Introduction To Jowett Cars Ltd – Hardware System
A vehicle manufactured by Jowett Cars Limited (JCL) was assembled
using hardware to hold components together. In modern times, the motor industry
tends to use the term 'fasteners', which probably originated in the USA. The term 'hardware' refers to such items as bolts, setscrews, machine screws, grub
screws, nuts of all types, plain washers, spring washers, internal teeth
washers, drive keys, mills pins, cotter pins, split pins, dowels and circlips –
to name just a few.
With respect to the post WW2 Jowetts, virtually all threads were of
the British Standard Fine (BSF) type. The other thread adopted by Jowett Cars
Limited was the British Association (BA) thread for hardware of a lesser thread
diameter than ¼". The best known alternative threads were British Standard
Whitworth (BSW), and the Unified National Fine (UNF) that had been adopted by
the North American Society of Automotive Engineers (SAE). Hence the description
of a piece of hardware being described as SAE-UNF. There is also a Unified
National Coarse (UNC) thread that was adopted by the SAE.
Non Standard Hardware
Jowett vehicles, in taking components from outside suppliers, did
use some items of hardware of the SAE format. Because Britain had made the
decision to adopt the SAE system for its motor industry, no doubt influenced by
the local Ford and Vauxhall (GM) companies taking large numbers of components
from the specialist industry. For a time, in the early 1950s, there was a
fairly confusing mixture of the two basic types of threaded hardware – today
there is an even worse situation with respect to the SAE and metric systems,
where confusion now reigns supreme!
We now have the situation where a UNF threaded setscrew or bolt,
with metric across the flats head dimension, is supplied in sealed packaging
along with a nut that conforms to the SAE across the flats dimension for the
nut size. A poor mechanic, working on a SAE equipped vehicle, replacing bolts
may need metric spanners as well.
Bring back Dr Frederick Lanchester LL.D., F.R.S. please!
JCL did use threaded hardware of the BSW format, as they did the SAE
formats. Set out below is a list of known non-BSF threaded hardware:
British Standard Whitworth – exhaust flange joint, brass mudguard
setscrews and nuts (Jupiter). Another use of the Whitworth thread form was in
the Javelin/Jupiter flywheel. Two 3/8" BSW threads have been provided for
push-off jacking setscrews for flywheel removal from the crankshaft. It is very
likely that BSW was used here because, traditionally BSW setscrews were made
from mild steel, and therefore would not have damaged the surface of the rear
face of the crankshaft.
SAE Unified National Coarse – fan belt adjuster lug on dynamo,
inside starter motor and dynamo (Lucas).
SAE Unified National Fine – full hydraulic brake system wheel
cylinders, rear axle components and dynamo pulley
This use of non-standard hardware, was, while the vehicles were in
their early operational life, easily handled by the average trained mechanic.
It was when the vehicles came to be serviced and/or repaired by unknowing
novices, that serious problems arose. A very good example was the forcing-on of
a BSF nut onto a UNF thread on a wheel cylinder mounting stud. It could be
fairly easily forced, and once in place in a dry condition, due to the forced
conforming of the thread types, became very prone to severe rust corrosion.
This condition would, in most instances, cause the stud to shear off flush with
the wheel cylinder housing – rendering it useless and most probably, scrapped.
Our loss!
The Jowett Hardware Part Numbering System
JCL introduced, with the release of the Jowett Javelin, a code
system to identify hardware type by its given part number. There is a code
system for all standard nuts, bolts, setscrews, machine screws and threaded
studs. The system code can be quite easily opened up to inform of the component
of hardware's specification. Part numbers allocated can be analysed as follows
under separate headings.
Overall, the Jowett system is a very good system, once the system
becomes clearer. It can never become totally clear because a number of
anomalies crept in. For instance, special nuts, for example the ⅜" self locking Simmons nut at
the water pump pulley – this item has been allocated a Jowett five digit part
number commencing with '5'. This is very strange as it could have so easily
been absorbed into the hardware part numbering system. Another anomaly is the
absence of listed hardware items in the spare parts catalogues. There must have
been a listing somewhere in the service system so that dealer parts departments
could order standard items. Or did dealer workshops purchase hardware items
locally?
