| Description | Date | Identifier | |
| The features and testing plans for the 4.EX experimental chassis. | 27th Feb 1920 | Box 41 \ 1 Scan081 | |
| Extract listing experimental parts fitted to 40/50 chassis models. | 15th Apr 1920 | Box 41 \ 1 Scan082 | |
| Valve mechanism noises at higher engine speeds, attributed to valve spring vibration. | 1st Jan 1921 | Box 41 \ 1 Scan083 | |
| Recommendation to replace faulty rectangular inlet valve springs with improved round wire springs on 20 HP Tourist Trophy cars. | 25th Jan 1922 | Box 41 \ 1 Scan084 | |
| The comparative endurance testing of valve springs, including a proposed American design. | 23th Aug 1923 | Box 41 \ 1 Scan085 | |
| Instruction to alter the steering lever to the other side on the front axle for the American model. | 27th Sep 1919 | Box 41 \ 1 Scan086 | |
| Decisions on the production and supply of chassis for the American market. | 31th Oct 1919 | Box 41 \ 1 Scan087 | |
| Report from a conference discussing proposed alterations for American market cars. | 2nd Dec 1919 | Box 41 \ 1 Scan088 | |
| Points for attention following an American visit regarding vehicle components. | 11th Nov 1920 | Box 41 \ 1 Scan089 | |
| Letter from Rolls Royce of America Inc. chasing prints for the re-lubrication of the Axle Control Sphere. | 4th Aug 1921 | Box 41 \ 1 Scan090 | |
| Proposal memo regarding an alteration to Akermite Pivot Thrust Washers. | 28th Aug 1923 | Box 41 \ 1 Scan091 | |
| Letter discussing the wear and lubrication of pivot pin bushes and a proposed solution for oil spillage. | 28th Jul 1923 | Box 41 \ 1 Scan092 | |
| Letter discussing the performance of an Ackeraite Pivot Thrust Washer after 7500 miles of use, comparing it to Genelite. | 15th Aug 1923 | Box 41 \ 1 Scan093 | |
| Letter from the American branch to Derby discussing front axle faults, specifically swerving under braking and 'tramping'. | 8th Dec 1926 | Box 41 \ 1 Scan094 | |
| Axle frequency, shock absorber performance, and front brake squeaking issues. | 8th Dec 1926 | Box 41 \ 1 Scan095 | |
| Braking tests and steering behavior with a new front axle. | 21th Dec 1926 | Box 41 \ 1 Scan096 | |
| Technical response discussing solutions for wheel wobble, tramping, and shimmy issues. | 21th Dec 1926 | Box 41 \ 1 Scan097 | |
| Remedies for steering wobble, brake squeaks, and other axle-related issues. | 21th Dec 1926 | Box 41 \ 1 Scan098 | |
| Letter from the American to the British office regarding front axle standardization and testing. | 5th May 1927 | Box 41 \ 1 Scan099 | |
| Page 2 of a letter concerning the fitting of aluminium guards to prevent ice banking around levers. | 5th May 1927 | Box 41 \ 1 Scan100 | |
| Comparing brake servo multiplication and braking effort percentages between Phantom models. | 15th Feb 1927 | Box 41 \ 1 Scan101 | |
| Changes to front and rear braking proportions and test results. | 15th Feb 1927 | Box 41 \ 1 Scan102 | |
| Cover note forwarding a copy of a letter from Mr. Olley regarding RRAI Brakes for comment. | 17th May 1929 | Box 41 \ 1 Scan103 | |
| Letter suggesting modifications to the servo cam-levers to resolve issues with the brake servo system. | 6th May 1929 | Box 41 \ 1 Scan104 | |
| Report discussing modifications to servo multiplication and brake linings to reduce squeaking. | 20th Oct 1929 | Box 41 \ 1 Scan105 | |
| Blueprint of a servo operating lever assembly and dog development. | 20th Oct 1929 | Box 41 \ 1 Scan106 | |
