drawbar vs engine

mb58

Member
I have noticed that tractor manufacturers have stopped listing drawbar hp and started using engine horsepower. What's the deal? It appears that the engine hp is a good bit larger than the drawbar hp. Is this a new "selling" tactic. Why not the old drawbar hp vs pto hp like the last 100 years?
 
(quoted from post at 07:39:17 10/24/14) I have noticed that tractor manufacturers have stopped listing drawbar hp and started using engine horsepower. What's the deal? It appears that the engine hp is a good bit larger than the drawbar hp. Is this a new "selling" tactic. Why not the old drawbar hp vs pto hp like the last 100 years?

Because if you knew the actual drawbar horsepower, you would not be nearly as impressed.
 
(quoted from post at 07:39:17 10/24/14) I have noticed that tractor manufacturers have stopped listing drawbar hp and started using engine horsepower. What's the deal? It appears that the engine hp is a good bit larger than the drawbar hp. Is this a new "selling" tactic. Why not the old drawbar hp vs pto hp like the last 100 years?

I'd say it also has to do with the tractors not being tested at Nebraska anymore..which is sad.
 
Though I too lament the demise of so many tried and true ways, in a way the new method does make sense.
Flywheel hp is how just about every other thing is rated - pickups, muscle cars, boat motors and I'm not sure but probably skid steers, dozers, etc as well.
 
Drawbar horsepower is quite difficult to measure and is dependent on a number of highly variable factors such as tires, weight and soil condition. And it is different in every gear. The University of Nebraska is able to make accurate and repeatable measurements of drawbar horsepower. As are the manufacturers themselves. But there's nothing to be gained for a manufacturer by publishing those numbers: no customer can prove or disprove them, and if they're honest with their published drawbar horsepower they'll just be beaten up by a lying competitor.
 
That is why, if you knew what was what then you would not buy it. If you think you would like to get something just a bit bigger than you have for easier pulling what you have they think you will look at those horse power figures and think that tractor with 20 more HP would pull my load like it should you will buy it and then you get to working it you find out it labors more pulling your load than the old tractor so that the next year you will trade it in for one with even bigger misleading numbers. They fail to think you might be so dissapointed that you would switch makes to a competor.
 
I'd say because very few people are plowing anymore, and that was the basic function of tractors in the old days.
 
(quoted from post at 09:01:56 10/24/14) I'd say because very few people are plowing anymore, and that was the basic function of tractors in the old days.

Instead of plowing it is now chiseling and digging which are even tougher drawbar pulls.
 

I've got a totally worn out Snapper rear engine riding mower. Original engine was a 7 horse Briggs. It got replaced with an 8 horse Briggs. Just recently I retired the Snapper, and replaced it with a new rider equipped with a 16 horse engine. The 16 horse engine will not do anything that the old 7 horse would not do, but the 16 horse engine does drink a whole lot more gasoline to get the same job done. Progress??
 
Who has the time and money to dismantle a new tractor and measure the engine horsepower? PTO horsepower is much easier to check.

What are realistic ratios between engine HP, PTO HP and drawbar HP for most tractors?

Engine HP - 100%
PTO HP - 95 to 90%
Drawbar HP - 70 to 80%?
 
Not sure why anyone would buy a new tractor to pull better without trying it first to see if it pulled better. If they won't let you try it, all sorts of red flags should go off.
 
Yes, it's a selling tactic. Engine horsepower is paper horsepower. Never verified and quite meaningless. Look at the PTO and drawbar ratings for a more realistic rating. But on tractors under 50 or 60 horse that are not required to be tested at an independent lab such as we have at Nebraska you are still on your own as to the validity of the stated figures. I always look for the Nebraska Test figures.
 
