PT Rises from the Ashes

Sedgewood · Sep 11, 2003

My new filtered vent cap. I machined off the old cap and drilled and tapped mounting holes for the new one. The new one has no dip stick but there is a screen which hangs down just the length of the old dip stick such that if I see oil covering the bottom of the screen the tank is up to level.

While I had the cover off I spent a fair bit of time wiping down every surface I could reach. In addition to the larger bits like welding slag the whole interior was covered with a thin film of very fine particles. Dust from all my road work last year maybe? There's a scary thought.

Sedgewood

MossRoad · Sep 11, 2003

May I suggest getting going by acquiring some new toys rather than my calamatous approach which, effective as it may be, has proven to be a rather too traumatic way to acquire site material!? 

Sounds like words to live by!

ACQUIRE NEW TOYS!!!

Maybe I'll get a tattoo of that on my .... /forums/images/graemlins/tongue.gif

Charlie_Iliff · Sep 11, 2003

PT's limited to absent assistance in the rebuild 

Dennis:
Although John had to go it alone on his rebuild, the Power Trac attitude was attributable to the insurer's threat to claim against PT. Although I think Power Trac over-reacted to that threat, and lost a sale, I have not heard of any other reports of lack of cooperation or support when repairs have been needed. Generally, Terry's advice is good, and parts are sent promptly. Just don't threaten to sue 'em and you'll be fine. /forums/images/graemlins/grin.gif

duane · Sep 11, 2003

John,

I agree. The 3 main issues with a hydraulic system, heat, pressure and cleanliness.

Pressure: covered by the safety valves
heat: very interested in what you get for maximum hydraulic reservoir temps
Cleanliness: Other than original construction or filter replacements, the on-going sources for possible contamination are the quick connects and the vent. I think the variable volume pump and wheel motor circuits should be okay. Nice job with the vent modification. I keep looking for a filtered vent cap that will go right on the existing mount. I'm still looking.

Duane

Sedgewood · Sep 11, 2003

Charlie: Dennis:
Although John had to go it alone on his rebuild, the Power Trac attitude was attributable to the insurer's threat to claim against PT. Although I think Power Trac over-reacted to that threat, and lost a sale, I have not heard of any other reports of lack of cooperation or support when repairs have been needed. Generally, Terry's advice is good, and parts are sent promptly. Just don't threaten to sue 'em and you'll be fine. 

I agree. It was my insurer's threat that caused the over-reaction. Factory support has generally been good where no threat of liability is concerned. Mention the "L" word and they get antsy.

Sedgewood

Sedgewood · Sep 11, 2003

duane: the on-going sources for possible contamination are the quick connects and the vent. 

There's another - cylinder rod seals are considered to be a major source. from what I read, a separate reservoir is recommended for hydrostatic drive.

Sedgewood

bmac · Sep 11, 2003

10W-30 gets too near the viscosity spec limit on the hot end to suit me 

sedgewood,
please forgive my sick sense of humor, but here goes:

I guess anyone who's used to running their tractor ablaze would be sensitive about performance on the "hot end".

Sorry, I couldn't resist. Nice job on the restoration.

BTW, is there a thread that addresses exchanges between you and PT and the lawyer? I must have missed it.

Bruce

marrt · Sep 11, 2003

PT changed the vent cap on all new production tractors. I forgot to ask if the new vent cap would fit the older tractors. I also did not ask why the change was made. At the time, my thoughts were elsewhere. Anyway, FYI.

marrt · Sep 11, 2003

I don't think Pt's filtration is sufficient. Consider the following quote:

"Hydraulic oil straight from the drum, has a typical cleanliness level of ISO 4406 21/18. A 25 GPM pump operating continuously in hydraulic oil at this cleanliness level will circulate 3,500 pounds of dirt to the system's components each year!"

WOW. That's scary. Also, suction-side filtration is generally not recommented due to the potential to create cavitation. However, I don't see a reasonable alternative. I don't think its practical to have filtration only on the return-side. This would mean fluid in the tank would need to be very clean at all times. In the PT design (any design in my view), this isn't practical.

Edward_DiMaria · Sep 11, 2003

Guys - I know we have been going around and around on this filtration issue - it seems to creep its way into every thread -
So I thought that we should really get this nailed down so all can be confortable or unconfortable given the way it works, comparables, alternatives etc.

