| Description | Date | Identifier | |
| Suitability of the trembler ignition system and its performance at higher speeds. | 1st Oct 1919 | Box 181 \ M11 img244 | |
| Design and urgent requirement for a model of the 40/50 HP electrical system switch box for the post-war series. | 23th Oct 1919 | Box 181 \ M11 img245 | |
| Notes on matters discussed regarding batteries, Condor engine crankshafts, and a petrol tank design. | 24th Oct 1919 | Box 181 \ M11 img246 | |
| Design and material changes for spare wheels, tyres, pendulum levers, radiators, and distributors. | 24th Oct 1919 | Box 181 \ M11 img247 | |
| Experiments for battery ignition systems and notes on torque reaction vibration. | 24th Oct 1919 | Box 181 \ M11 img248 | |
| Design and application of a starter motor for the American 40/50 HP chassis. | 28th Nov 1919 | Box 181 \ M11 img249 | |
| Confirmation of a telegram concerning short connecting rods and reaction vibrations. | 29th Oct 1919 | Box 181 \ M11 img250 | |
| Re-arranging the wiring on chassis 1 EX to improve slow running and general appearance. | 1st Oct 1919 | Box 181 \ M11 img251 | |
| Diagrams showing the routing and mounting of low and high tension wiring and components. | 1st Mar 1911 | Box 181 \ M11 img252 | |
| Cover note from 'E' sending a copy of miscellaneous notes from a visit with Mr. Hives. | 1st Nov 1919 | Box 181 \ M11 img253 | |
| From Mr. Royce detailing modifications for a steering box axle following a bump test. | 5th Dec 1919 | Box 181 \ M11 img254 | |
| Letter from CJ to R regarding a board meeting to discuss 3-speed versus 4-speed gearboxes. | 27th Nov 1923 | Box 181 \ M12 img001 | |
| Letter from C.J. to R. discussing the decline in Goshawk sales due to body weight and size restrictions. | 28th Nov 1923 | Box 181 \ M12 img002 | |
| Confidential letter between directors discussing a board meeting, car body specifications, and pricing. | 30th Nov 1923 | Box 181 \ M12 img003 | |
| Extract from a memo from R. to C.J. regarding a board meeting, a general election, and the matter of 3 or 4 speeds. | 30th Nov 1923 | Box 181 \ M12 img004 | |
| Extract from 'R.' to 'C.J.' expressing disapproval of proposed changes to Goshawk bodies. | 30th Nov 1923 | Box 181 \ M12 img005 | |
| Letter discussing Royce's upset over a 3-speed gearbox and arranging a Board Meeting. | 3rd Dec 1923 | Box 181 \ M12 img006 | |
| From CJ to the Directors regarding the debate over a 3-speed versus 4-speed gearbox, referencing Mr. Royce's views and health. | 12th Dec 1923 | Box 181 \ M12 img007 | |
| From C.J. regarding the Goshawk chassis length and a change of Board Meeting location. | 4th Dec 1923 | Box 181 \ M12 img008 | |
| Letter from Claude Johnson to Mr. Royce explaining the decision to not proceed with the three-speed gearbox. | 22th Nov 1923 | Box 181 \ M12 img009 | |
| Letter enclosing the apprenticeship documents of a former Chief Engineer for preservation in the Company Archives. | 25th Jul 1969 | Box 181 \ M13 \ M13.1 img001 | |
| Series of dated handwritten notes on technical justifications, equipment, and staff instructions. | 25th Jul 1969 | Box 181 \ M13 \ M13.1 img002 | |
| Page 2 of a report on car performance, discussing chassis modifications with stiffer springs and the trade-off between weight and speed. | 28th Mar 1911 | Box 181 \ M13 \ M13.1 img003 | |
| Instructing the Drawing Office to revert to using pinned piston rings instead of the new unpinned double rings. | 28th Mar 1911 | Box 181 \ M13 \ M13.1 img004 | |
| From F.H. Royce regarding a rough drawing for axle strain tests. | 3rd Jul 1912 | Box 181 \ M13 \ M13.1 img005 | |
