| Description | Date | Identifier | |
| Valve spring failure during testing on a Bentley unit. | 22th Feb 1937 | Box 158 \ 4 scan0123 | |
| Correspondence with The Tempered Spring Co. regarding the receipt and outstanding order of springs. | 22th Feb 1937 | Box 158 \ 4 scan0124 | |
| Official order to be placed with the Tempered Spring Co. | 22th Feb 1937 | Box 158 \ 4 scan0125 | |
| Letter from the Experimental Department to H.S. Burn Esq. regarding the 'Cross Rotary Valve'. | 23th Feb 1937 | Box 158 \ 4 scan0126 | |
| Letter from The Imperial Tobacco Company regarding arranging an interview to discuss the Cross Rotary Valve Gear. | 24th Feb 1937 | Box 158 \ 4 scan0127 | |
| Micro-examination report on a Bentley valve spring, concluding a mechanical failure rather than a material fault. | 26th Feb 1937 | Box 158 \ 4 scan0128 | |
| Clarifying the facts regarding the testing and performance of different types and materials of valve springs. | 4th May 1937 | Box 158 \ 4 scan0129 | |
| Reliability and failures of different steel wires used for springs. | 4th Mar 1937 | Box 158 \ 4 scan0130 | |
| Experiments and testing of new valve springs made from 'Swedish wire' versus standard springs. | 5th Mar 1937 | Box 158 \ 4 scan0131 | |
| The testing and comparison of different engine springs made from Swedish wire and Chrome-vanadium. | 5th Mar 1937 | Box 158 \ 4 scan0132 | |
| Letter from The Imperial Tobacco Company arranging a meeting with Mr. G. H. Grylls. | 5th Mar 1937 | Box 158 \ 4 scan0133 | |
| Letter from The Imperial Tobacco Company to G.H. Grylls arranging a meeting in Derby. | 11th Mar 1937 | Box 158 \ 4 scan0134 | |
| Letter to The Imperial Tobacco Co. Ltd. enclosing an arrangement drawing for a 25 HP unit and discussing rotary valve adaptation. | 19th Mar 1937 | Box 158 \ 4 scan0135 | |
| Letter from The Imperial Tobacco Company regarding a drawing for a 25 HP unit. | 22th Mar 1937 | Box 158 \ 4 scan0136 | |
| Request for the examination of two failed valve springs, one from a Bentley and one from a Phantom III. | 25th Mar 1937 | Box 158 \ 4 scan0137 | |
| Letter concerning an adaptation of a rotary valve design. | 30th Mar 1937 | Box 158 \ 4 scan0138 | |
| Micro-examination report on a failed Phantom III valve spring and a satisfactory Bentley valve spring. | 1st Apr 1937 | Box 158 \ 4 scan0139 | |
| The despatch of two springs to The Tempered Spring Co. for examination. | 27th May 1937 | Box 158 \ 4 scan0140 | |
| Letter to The Tempered Spring Co. regarding the failure of Rm.260 springs during testing and their return for analysis. | 27th May 1937 | Box 158 \ 4 scan0141 | |
| Letter from R.C. Cross regarding a rotary valve design for a 25 HP unit. | 28th May 1937 | Box 158 \ 4 scan0142 | |
| Concluding page of a letter regarding the efficiency and performance of a specific design. | 28th May 1937 | Box 158 \ 4 scan0143 | |
| Design proposal for adapting a cross rotary valve system to a 25 HP engine. | 28th May 1937 | Box 158 \ 4 scan0144 | |
| Design document for a cross rotary valve for a 25 HP engine. | 3rd Jun 1937 | Box 158 \ 4 scan0145 | |
| Letter to The Tempered Spring Co. Ltd. regarding failures of RM.260 valve springs and requesting their findings. | 3rd Jun 1937 | Box 158 \ 4 scan0146 | |
| Describing a valve lift indicator for testing Bentley and Phantom III engines. | 5th Jun 1937 | Box 158 \ 4 scan0147 | |
| Required parts and drawings for proceeding with a test on a Bentley engine. | 5th Jun 1937 | Box 158 \ 4 scan0148 | |
