| Description | Date | Identifier | |
| Letter to The Tempered Spring Co. requesting a quotation for large quantities of valve springs for the 30 HP model. | 9th Apr 1938 | Box 158 \ 4 scan0223 | |
| Requesting an official order for a dozen 'Neoprene' bushes from the British Tyre and Rubber Co. | 13th Apr 1938 | Box 158 \ 4 scan0224 | |
| Letter to The Tempered Spring Co. regarding the rejection of 1300 poorly finished valve springs. | 25th Apr 1938 | Box 158 \ 4 scan0225 | |
| Letter to The Tempered Spring Co. regarding the poor finish on EB.3256 valve springs. | 9th May 1938 | Box 158 \ 4 scan0226 | |
| Page 2 of a typed letter discussing finishing and occasional failures. | 9th May 1938 | Box 158 \ 4 scan0227 | |
| Issues and experimental solutions for flat bottom tappets on Wraith and Bentley engines. | 10th May 1938 | Box 158 \ 4 scan0228 | |
| Series of experiments modifying cam and tappet faces to ensure rotation and reduce wear. | 10th May 1938 | Box 158 \ 4 scan0229 | |
| Experiment with a Bentley 'S' direct-acting exhaust valve system compared to a normal rocker ratio system. | 10th Mar 1938 | Box 158 \ 4 scan0230 | |
| Blueprint showing four different experimental cam designs for the Wraith model. | 18th May 1938 | Box 158 \ 4 scan0231 | |
| The condition of various engine heads after testing, detailing warped and good condition units. | 26th May 1938 | Box 158 \ 4 scan0232 | |
| Deterioration of slow running in the Wraith model caused by incorrectly seating inlet valves. | 27th May 1938 | Box 158 \ 4 scan0233 | |
| Investigation into the warping of valve seats on the Wraith III engine model. | 26th May 1938 | Box 158 \ 4 scan0234 | |
| Engine valve seat warping, comparing different models and proposing solutions. | 26th May 1938 | Box 158 \ 4 scan0235 | |
| Letter from Lindbloom Auto Parts Co. concerning air leakage past intake valvestem guides and its effect on engine performance. | 1st Jun 1938 | Box 158 \ 4 scan0236 | |
| Promotional letter from Lindbloom Auto Parts Co. for their valve packing product. | 3rd Jun 1938 | Box 158 \ 4 scan0237 | |
| Letter inquiring about the use of plain silichrome exhaust valves on stellited seats to prevent valve burning. | 3rd Jun 1938 | Box 158 \ 4 scan0238 | |
| Information from AEC on valves, seats, and the use of Stellite. | 8th Jun 1938 | Box 158 \ 4 scan0239 | |
| Letter from Associated Equipment Co Ltd discussing exhaust valve and seat materials, including stellite and silichrome. | 8th Jun 1938 | Box 158 \ 4 scan0240 | |
| Letter from Associated Equipment Co. Ltd. discussing improvements in exhaust valve life using stellite seats and corrosion issues. | 1st Apr 1937 | Box 158 \ 4 scan0241 | |
| Drawing of an inlet valve for a high power head. | 13th Jul 1935 | Box 158 \ 4 scan0242 | |
| Letter to the Associated Equipment Co. Ltd. discussing valve and seat materials. | 11th Jun 1938 | Box 158 \ 4 scan0243 | |
| Letter from the Experimental Department requesting samples of valve and bearing packings for trial. | 15th Jun 1938 | Box 158 \ 4 scan0244 | |
| Letter from The Associated Equipment Co Ltd regarding valve testing and requesting information on stellite for War Office engines. | 20th Jun 1938 | Box 158 \ 4 scan0245 | |
| Cover letter to The Associated Equipment Co. enclosing a summary of the valve Stelliting process. | 21th Jun 1938 | Box 158 \ 4 scan0246 | |
| Letter from The Associated Equipment Co Ltd acknowledging receipt of information regarding the stelliting of valves. | 22th Jun 1938 | Box 158 \ 4 scan0247 | |
