Tire Overtreads--A Needed Invention

[jdkid]

Hi ya
LMAO=laughing my @$$ off
ROFLMAO= rolling on floor laughing my @$$ off
catch ya
JD Kid

 

[jdkid]

Hi ya
hey i had a think on this and ya math's seem's out to me

"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."

as the wheel only runs on the bottom track the diameter would not include the top track, the wheel it's self is the driver whether the track was flat or linked ie if i cut the track and drove down it i would travle the same distance as if it was linked
i think the point hayden so getting at is (step in if i'm wrong)if i put a track from back wheels to front(even tho they are diffrent sizes)both wheels will cover the same distenice(SP)one may do 100 turns and the other 187 turns (or what ever depending on size) the point about the fan belt it true but where the belt runs (bottom eage of "V")will travel the same distenice even if the gearing is 4to 1
good mind bender tho
catch ya
JD Kid

 

[patrickg]

OK guys, I'll try some more. Is this a conspiracy, everybody really gets it but wants me to struggle to try to explain it in different ways? O R am I diging myself into a hole, deeper with each abortive attempt. I really don't care if someone proves I'm wrong but I require proof, not vague conjecture based on gut feel or whatever. It gets a lot harder when you get rigorous, beyond the "I think there are 12437 angles on the head of the pin", but no one actually counts them.

Tracks laying on the ground are a red herring and shouldn't properly enter into the investigation. The radius, diameter, or circumfrence of the wheel inside the tracks matters.

I think before launching another couple thousand words I will request someone, anyone to point out the specific error(s) in my previous analysis. Please be a little more specific than, uh, I think its wrong (that might be mistaken for I don't understand it).

A couple small issues:

You said: as the wheel only runs on the bottom track the diameter would not include the top track

What matters here is not sophistry but engineering and math. If the half diameter (read radius) includes track thickness that is good enough.


A N D
... if i put a track from back
wheels to front(even tho they are diffrent sizes)both wheels will cover the same
distenice(SP)one may do 100 turns and the other 187 turns (or what ever depending on...

YES! one may turn 100 times the other 187 but when the tracks are LOCKED to the wheels by whatever means, friction, gears, pixie dust..
the wheels must each be driven at the correct ratio or the track must expand or contract A L O T if all wheels are driving (none idling) as with 4wd. If you are assuming 2wd then we have no further discussion.

A N D
...where the belt runs (bottom eage of "V")will travel the same distenice even if the gearing is 4to 1

YES!! A N D if you drive both pulleys from the same motor via a transmission, the transmission must drive each wheel at the correct ratio or there will be massive binding and or slipage. Imagine this with an extremely thick belt running on the ground. Each revolution of the belt around the wheels, propels it a belt circumference (outer perimeter where the rubber meets the road) distance ahead. Keep same pulley wheels but put on even thicker belt. Now the perimeter is greater. One rev of belt propels the beast farther than before. Do you agree so far? If yes, we done it!
I didn't change the pulleys just the belt thickness and it went farther with a thicker belt. But how can that be? It is because that is the way it works, not the lay the belt on the ground diversion.

Need more easy to visualize explanation? The belt laying on the ground and being driven over has no difference inside to outside. When wrapped around a wheel the inner surface travels the same distance as where it contacts the wheel (pulley) B U T the outer surface of the belt (track) travels farther as it is farther from the center of rotation (by the belt/track thickness. Think what would happen if you had a 1 inch wheel and an 11 1/2 inch thick track and could get it to function(this is a thought experiment, we ain't buildin' it so binding and flex isn't gonna stop us).

Each rev of the wheel without track would move axle forward 3.14 times 1 inch = 3.14 inches
B U T with the track on, one rev would move the axle forward 3.14 times times 24 inches = 75.36 inches

Having the track wrapped around the wheel increases its effective daimer by twice the thickness of the track. This is like putting taller tires on your car, it goes farther with each rev of the wheel. Imagine that yoiu have car tires with really really thick tread. Measure how far it goes down the road when the wheel turns one time. Now take a sharp knife and peel the tire. Do it neatly so you remove 20% of itsdiameter in one thick strip. Set that removed strip asside for later. Now rotate the tire one rev and notice that it goes a lot less distance down the road in one revolution. Now lay out the piece yoiu peeled off. Run over it with the peeled tire. Oh wow man, if doesn't effect the distance we go down the road does it. Runing on the pavement or a piece of removed tire makes no difference.
B U T when the ruber was on the tire it went further J U S T L I K E I T W A S A C A T T R E A D.

I think you probably got it now but if you are unconvinced, point out my error(s) in detail, with precision, so that I may determine the actual point of departure in our separate understandings. I would be just as happy to be proved wrong as to get your light bulb to come on. I enjoy the communications challenge (well it frustrates me some too 'cause I spell so poorly, type so slow, and the turn around on messages is so slow its tough for me to remember exactly the board position (chess) so to speak.

Thanks for hanging it there with me, we'll converge soon I think.

