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PTO Horsepower and Generator Question

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Chief
Join Date: Jul 2003
Posts: 4297 Southwest MiddleTennessee
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2003-08-17          62009


My John Deere 4410 is equipped with the ehydro trans. and is rated at 28.5 hp PTO horsepower. Equipped with the power reverser transmission it is rated at 30 PTO horsepower.

My question is.......if the tractor sits stationary running a PTO generator; would my ehydro equipped 4410 develop the rated 28.5 PTO hp or the 30 PTO hp that the power reverser equipped tractor would develop. I understand that there is going to be a PTO hp loss due to the ehydro trans. and parasitic power train loss; but it this PTO hp loss all the time or when the ehydro trans is operating too.

I always thought that the PTO was hard geared to the engine, where as the ehydro runs off the hyd. pump which caused the parasitic hp loss. I would think that my 4410 parked with the gear range selector in Neutral would make the full 30 PTO hp. Which is the case? Can one of you shead some light on this issue as I would like to get the largest possible PTO generator my tractor can safely run without overloading it.

It would be for emergency use only which has been once in 11 years that a generator was needed. We get very little snow. Hooking up the tractor to a PTO generator mounted on steel rails or heavy pallet/wood blocks would be very simple and straight forward. I already keep about 100 gallons of diesel stored at the house anyway; it gets used in the tractor so it won't sit long enough to go bad. I plan to run the generator maybe 8 to 12 hours in any given day MAX, so I would not run up a ton of hours on my tractor over a period of years. I purchased a Generac 5 Kw gas generator back in 1994 after a freak ice storm took out the power for months around here for many. I have never used the generator since. If I had to use the this generator in the event of a power outage, I have doubts about how readily this generator would start after setting for so long. I always have a certain amount of gas on hand but not enough to last for very long if needed. I would think, in my case the PTO genny would be the way to go.

All I would need to do is hire an electrician to install a switch panel and hook up for the genny. What do you guys think? Is my reasoning sound, and to recap; what are your thoughts on actual PTO hp. produced from a stationary tractor. Sorry about the lengthy post.




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Chief
Join Date: Jul 2003
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2003-08-17          62012


By the way. I just realized that the above post is my 800th post. :-) ....


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plots1
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2003-08-17          62013


Chief, how long does it take to use 100 gal of gas, I just put the fifth five gallon can in mine this weekend with 53hrs. on the clock. tractor is 8 months old. 25 gals used so far . At that rate it would take the better part of 3 yrs for me to burn a 100 gals. ....


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Chief
Join Date: Jul 2003
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2003-08-17          62014


On average, I have been burning about 2.5 gallons per hour. I put about 50 hours on her so far this season and figure I will probably put another 10 - 20 before winter. Then it will probably sit for most of the winter. I imagine that I would go through a 100 gallons a season. I also keep 10 - 15 gallons of green dyed road taxed diesel too so I can put off a trip to the Flying J since it is a 70 mile round trip. I can save about 15 -20 cents a gallon there. ....


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harvey
Join Date: Sep 2000
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2003-08-17          62024


Chief YOU HAVE OPENED A CAN OF WORMS HERE! The past generator debates got REALLY long winded.

My thought is: I have a little diesel tractor and a 175 gallon fuel oil tank for oil heat it only makes sense to use the tractor on a generator. If it snows and the power is out so what if the drive is full. If the grass needs mowing and the power is out so what. If a tree is down in my front yard so what. If I need to use the tractor for an emergency I'll unhook the generator for a couple of hours. No big deal.

The generator does not need to run 24/7. Long enough in the am to bring things back to life catch up on news, get fridge re chilled, etc. Noon or so for the fridge and heat if needed. Evening for same reasons and watch a movie. If really cold maybe get up in middle of night to move some air, We have a big wood furnace for heat and it needs air flow around it for a couple of hours and shut it down to idle for a while.

