Buying Advice Done with hydrostatics

   / Done with hydrostatics #81  
I believe there is a big difference between part throttle on an air cooled gas engine and part throttle on a liquid cooled diesel.
On hot days those gas engines need all the air they can get to stay cool apparently and the benefits of more air seem to outweigh
higher fuel usage and wear/tear on machinery. I think this is also because during warranty period manufacturers don't want to pay for cooked engines due to clogged fins and coolers so they engineer the air flow for worst case, maybe the cooler being half plugged shut.

I don't see hydro trannies getting that dirty, so it's just air flow, almost all the zturns have fans on top of their hydro units.
So clearly heat is an issue for them. Lower rpms means those fans are running at lower speeds, I can see the need.
The hydro trans on my ancient Cub Cadet is a work of art, neat looking finned aluminum case, looks like Buck Rogers could fly it to the Moon...
 
   / Done with hydrostatics #82  
Hydro Gear makes about 5 levels of HST rear transmissions. The lowest end Cub Cadets use the lowest grade hydro, just like everyone else. About 4 grand you get their next to best trans, and the top tier Hydro Gear commercial units are in the 7 grand range. Usually better motors/trans as you go up in American dollars... [ Cub Cadet wise ] Hydro Gear used pressed powder gears in their first two grades of trans, with actual machined metal gears higher up.

Thanks Jerryk that sure is good to know as I may need a new mower soon . I have an old toro wheel horse hydro that is over 20 years old and still going , it seems to have slowed down a bit , and I do change the oil in that tranny quite often .
 
   / Done with hydrostatics #83  
My understanding is WOT is to reduce the stress to the charge pump, and main pump for the hydrostatic transmission. The pistons? in the charge pump like to take many more small bites of fluid than larger bites at lower rpm.
I read about this years ago, and haven't been able to find the article.

Also found this, looks like low viscosity JD fluid is about at 5w oil.
Viscosity Charts - Bob is the Oil Guy
 
   / Done with hydrostatics #84  
The hydrostatic tranny on my 2009 cub-cadet with only 300 hours is kaput. This was my second hydrostatic mower, the previous one was a Toro that lasted much longer but it still went too just before I bought this one. No more.

Anybody know off-hand the last year the the ford riding mowers had classic manual transmissions? I'll be looking for a 54" or bigger deck. Or maybe there are current models with standards?

TIA

I have a 2006 Husqvarna with 400 hours on it (YTH2448) paid 1700 for it, runs great and 0 problems, have 2 acres to mow and have no complaints about the transmission. I always mow WOT and make sure the fan over the transmission is clean-also mow on a 30 degree slope. When it goes I will buy a 54 inch deck for my MF....
 
   / Done with hydrostatics #85  
I mow at WOT. My grasshopper has 2200 hours on the hydraulics. I doubt very many lower end gear mowers would even make it that far.
 
   / Done with hydrostatics #86  
I still have my 1983 Cub Cadet 982 hydro garden tractor. It got a new engine 20 years ago but has been very dependable.
 
   / Done with hydrostatics
  • Thread Starter
#87  
Wide open throttle

Thanks, I learn something every day. Never heard that one before, knew about full-throttle, firewalling it, balls-to-the-wall but not WOT. That's what I've been using. This CC has been cursed since the day I got it. The deck height cable pulleys were made of plastic and every time the deck took a bounce the cable would jump off, eventually cutting the pulleys. I had my blacksmith make new ones from steel and they've been working like a charm ever since. The deck belt pulley idler was totally cannibalised and almost seized due to wrong assembly, it cost me 5 belts the first two seasons, the dealer couldn't find the problem. I finally did, belts have been lasting two seasons since.
 
   / Done with hydrostatics #88  
WOT is your engine at the highest throttle setting, under load.
I believe High Idle is the engine at full power, NOT under load. Usually get 200-300 more rpm?

for most engines, and my experience is in diesel, you need to hit rated WOT under load or the engine is either overloaded,
air starved, something not adjusted correctly, and basically if you can't hit spec'd WOT, you have a problem you need to fix.
Then once you know your engines will hit WOT under load (my experience was in Detroit 8V71TI's which absolutely had to reach 2300rpm under load)
you ran at 80 to 90 percent of load. But never flat out, or WOT.

