Chain Length Differences

[Kelly N]

I pride myself on being for the most part "country smart" so I want an honest explanation to the effect of drawbar chain length when pulling. In my estimation, the shorter the chain(using the same hitch point location and height), the more weight of the sled the tractor tries to carry and not drag. This to me tells me that it would be easier to pull farther. Am I wrong???

 

[88-1175]

correct

 

[north puller]

The shorter chain has a steeper, more vertical angle. The tractor has more "lift" on the front of the pan, and the pan therefore puts more weight onto the back of the tractor. This helps with traction, but will cause you to use more power with your new found traction.

There are only three options to a pull: you run out of traction, you run out of power, or you full pull. A shorter chain will give you more traction.

 

[bgreer75]

If you want to calculate it and know the force in the chain you can break the force into its two vectors...

Sin of the angle of chain to ground times force in chain is down force on drawbar.

Cos of the angle of chain to ground times force in chain is the forward motion force.

When the front end of the tractor comes up, the drawbar lowers cause the angle to decrease which changes the two force vectors.

Most classes run a 20" drawbar so that is easy but the chain length and the tie point of chain to sled changes so make sure you measure that for accurate calculations.

Hope this helps....Brian

 

[Massey 101]

The missing link to chain length is the hook itself, seen all types over the years! Sometimes the man that hooks it to your tractor may have it twisted making it shorter!
The best way to beat chain worries, is keep a log on how you performed on that sled the last time you pulled...

 

[showcrop]

You want to pay attention when the new weight class starts. I was nearby as a friend backed up to the sled and we watched the operator raise the hitch point about three inches. As I walked to the back of my friends tractor he jumped off and I asked him how many.

 

[PopinJohn]

When talking about force in the chain, do you mean drawbar pull? Expressed how?
How can that number be determined without a strain gauge?
Just curious.

 

[bgreer75]

Force in the chain.....this would either have to be down with a load cell within chain or even something simple like a hydraulic cylinder and a pressure gauge. If you do cylinder method take psi times surface area of piston (Dont forget to subtract rod surface area)

I have pulled on a sled before with a load cell in the chain....they had it broadcasted to a laptop on sideline where you could watch.

I have also bonded strain gauges in the hitch before (back when I manage a R & D lab and had access to that stuff)..... this only yield force in forward motion but you could also install in down force too. You can also buy premade load cell pins and even load cell washers if you want to get creative....

I think it is neat to actually calculate how forces change when your tires dig down which basically lowers your drawbar.