What was the reasoning to go from direct drive to the torque converter drive? Why the diesel fuel in the torque converter?
Yair . . . OldRedFord. I can't help with any precise technical/engineering answers to either question but I believe the fuel converters were just another step along the evolution of power transmission. They never worked well on Cats and, at twelve hundred they were doughy bastards at best . . . in an Allis Chalmers at twenty one hundred they were a different beast and performed very well. As I understand it the theory was that the tractor would always move the load at the fastest possible speed. An Allis HD21 which had a two speed stick shift behind the converter had the capability of going from track spin to around (I think) four mph in first gear and from track stall to seven or eight mph in second. I could be a bit out with the numbers but I have many thousands of hours on the Allis's and they were the top performer of their era. I never did quite understand using the fuel as the power transfer medium but suspect it had something to do with heat dissipation . . . the last Allis's before they went to powershift had a standard oil converter. Cheers.
The first torque convertors were installed in modified Cat D8s by Peterson Cat, a California dealer. Buster Peterson is the inventor of many Cat improvements. Lots of them were picked up by the factory later on production machines. They were installed to use on push Cats for loading Cat cable scrapers. It always kept the puch cat matched to the scraper. Wasn't long before Cat came out with the diesel fuel convertor and then on to the oil filled ones. If I remember correct the fuel ones should drip 9(?) drops a minute. Or is it 7? The torque convertors were a huge improvement when used in the push cats.
Yair . . . Spot on old-iron-habit ! Yeh, I remember counting drips now. They had carbon seals and a certain flow I suppose was needed for lubrication. . . I seem to remember a special grease as well . . . was there a zerk in there somewhere? Those same characteristics that made the torque converter tractors good for pushing scrapers made them ideal for our application in the scrub. Cheers.
A story told to me by my late friend Jim Hamill. His father Archie worked for George M. Brewster & Son in Brewster's central shop in Bogota, NJ. Brewster's equipment manager Art De Braun, a mad scientist and mechanical genius, takes Archie and two other mechanics into the rebuild shop and shows him a brand new D8 14A without the blade attached and tell him to do the following: a) remove the transmission b) remove the left and right tracks and track frames c) build a frame to support the front of the tractor, when you are done come get me. They got Art and he shows them a HD-20 torque convertor and explains he wants them to install it between the master clutch and the transmission. Turned out not to be as simple as Art thought. It involved cutting and sectioning the frame for the needed space, altering the track frames and the blade push arms and maintaining the balance of the machine. They spent January, February and part od April of 1955? in surgery and had a working machine in the spring, just in time for Caterpillar to introduce the new D8 with a torque convertor. Brewster had made many modification to different equipment, lengthening carbodys on Manitowoc and Bucyrus Erie draglines, added a BE churn drill rocker arm assembly on Manitowoc and BE pile rigs to operate the sand drain rigs as drop hammers, no compressor needed.
I have some experience running both a D8H and a D8G torque converter drive and my boss who owns both swears the G pushes harder then the H. I do know the tracks are half as good on the H as the G.
Good post Roger, Didn't know the tc was a Peterson idea. What a savy bunch!
I'm probably way to young to be commenting here but my guess on the diesel converter would be that the medium is constantly being used up and replenished. Oil technology in those days not being what it is today, I suspect the heat added by the converter would have tended to make the machine's lube oil deteriorate too quickly. You guys tell me if I am all wet here.
I don't know if they had special greese or not. I never run one in the day, only drooled over the pictures and an article I read about them back then. I did get to backfill behind a dragline with a well kept original one for a bit at a show about three yeras ago. I enjoyed the experiance. It was actually a sweet, powerful machine to run when comparing to my dry clutch 2U-D8 which is also in decent shape.
I guess the idea for torque converter drive was smoothness of operation. Especially for things that required coordination with other machines, like pushcat as the others mentioned above. I don't know why they used a fuel fed converter, I do know that Manitowoc cranes used them too. Maybe other makes, too, but I'm not sure. One advantage I can think of about a fuel fed converter is that if you run out of converter fluid, (AKA diesel fuel) the machine is not going to run anyway, preventing converter damage.
Smoothness is a big thing, but from the manufacturer's point of view, you can also use a much smaller engine in terms of weight and torque with supposedly the same pushing ability.