Tire Overtreads--A Needed Invention
- Thread starter glennmac
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head on down to ya friendly NH man......get some of that wide belt stuff out of an old or new round baler (apparently they use wide belts now?.....
cut to length..........vulcanise with a big over lap together in a circle.........
jack the tractor up.......deflate the tire..........slip the belt over........inflate.......
strap with packing tape, or dog collars to the rim to stop them sliding side ways
the end
pudding
ps. this pic showed up at ytmag a while back............worth posting again
OI you! Get back to work
cut to length..........vulcanise with a big over lap together in a circle.........
jack the tractor up.......deflate the tire..........slip the belt over........inflate.......
strap with packing tape, or dog collars to the rim to stop them sliding side ways
the end
pudding
ps. this pic showed up at ytmag a while back............worth posting again
OI you! Get back to work
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jdkid
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Hi ya
well there ya go ,can be done i do notic all are 2 wheel drive tho but with tracks 4wd kinda comes useless
gives people a few ideas if doing a heap of snow work tracks for winter back to tires for summer best of both worlds
thanks for the pics pudding i'll spring ya a beer or two once i get up your way
catch ya
JD Kid
well there ya go ,can be done i do notic all are 2 wheel drive tho but with tracks 4wd kinda comes useless
gives people a few ideas if doing a heap of snow work tracks for winter back to tires for summer best of both worlds
thanks for the pics pudding i'll spring ya a beer or two once i get up your way
catch ya
JD Kid
hayden
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Hi Patrick,
I just read this more closely and what you are saying I think is completely correct, but is not the point I think we are debating. Maybe this is why we still don't see eye to eye.
My original comment to Glenn, restated hopefully more clearly, is: Take a 4x4 tractor with properly geared front and rear wheels for operating on flat ground just like many of us have today. The front and rear wheels are predominantly different sized, but things work without violance because the drive gearing is matched to the wheel size difference. This is your pully analogy and I think we agree on the need for proper gearing and we agree that the front and rear wheels will turn at different rotational speeds just like the pullies.
The point I was trying to make is that if you then wrap a track around those same drive wheels with that same gearing it will work just fine without slippage or skidding. Further more, it doesn't matter if the track is 1"" thick or 1' foot think, the tractor drive gearing and drive wheel sizes will still be correct and will propel the track without slippage.
Hopefully we are debating the same point. I've seen some lively conversations where in the end you discover the people are debating two different issues or points.
I just read this more closely and what you are saying I think is completely correct, but is not the point I think we are debating. Maybe this is why we still don't see eye to eye.
My original comment to Glenn, restated hopefully more clearly, is: Take a 4x4 tractor with properly geared front and rear wheels for operating on flat ground just like many of us have today. The front and rear wheels are predominantly different sized, but things work without violance because the drive gearing is matched to the wheel size difference. This is your pully analogy and I think we agree on the need for proper gearing and we agree that the front and rear wheels will turn at different rotational speeds just like the pullies.
The point I was trying to make is that if you then wrap a track around those same drive wheels with that same gearing it will work just fine without slippage or skidding. Further more, it doesn't matter if the track is 1"" thick or 1' foot think, the tractor drive gearing and drive wheel sizes will still be correct and will propel the track without slippage.
Hopefully we are debating the same point. I've seen some lively conversations where in the end you discover the people are debating two different issues or points.
StoneHeartFarm
Veteran Member
Hayden,
My gut is voting with you. Fuzzy math says it doesn't matter what the thickness of the belt is. The tires would be running on the inside of the belt, not on the outside. The effective diameters of the pulleys would be changed, which would result in different speeds of rotation (RPM), however, the distance the belt travels along its inside surface would be the same, irregardless of the belt's thickness. (It's very important we get this figured out, or every automobile ever built may be in danger of blowing its belts.) Assuming your track has an inside diameter of 10', and an outside diameter of 14' due to the added thickness. (The inside of a pipe is not the same diameter as the outside). So, for every rotation of the inside, the tractor will think it has gone 10'. But, actually, it will have gone 14'. No matter what, the outside of that track will go around once for every one time the inside goes around.
The third wheel you are seeing in the pictures is an idler, which basically helps to take the pressure off the top of the drive tires and reduces tire scrubbing. It also keeps the distance between centers shorter to prevent the track from jumping. The better you can hold the track the less likely it is to jump off.
