Tire Overtreads--A Needed Invention

[patrickg]

Thank you very much, I do believe we are in basic agreement, at least CLOSE ENOUGH now that I understand the minor differences in our approach a bit better. I was a tad theoretical and you practical but appreciated.

How many acres of land per head of beef on your place or are you doing crops? What about some pix from your part of the world, not the travel brochure BS but out in the countryside where you are. That would be a treat

Most of us have never and will never see the place first hand but could appreciate a working mans perspective.


Patrick

 

[jdkid]

hi ya patrickg
well yea i look at things from hands on (read as not the brightest candle on the cake!!)only went to school to eat lunch and make friends ok we are moveing at this stage to a new farm 1800 acres with about 1000acres workable so i'll be flat out regrassing /fenceing /track making etc etc. we manly fatting sheep (3500 ewes ,fem sheep) and some cattle but till we get the place up and running we don't realy know what we will do might run 150 odd cows and 4000 ewes with winter contract lambs (fattern and sell in winter) i'll get some pics once i get up there might stick them on a web page so it dose not load up the forum and then people can call in for a look at anytime i have a few mates who want pics too so it will kill 2 birds(sorry bird) with one stone hope to have pics of gear ,stock ,viwes etc etc so ya can pick what ya want to see
catch ya
JD Kid

 

[patrickg]

Hey, that will be just super. I know that I for one will certainly be looking forward keenly to seeing the pix. Maybe you could post the URL at the photos section of this tractor site. Ever see the movie, "Quigly Down Under" ?? that is what popped into my head in expectation of seeing the pictures. I know, wrong country, but a tad closer to our situation here.

Best to you,

Patrick

 

[jdkid]

Hi ya
yep i have seen that film (i do cowboy shooting so western pics top the list)
there have been some films made in NZ
shaker run,battletruck, vertacal limet (climbing film )lord of the rings!!! ment to be great i know a few mates who were horse riders in it .hercales(?)and the other one starts with "X" (damm spelling sucks!!) J park 3 is ment ot be filmed here
i'll think of more during the day
catch ya
JD Kid

 

[patrickg]

"Ledgend(s) of the Fall" "ANZAC" not exactly western but good

What do you shoot? Not at, with? I had some fun with my .44 single six Old Ruger Blackhawk 44 maggie. Got picked up as an extra in a western entertainment groups shoot out scene. Made it to the last bit with only 3 standing but then I died spectacularly and the two main characters shot it out. Amazingly the guy with the white hat won!

Patrick

 

[hayden]

The pully model is a good one. If you use a thin belt, the pullies rotate at speeds propotional to their diameters. If you use a thicker belt, do the pully speeds change? I don't think so.

I'd like to second your comment that this has made me think harder than I have in a while, and is dredging up all my old math and mechanical engineering which I sadly haven't exercised in a long time.

I've got a challenge now to show which of the two models is correct and more interestingly, why? I quite honestly can't show why your model of "the wheels diameter increases by the track thickness and behaves just like a bigger wheel" is wrong, if it even is, but I'll go draw some pictures and try to figure this out and convince myself, and hopefully some others, through math, how the heck this works.

Right now, I don't think the track simply creates bigger wheels. If it does, your math is correct and I agree with you. What I think is the correct model is that the track forms two concentric ovals (or approximately that shape). Like a race track, everyone knows that the inner edge of the track is a shorter distance around than the outer edge.

The drive wheels go around the inner surface of the track, and the progress around the inner surface is determined by the rotational speed of the wheels and their diameters. Because this progress around the inner surface is based on the drive wheel diameters, it is identical to the progress those same wheels would make on a flat surface, and the relative rotational speed of the front and back drive wheels would be the same as on a flat surface.

Now, lets look at what happens to the outer track surface. The outer surface is longer than the inner surface. When the drive wheels make one full rotation around the inner surface, one full rotation around the longer outer surface has also passed by. This means that the track driven vehicle will move faster for a given drive wheel speed since one drive wheel trip around the inner surface causes one full trip around the outer surface in contact with the ground.

All this said, I think the relative speeds of the drive wheels stay the same as on a flat surface because they are traveling around the inner surface of the track at a speed and rotational velocity determined by the drive wheel diameters and it is completely independent of the track thickness.

