My disaster

[relaqbr]

First off Im glad you got off the machine and didnt get hurt...With that said Im goingto go out on a limb here and say that given your explanation of what happened,my educated guess is that the machine may be slightly low on hydraulic oil,<sinp>

Thanks for the well wishes and idea but it was not low on fluid before or after.

relaqbr
After reading your post about a run away machine using hydraulics drive, I thought of the following things. If the machine is using a hydrostatic driven transmission, about the only thing I can think of is that the lever controlling the camplate came loose, or was jammed, forcing the camplate to maximum and increasing speed. The camplate in the hydro has a spring that keeps it in neutral until you push or pull the lever to go fwd or rev. The cable controlling that camplate could have jammed, and the accident caused it to become unstuck. .
You might never know what caused it if things are working correctly.

There is probably an emergency stop, which is used to kill the engine.

One of the things I experimented with was turning the key off on the hill as a emergency brake. Works OK. .

relaqbr
After the accident, did the machine operate normally?

I had a similar situation with a stuck control cable, controlling a hydrostatic transmission. It caused max speed with no control.

I have a new cable on order now.

Thanks for the post J_J I got some useful info googling toro hydrostatic camplate problem. The unit seems to run the same as it did before the problem. I don't have a speedometer but I believe that it was actually going faster than "top speed" when I hopped off.

This guy did.... LiveLeak.com - Idiot Tries To Navigate Tractor Down Stairs
(not my title by the way....)

I hope that dolt hasn't bred.

So do I. I do hope he was not badly hurt as well. He could have landed on his neck. Be a bummer to be paralyzed for life for being an idiot. He could also have been run over if it was my tractor -- as mine did not stop when I let go of the bar and hopped off.

Update: I have come down several times now. (one of the reasons I have not posted recently is that I have been out playing .) I decided to have the motor running at idle so that I could push the bar forward without it going much faster, to see if that would allow me to control the steering better. And it does. So with that as a backup plan I have tried some other variations and the result is that I can navigate that stretch of road fairly comfortably now

Thanks to the group for all the help and well wishes. And I hope that if any one has any further ideas about what might have happened that they post.

 

[EE_Bota]

I know this is an older thread, but I had a thought...which is rare enough in itself...

Suppose while the machine is going down hill, the swashplate is still tilted in the forward direction long before you feel there is going to be an issue. At the point where the machine is increasing its speed under its own weight, the hydraulic fluid from the pump in not driving the machine, rather a vacuum is starting to develop to slow the machine down. Suppose this reaches the point where a relatively full vaccuum is drawn on the fluid column from the pump to the motor. Vacuum is -15 psi, nothing compared to hydraulic pressure, and it really wouldn't slow you down at all. To slow down, you would have to reverse the pump's swashplate to provide pressure in the reverse direction.

I am (relatively) sure you did reverse the swashplate at some point to drive reverse pressure to the motor, so let's think freely about what could cause that to fail. Suppose there are volatiles in the hydraulic fluid that are able to stay diffused through the fluid under reasonable positive pressures at that operating temperature. What if at that same operating temperature, and a negative pressure (a vacuum) the volatiles bubble out making so when you reverse the swashplate, you don't really have bona fide fluid in the pump motor path to drive reverse direction forces.

Possible?

 

[Just Bob]

Interesting thoughts Ebota. I know on a track motorcycle that runs really hot brakes that if you have one iota of water in your fluid it will boil and create an air bubble that will put you straight into a wall.

If the OP had old hydraulic fluid with contamination your theory could be right on. And running on hills would put more stress on it and make it heat up more.

