Two speed modification for PT 422/425

[stray]

Started work on the two speed modification so thought a new tread would be appropriate. There is not a lot of room here to install 8 outlets from the tram pump. In fact there is not an over abundance of room anywhere in the engine compartment.

 

[stray]

My plan is to only have 2 outlets from the pump. One for the upper port and another for the lower. Then install a block where there is more room. This is as far as I have come along. Seems like lots of work ahead for this one. I hope not as much as the side mower though!!! Just so you all will know I didn't desert this project here is a pic of the block. It took a few hours just to make it!!

 

[Rip]

You have undertaken a very interesting and challenging project that many will be keen on following closely.

I was more than willing to give up top-end speed for torque on my used PT-1845 and replaced all four wheel motors with the next larger size as the OEM ones were already at the top of the series for torque. This was not cheap but realitively quick, and did not change any of the hydraulics. I did gain the desired low-end torque and have had no problems.

Good luck with this and hope your machine is not out of commission too long while undergoing "elective surgery"!

 

[RegL]

</font><font color="blue" class="small">( You have undertaken a very interesting and challenging project that many will be keen on following closely.

I was more than willing to give up top-end speed for torque on my used PT-1845 and replaced all four wheel motors with the next larger size as the OEM ones were already at the top of the series for torque. This was not cheap but realitively quick, and did not change any of the hydraulics. I did gain the desired low-end torque and have had no problems.

Good luck with this and hope your machine is not out of commission too long while undergoing "elective surgery"! )</font>

Rip, Did replacing the motors make a big difference working on slopes? How much top end speed did you lose? Thanks.

 

[toy]

Stray in an earlier post you said that the flow went from the pump to the right front and then to the left rear and the other side of the tee went to the left front and then to the right rear or something similar to that , but I was looking at the schematic that was in the manual and it appears to me that the flowgoes from the pump to the right front and then to the right rear and the other side of the tee goes to the left front and then to the left rear and then the oil leaves the rear wheel motor and goes back to the upper port the way it is now . unless you have some way of restricting the flow if one wheel is spinning to that wheel, it would seem to me that you would be losing your four wheel drive, oil will go the path of least resistance. I don't know what kind of valve it would take to do this [ maybe something like an anti scald valve in a shower I don't know if they make something of that nature for hydroulics or not but might give you a thought] ,but I hope you are successful at doing it.

 

[stray]

You are right about the way the motors are routed. Good observation! Don’t worry about the path of least resistance so much. I believe the problem of one wheel spinning too much will be taken care of by the size of hose used in the route of the low speed high torque mode. The larger hose will still be used inline for the standed mode. I want to keep this project as simple and cost effective as practical. Too me this is kinda what it is all about. That is the challenge. At least for me.
Another thing I want to look into is maybe having a block built or finding one that will have all the ports like the one I made as well as 2 solenoid valves for the switching of modes. This would keep the project even more compact and a few more less hoses. Either way will work. As I said, cost effectiveness as well as simplicity is what I’m after. I’ll say again this project will take awhile. And then it may take a little longer to better it. Please ever one, Keep the information coming.

 

[MossRoad]

A schematic is a logical drawing arranged to make the least amount of turns and crossovers so that the circuit can be shown in its simplest form. Just because the wheels are shown on the same side in the schematic drawing does not mean they are actually on the tractor that way. It would be best to physically trace the hoses yourself and label your schematic accordingly.

 

[keeney]

From a steering point of view, it would only make sense to series-connect the wheels on the same side of the machine. When they are connected this way, they are forced to spin at the same speed (disregarding inefficiencies and bypass leakage in the motors).

When you turn, the wheels on the outside of the turn need to turn faster than the ones on the inside. This is not possible if the wheels are connected in series across the corners of the machine.

- Rick

 

[toy]

You are right a person when they are going to work on their machine should trace down the hoses to see if the schematic is right and if not make a corrected schematic, and when you take off hoses label them so you won't get them mixed up. As far as a schematic is concerned the routing of the hoses in this case doesn't matter much but where the hoses goes does make a whole lot of difference, in my opinion. I haven't checked the schematic out to see if it is correct or not but the schematic made more sense being plumbed that way keeney, I believe is his name listed one reason another reason, I have a hard time explaning what I am trying to say so bear with me, take a chair put a coaster under one leg now the leg with the coaster under it will be on the floor and the leg diagonally from it will be on the floor and the two other legs will be tipsy. The two other legs if it was your pt wheels would with enough of a difference in level would loose traction but it is unlikely that you would have two wheels on the same side off the ground at the same time, unless you are like me when I was coming out of a hole that I dug for my septic tank , I believe I had it up on one wheel then trying to dance like Mr. Bojangels That wasn't just pt pucker that was down right out scarry. But laterwe all laughed about how big my eyes got. Since power trac makes minning industries machines it would seem to me that they would stick to msha standards with their schematics.

 

[stray]

Another good observation. That makes perfect scene to me.

 

[toolz_not_toyz]

</font><font color="blue" class="small">( From a steering point of view, it would only make sense to series-connect the wheels on the same side of the machine. When they are connected this way, they are forced to spin at the same speed (disregarding inefficiencies and bypass leakage in the motors). )</font>

Your logic is correct. And for a vehicle that is designed to operate on hard surfaces and expected to spend most of its time on hard surfaces that setup makes sense. But for a tractor? Keep in mind that many offroad vehicles are not designed to operate with a locked differential or locked hubs on hard surfaces either for the very same reason you have just pointed out.

 

[stray]

I hope this explains the routing and positioning of valves and hoses. This should work like it's drawn but I am hoping to refine it further. The blue and purple lines will only be in service in the high torque low speed mode. I was thinking of using a couple of $66 log splitter valves because of cost but they are large and operate manually. Can someone please put me on to some good cheep solenoid valves?

 

[J_J]

Stray, Check out Ebay

Item number: 7564005851

Electric solenoid valve.

 

[stray]

It looks like two of those will work. are two available here?

 

[J_J]

Stray, There are probably more than one, just email the guy and ask. Make sure you get the 12v ones. Or just type in hydraulic valve in the search window on Ebay. I got four sets of these valves for my backhoe project, but haven't decided whether to use manual valves, or the solenoid. Solenoid valves are instant on, while manual valve can be slowly activated

 

[stray]

Thanks abunch JJ. Will do.

 

[Rip]

RegL, Sorry not to have gotten back sooner. I did the swap as soon as I got the used machine back in early '04 so I can not say "how much" difference it made, but by the numbers I cut max speed by about 1/2 and got about 55% more torque.

Max speed is probably in the 8 to 9 MPH range and I use all of the available torque on the steeper (30 plus degree) slopes (read rocky Rocky Mountains) on a regular basis. It meets my needs and I am pretty sure it would not have in original configuration. Could I use more speed or torque? Sure... more..more...!!

 

[toolz_not_toyz]

Check out this place for solenoid valves:

Surplus Center

 

[stray]

To set up you Pt like this schematic one will need 8 new hoses and be sure that the tank port is pressure rated and see that the valves are rated with enough flow.

 

[stray]

Route the test block or a block with the solenoid valves like this. This would be the high torque low speed mode.