The traveling speed is faster based on the track thickness, and drive wheel torque is proportionally reduced as well.

I'm off to do the math to see if this holds together.

 

[jdkid]

hi ya hayden
ya right in some ways
Now, lets look at what happens to the outer track surface. The outer surface is longer than the inner surface. When the drive wheels make one full rotation around the inner surface, one full rotation around the longer outer surface has also passed by. This means that the track driven vehicle will move faster for a given drive wheel speed since one drive wheel trip around the inner surface causes one full trip around the outer surface in contact with the ground.
but ya still working on the very outside being solid which on tracks it's not, hinged /cut or strechs to wrap around the drive or ilder if the driver is doing 2 mile per hour the inside of the track is 2 mile per hour the base of the track is doing 2 mile per hour the only time the outside of the track speeds up is going around (streching/expanding)the driver/ilder here's the kicker cut a track in 1/2 lay it flat (dozer track!)what do ya find????????seeing most people don't have dozer tracks laying around ,ya got a old bike chain ?starting to see where i'm heading?
catch ya
JD Kid

 

[hayden]

OK, here's why I don't think you can model this as a wheel with a larger diameter, and why the different models produce different numbers.

Let's make the example simpler. The wheels are 1' in diameter and are the same size front and back, the track thickness is also 1', and the wheels are spaced 2' center to center.

The "It's a bigger wheel" model says that, without a track, one wheel rotation causes 3.14' of travel. With the track the diameter becomes 3' and one rotation causes 9.42' of travel. The distances travelled are directly proportional to the "wheel" diameters. This is because it's based on the circumference of concentric circles and those are proportional to the diameters of the circles.

The "Oval" model says that there are two concentric ovals representing the innter and outer surfaces of the track. The distance around the innter oval is 3.14' (the two half circles on the ends) plus 4' (the top and bottom straight sections) for a total length of 7.14' The distance around the outer oval is 9.42' (the two half circles on the ends) plus 4' (the top and bottom straight sections) for a total length of 13.42'.

Now, it takes 2.27 rotations of the drive wheels to move the inner surface one full time around (7.14/3.14). In those same 2.27 rotations of the wheels, the entire outer surface must also pass by exactly once giving a traveled distance of 13.42 feet.

In the "Bigger wheel" model those 2.27 rotations of a 3' diameter wheel would cause 21.38' feet of travel. But, the outer length of the track is only 13.42 feet.

Why the discrepency? Because the track is an oval, not a circle, and the circumference of concentric ovals is not proportional to their radii. 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. One degenerate case is when the two drive wheels are concentric (an oval that's a circle). Then and only then does the "Bigger wheel" model apply. The other degenerate case is an infinitely elongated oval, and then the oval thickness doesn't matter (this is back to driving on a smooth flat surface).

My take away from this is that track thickness will indeed act as gearing for the tractor and change it's speed and "power", but that the drive wheels will see the track just as they see a flat surface, and hence the drive ratios of the front and rear wheels is the same for a flat surface and for a tracked device.

Make sense?

 

[jdkid]

hi ya hayden
thats kinda what i'm getting at but my way's a bit more laymaned (work hardened handed)
catch ya
JD Kid

 

[jdkid]

hang on guys think about it???

Hi ya's
now i don't have the maths to back this up but work on haydens pic in ya head 2 wheels 1 foot round 2 foot centers ,he did the maths right (i think)but we have all forgotten that the tracks only touch the ground at 6 o'clock on both wheels ,the track layed out flat is =inside and out (cut and layed flat) when it is wraped around the end of each wheel it strechs or opens up (like a dozer) only then dose the speed of the outer mesurment increase but be couse it is not touching the ground the speed and forward travel is the same as the inside mesurment, power and gearing is not changed with the thickenest of the track and can be proved i'll come up with a hands on way of doing ... ok got it get a push bike and tip it upside down ,now stick some paper cleats on to the out side of the chain ie faceing away from cogs,now take note of chain between cogs at 6 0'clock cleats move at same speed as chain (right!!) but where chain wraps around cogs cleats speed up cos furer from center meaning that foward speed will be the same as inside speed
almost 1 point for the little guy here i think
catch ya
JD Kid