as I have very limited experience.
I think when you are mulching having a little more CTL and a little less (in size) of mulcher makes for a better mix. When you get into thicker material, having more power over the size of mulcher works better. Less chance of over heating the machine. The stored energy of the the larger disc is factor, but as you stated, once you have lost momentum, you wont have enough machine to quickly spin back up to full rpm. While not exactly the same, I considered a 72" drum mulcher, went with the 60". Very glad I did. I can get around and in between trees easier, and I have more hp per tooth with the 60" which is never a bad thing. Again, thats a drum not a disc, but there are some similarities.
I had that thought about size and being able to get it through smaller areas, especially in woods applications if you're not taking it all down.
2 GPM more shouldn't be a big concern. Under load you'd probably lose the extra 2 GPM anyway. Most ratings are at no load and don't take system losses into consideration.
If your terribly concerned, reduce engine rpm by 50-100 rpm to reduce pump flow. As far as I know all brush mulchers are going to have a target rpm at the disk or rotor. Gpm is what determines that rpm, you can adjust by engine rpm or belt sheaves if not directly coupled. 2 gpm isn't jack. Run the unit with smaller motor. Better to have more prime mover than you need.
We can adjust gpm flow electronically. Deere might be able to as well.