Patrick

 

[glennmac]

Having started this, I confess to being lost. If we are talking about bogie tracks, you wouldnt run the wheels in 4wd. You dont need to, because you have this big track connecting the wheels and doing a much better job than 4wd can do. Therefore, you would presumably drive the bogie track by the rear wheels alone and let the fronts spin free. Then it doesnt matter whose math is correct. Or does it.

Maybe I'll withdraw my patent application.

 

[patrickg]

I'm sorry but my karma ran over your dogma!

What has reality got to do with this for goodness sakes. We are just having fun threshing out the details. Sure it might work with 2wd, S O ??

Seriously, it is a great idea but I think the intrusion of sand, gravel, mud, grit, etc. coupled with the inevitable flex of pneumatic tires will wear the hell out of the tires and the tracks too if they aren't something real hard. Manuevering should be interesting as well. The tracks I saw on a pickup replaced the wheels entirely and steered the same as tires. They were used in 4wd but of course they were 4 separate tracks, one per wheel. Well worked out and seem to function fine. It would be worth asking maker if they could supply units for tractors.

Patrick

 

[RPM]

I think that jdkid is correct (beads of sweat on my forehead, furrowed brow, smoke coming out of my ears) /w3tcompact/icons/smile.gif

I believe that in this kind of problem you would consider the inside of the track as an 'unrolling carpet'. Hence it's just as if the tractor is driving on an elevated platform.

The linear velocity of any point on the outside of each tire - the point in contact with the inside of the track - is the same.

The radius of each tire is different - and so is the speed of rotation - but the linear velocity is the same. This is the same physics that stops tires slipping and scuffing when you drive in a straight line.

velocity = radius x (angular velocity in radians)

(360 degrees = 2xpi radians = approx 6.18 radians)

I did note that the Massey Ferguson in that polar expedition web site had a third wheel between the front and rear axles. Looks like this was probably free-running and the tracks only ran between the rear and mid axles.

Trying to have tracks between front and rear wheels and still steering with the front wheels would cause damage. All the tracked vehicles I know of do it by differential braking/acceleration of the whole track.

Halftracks were quite popular in World War II - especially amongst the Germans and Russians. I believe the US also used them ... this is the kind of setup I am talking about:

http://www.ping.be/~ping9503/BMVT/halftrack.jpg

Edited: removed in-line image as it was too large

There's also some interesting looking hybrids out there ...

Patrick

 

[RPM]

Oops - didn't realize that last picture would expand so much ... here's another that you might be interested in ...

This is a Ford 8N with tracks

Patrick

 

[MJB]

My father used to have an old Allis Chalmers WD with a kind of half-track setup on the rear wheels. There was a separate bogey wheel ahead of the rear tire on each side and slightly elevated off the ground. The mounts for the bogeys were spring loaded to hold tension on the tracks. The tracks went around these bogeys and the rear wheels, complete with regular tires. The inside of the tracks was fairly smooth with small bumps on them for the rear tire lugs to grab onto. The outside of the tracks had heavy 2" tall cleats on them. On flat hard ground the front part of the tracks had very little weight on them due to the elevation of the bogey wheels. This made it much easier to turn the tractor with the front wheels than if the full track was in ground contact. As you ventured into softer ground more and more of the track surface came into play. You quickly learned why tractors have turning brakes. With super wide floatation tires on the front wheels and the tracks installed, that tractor could go anywhere on soft ground. This unit was not very kind to lawns however./w3tcompact/icons/smile.gif

I love the smell of diesel in the morning. /w3tcompact/icons/smile.gif

 

[MJB]

Egad... looks like RPM added some more info while I was typing./w3tcompact/icons/smile.gif That picture of the MF and the Ford 8N look just like the setup on my dads old Allis Chalmers.

I love the smell of diesel in the morning. /w3tcompact/icons/smile.gif

 

[jdkid]

Hi ya Patrickg
most of what ya saying i'll run with .and if the front wheels where idlers no prob(don't know of any dozers with twin drive)but if set up right the front could be driven.now like ya say the tracks add to the prob,start with tracks cut and laying on the ground.... if the tracks were say 1 foot thick and you did 10 turns of the driver (and the driver had a cercumfrince(spelling was not a strong point )of 4 foot it would travel 40 foot down the tracks but if the tracks were 3 inch(same driver just diffrent tracks)for 10 turns it would still only go 40 foot ,now join the tracks up and try again you will find that is dose the same ,"no one has brought up that the tracks are hinged" at each link making the area of contact ie track face plate is the same flat or bent around the driver/ilder when wraped around the driver a %of area is air not contact area if i knew of someone spliting a set of tracks i could take my tape and get the good oil on what happens ,might even have to send it in to the X files
i'm sorry i could not use numbers ,figers graphs to show what and how i mean it to work but trust me it dose, the outside mesurments/speed will increse when wraped around the drivers but come back to the speed of the driver once flat .but if the tracks were belts yes the thicker they were the faster ya would go, but where the driver meets the belt and the inside speed of the belt would remane the same and if the gearing for both drivers were = then no prob
i think where there has been a mix up patrickg is i have been working on true tracks ie steel with hinges where ya working on a fat belt , most rubber tracked tractors have a thin belt so it flexs with out the need for hinges (ie CAT"s big rubber track tractor)
catch ya
JD Kid