Patent Prattles
An occasional Series on Morgan-related patents by John Merton
Bishop Cam Steering Box
Burman-Douglas Steering Box
Brooklands Steering Wheel
Tierod Ends
Easiclean
Wheels
Aero 8
Bishop Cam Steering Box
GB
223963 “Improvements
in or relating to gearing for steering mechanically-propelled vehicles and for
other purposes”
This,
a patent for a steering box, was applied for on July 25 1923 and
has a publication date of 27 October 1924.
The patent holder was Reginald Bishop, a Middlesex engineer, for a device
operationally consisting of a cam of helical form and constant diameter (at the
lower end of the inner steering column) imparting motion via a roller or peg
attached to a lever projecting from the steering rocker shaft.
Yes, it’s the old Bishop Cam steering box.
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Before
World War 2,most British cars were fitted with one of three proprietary steering
boxes, the Bishop Cam, the Burman-Douglas worm and nut, or the Marles.
Arguably, the Bishop Cam was the most basic (a polite word for crude). It
was fitted to Morrises and MG’s among others, and has long been
cursed by T-series MG owners
for its wooliness and vagueness. Around
1937, Vauxhall actually abandoned it, choosing instead the Burman-Douglas.
Well,
from the 1954 season (and possibly a few cars before), Morgan switched from the
Burman-Douglas to a “new” Cam Gears steering box, which continued in use for
quite a few years until the advent of the Gemmer and Jack Knight rack and pinion
systems. Simply, the Cam Gears box is the Bishop Cam box made by Cam Gears Ltd,
or, after a 1965 takeover, TRW Cam Gears Ltd.
The Morgan factory at one stage marketed a conversion kit to fit this
device to earlier cars.
If
you look hard at your Cam Gears box you may find “BISHOPS GEAR “ and the
patent number etched on the top cover or cast into the left hand side housing.
In
detailing the three boxes, the “Service Station and Motor Mechanics’
Manual” (1940) implies that the
Burman worm and nut box is much superior to the Bishop Cam, a feeling reflected
by some Austin A30 owners also (the A30 also changed to Cam Gears in the early
1950’s).
So,
why did Morgan switch to a technically inferior product dating back to the
1920’s? This is largely
speculation, but the Cam gears box is simpler, cruder, and presumably and
importantly cheaper. Also, post-war
Burman worm and nut boxes were of appalling quality, and arguably much worse
than their pre-war counterparts.
However,
“Spin Doctoring” was in vogue even then.
Both the “Autocar” and “Autosport” tests of May and August 1954
talk somewhat eulogistically of the new “cam and lever” steering box, and
Harvey, in “Morgan: the Last Survivor” talks of replacement of the “old
Burman worm and nut steering box which had survived since pre-war days, with a
more sophisticated Cam Gears cam and peg system…”
Oh dear!
(Special
thanks to Laurie Burton for retrieving his old Cam Gears box for a look-see)
Burman-Douglas Steering Box
GB
361204 (US 1893764) “Improvements
in or Relating to Steering Gear”
A
sports commentator and noted tautologist once spoke of a player making
“forward progress”. This
story’s a bit like making progress by going backwards, and gives a glimpse
into spin-doctoring as practised in the middle of last century.
Previously,
we’ve examined how, from around 1954 Morgan adopted a Bishop Cam steering gear
provided by Cam Gears Ltd., and made to a 1924 patent.
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Our
current Prattle covers the Burman-Douglas worm and nut steering box, used in
Morgan 4-wheelers from 1936 to 1954 (a few very early cars used a reduction gear
mounted halfway down the column). The
patent for it (GB 361204) was filed on 16 September 1931 and published in
January 1933. That’s 9 years
after the steering box Morgan adopted later!
The Burman-Douglas is the more sophisticated and complex design, and our
motoring forbears seem to have thought it was a lot better - until they moved
backwards to the Bishop Cam, that is…
The
“Service Station and Motor Mechanics’ Manual” (1941), in a treatise
covering Bishop Cam, Marles (later Marles-Weller) and Burman-Douglas designs
comments:
“The
Burman-Douglas steering gear … is looked upon by experts
as
being one of the most perfect types of steering gear in existence. As an outstanding indication of its efficiency, it may be
quoted that it was the steering gear used by Sir Malcolm Campbell in his
“Bluebird” when he established the world’s land record of over 300 miles
per hour.
The
Burman-Douglas gear was designed by a British engineer who had had long
experience of the manufacture and use of steering gears of many different
types…”
The
patent holder was John George Douglas of Luton, Bedfordshire. The design was claimed as a refinement of earlier worm and
nut systems, in part to eliminate lost motion in them…
There
are some marked differences, however, between the manufactured box as we know it
and the patent specifications. The
most significant is that the production boxes have no adjustment for wear
(except for end-float in the column). The
patent does have provision for wear adjustment, the nut being split
circumferentially and longitudinally to permit wear to be taken up by tightening
screws accessible simply by removing caps in the box casing.
Also, as we know it, the nut is located and held in position as a sliding
fit inside the casing, wear here being another factor contributing to slop in
the system. In the Patent, the
inner column, and hence the nut, is located and held in place by a spigot on the
end plate at the bottom of the box.