Now for a question. I understood that on 4x4 trucks (at least), the front wheels are designed to turn at a slightly slower rate than the rears. This is to ensure you can maintain steering. Since the rear wheels are always pushing the fronts, there is always a slight drag, which allows the front tires to steer. This explains two things. A. Why 4x4's are lousy on ice (I've seen a lot of em with their rears trying to pass their fronts.) B. Why the maunfacturers always add a warning label saying something like :"Do not operate on dry pavement."
Does anyone know if this rotational difference also applies to 4x4 tractors?
SHF
PS: Patrick,
42? 42? I believe the correct response is: "So long, and thanks for all the fish" /w3tcompact/icons/wink.gif
My gut is voting with you. Fuzzy math says it doesn't matter what the thickness of the belt is. The tires would be running on the inside of the belt, not on the outside. The effective diameters of the pulleys would be changed, which would result in different speeds of rotation (RPM), however, the distance the belt travels along its inside surface would be the same, irregardless of the belt's thickness. (It's very important we get this figured out, or every automobile ever built may be in danger of blowing its belts.) Assuming your track has an inside diameter of 10', and an outside diameter of 14' due to the added thickness. (The inside of a pipe is not the same diameter as the outside). So, for every rotation of the inside, the tractor will think it has gone 10'. But, actually, it will have gone 14'. No matter what, the outside of that track will go around once for every one time the inside goes around.
The third wheel you are seeing in the pictures is an idler, which basically helps to take the pressure off the top of the drive tires and reduces tire scrubbing. It also keeps the distance between centers shorter to prevent the track from jumping. The better you can hold the track the less likely it is to jump off.
Now for a question. I understood that on 4x4 trucks (at least), the front wheels are designed to turn at a slightly slower rate than the rears. This is to ensure you can maintain steering. Since the rear wheels are always pushing the fronts, there is always a slight drag, which allows the front tires to steer. This explains two things. A. Why 4x4's are lousy on ice (I've seen a lot of em with their rears trying to pass their fronts.) B. Why the maunfacturers always add a warning label saying something like :"Do not operate on dry pavement."
Does anyone know if this rotational difference also applies to 4x4 tractors?
SHF
PS: Patrick,
42? 42? I believe the correct response is: "So long, and thanks for all the fish" /w3tcompact/icons/wink.gif
patrickg
Veteran Member
Haydn, I'm sorry to be the cause of any "thinking pains" or frustration, well almost.
You said: In fact, spacing the wheels farther apart in a track device will slow it down even more for the
same 2.27 rotations of the drive wheels.
I'm sorry but I'm losing it... I guess I'm just not smart enough to have your view explained to me so that I "believe".
I just can't imagine how the "wheelbase" would slow ground speed. D O E S N O T C O M P U T E for me.
I keep thinking that it the track doesnt slip, compress, or stretch a huge amount, the linear feet of track passing by a drive wheel is a linear function of the circumference of the drive wheel times the rotational rate of the drive wheel (RPM). I believe this is invariant with changing track lengths. How does the wheel know how long the track is? Sure the time required to rotate the track one time changes linearly in direct proportion to the change in track length but the length per unit time of the track (sans slippage, compression, or stretching) that goes by is invariant.
If this goes on much longer I may recommend binding arbitration or I may have to sue for peace separately with the various litigants (combatants). Of course these options would be like voting on the laws of physics and the various universal constants. I'm reminded of the school board member who wanted pi made three so kids wouldn't have such a hard time with it in math.
Ahh, my all time hero Galileo Galilei when his friends persuaded him to go before the pope to recant his heretical notions. He had to "take it back" to have his life spared B U T was heard to mutter under his breath as he withdrew "respectfully" from the pope's prescence, "It moves."
Patrick
P.S. Could you give me just a little more detail on the "goes slower if the tracks are longer" thing.
You said: In fact, spacing the wheels farther apart in a track device will slow it down even more for the
same 2.27 rotations of the drive wheels.
I'm sorry but I'm losing it... I guess I'm just not smart enough to have your view explained to me so that I "believe".
I just can't imagine how the "wheelbase" would slow ground speed. D O E S N O T C O M P U T E for me.
I keep thinking that it the track doesnt slip, compress, or stretch a huge amount, the linear feet of track passing by a drive wheel is a linear function of the circumference of the drive wheel times the rotational rate of the drive wheel (RPM). I believe this is invariant with changing track lengths. How does the wheel know how long the track is? Sure the time required to rotate the track one time changes linearly in direct proportion to the change in track length but the length per unit time of the track (sans slippage, compression, or stretching) that goes by is invariant.
