| Description | Date | Identifier | |
| Graphs of road spring tests showing deflection vs applied load for a standard front spring after 3.5 years of service. | 18th Aug 1928 | Box 52 \ 2 Scan183 | |
| Graphical report on road spring tests after cleaning and lubrication. | 18th Aug 1928 | Box 52 \ 2 Scan184 | |
| Graph showing three tests on a cadmium plated and lubricated front road spring. | 14th Mar 1928 | Box 52 \ 2 Scan185 | |
| Graphs showing the results of three tests on a cadmium-plated front spring after a 4000-mile road test. | 12th Sep 1928 | Box 52 \ 2 Scan186 | |
| Blueprint comparing two different leaf spring designs, Firths and Woodhead. | 25th Oct 1928 | Box 52 \ 2 Scan187 | |
| Comparison of Woodhead and Firths rear road springs under a 1700 lbs load. | 25th Oct 1928 | Box 52 \ 2 Scan188 | |
| Summary comparing the life and performance of four different types of American springs ('A', 'B', 'C', and 'D'). | 16th Oct 1928 | Box 52 \ 2 Scan189 | |
| Summary table of bump test results for six different springs. | 30th Aug 1929 | Box 52 \ 2 Scan190 | |
| The material and heat treatment for 'R' Engine connecting rod bolts. | 30th Aug 1929 | Box 52 \ 2 Scan191 | |
| The high cost of Firth's Staybrite Steel and an instance of being overcharged for strip material. | 31th Dec 1929 | Box 52 \ 2 Scan192 | |
| Letter from a supplier regarding an inability to fit clips on 40/50 HP springs as per the standard, proposing an alternative solution. | 10th Jan 1930 | Box 52 \ 2 Scan193 | |
| Issues with Messrs. Firths' spring drawing, specifically concerning the front and rear springs. | 14th Jan 1930 | Box 52 \ 2 Scan194 | |
| Letter to a supplier regarding design specifications for Special Experimental Phantom II rear springs. | 16th Jan 1930 | Box 52 \ 2 Scan195 | |
| Blueprint for special front and rear road springs for chassis No 23 EX. | 10th Jan 1930 | Box 52 \ 2 Scan196 | |
| Letter from supplier Thos Firth & Sons regarding experimental rear road springs for a Phantom 1 Sports Chassis. | 20th Jan 1930 | Box 52 \ 2 Scan197 | |
| Letter from Thos Firth & Sons regarding the supply of rear road springs for a Sports Chassis. | 21th Jan 1930 | Box 52 \ 2 Scan198 | |
| Letter to a supplier regarding the redesign of overweight springs for a Phantom II. | 21th Jan 1930 | Box 52 \ 2 Scan199 | |
| Letter regarding the use of a spring in production and a request to prepare dies for rolling top plates. | 22th Jan 1930 | Box 52 \ 2 Scan200 | |
| Covering letter attaching a query from Thos. Firth & Sons about rear axle springs for Chassis 23-EX. | 22th Jan 1930 | Box 52 \ 2 Scan201 | |
| Discussions on the proportions of axle springs for model 23-EX with Firth's spring designer. | 22th Jan 1930 | Box 52 \ 2 Scan202 | |
| Telephone call memo from Thos. Firth & Sons Ltd. regarding the suitability of a drawing for the rear springs of Sports Car No. 23 EX. | 22th Jan 1930 | Box 52 \ 2 Scan203 | |
| Note recording a telephone call from Thos. Firth & Sons regarding springs for Sports Car No. 23 EX. | 23th Jan 1930 | Box 52 \ 2 Scan204 | |
| Letter to Firth & Sons Ltd. discussing the design and delivery of rear and front plate springs. | 23th Jan 1930 | Box 52 \ 2 Scan205 | |
| Specifications for a front spring, detailing the number of plates, their thickness, and clip centre measurements. | 21th Jan 1930 | Box 52 \ 2 Scan206 | |
| Blueprint for a special rear road spring for Sports Chassis No. 23 EX. | 21th Jan 1930 | Box 52 \ 2 Scan207 | |