Research into this article has revealed some miss-prints that have
carried through all Javelin Spare Parts Catalogues. For example, the
castellated (slotted) nut that secures the steering arms to the stub axles is
in fact ⅝" BSF, not ½" BSF as shown.
In addition, some strange changes to the part numbering and
identification system did occur. For example, one of the bolts securing the
Javelin steering column to the steering box is listed as, Part Number
FB604/10A, and identified as a setscrew. Its fellow bolts are shown as
FB604/7A, and are listed as being setscrews as well. A steering column would
have to be dismantled to attempt working the reasoning behind the bolt code and
the 'A' suffixes.
With respect to threaded studs, some have three different part
numbers for identical components, in the same applications over the
manufacturing period..
Bolts
Jowett Part
Number FB105/8
In this instance the part number may be broken-down:
F = British Standard Fine (BSF) Thread
B = Bolt, with Shank
1 = Hexagonal Head
05 = Bolt Diameter, 5/16"
(Code is shank diameter in 1/16" increments)
/ = Intermission before Bolt Length
8
= Length of bolt from under head to end of thread (Multiples of 1/8")
Thus Part Number FB105/8 identifies a 5/16" x 1" BSF Bolt.
It should be noted that all Jowett installed BSF bolts and setscrews
are of the high-tensile type. A bolt removed from a car that is of BSF thread
and has raised relief markings on its head, is a high-tensile bolt. Any bolt,
with few exceptions, that has a plain unmarked head must be considered to be of
mild steel or similar material. The exceptions are bolts such as flywheel
retention bolts, big end cap bolts, front spring arm pin and front brake back
plate bolts. These are bolts that were manufactured by Jowett, are high-tensile
and have no (or minimal) head markings. These bolts can be identified by their
five digit Jowett part numbers that commence with a five, or a 'J' (5 or J5).
Setscrews (Hexagonal Head)
Jowett Part
Number FS105/8
In this instance the part number may be broken-down:
F = British Standard Fine (BSF) Thread
S = Setscrew, with Full Thread
1 = Hexagonal Head
05 = Bolt Diameter, 5/16"
(Code is shank diameter in 1/16" increments)
/ = Intermission before Setscrew Length
8 = Length of setscrew from under head to end
of
thread (Multiples of 1/8" [0.125"])
Thus Part Number FS105/8 identifies a 5/16" x 1" BSF
Setscrew.
Machine Screws (Round Head – Screwdriver Slot)
Jowett Part
Number FS504/4
In this instance the part number may be broken-down:
F = British Standard Fine (BSF) Thread
S = Setscrew, with Full Thread
5 = Round Head
04 = Screw Diameter, 1/4" (Code is shank
diameter in 1/16" increments)
/ = Intermission before screw Length
4
= Length of screw from under head to end of thread (Multiples of 1/8"
[0.125"])
Thus Part Number FS105/8 identifies a 1/4" x 1/2" BSF
Machine Screw.
Nuts
Jowett Part
Number FN105/K
In this instance the part number may be broken-down:
F = British Standard Fine (BSF) Thread
N = Nut
1 = Standard Thickness Nut
05 = Nut Thread Diameter, 5/16" (Code is
shank diameter in 1/16" increments)
/ = Intermission
K
= Steel
Thus Part Number FN105/8 identifies a 5/16" BSF Nut (Standard
thickness).
Studs
Jowett Part
Number FD105/8
In this instance the part number may be broken-down:
F = British Standard Fine (BSF) Thread
D = Stud
1 = Standard Thread Proportion
05 = Stud Thread Diameter, 5/16" (Code is
shank diameter in 1/16" increments)
/ = Intermission
8
= Stud Length
