| Description | Date | Identifier | |
| Request to The Light Production Co. Ltd. for the supply of seven modified 4 1/4 litre Bentley Aerolite Pistons. | 17th Dec 1938 | Box 148 \ 1 scan0030 | |
| Summary of a preliminary test on a modified piston crown for the Wraith and Bentley V engines. | 17th Dec 1938 | Box 148 \ 1 scan0031 | |
| Piston crown design, discussing detonation prevention by referencing a Vauxhall design and a quote from 'Autocar' magazine. | 16th Dec 1938 | Box 148 \ 1 scan0032 | |
| Blueprint diagram of a Vauxhall combustion chamber. | 16th Dec 1938 | Box 148 \ 1 scan0033 | |
| Blueprint of a Standard Bentley Head and Raised Piston Crown. | 16th Dec 1938 | Box 148 \ 1 scan0034 | |
| Graph of BHP vs RPM for a 4 1/4 Litre Bentley engine with different piston compression ratios. | 16th Dec 1938 | Box 148 \ 1 scan0035 | |
| Blueprint graph of a 4 1/4 Litre Bentley engine showing B.HP and Ignition Advance vs R.P.M. for different compression ratios. | 1st Jan 1939 | Box 148 \ 1 scan0036 | |
| Summary of a paper on the phosphate treatment process, 'Granosealing', for piston rings. | 1st Jan 1939 | Box 148 \ 1 scan0037 | |
| Research committee report comparing anodising and tin-plating of aluminium alloy pistons. | 1st Jan 1939 | Box 148 \ 1 scan0038 | |
| Letter to The Light Production Co. Ltd. requesting the supply of 14 T.T. Bentley pistons. | 3rd Jan 1939 | Box 148 \ 1 scan0039 | |
| Order for 14 pistons from The Light Production Co. Ltd. | 3rd Jan 1939 | Box 148 \ 1 scan0040 | |
| Letter to The Light Production Co. Ltd. requesting the supply of various pistons. | 21th Jan 1939 | Box 148 \ 1 scan0041 | |
| Order to be placed for various types of pistons. | 21th Jan 1939 | Box 148 \ 1 scan0042 | |
| Seeking authorization to pay an invoice for 144 piston rings, double the quantity of 72 that was originally ordered. | 23th Jan 1939 | Box 148 \ 1 scan0043 | |
| Over-supply of piston rings from the supplier Wellworthy. | 27th Jan 1939 | Box 148 \ 1 scan0044 | |
| Letter from The Light Production Co. Ltd. acknowledging receipt of communication for an order of Pistons. | 24th Jan 1939 | Box 148 \ 1 scan0045 | |
| The compression ratio for the B.V. model, detailing road test results and standardisation considerations. | 9th Feb 1939 | Box 148 \ 1 scan0046 | |
| Road tests of Bentley V pistons with an increased compression ratio to improve engine performance. | 9th Feb 1939 | Box 148 \ 1 scan0047 | |
| Governor advance curve graph for a Delco-Remy distributor modified for B units with 7:1 compression pistons. | 2nd Dec 1938 | Box 148 \ 1 scan0048 | |
| Letter to Wellworthy Piston Rings Ltd. discussing piston and ring wear, mileage tests, and performance. | 17th Feb 1939 | Box 148 \ 1 scan0049 | |
| Letter from a piston ring specialist regarding raised centre pistons and 'L' section rings. | 20th Feb 1939 | Box 148 \ 1 scan0050 | |
| Letter from a piston ring manufacturer discussing the performance of cell-faced and tin-plated rings. | 22th Feb 1939 | Box 148 \ 1 scan0051 | |
| Internal request to place an official order for compression and scraper rings. | 22th Feb 1939 | Box 148 \ 1 scan0052 | |
| Request to The Light Production Co. Ltd. for tin-plated compression and scraper rings for Bentley production. | 22th Feb 1939 | Box 148 \ 1 scan0053 | |