I seem to remember on one thread that no filtration was taking place without tramming - but then someone clarified that and informed us that the charge pump circulates the fluid (fliter and through the cooler)

But many folks still seem to have big concerns about this (besides the welding slag / etc - which is a manufacturing defect not a filtration defect)

Some folks proposed separate filtration for the tram circuit - which seems to be a good idea but can it be done? - Also why is the suction filter design a bad choice? I asked PT - "is 100% of the oil filtered and the answer was yes - I guess I am just confused by all this

So I ask the question - what are the variuous methods of filtration - how does the big manufacturers of Skid steers do it? like Bobcat, Cat etc

(It would seem to me that this would be a good comparison because they use the same type pumps bolted directly to the engine except they have two tram pumps (one for each side)
Not sure how many other pumps they use but it has to be similar

One other thing is that it would seem that we would be constantly talking about pump / wheel motor failure if there was a serious problem with filtration and to my knowledge I only recall hearing about one such failure (a wheel motor on an older machine - was it Davesick?

What does everyone think - maybe we need to make this a thread - I know we have a thread in hydraulic fluid alternatives but not filtration

Sedgewood · Sep 12, 2003

Edward_DiMaria: Also why is the suction filter design a bad choice? I asked PT - "is 100% of the oil filtered and the answer was yes - I guess I am just confused by all this 

This to me is a very confusing topic. I don't think a suction filter is necessarily a bad choice. For one thing it ensures the oil entering the variable volume pump and wheel motor circuit just has been filtered. It does require faithful filter changes though. A lighter bypass valve spring is used and if one fails to change the filter before it clogs the bypass will open and dump the dirt in the filter straight into the pump. I've just added a vacuum guage to my filter to monitor filter restriction. PT's requiring 50 hour filter changes I suspect is very conservative and the vacuum gauge will give me a handle on whether less frequent filter changes are a possibility. Not to be lazy or save money but to limit the number of times the system is opened to possible contamination.

One other thing is that it would seem that we would be constantly talking about pump / wheel motor failure if there was a serious problem with filtration and to my knowledge I only recall hearing about one such failure (a wheel motor on an older machine - was it Davesick?


I don't know that filtration is a problem. Much of the material I've been reading is aimed at industrial applications where down time as well as the cost of big systems is a major item. There is a trade-off between cleanliness and component life and a point of diminishing returns where the benefit of further cleanliness doesn't warrant the next expensive step. I don't know what PT uses as a design life for these machines, but it's probably reasonable to think most will never see a second engine. So there isn't much point building in a cleanliness level that would give hydraulic components a life expectancy beyond engine life.

I may have mislead the forum here a bit. I'm really not obsessing on this much beyond trying to gain a basic understanding of how it all works. I just put the filtered breather on because it seemed an easy no brainer as long as I had the system open. And the vacuum guage. The cost / benefit seemed obvious. Same with the change in fluids. I wouldn't have considered going through all the hassle of changing fluids in a full system.

Sedgewood,

Sedgewood · Sep 12, 2003

bmac: guess anyone who's used to running their tractor ablaze would be sensitive about performance on the "hot end". 

/forums/images/graemlins/laugh.gif

 BTW, is there a thread that addresses exchanges between you and PT and the lawyer? I must have missed it. 

No thread. I kind of kept quiet about all that then eventually pointed the forum to my web page that describes my ordeal leading to an insurance settlement. The astute readers of this forum picked up on it there.

BTW, astute readers, this may be of interest. To send out a feeler and try to get a handle on my current relationship with Power Trac, I emailed Kristy Asbury to let her know I had the 1845 restoration finished and asked her to please let me know if and when Terry might be free to talk with me again. She replied Tuesday in part:

"Terry is working the coal show today and tomorrow - I will have him call you Monday."

Sedgewood

bmac · Sep 12, 2003

The astute readers of this forum picked up on it there. 

Astute is something I've never claimed to be. /forums/images/graemlins/grin.gif

 "Terry is working the coal show today and tomorrow - I will have him call you Monday." 

I'll go out on a limb here and guess that the Coal Show is not being held in Vegas. I need to get a life. I'm now envisioning mining equipment manufactures displaying their goods with dancing girls wearing the big feathery things (or less), hard hats, maybe a little coal dust on their cheeks (face) carrying a pick or shovel...... I need professional help.

MossRoad · Sep 12, 2003

Just a guess, but I'll bet this is it.

Bob999 · Sep 12, 2003

I've just added a vacuum guage to my filter to monitor filter restriction. 

Is this mounted on the bracket for the filter?

A previous post had pointed to a Grainger catalog that listed a pressure guage for mounting on the inlet side of the filter mount to monitor filter condition.

What caused you to use a vacuum gage rather than a pressure guage? What vacuum guage did you use? At what level of vacuum do you replace the filter?

Edward_DiMaria · Sep 12, 2003

Hey Sedgewood - is Columbia traqctor the guys I see at the Dutchess County Fairn every year? - I assume you go to it - Most of those folks who present there are really good folks

EDM

marrt · Sep 12, 2003

Not to be lazy or save money but to limit the number of times the system is opened to possible contamination.