| Letter to The Tempered Spring Co. regarding failed springs and a new order for Rm.260 springs. | 8th Jun 1937 | Box 158 \ 4 scan0149 | |
| Official covering order for valve springs. | 8th Jun 1937 | Box 158 \ 4 scan0150 | |
| Instruction to manufacture valve springs using recently purchased wire from Sweden. | 10th Jun 1937 | Box 158 \ 4 scan0151 | |
| The failure of rocker shafts on Bentley and Phantom III models, concluding it is due to improperly tightened nuts. | 11th Jun 1937 | Box 158 \ 4 scan0152 | |
| Response letter to Mr. R.C. Cross regarding the claims for his Rotary Valve design. | 14th Jun 1937 | Box 158 \ 4 scan0153 | |
| Blueprint detailing the adaptation of a 'Cross' rotary valve and drive arrangement for a 3.5 litre, six-cylinder engine. | 24th May 1937 | Box 158 \ 4 scan0154 | |
| Adaptation of a cross rotary valve to a 3.5 litre, six-cylinder engine. | 24th May 1937 | Box 158 \ 4 scan0155 | |
| Specification sheet detailing valve timings for various camshafts. | 14th Jun 1937 | Box 158 \ 4 scan0156 | |
| Letter from R.C. Cross regarding tests on an experimental engine using an adapted Austin Eighteen car. | 18th Jun 1937 | Box 158 \ 4 scan0157 | |
| Page 2 of a letter to W. A. Robotham regarding demonstrating results with an Austin Eighteen car. | 18th Jun 1937 | Box 158 \ 4 scan0158 | |
| Request for a resumé of the general progress on valve springs. | 18th Jun 1937 | Box 158 \ 4 scan0159 | |
| Letter from ironfounders C. & B. Smith Ltd regarding the production of 24 experimental chilled face tappet castings. | 21th Jun 1937 | Box 158 \ 4 scan0160 | |
| Letter to The Tempered Spring Co. requesting information on the failure of two springs. | 1st Jul 1937 | Box 158 \ 4 scan0161 | |
| Experiments and findings regarding valve spring reliability and suppliers. | 2nd Jul 1937 | Box 158 \ 4 scan0162 | |
| Trial of spring rings to prevent valve over-oiling, which proved less effective than the standard grummet. | 2nd Jul 1937 | Box 158 \ 4 scan0163 | |
| Letter of recommendation from Vauxhall Motors for Mr. Stenhouse, a specialist in springs. | 7th Jul 1937 | Box 158 \ 4 scan0164 | |
| Letter to Mr. A.C. Stenhouse inviting him for a discussion on valve springs. | 8th Jul 1937 | Box 158 \ 4 scan0165 | |
| Letter from the Experimental Department chasing a delayed delivery of experimental tappets. | 9th Jul 1937 | Box 158 \ 4 scan0166 | |
| Letter to Messrs C. & B. Smith Ltd. acknowledging receipt of tappet blanks and advising an official order will be placed. | 12th Jul 1937 | Box 158 \ 4 scan0167 | |
| The despatch of two Bentley inlet valves to A. Duckham Ltd. | 5th Aug 1937 | Box 158 \ 4 scan0168 | |
| Letter from Alexander Duckham & Co. Ltd. thanking for the return of two loaned Bentley Inlet Valves. | 9th Aug 1937 | Box 158 \ 4 scan0169 | |
| Micro-examination report on two broken valve springs from chassis No. 3BT.179. | 11th Aug 1937 | Box 158 \ 4 scan0170 | |
| Laboratory report cover featuring a photograph of two fractured metal rings. | 11th Aug 1937 | Box 158 \ 4 scan0171 | |
| Letter providing guidance on the process of Stelliting valves. | 20th Sep 1937 | Box 158 \ 4 scan0172 | |
| Instructions for applying Stellite to valve steel using an acetylene torch. | 20th Sep 1937 | Box 158 \ 4 scan0173 | |
| Page 3 of a letter detailing the Stelliting process for valves, including a sketch and cooling instructions. | 21th Sep 1937 | Box 158 \ 4 scan0174 | |
| Letter to E.R.A. Ltd. concerning the examination of failed valves and the reasons for their failure. | 21th Sep 1937 | Box 158 \ 4 scan0175 | |