I really get tired of the whinning about ALL THE HOURS THE POOR TRACTOR IS GONNA GET. No body seems to whine about miles on their cars. I bought the tractor to make my life easier and if I wear it out making me comfortable, so what, I'll get another one. No big deal, it's only money and ain't nobody taking it with them. Guys are riding around in $45,000 pick ups and whine about the cost of fuel or even better where to save a $1.00 on a oil filter and then dump in $4.00 a quart synthetic oil. I drive a little shit box Geo Tracker 8 years old and will drive for another 2-3 years before I get another new one like it.

A couple of years ago they had a bad ice storm across the north country here, northern NY state. Many people were with out power for over a week. Roads buried with trees no body going anywhere. How long would the piddly ass 2or3 5 gallon cans of gas last in the gas generators???

How often does this type of thing happen? We've only lost power here for more than 4 hours 2X and never more than 15 hours in the 14 years we've lived in the woods.

Get the PTO Gen. Have a professional hook up your switch box. Enjoy the peace of mind.

Oh yeah I still haven't went and bought a generator yet either. I run 12volt lighting and 12volt fans for the furnace. Guess what I run them from.

Nuff whinning! Harvey ....


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Chief
Join Date: Jul 2003
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2003-08-17          62025


Harvey,

I am on the same sheet of music with you right down the line! Great minds think alike ehh? At least when my CRS is not flaring up. ;-)

But Harvey.........you forgot to say what you thought about my big question. Does the ehydro tractor PTO still produce 28.5 PTO hp even though it is parked in neutral. Or does it produce the 30 PTO hp that the power reverser transmission tractor makes?

I have been thinking more about it now and I see that the hydro pump is hard linked to the engine and is turning all the time, so maybe that is where the 1.5 hp goes. I guess I am thinking that I can get away with a 15kw PTO generator or if I can find one a 14kw. Monday I will call my dealer and ask them this question as well. Thanks for the reply Harvey. ....


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Chief
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2003-08-17          62026


I did found the horsepower to kW requirement formula I was looking for. Granted these formulas are applicable for marine generator use, but kW is a kW and hp is hp. Should be the same requirements for our tractors. According to this formula (predicated upon an 80% generator efficiency rating) a 17kW generator would require 28.5 PTO hp. The chart states to use 93% efficiency if unknown so I use 80% to be safe. Just the size I was looking at. 17kW should be more than plenty for my needs. But it would still be interesting to find out exactly how much hp is lost with a stationary tractor? Sorry if I am getting into too much nitty gritty. I guess my test pilot and maintenance background is slipping through. Reminds me of when I used to do maximum power checks at altitude and having to figure the engine and aircraft torque factors using the charts and formulas. Don't miss that one bit either ;-)
....


Link:   Link to formula

 

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F350Lawman
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2003-08-17          62033


My ONLY real issue with the tractor and PTO generator is if I am not home. Not really that much chance of that for me but for other guys maybe. If you wife isn't familar with the tractor how is she going to do when the s*!# hits the fan? If there is a real bad weather situation,high winds, downed trees, blizzard, floods,lightning, etc do I want her going to get the tractor which she isn't familar with removing the brushhog which she's never done and trying to hookup to the PTO generator and then the house? Let's face it MOST power outages are not on sunny days with fair skies.
Then on top of this if she gets it going she has to go out and add more diesel to the tractor every few hours and maybe open the house oil tank and siphon more fuel?

I can hear my cell phone ringing- her:" Honey the tractor ran out of fuel" me: "Ok go get the cheater pipe and the big wrench, and then unscrew the cap on the oil tank in the basement and siphon some oil, then stand on the front wheel and pour it into the tractor" CLICK-divorce :)

I know, I know we will do practice runs... yeah right like all those family fire drills we all do :)

In this case the LP standby system wins hands down.

I always hope for the best but count on the worst and that is where the PTO generator might not be great. Now if your wife is inclined in these areas it may not be an issue. Even though I am home more than 90% of other guys I know I STILL got caught away when we got slammed with a blizzard last winter. ....


