A couple of HP questions

[SI2305]

Could anyone fill me in on two specific issues on HP ratings?

First, my beloved JD2305 has an HP rating of 18 PTO and 24 Gross. My first questions are as follows:

1) Many implements such as box blades, grader blades, and generaly any implement that
does not connect to the PTO give a minimum HP rating. Does this apply to the PTO HP
or gross HP. For example, say I was interested in a box blade that required a minimum
of 20 HP, could my tractor handle it?

2) I am VERY interested in getting a flail mower at some time--it just seems like the best
possible mower. It can cut a nice, even surface, it can shred woody material like a
rough cuter. It is fairly small and woud make maneuverability easier than now. Finally,
it does not throw materials.

Unfortunately, hardly any fall into my HP class, but several are close. Could someone explain to me how my tractor can take a full 48" tiller through hard clay (mine hasn't, don't own a tiller, but I know of others who have done just this), but can't it run a flail mower through grass. I find it logical that the tiller going through almost any soil will need FAR more HP/torque than any vegetable material that I am likely to mow. I just seem to think that flail mowing even tall, dense, wet grass will be easier on the tractor than a tiller going through any soil--even sand unless it was just tilling 1-2 inches in which case the tiller is really not the best tool to use.

It seems(at least percieved) like a paradox. Can anyone explain this it away ?


3) Just fantasizing about some day moving up to the 4000 series. The literature all say that they have the same engine specs (and the same JD engine too if I remember corectly). All of the 4x20 have the same displacent, engine speed and torque. However, the smallest--4320 has only about 43 HP gross while the 4720 has close to 60 HP gross. How is this nearly 50% increase in HP possible when all of the engine specs are the same? I believe that they are all tubocharged, but that still does not seem an adequate explanation. Is this just some JD head game to convince people to by more expensive tractors than they need or is there really a substantial differrence.--This issue has driven me nuts for years and I would love a fair comment/explanation.

I know this is a long post, but I would love to know from someowne with experience as to exactly how these HP issues actually work, from the flail mower to JD's inexplicably HP stats.

Thanks in advance

SI2305

 

[danedgington]

In regards to questions 1 and 2, you are basing a lot on manufacturers information, who take into account, not only can your setup physically do it, but also things such as safety so would the wait or size make your tractor unstable.

I don't have a 2305, but I do have a 2210. It can do things way beyond what the literature says in HP/Weight, but you do it at your own risk. I pull a 60" box blade no problem, but the literature says no. Your best bet is to find someone who has what you are looking for and try it and see how comfortable you are. There are things I would do on flat ground, I wouldn't try on a hill. A big thing with some of the bigger implements on the 2210/2305 is you are very lmited in weight you can lift; if it sticks very far past the links it gets hard keep the front wheels on the ground.

 

[RoyJackson]

The HP requirements normally refer to PTO HP, although I had to call an implement manufacturer to find that out (manufacturer was Woods, BTW). They are not hard and fast, but are recommendations so the buyer would have some confidence that his tractor could use that implement.
I'm assuming the engineers assume (TWO assumptions!!!!) a given PTO HP would relate to a tractor of a certain size and weight that would be adequate to use that implement. Really a grey area...

I ran a 60" Land Pride cutter (20 PTO HP minimum, as recommended by Land Pride) behind a 16.5 PTO HP tractor (Deere 670) quite successfully...better then I expected, in fact. The trade off was I couldn't run it as fast as I could with the 790 (24 PTO HP) I bought later. Also, the 670 would bog down more frequently then the 790.
I'd say your 2305 will operate a flail mower if the PTO HP recommendation is reasonably close to the tractor's output...but there are going to be times you'll have to slow down.

As far as the 4x20 series machines...the more powerful ones are turboed. The power output could be based on the size of the turbo, changes in the injection pump (flow and timing), size of the injectors, etc.
The specs you read on the Deere site aren't always all encompassing...more detailed information realy wouldn't mean much to most buyers. The important specs (PTO HP, torque (and at what RPM it peaks) are what sells the tractor.
I'm sure guys who own 4x20 series machines will chime in with more information that I have...

 

[XSKIER]

I'll let you know how a 48" flail mower will work when the grass starts to get long here. I just picked up an old Mott hammer knife with fine cut blades. I plan on running it with my 425 lawn tractor. I think it is 16 horse at the PTO?

 

[SI2305]

Thanks all for the input, some of it is close to what i expected. Just to make matters confusing for me, my Deere dealer did not even know what a flail mower was, much less why I would want one! Not much help there. I spoke to a local Kubota/LandPride dealer. Last summer I purchased a RFM from him and I love it--and it was $500 cheaper than the comparable Frontier model. I have sometbing of a bias for Land Pride based on this. He however was trying to disuade me from buying one--he quoted $4k!

Still, the flail mower continues to elude me. My own gut feel is that if my 2305 can swing a 4' rotary cutter (two heavy two foot dull blades on a mounting that sticks out close to six feet from the link ends) through thick grass, small trees and almost any concievable mowable material, I can't imagine why I can't turn an axel with cutters 2-4 inches out from the axel center on a housing that probably does not stick out more than 3 feet from the link ends.

the Land Pride literature says that they need 25 HP for a 6 foot, and I have seen 4 foot models. BEFCO offers a line that requires less than 18 HP and reach from 4-6 feet. That line seems like it might be ideal--I would be interested in 4'-5' model. The only limiting factor would be weight, but these models seem to fit in. There are no BEFFCO dealers nearby and I have absolutely no ideal what kind of quality these are known for.

The ONLY thought that I can imagine that might concievebly play is the gearing on these models. Unlike most every other implement, I think that a flail mower actually gears up for higher tip speed, thus lowering effective torque. This is just a guess and I still have m doubts, but a flail mower would be nice for mowing under bushes, rough areas, and generally be one of the perfect all-round mowers. I know full well that I won't mow in high range going full blast over heavy grass, but I would think I could make it work.

Another long post, but I wanted to thank those who already commented--it was insightful information. But moreover, I was wondering from those who own/operate flail mowers. Are they as useful I think they are? Do they drain HP as much of the literature implies? Must one go only slowly over grass when mowing? Do they cut both rough areas and fine areas well? Anything that I missed.

Again, I am just brimming with curiosity and I thank you in advance.

SI2305

 

[XSKIER]

I finally got a chance to run the old 48" hammer knife today. I used my 425 lawn tractor, weight wise you definitely know it's there. I took it through a stand of four foot high raspberry bush looking stuff by first backing into it and driving out. The knives make so much racket while hitting brushy material that I could not discern any appreciable power loss. Unlike the rest of you guys, I don't get black smoke to show the amount of power being used. The lawn tractor is so quiet and smooth that I can't tell how much of the 16 hp is being used. One pass through the brush and it was all down flat. I set the mower at about 4" cut height and the blades are mostly dull. It did not do too great of cut on 12" high fine grasses though. My plan is to get my lot in order with the dull blades and then replace them. Pictures to follow later.

 

[XSKIER]