| Description | Date | Identifier | |
| Suitability of different sparking plug brands, specifically Sphinx, Mercury and Lodge. | 4th Oct 1921 | Box 79 \ 2 scan0170 | |
| The performance of ignition plugs and lubrication observations on the 6.EX car. | 18th Oct 1921 | Box 79 \ 2 scan0171 | |
| Lubrication methods for spring shackles and rear shock dampers, and a note on a water leak. | 18th Oct 1921 | Box 79 \ 2 scan0172 | |
| Letter from The Sphinx Manufacturing Co. Ltd. detailing successes of their AC-SPHINX plugs in motorsport events. | 29th Jun 1922 | Box 79 \ 2 scan0173 | |
| The submission of Sphinx and AC Titan spark plugs for testing. | 11th Oct 1922 | Box 79 \ 2 scan0174 | |
| Returning six A.C. Sphinx Sparking Plugs to the manufacturer in Birmingham. | 22th Jan 1923 | Box 79 \ 2 scan0175 | |
| Internal request to order 3 dozen A.C. Sparking Plugs from the Sphinx Sparking Plug Co. | 28th Jan 1925 | Box 79 \ 2 scan0176 | |
| Performance comparison of Lodge and A.C. Sphinx spark plugs under test conditions. | 2nd Feb 1925 | Box 79 \ 2 scan0177 | |
| Cover note from ROY forwarding copies of correspondence concerning A.C. Plugs. | 3rd Mar 1925 | Box 79 \ 2 scan0178 | |
| Letter from the A.C. Sphinx Sparking Plug Company regarding spark plug options and an order. | 28th Feb 1925 | Box 79 \ 2 scan0179 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. discussing a potential price reduction and requesting a meeting. | 3rd Mar 1925 | Box 79 \ 2 scan0180 | |
| Letter to the AC-SPHINX Sparking Plug Co. Ltd regarding the observation of submitted plugs against Order No. 39337. | 3rd Mar 1925 | Box 79 \ 2 scan0181 | |
| Advice note from The AC-Sphinx Sparking Plug Co. Ltd. for plugs. | 20th Aug 1925 | Box 79 \ 2 scan0182 | |
| The dispatch of 12 plugs from the A.C. Sphinx Plug Company for testing. | 26th Aug 1925 | Box 79 \ 2 scan0183 | |
| Letter from A.C. Sphinx Sparking Plug Company regarding previous orders and a new model of spark plug. | 22th Aug 1925 | Box 79 \ 2 scan0184 | |
| Letter from AC-SPHINX SPARKING PLUG CO. LTD discussing the performance of single vs three-point spark plugs. | 22th Aug 1925 | Box 79 \ 2 scan0185 | |
| Letter from AC-Sphinx Sparking Plug Company apologising for a delay and discussing different types of spark plugs. | 21th Oct 1925 | Box 79 \ 2 scan0186 | |
| Covering letter attaching correspondence from The A.C. Sphinx Sparking Plug Co. Ltd. regarding two dozen returned A.C. plugs. | 22th Oct 1925 | Box 79 \ 2 scan0187 | |
| Follow-up letter requesting comments on unsuitable A.C. Plugs returned to the A.C. Sphinx Sparking Plug Co. Ltd. | 3rd Nov 1925 | Box 79 \ 2 scan0188 | |
| Order for 2 dozen A.C. (Sphinx) sparking plugs. | 4th Nov 1925 | Box 79 \ 2 scan0189 | |
| The delivery, standardization, and confidential pricing of A.C. Plugs. | 18th Nov 1925 | Box 79 \ 2 scan0190 | |
| Submission of 12 latest type three-point B.11 Detachable Plugs from the A.C. Sphinx Plug Company for reporting. | 10th Mar 1926 | Box 79 \ 2 scan0191 | |
| Testing A-C sparking plugs type No.114-Q in F.11 engines. | 17th Apr 1928 | Box 79 \ 2 scan0192 | |
| Letter from the A.C. Sphinx Sparking Plug Company discussing the performance of spark plugs on an F.11 engine. | 14th Jun 1928 | Box 79 \ 2 scan0193 | |
| Letter to the A.C. Sphinx Sparking Plug Co. regarding a delay in replying and the testing of plugs. | 19th Jun 1928 | Box 79 \ 2 scan0194 | |
| Pamphlet from AC-Sphinx Sparking Plug Co. Ltd. about their new Isovolt alloy. | 4th Apr 1930 | Box 79 \ 2 scan0195 | |