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harvey
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2003-08-18          62039


Sorry Chief. I do not have a clue about a hydro gaining pto power sitting still. The are tested/rated on a pto dyno so I "assume" the hp is right as sitting.

Unless you have some serious electric draws 10-14kw is gonna be plenty, probably overkill. There are some threads about how to add up all the wattage... and then you gotta start motors... You can get a 17kw gen but you would only be able to produce what the tractor is rated for in hp. I would only wanna run 5-8 kw staring stuff etc. Would not want to lug the engine getting a big motor started. (big wood working tools etc)

Me thinks KISS applies.

I'd like one of those big disconnects they use on power poles several of the farmers here have those instead of switching devices. ....


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TomG
Join Date: Feb 2002
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2003-08-18          62047


Now that's a real interesting question and maybe Chief's dealer will have a simple answer.

I'm with Harvey and think the ratings are taken from dyno readings and the tractor wouldn't be moving. At least my manual states 'observed pto hp, and I imagine 'observed' means read off a dyno. Besides, I know that tires, pto and hydraulics do share power from the same engine. My PHA will lug the engine if it's bitting good and I try to pull up the auger with a lot of dirt on top of it. Sometimes going into a pile of gravel with the loader I have to clutch the tractor before the hydraulics will break out the bucket. If the tractor were moving, high traction should reduce power available to the pto, so what traction load would be chosen for the tests? It's got to be static I think.

On the other hand PTO specs for HST tractors are usually less than for gear tractors. I can't figure why a pto HP for a HST should be less than for a gear pto. I think most HST's in neutral just spin the swash plate on the pump around. There aren't many moving parts and no oil is moved. I don't know why that would take much power or at least more power than a gear TX. I think there's something here I've missed and maybe an answer will pop up in the next several days.

I forgot to mention in comments about oversized generators in another thread that smaller breakers can be used to better match a tractor to a large generator. It's probably not desirable to have to reset main breakers frequently if the load is subject to high surges but it's still probably better than having to restart the tractor or have motors overheat.
....


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BillBass
Join Date: Feb 2002
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2003-08-18          62048


Chief-Seems no one knows the answer for sure, so I am going to throw in my 2 cents. Like you I am guessing the hydraulic pump is always running and always pumping and always maintaining a given pressure. If the tractor is not moving, the oil is simply moving thru a bypass. When you move the pedal, the oil is diverted thru a different path to turn the wheels forward or backward. Since the pump is maintaining a given pressure, the engine load would be the same with the tractor moving or sitting still. ???? ....


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Misenplace
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2003-08-18          62052


Gosh Harvey, I have a 45k truck just like several of the other guys here. The last I checked Thats regrettably what a HD diesel costs theese days. I too like to save a buck on a filter and $ on gas. Heck I even use that synthetic stuff only the rich folks use. LOL. I hope that doesn't make me a whiner, If it does someone send me a hanky please. I think maybe we all need to realize there is simply NO definative right or wrong. Its just not that simple. Whos to say F-350 is wrong, Heck I bet the last time he checked his wallet it was his name on the pay check ! And whos to say Harveys wrong even with the side tracked venting ? I would like to learn more about the PTO generators as I THINK they MIGHT just suit my needs right down to the ground. But then I'll have to add a flame retardent suit to the cost to get the info I need here :( NT has a stand alone Diesel Genset at around $2800 for a yanmar Diesel. The JD PTO is about 1/2 that cost and I already have the tractor. I have a 7500 Kw Generac with 25 Hours on it if anyone wants a deal on a gas one. I am switching to diesel. PTO or stand alone. That is the Question. ....


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TomG
Join Date: Feb 2002
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2003-08-18          62053


Good response and it does point to an assumption I made. We might get to a more general understanding of HST's here if that's interesting. I think most HST's use variable displacement axial flow pumps or motors. They can be of swash-plate or other design.