If this goes on much longer I may recommend binding arbitration or I may have to sue for peace separately with the various litigants (combatants). Of course these options would be like voting on the laws of physics and the various universal constants. I'm reminded of the school board member who wanted pi made three so kids wouldn't have such a hard time with it in math.
Ahh, my all time hero Galileo Galilei when his friends persuaded him to go before the pope to recant his heretical notions. He had to "take it back" to have his life spared B U T was heard to mutter under his breath as he withdrew "respectfully" from the pope's prescence, "It moves."
Patrick
P.S. Could you give me just a little more detail on the "goes slower if the tracks are longer" thing.
hayden
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I agree, it doesn't make sense and I think now I've REALLY figured this out, but first....
Glenn, my appologies for taking this discussion off course, but it's too puzzling a question for me to resist. I guess we've gotten "side tracked" - yuk, yuk, yuk. But all jokes aside, this would in fact make a great extra credit question for a Mechanical Engineering exam.
Now back to the problem. I now believe that not only is the "It's a Bigger Wheel" model incorrect, but I believe my "It's two ovals" model is ALSO incorrect. The real answer comes from looking more closely at the problem and seeing that it's neither circles nor ovals, but that a track changes shape as it goes around.
Let's look at the same example where we have two equal sized drive wheels of 1' diameter, spaced 2' center to center, with a 1' thick track wrapped around. Now let's look at the track's shape and distances around the inner and outer surfaces.
The track can be broken into two parts, that which is in contact with the wheel, and that which is running straight between the wheels. The sections in contact with the wheels are two half circles, one forward of the front axle, and the other rearward or the rear axle. In these sections, the inner track surface length is 1/2 of the wheel circumference, or 1.57'. The outer track surface is 1/2 of the wheel circumference plus 2x the track thickness, or 9.41/2 => 4.71'. The outer length is considerably longer than the inner length.
Now look at the sections of track between the axles where the track is not in contact with the wheels. Each of these sections (one top and one bottom) is 2' long, and for both of these sections the inner track surface is exactly the same length as the outer track surface.
Now, how is this so? Well, as the track goes around, the outer surface expands as it goes around the wheel, and the expanded outer surface is indeed moving faster than the inner surface, BUT IT"S NOT IN CONTACT WITH THE GROUND! Ground contact occurs only between the two axels, and in that section the inner and outer lengths are exactly the same.
So, I now believe that a trackless vehicle (just drive wheels) will travel EXACTLY the same distance per drive wheel revolution as a tracked vehicle with the same drive wheels, and it will do this regardless of the track thickness. This is because the section of track in contact with the ground is always the same length as the inner track section covered by the drive wheel rotation.
The "Bigger wheel" model does not work because the bigger wheel is never in contact with the ground. The "concentric Oval" model is wrong too because the longer part of the outer surface is also never in contact with the ground.
To summarize, as a track goes around, the length in contact with the ground is exactly the same as the length that came in contact with the drive wheels. As the track leaves contact with the ground at the exact same time that is makes contact with the wheel, and for the whole time it's in contact with the wheel the outer surface of the track expands, either by stretching in the case of a belt, or "fanning out" as in the case of a metal track. The outer surface is moving much faster as it goes around the wheel, then slows back down to the drive wheel speed once it leaves contact with the wheel. If you watch a track you can clearly see this speed change.
A track is exactly like having a person walking in front of the vehicle doing just-in-time road construction (of any thickness) while someone else is walking behind doing just-in-time road destruction and passing the removed material forward to the road builder guy. The tractor speed and leverage is completely unchanged with the addition of tracks, just as the thickness of a road surface does not alter speed or leverage.
I also retract my assertion that wider wheel spacing changes things. It changes nothing.
I think this now makes sense. Does anyone else agree (or care)?
Glenn, my appologies for taking this discussion off course, but it's too puzzling a question for me to resist. I guess we've gotten "side tracked" - yuk, yuk, yuk. But all jokes aside, this would in fact make a great extra credit question for a Mechanical Engineering exam.
Now back to the problem. I now believe that not only is the "It's a Bigger Wheel" model incorrect, but I believe my "It's two ovals" model is ALSO incorrect. The real answer comes from looking more closely at the problem and seeing that it's neither circles nor ovals, but that a track changes shape as it goes around.
Let's look at the same example where we have two equal sized drive wheels of 1' diameter, spaced 2' center to center, with a 1' thick track wrapped around. Now let's look at the track's shape and distances around the inner and outer surfaces.
