Tractor Pulling Madness

to top it all off ken.it was a woman driver.and i do believe she had a slight weight advantage over you...hang in there

I'd go with taller, narrow tires.  More tread on the ground

My dad has an M john Deere, why I have no idea it is the most useless thing I have ever seen in my life.

true, cant argue that

A larger diameter tire will always yield higher tractive effort than smaller diameter.  Dick's note about old hard tires not falling over is also true.  A tire with greater ply count will be less likely to deform under stress, but hardness and ply count can work against you when trying to 'air down' for more surface.  Likewise, airing down too far will increase rolling resistance, and require more horsepower to make the pull as weight transfers to the hitch. 

Having a 'stable' pulling platform is really the key to being successful in pulling-  if the tractor is jumping around, the amount of horsepower, weight, tire type/size changes will have very little impact on the ability to make consistent pulls.  That in consideration, I'll second Dick's note about hitch height, and include that when you weight the tractor, start by making it meet your organization's 'rules', and then set up your weights so that you can comfortably pull a test-load around with the front wheels off the ground... and not bang the front wheels uncontrollably. Once you can control it with a serious test-load dragging behind, make your other adjustments little-by-little and take good notes. 

Then, when you get to the track, look closely at the track, see what other guys are doing, and compare their performance.  THEN... watch what the TRACK is doing. The track will change substantially from first pull to last, and the guys that win, will be able to make a consistently good pull through those changes.  This also means they can PICK and hold to their line (stable platform, and being able to steer with wheels up!).

Tractor pulling is like a triathalon... you have to get the basics down, and nothing you do will actually 'win', but making the right 'mistakes' will cause you to lose.  Fortunately, in tractor pulling, if everyone gets to go home without injuries, and got to make at least one pull, then you're a winner regardless.  A bad day of [insert your favorite pastime here] with good friends and family is always better than the best day at work!

I have never pulled small light tractors, but I did build a big Diesel for a guy that pulled smaller antique gasser. We had one hell of a time with him because what works on big diesels, does not work on lighter tractors, and we couldnt get him to change his pulling approach with high HP heavy diesel.

Allis engineers pretty well covered what hitch height does for you in most operator manuals. The heavier the load the less the engineers recommend you to run for hitch height for operators safety. So do I hang enough weight out front to utilize the maximum hitch heights down force for traction or do I lower the hitch and loose down force to keep from hanging weight out front . I guess its a question one faces when faced with various rules.

Edited by mlpankey - 29 Oct 2011 at 1:55pm

Regardless of what type of competition it may be, EVERYTHING ALWAYS comes back to the rules.

You weren't disagreeing with me, ML- I wasn't referring to tread height, and you're right, too tall a tread WILL fold over.  My reference was to overall tire diameter... and the empirical data found in the Wismer-Luth study illustrates that agricultural tractive effort is not only pretty simple to predict, but also based on a relationship of very simple factors- tire height, ratio of weight upon driven wheels vs. weight upon undriven wheels, and rolling resistance.  The result of performing a calculation will give a pretty accurate relative figure not only of tractive capacity, it will also illustrate the amount of additional horsepower required to compensate for slip, and furthermore, the amount of TE rise which occurs as slip occurs.

Harold (Luth) put it best, saying something to the effect of:  "Once you hit the calculated TE limitations, everything beyond is a state of slip, and from that point on, you can GET more TE, but it means applying incredible amounts of horsepower, and generating more slip".  {This was said while we sat in beach chairs, around a campfire on an island in the middle of the Mississippi River, looking at  Cordova, Illinois.}

The point is pretty simple-  if you run a 40" tall drive tire, and replace it with a 60" diameter tire, correct the drawbar height and gear ratios accordingly, you'll get more drawbar  pull from the taller drive wheel.  Reason:  More contact surface (think geometry of Chord... http://en.wikipedia.org/wiki/Chord_%28geometry%29), lower rolling resistance, and greater drag required in order to break cohesive soil.

