I got the engine and 2wd manual tranny for peanuts. I was thinking this might make a pretty decent engine for a home-made tractor. Has anyone ever tried to tune these engines for low RPM? I assume it will need a better oil pump to keep the mains from burning up, but beyond that I'm wide open to suggestions.
You really need to start with defining what this home-made tractor has to do.
OK, you likely have the engine/trans from an old pickup. You say 2wd so I assume you mean rear wheel drive and not front wheel drive. Building a home-made tractor simply requires a rear diff ratio suitable for presumed large rear tires. If you used say 14" wheels and low aspect ratio tires, the original rear diff ratio will be about 4.1:1. Put 16" wheels and high aspect ratio tires and the engine will run lower rpm for the same road speed, not that this would be the problem you envisage: the engine would just be less efficient. Your cooling system would need to be adequate, and have an electric fan. An oil cooler would be a good idea.
What you need is a diff ratio of at least 4.8:1. eg some sort of light truck that has large wheels already. This will mean that you could start off in
2nd gear with no problem, leaving 1st for the heavy pulling.About 25 years ago a mate of mine built a nifty AWD/4WD vehicle for his farm in west of Sydney, Australia, before ATVs became available. Almost all the parts came from the local wrecker. He used a 1275cc BMC Mini engine and transmission mounted N-S. The original Mini diff became the center diff, with unequal length prop shafts running to Datsun 1600 diffs running two sets of Morris 1100 axles and uprights. He used 15" wheels as I recall. The whole thing was built in a ladder frame chassis made from 2x4x1/8" tube, with a roll bar and a 6'x4'6" box on the back.
The double reduction ratio with the two diffs was about 14.4:1, but with the bigger wheels this became equivalent to about 9:1. In any case, you easily could start off in 3rd with no load, 2nd for just about anything, and 1st (flat out was about 10kmh) was only used to crawl over rocks and pull stumps. After about 6 months he found the AWD centre diff action was unnecesary on dirt, so he welded it up and made it 4WD.
SD
On Sat, 22 Sep 2007 13:12:03 -0400, "Stewart DIBBS" wrote in :
Pull stuff. Speed is unimportant.
Yeah, I didn't think about that. Since they are made for high RPMs, coolant isn't going to flow as much. I'll start looking for a big radiator. The electric fan is also a good idea. I took another look and that itsy bitsy water pump doesn't look like it can take too much abuse. I figure I'll need a bigger alternator too, so I'll think about making a bracket that can handle both a different alternator and an external water pump.
I have an NP-231 laying around. I think the low ratio is 2.7:1, or something like that. Or I could look for a 4WD tranny w/case, which might be easier since I have no idea how to make an adapter between the Mitsu tranny and the NP-231. And I still have to find a rear axle, too.
You're story about the 4WD stump-puller was cool, but I think I'll keep this one simple.
Thanks for your thoughts, they were helpful.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.