Tire Overtreads--A Needed Invention

[jdkid]

Hi ya
i found the pic and a bit of a write up about the MF on the ice

http://www.fofh.u-net.com/pole.htm

catch ya's
JD Kid

 

[hayden]

Actually, the relative diameter of the front and rear wheels doesn't matter at all. By definition, they both traverse the same number of feet per minutes for any tractor movement. That's all that matters for driving a boogie trac or whatever they are called.

 

[patrickg]

Sorry but the math doesn't compute. An Example: If the front tires had a radius of 1/2 the rear and you rotate the front tires at twice the angular velocity then voila the desired 4wd situation (just as you assumed). Now add the accessories. The front and rear accessories must be of different thickness. Otherwise consider this: If the accessory thickness is say 10% of the front tire rarius that would be 5% of the rear tire radius and the new front to back ratio would no longer be 1:2 it would be 1.2:2.1 and the 2:1 difference in gear ratio front to back would not "fit" anymore. This would cause a problem with "tracks" or independent accessories on each tire, it doesn't matter which.

Another view: The distance traveled by the front and rear tires should be the same regardless of whether using tracks or conventional tires. The distance traveled by a wheel per unit time is the circumference times the RPM times the time spent traveling. An example: A wheel 1 ft high is: 1 times about 3.14 feet around. If it turns once per second then the axle progresses 3.14 ft/sec . If the back wheel were 2 ft tall then it is 2 times 3.14 or 6.28 ft around. It would have to turn one time in two seconds to go the same speed as the 1 ft high wheel. Now lets increase the diameter of both wheels with either a track or a tread cover thingy (it doesn't matter which). The principle is the same if the additional thickness is just a little bit or a lot so lets make it fairly thick and see a glaring error. Lets make the accessory a foot thick. Now the front wheel is 3 feet tall and goes 3 feet times 3.14 (9.42 ft) per revolution. The back wheel is now 4 ft tall and goes4 times 3.14 (12.56 ft) per revolution. Since the front wheel turns twice for every turn of the back it goes 18.82 ft while back wheel is going 12.56 ft. This might cause some tire scrubbing, loss of traction, wear, steering difficulty, premature tranny and drive component wear and bad things I haven't thought of yet. Of course the accessory will be less than 1 ft thick and the error will be smaller. Do the math, it won't be healthy for the things I listed above.

There was one tricky part. If you missed that you were on a colision path with reality. Adding twice the accessory thickness to get new "effective" diameter used to compute circumference. Consider the leverage thing. From the center of the axle to where the rubber meets the road is a lever arm, this is what the tractor "pulls" to go. It is also a radius of a circle. Increasing the radius adds twice as much to the diameter. If this wasn't so then the physics would be quite different (really wrong, but different). Accessory thickness would not matter as it would be the same as driving over a carpet or layer of anything.

So, if you run separate accessories on the tires and you had the correct thickness for your particular front to rear ratio you could run 4wd otherwise only 2wd. To run tracks you need to either run 2wd or get tricky and run a round tire accessory to adjust for the difference front to back plus tracks.

As a separate observation regarding tire wear. Grit, gravel, and mud will get between the accessory thingies and the tires, tracks or separates. There will be flexing and scrubing with this abrasive mix in there (I assume the need for these accessories was for other than tractoring in a clean room) will chew up the tires faster than regular tire wear by far.

If anyone cares, I vote with the enlightened gentleman a few posts back who said, and I paraphrase, it would be cheaper to get an extra set of tires and wheels. Sure would.

Now then, there is a company that makes tracks to replace the wheels on a 4wd truck. I have seen videos of a P/U truck flying up dunes in 4wd on four tracks. Steers just as it always did and the tracks clear the front sheet metal when steering. Comes in various models for different size trucks. Maybe they would provide tracks for a tractor. They tout the advantages of large footprint low PSI, goes good on snow, sand, soft ground etc. They were N OT cheap and couldn't compare to the price of another set of mounted tires but will do what N O tractor tire that will fit on your tractor can do regarding traversing soft footing. The demo I saw showed the truck driving up with conventional wheels with tracks in bed (pretty much filling bed) They jack up the truck one wheel at a time and put the tracks on. Put the wheels in the bed and then do some amazing dune climbing. Would be great to run the river sandbars, winter snow, etc. Of course it raised the truck like a good size lift kit which was not a bad thing for off roading but yoiu have to be mindful of the increase in height of CG and the traction They don't slide sideways to relieve momentum very well and would roll if you tried to do some Mario Andretti stuff. Probably wold work super on a tractor if yo didn't over stress them pulling something. Of course the MFG could supply safe limits I'm not experienced beyond seeing the demos.