| Letter from Thos. Firth & Sons confirming an order for springs for an experimental chassis. | 23th Jan 1930 | Box 52 \ 2 Scan208 | |
| Letter from Thos. Firth & Sons, Ltd. regarding a delivery schedule and the inability to provide a definite date. | 24th Jan 1930 | Box 52 \ 2 Scan209 | |
| Confirming a settlement with Firth's for the supply of springs to an attached drawing. | 28th Jan 1930 | Box 52 \ 2 Scan210 | |
| Substitution of a rolled eye for a solid eye on the Phantom II Rear Axle Spring to reduce costs. | 4th Feb 1930 | Box 52 \ 2 Scan211 | |
| Letter regarding the progress of work on a set of springs for a sports chassis. | 7th Feb 1930 | Box 52 \ 2 Scan212 | |
| Request to issue lubrication instructions for Sports Car road springs manufactured by Firth's. | 25th Feb 1930 | Box 52 \ 2 Scan213 | |
| Spring leaf tip sent to Messrs. Firth Ltd. for examination. | 14th Mar 1930 | Box 52 \ 2 Scan214 | |
| Letter to a supplier regarding the testing and redesign of five-leaved light springs for model 23-EX. | 14th Mar 1930 | Box 52 \ 2 Scan215 | |
| Letter from a supplier regarding the design and manufacturing of five-leaf light springs following a test failure. | 19th Mar 1930 | Box 52 \ 2 Scan216 | |
| Letter to supplier Thos. Firth & Sons, Ltd. regarding drawing F.82033 and an order for special five-leaf front springs. | 20th Mar 1930 | Box 52 \ 2 Scan217 | |
| Order request for a pair of modified five-leaf stiffer type front springs from Messrs. Firth & Sons, Ltd. | 20th Mar 1930 | Box 52 \ 2 Scan218 | |
| Change of steel for exhaust valves and the resulting scrap costs. | 8th Apr 1930 | Box 52 \ 2 Scan219 | |
| Letter from a supplier confirming a 4 to 5 week lead time for one set of 40/50 HP 5 leaf road springs. | 11th Apr 1930 | Box 52 \ 2 Scan220 | |
| Urgent need to order main plates for 40/50 HP rear axle springs from Messrs. Firth. | 12th Apr 1930 | Box 52 \ 2 Scan221 | |
| Order for a set of stiffer type road springs for experimental use on Major Segrave's car. | 12th Apr 1930 | Box 52 \ 2 Scan222 | |
| Letter to a supplier regarding the manufacture and defects of Phantom II stiffer type road springs. | 8th May 1930 | Box 52 \ 2 Scan223 | |
| Letter regarding improvements to the bedding of leaves for Phantom II stiffer type road springs. | 12th May 1930 | Box 52 \ 2 Scan224 | |
| Urgent internal request to order a pair of special front springs for a 20 HP model from Firths. | 14th May 1930 | Box 52 \ 2 Scan225 | |
| Order request for a pair of special low rating front springs for a Phantom II. | 19th May 1930 | Box 52 \ 2 Scan226 | |
| Rejected cast of S.L.V. steel for valves, the resulting production difficulties, and the analysis of a new cast. | 2nd Jun 1930 | Box 52 \ 2 Scan227 | |
| Letter regarding the rejection of a cast of S.L.V. steel for valves and the ordering of a further cast from Messrs Firths. | 4th Jun 1930 | Box 52 \ 2 Scan228 | |
| Supply delay of S.L.V. Valve Steel and the proposal to use H.R. Crown Steel as a substitute. | 1st Jun 1930 | Box 52 \ 2 Scan229 | |
| The supply and allocation of S.L.V. Steel for Valves. | 30th Jun 1930 | Box 52 \ 2 Scan230 | |
| Conservation of S.L.V. Steel due to a supply shortage and a dispute with supplier Firths over H.R. Crown Steel. | 11th Jul 1930 | Box 52 \ 2 Scan231 | |
| Postscript memo about an upcoming works closure for the annual holiday and its impact on steel supplies. | 1st Jul 1930 | Box 52 \ 2 Scan232 | |
