| Description | Date | Identifier | |
| Description of an electrical relay device that controls accumulator charging based on voltage levels. | 29th Apr 1930 | Box 59 \ 1 Scan359 | |
| Letter detailing the advantages and applications of a patented relay device for controlling battery charging. | 30th Apr 1930 | Box 59 \ 1 Scan360 | |
| Letter responding to a proposal for an Auto Charge Control Switch, declining further details due to existing internal development. | 30th Apr 1930 | Box 59 \ 1 Scan361 | |
| Modifications to dynamo armatures to increase current output at high speeds. | 9th Jan 1931 | Box 59 \ 1 Scan362 | |
| Internal memorandum discussing various types of dynamo systems and regulator technologies. | 19th Jan 1931 | Box 59 \ 1 Scan363 | |
| Modifications to external regulator control, comparing dithering contacts with long-period vibrator regulators for dynamo battery systems. | 9th Jan 1931 | Box 59 \ 1 Scan364 | |
| Comparison of relative heating and output for shunt wound versus battery controlled dynamos. | 9th Jan 1931 | Box 59 \ 1 Scan365 | |
| Test and calibration report for a 20 HP Speedometer, detailing issues with readings when hot and cold. | 4th Jan 1930 | Box 59 \ 2 Scan001 | |
| Speedometer calculations and testing for a 10,000-mile test on car 23-EX. | 17th Jan 1930 | Box 59 \ 2 Scan002 | |
| Test report for an A.T. type speedometer, detailing readings at various temperatures and RPMs. | 27th Jan 1930 | Box 59 \ 2 Scan003 | |
| Urgent need for information on speedometer settings and accuracy issues. | 28th Jan 1930 | Box 59 \ 2 Scan004 | |
| Typed document page discussing the adjustment of mileage readings. | 30th Jan 1930 | Box 59 \ 2 Scan005 | |
| Recommendation to alter A.T. speedometer internal gearing to improve accuracy due to temperature and tyre pressure issues. | 30th Jan 1930 | Box 59 \ 2 Scan006 | |
| Query regarding the effect of low tyre pressure on the figure for wheel revolutions per mile. | 1st Feb 1930 | Box 59 \ 2 Scan007 | |
| Tests and recommendations for A.T. Speedometers. | 3rd Feb 1930 | Box 59 \ 2 Scan008 | |
| A.T. Speedometer data sheet with calculations for Phantom II and 20 HP models. | 3rd Feb 1930 | Box 59 \ 2 Scan009 | |
| Instrument testing, focusing on temperature errors, magnetism, and potential adjustments. | 3rd Feb 1930 | Box 59 \ 2 Scan010 | |
| The testing and calibration of an A.T. Speedometer. | 3rd Feb 1930 | Box 59 \ 2 Scan011 | |
| Report showing the effect of low tyre pressure on wheel revolutions per mile for speedometer readings. | 4th Feb 1930 | Box 59 \ 2 Scan012 | |
| Request to test a speedometer for a 14-GIV model during a 10,000-mile test to check for magnetism loss. | 6th Feb 1930 | Box 59 \ 2 Scan013 | |
| Notes on the gear ratio for an A.T. Speedometer, model A.677. | 6th Feb 1930 | Box 59 \ 2 Scan014 | |
| Sending two speedometers to the A.T. Speedometer Co. Ltd. to have their ratios altered. | 17th Feb 1930 | Box 59 \ 2 Scan015 | |
| Letter to A.T. Speedometer Co. Ltd. regarding the alteration of two speedometers. | 17th Feb 1930 | Box 59 \ 2 Scan016 | |
| Instruction to ask the A.T. Speedometer Co.Ltd. to proceed with work as outlined in an attached letter. | 27th Feb 1930 | Box 59 \ 2 Scan017 | |
| Test report for an A.T. Speedometer allotted to a 10,000-mile test chassis, detailing temperature-based reading variations. | 18th Feb 1930 | Box 59 \ 2 Scan018 | |