My assumption is that most HST's use a variable displacement pump rather and a fixed displacement motor but it is an assumption. A swash-plate type axial flow pump doesn't move oil or develop pressure in neutral because the pistons don't move. Of course, that wouldn't be true if it's the motor that's variable. There are other types of variable displacement pumps often used in closed center hydraulic systems that do maintain pressure.

I think I've heard of some HST's that use variable displacement designs for both the pump and motor. In that case one of them becomes the range selector.
....


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Misenplace
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2003-08-18          62055


Tom, I just want to make sure I understand your point completely. Are you saying that with a variable hydro pump the trans would be working the entire time a pto driven implement was run ? If so I want to understand that just for my own info. If that is the case I would think for many that would be a very large point against a hydro that I have never seen mentioned before and it is something I for one would take in to serious consideration on my next purchase. ....


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Murf
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2003-08-18          62059


Historically I have only really run gear units, for technical reasons, but have recently added a HST unit to my 'personal use' department.

Based on what I know of them the way it works is remarkably like the way your vehicles power steering system, the pump is creating full pressure constantly, whether or not it is required. However the pressure relief valve opens and shuts constantly maintaining that pressure level.

This though is nothing to do with the amount of WORK the pump is required to do, which is a LOAD on the system. If the PTO is running and the tractor is stationary then the only thing the pump is doing is is maintaining the pressure set by the relief valve. There is some intrinsic power loss by even just this amount of work being done, but not nearly as much as pushing the tractor along.

My overall caution is that tractors are not overly efficient at rated output, nor do they like to produce at 100% for very long. Generally when we are spec.'ing equipment we like to use 75% as a rule of thumb. In other words if your machine puts out 28.5hp at the PTO, consider it to be about 21 hp and it will perform well without beating up the equipment.

Best of luck. ....


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DRankin
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2003-08-18          62060


There is a basic premise I question.

The front drive shaft, the mid PTO, the rear drive axles and the rear PTO all emanate from the same "box" under the tractor seat.

Seems to me that all those functions must be powered through the same hydrostatic "link" that separates the engine from the drive train. ....


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DRankin
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2003-08-18          62062


Murf and I were pontificating at the same time. I like his explanation. It makes sense.

The power is always instantly available. We just use all those levers and controls to direct it.

....


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Misenplace
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2003-08-18          62067


So is the consensus that my 2210 with 17 pto hp will not be over burdened powering the JD genset at an average of 8 hours a year ? Even in a big outage I would not run 24/7. I see the point of haveing the tractor available for other tasks semi moot. Just uhook the genset take care of buisiness then hook it back up. Personally I try use use black outs as an excuse to do less work around the house so I dont think I'd be mowing or tilling with the power down. ....


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DRankin
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2003-08-18          62070


Doc, I think that is right, but from a different angle.

That generator is pre-engineered to match up to a 20-24 horse gas or diesel tractor with 26-12x12 tires on the back.

Sounds like your tractor to me.

I'll weigh in on the other issue too..... my tractor and my pick-up were purchased with work in mind. I don't care if the hours or the miles pile up as long as they both do their jobs.

If one of the tractor's jobs is to keep the water running and the food from spoiling during a crisis, the total on the hour meter become irrelevant. ....


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Misenplace
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2003-08-18          62072


My thoughts have always been the more hours on the meter the beter. After all thats exactly what I bought it for ! ....


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F350Lawman
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2003-08-18          62073


Doc, I am just a humble retired civil servant.... I just marry well :) Only kiddin'

I happen to like the PTO option, it is the best solution $ for $ but for the fact that I NEED to be home to operate it. It also doesn't do you a cent of good if you're skiing in Colorado and the power goes out and your pipes freeze or the T=storm floods your basement and there's no juice to power the sump. I think if a PTO gen is your choice it would be wise to have one dependable neighbor/relative who can set it up to run a couple of hours aday to avoid the problems I mentioned.

