posted 5 years ago
If people are interested, I can try to document this project. The basics are- I got a really good deal on a large tractor. It is (like all good deals) fraught with downside.
This tractor is a Zetor 7745, 4WD, 81 HP- but only 8GPM hydraulic.
Parts are an issue. Going over the zetor websites, the brakes are notorious. The manual has lots of issues with apparently pictures and notations from other models used. As an instance, the steering in the manual is with a ram on the left side of the machine with an electrical interface to steering, while the ram on the tractor is actually underneath the machine and operates in a completely different way with direct flow from the steering column relief valve. The parts list is this side ram, so I don't even know which part to order, and while parts are reasonable, shipping is murder. So I have had to bootleg some stuff and use a custom hydraulic shop for $$.
I have looked at installing the 12GPM hydraulic pump when this one dies that is used on their other models, but I am not sure it will fit, and I am not sure the hard lines will take it. It looks like the ID of the lines would have to be [url=https://www.ihservice.com/PDF%27s/Tube%20Selection%20Chart.pdf]1/2" based on this document.[/url] It seems like that's why most small tractors tap out at 8 GPM so you can use cheap lines. I could probably get away with it at low RPMs but then why risk it?
So it looks like I will stay with the pump. The relief valve was going bad, losing fluid through the seals on the spools. Not much but impending failure. The current relief valve is almost 30 years old, and I haven't seen a replacement kit for it. So I decided to get a three spool valve and plumb in an extra line with a skid steer quick attach on it for the grapple and auger. Total outlay is $80 for the relief valve, $30 for the quick attach fittings, $10 for 3/8 to 1/2" adapter, and (ouch) hoses which are actually not terrible at $100. If you shop for standard size hydraulic lines you sometimes come out ahead. I can get a prebuilt line at tractor supply for $11, put on a female to female fitting for $2.50, and save $20 per hose compared with a custom hose on short lines. Longer lines are even more savings, custom is about $10/foot and precrimped are about half.
Then the issue is the pin to skid steer quick attach. You can buy one for $850, or you can make one. I paid $80 for the paddles online (and they look pretty good actually), need to cut the tabs off the bucket with a torch and weld them on the paddles, and reinforce the whole thing with some steel channels. Total outlay for the steel is $50 (I am fortunate to have a steel dealer literally a few miles away). So I sacrifice the bucket (or weld on a reciprocal quick attach plate for $80), but I have two skid steer buckets I paid $80 for pretty much the same size.
So total outlay (post tractor) is around $400. This is not as good as the 18GPM skid steer hydraulics with electronics, but the tractor will not be getting stuck.
I can rent a tracked skid steer if I really need one. One less machine to deal with.
Anyhow let me know if you want pictures. Videos are a real problem due to slowwwww internet but if there are parts of the build that are unclear I can take some pictures.
Standing on the shoulders of giants. Giants with dirt under their nails