The track can be broken into two parts, that which is in contact with the wheel, and that which is running straight between the wheels. The sections in contact with the wheels are two half circles, one forward of the front axle, and the other rearward or the rear axle. In these sections, the inner track surface length is 1/2 of the wheel circumference, or 1.57'. The outer track surface is 1/2 of the wheel circumference plus 2x the track thickness, or 9.41/2 => 4.71'. The outer length is considerably longer than the inner length.
Now look at the sections of track between the axles where the track is not in contact with the wheels. Each of these sections (one top and one bottom) is 2' long, and for both of these sections the inner track surface is exactly the same length as the outer track surface.
Now, how is this so? Well, as the track goes around, the outer surface expands as it goes around the wheel, and the expanded outer surface is indeed moving faster than the inner surface, BUT IT"S NOT IN CONTACT WITH THE GROUND! Ground contact occurs only between the two axels, and in that section the inner and outer lengths are exactly the same.
So, I now believe that a trackless vehicle (just drive wheels) will travel EXACTLY the same distance per drive wheel revolution as a tracked vehicle with the same drive wheels, and it will do this regardless of the track thickness. This is because the section of track in contact with the ground is always the same length as the inner track section covered by the drive wheel rotation.
The "Bigger wheel" model does not work because the bigger wheel is never in contact with the ground. The "concentric Oval" model is wrong too because the longer part of the outer surface is also never in contact with the ground.
To summarize, as a track goes around, the length in contact with the ground is exactly the same as the length that came in contact with the drive wheels. As the track leaves contact with the ground at the exact same time that is makes contact with the wheel, and for the whole time it's in contact with the wheel the outer surface of the track expands, either by stretching in the case of a belt, or "fanning out" as in the case of a metal track. The outer surface is moving much faster as it goes around the wheel, then slows back down to the drive wheel speed once it leaves contact with the wheel. If you watch a track you can clearly see this speed change.
A track is exactly like having a person walking in front of the vehicle doing just-in-time road construction (of any thickness) while someone else is walking behind doing just-in-time road destruction and passing the removed material forward to the road builder guy. The tractor speed and leverage is completely unchanged with the addition of tracks, just as the thickness of a road surface does not alter speed or leverage.
I also retract my assertion that wider wheel spacing changes things. It changes nothing.
I think this now makes sense. Does anyone else agree (or care)?
Peter,
You dont have to apologize to me. This thread started with a hypothetical product. You are solving a problem for an actual product.
Your analysis makes sense to be. But, then again, so did all the prior ones as they were argued. Does it make any difference if the wheels are different sized. Then the upper length between wheels is longer than the length on the ground. Or is it only the one on the ground that counts.
You dont have to apologize to me. This thread started with a hypothetical product. You are solving a problem for an actual product.
Your analysis makes sense to be. But, then again, so did all the prior ones as they were argued. Does it make any difference if the wheels are different sized. Then the upper length between wheels is longer than the length on the ground. Or is it only the one on the ground that counts.
jdkid
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hay hayden
read "hang on gugs think about it" my last posting the light bulb goes on in there
catch ya
JD Kid
read "hang on gugs think about it" my last posting the light bulb goes on in there
catch ya
JD Kid
patrickg
Veteran Member
Haydn, I'm most plesed that you recant the aberant "speed varies with wheel base" nonsense. That is another step in the direction of our becoming more congruent in our thinking or expressing our thinking. If our discussion, coming under Glenn's Subject title is an embarassment or annoyance to him we could move to "Of topic, and just for blood, uh er ah I mean fun".
If you put this on a mechanical engineering exam the incidence of school shootings would skyrocket.
I agree with your surmise that the oval model is incorrect however, I would like to hear a cogent explanation of why the lever arm extending from the center of the axle and terminating at the ground's surface under the tread isn't the correct one to use in determining torque and other forces, speeds, and lengths in the system. Please strive to make this explanation NOT rely on rolling wheels along on unrolled tracks. Why this restriction? Because it seems too close to the idea that a thick tire, thin tire or no tire at all makes no difference and that taking the tire off and unrolling it under the car would achieve the same forces, torques, distances per revolution, etc. as driving the car with the tires on. I have some reservations with that. Succeed in this and my model will begin to crumble. I'm not being pig headed and this isn't a negotiation. Laws of physics don't secumb to political solutions. I believe all either of us wants (besides being right) is to find the truth, whether we are personally upheld or proven erroneous is secondary to the truth and its pursuit. Mental gymnastics are a noble employment of our faculties and win, loose, or draw all participants should profit from playing the game. Hope the rest aren't too upset with us.
