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Re: Pulling Tractor. JD/IH????
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Posted by John T on February 10, 1999 at 13:19:14:
In Reply to: Pulling Tractor. JD/IH???? posted by Sean H on February 10, 1999 at 11:25:51:
Sean, Im a JD owner and fan so I hope my buddies dont get mad at this, but being an engineer, I think one must accept certain facts of physics. Although JD's (talkin antique classes here and 2 cylinders) can be made to outpull an Ollie or IHC and I love it, the problem with JD's is that they are low rpm high torque while IHC and Ollies are high rpm and lower torque. When pulling a progressive weight sled, the higher rpm faster off the line Ollies and IHC's have the advantage of storing kinetic energy ( 1/2 m x v squared) in the sled which builds inertia and momentum that helps farther down track when hp drops off. The JD's get most hp from torque (hp = function of torque x RPM) and when they drop rpm and lug down their hp doesnt go down that much. Ollies get most hp from rpm so when they lug down their hp drops more drastic. Because of that, in a dead lug pull with no progressive weight, the JD's have the big big advantage. Still, the high revving ollies and IHC's faster off the line can store early energy in the sled and use it later which the JD's (slower off line) just cant as well. I have pulled, observed, and studied this a great deal and if you watch those tractors that have the most speed built up and really get that sled going, they usually win. The JD's are the best dead pull luggers, but they just dont get much early speed due to their rpm limitations. Now, those guys that get the revs way up on the JD's are hard to beat. Still, the engine dynamics limits their rpm as compared to what those Ollies can turn up to which makes the high revving fast off line tractors hard to beat versus a JD even with more hp that cant build up and store kinetic energy and re use it like the Ollies. Of course, there's pullers with JD's that beat Ollies if they really get them turned up (and I love it), but Im just giving you general engineering things to consider as you asked. High RPM fast off line tractors that store kinetic sled energy are just usually better pullers than slow dead pull luggers. If one gets a tight tight biting track, then the JD's do better because towards the end they have that terriffic torque and hp almost still as much even when rpm drops. But, the bites usually not that good which favors those that built up speed at low weight part of pull. Thats my story and Im stickin to it even though my JD buddies will come up with these stories (which are true) how they beat an ollie etc., but Im just sayin high revvers fast off line have an engineering advantage due to laws of physice even though either can still be built up to beat the other if money is no object. If you really wanna win, the more money you throw at it can make you win regardless if JD or Ollie but one has to stay in certain classes etc also. John T in Indiana retired engineer.
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