marrt
Platinum Member
This may have been discussed b/f but here goes.... I know PT does not recommend filled tires for the 400 series. But what about the 1400 and larger series?
Tires Filled Tires
- Thread starter marrt
- Start date
- Views: 2197
davesisk
Platinum Member
Marrt:
I don't know, but (just FYI)...both of my rear tires are filled, and interestingly enough, I just replaced one rear wheel motor and the other rear wheel motor has some minor seepage (can't detect where it's coming from, but the shell gets a little greasy after a few hours of use). Both front wheel motors are dry as a bone all the time, and those wheels are not filled. I don't know if this is coincidence or not, but I think PT does say that filling the tires puts addition wear on the wheel motors.
Just out of curiosity, does anyone know WHY filling the tires puts additional wear on the wheel motors? I can't see the polar moment of inertia of the wheel (resistance to a change in turning speed) being increased THAT much by adding a liquid to it???? Or maybe it is?
Dave
I don't know, but (just FYI)...both of my rear tires are filled, and interestingly enough, I just replaced one rear wheel motor and the other rear wheel motor has some minor seepage (can't detect where it's coming from, but the shell gets a little greasy after a few hours of use). Both front wheel motors are dry as a bone all the time, and those wheels are not filled. I don't know if this is coincidence or not, but I think PT does say that filling the tires puts addition wear on the wheel motors.
Just out of curiosity, does anyone know WHY filling the tires puts additional wear on the wheel motors? I can't see the polar moment of inertia of the wheel (resistance to a change in turning speed) being increased THAT much by adding a liquid to it???? Or maybe it is?
Dave
Charlie_Iliff
Veteran Member
- Joined
- Jun 13, 2001
- Messages
- 1,890
- Location
- Arnold, MD
- Tractor
- Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II
Marrt & Dave:
The volume of PT tires is substantially smaller than conventional tractors, so the weight actually added isn't as significant. If weight is needed, however, that's one way to do it.
I think someone doing real calculations would have a hard time showing any significant increase in any loads on the axle and thus the wheel motor. Picking something up with a loader vastly increases the weight on the fronts, and then driving over anything rougher than a tabletop imposes shock loading spikes way above the weight being carried. Fluid in the tires doesn't increase static axle load at all, although it would increase the inertia of the wheel-tire combination. That will affect loading at high speeds over bumps, but because it will change (slow) any resonant component, it may be hard to say that it doesn't actually reduce the shock loading when you hit a bump. As Dave noted, the polar moment is increased, and gyroscopic effects are, as well, but I'd bet they are much smaller than the operating jolts we apply to the machines all the time. Without the benefit of testing, my gut feel is that fluid in the tires would be less hard on the axles than equivalent dead weight on the frame.
Marrt - are you going to be chief tester? /forums/images/graemlins/grin.gif
The volume of PT tires is substantially smaller than conventional tractors, so the weight actually added isn't as significant. If weight is needed, however, that's one way to do it.
I think someone doing real calculations would have a hard time showing any significant increase in any loads on the axle and thus the wheel motor. Picking something up with a loader vastly increases the weight on the fronts, and then driving over anything rougher than a tabletop imposes shock loading spikes way above the weight being carried. Fluid in the tires doesn't increase static axle load at all, although it would increase the inertia of the wheel-tire combination. That will affect loading at high speeds over bumps, but because it will change (slow) any resonant component, it may be hard to say that it doesn't actually reduce the shock loading when you hit a bump. As Dave noted, the polar moment is increased, and gyroscopic effects are, as well, but I'd bet they are much smaller than the operating jolts we apply to the machines all the time. Without the benefit of testing, my gut feel is that fluid in the tires would be less hard on the axles than equivalent dead weight on the frame.
