| Description | Date | Identifier | |
| Letter from Alfred Lalli, a mechanical engineer, offering Eyquem sparking plugs for aeroplane engines for testing. | 13th Jul 1927 | Box 33 \ 3 Scan254 | |
| Leakage tests on K.L.G. and Champion sparking plugs intended for use with leaded fuel. | 15th Sep 1927 | Box 33 \ 3 Scan255 | |
| Investigation into engine pinking caused by a fine powder deposit on spark plugs and a proposal to update cleaning instructions. | 22th Sep 1927 | Box 33 \ 3 Scan256 | |
| Request to test spark plugs from a Swiss manufacturer and provide a report. | 14th Oct 1929 | Box 33 \ 3 Scan257 | |
| Query regarding condensation issues with Aero Engine ignition plugs on the Condor engine and 20-HP cars. | 24th Nov 1927 | Box 33 \ 3 Scan258 | |
| Extract questioning why English makers cannot produce porcelain ignition plugs equal to Champion for aero engines. | 28th Nov 1927 | Box 33 \ 3 Scan259 | |
| Letter from C.G. Spencer & Sons Ltd. apologising for a bad report on plugs tested on an Aero Engine. | 16th Dec 1927 | Box 33 \ 3 Scan260 | |
| Circular letter regarding sparking plugs used on engine type tests. | 10th Jan 1928 | Box 33 \ 3 Scan261 | |
| Circular letter detailing the standard procedure for using and testing sparking plugs during engine type tests. | 8th Dec 1925 | Box 33 \ 3 Scan262 | |
| Summary of sparking plug trouble experienced during an F.12 type test. | 20th Jan 1928 | Box 33 \ 3 Scan263 | |
| Sales letter from Desmo Ltd. offering their 'Flexi Plug Cover' for aero engines, including a sample for testing. | 8th Aug 1928 | Box 33 \ 3 Scan264 | |
| Spark plug development at Farnborough, discussing overheating issues and proposing a cooling solution. | 1st Oct 1928 | Box 33 \ 3 Scan265 | |
| Unsatisfactory bonding wire clips on armoured cables for F engines, with suggestions for improvement. | 20th Oct 1928 | Box 33 \ 3 Scan266 | |
| Quoting a letter from J. A. Stevens Ltd. regarding the dispatch of twenty-four platinum-tipped spark plugs. | 1st Dec 1928 | Box 33 \ 3 Scan267 | |
| Letter regarding the supply and testing of special plugs from Germany for Mr. Hives. | 1st Dec 1928 | Box 33 \ 3 Scan268 | |
| Outlining the procedure for requisitioning spare parts for Air Ministry engines. | 19th Jan 1929 | Box 33 \ 3 Scan269 | |
| Return of Jupiter sparking plugs due to a lack of interest in testing them. | 21th Feb 1929 | Box 33 \ 3 Scan270 | |
| Analysis of ignition plug temperature, pre-ignition, and cooling in an aluminium cylinder head. | 10th Apr 1929 | Box 33 \ 3 Scan271 | |
| Engine design modifications, including compression ratio, plug cooling, and ignition advance. | 10th Apr 1929 | Box 33 \ 3 Scan272 | |
| Conclusions from a cylinder head test, proposing modifications to the combustion chamber, plug, and compression ratio. | 10th Apr 1929 | Box 33 \ 3 Scan273 | |
| Page from a publication featuring letters discussing the merits of long versus short stroke engines. | 23th Nov 1912 | Box 33 \ 4 Scan001 | |
| Extract from 'The Autocar' magazine discussing engine forces, pressure diagrams, and the debate between long and short stroke engines. | 4th Feb 1915 | Box 33 \ 4 Scan002 | |
| Method for checking and calibrating speedometers. | 23th Aug 1913 | Box 33 \ 4 Scan003 | |