Oh, by the way, it would sure help put a stake through the heart of my contention if in your cogent explanation you could explain the difference between two wheels without tracks running around them and a set of wheels with tracks running around them in the following areas:
With the exception of increased footprint (reason for the tracks in the first place but that isn't the issue in the is microcosm just now) what is the difference between a wheel of diameter x with a tire thickness of y and a track covered wheel of diameter x with a track thickness of y as the wheel base (inter axle distance decreases, degenerating the hypothetical example into a wheel of thickness x with a tire of thicknes y? You, I am sure recall some of the theory of calculus. Stuff like smoothly differentiable curves vs discontinuous curves like say a tangent (not our personal tangent but the math thingy)? So as the excess track is mentally shrunk and the two axles get closer and closer together until the two axles are one, at what point do we encounter the massive discontinuity. To uphold your view, there must be one. There must be someplace along the smooth transition where a non-linear transformation must suddenly occur as in the case of the tangent curve which suddenly with only an infintesimal change in the horizontal axis has the value of the vertical axis jump from negative to positive infinity.
I know some out there say, "but the front tires and back tires will rub on each other before the axles get too close." Remember we ain't a builldin' one of these to see what it does, we is a cussin and discussin the theory of operation.
Go get a beer while the grownups talk big people talk.
Ok, I'm back. Yup, you would have me down a queen and a rook if you could point out that inflection point or great discontinuity that we should discover following your model if we slowly "morph" the tracked version into the wheels only version with equal wheel diameters and tire size equal to tread thickness.
Ok, the above verbage contains a challenge which if taken and won could mortally wound my assertions and conjectures offered so far, I F you pick up the gauntlet and unhorse the challenger.
I'll just take two Excedrin and stay here in the shade a while...
Patrick
If you put this on a mechanical engineering exam the incidence of school shootings would skyrocket.
I agree with your surmise that the oval model is incorrect however, I would like to hear a cogent explanation of why the lever arm extending from the center of the axle and terminating at the ground's surface under the tread isn't the correct one to use in determining torque and other forces, speeds, and lengths in the system. Please strive to make this explanation NOT rely on rolling wheels along on unrolled tracks. Why this restriction? Because it seems too close to the idea that a thick tire, thin tire or no tire at all makes no difference and that taking the tire off and unrolling it under the car would achieve the same forces, torques, distances per revolution, etc. as driving the car with the tires on. I have some reservations with that. Succeed in this and my model will begin to crumble. I'm not being pig headed and this isn't a negotiation. Laws of physics don't secumb to political solutions. I believe all either of us wants (besides being right) is to find the truth, whether we are personally upheld or proven erroneous is secondary to the truth and its pursuit. Mental gymnastics are a noble employment of our faculties and win, loose, or draw all participants should profit from playing the game. Hope the rest aren't too upset with us.
Oh, by the way, it would sure help put a stake through the heart of my contention if in your cogent explanation you could explain the difference between two wheels without tracks running around them and a set of wheels with tracks running around them in the following areas:
With the exception of increased footprint (reason for the tracks in the first place but that isn't the issue in the is microcosm just now) what is the difference between a wheel of diameter x with a tire thickness of y and a track covered wheel of diameter x with a track thickness of y as the wheel base (inter axle distance decreases, degenerating the hypothetical example into a wheel of thickness x with a tire of thicknes y? You, I am sure recall some of the theory of calculus. Stuff like smoothly differentiable curves vs discontinuous curves like say a tangent (not our personal tangent but the math thingy)? So as the excess track is mentally shrunk and the two axles get closer and closer together until the two axles are one, at what point do we encounter the massive discontinuity. To uphold your view, there must be one. There must be someplace along the smooth transition where a non-linear transformation must suddenly occur as in the case of the tangent curve which suddenly with only an infintesimal change in the horizontal axis has the value of the vertical axis jump from negative to positive infinity.
I know some out there say, "but the front tires and back tires will rub on each other before the axles get too close." Remember we ain't a builldin' one of these to see what it does, we is a cussin and discussin the theory of operation.
Go get a beer while the grownups talk big people talk.
Ok, I'm back. Yup, you would have me down a queen and a rook if you could point out that inflection point or great discontinuity that we should discover following your model if we slowly "morph" the tracked version into the wheels only version with equal wheel diameters and tire size equal to tread thickness.
Ok, the above verbage contains a challenge which if taken and won could mortally wound my assertions and conjectures offered so far, I F you pick up the gauntlet and unhorse the challenger.
I'll just take two Excedrin and stay here in the shade a while...
Patrick