| Letter discussing defects discovered in engine valves after etching, related to the Stellite application process. | 21th Sep 1937 | Box 158 \ 4 scan0176 | |
| Requesting the dispatch of 5 valves back to Mr. P. Berthon of E.R.A. Ltd for inspection. | 21th Sep 1937 | Box 158 \ 4 scan0177 | |
| Letter from English Racing Automobiles regarding issues with stelliting valves and a request for inspection and further observations. | 21th Sep 1937 | Box 158 \ 4 scan0178 | |
| Letter from English Racing Automobiles Ltd. regarding the failure of exhaust valves and requesting stelliting services. | 23th Sep 1937 | Box 158 \ 4 scan0179 | |
| Continuation letter from English Racing Automobiles Ltd. regarding the final machining of fabricated parts. | 23th Sep 1937 | Box 158 \ 4 scan0180 | |
| Letter from English Racing Automobiles Ltd discussing valve stelliting troubles and requesting assistance. | 23th Sep 1937 | Box 158 \ 4 scan0181 | |
| Letter declining a request for Stelliting valves and recommending Motor Components Ltd. of Birmingham for the work. | 28th Sep 1937 | Box 158 \ 4 scan0182 | |
| Letter from English Racing Automobiles Ltd. thanking for correspondence and confirming they are contacting Motor Components, Ltd. as suggested. | 1st Oct 1937 | Box 158 \ 4 scan0183 | |
| Requesting the dispatch of 3 valves to F.R. Banks of Ethyl Export Corporation for trial. | 13th Oct 1937 | Box 158 \ 4 scan0184 | |
| Letter detailing the trial results and condition of three exhaust valves submitted for testing. | 13th Oct 1937 | Box 158 \ 4 scan0185 | |
| Letter discussing cracked Sil.XCR valves and seeking feedback on the manufacturing issue. | 28th Oct 1937 | Box 158 \ 4 scan0186 | |
| Letter to The Midland Cylinder Co. requesting a quote for a trial batch of tappet casting blanks using a new material called Monichrome. | 28th Oct 1937 | Box 158 \ 4 scan0187 | |
| Requesting a report on valves held open by the hydraulic mechanism in a cold chamber, questioning if the cause was Price's oil or sludge. | 28th Oct 1937 | Box 158 \ 4 scan0188 | |
| Serious situation and potential causes for the failure of hydraulic tappets. | 29th Oct 1937 | Box 158 \ 4 scan0189 | |
| Plunger clearance, oil leakage, and sludge issues in tappet and valve mechanisms. | 29th Oct 1937 | Box 158 \ 4 scan0190 | |
| List of experimental cars showing mileage covered during hydraulic tappet tests. | 29th Oct 1937 | Box 158 \ 4 scan0191 | |
| Letter from a supplier advising against the use of their 'Monikrom' alloy for tappets due to unsuitability. | 30th Oct 1937 | Box 158 \ 4 scan0192 | |
| The mileage completed by various units on a solid rocker mechanism. | 2nd Nov 1937 | Box 158 \ 4 scan0193 | |
| Procedure for deleting silent hydraulic tappets following a successful 15,000-mile test. | 11th Nov 1937 | Box 158 \ 4 scan0194 | |
| The trial results of non-stellited Thompson-Products exhaust valves and requesting further information. | 2nd Dec 1937 | Box 158 \ 4 scan0195 | |
| Series of questions regarding the sourcing, pricing, and advantages of American Silichrome valve materials. | 2nd Dec 1937 | Box 158 \ 4 scan0196 | |
| Letter from Belgrave Engineering Co offering to manufacture Push Rods and enclosing a sample valve, referencing their previous work for Ford. | 3rd Dec 1937 | Box 158 \ 4 scan0197 | |
| Confirming a trial to incorporate valve spring dampers and delete bottom spring washers. | 7th Dec 1937 | Box 158 \ 4 scan0198 | |
