Grazelda,
It may be more work than you're interested in putting into research efforts, but we sussed out a lot of the driveline issues you may also be facing
over in this thread. It’s
loooong and often full of hot air, but you may find some of it helpful to you.
The vehicle in the thread was strictly a human powered vehicle in 2007, weighing an estimated 1800-2000 lbs (I really should scale the damn thing). It rolled at +/- 2.2mph and carried up to 8 people with 4 pumping the thing along. At one point we also towed a piano on casters with the player and a girl dancing on top of it.
I’ve heard that a human can generate 0.3Hp under ideal conditions, so that means +/- 1.2Hp moving that much weight. You can do a lot of things with low gearing, but it was maxing us out. We’d have never have gotten to 5Mph. At one point I changed the gearing to give us around 3.5mph and it was just too much. Even a headwind at 2.2 made us really have to work it. For 2008 it was motorized with an old single cylinder engine. The engine was rated at 1-¾ Hp. After a tune up mid-week, it move 6 people at around 3.5 mph pretty easily on good, flat playa. The dunes were tricky and at a couple of points we had to pump it by hand to help it along in the deep stuff.
My long winded point is that if you can deal with making a working drive train, you can do a lot with smaller engines. From practical experience on the playa I think 10Hp+ is a great area to be in for your project. Worst case, you'll know if too many people are on it and can adjust your payload accordingly.
Old welders/generators (8500 watt or more) usually have Mid-teens Hp engines. If you could find one of them, or heck… even check with Northern Tool for new ones. I just saw one in their catalog, a 12 Hp LCT for $399. And a 13.5Hp Briggs for $649... Both brand new. Check local tractor supply places too. They usually stock some engines ready to go for around the same prices.
Go with the biggest thing you can get within reason. A little more power is better than a little less. We had to use 1-3/4Hp because that’s all we could find fitting the need of that particular creation. The 3Hp antique engines weighed in at around 450-500lbs. The 1-¾ was a feathery 190lbs or so.
Also, the biggest problem you’ll face with a straight axle vehicle where the axle is powered will be dealing with the outter wheel turning faster in a turn. You need some sort of over-running clutch or something similar to get around this. Or you could power a single rear wheel, but then there are balance issues.
If I can help at all, please don't hesitate to ask. And feel free to chime in on any of the "Contraption" threads
(in both the 2008 and 2009 Art & Performance areas) and tell about your creation!
~meow
The New and Improved Black Cat... now with 25% more blather