| Request to order two dozen Neuprene bushes with specific dimensions and hardness from the British Tyre company. | 22th Jun 1938 | Box 158 \ 4 scan0248 | |
| Letter from Lindbloom Auto Parts Co. regarding the application of packing on valve stems. | 29th Jun 1938 | Box 158 \ 4 scan0249 | |
| Letter to The Belgrave Engineering Co. regarding endurance testing and a new order for trial engine valves. | 29th Jun 1938 | Box 158 \ 4 scan0250 | |
| Official order for forged engine valves from Belgrave Engineering Co. | 29th Jun 1938 | Box 158 \ 4 scan0251 | |
| Technical memo detailing modifications to increase push rod clearance in the cylinder head for the Wraith III and Bentley 111 models. | 2nd Jul 1938 | Box 158 \ 4 scan0252 | |
| The design and testing of modified tappets and push rods for the Wraith III and Bentley III models. | 13th Jul 1938 | Box 158 \ 4 scan0253 | |
| The failure of obsolete bottom tappets on a Wraith unit and proposed design modifications. | 3rd Aug 1938 | Box 158 \ 4 scan0254 | |
| Blueprint drawing for a Tappet. | 4th Aug 1938 | Box 158 \ 4 scan0255 | |
| Standardisation of tappets and push rods for the Wraith III and B.III chassis. | 9th Aug 1938 | Box 158 \ 4 scan0256 | |
| Modification and strengthening of barrel type tappets for the Bentley III and Phantom III models. | 9th Aug 1938 | Box 158 \ 4 scan0257 | |
| Requesting an examination of cracks found on trial exhaust valves with stellite faces. | 11th Aug 1938 | Box 158 \ 4 scan0258 | |
| Letter to The Tempered Spring Co. regarding under-specification valve springs. | 31th Aug 1938 | Box 158 \ 4 scan0259 | |
| Letter from a spring supplier regarding a complaint about weak valve springs and discrepancies in load testing. | 1st Sep 1938 | Box 158 \ 4 scan0260 | |
| Modification for an oil seal on the valve spring top washer for Wraith III and Bentley III engines. | 9th Sep 1938 | Box 158 \ 4 scan0261 | |
| Successful trial of valve oil seal washers and a proposal for wider application and further investigation. | 22th Sep 1938 | Box 158 \ 4 scan0262 | |
| Confirming a material analysis of two .4 carbon push rods due to variations in Brinell hardness. | 22th Sep 1938 | Box 158 \ 4 scan0263 | |
| Letter from Joseph O. Eaton of Eaton Manufacturing Company regarding a meeting to discuss Hydraulic Lifters. | 23th Nov 1938 | Box 158 \ 4 scan0264 | |
| Letter to J.O. Eaton arranging a meeting for the 28th of November. | 24th Nov 1938 | Box 158 \ 4 scan0265 | |
| Pattern modification to the 8-cylinder exhaust valve guide. | 25th Nov 1938 | Box 158 \ 4 scan0266 | |
| Telegram from Eaton to Mr. Robotham arranging a meeting to discuss Lister prices. | 30th Nov 1938 | Box 158 \ 4 scan0267 | |
| Telegram received by telephone arranging a meeting to discuss Lister prices. | 30th Nov 1938 | Box 158 \ 4 scan0268 | |
| Telegram received by telephone requesting a meeting to discuss lister prices. | 30th Nov 1938 | Box 158 \ 4 scan0269 | |
| Short, typed and handwritten memo confirming a meeting. | 30th Nov 1938 | Box 158 \ 4 scan0270 | |
| Urgent memo regarding the failure of B.60 bottom tappets during an endurance run and the need for a modified design. | 1st Dec 1938 | Box 158 \ 4 scan0271 | |
| Methods to reduce engine detonation and material considerations for exhaust valves. | 7th Dec 1938 | Box 158 \ 4 scan0272 | |
| Valve gear failure on the B.60 unit and proposing design changes for various engines. | 8th Dec 1938 | Box 158 \ 4 scan0273 | |
