Hi:
I assume you mean the Magnatrac mini-dozers? Yes, they are very interesting. I actually gave some short consideration to buying a used one of these before I bought the Power-trac.
After having a tracked Bobcat and a smaller wheel skid steer in my backyard (and seeing all the damage that skid steering machines do to the turf), I decided against the Magnatrac's (or any skid-steering design). I had also considered a Toro Dingo (small stand-on skid steer) or one of it's clones. Funny story, I was looking at a Dingo at a rental place, and I was questioning the guy about how much turf damage it would do with an unskilled operator (me!). He said "Aw, it won't tear up the grass, it's light compared to a Bobcat...let me show ya...". He cranked it up and turned it on the gravel. The thing scraped the gravel down to the red muddy clay while he was turning it. Then he said "See, no damage at all." I said "um...ok, I've seen what I needed to see" and left. It was just so funny to me that he was scraping the gravel down to the mud, but he didn't see any "damage". I just thought that was hysterical. /forums/images/graemlins/wink.gif
Magnatrac makes big statements about the better traction you get with tracks, but I really think that benefit is a little overstated with a machine that light. For a machine that light (around 1000-1500 lbs or so, right?), I think that the weight is much more of a factor than whether there's tracks or 4WD with tires. As the weight goes up, I think the tracks become more effective. This may just be my opinion, but I think it's a reasonably valid one. If you notice on the video of the smaller magnatrac's, the tracks are slipping against the ground when the guy is pushing the dirt pile up an incline! They've provided the proof themselves that a machine of minimal weight will have traction limits regardless of whether it uses tires, tracks, 4WD or even 2WD.
One of the things that I really like about the Power-trac is the articulated steering. That, paired with the "fluid differential" effect that you get with the series-parallel connection of 4 wheel motors, is about as easy on turf as you can get, but you still get excellent traction. (For instance, I've pulled a trailer loaded down with gravel on level ground with no problems...total weight around 2500 lbs.) I have occasionally made one wheel spin on the grass (if I was pushing against something that wasn't moving), but that's something you could do just as easily with a mechanical transmission or a typical hydro-mechanical tranny on a machine this light (around 1200 lbs), or even a tracked machine as we've seen on Magnatrac's video.
Another nice thing about the articulated steering is that you can point the bucket exactly where you want with the steering. You can also pretty precisely position a posthole digger or swing a stump grinder from side to side. Very nice! Backing a trailer up gets a little challenging though (you have to steer the opposite direction than you would in a vehicle or other front-steering machine).
There are two disadvantages to articulated steering that come to mind. One is that you can actually get stuck beside a building (meaning you can't steer away from it without banging into it). However, you can use the bucket to crab sideways (lift the front end with the bucket and turn the steering toward the wall, then let the front end down and turn the steering away from the wall...if you're careful, you can crab-away without banging the wall).
The other disadvantage (which is probably the worst one) is that turning effectively shortens the machine, moving the center of gravity (COG) forward. In other words, you could pick up a heavy load with no problems with the machine straight, but when you turn, it'll tip forward onto the bucket. When you straighten the machine back out, it'll then tip back onto the rear wheels. (I think we've effectionately named this phenomenon the "PT Pucker", right guys?) You just have to make sure that you carry loads low, and don't turn with a load up high. If you carry a heavy load up high, you could very well turn the machine over on yourself. If you carry the loads low, it would be difficult to do much damage.
Note: the "carry loads low" rule applies to any machine with a front-loader. Starting down an incline will also shift the COG forward and potentially cause you to tip forward on any kind of tractor or loader! This can be a really bad effect if you're using traditional 2WD tractor with a front loader. As you start down a hill, the COG shifts forward unloading the rear wheels, which is where the brakes are on a 2WD. Essentially, you end up rolling down the hill unable to stop. This isn't a problem with most 4WD tractors (assuming you have it in 4WD at the time). With any machine, you could tip forward going down an incline onto the bucket, and once you're in that position, the only thing you can do to get out of it is to dump some of the load where you're stuck (and it might not be the ideal place to dump!) A good rule of thumb (even with a Power-trac) is to back down a hill if you're carrying a load (even if you're carrying the load low). /forums/images/graemlins/cool.gif
Hope all this helps!
Dave
