California Antique Farm Equipment Show 2014

[Gil]

Hi Bill,

Nice coverage of the show and thanks for posting.

My attention was focused on the "power steering" on the Caterpillar. The operator had to be "powerful enough" to steer the thing. This is before they designed in differential tread movement to steer the beast. This brings up an interesting question - when did differential steering become standard on Caterpillar tractors? Was this a development borrowed from the military (tanks)?

-Gil

[whulsey]

Differential steering (if we're talking about the same thing) I thing was first used by Cat in the late 70's-early 80's. Before that it was basically a clutch and brake setup were power was cut to one track and it was braked so the machine rotated around it. On the early on shown it was an actually front wheel (even if it is fairly large) that was turned by the steering wheel (lots of Armstrong steering and some gear reduction) there. Its getting past bedtime so will dig through some of my Cat books to see if I can find a bit more info later.

Wayne, but I answer to about anything especially if its a call to dinner.

Hey Don, that little Seven is a cutie isn't it?

[whulsey]

Did some digging and couldn't find any definite dates. But here's a couple of comments from the crawler section of the Yesterday Tractors Forum that talk about the steering systems.

Most have clutches and brakes on each side and a solid bevelgear shaft driving the clutches, no diff. Some have levers for the clutch control and pedals for the brake control. Others may have only levers or only peddals. These types usually have the first part of the travel to release the clutch and the last of the travel to put on the brake. Some old IHC tractors used a set of planetaries some times two on each side instead of clutches. They had a big brake disc that a caliper held for the planetary to drive and let go of it to not drive. The also had a brake on each side too. The Struck mini dozed kit uses V belts you tension to drive on each side for F & R you might want to build something like that.

Most older dozers use a clutch and brake system for each track... The clutch disengages power to the track for gradual turns, applying the brake causes a sharper turn. This system works because there is no differential between the tracks. Some newer ones use one lever or pedal for both functions (JD 450). The first part of lever or pedal travel releases the clutch, moving it further applies the brake. Another system is the controlled differential, it uses a brake on each side to cause power transfer to the opposite track thereby slowing one track down and speeding up the other. This system is widely used on military tracked vehicles, and some dozers. Oliver (Cletrac) used a controlled differential on the HG/OC-3 and maybe others. Caterpillar has also offered differential steering. Most new machines have gone to hydrostatic drive, where a variable speed hydraulic motor is used to drive each track. This system is very nice... until it breaks, then you need a fat wallet!

From Farm Collector Magazine:
The Cleveland Tractor Company began in 1911, when Rollin H. White, with the help of his brother Clarence, worked to develop a farm tractor. White already had a successful steam car, as well as a line of both steam and gasoline powered trucks on the market.
After trying several unsatisfactory wheeled tractor designs, White came up with a promising crawler design, featuring his patented Controlled Differential Steering mechanism, which was used, with many improvements, until Oliver ended crawler tractor production in 1965.
Read more: Oliver Cletrac HG and OC-3 - Looking Back - Farm Collector

So it looks like Rollin White developed it and used it in on the Clectrac's who sold a lot of stuff to the military.


And if you want to geek out even more here's a discussion that also brings up that the diff system was invented by C.L. Best and bought my White before the Best-Holt merger created Caterpillar Corp. I love this stuff (probably why I don't ever get anything finished).

http://www.practicalmachinist.com/vb...64/index3.html

[WVA]

Nice piece of enlightenment on crawlers! I know from some experience in the 50's with a D-8 and a TD-18, about the lever and brake arrangement. An interesting note is that if there is no load,and you are going downhill, the steering can be the reverse....with no brake on the unclutched side, the track freewheels, and the tractor turns in the other direction! It is so common to hit the brake that it seldom happens. The WWII MG-1 and MG-2, (Cletrac) high speed tractors used on airfields had differential drive. Jim

[Gil]

Hi Bill,

Read the Wikipedia entry on Carterpillar - found out the British used them to haul artillery around in WWI and more or less copied the design for their first tanks - a surprise.

The clutch/brake system has worked well as tracked vehicles are more or less point and proceed type vehicles.

Liked @WVA's reference on downhill control reversal - one of those "whooda thunkits"...,

You're right about this bringing up a #10 can of worms though...,

-Gil