And the deeper explanation of track conditions- If you do a soil sample study, you'll find that there's two ends of the soil spectrum that yield very poor TE capacity.  First is very sandy or loose soils, the other end, is very very hard soils.  Just walking on them is an excellent illustration of why the 'middle ground' yields best performance, and again, this was a lesson illustrated on a river-island sandy beach.  Walk through the really loose sand for a quarter mile, and you'll be an incredibly tired dude.  The softness requires more energy, because it isn't solid footing... you're fighting the condition of sinking-in.  From the other perspective, if you walk on smooth concrete, you'll slip because you'll have nothing to push against when the slip-point occurs.

The middle-ground, is having a type of soil that sticks to itself (cohesion), and can compact just-enough so that the agricultural tire impresses a 'pattern' to match the tire... at which point, the tire has something to apply force directly against.

When you reach the point where slip STARTS to occur, what's happening (assuming the tread 'fall over' condition that ML noted isn't occuring), is that the soil has reached the limit where it can no longer stay stuck together under the SHEAR strain that the tire's lugs are applying.  One thing to keep in mind here, is that the tire's lug design COMPACTS directly below the lug, and in doing so, actually INCREASES the ground's ability to resist compression under shear.  This doesn't mean that the tire loses it's capacity to do work, but the applied horsepower -to- drawbar force relationship changes dramatically.  This happens because the tire is SINKING, and a substantial amount of horsepower is required in order for the tire to 'climb' back to the surface.  Realize here, that a larger-diameter tire suffers 'climb loss' horsepower much less than a small-diameter tire, just like it's easier to roll over a tree limb with a monster truck, than with a skateboard wheel.  From a TE calculation standpoint, it's the larger wheel diameter's advantage that horsepower-to-slip relationship is much less of a punishment, than a smaller diameter tire.

Eventually, when slip occurs, the tire will be 'tearing' soil from it's position.  Let's say the wheel turns 110 feet, but the tractor only goes 100'... that's a 10% SLIP condition.  Going to a 20% slip condition may bring up drawbar horsepower by say... 4%, but it may require input horsepower to DOUBLE.

Pretty cool math, really, and note that when Harold was doing this study, they didn't START with math... they started with empirical evidence-  they set up tractors, and applied the conditons noted... seemingy opposite of how grad students do it today, but I guess that's why they call it 'old school' (and probably why it all works well).

Live weight:
My experience with pulling... <and note that I have only two types of pulling experience- 1) Casual sled-pulling (primarily garden tractor, but occasional full-size pulling) and 2) Practical pulling... moving large objects with tractors on-the-farm> is that regardless of how the 'hard' weighting is done, that the 'live weight' factor is incredibly important in a successful pull.  A big heavy guy on a properly set up puller can start his pull, and once the wheels are up, steer it down the track just by sitting still, and extending one hand to one side, or making a slight lean. 

My most memorable, was making a full pull with a Cub Cadet compact 4x4, front wheels up, with turf tires on a well-torn-up track.  To steer left, lean a smidgen to the right.  This causes the left wheel to lose traction, and the right grips a little better to pull the front end over to the left.  This ain't a new technique, but for guys who DON'T use their tractors for agricultural situations, they don't get the chance to exercise it often.  I had a 7500lb slug in my barnyard that I moved around, and every time, I had to steer it with wheels up, and never touched a brake.  Being able to master this, meant being able to pick the best line down a torn-up track.  It's not an easy task to learn, though, if the balance, drawbar orientation, etc., aren't set up to make for a stable pulling platform.  Once a driver loses control of his machine's stability, the pull is over.

field and road especially if they are road worn and have about 3/4 a inch tread.

JW      Camp was  talking about garden tractor pulling most of the time. I think steering with front wheels off the ground can work by shifting your body weight only on a garden tractor that weighs 500 pounds or less.

2 mysterys remain. JW is my witness.

    I got beat good in 3000 and 3500 by another CA on little old junk 10 24s. I'm pulling 13-6 24 Firestones at 4 psi. Then we both get beat by a M Deere in both classes. I'm still scratching my head, It's like having a bass boat with all the high tech gear gettin out fished by kid in a 10 foot flat bottom aluminum boat. And then a little lady from Arkansas fishin from the bank sittin on a M Deere wins the tournament.

