Prinoth Steering Question

[Dan in Napa CA]

Greets, all. I have a new-to-me Prinoth T2, circa 1988-90, I-6 diesel, full hydrostatic, that wants to track right when the levers are pushed forward equally. To get it to go straight, I have to keep the left lever pulled back a good inch behind the right one, which as you might guess has caused some very terrible and dangerous left hand cramps while operating. Severe.

The question is: Do any of you have thoughts about whether a T2 of that era had any control lever adjustment to get it to track straight? It's out of balance - maybe I'm looking in the wrong place altogether (admittedly, I'm a hydro noob). I've been through the operating/maintenance manual and spare parts catalog, and I'm not finding anything in either a schematic or maintenance that shows anything that looks like a likely target. I'm not going to be able to crack into it for a week, so I'm prepping for battle. I suppose I could just call FarWest and have them tell me how much a service call will be. Yeah, right. As a last resort. I'm looking for thoughts, theory, suggestions.

Oh, it's mkntrakes old rig, so you've all seen pictures already. Green, gull wings, flames, microwave, Lost in Space Chariot.... http://www.forumsforums.com/3_9/showthread.php?t=22250 I've seen it enough that I haven't even taken a good photo. Next week, I promise, with snow.

Tracks, wheels, sprockets all good, no apparent leaks. No funny noises. The wicked turbo spin does not bother me at all....

I don't know how long the problem has been there; last owner said he'd run it 5 hours in the last 4 years, and then later said it'd been more like 2 hours. Could be lack of use, I dunno.

With both levers equal, it tracks to the right about 15 degrees, maybe 20. When going straight, it feels like it's pulling 100% on right track and 50-60% on left. Bad right motor? 3300 hours on the clock. It climbs and pushes snow and doesn't complain - it just doesn't track straight.

Anyway, I'm looking for ideas that will lead me down the path to enlightenment. TIA

DiNCA

 

[Snowtrac Nome]

you need to get some gauges on it and determin if you hav a bad pump motor or just a cable adjustment one thing you might try is does it do the same thing in reverse if so likely not a cable adjustment.

 

[Dan in Napa CA]

Gauges, you mean like this one? http://www.omega.com/Green/pdf/FLKIT.pdf

Being as I'm a hydro noob, I'm not sitting on a box fulla test equipment, although I do have one of those fancy laser tracking infrared thermometers. I'm going to have to find out what pressures and flow I should be getting, which would make a test gauge more useful.

I like the thought about reverse, and I'll be checking that out. The other thing will be seeing if it tracks right in low speed operation. There's a "2 in - 4 out" valve body with 2 electric solenoid valves that according to the schematic is a brake systems line and driving speed change (tubazioni impianto freni e cambio velocita) . Gonna have to learn Italian now. Could be the right motor's speed change solenoid is sticking in low after sitting for so long. Or it got disconnected or rats ate the wire.... Easy fix, easy fix, easy fix.

You're right, it could any number of things. I figure to operate and observe symptoms/conditions, inspect, then form a hypothesis and test it. Problem with being a noob is that I have a steep learning curve - not enough hydro experience to be able to know where "the obvious" resides. I was half thinking that some of the Bombardier guys might have seen a similar problem and could throw some "obvious" things to look at. I'm gonna have to bone up on a bunch of things, including how to work a pressure/flow test gauge....

It's probably well overdue for a hydraulic system flush with fresh fluid and filters. 4 years, 2 hours operation, and minimal (?) maintenance? There's a bunch of deferred maintenance to be done, and I may shake loose the problem during that phase. Realistically, I should just go through the rig starting with setup, then through all maintenance items for 3200 hours, change filters, fluids, etc., etc. Major service items.

I DO happen to have a spare 4 leaf clover; maybe I just drive it for 10 hours and see if it fixes itself. Yeah, that's the ticket.

Cheers,
DiNCA

 

[Snowtrac Nome]

To be honest i'm not real familiar with that system the ones on bobcats run two pumps and 2 motors with levers controling the flow tthrough the motors. i would have to look at the hydraulic schematics and you should have test ports for gauges to check pressure from if you don't than one would have to install some t's before and after the valves if you are driving off a single pump through a priority valve you may have a valve or motor issue.