| Abandoning the Avery Impact Test in favour of the Arnold Test for the heat treatment of front pivots. | 16th Jan 1914 | Box 181 \ M13 \ M13.1 img006 | |
| Letter discussing particulars of a machine from Cambridge Scientific Instrument Co. for measuring the pitch of threads. | 23th Feb 1914 | Box 181 \ M13 \ M13.1 img007 | |
| Response to Monsieur Faroux's report on a car's performance, discussing its weight, speed, and recommending suspension upgrades. | 17th Oct 1916 | Box 181 \ M13 \ M13.1 img008 | |
| Future development of aero engines and the strategic direction of the designing department. | 6th Jan 1920 | Box 181 \ M13 \ M13.1 img009 | |
| Advising against undertaking multiple large projects, like an aero engine and a chassis, concurrently. | 8th Jan 1920 | Box 181 \ M13 \ M13.1 img010 | |
| Potential causes and solutions for poor vehicle acceleration, focusing on carburettor mixture and ignition timing. | 3rd Sep 1920 | Box 181 \ M13 \ M13.1 img011 | |
| Potential causes for poor engine performance, including compression, fuel, and external drag factors. | 3rd Sep 1920 | Box 181 \ M13 \ M13.1 img012 | |
| Progress on the development of a front wheel brake system, including frame modifications and patent considerations. | 19th Aug 1922 | Box 181 \ M13 \ M13.1 img013 | |
| On the policy for making progress, advocating for simplicity, robustness, and consistency of direction. | 15th Feb 1924 | Box 181 \ M13 \ M13.1 img014 | |
| Issue of exhaust fumes entering the car body and proposed solutions. | 29th Mar 1924 | Box 181 \ M13 \ M13.1 img015 | |
| Progress report memo discussing steering, front springs, brakes, and gearbox specifications. | 16th Jan 1924 | Box 181 \ M13 \ M13.1 img016 | |
| Dynamometer tests on a 25 HP model to investigate a boom in the exhaust and engine vibration. | 8th Dec 1930 | Box 181 \ M13 \ M13.2 img001 | |
| Investigation into the causes of over-run booms on a 25 HP Japan Engine (1V-G6). | 8th Dec 1930 | Box 181 \ M13 \ M13.2 img002 | |
| Analysis of different exhaust system configurations and their effect on engine booms. | 8th Dec 1931 | Box 181 \ M13 \ M13.2 img003 | |
| Performance of a dynamo-battery system and a two-rate charge switching scheme. | 9th Dec 1930 | Box 181 \ M13 \ M13.2 img004 | |
| Analysis of dynamo output, field resistance, and battery charging in relation to headlamp current. | 9th Dec 1930 | Box 181 \ M13 \ M13.2 img005 | |
| Technical document detailing the principles and standardized conditions for comparing dynamo output curves. | 9th Dec 1930 | Box 181 \ M13 \ M13.2 img006 | |
| Continued discussion on battery charging systems, comparing single and two-rate charge schemes. | 9th Dec 1930 | Box 181 \ M13 \ M13.2 img007 | |
| Proposal to lengthen the dynamo unit, with an analysis of attached output performance curves. | 1st Dec 1930 | Box 181 \ M13 \ M13.2 img008 | |
| The fuel consumption of a 20 HP car with thermostatically operated shutters, comparing results at different running temperatures. | 16th Dec 1930 | Box 181 \ M13 \ M13.2 img009 | |
| Investigation into misfiring on the 20/25 HP battery ignition system, concluding with a reduction in the sparking plug gap. | 7th Dec 1930 | Box 181 \ M13 \ M13.2 img010 | |
| Sparking plug voltage tests carried out on 20/25, 40/50, and Phantom II chassis. | 7th Dec 1930 | Box 181 \ M13 \ M13.2 img011 | |
| Test results showing plug voltage measurements at varying plug gaps and water temperatures. | 17th Dec 1930 | Box 181 \ M13 \ M13.2 img012 | |
| Plug gap and voltage tests on a 20/25 chassis, including an assistant's report on ignition coil performance. | 7th Dec 1930 | Box 181 \ M13 \ M13.2 img013 | |