| Customer's request for an engine revolution counter and an alternative proposal for a colour-coded speedometer. | 17th Dec 1912 | Box 33 \ 4 Scan004 | |
| Specification for a speedometer drive system using a raw hide belt and flexible shaft for a standard car. | 18th Aug 1916 | Box 33 \ 4 Scan005 | |
| Extract discussing issues with the speed indicator belt and mileage recorder on chassis no. 7-CA. | 9th Sep 1916 | Box 33 \ 4 Scan006 | |
| New speedometer drive using a pulley and the optimal placement of the battery on the chassis. | 10th Jan 1919 | Box 33 \ 4 Scan007 | |
| Chassis wiring scheme and sending a dismantled round tube radiator matrix sample for examination. | 10th Jan 1919 | Box 33 \ 4 Scan008 | |
| New design for a speedometer drive, proposing a pulley and belt system driven from the propeller shaft. | 10th Jan 1919 | Box 33 \ 4 Scan009 | |
| Performance of a Waltham speedometer, noting its moving scale design as a drawback, and recommending a trial. | 13th Oct 1920 | Box 33 \ 4 Scan010 | |
| Letter from Portland Motor Co. Ltd. proposing a meeting to demonstrate a patented speedometer with a gear change indicator. | 1st Apr 1924 | Box 33 \ 4 Scan011 | |
| Letter to The Portland Garage regarding a proposed instrument by a Mr. Braithwaite, requesting sketches instead of a visit. | 2nd Apr 1934 | Box 33 \ 4 Scan012 | |
| Letter enclosing a sketch and photographs of a protected mechanism related to a speedometer and gear ratios. | 10th Apr 1934 | Box 33 \ 4 Scan013 | |
| The conclusion of a handwritten letter regarding the return of drawings and photographs. | 11th Apr 1924 | Box 33 \ 4 Scan014 | |
| Letter declining a proposal for an instrument and suggesting the inventor approach accessory makers. | 11th Apr 1924 | Box 33 \ 4 Scan015 | |
| Outstanding 1921 invoice for a Watford Speedometer and Clock. | 17th Sep 1924 | Box 33 \ 4 Scan016 | |
| Order to be sent to Messrs. North's for a Watford Speedometer and Clock. | 18th Sep 1924 | Box 33 \ 4 Scan017 | |
| Complaints about A.T. speedometers and the decision to test alternative Smith speedometers. | 16th Apr 1925 | Box 33 \ 4 Scan018 | |
| Hand Tachograph & Speed Indicator made by the James Jacquet Company of Switzerland. | 16th Mar 1925 | Box 33 \ 4 Scan019 | |
| New Cooper-Stewart speedometer which uses figures instead of a needle, offered for testing. | 16th Apr 1925 | Box 33 \ 4 Scan020 | |
| Delivery of a new Cooper-Stewart speedometer. | 22th Apr 1925 | Box 33 \ 4 Scan021 | |
| Decision not to test or adopt the Cooper Stewart speedometer. | 27th Apr 1925 | Box 33 \ 4 Scan022 | |
| Return of a Cooper-Stewart speedometer without testing. | 30th Apr 1925 | Box 33 \ 4 Scan023 | |
| Sending a Cooper-Stewart Speedometer back to the manufacturer. | 8th May 1925 | Box 33 \ 4 Scan024 | |
| Letter to Cooper-Stewart Engineering Co. Ltd. regarding the return of a loaned speedometer and fittings. | 8th May 1925 | Box 33 \ 4 Scan025 | |
| Outer covering on flexible drives used for speedometers. | 8th Jul 1925 | Box 33 \ 4 Scan026 | |
| Potential testing of new instruments from the British Instrument Company Ltd. | 7th Dec 1926 | Box 33 \ 4 Scan027 | |
| Speedometer drive cable standards, fracture issues, and fitting improvements. | 20th May 1927 | Box 33 \ 4 Scan028 | |
| Urgent chassis test requiring discs for Dunlop wire wheels. | 17th Jun 1915 | Box 33 \ 4 Scan029 | |