| Alteration report discussing brake troubles and potential improvements to the servo system. | 24th May 1929 | Box 41 \ 1 Scan107 | |
| Correspondence about brakes, enclosing a copy and photos for comment. | 17th Aug 1929 | Box 41 \ 1 Scan108 | |
| Letter discussing the design, testing, and manufacturing costs of brake ball thrust cam levers. | 3rd Jun 1929 | Box 41 \ 1 Scan109 | |
| Letter proposing the omission of a star spring and bushing to ensure even bedding of cam faces. | 3rd Jun 1929 | Box 41 \ 1 Scan110 | |
| Photograph displaying four lever arms with their associated ball bearing components. | 4th Jul 1929 | Box 41 \ 1 Scan111 | |
| Letter to Rolls-Royce of America regarding the front axle control anchorage and a proposed alteration. | 4th Jul 1929 | Box 41 \ 1 Scan112 | |
| Tests on ball thrust levers and potential modifications to R.R.A.I. brakes. | 18th Jul 1929 | Box 41 \ 1 Scan113 | |
| Two distinct sources of a clanking noise in the brake system upon release and proposing a solution. | 8th Aug 1929 | Box 41 \ 1 Scan114 | |
| Requesting an electrolytic vacuum valve for experimental work. | 9th Aug 1919 | Box 41 \ 2 Scan001 | |
| Letter discussing the sourcing and use of electrolytic vacuum valves for accumulator charging and wireless telegraphy. | 28th Aug 1919 | Box 41 \ 2 Scan002 | |
| Requesting to see new vacuum valve specimens from the US for potential use in car lighting dynamo systems. | 18th Sep 1919 | Box 41 \ 2 Scan003 | |
| The use of rectifier valves for wireless apparatus on trans-Atlantic flight machines and for battery charging. | 20th Sep 1919 | Box 41 \ 2 Scan004 | |
| Requesting samples of electrolytic vacuum valves for experimentation from the R.A.F. | 24th Sep 1919 | Box 41 \ 2 Scan005 | |
| Letter requesting Electrolytic Vacuum Valves for experimental use in controlling a chassis lighting dynamo. | 26th Sep 1919 | Box 41 \ 2 Scan006 | |
| Letter from the Ministry of Munitions of War regarding the sensitive construction of an Electrolytic Vacuum Valve. | 3rd Oct 1919 | Box 41 \ 2 Scan007 | |
| Price list and particulars for Thermionic Valves from the General Electric Co. Ltd. | 7th Oct 1919 | Box 41 \ 2 Scan008 | |
| Letter from Osram-Robertson Lamp Works regarding the supply of rectifying valves, with an internal note clarifying interest. | 9th Oct 1919 | Box 41 \ 2 Scan009 | |
| Quotation from Osram-Robertson Lamp Works for O.R.3 rectifying valves. | 20th Oct 1919 | Box 41 \ 2 Scan010 | |
| Request to obtain up-to-date catalogues for thermionic valves from three specified companies. | 21th Nov 1922 | Box 41 \ 2 Scan011 | |
| Quotation for B.T.H. wireless valves from The British Thomson-Houston Company Limited. | 24th Nov 1922 | Box 41 \ 2 Scan012 | |
| Enquiry to the Marconi Osram Valve Co. for a rectifying valve suitable for high voltages to measure ignition system impulses. | 30th Nov 1922 | Box 41 \ 2 Scan013 | |
| Continuation of a letter discussing the suitability of a valve for testing insulating materials. | 8th Dec 1922 | Box 41 \ 2 Scan014 | |
| Enquiries made to source a specific rectifying valve. | 8th Dec 1922 | Box 41 \ 2 Scan015 | |
| Copy of a letter from The British Thomson-Houston Company Limited regarding their inability to quote for wireless valves. | 29th Dec 1922 | Box 41 \ 2 Scan016 | |
