I seriously looked at a Norwood Skid Winch. I have 50+ acres of woods that are under a NY DEC 480A forest management plan that requires cutting down stands of hop hornbeam. Many of the stands are far from trails, but since the hop hornbeam is excellent firewood I looked into skidding options. In the end, I built a hydraulic capstan winch on 3 pt King Kutter Carry All (Craigslist) using a Eaton Char-Lynn 104-1022-006 Geroler motor (eBay) and a 2 1/4" capstan (Northern Tool). I spent $600 in purchased parts and materials and put in ~25 hours building it.
Overal,l I am very happy with it on my 59 HP tractor and am easily able to skid 10" trees up to ~20 feet long. Based on my experience, I doubt that it would skid 20" trees greater than 6-8' feet long and agree that a Frami or Wollensak would be needed to routinely handle logs of 20" in size.
For lighter work that I need to do, I have found the capstan winch to be adequate and very convenient. It is very easy and fast to set up and skid the the smaller trees I work with. I use 1/2" double braid rope and found it to hold up well. I have stalled the hydraulic motor with four wraps on the capstan trying to extricate a large blown down maple log at the bottom of a tangled brush and branch pile. This was reassuring since it indicated to me that the rope was stronger than the motor pull. It is important prepare for the possibility of snapped ropes. I stand well to the side of the winch and tie towels to the line if I need to "pull hard". The capstan operation gives good control of the pulling force and I have used it for skidding as well as puling down snags and hung up trees with snatch blocks. Handling rope is easier than metal cable.
Build details for those interested:
As I designed the winch, I was trying to match the pulling speed of the PCW-5000 that ericm979 referenced. The Eaton motor displacement is 4.9 cubic inches. The geroler motor I used is more expensive then a typical geroter, but works smoother at lower rpm and was rated for the pressure of my hydraulic system. I use the winch on a 59 HP Yanmar and the rear hydraulics are rated for ~9.4 GPM at ~2300 PSI. By calculation, this converts to ~14 HP with a pull ~2750 lbs at ~2.5 fps. In the end it pulls a little faster and thus with less force. I bought a 1.25" shaft diameter motor but I think this was not needed. A 1" shaft would be adequate and would not require boring out the capstan. To fabricate, I used a MIG, drill press, metal chop saw and angle grinder to make most of the parts. I had to use a lathe from work to make a large Delrin washer that fits over the capstan and is mounted on the hydraulic motor base to provide a low friction surface for the in-feeding rope.
