The ‘Nimble’ T-6

By Staff
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A belt-driven automotive air-conditioning compressor provides compressed air for the air cylinders.
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A belt-driven automotive air-conditioning compressor provides compressed air for the air cylinders.

Dick and Ann Holcombe and the T-6. After 66 years of marriage,
Ann still puts up with Dick’s mechanical experiments. The T-6,
serial number 39517, is of circa 1952 vintage.

With the seat folded up the air tank, air cylinders, control
valves and plumbing for Dick’s air-assisted steering are
clearly visible. Dick’s biggest challenge was making air valves
that would pull the levers back quickly while also allowing the
levers to return to their normal position rapidly.

One day in 1924 I watched a red hit-and-miss engine being
unloaded from a Lehigh Valley freight car at the Dushore (Pa.)
railroad station. From that time on I had an almost uncontrollable
desire to acquaint myself with anything that had wheels and ran on
gas.

Crawlers have played an important role in my life, and over the
years I’ve had a number of different units. My first bulldozer
was a Caterpillar D2, followed by a Caterpillar RD7, an OC3 Oliver,
a TD-14 International and then a T-4 International.

I had some land in Sullivan County, Pa., that had the promise of
a lake site. With the help of our county agent we laid out a dam
and started construction. I hired a man with a new D4 Cat to do the
main breastwork, and after finishing the drainpipe and spillway we
filled the lake. The 16 acres the water would cover was swamp,
brush and trees. After a winter of extreme cold, with ice 24 inches
thick, we drained the lake and the job of clearing and grading
began.

The D2 was the first bulldozer to be put to work, and after a
short time I decided a larger tractor would be necessary. My
financial situation at the time precluded a more modern tractor and
I had to settle for the ancient RD7 Cat, a model designation
introduced in 1936. For the next three years clearing and grading
took place on a schedule of convenience, with the RD7 being retired
and the TD-14 doing the heavy work. I then acquired the T-4
International, and with the engine overhauled and new pins and
bushings installed the T-4 became my only crawler tractor.

The Next Chapter

The small pedals now control steering on Dick’s T-6. Close
examination reveals cables running through pulleys from the
hand-clutch lever to the brake pedal. A light touch on either pedal
makes an air cylinder pull on its respective lever, which in turn
pulls on its respective brake, making the T-6 turn.

Fifty years passed. The lake had been sold, but the T-4 was
still in my possession. At the age of 85 I decided that the
gymnastics of getting on and off the T-4 were getting to be a
chore, and after a fellow offered me a price I couldn’t turn
down I sold it. For the first time in nearly 50 years, I was
without a crawler.

About two years ago a casual friend of mine asked if I would
take a look at a tractor he had acquired, as he needed some advice
on making it work. It was a T-6 International with a Drott bucket
and bulldozer blade. The engine was stuck and the steering clutch
cavities were full of water. The street grousers were smooth and
the track pins and bushings were worn through. I told him it would
be a very expensive job to put it in shape and he decided to just
let it sit.

Time passed, and my friend passed away. One morning his widow
called, and she offered me the T-6 if I would take it away. The
starting of the engine and the refurbishing of the steering
clutches is a story in itself, but we managed to get it on a lowboy
and delivered to my place.

A common method of steering a crawler tractor at the time was to
pull back the hand steering clutch lever and apply the foot
steering brake, thus making the tractor pivot on the disengaged
track. Now, these levers are unassisted, mechanical devices
requiring a fair amount of pull to engage. The T-6 book calls for a
maximum pull of 35 pounds on the steering clutch hand lever. Now,
that was okay when the machine was used for plowing, but when it
was used as a bulldozer or loader, it took a lot of pulling – a lot
more than an overweight, underpowered 87-year-old could muster.
‘There has got to be a better way,’ 1 thought to
myself.

My T-4 had linkage between the hand clutch levers and the
steering brakes for turning, so why not rig a cable from the
steering hand lever to the brake pedal of the T-6 and achieve the
same results? I tried it and it worked, but the pull on the levers
was more than 1 could manage.

I have some experience with air cylinders, and recognizing the
universal use of air in braking systems on trucks I thought why not
steer the tractor with air. With considerable trial and error I
came up with the following scenario.

The tractor’s original gas tank was rusted, so I discarded
it and mounted a smaller gas tank to the right of the
operator’s seat. I then mounted a used air-conditioning
compressor on the left side of the engine, and via v-belts and an
electric clutch I had compressed air. I used a three-gallon tank
for air storage and mounted two 6-inch diameter pull-type air
cylinders under the seat, attached via cables to the steering
clutch handles. 1 then made two air valves from 3/8-inch air
quick-couplers and connected these to two small foot pedals
convenient to the operator. Sounds simple, but it took a lot of
bench testing and valve size manipulation to finally achieve quick
operating response.

The day of testing was wet and the tracks were soon a mass of
mud, but the response was great. Light pressure on the foot pedals
swung the machine right or left, and, if such a term could be
applied, the T-6 was actually ‘nimble.’

The T-6 now rests on some land near my house. The worn out
tracks are covered with mud, and the machine’s generally shabby
paint and dents present a forlorn picture. The gas engine and the
drive train are in serviceable condition, but at my age ingress and
egress to the operator’s seat is a nightmare.

It is doubtful that my power steering experiment was unique. My
long life has been associated with many mechanical adventures, but
making a T-6 to be ‘nimble’ was worth the while.

Contact engine enthusiast Dick Holcombe at: P.O. Box 247,
Dushore, PA 18614; e-mail: dicke@chilitech.net

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