| Letter from The Edison Swan Electric Co. Ltd. regarding a request for special wireless valves. | 20th Dec 1922 | Box 41 \ 2 Scan017 | |
| Letter from The M.O. Valve Co. Ltd. regarding the supply of rectifying valves for high voltage insulation testing. | 21th Dec 1922 | Box 41 \ 2 Scan018 | |
| Postponing a meeting concerning an electrostatic voltmeter until a suitable rectifying valve has been decided upon. | 25th Jan 1923 | Box 41 \ 2 Scan019 | |
| Follow-up letter to The Edison Swan Electric Co. Ltd. regarding the status of experiments on Wireless Valves. | 16th Feb 1923 | Box 41 \ 2 Scan020 | |
| Letter from Edison Swan Electric Co. Ltd. regarding a delay in experiments concerning wireless valves. | 21th Feb 1923 | Box 41 \ 2 Scan021 | |
| Quotation for type U.2 Rectifying Valves from The M.O. Valve Co. Ltd. | 10th May 1923 | Box 41 \ 2 Scan022 | |
| Quotation from The General Electric Co. Ltd. for a Type U.2 Rectifying Valve. | 19th May 1923 | Box 41 \ 2 Scan023 | |
| Continuation sheet of a letter from The General Electric Co., Ltd. | 23th May 1923 | Box 41 \ 2 Scan024 | |
| Specification and quotation for an oscillograph, rectifying valve, and electrostatic voltmeter. | 23th May 1923 | Box 41 \ 2 Scan025 | |
| Suitable voltage ranges for an instrument and seeking confirmation on oscillograph expenditure. | 23th May 1923 | Box 41 \ 2 Scan026 | |
| Letter regarding the successful manufacturing of a rectifying Wireless Valve. | 31th May 1923 | Box 41 \ 2 Scan027 | |
| Inquiry to General Electric Co. for specific power rectifying valves for high voltage tests. | 15th Oct 1926 | Box 41 \ 2 Scan028 | |
| Technical note on the production testing of coil cases using a trembler ignition coil. | 15th Oct 1926 | Box 41 \ 2 Scan029 | |
| Correspondence with the General Electric Co. Ltd. about a new power rectifying valve. | 4th Nov 1926 | Box 41 \ 2 Scan030 | |
| Required voltage for a rectifying valve and correcting a filament current specification. | 6th Nov 1926 | Box 41 \ 2 Scan031 | |
| The failure of the General Electric Co. to provide prices for two rectifying valves for high tension D.C. insulation tests. | 15th Nov 1926 | Box 41 \ 2 Scan032 | |
| Letter from The General Electric Co. Ltd. regarding the unavailability of a specific rectifying valve and offering alternatives. | 12th Nov 1926 | Box 41 \ 2 Scan033 | |
| Correspondence querying inconsistent filament current specifications for a rectifying valve used in insulation tests. | 16th Nov 1926 | Box 41 \ 2 Scan034 | |
| Continuation page of a document correcting a quoted electrical resistance value. | 29th Nov 1926 | Box 41 \ 2 Scan035 | |
| Communication regarding an order for a Rectifying Valve for High Tension D.C. Insulation Tests. | 29th Nov 1926 | Box 41 \ 2 Scan036 | |
| Letter from The General Electric Co. Ltd. regarding the supply and pricing of an E.H.T. No.2 valve. | 27th Nov 1926 | Box 41 \ 2 Scan037 | |
| And ordering two specific Osram rectifying valves for high tension D.C. insulation tests. | 8th Dec 1926 | Box 41 \ 2 Scan038 | |
| Letter to the General Electric Co. Ltd. regarding discrepancies and test results for a U.4 Rectifying Valve. | 11th Dec 1926 | Box 41 \ 2 Scan039 | |
| Report page discussing the results of valve tests, including emission curves and recommended operational parameters. | 11th Dec 1926 | Box 41 \ 2 Scan040 | |
| Particulars and results of a test on an Osram U4 Rectifying Valve. | 11th Dec 1926 | Box 41 \ 2 Scan041 | |