| Letter to A.T. Speedometer Co. Ltd. regarding an incorrectly ordered speedometer casing and requesting an urgent fix. | 9th Apr 1930 | Box 59 \ 2 Scan019 | |
| Urgent request to the Stores to despatch an A.T. Speedometer for casing alteration for a left-hand drive car. | 9th Apr 1930 | Box 59 \ 2 Scan020 | |
| Letter from A.T. Speedometer Co. Ltd. confirming an order change to a 'Bezel' type instrument. | 11th Apr 1930 | Box 59 \ 2 Scan021 | |
| Test report on A.T. speedometers No. C.296 & C.278, detailing performance and suitability on a 22-EX vehicle. | 15th Apr 1930 | Box 59 \ 2 Scan022 | |
| Calculation and diagram for speedometer drive gearing on a PII model. | 16th Apr 1930 | Box 59 \ 2 Scan023 | |
| Letter to A.T. Speedometer Co. returning two speedometers for alteration as their miles/hour reading is incorrect. | 16th Apr 1930 | Box 59 \ 2 Scan024 | |
| Sending two speedometers to the A.T. Speedometer Co. for alteration. | 16th Apr 1930 | Box 59 \ 2 Scan025 | |
| Directing that all correspondence regarding the A.T. Speedometer be sent to a specific department due to its classification as an electrical instrument. | 25th Apr 1930 | Box 59 \ 2 Scan026 | |
| Check of revolutions per mile for a speedometer. | 16th May 1930 | Box 59 \ 2 Scan027 | |
| Test record for a speedometer, showing readings at various temperatures. | 3rd Jun 1929 | Box 59 \ 2 Scan028 | |
| Laboratory check and temperature performance analysis of an A.T. Speedometer for the 20/25 HP model. | 20th May 1930 | Box 59 \ 2 Scan029 | |
| Instrument's performance, noting a slight over-reading due to a drive speed mismatch. | 30th May 1930 | Box 59 \ 2 Scan030 | |
| Notification regarding the updated speedometer calibration for the 20/25 HP chassis. | 22th May 1930 | Box 59 \ 2 Scan031 | |
| Test record for checking the revolutions per mile of a speedometer. | 27th May 1930 | Box 59 \ 2 Scan032 | |
| Test record for an A.T. speedometer, showing readings at various temperatures. | 27th May 1930 | Box 59 \ 2 Scan033 | |
| Request for laboratory testing of two A.T. speedometers after 10,000 miles of running. | 31th May 1930 | Box 59 \ 2 Scan034 | |
| Bench test results for a Phantom II A.T. Speedometer showing speed indications at various temperatures. | 4th Jun 1930 | Box 59 \ 2 Scan035 | |
| Continued analysis of speed and distance instrument accuracy based on tyre revolutions and speed. | 4th Jun 1930 | Box 59 \ 2 Scan036 | |
| A.T. speedometer test sheet recording readings at various temperatures. | 20th Jun 1930 | Box 59 \ 2 Scan037 | |
| Request to arrange for the speedometer from chassis 18-GIV to be sent to the laboratory for testing. | 23th Jun 1930 | Box 59 \ 2 Scan038 | |
| Customer complaints about fast-reading speedometers on the Phantom II, detailing test results for different calibrations. | 23th Jun 1930 | Box 59 \ 2 Scan039 | |
| The alteration of speedometers for Phantom II cars with specific tyres and wheels. | 24th Jun 1930 | Box 59 \ 2 Scan040 | |
| Test results for an A.T. Speedometer after a 10,000-mile run, showing readings at various temperatures. | 25th Jun 1930 | Box 59 \ 2 Scan041 | |
| Letter chasing the return of two modified speedometers from A.T. Speedometer Co. Ltd. | 27th Jun 1930 | Box 59 \ 2 Scan042 | |
| Letter from A.T. Speedometer Co. Ltd. regarding the return of two speedometers. | 30th Jun 1930 | Box 59 \ 2 Scan043 | |
| Agreement with the A.T. Company regarding speedometer and odometer settings and tolerances. | 4th Jul 1930 | Box 59 \ 2 Scan044 | |