| Alterations by Mr. Royce to an indicator diagram apparatus, detailing a proposed epicyclic gear drive. | 17th Mar 1917 | Box 79 \ 3 scan0001 | |
| Procedure for creating an engine indicator diagram using an epicyclic case and pressure gauge readings. | 15th Feb 1916 | Box 79 \ 3 scan0002 | |
| With a sketch detailing a simple, belt-driven vertical cylinder pump design. | 15th Feb 1916 | Box 79 \ 3 scan0003 | |
| Schematic diagram of an indicator diagram apparatus. | 13th Oct 1929 | Box 79 \ 3 scan0004 | |
| Return of an Indicator Diagram Apparatus and a proposal for its epicyclic gear's use in magneto investigation. | 24th Mar 1917 | Box 79 \ 3 scan0005 | |
| Letter to Professor B. Hopkinson inquiring about an optical indicator for aero engines. | 26th Mar 1917 | Box 79 \ 3 scan0006 | |
| Design and application of an indicator diagram apparatus for aero engines. | 27th Mar 1917 | Box 79 \ 3 scan0007 | |
| Page two of a typed memo requesting copies to stay informed on a particular matter. | 27th Mar 1917 | Box 79 \ 3 scan0008 | |
| Raising questions about the design of an indicator diagram apparatus, specifically concerning the rotary valve and oil system. | 1st Mar 1917 | Box 79 \ 3 scan0009 | |
| Continuation of a memo discussing an air vessel on a pipe and arranging work with Mr. Nadin. | 1st Mar 1917 | Box 79 \ 3 scan0010 | |
| Letter from the Air Board regarding the accuracy of an optical indicator for aero engines. | 29th Mar 1917 | Box 79 \ 3 scan0011 | |
| Responding to a query on the indicator diagram apparatus, detailing valve design, relief valve placement, and oil pump configuration. | 31th Mar 1917 | Box 79 \ 3 scan0012 | |
| Technical note on controlling pressure growth using an oil pump, air vessel, and indicator valve for engine diagrams. | 15th Feb 1915 | Box 79 \ 3 scan0013 | |
| Instruction sheet for an order to Messrs. Hormald & Hestenton for one brass casting. | 7th Jul 1917 | Box 79 \ 3 scan0014 | |
| Instructions to machine and fit parts for a Differential Gear-Indicator-Diagram Apparatus based on Drawing J.79. | 7th Jul 1917 | Box 79 \ 3 scan0015 | |
| Instruction to produce patterns from a drawing for a differential gear indicator diagram apparatus. | 7th Jul 1907 | Box 79 \ 3 scan0016 | |
| Instruction to order various castings from Brown's Foundry for an Indicator Diagram Apparatus 'Three' Throw Pump. | 11th Jul 1917 | Box 79 \ 3 scan0017 | |
| Instructions to Messrs. Normald & Peskett for machining parts for a Three Throw Pump based on blueprints. | 11th Jul 1917 | Box 79 \ 3 scan0018 | |
| Instruction to Messrs. Wormald & Restorick to make bronze castings for a Three Throw Pump. | 11th Jul 1917 | Box 79 \ 3 scan0019 | |
| Instructions for creating patterns for a three-throw pump indicator-diagram apparatus. | 11th Jul 1917 | Box 79 \ 3 scan0020 | |
| Holding an experiment in abeyance pending further developments with the Dalby-Watson indicator apparatus. | 13th Oct 1917 | Box 79 \ 3 scan0021 | |
| Dalby Watson indicator and a patentable method for obtaining engine indicator diagrams. | 2nd Jan 1918 | Box 79 \ 3 scan0022 | |
| Adoption and development of the Dalby Watson indicator diagram apparatus for aero engines. | 5th Jan 1918 | Box 79 \ 3 scan0023 | |
| Suggesting a simpler indicator scheme to avoid issues found with the Dalby-Watson indicator. | 1st Jan 1918 | Box 79 \ 3 scan0024 | |