I keep forgetting to do this, but my Kubota F mower runs at 3050 WOT, with mower deck on. I want to see what it will do with mower off. That would be
High Idle, if I have this right. I mow at 2600rpm btw. Once upon a time fast speeds like that would have blown diesels sky high, now that's slow for the Asian diesels.

I keep coming back to the WHY on this. Most of our manuals say run flat out. I never do. Every machine is air blasted when done and radiators/coolers always clean before I start.
I'm just surprised hydrostatics aren't designed to work perfectly over a certain rpm, like 300 rpm over idle. Clearly they are not.
Can someone explain in a little more detail why?

My feeling is these hydrostatics should last many thousands of hours without anything other than oil changes. If they are breaking too soon, sure would be nice to know what is
causing that. Tuff Torque isn't going to tell you...they are selling replacement parts nicely I'm sure.

Can someone explain mechanically why it is easier on hydrostatics to run at full rpm? I understand the basics but what actually is stressed
when you don't have sufficient pump pressure? I thought that was when things stalled...not broke.
 
   / Done with hydrostatics
  • Thread Starter
#89  
WOT is your engine at the highest throttle setting, under load.
I believe High Idle is the engine at full power, NOT under load. Usually get 200-300 more rpm?

for most engines, and my experience is in diesel, you need to hit rated WOT under load or the engine is either overloaded,
air starved, something not adjusted correctly, and basically if you can't hit spec'd WOT, you have a problem you need to fix.
Then once you know your engines will hit WOT under load (my experience was in Detroit 8V71TI's which absolutely had to reach 2300rpm under load)
you ran at 80 to 90 percent of load. But never flat out, or WOT.

I keep forgetting to do this, but my Kubota F mower runs at 3050 WOT, with mower deck on. I want to see what it will do with mower off. That would be
High Idle, if I have this right. I mow at 2600rpm btw. Once upon a time fast speeds like that would have blown diesels sky high, now that's slow for the Asian diesels.

I keep coming back to the WHY on this. Most of our manuals say run flat out. I never do. Every machine is air blasted when done and radiators/coolers always clean before I start.
I'm just surprised hydrostatics aren't designed to work perfectly over a certain rpm, like 300 rpm over idle. Clearly they are not.
Can someone explain in a little more detail why?

My feeling is these hydrostatics should last many thousands of hours without anything other than oil changes. If they are breaking too soon, sure would be nice to know what is
causing that. Tuff Torque isn't going to tell you...they are selling replacement parts nicely I'm sure.

Can someone explain mechanically why it is easier on hydrostatics to run at full rpm? I understand the basics but what actually is stressed
when you don't have sufficient pump pressure? I thought that was when things stalled...not broke.

Ok, there's maybe a misnomer in there then i.e. if WOT is wide open throttle then that is a throttle valve position and not an rpm as online definitions that I have found would seem to confirm. In a word: maximum duct breathing. What it might _mean_ though in practice is limit rpm MAINTAINED under design limit load by let's say the governor. THAT, were it to ever happen after a month's use, would mean an engine that is still like new. I'm thinking of the stall-rpm on a big rig, as an indication of engine condition although more than just the engine comes into play.

Back to these HST's, at least part of the problem, according to gossip cause I'm anything but an authority on them, is a lack of cooling or inadequate cooling. I cannot state this as I simply don't know, but IF that's what it is then another pound of aluminum fins and another quart of oil should've been designed-in. According to my dealer the pumpmotors are computer machined to very close tolerances and wear can too easily go out of tolerance for more than just one reason.

Bottom line from my side of the equation is that I don't CARE about the cause, the nitty-gritty, or the whatever rationale, I do not consider 300-hour life as being normal except for biodegradable garbage-bags.
 
   / Done with hydrostatics #90  
As others have said . WOT for cooling . WOT with the forward travel pedal half way down is less stressful to the transaxle vs 1/2 rpms and forward pedal all the way down.
 

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