On this super single conversion, my advice is don't do it..I'll explain.
In 1969, I was regular army, and got assigned to an AMC (Army Materiels
Command back then) unit at Camp Pickett Va, for the very first testing of
super singles on 2 1/2 ton trucks. The agency responsible for the testing was
USA-GETA, Army Materiels Command, General Equipment Test Activity.
We took 12 brand new M35A2's and 12 driver/co-driver teams and laid out a
course of rough terrain testing more than 30 miles long. All the trucks
required modification of the hubs, which if I recall correctly involved
pressing in new lug studs, and moving the brake drums to the other side of the
hub flange. A drag link valve and tierod cylinder type power steering kit was
installed on each truck. Special pump kits were provided for installation on
the LDS465-2 multifuel engines. Wheels were supplied by each of six tire
manufacturers for this test. They were one piece drop center wheels, and the
radials were tubeless of course. Most of the tires resembled very closely
what we have today as super singles, with just a few tread patterns
differing radically.
The first results were inconclusive as far as tire suitability, mostly because
of the damage to the trucks. This damage was in several categories, as
follows:
*damage to hubs, bearings, and running gear due to the greater wheel offsets
toward the outside of the truck...the hubs were under-designed for the extra
loading.
*dramatic damage to the service brakes...several trucks experienced total and
explosive brake destruction in emergency stop situations. In several cases it
was necessary to change out entire bogey assemblies because of severe shrapnel
damage to the axle housings and brake assemblies.
*premature wear on all front axle steering parts, caused by the increased
mechanical advantage the wider tracked wheels had on the truck's front end.
Front end life was measured in weeks, not years! All trucks experienced bent
tierods, bent hubs, bearing failures, and steering gear damage. Dampers were
tried, with the result that several had their pistons pulled right out of
them. The rough terrain was just too much for the front end design.
*Collisions due to loss of control...two trucks were totally destroyed and
there was one fatality and two serious injuries after one truck lost control
on a rough downgrade and was unable to avoid the stopped truck in front of it.
This was attributed to inadequate brakes and a steering system "excursion"
from normal, probably caused by the front end forces over-riding the hydraulic
cylinder. The driver of the rear truck suffered a broken arm, chest injuries,
and facial injuries. His codriver was severely maimed when he attempted to
bail out, and was caught by the rear duals. The driver of the front truck
that was struck was killed instantly when his truck was pushed over the
embankment and a large tree limb penetrated the windshield frame and impaled
him.
This occurred at less than 30 mph..try to imagine this same thing happening at
highway speeds!
*Low speed rollovers were frequent, and it was established that the
construction of the much thinner radial sidewalls was lacking in enough
stability to permit operation at the edge of the truck's design limits...(an
M35 rolls easily to begin with) in sharp turns, rollovers were occurring at
less than 20 MPH. In several units that didn't actually roll, wheel damage
was observed from contact with the pavement after the sidewalls rolled under.
*Excessive body & frame wracking caused by uncontrolled wheel articulation way
beyond the truck's design limits. The combined wheel-tire weight at the
extended track widths were too much for the suspension.
*Torque rod failures were almost a daily thing...with pivot bearing failures
close behind.
The first year of testing was plagued by the above, at which point I retired
and handed the mess to someone else. Obviously, a lot of the problems were
resolved, because the singles eventually found their way to deployed units. I
am not sure how long this test was run, or how it turned out ultimately, but
the first year's results certainly give some food for thought. There are a LOT
of issues involved when you retrofit a vehicle
with equipment it was not designed for. As in a lot of DOD transactions,
sales pressure from manufacturer's reps seems to have a way of sweeping
serious problems under the rug, and field units often find themselves with
dangerous gear. This is my opinion, but there is enough data backing it up
that super singles perhaps have no place on large tacticals...at least not as
they were designed back in 1969.
Nick
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