| Test record for an A.T. Speedometer, detailing performance at various temperatures. | 9th Jul 1930 | Box 59 \ 2 Scan045 | |
| Test record for an A.T. speedometer, showing readings at various temperatures after 10,000 miles. | 9th Jul 1930 | Box 59 \ 2 Scan046 | |
| Bench test results for an A.T. Speedometer from chassis 19-EX, showing MPH readings at various temperatures. | 1st Jul 1930 | Box 59 \ 2 Scan047 | |
| Inquiry regarding a 16% increased reading from instrument No. A.677 N.800 after a 10,000-mile test. | 1st Jul 1930 | Box 59 \ 2 Scan048 | |
| Test report on an A.T. Speedometer following a 10,000-mile run, investigating an increase in readings. | 11th Jul 1930 | Box 59 \ 2 Scan049 | |
| The results of testing a new speedometer on the Brooklands track. | 14th Aug 1930 | Box 59 \ 2 Scan050 | |
| Comparison of speedometer and mileage recording accuracy between American cars and Rolls Royce vehicles. | 14th Aug 1930 | Box 59 \ 2 Scan051 | |
| Considerations for A.T. speedometers, focusing on the factors affecting the drive mechanism. | 9th Aug 1930 | Box 59 \ 2 Scan052 | |
| The effect of centrifugal force on tyre revolutions and mile counter calibration. | 9th Aug 1930 | Box 59 \ 2 Scan053 | |
| Continued discussion on instrument error calculations and the working principle of speed indicators. | 19th Aug 1930 | Box 59 \ 2 Scan054 | |
| The principles of speed measurement, considering temperature effects on instrument accuracy and calibration. | 9th Aug 1930 | Box 59 \ 2 Scan055 | |
| Analysis of speedometer reading inaccuracies, investigating potential causes such as magnetism and control spring power. | 9th Aug 1930 | Box 59 \ 2 Scan056 | |
| Continued report on speedometer testing, discussing errors related to temperature and control spring weakening. | 9th Aug 1930 | Box 59 \ 2 Scan057 | |
| Confidential memo discussing speedometer accuracy in relation to tyre diameter changes at high speeds. | 21th Aug 1930 | Box 59 \ 2 Scan058 | |
| Speedometer and mileage recorder calibration to account for the effective increase in tyre diameter with speed. | 25th Mar 1930 | Box 59 \ 2 Scan059 | |
| Proposing a meeting in Derby to discuss speedometers. | 26th Aug 1930 | Box 59 \ 2 Scan060 | |
| Letter to A.T. Speedometer Co. regarding potential inaccuracies in their instruments. | 27th Aug 1930 | Box 59 \ 2 Scan061 | |
| Testing of A.T. speedometers for reading inaccuracies after 10,000-mile runs. | 28th Aug 1930 | Box 59 \ 2 Scan062 | |
| Letter from The A.T. Speedometer Co., Ltd. responding to a query about a speedometer giving an increased reading. | 29th Aug 1930 | Box 59 \ 2 Scan063 | |
| Factors affecting speedometer drive revolutions, such as tyre size, inflation, and vehicle speed. | 4th Sep 1930 | Box 59 \ 2 Scan064 | |
| Continued report detailing calculations for speedometer calibration considering tyre inflation and wheel revolutions. | 1st Sep 1930 | Box 59 \ 2 Scan065 | |
| The calibration and accuracy of the speedometer and mile counter under various operating conditions. | 1st Sep 1930 | Box 59 \ 2 Scan066 | |
| The centrifugal effect of tyres at high speed and its impact on speed and mileage readings. | 1st Sep 1930 | Box 59 \ 2 Scan067 | |
| Compression of instrument scales for speeds above 40 mph. | 1st Sep 1930 | Box 59 \ 2 Scan068 | |
