Sunstrand vs Eaton 1100

[Fordiesel69 271]

Have a really nice 314-H with a mint 260 ish hour M14.  With a 48" deck in tall grass at full speed climbing hills, it will bog the engine down to a halt.  It is definatly the transmission loading the engine down, as my 8-speeds do not do that.  Fast forward to my newly aquired C-160 with a sunstrand.  It has an old unknown K341 16HP that runs perfect.  Somehow it handles it perfectly with almost no bogging down.  Is this becuase the sunstrand is more effieicnet at converting input power to the ground?  The 16HP engine can;t be that much more powerful than the M14.  My M14 is really mint and runs awsome.

[bmsgaffer 2,053]

The hydros should take about the same amount of HP to run, I dont think the sundstrands were any more efficient than the eaton (or they wouldnt have switched for so many years!)

I think 14hp is a little on the short side to be spinning a 48" deck with a hydro at full speed. (I cant cut anywhere near full speed and still end up with a nice cut...) The general consensus is that you loose about 2hp as friction losses in a hydro powered machine versus a straight gear drive. So then you have 12hp left for actual forward motion AND spinning a 48" deck.

I think every HP would be very valuable at this point, so 2 of them would probably make a noticeable difference.

Edited June 3, 2015 by bmsgaffer

[jeremi3210 742]

Iam running a m12 on a c160 auto with a 48 inch deck with no problems at all. I think a m14 should have more than enough power.

[dcrage 630]

The general consensus is that you loose about 2hp as friction losses in a hydro powered machine versus a straight gear drive. 
I

​There was an extensive (least that is the way I remember it) topic on this 2 hp 'drain' for hydros vs gear transmissions in the last couple of years here on Red Square

[shallowwatersailor 3,214]

I recall reading that the Sunstrand was more efficient at putting the power to work than the Eaton. It may have been a thread on a different forum that came to that conclusion. I believe the pump on the Sunstrand runs at engine rpm - or vice versa - and that was the difference. The horsepower drain on hydros vs. manual gear transmission similar to automobiles until they had lockup torque converters.

Wheel Horse was a manufacturer and, just like any manufacturer, put out the best product for the least amount of money. It might be interesting to look at the economy in 1980-1981 in the GT market as that was when Wheel Horse made the change from Sunstrand to Eaton. The country went into a recession in 1980 and suffered through 1981 in the manufacturing industry.

[wheeledhorseman 579]

Sundstrand hydrostatic piston-piston transmission manuals mention that up to 25% of the input energy can be lost as heat! This is a percentage of the HP going through the transmission though i.e. to propel the tractor along.

In practice not many HP are needed to move a tractor that's not plowing or rotavating on the flat or gradual inclines so the actual HP lost isn't great. I can mow with my C-120 Auto for an hour or more and the transmission casing gets only warm to touch, not hot, indicating not too much in actual HP is being lost. If you think about it 2 HP lost (as has been mentioned) = 1.5 KW which would make the trans case too hot to touch I think!

You mention tall grass, full speed, and up hills so expect more HP to be going through the transmission and the losses to be higher but it's worth checking the temp of the trans case - if its getting too hot to touch then you are losing a lot. The transmission can operate up to 180 F but should not go over 200 F. If the transmission is just warm then your bogging down issue lies elsewhere I think.

I've had two bogging down issues the worst case was with the 120 Auto which had an engine that sounded fine, ran fine and didn't smoke but bogged down going uphill mowing. Taking the head off told another story and I ended up rebuilding the engine. The other case was with my C100 which suddenly started bogging down when mowing long grass. This time the issue was with the governor linkage which had slipped introducing slop into its action on the throttle.

Good luck - hope there may be something here that helps.

[Fordiesel69 271]

25% is alot of loss. 

Tranny gets between 120 and 140 on both depending on if it is really hot outside.  But the sunstrand takes longer to get that hot.

The M14 I have still looks like the piston and cylinder is factory fresh.  The gov is opening wide as the exhaust note gets very loud. 

The K341 16HP is very good, but not fresh by any means, but the gov is only cracking 1/2 to 3/4 open, and it just pulls right thru, which is why I am thinking the sunstrand is more effieient.

 

[bmsgaffer 2,053]

The Eaton 11 manuals do not give any efficiency numbers that I have seen.

There's a lot of long winded calculations I did back of the napkin style to come up with a rough estimate. These are NOT to be considered accurate numbers, just gives us an idea. I may be WAY off base as it gets pretty complicated converting input engine power to output power in these hydraulic systems. Also, I did not count for belt drive friction losses which will affect ALL the types of transmissions.

Long story short is that I got about 13hp out based on 18hp in for an Eaton 11 and that makes it about 72% efficient. I know that eaton probably makes their torque numbers safe estimates so it is probably a bit higher than that which looks to be right on the money with the Sundstrand.

Wheel horse designed the eaton to run at 3400 rpm (dont know about the sundstrand) and 700 psi I am assuming for longevity reasons. It can be run at up to 3600 rpm and 800 psi but you may want to put a oil cooler on it if you do that.

[Ken B 3,189]

Are you certain your governor is working as it should and that you are getting max RPM? IMO if it is bogging it down to a halt you have an issue some where...

Edited June 4, 2015 by Ken B

[Fordiesel69 271]

Absolutly it is.  It is thick grass and a good size hill for sure.