Marrt - are you going to be chief tester? /forums/images/graemlins/grin.gif
Schultz
Gold Member
I think I may take the opposite stand. Providing the wheel motor bearings can handle the extra load, then I would say the weight on the frame would be preferred. As you mentioned Charlie when you load the bucket, you're adding a much higher load then the back tires normally see, so the bearings are likely capible of more loading.
My preference comes because the loading of the tires may add as much as 40lbs to each tire (5gal of fluid). I also agree with you this isn't much to worry about. However, this does create a heaver flywheel, so the wheel motor has to overcome this energy every time it changes speed, which might put more stress on the motor seals.
My preference comes because the loading of the tires may add as much as 40lbs to each tire (5gal of fluid). I also agree with you this isn't much to worry about. However, this does create a heaver flywheel, so the wheel motor has to overcome this energy every time it changes speed, which might put more stress on the motor seals.
Charlie_Iliff
Veteran Member
- Joined
- Jun 13, 2001
- Messages
- 1,890
- Location
- Arnold, MD
- Tractor
- Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II
<font color="red"> this does create a heaver flywheel, so the wheel motor has to overcome this energy every time it changes speed, which might put more stress on the motor seals.
</font>
That's certainly true, but I wonder whether it is a significant load compared to the inertia of the whole machine, which the motors are handling all the time. If you add 160 lb. of dead weight to the frame, the wheel motors have to accelerate and slow that mass. If it's in the tires, they have to do the same, just rotational instead of linear. And there'd be some lag where the fluid and tire casing wouldn't move or accelerate at the same rates.
I guess my conclusion at this point is that I certainly don't know the answer. I just have a gut feel that the difference wouldn't be great.
</font>
That's certainly true, but I wonder whether it is a significant load compared to the inertia of the whole machine, which the motors are handling all the time. If you add 160 lb. of dead weight to the frame, the wheel motors have to accelerate and slow that mass. If it's in the tires, they have to do the same, just rotational instead of linear. And there'd be some lag where the fluid and tire casing wouldn't move or accelerate at the same rates.
I guess my conclusion at this point is that I certainly don't know the answer. I just have a gut feel that the difference wouldn't be great.
Schultz
Gold Member
After thinking about it more it probably doesn't matter all that much where the weight is. I agree the difference of workload on a wheel motor of a filled tire vs. a non-filled tire is very little compared to the load of the tractor itself. So, with that in mind any additional weight in a tire would have no additional effect on the wheel motor bearings. As far as stress goes it may be better to have it on the wheel. However, you can shift the CG more rearward with the same weight by hanging it off the tail of the tractor. Take your pick...
RonL
Banned
- Joined
- Dec 22, 2001
- Messages
- 432
- Location
- Worcester, Massachusetts
- Tractor
- Caterpillar 416C IT, Caterpillar D3G, previously owned a Ford 1910
I don't think that fluid in a tire would have a significant flywheel effect. Consider 40 pounds of fluid in a tire and 40 pounds of weight bolted to the tire. Stopping the spinning tire with the weight bolted on would involve having to stop the spinning weight also. Stopping the spinning tire with fluid would involve stopping the spinning tire but the fluid could continue to spin. Minus the friction against the interior carcass of the tire, of course. However, is stopping the forward momentum of both the same? If a tree falls in the forest..................
RonL
RonL
OP
marrt
Platinum Member
<font color="red">Marrt - are you going to be chief tester?</font>
I'm going to look at a 1430 and the owner said he filled the tires. I recall some discussion on this topic before and the conclusion, for the 425, was that Power-Trac didn't recommend it. The reason this would be helpful for the 425 is to take advantage of the hydraulic lift capacity to get more lift without risk of the PTP. One reason it may not be recommended is that it may stress the center articulated joint, as opposed to the wheel motors, when carrying a load. However, as you've noted, I really can't believe the difference is significant.
Maybe the guy filled the tires because he bought those whippy turf tires and was simply looking for more traction. /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif I'll find out.