| Modifying sparking plug gaps and increasing ignition coil secondary turns for 20/25 and 40/50 chassis. | 7th Dec 1930 | Box 181 \ M13 \ M13.2 img014 | |
| Experiments investigating flywheel vibrations in a 25 HP engine. | 24th Dec 1930 | Box 181 \ M13 \ M13.2 img015 | |
| Comparison of weights and water capacities for 25 HP radiators using large hexagonal-ended copper tubes. | 30th Nov 1931 | Box 181 \ M13 \ M13.2 img016 | |
| Ball thrust washers for small and centre bevel pinions. | 30th Apr 1926 | Box 181 \ M13 \ M13.2 img017 | |
| Modifications and speed trial results for a 25 HP car ordered by Lord Cholmondeley. | 14th Nov 1931 | Box 181 \ M13 \ M13.2 img018 | |
| Development of driver-controlled hydraulic shock absorbers and comparison with other types. | 13th Jun 1931 | Box 181 \ M13 \ M13.2 img019 | |
| Proposal to source a complete instrument board for the 20/25 HP chassis from Messrs Smiths. | 23th Oct 1931 | Box 181 \ M13 \ M13.2 img020 | |
| Successful testing of a synchro-mesh gearbox and its strategic implementation for the 25 HP and Phantom II models. | 20th Oct 1931 | Box 181 \ M13 \ M13.2 img021 | |
| Development of a new epicyclic gearbox for the Phantom II model. | 20th Oct 1931 | Box 181 \ M13 \ M13.2 img022 | |
| The performance of Mulliner's bodywork after a 15,000-mile test in France. | 14th Oct 1931 | Box 181 \ M13 \ M13.2 img023 | |
| Fitting of dummy shutters to a 20/25 HP chassis with a Brewster body, and the wooden subframe for Phantom II cars. | 9th Jan 1931 | Box 181 \ M13 \ M13.2 img024 | |
| Comparison of flywheel test results with and without a tail bearing. | 13th Jan 1931 | Box 181 \ M13 \ M13.2 img025 | |
| Vibration testing of a lightened flywheel for a 25 HP unit. | 13th Jan 1931 | Box 181 \ M13 \ M13.2 img026 | |
| Blueprint of a mirror holder and tail bearing for a 25 HP flywheel. | 14th Jan 1931 | Box 181 \ M13 \ M13.2 img027 | |
| Analysing the 25 HP chassis weight in comparison to a Chrysler car. | 14th Jan 1931 | Box 181 \ M13 \ M13.2 img028 | |
| Review of design faults and proposed solutions for the 25 HP car, focusing on exhaust pipes and slipper wheels. | 26th Jan 1931 | Box 181 \ M13 \ M13.2 img029 | |
| Complaints on engine vibrations, dynamo output, and ignition systems. | 26th Jan 1931 | Box 181 \ M13 \ M13.2 img030 | |
| Technical report discussing carburetter design, petrol pump provisions, 25 HP suspension improvements, and starter motor options. | 28th Jan 1931 | Box 181 \ M13 \ M13.2 img031 | |
| Proposal and discussion on road spring specifications for a Continental Touring 25 HP model. | 30th Jan 1931 | Box 181 \ M13 \ M13.2 img032 | |
| Front axle control and shock absorber placement for the 'Japan' III model. | 2nd Feb 1931 | Box 181 \ M13 \ M13.2 img033 | |
| Proposal for road spring specifications for a Special Touring 25 HP model. | 2nd Feb 1931 | Box 181 \ M13 \ M13.2 img034 | |
| New 6-cylinder, 4-litre Bentley car designed to compete with the 25 HP model. | 3rd Feb 1931 | Box 181 \ M13 \ M13.2 img035 | |
| Summary of faults and troubles experienced on a prototype vehicle, with proposed eliminations for a future model. | 3rd Feb 1931 | Box 181 \ M13 \ M13.2 img036 | |
| List of identified faults, modifications, and standardisation sheets for various vehicle components. | 3rd Feb 1931 | Box 181 \ M13 \ M13.2 img037 | |
| Numbered list of vehicle component modifications and improvements. | 11th Feb 1931 | Box 181 \ M13 \ M13.2 img038 | |
| Mathematical investigation into the benefits of heavy crankshafts and stiff crankcases for the 25 HP engine. | 11th Feb 1931 | Box 181 \ M13 \ M13.2 img039 | |
