Weight to HP ratio??

ledebuhr1 · Nov 26, 2003

Is there an ideal Hp to weight ratio on CUT's?? you might have "not enough" or "too much" power.

thanks

slowzuki · Nov 26, 2003

What is the best brand of truck? You have to be more specific. What do you want to do? Mow? Loader work? discing? Snowblowing?

My rule is you can't have too much hp or weight until you can't pay for it or can't get it to where you need it.
Ken

ledebuhr1 · Nov 26, 2003

Ill be doing loader work and snow plowing. No mowing.

Soundguy · Nov 26, 2003

Just doing some quick math, I took the approx weights and engine HP for my tractors, and they turn out like this:

1966 IH cub 14hp / 14xx lbs
NH 1920 33hp/ 3500 lbs
ford 8n 27hp / 2800 lbs
YM 1700 ? 20hp/ 1800 lbs

That is floating about 10 pounds per hp. I've noticed the japanese tractors tend to be a bit 'thinner' and the chinese /korean/indian tend to be 'thicker'.. guess it is due to the metalurgy of the castings.. needing bigger /thicker heavier castings to achieve the strength , etc.

Soundguy

ledebuhr1 · Nov 26, 2003

Soundguy, which of your tractors is the most usefull?? I noticed the NH 1920 had the most HP, but it weighed the most. Do you ever feel it was ever underpowered?

gsganzer · Nov 26, 2003

Probably the most accurate way to derive this is by doing a calculation along the same line, and calculate the relationship of HP to #/in2 of tire contact.

JerryG · Nov 26, 2003

Agriculture industry standard is 90-120 lbs per PTO hp. This is to get the power to the ground.

art · Nov 26, 2003

In the ag world we are just learning the new gross horsepower ratings as we had always used PTO horsepower when we talked and the ratings are still using that at the 90 to 120lbs. For lawn work we look for less weight yet. For the work you are descibing more would be ideal but yet the rest of the time if there is any you would feel that it is fat.

bebster · Nov 26, 2003

When I was researching tractors (before buying my JD 4410) I did a number of plots. Here's one that plots Weight vs PTO HP for popular CUTs from Kubota and John Deere.

The data indicates the ratio for both manufacturers is running about 105 lbs per PTO HP.

ledebuhr1 · Nov 26, 2003

Thanks for your chart. I am assuming that PTO hp is the closest to rear wheel hp??

Looks like I might be upgrading to the L4330.

JerryG · Nov 26, 2003

Art,
I guess the ideal weight for mowing would be the least weight that the wheels would not spin?

KubotaBling · Nov 26, 2003

cut's are alittle more powerful than most bigger tractors ie a 2000# tractor having 20pto hp vs a tractor weights 40,000 might have 200-400 hp. Due to the need for light weight as to not disrupt the soil in rice tires and relatively small tires used on cuts. The floation idea is used to make a high hp low ground pressure unit. Traction is usualy the problem when ground engaging, power when your using a mowing machine.

But i like a tractor that has 1:1 vs the industry std of 100# per hp for weight. So for a 40,000 # tractor a 40,000hp engine would work like one off a boeing ram jet or something like that. I find with a tiller it churns the dirt alot better /forums/images/graemlins/grin.gif

bebster · Nov 27, 2003

PTO HP is the actual HP delivered to the PTO shaft. This is usually the most important HP figure on a tractor, since it relates to the amount of energy that can be delivered to PTO powered implements. It's typically about 73-83% of the gross engine HP for compact tractors. For the L4330 its 80% (43.2 gross HP, and 35 PTO HP).

Soundguy · Nov 29, 2003

You might want to check drawbar hp.. if a unit is very light.. high hp won't transmit to the ground as effictively.

Also I noticed my obvious type-o error.. A zero got left out/ that was 100 # per hp.. and as i see from the other posts.. that is a good average.

Soundguy

Soundguy · Nov 29, 2003

The 1920 is my workhorse.. for many reasons.. not just new and deisel.

It is the only tractor with rops, and 4wd that I have.

It is also one of the only with a 12v neg grnd system.. which allows my niceties like an am/fm radio on the fender. With the rops I get a sunshade... ( though my cub is 12v with a sunshade.. I can't go mow 10 ac in the same amount of time.. etc.

The 4wd is nice for disc'ing too.

I left out a few of my tractors in the comparison.. namely the NAA which is right there weight and hp with the 1920...I could probably do nearly equal work with them.. with trade offs for the 4wd on the 1920, and the draft hyds on the NAA. Power steering on the 1920 is nice.. but as my othe rtractors don't have it.. I can live without it. NAA has turfs.. so that cuts down a bit on its usable traction... but as far a s power goes.. I have to say it is very even with the 1920.. but the NAA"s hyds seem weaker than the NH lift.. etc. ( age i figure ).

On a far side of the comparison.. I see my JD 'B' is only 28 hp ( pto i think ), yet weighs something like 4200 lbs. That is on the low side of hp, high side of weight.. yet this machine used to 'hay' for a living.. whereas I wouldn't want to hay with my 1920 due to the baler throwing the tractor around due to the lighter weight.

Again.. just have to match the tractor with the job.

Soundguy

normde2001 · Nov 29, 2003

"A zero got left out/ that was 100 # per hp"

I was gonna mention that, but thought, "nah, he knows that."
That would have made a pretty good superstock dragracing ratio.

BigDave · Nov 29, 2003

I had the same question about a year and a half ago. I agree with the above answers: it depends. I picked the midsized Class II Boomer from NH which had 25, 29, & 33 hp choices on the same tractor chassis. These choices give 75-100lb per hp. If I was planning to mow on flat land, I guess the 25 hp would have been best & maybe even too big for my mowing needs. If I was planning on doing FEL work, the 29 probably would have been my choice. I live on hill and push snow with my FEL, as well as mow, drag tress, move dirt, and so on. I felt 33hp was a best choice for me. If I had a lot of $$ to spend, like I hadn't spent a lot already, I would have a 20hp tractor for mowing, maybe even a ZTR, and 40-45hp tractor for the real work. Of course my wife has a different opinion on the subject. /forums/images/graemlins/grin.gif

Joe1 · Dec 1, 2003

When considering the tractor weights, you need to use the curb weight not the shipping weight.

My JD 770 weighs about 2,150 #.

Add Liquid weighted wheels, a front end loader, a rear rotary cutter, fluids and my 190# and It's probably some where nearer to 3,900 #. Even with 4 wheel drive and "only" 25 gross HP, and 20 PTO HP, I ALWAYS run out of traction before HP.

The manufacturers have been building these machines for decades, and have pretty good feeling for the weight to power ratio and the kind of realistic work plus a little extra their machines are designed for. A knowledgable dealer and a study of the literature available (a lot of mostly knowledgable opinions on this and other forums), along with an accurate idea of what you need to accomplish should cover the bases.

Good luck

Joe1

k4330 · Dec 2, 2003

Ditto on that. My 4330 says #3500 then add loader, bucket, filled tires. and we jump up over #5000. I was draging a full downed red oak with leaves it bog the motor but lost traction before it would stall ..Bill