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Re: John T
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Posted by John T on February 12, 1999 at 06:48:38:
In Reply to: John T posted by Al on February 11, 1999 at 21:37:25:
Al, Your thinking on leverage is correct. Think of the tractor as a big teeter totter board with the rear axles being on the fulcrum pivot and a kid on each end. The farther the weight is located from either end of the rear axle centerline, the more leverage force it exerts. Therefore, the farther any weight to the rear, the more it wants to lift the front end therefore transferring more weight to the rear axles where you want it for traction. As Im sure youre more aware than me, maximun traction is to where all weight is transferred to rear axles with just enough on front to have enough friction to steer. You are absolutely right that the farther to front the more good weight does to hold down front because its farther away from fulcrum pivot point which is the rear axles. So, your thinking and intuition is 100% engineering right. Now, as far as location of weights, its back to the simple thing as max to the back which will allow front end to barely float and allow steering. Thats simple and its theory is always correct and unchanging. The trouble is, that each track and every pull is different as far as traction is concerned, therefore where that weight needs to be (as far as towards front or back) is always different. Where the difference comes in, is that you want maximum overall weight of course, but to hold front end down (if track is over lifting it) and say you still had 100 lbs to spare at scales, you want it as far to front because the farther to front the more the same weight holds the front end down as you already knew. The ideal situation would be one big slidable weight with the maximum scale allowance to where you could do a trial run then slide it back and forth just to where front end barely stayed down. So all these supposed tricks and best weight placement is really not rocket science, its just all as far back as possible to float front end but tractors with inherent light weight fronts, need more to front or as far as front to achieve same effect.
Now, drawbar placement. The engineering thing to consider (as Im sure again youre more aware than me) is to make the sleds drag force want to pull down on axle pivot point to increase downward force and traction. The best easy way to think about long versus short advantages is to over extend and go to the extreme locations to visualize. So, if the drawbar were 20 feet long, as soon as you experienced much sled resistance force, the tractor would tip up easily too high and no steering. But if sled were hitched immediately above axles (zero drawbar length) its pulling resistance pulls straight down on axle helping with traction more instead of just lifting front end off ground. As you also know already and rules limit, the higher the drawbar the better for the same reasons. I have pulled some antiques over the years but never spent the money to be real good at it, but this theory is not really rocket science and any pullers alrerady know it even though they may not technically understand why. Max weight to rear just floating front end and high close drawbar as you already knew is bottom line. Youve already read my theory of needing max ground speed early in pull to build kinetic energy ( 1/2 Mass x Velocity Squared) is a winner and max traction friction is just before where you spin out wheels. JD's still have to overcome the disadvantage (in a progressive weight pull), being high torque low rpm, of the faster off the line screamin Ollies which get early ground speed and store more sled energy, but in a dead lug non progressive weight pull, they (JD) win. Now, when I get ready to soup up my G, you owe me some practical tips, I swore I wasnt gonna pull again unless I was serious and could be competitive. Good Luck. John T in Indiana jmn50@msn.com
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