Gross engine power is always the largest number followed by net flywheel hp... and the numbers that manufacturers use vary between those two today... Both are really quite meaningless because neither one considers the parasitic loss in the drivetrain. I would say on most tractors in the 60-100 hp class... PTO power will be in the 85% range of net flywheel power. Drawbar power will be in the low-mid 70% range. On the lower end for bias tires and on the upper end for radial tires with an easy 2-3 point spread between them on the same tractor. Personally I just laugh at net flywheel numbers because they don't mean anything. I can show you tractors that have a 10% margin on net flywheel power that make the same drawbar power due to drivetrain efficiencies in on over the other. The gap is not so wide with PTO power but it's still there... I don't take Nebraska or OECD numbers as the be all, end all of tests either... but when interpreted for what they show they are quite meaningful.
The main area that I think they err somewhat is in the fuel efficiency numbers... in that while they do show which is most efficient at maximum power they do not necessarily mimic real world usage conditions where the torque curve of some engines will result in a lower gph consumption rate for a particular job even though the full power efficiency is somewhat less...

Rod
 
Moline used to list engine brake hp and pto on some listings for their tractors in the early to mid 1960s, of course it sounds like a lot more horsepower, but as my dad always said.....they were bigger horses years ago. How true lol.
 
It is probably because of all these little Hydrostatic tractors....

The neighbor has a 30 hp Kubota that is hydrostac, and I swear that my lawn mower would out pull that thing!! It is GUTLESS on the pedal... NO power! So, on something like that, Drawbar power is probably about 15, where as engine power is 35, which would you rather spend $25000 on?? :) Bryce
 
Chances are you aren't used to a hydrostat. Less they are more lossy than a gear transmission but the no power feel is from trying to use it as an accelerator pedal rather than understanding its a gear shifter.

People first using them will hit a hill and push the pedal. Wrong move, you need to downshift on hills, that means lift off the pedal.

Without knowing this it feels like a boggy underpowered machine. The 5 or 10% extra loss in a hydro isn't what your butt is feeling.
 
One thing I've wondered about on the accuracy of flywheel HP was did it include the parasitic losses from spinning the flywheel itself or hydraulic pumps, PS pumps, water and fuel pumps and generator or alternator, etc, etc?
Pull all those things off an engine and it would produce more on the end of the crank than is sent through the clutch to the pto or tires where of course, more loss occurs.
 
Ken you nailed it He does not know how to drive the tractor, Very common complaint they are trying to pull something when they have the pedal to the floor or in affect in road gear. Just takes some learning but most times they will out pull the gear drives of the same hp.
 
Tractors sold in the US are still required to be tested at Nebraska. You can go to the website and read most of the reports. All tractors measure the PTO power. I think if it is over 100 PTO HP or so, they will do drawbar testing as well. The literature from the US manufactures still show PTO power as well.
 
you guys need to come into the new world. where i live most all tillage tractors are 4 wheel drive or quads and most are bought with out pto so its a little had to dyno so they have gone to flywheel HP just like trucks
 
You know you are going to get from the bota lovers.

I got jumped on because I said my neighbor has a new BX23 with loader and hoe. It can't lift anything and the hoe has no mussle. Then I heard all kinds of excuses like something is wrong with a brand new bota.
 
Dynamometer testing of the PTO hp is a lot less cumbersome than hooking up the drawbar. Usually the two aren't that far apart.

Mark
 
(quoted from post at 08:48:06 10/25/14) Dynamometer testing of the PTO hp is a lot less cumbersome than hooking up the drawbar. Usually the two aren't that far apart.

Mark
ust my off the cuff opinion, now, no facts, but let us say that a drawbar HP test on a lightweight (36 flywheel HP) tractor yields 25HP and that peak/limit occurred as result of loss of traction. Now I install a 72hp engine of same weight(aluminum, magnesium, etc.) and repeat and of course, the drawbar test still yields the same traction limited 25hp . Now if I were the manufacturer, do you think I will advertise 25 drawbar or 72 flywheel HP?
 
Well the rest of the story goes the way of current electric motor
ratings: Peak HP which has absolutely nothing to do with what you
are using when operating the product. But it is a nice big number
making the customer think they are getting something extra for
their $$$$$. Marketing Hype!

Mark
 
When you have a powerful engine in a
lightweight tractor the peak drawbar power will
be at higher ground speed. The drawbar pulling
force may not be be any greater but with the
increased speed the power produced will be
proportionally higher. Higher speed operation
with a light, powerful tractor is often more
efficient since less of the engine's power is
required just to move the machine. The size of
the implement that a tractor can pull is only
half of the drawbar power equation - the speed
at which that implement can be pulled is the
other.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top