It doesn't really bother me THAT much about running the tractor. After all I use my 45K Diesel pickup to power an 800/1600 watt power inverter.:)

I have shown my wife how to hook up the inverter to her conversion van so that would power a light, tv, radio, fan or small sump pump until I suppose I could get home to start a PTO generator running. I left the inverter available with an extension cord and she knows where it is at.

Hmm, why does she need to do that when the van has ac, a bed, a tv/vcr, video game hookups? Just stay in the van :)

....


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AC5ZO
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2003-08-18          62074


Chief, the formula that you have is good, but for PTO driven generators it is probably better to use 2 PTO horsepower for a KW of power produced. So, a 30HP tractor would be good for 15KW of power.

There are a few reasons for this but one of the biggest is that there is a drive train to go from 540 RPM to 3600 RPM for the generator. The efficiency varies depending on whether this drivetrain is belt or gear, but there are losses. All of these losses multiply together, so generator conversion efficiency, drivetrain efficiency, and so forth get you into the 60% neighborhood.

You also need some reserve engine capacity, or the system will crash faster than a NE power grid if a heavy load comes on line. If you exceed the tractor HP capacity, the generator will place an extraordinary load on the motor causing it to slow down. This causes the frequency to drop which in turn causes motors and transformers to draw more amperes and make more heat. All it takes is for a refrigerator to start or the well pump to kick in. In most cases, the high current load will kick out the generator circuit breaker or in some designs, the magnetic field in the generator collapses and it simply no longer generates power until the load is removed. ....


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Art White
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2003-08-18          62075


Murf's right on the power of a hydro. I haven't tried to have my dyno hooked to a tractor yet that is hydro with someone riding on it looking for more power loss. I like two horsepower per KW and I mean PTO not engine. ....


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Misenplace
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2003-08-18          62079


F-350, there were many people here doing just that. sleeping in their motor homes campers etc that had generators. Maybe I should order that pto option for the allison tanny on that over priced truck of mine. It outa drive enough Kw to power a few homes ! No joke the owners manual talks about that as an option ! ....


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AC5ZO
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2003-08-18          62082


Truck PTOs don't deliver anywhere near the engine HP. They are just intended to operate a few hydraulics, winches or lifts. ....


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F350Lawman
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2003-08-18          62083


Me and the Chief were discussing that with the truck PTOs before the blackout. Someone wrote that they done't have too much output 15-25hp? Seems like a waste of a big motor :)

Do you know what the chevy one would be rated at? I am curious. ....


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Misenplace
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2003-08-18          62088


I had no idea that was the case. I was really just being facetious. ....


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TomG
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2003-08-18          62092


The link below is the best pic I have of an axial flow pump, which is a type I that think is commonly used for HST's. The swash plate is rotated by the input shaft and pulls pistons in the cylinder block in and out. The pump pictured has a fixed displacement. Variable displacement ones have a control that controls tilt of the swash plate. The plate spins all the time, but if the plate is perpendicular to the cylinder block then the pistons don't move and there will be no flow or pressure; that is unless there's something I haven't grasped yet. My impression is that the speed pedal controls tilt of the swash plate.

Here's where I am perplexed. If the pump works the way I've thought it does for quite awhile now I can't see any reason why it would develop circulation or pressure when in neutral. On the other hand, I also can't understand why a spinning swash plate would sop up much HP. The power loss from gears to HST would make more sense to me if the pump were doing something. Don't know! Another impression of mine is that the pto input shafts are pretty much separate from the pump.

Full of impressions today but then I'm just a gear head myself.
....


Link:   

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Murf
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2003-08-18          62098


Tom, you were heading down the right track until you got to "My impression is that the speed pedal controls tilt of the swash plate.". This is where you made a wrong turn friend. As I mentioned earlier (maybe not clearly enough), and Mark H. re-iterated, the foot pedal on a hydrostatically driven unit is merely operating a valve which directs the flow of hydraulic fluid. It has nothing to do with swash plate dynamics, that is self-controlled based on input from sensors & valves, etc.