| Electrical experimental record sheet for a 10,000-mile test of an AT Speedometer. | 10th Feb 1930 | Box 59 \ 2 Scan069 | |
| Supply of horns, clocks, and speedometers for L.H.Phantom II Chassis for the American market. | 1st Sep 1930 | Box 59 \ 2 Scan070 | |
| Sourcing and standardisation of electric clocks and speedometers for the Left-Hand Phantom II Chassis. | 5th Sep 1930 | Box 59 \ 2 Scan071 | |
| Typed memorandum regarding the complications and proposed solution for A.T. Speedometers. | 9th Sep 1930 | Box 59 \ 2 Scan072 | |
| Request for up-to-date data concerning A.T. speedometers, focusing on road wheel revolutions per mile under various conditions. | 12th Sep 1930 | Box 59 \ 2 Scan073 | |
| The necessary compression of the speed scale for A.T. speedometers. | 12th Sep 1930 | Box 59 \ 2 Scan074 | |
| Requesting an investigation into A.T. Speedometers to gather up-to-date information for final recommendations. | 3rd Sep 1930 | Box 59 \ 2 Scan075 | |
| Complaint about receiving an obsolete 40/50 speedometer instead of a standard one, causing delays. | 7th Oct 1930 | Box 59 \ 2 Scan076 | |
| Response to a complaint regarding the delivery of an obsolete A.T. 40/50 Speedometer. | 10th Oct 1930 | Box 59 \ 2 Scan077 | |
| A.T. Speedometer test record showing performance at different temperatures. | 8th Oct 1930 | Box 59 \ 2 Scan078 | |
| Test record for an A.T. Speedometer, detailing its performance and accuracy at various temperatures. | 9th Oct 1930 | Box 59 \ 2 Scan079 | |
| Experimental record sheet for an A.T. Speedometer with a small type dial. | 11th Oct 1930 | Box 59 \ 2 Scan080 | |
| Test report for an A.T. Speedometer from chassis 18-GIV after a 10,000-mile test. | 3rd Oct 1930 | Box 59 \ 2 Scan081 | |
| Investigation into the increased reading of an A.T. Speedometer and its performance at various temperatures. | 3rd Oct 1930 | Box 59 \ 2 Scan082 | |
| Continued note on instrument readings for mileage and speed based on tyre revolutions per mile. | 3rd Oct 1930 | Box 59 \ 2 Scan083 | |
| Test record for an A.T. speedometer, showing MPH readings at various temperatures. | 27th Oct 1930 | Box 59 \ 2 Scan084 | |
| Test report on an A.T. Speedometer C.83 from chassis 20-EX, detailing reading discrepancies and temperature effects. | 31th Oct 1930 | Box 59 \ 2 Scan085 | |
| Technical memorandum discussing failures and issues with speedometers, particularly the trip gear. | 1st Nov 1930 | Box 59 \ 2 Scan086 | |
| Seeking agreement on a proposed letter to The A.T. Speedometer Co. regarding mechanical complaints. | 17th Nov 1930 | Box 59 \ 2 Scan087 | |
| Letter to the A.T. Speedometer Co. regarding failures with speedometer trip gears. | 17th Nov 1930 | Box 59 \ 2 Scan088 | |
| Continued letter asking for a proposal to overcome unsatisfactory defects. | 17th Nov 1930 | Box 59 \ 2 Scan089 | |
| Letter from The A.T. Speedometer Co., Ltd. acknowledging a previous letter and advising that the points raised are being investigated. | 19th Nov 1930 | Box 59 \ 2 Scan090 | |
| Query regarding the revolutions per mile for standard P.2. and 20/25 A.T. speedometers. | 3rd Dec 1930 | Box 59 \ 2 Scan091 | |
| Technical note on the calibration of A.T. Speedometers for Phantom II and 20/25 HP chassis. | 4th Dec 1930 | Box 59 \ 2 Scan092 | |
| Letter to A.T. Speedometer Co. enquiring about drive revolution specifications and noting discrepancies. | 11th Dec 1930 | Box 59 \ 2 Scan093 | |
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