| The arrival of rectifying valves and leaflets for H.T. D.C. insulation tests. | 15th Dec 1926 | Box 41 \ 2 Scan042 | |
| Letter from The General Electric Co. Ltd. regarding a U.4 type Rectifying valve. | 1st Jan 1927 | Box 41 \ 2 Scan043 | |
| Continuation sheet of a letter from The General Electric Co., Ltd. regarding an attachment. | 6th Jan 1927 | Box 41 \ 2 Scan044 | |
| Letter to The General Electric Co. Ltd. concerning test results and the replacement of a U.4. rectifying valve. | 6th Jan 1927 | Box 41 \ 2 Scan045 | |
| Letter from The General Electric Co., Ltd. regarding a U.4. Rectifying Valve. | 10th Jan 1927 | Box 41 \ 2 Scan046 | |
| Arranging the exchange of a U.4 rectifying valve. | 11th Jan 1927 | Box 41 \ 2 Scan047 | |
| Letter from The General Electric Co. Ltd. regarding a complaint about a U.4 valve and enclosed characteristic curves. | 27th Jan 1927 | Box 41 \ 2 Scan048 | |
| Continuation page of a letter from The General Electric Co., Ltd. | 28th Jan 1927 | Box 41 \ 2 Scan049 | |
| Letter to General Electric Co. Ltd. explaining test result differences for a U.4 valve, with accompanying circuit diagrams. | 28th Jan 1927 | Box 41 \ 2 Scan050 | |
| Page 2 of a letter discussing the performance and advertisement of a valve's delivery curve. | 14th Jan 1927 | Box 41 \ 2 Scan051 | |
| Graph plotting three performance curves (A, B, C) for a U.I. Valve, with associated circuit diagrams for testing at 189 Volts AC. | 14th Jan 1927 | Box 41 \ 2 Scan052 | |
| Faint, handwritten archival document with a red ink stamp in the bottom right corner. | 28th Jan 1927 | Box 41 \ 2 Scan053 | |
| Describing a portable rectifying unit for high voltage D.C. insulation testing. | 29th Apr 1927 | Box 41 \ 2 Scan054 | |
| Page describing the operation of a valve for generating high D.C. voltage for insulation testing. | 29th Apr 1927 | Box 41 \ 2 Scan055 | |
| Page describing the use and functionality of an apparatus for testing D.C. insulation resistance. | 29th Apr 1927 | Box 41 \ 2 Scan056 | |
| The final development and application of an insulation testing apparatus for redmanol coil cases. | 29th Apr 1927 | Box 41 \ 2 Scan057 | |
| Circuit diagram for a High Tension Rectifying Unit used for H.T.D.C tests of insulation. | 29th Apr 1927 | Box 41 \ 2 Scan058 | |
| Blank page with a date stamp from Derby. | 29th Apr 1927 | Box 41 \ 2 Scan059 | |
| Connection diagram for high-tension direct current insulation tests using a trembler coil and rectifying valve. | 29th Apr 1927 | Box 41 \ 2 Scan060 | |
| Two-page document with a blank left page and illegible text on the right, bearing a purple date stamp. | 29th Apr 1927 | Box 41 \ 2 Scan061 | |
| Faulty G.E.C. rectifying valve, type U3, and the urgent request for its replacement. | 7th Oct 1927 | Box 41 \ 2 Scan062 | |
| Letter from a supplier regarding the return and replacement of a rectifying valve. | 10th Oct 1927 | Box 41 \ 2 Scan063 | |
| Suitability of a replacement rectifying valve and potential solutions to prevent filament distortion. | 11th Oct 1927 | Box 41 \ 2 Scan064 | |
| Letter from General Electric Co. Ltd. responding to a query about a U.3. Rectifying Valve. | 24th Oct 1927 | Box 41 \ 2 Scan065 | |
| Letter from The General Electric Co., Ltd. reporting on the test results of a valve under high voltage. | 28th Oct 1927 | Box 41 \ 2 Scan066 | |
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