Upgrading Wheel Motors

[marrt]

I'm about to upgrade my White 14.2ci wheel motors with White 21.2ci (or bigger) motors. Any way to easily figure out the speed changes? The current motors are very fast. I'd guess 10 MPH. The tractor is faster than my 1845 and I have larger than normal tires on that tractor. I'd rather have more torque due to some hills on my property. Beside, with no suspension, I don't like going over 6 MPH anyway.

I'll get a local welder to lengthen the wheel motor boxes and take plenty of pictures.

 

[woodlandfarms]

Martt. what tractor (s) do you own? I thought you were an 1845 and were looking at a 425...

 

[marrt]

I still have an 1845 but bought a 425 from a member here...guess I should have mentioned that.

 

[woodlandfarms]

Sidetracking but you said 1850? Typo? Or do you have 3 and an addiction problem and won't fess up here?

 

[marrt]

LOL. Yes, I do have an addiction...to sake. I had a bit too much sake before writing that post. Fixed now.

Actually, I own two properties. So I "need" two tractors, right?

 

[woodlandfarms]

Rationalize that tractor addiction however you want. Blame the sake. You could trailer them ;-)

 

[MossRoad]

Power Tracs, sake, trailers, typos all in one thread.... Gosh I love TBN!!!! :laughing:

 

[KentT]

Any way to easily figure out the speed changes?

Having been there, done that, the short answer is "NO" to the "easy" part. With a variable displacement pump, the inherent loss of efficiency in hydraulic systems, etc. -- all you can end up with it theoretical numbers.

However, the White catalogs list the specs for each size motor in a series separately, with a table for different flow rates (volume) and PSI. So, you can compare the specs, side by side, at different pressure and flow ratings. I built a spreadsheet that compared the numbers for the specific size motors I was looking at, using the data from those tables. Disregard any numbers above 2500 PSI (max limit for these PT designs, AFAIK), and about 12 GPM (though I'm not sure what the theoretical max for this tram pump is). Then you could use tire circumference to calculate the theoretical MPH. Since we're dealing with theoretical numbers, it is essentially a direct relationship. Twice the displacement yields twice the torque, and 1/2 the RPM (speed).

From practical experience in having done this twice now, and seat-of-the-pants observations, the CE-series 22.8ci would be a good choice to meet your stated requirements, if you plan on staying with the stock 23x10.50x12 tires. I ran CharLynn S-series motors about that size for a while -- though I don't recommend them for this conversion because the taper on their tapered shafts does NOT match the taper on the PT hubs. I couldn't keep the hubs tight, and wallowed them out -- they're very soft metal.

I'm now running White RE-series 28.3ci BUT I also went to 26x12x12 tires. Even with the taller tires it is SLOW (slower than your stated goal) but has more torque that the 425's design limits -- I've bent QA hitches, lift arms, etc. I have to be careful not to break things, and still find the weak points in the PT's design. So far, I love the torque on my steep hillsides, though, and have found the speed "fast enough" even if I am mowing at full treadle on the few flat spots I have.

As I said, I'd recommend the 22.8 size -- then you could go to taller tires if you wanted more speed...

BTW, my only complaint with the RE series wheel motors is that I have now blown the seals on each of the rear wheel motors. The first one went at about 250-300 hours of abuse, and simply ordered another wheel motor from Surplus Center to have a spare. The second one went yesterday, and I just ordered two seal kits. I'll have one put in the wheel motor I replace initially, then have to second one installed in the motor that just blew, so I'll have a ready spare next time...Surplus Center no longer has the REs in this size in stock (sold out, I guess) but at $179 each (with hubs) or $169 each (without hubs) they were a bargain while they lasted....

 

[marrt]

Thanks Kent,

Let's go through a few numbers. The Bondioli and Pavesi NT 10 pump comes in two flavors, 14 cu cm and 19 cu cm. So, at 3600 RPM, that's ether 13.31 GPM or 18.07 GPM. The rated pressure of the pump is 175 bar, or about 2500 PSI. Using rule of thumb calculators, 13.31 GPM at 2500 PSI would require 23.29 HP. The same calculation for 18.07 GPM would require 31.62 HP. Therefore, if I were guess, I'd bet the PT-425 uses the 14 cu cm pump and the PT-1430 uses the 19 cu cm pump (assuming it uses the B&P NT 10).

Now that we have some numbers, let's look at the White brochure. The "230" motor can take up to 3000 PSI continuous. However, just driving around with no load wouldn't require much pressure. Since White rates the RPM by pressure and GPM, we have to pick something. For conversation purposes, I selected an RPM of 60, assuming 15 GPM. Doing a little math, this results in a 4.1 MPH speed. Far slower than the 8 MPH advertised or my seat of the pants estimate. Doing the same math for your tractor, I get 2.3 MPH using a 26" tire. My guess is these number are off by 50%. Maybe something to do with the way they are plumbed in series. If so, my tractor speed would indeed be about 8 MPH and your current speed would be about 4.6 MPH, or a "speed walking" pace.