Good point. It's very easy to introduce contamination into the system when doing routine maintenance.

 I don't know what PT uses as a design life for these machines, but it's probably reasonable to think most will never see a second engine. So there isn't much point building in a cleanliness level that would give hydraulic components a life expectancy beyond engine life.


I think this comment is spot on. From reading this forum for a while now, my perception is that most homeowners put less than 200 hours per year on their tractor. I believe the Deutz engine has a design life of 10,000 hours before failure. That would translate into 50 years of use. Even if you cut the number in half, its still a long time.

So, its really a question of "what's good enough," not "what's optimal." The tradeoffs for PT are significant. Let's take a hypothetical example. Let's assume that PT could spend another $200 in manufacturing cost to create dedicated hydraulic reservoirs and add a couple additional filters with water separators. Further, let's assume that these changes would increase the design life by 25%. I think most people would say they should make the changes. However, if PT concludes that only 10% of users would every benefit from the changes (i.e., the other folks would not use the tractor enough or would not keep the tractor properly maintained so that the changes were effective), then PT would effectively spend $2000 ($200/10%) for each owner who would actually take advantage of the changes. Therefore, PT would not make the changes, even though they seem "cheap."

However, if PT offered a “Severe Service” package that included these changes for only $300, we'd all buy it. After all, $300 on a $15K tractor purchase is only 2% more. Sounds like a deal for a promised 25% increase in design life.

I think most folks who buy PT's like to “improve/modify” their equipment. I know I do. Trying to determine the optimal filtration for the PT, even though it may not make sense financially given the actual risk/design life of the tractor, is just part of the fun.

duane · Sep 12, 2003

John, your right, rod seals are also a source of hydraulic contamination.

Here is my two cents on the green PT Hydraulic filtration, but probably applies to the red PTs as well.

At full RPM, the integral charge pump to the variable volume pump is moving about 5 gpm. This means that about 5 gpm is being pulled through the suction filter at 10 microns. At this flowrate, the contents of the hydraulic reservoir is filtered every two minutes.

As I understand it, the piston assembly in the variable volume pump is the most sensitive to contamination (probably the most expensive unit as well). The suction filter protects the charge pump, piston pump and wheel motors. Thus this circuit should be adequately protected.

The tilt, lift, steering and PTO circuit is fed from tandem gear pumps which combined is moving about 12 gpm. As everybody is aware, no filtration on these circuits. I believe that PTs design relies on the tram circuit to keep the reservoir fluid clean. (Are the gear pumps, cylinders, valves, hydraulic motors in this circuit a little less sensitive to contamination?) Likely that the oil in these circuits is not as free of contamination as the tram circuit, and that ingestion of damaging particles is possible since there is no suction screen/filtration. In reality, I’m not sure of the long term consequences. I have not seen any trends in failure of components in these circuits, although most of us only have low hours. Reports back from tractor owners in the one thousand hour and up range would be informational.

PT does manufacture the Lo-Trac commercial mining vehicles. The design and operating experience from this side of the business must be their basis for the Power Trac machines. This should give us a good amount of confidence in the design. The web-site indicates that these machines also use a crankcase oil in the hydraulic system.

John, after you have worked your 1845 machine hard, could you post some hydraulic reservoir temperatures along with the ambient temperatures. Curious to see where the bulk temperature settles out at.

Duane

Sedgewood · Sep 12, 2003

Mossroad: Just a guess, but I'll bet this is it. 

Bluefield WV, why that's hardly 20 miles up the valley.

Sedgewood

Sedgewood · Sep 12, 2003

Bob999: Is this mounted on the bracket for the filter? 

No, it has 1/8 mip threads and screws directly into the guage port on the pump side of the filter housing.

What caused you to use a vacuum gage rather than a pressure guage? 

Uh... the filter is on the suction side and there's a vacuum there? /forums/images/graemlins/tongue.gif

 What vacuum guage did you use? 

MSC part number 56479157 (1-1/2 inch back inlet 30"hg-0 $14.73)

 At what level of vacuum do you replace the filter? 

I don't know yet /forums/images/graemlins/tongue.gif I don't seem to have the info right at hand but I seem to recall seeing somewhere (on Gesen web site perhaps) that the relief valve is set at 3-5 psi and I see quickly in the Sauer Danfoss literature (though I'm not sure I have the right application info) a design drop across the filter of .1 bar and a filter changeout at .13 bar (I don't have the conversions right at hand nor the time at the moment to really think this through) My initial guage reading is 5" hg at full throttle with a clean filter.

Sorry to be less than coherent here,
Sedgewood