| The experimental use of H.R. Crown Steel for inlet valves as a replacement for S.L.V. steel. | 24th Jul 1930 | Box 52 \ 2 Scan233 | |
| Despatch order for the replacement of a pair of failed special front springs for a 20-HP chassis. | 10th Jul 1930 | Box 52 \ 2 Scan234 | |
| The failure and return of two 20 HP front springs for rebuilding. | 10th Jul 1930 | Box 52 \ 2 Scan235 | |
| Letter to a supplier regarding the failure of two 20 HP front springs during testing, requesting their opinion and replacement. | 10th Jul 1930 | Box 52 \ 2 Scan236 | |
| Internal order request for two 20 HP front springs with specific poundage for Mr. Royce's car. | 10th Jul 1930 | Box 52 \ 2 Scan237 | |
| Letter to a supplier regarding the failure and performance discrepancy of two experimental springs. | 13th Aug 1930 | Box 52 \ 2 Scan238 | |
| Page 2 of a letter discussing spring design modification and performance consistency. | 13th Aug 1930 | Box 52 \ 2 Scan239 | |
| The examination and failure analysis of two experimental 20 HP Front Springs. | 6th Aug 1930 | Box 52 \ 2 Scan240 | |
| Letter from a supplier regarding the cause of a component failure due to overstressing and fatigue. | 6th Aug 1930 | Box 52 \ 2 Scan241 | |
| Letter to Thos Firth & Sons regarding the performance of springs during an intensive test and requesting suggestions for improvement. | 13th Aug 1930 | Box 52 \ 2 Scan242 | |
| The satisfactory examination of nitrided Firth's H.R. Crown valve stems from Nitralloy Limited. | 17th Sep 1930 | Box 52 \ 2 Scan243 | |
| Internal order for a pair of special stiffer type road springs to be sourced from Messrs. Firth Ltd. | 22th Sep 1930 | Box 52 \ 2 Scan244 | |
| Urgent request to order two pairs of low rating front springs for a 20 HP vehicle. | 26th Sep 1930 | Box 52 \ 2 Scan245 | |
| Requesting the creation of a pair of Austenitic steel discs for testing as forged cylinder liners. | 7th Oct 1930 | Box 52 \ 2 Scan246 | |
| Returning two low rating front springs to Firths Ltd. to have the poundage altered. | 8th Oct 1930 | Box 52 \ 2 Scan247 | |
| The ordering and modification of low-rating road springs. | 8th Oct 1930 | Box 52 \ 2 Scan248 | |
| Composition and heat treatment of various Firth's austenitic steels. | 10th Oct 1930 | Box 52 \ 2 Scan249 | |
| Letter from a supplier regarding modifications to an order for rear springs. | 16th Oct 1930 | Box 52 \ 2 Scan250 | |
| Technical letter discussing modifications for an order of springs with increased camber and deflection. | 15th Oct 1930 | Box 52 \ 2 Scan251 | |
| Letter discussing the specifications and stress analysis of rear springs for a 20 HP model. | 15th Oct 1930 | Box 52 \ 2 Scan252 | |
| Letter to supplier Thos. Firth & Sons, Ltd. clarifying an order for experimental springs. | 17th Oct 1930 | Box 52 \ 2 Scan253 | |
| Letter discussing specifications for 1300 lbs. rear springs, including deflection, design, and resistance to failure. | 17th Oct 1930 | Box 52 \ 2 Scan254 | |
| Letter from Thos. Firth & Sons confirming the order for special springs has been put in hand. | 21th Oct 1930 | Box 52 \ 2 Scan255 | |
| Sending two pairs of rear springs for camber alteration to Messrs. Thos. Firth & Sons, Ltd. | 21th Oct 1930 | Box 52 \ 2 Scan256 | |
| Refurbishment of worn 20 HP rear road springs by Messrs. Firths. | 23th Oct 1930 | Box 52 \ 2 Scan257 | |