| Confirming a conversation about gathering drawings for the Indicator Diagram Apparatus job. | 16th Jan 1918 | Box 79 \ 3 scan0025 | |
| Design and development of an Indicator Diagram Apparatus. | 13th Mar 1918 | Box 79 \ 3 scan0026 | |
| Suitability of different oil pumps for testing apparatus and Mr. Royce's feedback. | 13th Mar 1918 | Box 79 \ 3 scan0027 | |
| Summarizing a meeting about the responsibility for designing experimental test tackle and special devices. | 6th Apr 1918 | Box 79 \ 3 scan0028 | |
| Transfer of an Eagle Engine job and Indicator Diagram Apparatus work to Mr. Bailey's department. | 6th Apr 1918 | Box 79 \ 3 scan0029 | |
| Listing parts required for an Indicator Diagram Apparatus for an Epicyclic Gear and Drive. | 22th Apr 1918 | Box 79 \ 3 scan0030 | |
| The receipt of various Hoffman ball bearings for an Indicator Diagram Apparatus. | 10th Jul 1918 | Box 79 \ 3 scan0031 | |
| Proposal for an oil pump to be used for crankshaft testing and other experiments. | 13th Jul 1918 | Box 79 \ 3 scan0032 | |
| Design specification for a multi-cylinder pump, detailing its construction and components, including a sketch. | 13th Jul 1918 | Box 79 \ 3 scan0033 | |
| Design specifications for an oil pump, valve chest, and associated components. | 13th Jul 1918 | Box 79 \ 3 scan0034 | |
| Progress of an indicator for an engine operated by oil pressure. | 23th Sep 1919 | Box 79 \ 3 scan0035 | |
| List of five pressure gauges for an indicator diagram apparatus. | 26th Sep 1919 | Box 79 \ 3 scan0036 | |
| Apparatus for indicating pressure in high-speed engines. | 2nd Feb 1921 | Box 79 \ 3 scan0037 | |
| Update on the progress of the Indicator Diagram Apparatus, which was delayed by work on the Goshawk. | 4th Mar 1921 | Box 79 \ 3 scan0038 | |
| Assessment of the Royce Indicator Apparatus, detailing missing components and proposing modifications for engine testing. | 4th Jan 1923 | Box 79 \ 3 scan0039 | |
| Letter from G. Cussons Ltd. regarding a demonstration of the Dalby-Watson Optical Indicator for internal combustion engines. | 3rd Sep 1917 | Box 79 \ 3 scan0040 | |
| Letter to G. Cussons, Ltd. expressing interest in the Dalby-Watson Optical Indicator for engines. | 4th Sep 1917 | Box 79 \ 3 scan0041 | |
| Letter from G. Cussons, Ltd. regarding particulars and a photo of an Optical Indicator. | 6th Sep 1917 | Box 79 \ 3 scan0042 | |
| Letter to Messrs. G. Cussons, Ltd. enquiring about the performance of a Dalby-Watson Optical Indicator. | 8th Sep 1917 | Box 79 \ 3 scan0043 | |
| Data recording chart with a vertical scale from 0 to 300, produced by G. Cussons Ltd. | 18th Sep 1917 | Box 79 \ 3 scan0044 | |
| Letter from G. Cussons, Ltd. regarding the performance testing of an engine indicator. | 18th Sep 1917 | Box 79 \ 3 scan0045 | |
| Letter to G. Cussons, Ltd. discussing the Dalby-Watson Optical Indicator and arranging a visit to see it in operation. | 14th Sep 1917 | Box 79 \ 3 scan0046 | |
| Letter from G. Cussons, Ltd. regarding diagrams for an optical indicator and arranging a visit. | 15th Sep 1917 | Box 79 \ 3 scan0047 | |
| Letter to Messrs G. Cussons, Ltd. arranging an inspection visit for a Dalby-Watson Optical Indicator. | 19th Sep 1917 | Box 79 \ 3 scan0048 | |
| Letter from G. Cussons, Ltd. discussing the placement, features, and production of the Dalby Watson Optical Indicator. | 27th Sep 1918 | Box 79 \ 3 scan0049 | |
| Dalby-Watson Optical Indicator from G. Cussons Ltd. | 27th Sep 1917 | Box 79 \ 3 scan0050 | |
