Chain length.
Hi, Firetrack.
Welkum too ther 4um. Good to have some-one else here who's done a bit of chaining.
I too did a bit chaining in my mis-spent youth. Everything from mallee and sand plain scrub to tall timber with everything from D4's to D8's. I never did get to use a ball 'cos by the time I started doing it, folks had woken up that the ball snapped a lot of trees off instead of pulling them out of the ground.
We used to work our chain length on the basis of the width of cut we could handle plus an extra 100 feet for each tractor. When using 2 x 270 hp D8's pulling mallee or scrub country, we would be cutting anything up to 400 feet wide which would see us using 600 feet or a bit more of 2 1/2" chain. We found that anything much under that 100 feet of chain for each tractor over and above the cut would see D. R. Sends being pulled sideways and we had to work more on the steering clutches and brakes to stay on course. Not a good look, especially when you can't see your buddy 400 feet away through the bush and you're relying on the hang of the chain to tell you how well you're keeping pace with him and roughly how your cut width is going.
We often tied long sticks to the front canopy legs with rag flags on the tops to help us keep track of each other in the scrub - didn't always work. Then we'd go into a heavy timber job where we were only 30 - 50 feet apart and could see each other most of the time. Sure made a change. We shortened the chain for those jobs, down to maybe 300 feet.
With those 2 x D8H's and 600 feet of chain, we took down 6,000 acres in 5 x 13 hour days on one job, 1,200 acres a day, nearly 100 acres an hour. That's fairly cheap clearing, especially when the farmer can put a running fire over it and then plough it without raking. Cutter bars were pretty much unknown in those days, mid-1960's to early 1970's.
Ah, those were the days. LOL.