| Preferred method for an oil seal on a valve spring top washer for the Wraith III. | 8th Dec 1938 | Box 158 \ 4 scan0274 | |
| The unauthorized order of 48 sample valves from Daniel Doncaster Co, Ltd. | 13th Dec 1938 | Box 158 \ 4 scan0275 | |
| Specification sheet for an overhead valve engine detailing valve gear weights, spring loads, timing, and accelerations. | 13th Dec 1938 | Box 158 \ 4 scan0276 | |
| Specifications for a Side Valve Engine including valve gear weights, loads, timing, and performance data. | 13th Dec 1938 | Box 158 \ 4 scan0277 | |
| Diagram of an engine oil system with specified pressures. | 14th Dec 1938 | Box 158 \ 4 scan0278 | |
| Letter from The Studebaker Corporation discussing engine valve cooling, temperatures, and running-on issues. | 14th Dec 1938 | Box 158 \ 4 scan0279 | |
| Research engineer's report on engine after-firing, crankshaft vibration damper, and overdrive gearbox issues. | 14th Dec 1938 | Box 158 \ 4 scan0280 | |
| Letter to Mr. Robotham chasing up delayed information for the Engineering Department in Detroit. | 15th Dec 1938 | Box 158 \ 4 scan0281 | |
| Letter from Olds Motor Works to Mr. W.A. Robotham regarding their opinions on engine valves. | 16th Dec 1938 | Box 158 \ 4 scan0282 | |
| Letter to J.O. Eaton regarding particulars for hydraulic tappets. | 16th Dec 1938 | Box 158 \ 4 scan0283 | |
| Letter from Chrysler Corporation to W. A. Robotham regarding exhaust valve temperatures and engine performance. | 19th Dec 1938 | Box 158 \ 4 scan0284 | |
| Letter from Chrysler Corporation to Mr. W. A. Robotham concerning valve temperature and tappet adjusters. | 19th Dec 1938 | Box 158 \ 4 scan0285 | |
| Points from a paper by Banks regarding trials on car engine components. | 20th Dec 1938 | Box 158 \ 4 scan0286 | |
| Letter from Ethyl Export Corporation requesting data on valve closing velocities and car test results. | 20th Dec 1938 | Box 158 \ 4 scan0287 | |
| Letter discussing oil pressure for tappets, sodium-cooled valves, and valve positions. | 20th Dec 1938 | Box 158 \ 4 scan0288 | |
| The second page of a typed letter concluding with a signature from Joseph O. Eaton, Jnr. | 26th Nov 1938 | Box 158 \ 4 scan0289 | |
| Letter from Joseph O. Eaton, Jnr. to W. A. Robothom confirming a meeting. | 26th Nov 1938 | Box 158 \ 4 scan0290 | |
| Technical drawing of an exhaust valve seat. | 25th Jul 1935 | Box 158 \ 4 scan0291 | |
| Technical drawing for an inlet and exhaust valve. | 18th Jul 1935 | Box 158 \ 4 scan0292 | |
| Requesting an official drawing for a modified inlet valve for the Wraith or Bentley V. | 29th Dec 1938 | Box 158 \ 4 scan0293 | |
| Letter from Eaton Manufacturing Company regarding a price increase for an intake valve gear unit due to a non-standard modification. | 3rd Jan 1939 | Box 158 \ 5 scan0001 | |
| Letter to a customer advising to hold off ordering hydraulic tappets due to increased cost and future improvements. | 4th Jan 1939 | Box 158 \ 5 scan0002 | |
| Letter from The Tempered Spring Company Limited regarding the dispatch of 36 valve springs and a deviation from drawing specifications. | 5th Jan 1939 | Box 158 \ 5 scan0003 | |
| Letter from Eaton Manufacturing Company confirming a supply agreement and requesting an order for samples. | 9th Jan 1939 | Box 158 \ 5 scan0004 | |
| Requesting an order to be placed with the Eaton Manufacturing Co. for one dozen hydraulic tappet lifters. | 10th Jan 1939 | Box 158 \ 5 scan0005 | |