The variable rate pump, BTW, is only required so that you can have a wide range of functions served by one pump instead of several. For low motor speed applications, like loader work, you need maximum PSI, but not as much in the way of flow, as you do for high motor speed applications, like road speed travel, where you need an immense amount of flow, but not at as a high a pressure.

The best example I can think of to help visualize the need for a variable pump is in a log-splitter, you want the cylinder to travel as fast as possible 'unloaded' (on the return stroke and the down stroke before it contacts the wood) to mimimize the wait times, but then you want it to develop maximum power and reduce speed in order to actually split the wood.

Clear as mud, huh?

Best of luck. ....


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Misenplace
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2003-08-18          62099


Speaking of wood splitters I have the big bosses permission to buy a free standing log splitter next week end for a aniversary presant. Now I just gotta find one I like. Life is good :) ....


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AC5ZO
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Posts: 928 Rio Rancho, NM 87144
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2003-08-18          62102


What is she going to get you? ;-} ....


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DRankin
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Posts: 5116 Northern Nevada
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2003-08-18          62107


Our aniversary is today. # 30!! ....


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Misenplace
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2003-08-18          62108


Congratulations ! Going out for dinner or just fireing up the BBQ ? The 31 st is our 7 th. ....


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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2003-08-18          62112


Congrats to both (all 4 actually) of you. I'm just a baby, and on a second 'other half' so I have a long way to go before I get to that benchmark of life. I recently hosted a 50th anniversary 'garden reception' for my parents last month. I was beginning to think I wouldn't see 50 years, never mind being married that long but the Doctor now says I'm "gonna suffer along with the rest of us for a long time yet." LOL

Back to splitters though, Doc, don't buy one unless it has a two-stage pump on it. Also, don't waste your time (and money) on one with 'two direction' splitting, it isn't nearly as powerful on the 'back stroke' and it's a waste. If you are going to be tackling the 'big' stuff you may want to look at the 'block lifter option' if it's available, in fact it might be worth it to eliminate any manufacturer that doesn't offer it. While your at it, check out the ones that flip to a vertical position too, it can be a real back-saver.

Mine is a two part splitter, the 'power unit' is outside in a 'dog house' and the 'splitter' portion is mounted mine into a long, very sturdy steel bench in between bay doors in drive shed at the farm. If you back in with the wood in the back of a truck, or trailer, you move the wood straight sideways onto the bench, then slide it through the splitter and out the other side into another truck or whatever you want, boxes, etc. This way you only have to pick up the wood once instead of many times. Besides if your splitting in bad weather (including hot sunny days) you are inside doing it, not to mention STANDING UP...

Best of luck. ....


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harvey
Join Date: Sep 2000
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2003-08-18          62117


I'm sorry! I can get wound up and that is one of the things that can crank me (fussing about hours on the meter and the other stuff).

Cutting and splitting wood is something I know lots about.

Thanks for not killing me to much. Harvey ....


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Chief
Join Date: Jul 2003
Posts: 4297 Southwest MiddleTennessee
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2003-08-18          62120


Doc, I bought a 20 ton log splitter from Harbor Freight with Honda 5 hp engine. Get the Honda those things run for ever and are real good on gas consumption. Mine has a 1 gal. tank and will run all day and not run out. I think I paid about $850 for mine but that was about 8 or so years ago. I would take a look at the hyd. control valve though. The valve that came on mine was an El Cheapo and jammed up after 2 seasons. I had to install a new valve and has been running good every since. When you do your 50 hour tractor service, save the hyguard oil. It makes GREAT hyd. log splitter oil. That is what I did with mine. As soon as you get one, everyone around you will want to borrow it. I learned my lesson on loaning stuff out. That is fodder for another thread. ....