| Notification regarding the receipt of a set of nickel-finished Wire Wheel Discs available at the Stores. | 18th Oct 1915 | Box 33 \ 4 Scan030 | |
| Arrangements for fitting two different types of aluminium discs to wire wheels for comparative testing. | 30th Apr 1919 | Box 33 \ 4 Scan031 | |
| Policy on developing or recommending disc covers for wire wheels. | 29th Sep 1919 | Box 33 \ 4 Scan032 | |
| Requesting a pair of wheels to have discs fitted for testing on a car. | 2nd Aug 1920 | Box 33 \ 4 Scan033 | |
| Fitting improved discs to a wheel for examination. | 27th Jul 1920 | Box 33 \ 4 Scan034 | |
| Requesting a pair of wheels to have discs fitted for chassis X 3374. | 2nd Aug 1920 | Box 33 \ 4 Scan035 | |
| 'Goshawk 11' front axle design, specifically concerning vertical pivots and wheel compatibility. | 16th Feb 1921 | Box 33 \ 4 Scan036 | |
| Cover letter attaching a letter from Cornercroft Ltd. and requesting remarks on a suggestion within it. | 28th Sep 1921 | Box 33 \ 4 Scan037 | |
| Letter from Cornercroft Ltd. regarding the supply and testing of ACE Patent Wheel Discs on a car. | 23th Sep 1921 | Box 33 \ 4 Scan038 | |
| Dunlop Wheel fitted with patent discs by Cornercroft Limited. | 21th Nov 1921 | Box 33 \ 4 Scan039 | |
| Copy of a letter from Cornercroft Limited regarding the fitting of ACE Patent Seamless Discs to a Dunlop E. type wheel. | 18th Nov 1921 | Box 33 \ 4 Scan040 | |
| Dunlop Wheel sent to Messrs. Cornercroft Limited for fitting with patent discs. | 24th Nov 1921 | Box 33 \ 4 Scan041 | |
| Unsatisfactory performance of disc wheels on 20 HP cars, citing issues like noisy axles and general booming. | 2nd Mar 1923 | Box 33 \ 4 Scan042 | |
| Requesting a test of Dunlop Discs as a potential improvement over the 'Barker' Discs. | 9th May 1923 | Box 33 \ 4 Scan043 | |
| Company's refusal to test or recommend Dunlop Discs. | 24th May 1923 | Box 33 \ 4 Scan044 | |
| New Dunlop wheel discs and a proposal to send a set for inspection. | 28th May 1923 | Box 33 \ 4 Scan045 | |
| Dispatch of 5 Dunlop wheel discs to stores. | 1st Jun 1923 | Box 33 \ 4 Scan046 | |
| Whether wheel discs make cars noisier and if further tests are needed. | 17th Sep 1924 | Box 33 \ 4 Scan047 | |
| Letter from Barker & Co. (Coachbuilders) to Mr. Johnson regarding noise levels of their wheel discs. | 23th Sep 1924 | Box 33 \ 4 Scan048 | |
| The advantages and disadvantages of fitting discs to wire wheels, focusing on noise amplification and rusting spokes. | 23th Sep 1924 | Box 33 \ 4 Scan049 | |
| Communication regarding a letter received from Cornercraft Ltd. concerning testing a set of Wire Wheel Discs. | 9th Dec 1927 | Box 33 \ 4 Scan050 | |
| Promotional leaflet for 'Super Ace' patent wheel discs. | 7th Dec 1927 | Box 33 \ 4 Scan051 | |
| Sales letter from Cornercroft Limited promoting their Ace Super Wheel Discs for use on Rolls-Royce cars. | 7th Dec 1927 | Box 33 \ 4 Scan052 | |
| Page two of a letter from Cornercroft Limited regarding a business proposal and a planned visit to Derby. | 7th Dec 1927 | Box 33 \ 4 Scan053 | |
| The receipt of 'Ace' discs, with a query about the quantity of spokes and correctness of the nipples. | 25th Jan 1928 | Box 33 \ 4 Scan054 | |
| The disposal of surplus blue painted wheel discs no longer required for the Baden & Prague Propaganda Car, chassis 29-CL. | 16th Aug 1928 | Box 33 \ 4 Scan055 | |
| Request for the return of wheel discs from Lillie Hall. | 20th Aug 1928 | Box 33 \ 4 Scan056 | |
| The return of wheel discs from chassis 29-CL, the Baden & Prague Propaganda Car, to Derby for stock. | 23th Aug 1928 | Box 33 \ 4 Scan057 | |
| Query regarding the performance impact of fitting wheel discs to a Continental Trials car, chassis 31-GX. | 9th Jun 1931 | Box 33 \ 4 Scan058 | |
| Comparative performance of disc wheels versus wire wheels at high speeds. | 10th Jun 1931 | Box 33 \ 4 Scan059 | |
| Dynamometer readings after altering the cam wheel timing on chassis 1144. | 4th Oct 1909 | Box 33 \ 4 Scan060 | |
| Graph and table showing performance curves with different engine timing settings for a 64lbs compression engine. | 5th Jul 1910 | Box 33 \ 4 Scan061 | |
| Graph showing timing curves for the 64 lbs Compression Engine J 7.10. | 5th Jul 1910 | Box 33 \ 4 Scan062 | |
| Graph and table showing timing curves for a 64 lbs compression engine, plotting horsepower against RPM. | 5th Jul 1910 | Box 33 \ 4 Scan063 | |
| Engine power and performance test results for chassis 1510. | 22th Feb 1911 | Box 33 \ 4 Scan064 | |
| Valve lift diagrams and proposing modifications to improve engine performance. | 21th Feb 1916 | Box 33 \ 4 Scan065 | |
| Recommendation to slightly retard engine valve timing for improved power. | 14th Jun 1916 | Box 33 \ 4 Scan066 | |
| Requesting remarks on an attached letter from Springfield regarding valve timing. | 19th Aug 1921 | Box 33 \ 4 Scan067 | |
| Discrepancy in valve timing and requesting revised figures and permissible variations. | 1st Aug 1921 | Box 33 \ 4 Scan068 | |
| Discrepancy between drawing specifications and test figures for engine valve timing. | 1st Aug 1921 | Box 33 \ 4 Scan069 | |
| Faults with camshaft and valve timing and proposing an inspection to establish standard limits. | 24th Aug 1921 | Box 33 \ 4 Scan070 | |
| Limits and accuracy of engine valve timing for the 40/50 chassis. | 9th Sep 1921 | Box 33 \ 4 Scan071 | |
| Modifications to the valve timing for the Goshawk engine. | 7th Jun 1923 | Box 33 \ 4 Scan072 | |
| Modifications to the timing of the Goshawk 11 engine, specifically the exhaust and inlet cams. | 13th Jul 1923 | Box 33 \ 4 Scan073 | |
| Determining the accuracy of checking valve timing by hand versus when the engine is running. | 16th Aug 1923 | Box 33 \ 4 Scan074 | |
| Engine valve timing variations and gear rattles. | 9th Sep 1923 | Box 33 \ 4 Scan075 | |
| Unsatisfactory method for checking engine timing on Series III Condors and proposing solutions. | 5th Feb 1924 | Box 33 \ 4 Scan076 | |
| Test bench results comparing B.HP output and valve timings for 110° and standard camshafts. | 29th Apr 1924 | Box 33 \ 4 Scan077 | |
| Confirming verbal instructions for new valve lift curves and cam alterations. | 21th Jul 1926 | Box 33 \ 4 Scan078 | |
| Adjustments to valve timing and improvements to valve spring design. | 1st Aug 1926 | Box 33 \ 4 Scan079 | |
| Duplex and triple valve spring designs, proposing a double spigot to prevent the springs from rubbing together. | 5th Sep 1926 | Box 33 \ 4 Scan080 | |
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