Patrick

 

[patrickg]

Thanks for the Antarctic tractor story URL. Nice read. Ought to read it to my L4610 to inspire it to greatness.

Patrick

 

[jdkid]

Hi ya
Oh man i'm holding back the tears from my eyes LMAO got a pic in my head of ya sitting beside ya tractor with it all tucked up like a 5 year old listering to grandad's old time storys that aside i don't think MF used it as a selling point
catch ya
JD Kid

 

[hayden]

I see where you're going with your reasoning, but I think it's incorrect. Tracks don't increase the diameter of the wheel. The wheels travel continuously around the inner surface of the track, not the outer.

Think of it this way. Take the track, cut it, and lay it out flat. Make it as thick as you wish. Now drive the tractor down it's length. As you get to the end, quickly run around the back, pull the track up over the wheels and around to the front so you drive over it again, and again.

 

[patrickg]

Please translate LMAO.

Thanks,

Patrick

 

[patrickg]

Hayden, I sure don't want to make an ememy so lets pursue this for fun, no money, no ego, not even a rootbeer float, OK.

Lets say the track is 15 feet long and the wheels are approximately 1.59235668789808917197452229299363 ft in diameter including the track thickness (twice). This would put the wheel base at 5 feet. Each rotation of the wheel would advance the axle 5 feet. In three rotations the track would make one full circuit around the wheels and baring loss of traction would advance the axles (and vehicle) 15 ft.

Now if we were eyeball to eye ball I could get an amen or you could dissagree and I would explain the hard part.

Now take the track off and lay it out on the ground. Just for grins, lets say the track is sturdily built and is 6 inches thick. The wheels then (sans track around them) are now approximately 0.59235668789808917197452229299363 ft in diameter. Each rotation of a wheel this size (whether on the ground or on carpet or rolling down the track we have put on the ground) advances the axle 1.86 ft approximately. Since 1.86ft clearly does not equal 5ft the axles advance different distances with track on and track off.

I'll pause here until my temples stop throbbing. I haven't had anyone force me to actually think in so long, I'm glad to find out I still can. I'm reminded of the lecturer who said, "If you make people think that they are thinking, they will love you but if you actually make people think they will hate you." I hope we both avoid his pronouncement.

Hayden, thank you so much for your question. I hope this cleared it up for you but if not A N D no other brave souls out there want to jump in, I could try to find yet another way. Or alternatively, you or someone else of your persuasion might want to try to explain my error. Maybe I just don't get it.

I used to have a chuckle every time some mathematician wanted to prove something so badly that their subconscious would introduce an error into their proof to make it come out the way they wanted. They would publish in a journal or deliver it as a paper in a convention venue. Someone would see the booboo, ream them over it, the author would publish a thank you for noting that error type of a message and resubmit the proof with that error fixed and another introduced to make it come out the way he wanted. Sometimes they finally prove it sometimes they go down in flames and never make the proof (it might not be provable). This is not an isolated event except it often happens at mathematic society meetings and not so often in journals.

Patrick

 

[patrickg]

Heat death of the universe? Now I have something else to worry about. So when is that supposed to happen?

I thought knowing that the answer was 42 would have been more useful but now there is this heat death thing. Is that for sure our universe?

Patrick

 

[patrickg]

Hi Hayden, I thought of another thing. If the relative size of the front and rear wheels didn't matter would that mean similarly that the relative sizes of the pulley wheels over which a fan belt kinda thing is stretched also doesn't matter and even though they are different sizes they would both spin at the same RPM or that changing one of them wouldn't effect the RPM of either. Doesn't a smaller one have to spin faster to move the same number of linear feet of belt or else it will be slipping? If both pulleys were gear driven from same motor wouldn't it matter what the two gear ratios were in relation to the sizes of the pulleys? Is this different from your envisionment of a tracked vehicle? If yes, how?

Patrick