| Visit to observe an engine indicator instrument in operation on a test rig. | 9th Aug 1917 | Box 79 \ 3 scan0051 | |
| Light spring diagrams with Messrs. Cussons and seeking guidance on continuing the project. | 9th Aug 1917 | Box 79 \ 3 scan0052 | |
| Dalby-Watson Optical Indicator and the availability of a specially ordered arc lamp. | 3rd Oct 1917 | Box 79 \ 3 scan0053 | |
| Letter to G. Cussons Ltd. regarding the use of a Dalby-Watson Optical Indicator on an engine. | 5th Sep 1917 | Box 79 \ 3 scan0054 | |
| Continued letter enquiring about the price and delivery of an indicator for measuring engine cylinder pressure. | 10th Oct 1917 | Box 79 \ 3 scan0055 | |
| Letter from G. Cussons, Ltd. discussing the approval, inspection, and development of an indicator rig. | 10th Oct 1917 | Box 79 \ 3 scan0056 | |
| Letter to Messrs. C. Gussons, Ltd. confirming a meeting to view a 12 cylinder engine on test. | 12th Oct 1917 | Box 79 \ 3 scan0057 | |
| Post Office Telegraph from Cussons of Manchester arranging an engine inspection in Derby. | 12th Oct 1917 | Box 79 \ 3 scan0058 | |
| Telegram received by telephone regarding a preference for an engine inspection time. | 12th Oct 1917 | Box 79 \ 3 scan0059 | |
| Confirmation of a telegram sent to Cussons in Manchester regarding a car meeting at the station. | 25th Oct 1917 | Box 79 \ 3 scan0060 | |
| Request to Mr. Southern for a blueprint of the arrangement of an Eagle Aero Engine Series 6 and 7. | 25th Oct 1917 | Box 79 \ 3 scan0061 | |
| Letter to Messrs. G. Cussons Ltd. enclosing blueprints for a Series 6 Eagle Aero Engine and Scheme 251 for an optical indicator rig. | 27th Oct 1917 | Box 79 \ 3 scan0062 | |
| Letter to G. Cussons Ltd. regarding the testing of an optical indicator on a captured Mercedes 260 HP engine. | 24th Nov 1917 | Box 79 \ 3 scan0063 | |
| Letter from G. Cussons Ltd. regarding a delay in a scheme for an indicator rig and requesting a sketch of a Mercedes-Gotha Biplane Engine. | 26th Nov 1917 | Box 79 \ 3 scan0064 | |
| Internal request for a general arrangement drawing of a Mercedes-Gotha biplane engine for an indicator rig adaptation. | 27th Nov 1917 | Box 79 \ 3 scan0065 | |
| Letter to Messrs C. Cussons Ltd. regarding photostat arrangements for an optical indicator on a Mercedes Gotha Biplane Engine. | 20th Dec 1917 | Box 79 \ 3 scan0066 | |
| From R. to EFC discussing the Dalby Watson indicator and a patentable method for obtaining an indicator diagram. | 2nd Jan 1918 | Box 79 \ 3 scan0067 | |
| Adaptation of a Dalby Watson indicator for Eagle and Mercedes Gotha engines. | 5th Jan 1918 | Box 79 \ 3 scan0068 | |
| Letter to G. Cussons Ltd. regarding the adaptation of their optical indicator for the Eagle engine. | 5th Jan 1918 | Box 79 \ 3 scan0069 | |
| Suggesting a simpler scheme for an indicator to avoid the troubles found with the Dalby-Watson model. | 9th Jan 1918 | Box 79 \ 3 scan0070 | |
| Telegram received by telephone arranging for a meeting at Derby train station. | 16th Jan 1918 | Box 79 \ 3 scan0071 | |
| Procurement and fitting of a Dalby-Watson Optical Indicator to an Eagle engine. | 18th Jan 1918 | Box 79 \ 3 scan0072 | |
| Request to place an order for a Dalby-Watson Optical Indicator and its accessories. | 18th Jan 1918 | Box 79 \ 3 scan0073 | |
| Instruction to obtain further particulars and a dimensioned drawing for a Dalby-Watson Optical Indicator. | 26th Jan 1918 | Box 79 \ 3 scan0074 | |
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