| Letter to Belgrave Engineering Co. regarding a sample valve, its quality, and a request for quotation for production. | 15th Dec 1937 | Box 158 \ 4 scan0199 | |
| Addition of tappet retaining plates for Wraith III and Bentley 111 engines. | 16th Dec 1937 | Box 158 \ 4 scan0200 | |
| Request to manufacture petrol drain valves for the Phantom III and 30 HP models. | 31th Dec 1937 | Box 158 \ 4 scan0201 | |
| Quotation for chassis valve forgings from Belgrave Eng. Co. and requesting a cost analysis. | 10th Jan 1938 | Box 158 \ 4 scan0202 | |
| Request for the production of two sets of valve springs, one normally produced and one shot blasted, for a special long distance test. | 10th Jan 1938 | Box 158 \ 4 scan0203 | |
| Analysis of a sample 'die cast' cast iron tappett from the Ford Motor Company, comparing its material composition and hardness to tappetts produced for the Wraith. | 14th Jan 1938 | Box 158 \ 4 scan0204 | |
| Letter to The Belgrave Engineering Co. regarding the production and costing of valves and push rods. | 24th Jan 1938 | Box 158 \ 4 scan0205 | |
| Letter to The Tempered Spring Co. requesting the supply of springs for an experimental trial. | 31th Jan 1938 | Box 158 \ 4 scan0206 | |
| Testing, adoption, and trials of different valve springs for various car models. | 31th Jan 1938 | Box 158 \ 4 scan0207 | |
| Comparative cost analysis for different types of springs. | 31th Jan 1938 | Box 158 \ 4 scan0208 | |
| Letter to The Tempered Spring Co. regarding the specifications and potential design improvements for two spring types. | 1st Feb 1938 | Box 158 \ 4 scan0209 | |
| Letter specifying diameter limits for valve spring washers and requesting urgent delivery of springs. | 1st Feb 1938 | Box 158 \ 4 scan0210 | |
| Letter to The Tempered Spring Co. enquiring about the delivery of an order for valve springs. | 11th Feb 1938 | Box 158 \ 4 scan0211 | |
| Technical report providing an analysis and comparison of three American Silcrome valve steels. | 12th Feb 1938 | Box 158 \ 4 scan0212 | |
| Report comparing American valve steels like Silcrome, including prices, equivalents, and adoption by various car manufacturers. | 12th Feb 1938 | Box 158 \ 4 scan0213 | |
| The difficulties of stelliting Silcrome steel and issues with valve steel. | 12th Feb 1938 | Box 158 \ 4 scan0214 | |
| Suggesting an increase in screw diameter from 5.BA to 3.BA for the rocker shaft location screw on Wraith, Bentley & 30 HP models. | 23th Feb 1938 | Box 158 \ 4 scan0215 | |
| Locking the 5.BA. location screw in the rocker shaft for 25/30 and Bentley models. | 25th Feb 1938 | Box 158 \ 4 scan0216 | |
| Complaint about broken Chrome Vanadium valve springs and suggesting a trial of carbon valve springs with anti-surge coiling. | 4th Mar 1938 | Box 158 \ 4 scan0217 | |
| Valve spring failure due to corrosion on Chassis GUN-37. | 9th Mar 1938 | Box 158 \ 4 scan0218 | |
| Letter to a supplier regarding difficulty machining inlet valves and asking for heat treatment advice. | 16th Mar 1938 | Box 158 \ 4 scan0219 | |
| Revised oil pipe design for the Wraith III and Bentley 111 relief valves to improve access. | 18th Mar 1938 | Box 158 \ 4 scan0220 | |
| Letter to The British Tyre & Rubber Co. requesting a supply of twelve 'Neuprene' bushes with specific dimensions and hardness. | 6th Apr 1938 | Box 158 \ 4 scan0221 | |
| Request to manufacture six rocker cover thumb nuts from a cheaper material for testing and cost-saving purposes. | 6th Apr 1938 | Box 158 \ 4 scan0222 | |
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