I'm going to look at a 1430 and the owner said he filled the tires. I recall some discussion on this topic before and the conclusion, for the 425, was that Power-Trac didn't recommend it. The reason this would be helpful for the 425 is to take advantage of the hydraulic lift capacity to get more lift without risk of the PTP. One reason it may not be recommended is that it may stress the center articulated joint, as opposed to the wheel motors, when carrying a load. However, as you've noted, I really can't believe the difference is significant.
Maybe the guy filled the tires because he bought those whippy turf tires and was simply looking for more traction. /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif I'll find out.
Bob999
Platinum Member
Your point about additional weight adding loads to the center joint reminds me that when I visited PT I enquired about a then current TBN post about a broken heim joint on an 425. I was told that 1400 and 1800 series uses a different "design" (I think the reference was to materials) and that there had been no problems with broken joint components on these models. I also learned that the problem on the 425 was most likely a welding issue.
FOURTEEN
Veteran Member
- Joined
- Jan 17, 2004
- Messages
- 1,042
- Location
- Efland - Triangle of North Carolina.
- Tractor
- 2004 Power Trac PT-425
"driving over anything rougher than a tabletop imposes shock loading spikes way above the weight being carried. Fluid in the tires doesn't increase static axle load at all"
You may have the answer here, but not realize it! The tires are not static!
It's not the weight of the filled tire that stresses the motors, it is more likely the shock loading. Tires are filled with air for a reason - to cushion and absorb shock. Filled tires are, by definition, mostly filled with incompressible liquid, so every shock is transmitted directly to the chassis. (Lay a wheel and tire on the garage floor. Hit the tire with a baseball bat as hard as you can. Not much happens. Now, hit the solid wheel the same way. You will be lucky if the bat doesn't break in your hands!!) Even railroad cars which ride on smooth steel have coil springs to cushion the ride. The air filled tires are the only suspension the poor PT has!!!
Why not just use the PT the way it was designed?? Is it worth damaging or breaking it just to lift a little extra!??!
You may have the answer here, but not realize it! The tires are not static!
It's not the weight of the filled tire that stresses the motors, it is more likely the shock loading. Tires are filled with air for a reason - to cushion and absorb shock. Filled tires are, by definition, mostly filled with incompressible liquid, so every shock is transmitted directly to the chassis. (Lay a wheel and tire on the garage floor. Hit the tire with a baseball bat as hard as you can. Not much happens. Now, hit the solid wheel the same way. You will be lucky if the bat doesn't break in your hands!!) Even railroad cars which ride on smooth steel have coil springs to cushion the ride. The air filled tires are the only suspension the poor PT has!!!
Why not just use the PT the way it was designed?? Is it worth damaging or breaking it just to lift a little extra!??!
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,973
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
have you considered the fact that the rear tires, since they are filled, do not flex very much, where as the front tires that are not filled do flex and therefore the rolling radius of the tire changes. on a four wheel drive machine, the diameter of all four tires must be the same to function effectively. i would therefore jack up the rear tires and measure the center of the tire, and ensure that all the other tires are the same. you may have to run some tires at a different pressure to get equal diameter on all tires
same size tires from different manufactures may have a different rolling radius, and depending on air pressure may cause your back tires to working harder, and cause more stress.
j.j.
same size tires from different manufactures may have a different rolling radius, and depending on air pressure may cause your back tires to working harder, and cause more stress.
j.j.
FOURTEEN
Veteran Member
- Joined
- Jan 17, 2004
- Messages
- 1,042
- Location
- Efland - Triangle of North Carolina.
- Tractor
- 2004 Power Trac PT-425
</font><font color="blue" class="small">( The rolling radius of the tire changes. On a four wheel drive machine, the diameter of all four tires must be the same to function effectively.
j.j. )</font>
The rolling radius of all tires changes as they move under various load and road conditions.
The horizontal diameter and circumference do not change. On geared 4WD vehicles the tires must be the same size (circumference). On a 4WD tractor with 2 size tires the internal gear ratios must be designed to allow all 4 tires to turn at the same speed.