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Misenplace
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Posts: 875 Michigan
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2003-08-18          62122


Is harbor freight a on line or catalog co ? Or did you buy it locally ? Sounds like just what I'm after. Most of the ones with the Hondas I see are 6 hp and 22 ton but that varies with each company. Dave ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-08-18          62130


There doesn't seem to be much continuing interest in the HST PTO rating question. I'll persist with one more comment. I can't say I'm right because I'm not claiming expertise, bit I don't think I've exactly gone wrong either, nor do I think Murf and I are saying radically different things.

Control of ground speed/torque is achieved by varying the volume pumped in variable displacement engines or motors or both. High volume = fast ground speed; low volume = slow for a pump and reversed for a motor. Common variable axial flow pumps usually are variable swash plate or bent axis designs.

Basically, the swash plate or axis angle has to change to vary the volume pumped or the motor speed. One way or another a swash plate or axis angle must change to vary ground speed. It can be on the pump, motor or both and the speed pedal as far as I know has to affect one or the other. As Murf said, the speed pedal doesn't operate directly on the motor or pump in most CUT's as far as I know. To my thinking if the speed pedal controls ground speed it has to affect displacement on the pump or motor somehow.

Here is a link that describes a HST more or less the way I think I did.

http://www.tigercat.com/hystdem.pdf

The link below gets into HST designs that use variable displacement pump and fixed motors, fixed pumps and variable motors or again both and the advantages of the various designs and throws in gear section in series as well. A set up for Baja Cars is described. However, all of this sort of begs the question. I don't know which design is common on CUT's and that's sort of what I was interested in.
....


Link:   

Click Here


 

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Chief
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2003-08-18          62132


Dave,

Harbor Frieght is online. With shipping charges and taxes they are usually a little cheaper but not always. Homier also sells this kinda stuff too. www.homier.com ....


Link:   Link to Log Splitters

 

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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2003-08-18          62134


You guys sure did generate enough different conversations to put into one, maybe Dennis could just consolidate and have bantering as a subject. ....


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kwschumm
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Posts: 5764 NW Oregon
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2003-08-18          62135


TomG, I've been following this thread without contributing but I'm very curious about the HST PTO HP issue.

Perhaps its an oversimplification on my part, but I figured that the HP loss was simply due to the pump always providing hydraulic flow and pressure, whether there was any real work being done or not. If the fluid has to flow and pressure needs to be built then the pump will sap HP even if the tractor isn't moving, regardless of pump design.

I'm probably missing something, but don't know what it is. ....


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Misenplace
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Posts: 875 Michigan
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2003-08-19          62146


Art, I thought the issue was explained and settled. I'm sure no one meant to overtake the subject. I also always figured that the power loss was simply due to hydraulic pumps and the sheer physical size. Based on the principles of Dynamics that friction is always presant then generally a larger surface area with more parts were create a greater resistance. The one question I still have about all of this that you might help out with is on the larger pto driven gensets that seem to be intended to mount on a small trailer how do you get the pto shaft to run straight ? It seems if you use a telescopeing shaft and back to the trailer that your shaft would likely always be running at some angle. I also gather that the short answer and general consensus is that there would be no greater wear than normal use on a hydro in neutural to run a pto driven generator. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-08-19          62149


Art's comment is well taken. At least in this part of the thread I'm guiltily of mixing and matching principles and specifics and without a grasp of the specifics. All of these designs seem to be out there and Murf pointed indirectly to different properties of the designs, which is something I hadn't thought about.

So, from Murf's comment I did some digging and found the link above that summarizes the designs. The link also says the variable pump only type is likely to be found only on lawn and garden tractors due to torque limitation of the design. The design would save much of the HP that seems to be sopped up by a HST when a tractor isn't moving.

Since power is sopped up, I'd guess that most CUT's use a design where both pump and motor displacements are variable. A variable motor only design is inefficient at extreme ranges of operation and on it's own can't achieve zero speed or reverse. The pump likely has a load sensing design so pressure is maintained and oil bypassed as Bill and others mentioned. A geared range section reduces improves efficiency by reducing the ratio of displacements from the pump and motor required to achieve extreme ranges of motor speed

Anyway, that seems to be where the HP goes. I'm not sure why since I'd guess zero speed as well as reversing could be achieved by the pump swash plate. The answer likely has to do with coordinating operations of the pump and motor. But, that's enough of an answer for me although a bunch of blanks are left to fill in sometime. It's also probably the answer for Doc's question now a long way above. I'd guess most CUT pumps work against pressure all the time, and that's where the HP goes.
....