 

[Dan in Napa CA]

Don, you are a glutton for punishment. It's an Italian machine, so looking at hydraulic schematics is like looking at a bowl of spaghetti. The road leads to madness, MADNESS I tell you.

The system has a twin pump, one side runs left, the other runs right. The left side also has the blade/attachments pump; the right side has the tiller pump. I'll try to send you a PM with the parts catalog front side hydraulics diagram and index, it's about 170 kb. The index doesn't actually describe all the numbered parts; I have 3 more manuals that when read together give probably 80% of the necessary information. None of them describe how the system actually works, but it's Italian so it can be figured out with much trial and error. Like adjusting desmodromic valves on a Ducati. If you can bear to look at more, I can piece together as much of the bigger picture as I have available.

It's like looking at an Italian Supermodel - you can't tear your eyes away, but you know you wish she would just hurry up and slap the crap out of you so you can return to your senses and get back to business.

DiNCA

 

[Snowtrac Nome]

you may try alaska snowcat he is pretty buisey now bu drop hin a pm he will get back with you he is pretty familier with the different hydro drive systems your gauge was cool you will likely need 2 gagues so you can check pressure at the pump and pressure at the motors. this way you can see if the supply to the motors is equal.

 

[undy]

Dan,

That sure is a pretty snowcat, even if it's got some issues.

Interesting analogy to the Supermodel. My "other car" is a Pantera. I was told that being an Italian car, it didn't even need to run. It was enough just to look cool and sexy sitting by the side of the road. I've got my cousin's MH900e sitting in my shop, and it's certainly got the look too. Gotta love those Italians, eh?

 

[Snowtrac Nome]

Dan,

That sure is a pretty snowcat, even if it's got some issues.

Interesting analogy to the Supermodel. My "other car" is a Pantera. I was told that being an Italian car, it didn't even need to run. It was enough just to look cool and sexy sitting by the side of the road. I've got my cousin's MH900e sitting in my shop, and it's certainly got the look too. Gotta love those Italians, eh?

is that the secret of the krustys they just sit and look pretty but never run they must be made in itialy too

 

[Dan in Napa CA]

Good looking rig, aye, true dat, thx. That turbo spinning up when it starts to make power is drop dead sexy, too. And but for the tracking to the right, it goes where it gets pointed. If I can get it dialed in the way I think it should be, I may give up the snowmobiles altogether. Although there's a lot to be said for "able to go faster than 17 mph."

Italian, doesn't even need to run, . MH900e [drool] all hail Hailwood! And the 916, say no more. I have a plated '04 Husqvarna TE450 from the MV Agusta era, so Italian. The whole thing makes sense in the context of Meatballs - Swedish, Italian, all good. It's funny how you can put up with little quirks when it's Italian. Like sometimes the electric leg doesn't work, but then it does 5 minutes later. No worries, it's Italian, the carb has an accelerator pump and the DOT knobby throws a monster roost while a guy battles to keep the front wheel near the ground. When they run, it's maniacal cackle and $hit your pants fun.

 

[brianf]

look at drive pumps see if you have electronic controls on the side,or cables. this is a good starting point,both of these controls have to be serviced and set up, this system may have a drive card, which again may be adjustable. but look at pumps ,type of control manual or electronic this may be a great starting point

 

[Dan in Napa CA]

It's all hydro. Nothing electric, although there are limit switches at the pilot controls. The high/low speed and the parking brake are solenoid activated. But no computers, cards, potentiometers or wires (except for lights and stuff). Good old plain, basic fluid and hoses everywhere like a nest of spaghetti. Old school.

There are 6 hydro lines that go to the controls, 3 to either side. The sticks have neutral, forward and reverse, they're proportional directional control valves. Pressure comes from the dual pump, then leaves the control valve and returns to direct the flow to one side or the other of the boost pump. From there, it's to one side or the other of the drive motor, which is variable displacement. From motor, to radiator, to filters, to tank. Open loop system. What's got me fried now is that I actually have to know something about hydraulics beyond how my log splitter works.