The PT wheels are not geared together. Each is powered by a fully independent motor which is not influenced by the other motors on the PT. Each only "sees" more or less hydraulic pressure, and does it's work regardless of what may be happening to the other 3. (A 4WD SUV is like a boat with 4 oarsmen chained together - they must be the same size and work in unison. The PT is like a boat with 4 outboard motors - each one helps propel the boat, but is independent of the others.)
j.j. )</font>
The rolling radius of all tires changes as they move under various load and road conditions.
The horizontal diameter and circumference do not change. On geared 4WD vehicles the tires must be the same size (circumference). On a 4WD tractor with 2 size tires the internal gear ratios must be designed to allow all 4 tires to turn at the same speed.
The PT wheels are not geared together. Each is powered by a fully independent motor which is not influenced by the other motors on the PT. Each only "sees" more or less hydraulic pressure, and does it's work regardless of what may be happening to the other 3. (A 4WD SUV is like a boat with 4 oarsmen chained together - they must be the same size and work in unison. The PT is like a boat with 4 outboard motors - each one helps propel the boat, but is independent of the others.)
Charlie_Iliff
Veteran Member
- Joined
- Jun 13, 2001
- Messages
- 1,890
- Location
- Arnold, MD
- Tractor
- Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II
<font color="red"> Filled tires are, by definition, mostly filled with incompressible liquid, so every shock is transmitted directly to the chassis. </font>
That's true, I suppose if you fill the tire completely. On ag tractors, we've always left a substantial air pocket, and some will claim that the best stability is to limit the fill to the axle line. For comfort and maximum traction on the turfs on my PT, I keep them very soft. 10-12 psi. I have considered going to 8 ply bar tires to avoid punctures, but the harshness and high spike loads are a bad side effect even without fluid.
That's true, I suppose if you fill the tire completely. On ag tractors, we've always left a substantial air pocket, and some will claim that the best stability is to limit the fill to the axle line. For comfort and maximum traction on the turfs on my PT, I keep them very soft. 10-12 psi. I have considered going to 8 ply bar tires to avoid punctures, but the harshness and high spike loads are a bad side effect even without fluid.
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,973
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
it's ok to disagree, so here goes. yes, all the motors will try to run at the same rpm, given that all things are equal. now, let out half the air in one tire and notice the effect. for instance, i have a dixie chopper o turn lawn mower driven by hyd motors. if the tires are different diameters caused by leaking air, i have to compensate by adding more torque to the side with the low tire. i don't know if that explains my point. but i tried.
j.j.
j.j.
FOURTEEN
Veteran Member
- Joined
- Jan 17, 2004
- Messages
- 1,042
- Location
- Efland - Triangle of North Carolina.
- Tractor
- 2004 Power Trac PT-425
Considering all these bad side effects, and already having full-time all-wheel drive, how much of an advantage are filled tires!??!
However, the judicious use of weigh can bring startling results. My 1976 14hp Power King 2WD tractor came from the factory weighing 850# with 8.00x16 AG rear tires. It often spun the tires when 48" mowing on lawn slopes or trying to push snow with the 48" dozer blade.
Completely filling the tires would have added 250#, but the tractor would ride like on concrete wheels. No thanks!
Instead I added: 2 steel wheel weighs of 135# each, a steel chassis weight below the frame of 130#, a steel 3 point hitch weigh of 70#, and a 50# steel scale weigh over the axle near the 1000AH car battery! The tractor now weighs 1400#, a 65% increase, with most of it centered (H&V) at the rear axle!!!
After studding the AGs with #6 hex head crown screws and dropping tire pressure to 7#, the Power King is **** near unstoppable for a 2WD! Wet grass, mud, ice, snow, slippery logs, and steep slopes (forward 25 degrees on dry loose clay)can be laughed at! Plowing into a snow bank at the end of our hard-packed snow covered parking lot in high gear, the Power King would actually slip it's clutch rather than spin a tire! Comfortable ride with a big footprint that is gentle on dry clay grass is another plus.