   Oh!!  I forgot to mention. The the Kid on the other  CA  had water in one rear  tire. Did you know that JW? 

i'm Sorry Mr Kamp. I got this  message on a black screen " A error has occured. Try again later"  Kinda like my pullin. Try again later. I will put some of your ideas to work. I wish I had a sled of my own to test theories.

With my ASAE hitch on the B I get hardly any front lift. If I remove it and pull direct from the drawbar the front comes up. This goes against the theory of the shorter the better?

I have never heard of tire height changing gear ratios, I thought that you had to open the tractor up to change gear ratios and change the gears.  Tire height will change the speed at which you go down the track with all other conditions being the same, such as gear ratios and engine rpm.  

Yes, what ML MEANT is that going to larger diameter tire changes Effective Drive Ratio.  It's all 3.14 * tire diameter there.

Reason why a narrower tire will often out-pull a wider, is because of soil properties I noted above.  Soil has the ability to be compacted, and when tire pressure (particularly the lugs) compacts it, the soil's shear strength is increased.  IF you run a wider tire, the lug contact force is distributed over a larger area, which means compaction force is reduced, and shear strength of the soil falls.  This is where chosing the tire for the track is of utmost importance- if you're on dry sand, you'll get very little shear strength through compaction, and you'll get very high rolling resistance because the tire digs and sinks down, having to waste power climbing out. Running a wider tire reduces horsepower loss here.  If you're on very hard soil, the wide tire doesn't create enough compaction pressure on the lugs to cause them to 'bite' in.

The reason why drawbar length and hight make a difference, is illustrated by drawing the tractor, drawbar, and sled from the side-view.  Draw a straight line from the middle of the driven wheel, through the center of the RIGID DRAFT POINT.  By this, I mean the point at which the part of the draft linkage which is rigid with respect to the tractor.  Let's say you have a standard drawbar, non-swinging, locked down, 10" above the ground, 20" back from the wheel center, and attached to that is a chain.  The chain is a flexable draft point, so draw your line to the point where the chain attaches.

Now draw a line from the center of the tire CONTACT point, up through same point as the chain attachment point.  Now draw a line from wheel contact to center of wheel, and you have a triangle.

The BOTTOM side of the triangle is the portion of draft reaction which causes the front tractor wheels to lift under wheel thrust.  The top portion, is the reaction which occurs under draft tension and transferred weight (from the sled).

The FRONT side (the vertical line) illustrates the initial angle at which the tractor SITS (if you're running small front tires, it'll be leaned forward).

NOW... draw a line from the CENTER of the vertical line, through the center of the draft point... this distance is the length of draft.  Longer this line is, the more stable your draft will be, but the less control you'll have while trying to steer... because the draft load will WANT to point the tractor straight ahead, as long as right-left traction is equal.

Now for the last lines:

Draw a line from the chain connection point, to the sled connection point.  Now draw a horizontal line from the sled connection point to a point directly under the chain connection point.  This is the thrust angle which is applied to the drawbar.  As the sled is drawn harder (either by greater draft force, or more weight transfer on the sled), this angle will cause the balance of tire-force vs. nose lift to change, because the draft load is not straight rearward.

Now, draw two vertical lines- one from the drawbar to the ground, and another from the sled draft point to the ground.  This is the length of the draft chain.  Longer you make this chain, the lower the thrust angle, which means changes in draft force, have a lesser effect on the forces occuring at the drawbar.

Mebbie I should draw this out...

Anyway, the point here is, the 'magic bullet' for having a successful pull, is having a draft arrangement which 1) meets the rules, and 2) causes a STABLE PULL over the whole length of the track, and finally 3) ALLOWS the operator to PICK HIS LINE.

If you have a platform that's too stable under draft, you'll be limited to driving whatever line IT wants... which means, it'll be totally steered as a result of the sled's drag, and pulled off course by whichever tire has least traction. 

If you have a platform that's unstable, it will jump, bounce, and wig-wag all over under draft load.  Tires that bounce on the ground don't get good traction.  Tractors that can't settle down and pull straight, will not stay on the course.