| Replacement of an uncomfortable pneumatic rear seat cushion on a Park Ward body 25-EX car. | 9th Feb 1931 | Box 181 \ M13 \ M13.2 img040 | |
| Tests on 25 HP flywheel vibrations using a double bearing setup. | 11th Feb 1931 | Box 181 \ M13 \ M13.2 img041 | |
| Blueprint showing the design for a 25 HP Double Flywheel Bearing. | 20th Apr 1931 | Box 181 \ M13 \ M13.2 img042 | |
| Unreliability of fabric couplings on the Phantom II and advocating for their continued use due to their noise-reducing benefits. | 20th Apr 1931 | Box 181 \ M13 \ M13.2 img043 | |
| Comparing a 25 HP integral cast iron crankcase and cylinder block against a standard unit, discussing flywheel rattles, weight, and cost. | 20th Apr 1931 | Box 181 \ M13 \ M13.2 img044 | |
| Overdue specifications for the Japan 1 second half 'T' series 25 HP cars. | 8th May 1931 | Box 181 \ M13 \ M13.2 img045 | |
| Component improvements for the 25 HP model, covering springs, axles, and other systems. | 1st May 1931 | Box 181 \ M13 \ M13.2 img046 | |
| Testing and modifying a 'Japan' engine exhaust system to reduce power loss while maintaining silence. | 9th May 1931 | Box 181 \ M13 \ M13.2 img047 | |
| Table detailing the dimensions of Down Pipes and Fish Tail Pipes for 40/50 HP and 20 HP models. | 9th May 1931 | Box 181 \ M13 \ M13.2 img048 | |
| Results of an experiment on a rigid construction method and its effect on efficiency and performance. | 20th Apr 1931 | Box 181 \ M13 \ M13.2 img049 | |
| Experiment modifying the springing on a Phantom I chassis (110-DC). | 30th Apr 1931 | Box 181 \ M13 \ M13.2 img050 | |
| Road test report on a 25 HP large pin crankshaft to determine its critical speed and the effects of balance weights. | 9th May 1931 | Box 181 \ M13 \ M13.2 img051 | |
| Test report on the effectiveness of a Diamond Engine Mounting system for a 25 HP engine to reduce booms and vibrations. | 11th May 1931 | Box 181 \ M13 \ M13.2 img052 | |
| Page discussing the next steps for increasing the power output of a unit. | 11th May 1931 | Box 181 \ M13 \ M13.2 img053 | |
| Dimensions and dispatch of different Zenith carburettors. | 11th May 1931 | Box 181 \ M13 \ M13.2 img054 | |
| Phantom II and Japan 1 exhaust systems, including manifold failures and potential design modifications. | 19th May 1931 | Box 181 \ M13 \ M13.2 img055 | |
| Graph comparing the performance of two different exhaust manifold designs. | 19th May 1931 | Box 181 \ M13 \ M13.2 img056 | |
| List of new features for a 20/25 HP 'T' Series car being prepared for tests in France. | 21th May 1931 | Box 181 \ M13 \ M13.2 img057 | |
| Crankshaft replacement, speedometer alteration, and the fitting of a new exhaust manifold and pipe. | 23th May 1931 | Box 181 \ M13 \ M13.2 img058 | |
| Sending a booklet on a twin carburetter and future information on a single downdraught carburetter. | 28th May 1931 | Box 181 \ M13 \ M13.2 img059 | |
| Investigation into the cause and potential fixes for a gear rattle on the 25 HP model. | 29th May 1931 | Box 181 \ M13 \ M13.2 img060 | |
| Note on experiments with a flexible drive between the flywheel and gearbox, resulting in gear rattles. | 29th May 1931 | Box 181 \ M13 \ M13.2 img061 | |
| Performance graph comparing a Twin Zenith carburetter against a standard chassis carburetter on the 'Japan' engine. | 22th May 1930 | Box 181 \ M13 \ M13.2 img062 | |
| Petrol supply for low speed jets in single carburetters for Japan. | 3rd Jun 1931 | Box 181 \ M13 \ M13.2 img063 | |
| Verifying that piston motion is the cause of 25 HP overrun gear rattles by fitting heavier cast iron pistons. | 9th Jun 1931 | Box 181 \ M13 \ M13.2 img064 | |
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