There's a switch on the dash that actuates a solenoid for changing from low to high speed, a pressure line to the solenoid valve block, and a line from the block to each motor. The cat responds to the switch, at least on one side. Not positive about the other side, but I'm having a hard time believing that a single solenoid, if functioning, wouldn't supply pressure to both motors. Possible, but not probable in my book.

I'll be digging into it on Tuesday. I'm camping on taking off the tower cover (basically a metal piece that would be a bellows if it were rubber) and expecting to find that on each side of the lever there will be a threaded actuator for each side of the control valve, that can be adjusted by loosening a lock nut, lengthening the actuator, and then retightening the lock nut. Test and repeat until desired results are achieved.

Or drink heavily.

 

[Dan in Napa CA]

Just an update: It tracks straight in low and reverse. When shifting from low to high speed, it slews hard to starboard. I made a great sidewinder down a long straightaway from switching from low to high and back, while trying to keep from running into ditches and off the side edge.

This leads me to believe it's either the high/low switch solenoid (not likely, because it is obviously shifting the left motor, and it's the same valve for both motors), the switching circuit on the right motor (possible, although the motor otherwise works perfectly), or a third choice - damage to the line between solenoid block and right motor.

I'll have a crawl under and inspect this weekend, to see if maybe there was damage to that line in transport. After that, it'll be "wait for snow to melt" and get some pressure testing equipment.

An interesting aside, it turns out there's another Prinoth, a T2S, on the hill. I may get to do some comparison viewing to help sort this out.

DiNCA

 

[muleman]

Is there any speed sensors for the drive motors? Could be one side is lagging due to a bad input not allowing valve to fully open for the high speed circuit.

 

[Alaska Snow Cat]

I have no experience with Prinoth but I used to have a Thiokol 3700 that had the two speed hydrostatic system and I wouldn't be surprised if they were similar in design. The 3700 had "variable speed" drive motors that had a two position swash plate instead of a fixed swash plate. Each side had a small electrical controlled hydraulic valve that controlled the angle of the swash plate depending on what position the operator put the electric switch.

The problem could be a wiring issue on the side that does not work, or the valve itself which was external mounted in the tub on the 3700. It could be a problem inside the motor itself which could include the swash plate or any of the shuttle valves or pressure relief valves.

First I would check to see that you are getting good voltage to the valve on each side when the switch is activated. Then once I knew how the system works and had a clean shop environment, I would then dive into the hydraulics.

I had a couple of Bombardier BR 300s parking in my yard last year while they were doing contract work in my area and one of them started having some steering issues with the computer. I told the operator to get ahold of Prinoth since they now own and support Bombardier cats and within the hour their tech support had helped them figure out the problem and get them back on the trail. I highly recommend you contact them if your T2 gets any more complicated than a broken wire. Hydrostatics are not real complicated but have some very precise moving parts that you do not want to damage or introduce any contamination into. Prinoth in Grand Junction is (970) 242-7150

Good luck

 

[Dan in Napa CA]

muleman - Nope, no speed sensors. It's all old school hydraulics, just valves and hoses, pumps and motors. A switch that controls a single solenoid that pressurizes the emergency brake release on both drive motors, and a switch that controls a single solenoid that pressurizes the swash plate angle in each motor to run high or low speed. The left motor switches from high to low, but the right is stuck in low and won't switch.

ASC - From your description, the Prinoth is probably similar to the 3700, except that there's a single solenoid valve that controls the angles of both swash plates. The left motor switches, the right motor doesn't. So, unless there's obvious damage between the solenoid valve block and the right motor, I'm thinking it'll be internal on the motor, as you suggest. Stuck valve or something similar - it hasn't been used much in the last few years. We'll do the inspection and go from there. "Clean Shop Environment." Nice. Need to build a shop, yup, although I'm sure Miss Kate wouldn't mind one bit if I pulled the motor to rebuild on the kitchen table, nope. One good thing, Prinoth has a Reno shop, and they get over my way to service the Government's groomer. If need be, I can maybe piggyback a service call. I've already talked to John Swartz at Farwest USA, good people.

Thanks for the help and ideas, Gentlemen. I'll keep you posted as we unwind the mystery.

DiNCA