| Internal order request for Phantom II road springs with specific measurements. | 8th Nov 1930 | Box 52 \ 2 Scan258 | |
| Internal memorandum requesting an order for Phantom II road springs and discussing design specifications. | 29th Nov 1930 | Box 52 \ 2 Scan259 | |
| Urgent request for a set of special road springs for a Phantom II car, including detailed specifications. | 1st Dec 1930 | Box 52 \ 2 Scan260 | |
| Letter from a supplier confirming the design and delivery schedule for a set of 40/50 Road Springs for Mr. Royce's car. | 3rd Dec 1930 | Box 52 \ 2 Scan261 | |
| Internal order request for two sets of 20 HP springs. | 13th Dec 1930 | Box 52 \ 2 Scan262 | |
| Specification sheet for lower rating springs required for model 18-G4. | 18th Dec 1930 | Box 52 \ 2 Scan263 | |
| Letter regarding special springs with increased deflection for a 20 HP Chassis, detailing changes to mainplate thickness and resulting stress. | 18th Dec 1930 | Box 52 \ 2 Scan264 | |
| Internal order for front and rear 40/50 model road springs with detailed specifications. | 23th Jan 1931 | Box 52 \ 2 Scan265 | |
| Order for two pairs of 20 HP front road springs with specifications. | 23th Jan 1931 | Box 52 \ 2 Scan266 | |
| Internal order specifying details for Phantom 1 front and rear road springs. | 28th Jan 1931 | Box 52 \ 2 Scan267 | |
| Preliminary specification for a low rating suspension for the 20 HP model, modified from the Phantom II for the American market. | 2nd Mar 1931 | Box 52 \ 2 Scan268 | |
| Update on the manufacturing and delivery schedules for F-Type and R-Type engine components. | 2nd Mar 1931 | Box 52 \ 2 Scan269 | |
| Listing various road springs in stores for disposal, with instructions for each batch. | 6th Mar 1931 | Box 52 \ 2 Scan270 | |
| Request to allot various American Type, 25 HP, front, and rear road springs to the Experimental Department. | 7th Mar 1931 | Box 52 \ 2 Scan271 | |
| Requesting an alteration to the poundage and camber specifications for P.I. Road Springs. | 23th Mar 1931 | Box 52 \ 2 Scan272 | |
| Letter regarding an order to alter springs, providing alternative recommendations. | 31th Mar 1931 | Box 52 \ 2 Scan273 | |
| Comparison of specifications, plate dimensions, and stresses for three different spring designs. | 8th Apr 1931 | Box 52 \ 2 Scan274 | |
| Cover letter to a supplier regarding the dimensions of spring clips. | 8th Apr 1931 | Box 52 \ 2 Scan275 | |
| Sketch detailing the minimum and maximum dimensional tolerances for the P1 Rear Springs. | 18th Apr 1931 | Box 52 \ 2 Scan276 | |
| Sending two rear springs to Cricklewood for car GLR-59, with a handwritten request for the springs' specifications. | 18th Apr 1931 | Box 52 \ 2 Scan277 | |
| Instruction to fit low rating springs to the rear of chassis No. 110-DC. | 20th Apr 1931 | Box 52 \ 2 Scan278 | |
| Letter to Messrs Thos. Firth & Sons regarding the testing and proposed redesign of flexible road springs for a 25 HP car. | 21th May 1931 | Box 52 \ 2 Scan279 | |
| Letter from Thos. Firth & John Brown Limited regarding an enquiry for flexible road springs. | 22th May 1931 | Box 52 \ 2 Scan280 | |
| Letter from a supplier discussing the design and testing of alternative flexible road springs for a 20 HP car. | 27th May 1931 | Box 52 \ 2 Scan281 | |
| Particulars of high deflection front springs for the 20/25 HP model, including three alternative suggestions. | 27th May 1931 | Box 52 \ 2 Scan282 | |
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