But
then, in the convoluted logic of the afore-mentioned publication:
“…This
tremendous bearing area between the main nut and inner column gives an obvious
tendency toward long life. So great
is this contact area, that the maximum load and speed can never break down the
oil film.”
Later,
however, the article goes into some detail about procedures to be
followed when wear takes place between the nut and inner column…
So,
why was the Burman-Douglas box dropped from 1954 for what publicists then
claimed was an improved and more sophisticated product?
As far as I can glean, Morgan’s spin was that the post-war Burman-Douglas
boxes were of appalling quality (they were right!).
But perhaps there’s a bit more to it than this.
The replacement Cam Gears box is a cruder and simpler device - perhaps it
was cheaper to buy. Then, too, the
Austin A30 made the same move at about the same time, suggesting there may have
been a problem with continuing supplies (some
A30 owners consider the Burman the better box).
After World War 11, the Burman Gear Co was supplying the industry with
larger and more sophisticated recirculating ball designs - perhaps they deemed
it uneconomic to continue production of the older worm and nut devices?
Brooklands Steering Wheel
GB
377440 “Improvements
relating to Hand Steering Wheels of Motor Vehicles, Aircraft, Motor-boats and
the like”
Do
you have a Bluemel’s “Brooklands” steering wheel on your Morgan?
Perhaps you’re extra lucky and have a pre-war 4-4, or one of a few
post-war Series 1’s, with an Ashby wheel?
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The
wheels (which are virtually identical) have four spokes, each consisting of five
spring steel spokes held apart by a spacer a few inches out from the centre
boss. The boss itself is in two
pieces – the spokes are clamped between each piece, which is held together by
four one quarter inch BSF nuts and bolts.
Well,
the patent holder was Frank Ashby and Sons, a small Birmingham manufacturer
(they also made rear luggage racks for some Morris models).
The application date was August 1931, the acceptance date July 28, 1932.
The
aim of the design was to improve flexibility and cushioning from road shock
without loss of steering feel or control.
You
may find the patent number on the rear of the boss of the Ashby wheel.
If you can find a pre-war MG with an original Bluemel’s
“Brooklands” wheel, look for the number on one of the spoke spacers.
And, yes, the Bluemel’s “Brooklands” is an “imitation” –
actually a copy of the Ashby wheel and made to Ashby’s patent.
Tierod
Ends
1.
GB289272 “Improvements in or
relating to the steering mechanism of motor or other vehicles”.
Remember
the fabled “Morplane” hoax? This
is the patent number used, albeit with a “/4” added to it. Such a number never officially existed. of course, but the
number without the “/” does.
It’s
for the unique tie-rod ends used on three-wheelers and four wheelers from the
late 1920’s until the advent of the Plus 4.
These consist of a conical bronze bush which is a tight fit on the
attaching bolt. The bush rides in a
tapered hole in the end of the tie-rod, the system being tensioned by a coil
spring under the head of the bolt (or its nut) effectively drawing the bush
further into the taper as wear takes place.
The system aimed at eliminating wheel wobble.
The
patent applicant was Henry Frederick Stanley Morgan, Morgan Motor Company Ltd.
Application date for the patent was June 1927, with acceptance completed
on April 26, 1928.
By
the way, movement takes place between the outside of the bush and the tie-rod
end, not between the inside of the bush and the bolt.
Thus the “dodge” in some of the workshop manuals of internally
drilling the bolt to allow grease to be pumped inside the bush, obviating the
need to dismantle the system for lubrication, is a nonsense.
Easiclean
Whee
ls
GB
456866 “Improvements in
and relating to Vehicle Wheels”
You’ll
find this number on the 17” Easiclean wheels fitted to most Series 1’s from
around 1938 or so. It’s
adjacent to one of the hubcap retention knobs.
It’s
actually got much broader applicability than just Morgans (read on), and is not
tied to the Easiclean wheel per se.
It’s
the system for clipping on the hubcap over fixed knobs or fixed raised points on
the wheel, relying on the spring of the hubcap itself to do the job.
Other ways of fixing have included spring-loaded knobs, like the
round-backed Mercedes of the ‘50’s and early ‘60’s, and attaching via a
centre screw. On earlier 4-4
Morgans, the hubcaps were attached by a centre spinner (a hexagon bolt on some
very early cars), which screwed into the hub, doubling as the dust cap.
The
British patent was applied for in February 1936, and accepted on November 17,
1936. It was granted to a German
national, Paul Lemmerz, and followed earlier German patents.
Incidentally, there were at least five different types of Easiclean wheels used on Series 1 Morgans, some with centre-fixed hubcaps rather than the clip-on type. It is not known whether all these were factory-fitted.
4
Aero 8
6
GB
2359528 “Chassis Structure
for a Land Vehicle”
Well,
if you wanted to know about the new Aero 8 chassis, this is the patent for it.
It consists of two interconnected sections (a front and a back), the
outer parts held together by fasteners designed to break on impact, allowing the
two portions to slide relative to each other. The patent also incorporates a
spring/damper assembly unit, the top connection of which appears to be attached
to the inner pivot rod for the upper of the two wishbones.
The
applicant for the patent was the Morgan Motor Company, the inventors listed as
Christopher John Lawrence and Charles Peter Henry Morgan.
Publication date of the patent is 29 August 2001.
Interestingly, the Morgan company also holds a parallel patent in
Germany, DE10108034, for this chassis/suspension set-up.