 

[RJA.Ilex]

It sounds to me as if you are running close to the limits of the machines on your drive (35 degrees is quite steep). I am not familiar with the machine in question but the manufactures maximum recommended angle will be based on twice the static tip angle.
As for the machine running out of control I would suggest that the pressure release on the hydrostatic trans blew, this effectively limits the braking force available on hydrostatic machines.
As for how to tackle slopes safely, bucket down in the UK on telehandlers the recommendation I have heard is ankle height, and climb/desend slopes with the heavy end uppermost. This means the direction of travel could change depending on the load being carried.
As for hitting the emergengy brake, this is likely to push the machine over the edge.
I have had similar experences in the past but never actually lost the machine, the last one ws on a JD outfront rotary mower (1340?) which nearly ran out in heavy traffic.

 

[relaqbr]

I know this is an older thread, but I had a thought...which is rare enough in itself...
<snip> What if at that same operating temperature, and a negative pressure (a vacuum) the volatiles bubble out making so when you reverse the swashplate, you don't really have bona fide fluid in the pump motor path to drive reverse direction forces.

Possible?

"I had a thought...which is rare enough in itself..." Oh I am sure NOT

Is pulling a vacuum the same a cavitating? I think that you are right. I do regularly go down this hill now and the machine rattles, gurgles, and speeds up as it gets to the steep part and I then manually pull back on the drive handle which slows it down. The company rep (not the manufacturer's) has seen and heard it (took a month to get them out) and says that it will not hurt anything. Any opinions? Also anyone know the mm of Mercury needed to pull a vacuum in pure clean hydraulic fluid or where to find it?

I know on a track motorcycle that runs really hot brakes that if you have one iota of water in your fluid it will boil and create an air bubble that will put you straight into a wall.

If the OP had old hydraulic fluid with contamination your theory could be right on. And running on hills would put more stress on it and make it heat up more.

Steam bubble?
The tractor was new (less than a month old and 20H on it. It had not been worked much before the adventure. However, I do not know for sure if anything had happened to contaminate the oil before I got it. I think that I will look closely at the fluid and maybe just replace it now.

It sounds to me as if you are running close to the limits of the machines on your drive (35 degrees is quite steep). I am not familiar with the machine in question but the manufactures maximum recommended angle will be based on twice the static tip angle.

I have since found out it is over the recommended slope, yes 35deg IS steep but it is my driveway! And the salesman knew that when he sold it to me. ?

As for how to tackle slopes safely<snip>...

Well and with a grain, smidgen, iota of salt. I don't like backing up the whole way. So I go VEEERRRY carefully if I need to go up without the bucket on the front (ie. back heavy).

I have had similar experences in the past but never actually lost the machine, the last one ws on a JD outfront rotary mower (1340?) which nearly ran out in heavy traffic.

Well I assume the final outcome was as good as mine as we are both here discussing it

Thanks to the three of you for great thoughts. And I hope you are having very happy holidays.

Bob

 

[SPYDERLK]

It sounds to me as if you are running close to the limits of the machines on your drive (35 degrees is quite steep).

He must mean a 35% grade. A car, even one that had enuf power, would need 4wd to climb 35 degree pavement if it were wet.
larry

 

[relaqbr]

He must mean a 35% grade. A car, even one that had enuf power, would need 4wd to climb 35 degree pavement if it were wet.
larry

Absolutely 35% slope/grade Still steep though. Used to try and ride a bicycle up a 32% in Los Angeles once a year.

Bob

 

[George G]

When you are going down hill. Your loader will try to roll down the hill. When it dose, your drive motors will start to act like pumps. They "the motors" will start building psi between the motors outlet port and the pumps inlet port. Normally, this will slow the vehicle down. Now, if you are going down a hill that is to steep, or, you are going to fast. When you try to slow down. The pump won't pull oil away from it's inlet fast enough. So, the psi between the motors outlet port and the pumps inlet port will continue to increase til the crossport relief valve opens. At this point,no slow down, no streeing, no reverse. The only thing you can do is drop the bucket, and hope that slows you down enough for the cross port relief to close, and bring you to a stop.

 

[woodlandfarms]

So, how do you calculate the difference betweem Percent and Degrees in slopes.

My tractor is rated at a 45 degree slope (sideways). What would that be in Percent?