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Art White
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2003-08-19          62156


Guys relax, they have been installing new phones at the store and goofed up my connections so I've been trying to get a break during the day to do my internent work or play. On the hydro, it is hard to imagine but oil like water or energy takes the path of least resistance. The oil rather then taking a chance of being squeezed sneeks out and won't take the load. So you have a loss of power. That simple. A hydro is not a matter of a pump but you have a moveable swash plate that by changing the angle gives you your varied speed. Your pistons are made of brass and wear extensively with oil starvation. You are running pumps and that is where the loss of power comes from. ....


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Art White
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2003-08-19          62157


Doc, the shaft should be as near straight as possible. That is your work to make it as straight as can be. ....


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Art White
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2003-08-19          62158


Murf jumping in and going back to the swashplate activation. There are different types and the bulk of them in the older tractors do have the swashplate hooked in and that is where the work is done. I haven't seen many of the newer ones apart but from the days of old it was interconnected. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-08-19          62163


The link below goes to a site I ran across awhile back. The site likely supports a commercial idea of the owner but I haven't figured out exactly what is being sold or if it's interesting. The particular page linked to is about the sorts of leakage Art mentioned. There are a couple of other relevant pages on the site.

This mixing and matching of principles and specifics does get messy but I don't read any angst or even dismay here. When it works content should become more specific and less speculative. I think we've got to be messy sometimes to keep up our content quality and everybody eventually benefits. I know my grasp of both principle and specific have ratcheted up through this discussion and I hope others benefited as well.
....


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kwschumm
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2003-08-19          62169


My curiousity is sated. It seems it's just pumping losses and most any pump technology will have such losses when maintaining pressure and flow, even when stationary.
....


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Art White
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2003-08-19          62179


One more note on the hydro's for those in the conversation. The Case, Ingersall units do use a pump and motor to drive, that is why they freewheel downhill. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-08-20          62225


The links I thought I put in an above comment aren't there. I remember now that you can't put site addresses in text but I thought I included another one in link url box but maybe not.

Maybe interest in HST mechanics is exhausted for the moment but I included the links below the pump picture in the link below. The principles link describes constant torque, constant speed and other designs. The description is for a variables pump and motor design.
....


Link:   Pic despcription and principles

 

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DRankin
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Posts: 5116 Northern Nevada
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2003-08-20          62233


I wonder if the swashplate is secured to the housing with a swashbuckle? ....


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Murf
Join Date: Dec 1999
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2003-08-20          62234


Mark, that was not very PUN-ny at all ...

Infact I think it was only 2/3 of a PUN ... the PU part.


Ohhh-oh, here we go again.... ....


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Misenplace
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Posts: 875 Michigan
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2003-08-20          62236


Mine came with duelling control pedals ! ....


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TomG
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Posts: 5406 Upper Ottawa Valley
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2003-08-21          62290


Hey, a pretty good way to ease out of a messy topic. At least I don't have to collect any thoughts and I'd have to have a second to make further contributions. Well, HST's don't have seconds so I'm out of luck. Don't have a HST either. ....


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Misenplace
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Posts: 875 Michigan
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2003-09-09          63457


Well after all this time I finally got a straight answer from the JD dealer on the JD genset use with the 2210. He says no problem to use it, it could even be used on a slightly larger machine. I am thinking certainly no bigger than a 4115 which is key to me as I have plans to trade up. He assures me that the warranty will NOT be voided even though it is billed for the X series. Now if I could just make up my mind. Started at $1,750 but after a LOT of time came down to $1600. Dave ....


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