littlejoe said:
hillsdown said:
We have a Tomcat 255 turbo skid steer and know that there is a valve on it that you switch over from summer to winter use . BUT cannot remember where it is and the book does not have any reference of it. Does anyone know here that valve might possibly be ?
Desperately need to find it as it does not run worth a darn when it is cold, it starts just fine but quits as soon as the cold 10w30 oil moves around. We switched it to a light hydraulic fluid for winter but that has not corrected anything .
Thank you
Some John Deere industrial stuff had a valve you could close to take hyraulic load off while starting and warming up machine.
With closed center system and nitrogen 'accumulator' to pump against, j d would instantly try to get 2000 psi. On our loader, engine would crank easier if you raised bucket while cranking (if you din't do first item i mentioned)
is hydr pump on end of crank? anyhow--wherever it's at--see if there's some dohickey you can turn or switch to take it outa service for a bit
Anyway---an 'open center' system is common on lots of equipment---if you were able to look into a valve you weren't using, you could see right thru it---oil just goes round and round till you divert it. Disadvantage is that you're wasting power and building some heat.
'closed center' is used by j.d. and cat---the center is closed till you cycle valve---pump on our little loader will try to pressure up to over 2000#, then cut production from top of 25 gpm to about 3gpm---lubrication of trans, steering, brakes.
it's pumping against what i call an 'accumulator' (no doubt the wrong name)---this is like an enclosed cylinder with just the piston in it. hyd t'd in on one end. on other side of piston, pressured up with 500psi nitrogen when at rest, no hyd pressure. this works as kinda a shock absorber for hye system as liquids are incompressible and is also sposed to give you enuf hydr---with dead engine---to pull over to side of road and get stopped.
the hydraulic pump is crank driven and kinda a rotary piston type. No connecting rods, pistons are kinda free floating and driven by sort of a cam, on demand. With closed center, you're not building as much heat, wsting as much power and wearing as much stuff out---at least that's the theory explained to me.
either will run a cylinder---but you gotta have the right valve for your tractor---found this out by buying a post driver that worked really good for the other guy.....