Tom

 

[buickanddeere]

Tuff Torq | KWM-18

 

[KentT]

I think you're correct with the 14cc size assumption on the tram pump. I agree that theoretically, it could pump 13.31 GPM, requiring 23.29HP. However, that 25HP engine (at 3600 RPM) is also spinning the pump for the lift arms/tilt/steering circuit at all times, in addition to the PTO pump. Even if there is no added load on either of those hydraulic circuits (not steering, lift arms at rest, and the PTO not engaged -- those pumps are still pumping oil, even if that oil is simply returning to the tank. So, I don't think you EVER have 23.29HP going to the tram pump. How much less depends on how the other two circuits are being used....

Now, let's look at how pressure/flow relates to the tram circuits themselves. There are TWO circuits, with TWO motors in each one. So, that volume is split in half, with half available to each circuit. Pressure is the same across both circuits, but the front wheelmotor will "consume" half that pressure while the rear wheelmotor will "consume" the other half. In a "no added load" situation, with the PT up on jackstands and only turning the wheels, you could likely get somewhere around 12GPM, perhaps a bit more, flowing through the tram circuits (why I suggested disregarding anything above 12 GPM in my first post) with the remainder of the engine power going to the other two pumps.

At 12GPM, according to the specs, a 230 wheel motor would turns 192 RPM, at 1000 PSI. But, that doesn't happen -- half the flow (6 GPM) is going to one wheel motor circuit, half (6 GPM) to the other. According to the chart, at 6 GPM the wheelmotors would turn 96 RPM at either 250 or 500 PSI pressure. It likely would take somewhere close to 500 PSI to get the PT moving if not on jackstands (automatic hydraulic brakes often require about 400 PSI to release, as an a example, and allow the motors to start turning). So, at 12GPM from the pump (6 GPM to each wheel motor) you'd be turning 96 RPM -- or about 6.3 MPH with 23" tall tires, according to my conversions.

You may actually be able to get more than 12GPM flowing the tram pump, closer to 14 (the next table value) in no-load/no-added-load conditions, before you run out of engine HP, but since the table does not show 7 GPM (half of 14), it is hard to make any higher conversion or calculations...

Bottom line -- I think your interpretations are pretty solid -- but you haven't considered that the GPM must be evenly split across the two tram circuits... and there's no need to add any "fudge factor adjustments"... I think the numbers are pretty accurate, just a bit difficult to interpret.

 

[marrt]

Kent,

Thank you for the detailed response. I wrote up a long reply...but it disappeared before I could post.

In my analysis above, I made two errors. I misread the chart and originally used liters per minute instead of GPM (oops). And I didn't consider the flow split between the two circuits. After those corrections, I get about 7.7 MPH for the standard 230 motor and 4.5 MPH for the 375 motor. So, the 375 looks like a decent compromise, as you suggest.

Now, on to the motor mounts. I can fabricate some type of spacer, or have a welder lengthen the boxes. The 375 motor is only .57" longer than the 230. But I'm a little worried about using a spacer. I'm afraid it could get lose and "wobble" over time, causing problems.

Tom

 

[KentT]

Tom,

I'd vote for welding in an extension to the wheel motor boxes. Cut the current ones with a plasma cutter down the center, weld in the needed estension, then weld on a wider plate on each side to "scab over" and reinforce the previous work. That way, the modification would likely be stronger than what you started with -- you may need that added strength to handle the added torque. I bought 1430 wheel motor boxes from Tazewell for my last upgrade, but they were almost as expensive as the new wheel motors -- danged close to it, as I recall. When I put the 22.7ci CharLynn S series on it earier, I simply cut openings into the tub, an recessed the into he opening. But, my older 425 originally had the welded on wheelmotor boxes, not the later-style bolt-on ones like yours...

You'll be surprised what the added torque feels like, but use it gently until you get used to it. I've bent and broken things that I would never have imagined, including ripping out the front of the tub where the opening is cut for the hydraulic control valves and lines... I must have developed a stress crack at the corner of the opening, which is near where the right lift arm mounts. I ripped it farther, broke the weld at the right side of the tub, and curled it up at least an inch and a half. That made for an "interesting" repair. I do believe I could pull a 3-point plow with it now, if I had the 3-point hitch.

 

[MossRoad]

I've bent and broken things that I would never have imagined, including ripping out the front of the tub where the opening is cut for the hydraulic control valves and lines...

Kind of like this???
https://screen.yahoo.com/weekend-drug-olympics-000000571.html

 

[KentT]

Kind of like this???
https://screen.yahoo.com/weekend-drug-olympics-000000571.html

:laughing:

Yep, pretty much. I'm trying to learn to use the PT's wheels to only hold it in place when using the mini-hoe, especially. It's very tempting to use reverse to better fill the bucket, rake more stuff out of the ditch, etc.

 

[MossRoad]

:laughing: The big Russian has to be dissapointed... :laughing: