| Description | Date | Identifier | |
| Requesting an official order be placed with Dobbie McInnes and Clyde Ltd. for six valve discs for a Farnborough Indicator. | 6th Mar 1939 | Box 134 \ 1 scan0137 | |
| Letter from the Experimental Department requesting spare valve discs and material information. | 6th Mar 1939 | Box 134 \ 1 scan0138 | |
| Status update memo on various components for the Single Cylinder Bentley project. | 11th Mar 1939 | Box 134 \ 1 scan0139 | |
| Order request for an 'A' type indicator valve and six spare valve discs for a Single Cylinder Bentley. | 17th Mar 1939 | Box 134 \ 1 scan0140 | |
| Typed letter requesting the urgent supply of a Farnborough Indicator valve and spare parts. | 17th Mar 1939 | Box 134 \ 1 scan0141 | |
| Required drawings and parts for modifying a Bentley 11 cylinder head. | 13th Mar 1939 | Box 134 \ 1 scan0142 | |
| Instructing the development and testing of new cylinder and piston designs for a Bentley S/C unit. | 17th Mar 1939 | Box 134 \ 1 scan0143 | |
| Analysis of a direct injection combustion chamber and multi-hole nozzle from the National Gas & Oil Engine Co. | 18th Mar 1939 | Box 134 \ 1 scan0144 | |
| Continuation of notes on engine nozzles, shrouded valves, fuel pumps, and superchargers. | 18th Mar 1939 | Box 134 \ 1 scan0145 | |
| The order of twelve corrujoint washers for a Single Cylinder Bentley. | 23th Mar 1939 | Box 134 \ 1 scan0146 | |
| The requirements for adapting a single-cylinder Bentley engine head for testing various compression ratios and throat sizes. | 25th Mar 1939 | Box 134 \ 1 scan0147 | |
| Outstanding and delayed parts for a single cylinder Bentley unit. | 27th Mar 1939 | Box 134 \ 1 scan0148 | |
| Requesting to fit up a charging plant on a test bed for a Bentley S/C Unit. | 30th Mar 1939 | Box 134 \ 1 scan0149 | |
| Listing outstanding jobs for the single cylinder unit and requesting estimated completion dates. | 30th Mar 1939 | Box 134 \ 1 scan0150 | |
| General programme of work for a single cylinder unit. | 30th Mar 1939 | Box 134 \ 1 scan0151 | |
| Programme of tests for a single cylinder unit, including coolant, gasket, and new cylinder head evaluations. | 1st Apr 1939 | Box 134 \ 1 scan0152 | |
| Engine testing procedures for fuel consumption, ignition curves, and the effect of distance between the head and piston. | 1st Apr 1939 | Box 134 \ 1 scan0153 | |
| Specification sheet for Beardmore and other railcar engines. | 4th Apr 1939 | Box 134 \ 1 scan0154 | |
| List of engine specifications used by various international railway companies. | 4th Apr 1939 | Box 134 \ 1 scan0155 | |
| The investigation of detonation indication on single cylinder units using a Cathode-ray unit. | 12th Apr 1939 | Box 134 \ 1 scan0156 | |
| Asking for the current status of various engine components and systems. | 19th Apr 1939 | Box 134 \ 1 scan0157 | |
| Request to mark up a print of a Bentley single cylinder head to conform to the design of a Wraith cylinder head. | 26th Apr 1939 | Box 134 \ 1 scan0158 | |
| Request to modify an existing Bentley Single Cylinder Head to conform to Wraith lll specifications. | 27th Apr 1939 | Box 134 \ 1 scan0159 | |
| Design for 'dieselising' the S/C unit, including the cylinder head and piston arrangement. | 16th May 1939 | Box 134 \ 1 scan0160 | |
| Request to investigate the design changes required to convert a 4¼-litre high-power engine into a 3½-litre unit. | 17th May 1939 | Box 134 \ 1 scan0161 | |
| Seeking payment approval for an invoice for a die from The Southwark Manufacturing Co. | 18th May 1939 | Box 134 \ 1 scan0162 | |
| Agreeing to pass the cost of Corrujoint dies bought from The Southwark Manufacturing Co. for payment. | 23th May 1939 | Box 134 \ 1 scan0163 | |
| The status of the 3¼ bore High Power Engine and whether castings can be instructed. | 25th Sep 1939 | Box 134 \ 1 scan0164 | |
| The investigation and redesign of high power cylinder heads. | 12th Oct 1939 | Box 134 \ 1 scan0165 | |
| Comparison of engine head modifications and their performance characteristics. | 12th Oct 1939 | Box 134 \ 1 scan0166 | |
| The development and testing of a modified cylinder head, detailing iterative changes to its compression ratio and performance characteristics. | 12th Oct 1939 | Box 134 \ 1 scan0167 | |
| Blueprint illustrating three stages of modification to a mechanical component, showing plan and cross-section views. | 26th May 1939 | Box 134 \ 1 scan0168 | |
| Performance comparison graph for a B.60 cylinder head. | 26th May 1939 | Box 134 \ 1 scan0169 | |
| Performance graph comparing cylinder head configurations for the B.60 No. 3 unit. | 26th May 1939 | Box 134 \ 1 scan0170 | |
| Performance comparison graph for a B.60 cylinder head under various configurations. | 26th May 1939 | Box 134 \ 1 scan0171 | |
| Specification sheet for a White 12-cylinder horizontally opposed bus engine. | 2nd Dec 1939 | Box 134 \ 1 scan0172 | |
| Issue of excessive blow-by in high power engines, its effects, and proposed solutions for the piston ring set-up. | 2nd Dec 1939 | Box 134 \ 1 scan0173 | |
| List of questions regarding high power engine performance, cylinder wear, and blow-by. | 2nd Dec 1939 | Box 134 \ 1 scan0174 | |
| Plating recommendations for C.I. liners to be cast in aluminium brake drums. | 3rd Jan 1941 | Box 134 \ 1 scan0175 | |
| Letter from The Stainless Spinning Works confirming the despatch of Plate Springs RG.2909. | 26th Feb 1942 | Box 134 \ 1 scan0176 | |
| Short typed message regarding an arrival by road at a specific time. | 15th Mar 1940 | Box 134 \ 1 scan0177 | |
| Message to NIPSA in Bury, Lancashire, arranging a meeting to discuss engine design problems. | 14th May 1940 | Box 134 \ 1 scan0178 | |
| Brief typed telex message arranging a meeting for the following Friday. | 5th Jun 1940 | Box 134 \ 1 scan0179 | |
| Telegram confirming the arrival details for Mr. Robotham. | 10th Oct 1940 | Box 134 \ 1 scan0180 | |
| Telegram received by telephone regarding an arrival for the attention of Robotham. | 1st Oct 1940 | Box 134 \ 1 scan0181 | |
| Telegram received by telephone confirming the arrival of Mr. Robotham. | 1st Oct 1940 | Box 134 \ 1 scan0182 | |
| Technical report on Mercedes Benz dry cylinder liners. | 3rd Oct 1940 | Box 134 \ 1 scan0183 | |
| Sketch of a Mercedes-Benz dry liner with dimensions and material hardness. | 3rd Oct 1940 | Box 134 \ 1 scan0184 | |
| Advantages and disadvantages of two types of high power cylinder heads. | 9th Sep 1940 | Box 134 \ 1 scan0185 | |
| Research into improving engine volumetric efficiency and power output. | 15th Jan 1944 | Box 134 \ 1 scan0186 | |
| The creation of a separate file for letters concerning Aspin Cylinder Heads. | 13th Mar 1944 | Box 134 \ 1 scan0187 | |
| Letter from F. M. Aspin & Co. Ltd. to W. A. Robotham regarding engine developments. | 13th Mar 1944 | Box 134 \ 1 scan0188 | |
| Letter declining an offer to convert a Bentley engine and putting the project on hold. | 8th Mar 1944 | Box 134 \ 1 scan0189 | |
| Letter from F. M. Aspin & Co. Ltd. to W. A. Robotham acknowledging a letter and offering to undertake a complete job. | 28th Feb 1944 | Box 134 \ 1 scan0190 | |
| Letter postponing work on the Aspin head experiment project for various reasons. | 23th Feb 1944 | Box 134 \ 1 scan0191 | |
| Letter from F. M. Aspin & Co. Ltd. to W. A. Robotham regarding a previously sent letter and power curve. | 21th Feb 1944 | Box 134 \ 1 scan0192 | |
| Letter from F.M. Aspin & Co. discussing a cylinder head collaboration and engine performance metrics. | 5th Feb 1944 | Box 134 \ 1 scan0193 | |
| Letter from F. M. Aspin & Co. Ltd. detailing engine performance after 1,000 power hours and a recent facility expansion. | 22th Sep 1943 | Box 134 \ 1 scan0194 | |
| Performance curve graph for an Engine Series TA6 6 Cylinder with atmospheric induction. | 22th Sep 1943 | Box 134 \ 1 scan0195 | |
| Confidential letter to Maurice Platt of Vauxhall Motors regarding the Aspin head and valve development. | 21th Feb 1944 | Box 134 \ 1 scan0196 | |
| Confidential letter from Vauxhall Motors discussing test results and failures of various Aspin project engines. | 14th Feb 1944 | Box 134 \ 1 scan0197 | |
| Report page detailing the performance, modifications, and issues with a converted Vauxhall Ten engine featuring an Aspin rotary valve head. | 14th Feb 1944 | Box 134 \ 1 scan0198 | |
| Concluding page of a letter detailing engine performance metrics and development work since 1940. | 5th Feb 1944 | Box 134 \ 1 scan0199 | |
| Letter from F.M. Aspin & Co. Ltd. to W.A. Robotham discussing the manufacture and performance of a Cylinder Head. | 5th Feb 1944 | Box 134 \ 1 scan0200 | |
| Continuation sheet of a letter from F. M. Aspin & Co. Ltd. discussing engine performance and company expansion. | 22th Sep 1943 | Box 134 \ 1 scan0201 | |
| Performance curve graph for an Engine Series TA 6, a 6-cylinder engine with atmospheric induction. | 22th Sep 1943 | Box 134 \ 1 scan0202 | |
| Letter from Vauxhall Motors concerning tests on an Aspinized Vauxhall engine. | 1st Feb 1944 | Box 134 \ 1 scan0203 | |
| Letter to F.W. Aspin regarding a contract to develop an engine with an Aspin head for the Ministry of Supply. | 31th Jan 1944 | Box 134 \ 1 scan0204 | |
| Secret letter to Maurice Platt of Vauxhall Motors requesting information on an engine produced with Aspin's valve gear. | 29th Jan 1944 | Box 134 \ 1 scan0205 | |
| Letter from Briggs Motor Bodies Limited to W. A. Robotham congratulating him on an appointment and discussing the Aspin Engine. | 12th Nov 1941 | Box 134 \ 1 scan0206 | |
| Graph and diagrams comparing two-stroke engine valve opening areas for various valve designs. | 28th Jun 1940 | Box 134 \ 1 scan0207 | |
| Letter from F.M. Aspin & Co. Ltd. requesting a review of a Centrifugal Supercharger design. | 16th Oct 1940 | Box 134 \ 1 scan0208 | |
| Letter from F.M. Aspin & Co. Ltd. discussing job specifications, drawings, and cost estimates for cylinder components. | 15th Oct 1940 | Box 134 \ 1 scan0209 | |
| Letter declining to disclose development work on centrifugal superchargers. | 18th Oct 1940 | Box 134 \ 1 scan0210 | |
| Letter from F.M. Aspin & Co. Ltd. returning an inadvertently taken Visitor's Pass. | 3rd Oct 1940 | Box 134 \ 1 scan0211 | |
| Requesting the location of a pattern to modify a cylinder block for Aspin's cylinder head. | 25th Sep 1940 | Box 134 \ 1 scan0212 | |
| Agreement to fit an Aspin head to an overhead camshaft Bentley engine. | 15th Sep 1940 | Box 134 \ 1 scan0213 | |
| Patent inquiry for a principle applying acceleration and deceleration to a rotary valve. | 10th Jul 1940 | Box 134 \ 1 scan0214 | |
| Letter from F.M. Aspin & Co. Ltd. acknowledging receipt of a letter and diagram, promising an attractive proposition. | 8th Jul 1940 | Box 134 \ 1 scan0215 | |
| From Rm. to Jnr. discussing a review of the Aspin valve and its potential for engine designs. | 8th Jul 1940 | Box 134 \ 1 scan0216 | |
| Design, performance and mechanical limitations of the Aspin rotary valve. | 6th Jul 1940 | Box 134 \ 1 scan0217 | |
| Letter to F. M. Aspin & Co. Ltd. discussing attempts to determine the orifice coefficient of a valve and port. | 3rd Jul 1940 | Box 134 \ 1 scan0218 | |
| Letter from F.M. Aspin & Co. discussing port design and proposing a flow measurement test against poppet valves. | 29th Jun 1940 | Box 134 \ 1 scan0219 | |
| Continuation sheet of a letter from F. M. Aspin & Co. Ltd. requesting information. | 29th Jun 1940 | Box 134 \ 1 scan0220 | |
| Graph comparing poppet valve and Aspin engine port areas against timing angle in degrees. | 21th Jun 1940 | Box 134 \ 1 scan0221 | |
| Aspin valve design, its poor volumetric efficiency, and potential use in 2-stroke engines. | 28th Jun 1940 | Box 134 \ 1 scan0222 | |
| Letter to Mr. Aspin comparing the breathing capacity of his Aspin valve to a standard poppet valve for aviation engines. | 28th Jun 1940 | Box 134 \ 1 scan0223 | |
| Letter to F.M. Aspin comparing the breathing capacity of his Aspin valve against the standard poppet valve for aviation engines. | 28th Jun 1940 | Box 134 \ 1 scan0224 | |
| Valve timing and design characteristics for the Aspin valve engine. | 21th Jun 1940 | Box 134 \ 1 scan0225 | |
| Comparing the Aspin engine's valve timing and performance against the B.60 and Merlin engines. | 18th Jun 1940 | Box 134 \ 1 scan0226 | |
| Letter from F.M. Aspin & Co. Ltd. enclosing drawing No. C.144 for engine porting and discussing experimental work. | 14th Jun 1940 | Box 134 \ 1 scan0227 | |
| Letter from F.M. Aspin to W.A. Robotham discussing a drawing for engine porting and a valve opening diagram. | 14th Jun 1940 | Box 134 \ 1 scan0228 | |
| Comparison of valve port areas for various engines, including the Aspin valve and the B.60. | 10th Jun 1940 | Box 134 \ 1 scan0229 | |
| Letter to Mr. F. Aspin cancelling a visit and halting development work due to the serious situation in France. | 24th May 1940 | Box 134 \ 1 scan0230 | |
| Cover letter from F. M. Aspin & Co. Ltd. regarding a print of a rotor from an engine. | 23th May 1940 | Box 134 \ 1 scan0231 | |
| Photograph showing a rotor taken from a 4 1/8' bore by 6' stroke engine. | 17th May 1940 | Box 134 \ 1 scan0232 | |
| Design work, challenges, and questions regarding the Aspin engine. | 17th May 1940 | Box 134 \ 1 scan0233 | |
| List of questions and observations regarding engine valve and spark plug performance. | 17th May 1940 | Box 134 \ 1 scan0234 | |
| Declining research on the Aspin Valve Gear due to existing research commitments. | 16th May 1940 | Box 134 \ 1 scan0235 | |
| Visit to Aspin regarding engine conversion, design issues with cylinder stud positioning, and a new layout at Blounts Mill. | 15th May 1940 | Box 134 \ 1 scan0236 | |
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