If my new PT-425 runs out of traction, or wants to lift it's tail, I will carefully consider all my other options before filling the tires.
PS: Based upon the new Power Trac Product Catalogue, "PT-425" and "Power Trac" are correct - not "PT425" and "Power-Trac". But then again, "catalogue" is used for the more common word "catalog"! Strange, but true!!
However, the judicious use of weigh can bring startling results. My 1976 14hp Power King 2WD tractor came from the factory weighing 850# with 8.00x16 AG rear tires. It often spun the tires when 48" mowing on lawn slopes or trying to push snow with the 48" dozer blade.
Completely filling the tires would have added 250#, but the tractor would ride like on concrete wheels. No thanks!
Instead I added: 2 steel wheel weighs of 135# each, a steel chassis weight below the frame of 130#, a steel 3 point hitch weigh of 70#, and a 50# steel scale weigh over the axle near the 1000AH car battery! The tractor now weighs 1400#, a 65% increase, with most of it centered (H&V) at the rear axle!!!
After studding the AGs with #6 hex head crown screws and dropping tire pressure to 7#, the Power King is **** near unstoppable for a 2WD! Wet grass, mud, ice, snow, slippery logs, and steep slopes (forward 25 degrees on dry loose clay)can be laughed at! Plowing into a snow bank at the end of our hard-packed snow covered parking lot in high gear, the Power King would actually slip it's clutch rather than spin a tire! Comfortable ride with a big footprint that is gentle on dry clay grass is another plus.
If my new PT-425 runs out of traction, or wants to lift it's tail, I will carefully consider all my other options before filling the tires.
PS: Based upon the new Power Trac Product Catalogue, "PT-425" and "Power Trac" are correct - not "PT425" and "Power-Trac". But then again, "catalogue" is used for the more common word "catalog"! Strange, but true!!
Attachments
Charlie_Iliff
Veteran Member
- Joined
- Jun 13, 2001
- Messages
- 1,890
- Location
- Arnold, MD
- Tractor
- Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II
<font color="red"> Considering all these bad side effects, and already having full-time all-wheel drive, how much of an advantage are filled tires!??! </font>
I don't think any of us can answer that question. Davesisk has fluid in the rears on his, but he's the only one I know who has it. I don't know that he's run without it to compare. Dave? I've had times with the 1845 where I needed more traction, but I'm on turfs with no added weight on the tractor. Most PT users have found pretty impressive traction without any modifications.
I don't think any of us can answer that question. Davesisk has fluid in the rears on his, but he's the only one I know who has it. I don't know that he's run without it to compare. Dave? I've had times with the 1845 where I needed more traction, but I'm on turfs with no added weight on the tractor. Most PT users have found pretty impressive traction without any modifications.
FOURTEEN
Veteran Member
- Joined
- Jan 17, 2004
- Messages
- 1,042
- Location
- Efland - Triangle of North Carolina.
- Tractor
- 2004 Power Trac PT-425
</font><font color="blue" class="small">( <font color="red"> Most PT users have found pretty impressive traction without any modifications.
)</font>
My point exactly! It may be foolish to always wear suspenders just because someday your belt may break!
If someone often gets themself stuck, or lifts the rear wheels, if may be just "operator error"!
/forums/images/graemlins/blush.gif
"Doctor! Doctor! It hurts when I do this!"
"Then don't do that!!" /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
.
)</font>
My point exactly! It may be foolish to always wear suspenders just because someday your belt may break!
If someone often gets themself stuck, or lifts the rear wheels, if may be just "operator error"!
/forums/images/graemlins/blush.gif
"Doctor! Doctor! It hurts when I do this!"
"Then don't do that!!" /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
.
