PT Rises from the Ashes

[Sedgewood]

Bob999: <font color="red">Congratulations on getting everything back together! </font>

Thanks MossRoad, pajaube, smartguyz, duane, marrt, Bob999. And a special thanks to Charlie for his ongoing support and assistance. It's been a long haul and I've learned a lot, some of which I hope I can share. I've fallen a bit behind on documenting what I've done at my web site. I want to add a better wiring diagram, some better hydraulic circuit diagrams, and some more pictures, etc. There should be enough similarities between the red and green machines that the greenies, who vastly outnumber the reds, can get some benefit from this too. I know I had a hard time making sense of PT's wiring and plumbing diagrams and maybe I can improve on them enough to be helpful.

<font color="red"> I noticed in looking at your parts purchases that you purchased hydraulic fluid (25 gal Kubota AW ISO VG 46 hydraulic oil from Columbia Tractor ) rather than motor oil for the hydrualic system. What caused you to change? </font>

Bob's been paying attention! That was the toughest decision of the project, mainly because I know so little about hydraulics. Sauer Danfoss, maker of the variable volume pump, has some excellent technical info on their web site, in particular Hydraulic Fluids and Lubricants Applications Technical Information and Design Guidelines for Hydraulic Fluid Cleanliness Applications Technical Information, two rather large PDF downloads. I printed these out and studied them until I thought I had some idea what to look for. They recommend many fluids, including motor oil. Other than basic lubrication qualities, the main thing seems to be to keep viscosity within certain limits and ISO VG 46 seems to be the best compromise for my climate, provided it has a high enough viscosity index. Kubota's fluid was what Columbia Tractor had in stock at the time and apparently they sell a lot of it. I never did find any specs on the Kubota fluid's viscosity index though the label says "All Weather" so I assumed it does and took a bit of a gamble that what "everybody is using" should be ok. /forums/images/graemlins/tongue.gif

Does anyone know why PT uses motor oil (there's nothing wrong with using motor oil)? And then muddies the water with conflicting "Use only 10W30" and "Use only 10W40" documentation and stickers? /forums/images/graemlins/confused.gif

Sedgewood

 

[Edward_DiMaria]

great to hear that the PT is fired back up - great job -ED

 

[smartguyz]

</font><font color="blue" class="small">(
Does anyone know why PT uses motor oil (there's nothing wrong with using motor oil)? And then muddies the water with conflicting "Use only 10W30" and "Use only 10W40" documentation and stickers? /forums/images/graemlins/confused.gif

Sedgewood )</font>

Sedgewood, I spoke to Terry about this some when I purchased my PT425 and found the conflicting information. According to Terry, the 10W-30 is a typo. They use Mobil 10W-40. Terry said that they used to use hydraulic fluid, but after some issues arose where different people from different areas of the country found that they couldn't find the exact hydraulic fluid brand and viscosity PT was using - PT gave this some thought and decided that since motor oil was both perfectly acceptable to use in the PT, and was pretty much universally available across the USA, they would make the switch. He said this has eliminated the issues they were having with not being able to locate the correct hydraulic fluid for all users.

Great to see you back in business! If you have a chance, we'd love action shots! (I also relish any 'improvement' shots, like your junction box shot! Thanks so much!)

Sincerely,

Rob /forums/images/graemlins/grin.gif

 

[marrt]

John,

I've read every page of your web site. I'm afraid Mossroad may have some catching up to do. /forums/images/graemlins/smile.gif. The information you are documenting will be very helpful for all PT owners.

Anyway, one of your links took me to a site (hydraulicsupermarket.com) that has a newsletter on hydraulics. One of the items in the news letter talked about the difference between hydraulic fluid and motor oil. Besides viscosity differences, one other major difference is the ability to separate water out of solution. Apparently, high quality hydraulic fluid has a number of additives that separate water much better that motor oil. However, the water must be drained off to be beneficial. I don't know how this would be done on a PT.

Viscosity stability appears to be the most important factor. High quality hydraulic fluids have much better viscosity stability when hot. This explains why we sense some power reduction on summer days when the hydraulic fluid reaches maximum operating temperature.

I believe PT said they used motor oil because it was commonly available (and cheaper of course).

 

[MossRoad]

<font color="blue"> I'm afraid Mossroad may have some catching up to do. </font>

Yep, it's pretty much a stattic site right now, as I haven't done anything to the unit lately. I'd better get going! /forums/images/graemlins/tongue.gif

 

[dbetts]

Glad to see you've got the machine running again! I've had to keep my wife from reading your posts about PT's limited to absent assistance in the rebuild. We have had a very bad experience with a go kart manufacturer that we purchased an electric kart from who then gave no support when the machine didn't work right. (but that's too long a story to tell here). It's reassuring to know there is such an intelligent and active group out there to help if I do run into trouble after my (hopefully soon) purchase. db

 

[duane]

John,

Any concern about the motor oil left in the circuit and/or implement motors mixing with the new hydraulic oil?. Probably not, just curious to see if you had any info on this.

Duane

 

[Sedgewood]

smartguyz: <font color="green"> They use Mobil 10W-40. Terry said that they used to use hydraulic fluid, but after some issues arose where different people from different areas of the country found that they couldn't find the exact hydraulic fluid brand and viscosity PT was using </font>

Oh, that makes sense. Mixing fluids is not a great idea. Columbia Tractor doesn't stock 10W-40, I guess nobody uses it around here. Even Wal-Mart only has an occassional bottle. 10W-30 and 15W-40 are available. I was going to go with 15W-40 then changed my mind when I realized how far out of viscosity spec it would be for cold starts at 0 degrees F. 10W-30 gets too near the viscosity spec limit on the hot end to suit me - especially since this tractor runs so hot (the engine temp anyway - I haven't checked hydraulic system temps (yet - I just bought a noncontact thermometer)).

Put a much needed culvert in yesterday - sure is nice to be back at work,
Sedgewood

 

[Sedgewood]

MossRoad: <font color="green">Yep, it's pretty much a stattic site right now, as I haven't done anything to the unit lately. I'd better get going! </font>

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!? /forums/images/graemlins/tongue.gif

Sedgewood

 

[Sedgewood]

duane: <font color="red"> Any concern about the motor oil left in the circuit and/or implement motors mixing with the new hydraulic oil?. Probably not, just curious to see if you had any info on this. </font>

I thought about this and decided not to worry about whatever might have been left in the wheel motors and cylinders - everything else has been apart. There was probably not more than 2-3 quarts still in the system which is only a 3% or so.

One thing that has concerned me more as I've read up on hydraulic systems is contamination. The PT 1845 system, and the other models too I assume, are simple in the extreme, with no filtration other that the 10 micron suction filter. There are no screens on the suction lines leaving the tank. Not even a filter on the tank vent. While I had the system empty I thought I might put screens on the suction lines but decided against it since there was no easy way to connect them because of the welded construction PT uses which doesn't provide pipe nipples inside to screw a screen to (see attachment).

I did put on a filtered vent cap though (next post/attachment). A vent desicant also might be a good idea to keep moisture out but I decided not to go that route for now muddy reasons.

Sedgewood