OK, today's question from a beginner...I understand the basics of PTO, back in the days of my youth I helped out enough to know that a) PTO can be extremely dangerous and b) there are a lot of variables involved in using them.
My situation is such that I will not ever by a Snow Blower again. (I lived in the north for about 1/2 of my life and I don't miss the snow very often...the cold, I like)
In the tractors I am considering the PTO HP runs anywhere from 20 to 42. I think they all run at 540 rpm ,IIRC. They all have PTO, but there are differences.
I need help for me (and hopefully for other noobs) understanding what I want and what I need. Essentially, the pros and cons and uses of each type.
Also, I don't think I need a mid-PTO for my uses. As I mentioned, I will not be using a snow blower and I also have no use for a mid-mount mower as I will be doing no finish mowing at all. Are there other implements that typically use a mid-PTO that I should consider? (again, our 18+ acres is about 80% wooded, so anything to do with small-scale forestry and property maintenance is on my plate.)
Right now the list of possible implements to use with the tractor: Rotary Cutter, Post Hole Digger, Box Blade, Tree Shears and/or puller, small tiller, FEL with bucket and grappler. Outside chance we get a backhoe at some point.
Independent vs Live PTO....my recollection is essentially that with Independent you have a lever or switch that engages the PTO when you want it to run. Otherwise, it is effectively in neutral. Live runs when the engine runs and you use a 2-stage clutch to change gears with or without stopping the PTO depending on if you fully engage the clutch. So, experts, please clear up any misunderstandings I have on this and give some pros/cons for why one or the other is better.
Thanks!
- There are three standard rear PTO specifications, 1 3/8" 6 spline shaft 540 rpm, 1 3/8" 21 spine shaft 1000 rpm, and 1 3/4" 20 spline shaft 1000 rpm. Essentially everything designed for the U.S. domestic market under about 75 engine HP is going to be the standard 540 rpm setup only, so you won't see anything else unless you are looking at a larger tractor or some foreign market tractor. You won't likely encounter any implements except a mid mount mower or snowblower (most of them run at 2000 RPM) that don't use a 540 RPM PTO as implements with a 1000 rpm PTO are designed to take at least 75-100 PTO HP to run.
- Typically a mid mount PTO is used to run a mid mount mower. Theoretically you could run a hydraulic pump or something similar off of a mid mount PTO like a pickup with a transmission PTO would, but nearly all of that type of equipment for tractors just runs off of a rear PTO as mid mount PTOs are proprietary and would be not profitable to design for.
- There are three types of PTO clutches, transmission-driven, live, and independent. Transmission driven is what most tractors before about 1960 used and is what some of the smaller gear-transmission compact tractors like the Kubota
L2501/
L3301 and Deere 3D series. The PTO runs off of a gear inside of the transmission and you can either engage the gear and have the PTO turn or leave it in neutral and have the PTO not turn. If the PTO is engaged, it turns whenever the main traction clutch is engaged and it stops when the main traction clutch is disengaged. You can run a stationary piece of PTO equipment like a post hole auger,
chipper, or generator with a transmission PTO, simply put the transmission in neutral, parking brake engaged, and with the PTO engaged let out the clutch.
- Live PTOs use a two-stage main clutch pedal where if you push it in partway, it disengages the traction clutch but the PTO clutch is still engaged, and if you push it in all of the way, you disengage both. The PTO itself has an engage/disengage lever where engaged engages the gear to the clutch shaft and disengages leaves it in neutral. This was seen on many tractors from about the 1960s to the 1980s and is still seen on some smaller gear-driven compact tractors like the Kubota L3701. You have the advantage here of being able to stop the tractor with the PTO still turning and it allows for a synchronized transmission to be practical.
- Independent PTO is what most tractors today use and it uses a completely different clutch from the main traction clutch. The entire PTO setup is clutched and if the clutch is engaged (either by a mechanical lever or by an electronic/electrohydraulic solenoid) the PTO turns, and if the clutch is disengaged, the PTO doesn't turn.
- Tractors with a hydrostatic drive effectively all behave as if they have an independent PTO, even if mechanically there may be a clutch on the engine to control the PTO and also drive the hydrostatic pump. If there is such a clutch setup, you don't use it to stop, shift, or change directions, so it behaves like an independent setup on a gear drive tractor.
An independent PTO is the easiest to use as it's the most "fool-resistant," simply engage when you want the PTO to start to run and disengage when you want it to stop. You will learn to not step "too far" on the clutch with a live PTO when shifting but once you do so, a live PTO works just as well as an independent. A transmission driven PTO will make you alter how you work with a PTO-driven implement as your PTO implement nearly always takes longer to spin back up after clutching than your tractor takes to resume moving. You will either work in a way so you can avoid clutching (e.g. making larger headlands where you can simply turn around rather than making a 3 point turn) or accommodate the added distance needed for the implement to spin back up before you get to where you need to resume working. Depending on what you are doing and how much you are willing to learn, this may be no big deal or a bit of a hassle.
I personally vote for an independent PTO on a gear transmission tractor but would be happy with a live PTO on a gear transmission as well. I would get a different model/series or brand of tractor if I had to get a transmission driven PTO to get a gear transmission instead of a hydrostatic drive. These aren't generally an option on compact tractors unless you pick between different model lines, but I prefer a mechanical PTO clutch engagement over an electrohydraulic engagement and prefer a mechanically-controlled transmission clutch instead of a solenoid-controlled unit such as a powershift or hydraulic reverser as I can feather engagement with a mechanical linkage but am at the mercy of a computer for an electrohydraulic solenoid to avoid it just abruptly dropping the clutch.
