Hydro power loss? 20%, not on it's worst day!

art · Jul 16, 2004

Hydro power loss? 20%, not on it\'s worst day!

I keep seeing that hydro's loose such numbers of 20 and 40% on this board and I thought do to the number of e-mails sent to me about it that I would put up a few facts. /forums/images/graemlins/shocked.gif I went to the Nebraska Tests which is required if a company wants to sell tractors in that state. The tests are quite expensive and some manufacturers have chosen not to sell there do to the limited market. They are at http://tractortestlab.nl.edu/ These are the two tests that I found that were the worst as some were even closer. I'm using two basically 100 PTO hosepower tractors using a IH hydro 100 test #1158 and a 966 gear drive test #1123. The gear drive weight was 13670lbs and the hydro was 12765lbs The gear on the economy run pulled 6606lbs at 4.84mph at 85.21 drawbar horsepower. The hydro pulled 5,287 at 5.55mph at 78.31 drawbar horsepower. At 75% of maximum pull the gear pulled at 70.99 drawbar horsepower and the hydro at 67.68 drawbar horsepower. Mind you these tests were done over thirty years ago! The newer three range transmissions will be even more efficient then these could test! /forums/images/graemlins/grin.gif Fuel being used will be the largest difference but when doing PTO work or loader work the hydro has long been a winner of efficiency. /forums/images/graemlins/grin.gif I appreciate Junkmans line and I hope this clears up some of the miss information given here. /forums/images/graemlins/smirk.gif

MikePA · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

IOW, the hydro tractor power loss is between 4.7% and 8.1%. /forums/images/graemlins/cool.gif

To20Chris · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

Could you double check that link? It did not work for me - Thanks!

Gary_in_Indiana · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

Mike,

According to my owner's manual, the PTO HP of my JD 4200 is between one and two less HP with the HST instead of the gear transmission. The PTO HP is right at nineteen plus with HST and over twenty with the gear transmissioin so your percentages are right on with my manual. /forums/images/graemlins/smile.gif

JerryG · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

There is a bit of a difference between drawbar hp and PTO hp. The hydro would have more hp loss when used for drawbar hp than for PTO hp.

RichNJKubota · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

Correct link:
http://tractortestlab.unl.edu/

timb · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

Not an ideal comparison, but of course there are limited choices to try to find a match in the Nebraska lists.

Those two tractors are not identical. Close, but not as close as you would have in hydro/gear versions of the same CUT. The IH 100 Hydro starts off with a slightly bigger engine rated for slightly more hp than the 966. The real loss on the IH 100 Hydro from PTO output to drawbar is somewhat higher than 8% - more on the lines of 25% where the 966 is seeing about 15% loss drawbar compared to PTO.

One thought - the quoted 20%-30% loss number may then not be referring to the difference between a hydro and a gear system but rather the absolute loss in the hydro system. But - a gear tranny has it's own parasitic losses - there are no frictionless devices or free lunches - and that loss may often be on the lines of 15% give or take looking at some gross-hp-to-drawbar-hp losses posted.

A guess- but that math would line up somewhere in the same ballpark as the IH comparison shows.

So does a hydro lose you 20%-30%? Yes, but a gear loses you 15%. Call it an actual 10% hydro disadvantage. Whether that matters is up to the individual situation.

MikePA · Jul 16, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

<font color="blue"> So does a hydro lose you 20%-30%? Yes, but a gear loses you 15%. Call it an actual 10% hydro disadvantage. Whether that matters is up to the individual situation.</font>
You are mixing percent differences and percentage point differences.

The percent difference between a 20% loss and a 15% loss is 25% not 10%. (5 divided by 20) That's why it's always best to work from the original numbers and not derived percentages.

((Drawbar hp gear - drawbar hp hydro) / Drawbar hp gear) x 100 = Percent Hydro Loss vs Gear

((85.21 - 78.31) / 85.21) x 100 = 8.1%
((70.99 - 67.68) / 70.99) x 100 = 4.7%

art · Jul 17, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

There are some other facts here that you fellows missed! Like the fact that the hydro actually pulled the weight faster but yet it was less weight. That the hydro actually weighed less by 900 lbs. Tried to change the link but to late! Sorry

gone · Jul 17, 2004

Re: Hydro power loss? 20%, not on it\'s worst day!

you are comparing 100hp tractors,i think yoll find if you compare 25 hp tractors the percentage will grow. the 544 ih hydo if i remember right lost 10 drawbar hp compared to the gear on a 50 hp tractor but my memory could be off that was in the 70's. i can state the fact the gear could out plow the hydro hands down from personal experence on the farm