| Modification to improve lubrication on the B.60 and B.80 valve gear. | 23th Jan 1939 | Box 158 \ 5 scan0006 | |
| Requesting an order for eight valve seats from the British Piston Ring Co. | 24th Jan 1939 | Box 158 \ 5 scan0007 | |
| Letter to The British Piston Ring Co. Ltd. requesting a supply of eight valve seats in Brickromium. | 24th Jan 1939 | Box 158 \ 5 scan0008 | |
| Adoption of Magnaflux testing for valve springs. | 8th Feb 1939 | Box 158 \ 5 scan0009 | |
| Proposing a test on an engine fitted with double valve springs. | 8th Feb 1939 | Box 158 \ 5 scan0010 | |
| Confirming the acquisition of a Metropolitan Vickers Magnetic Testing Machine for Magnaflux testing of valve springs. | 10th Feb 1939 | Box 158 \ 5 scan0011 | |
| Letter from Wilcox-Rich confirming the shipment of hydraulic lifter unit samples. | 15th Feb 1939 | Box 158 \ 5 scan0012 | |
| Letter from a supplier regarding notes on helical springs and requesting to see a shot-blasted valve spring. | 22th Feb 1939 | Box 158 \ 5 scan0013 | |
| Letter from Associated Equipment Co Ltd regarding salt-cooled valves and potential patent infringements. | 27th Feb 1939 | Box 158 \ 5 scan0014 | |
| Technical drawing of an exhaust valve. | 7th Nov 1935 | Box 158 \ 5 scan0015 | |
| Letter regarding the unavailability and future forwarding of shot-blasted valve springs. | 28th Feb 1939 | Box 158 \ 5 scan0016 | |
| Dozen shot-blasted springs (EB 3256) with spares for a trial. | 28th Feb 1939 | Box 158 \ 5 scan0017 | |
| Letter to Associated Equipment Co. Ltd. regarding the patent rights for salt-filled valves and a potential patent extension. | 28th Feb 1939 | Box 158 \ 5 scan0018 | |
| Article on the design, analysis, and failures of aircraft engine valve mechanisms, discussing issues like false motion and seating velocities. | 1st Mar 1939 | Box 158 \ 5 scan0019 | |
| Analysis of valve cam lift curves comparing high and low RPM performance, showing deflection and discussing resulting valve failures. | 1st Mar 1939 | Box 158 \ 5 scan0020 | |
| Analysis page on aircraft valve mechanisms, with graphs illustrating cam lift curves and seating velocities. | 1st Mar 1939 | Box 158 \ 5 scan0021 | |
| Aircraft valve mechanisms, material requirements, and operational issues like seating velocity. | 1st Mar 1939 | Box 158 \ 5 scan0022 | |
| Page from a Society of Automotive Engineers (S.A.E.) journal discussing engine valve clearances, material properties, and hydraulic lifter compensation. | 1st Mar 1939 | Box 158 \ 5 scan0023 | |
| Page discussing aircraft valve mechanisms, material properties, fatigue failure, and corrosion resistance. | 1st Mar 1939 | Box 158 \ 5 scan0024 | |
| Journal page discussing engine valve seat inserts and different designs for internally cooled valves. | 1st Mar 1939 | Box 158 \ 5 scan0025 | |
| Query regarding the optimal sodium fill percentage for sodium-cooled valves, referencing an S.A.E. Journal article. | 18th Mar 1939 | Box 158 \ 5 scan0026 | |
| Letter from Eaton Manufacturing Company regarding timing diagrams and cam contours for engines. | 18th Mar 1939 | Box 158 \ 5 scan0027 | |
| Letter to The Eaton Manufacturing Co. regarding the camshaft for hydraulic tappets. | 20th Mar 1939 | Box 158 \ 5 scan0028 | |
| Comparison of hairpin type and helical valve springs, specifically the B.60 and a 1937 Norton T.T. spring. | 30th Mar 1939 | Box 158 \ 5 scan0029 | |
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