| Request to send an order for 28 pistons to The Light Production Co. Ltd. | 2nd Mar 1939 | Box 148 \ 1 scan0054 | |
| Letter from the Experimental Department requesting the supply of 28 pistons based on enclosed drawings. | 2nd Mar 1939 | Box 148 \ 1 scan0055 | |
| Letter from Wellworthy Piston Rings Ltd. regarding the supply and design of an 'L' shaped piston ring, named 'Everseel'. | 4th Mar 1939 | Box 148 \ 1 scan0056 | |
| Letter from Hepworth & Grandage Ltd. regarding the experimental testing of Phormicast piston rings. | 6th Mar 1939 | Box 148 \ 1 scan0057 | |
| Letter from The Light Production Co. Ltd. concerning the delivery of Piston EW.2121 and a proposed works visit. | 6th Mar 1939 | Box 148 \ 1 scan0058 | |
| Letter from Hepworth & Grandage Ltd discussing the testing of high tension cast-to-form rings. | 7th Mar 1939 | Box 148 \ 1 scan0059 | |
| Letter concerning an order for Pistons EW.2121, discussing the need for a new wooden corebox due to design changes and estimating a four-week delivery. | 7th Mar 1938 | Box 148 \ 1 scan0060 | |
| Letter to The Light Production Co. Ltd. arranging a works visit and referencing piston EW.2121. | 7th Mar 1939 | Box 148 \ 1 scan0061 | |
| Letter from The Light Production Co. Ltd. regarding a meeting, piston EW.2121, and alloy Aerolite 122. | 8th Mar 1939 | Box 148 \ 1 scan0062 | |
| Letter from a supplier regarding a change in piston production alloy and seeking a decision on testing. | 9th Mar 1939 | Box 148 \ 1 scan0063 | |
| Letter to J. Howlett of Wellworthy Piston Rings Ltd. concerning the 'L' Section Ring for oil control. | 9th Mar 1939 | Box 148 \ 1 scan0064 | |
| Letter to a supplier requesting exact dimensions and limits for piston grooves before manufacture. | 10th Mar 1939 | Box 148 \ 1 scan0065 | |
| Letter to The Light Production Co. Ltd. regarding the alloy for piston EW.2121 and confirming a meeting. | 11th Mar 1939 | Box 148 \ 1 scan0066 | |
| Letter from Wellworthy Piston Rings Ltd. discussing a potential collaboration on piston manufacturing and associated patents. | 13th Mar 1939 | Box 148 \ 1 scan0067 | |
| Letter to W. A. Robotham regarding an experiment and a potential agreement for the manufacture and sale of a piston. | 13th Mar 1939 | Box 148 \ 1 scan0068 | |
| Request to scheme the adaptation of a Buick harmonic damper and a drawing for a modified Aerolite piston. | 15th Mar 1939 | Box 148 \ 1 scan0069 | |
| Letter from Wellworthy Piston Rings Ltd. regarding a high compression piston design. | 16th Mar 1939 | Box 148 \ 1 scan0070 | |
| Diagram with dimensions for a Leyland 3 1/2' Cub petrol engine cylinder head. | 13th Mar 1939 | Box 148 \ 1 scan0071 | |
| Letter from Hepworth & Grandage apologising for a delay and enclosing a revised sketch with suggested limits for ring grooves. | 16th Mar 1939 | Box 148 \ 1 scan0072 | |
| Specification drawing for Phormicast piston rings, detailing dimensions, types, and tolerances. | 21th Mar 1939 | Box 148 \ 1 scan0073 | |
| Letter to The Light Production Co. Ltd. requesting modifications for the production of piston EW.2121. | 21th Mar 1939 | Box 148 \ 1 scan0074 | |
| Visit to The Light Production Co. Ltd. at Slough concerning piston manufacturing. | 22th Mar 1939 | Box 148 \ 1 scan0075 | |
| Comparison of 'Aerolite' and 'R.R.' piston manufacturing processes, including gudgeon pin fit, machining, ageing, and pressure testing. | 22th Mar 1939 | Box 148 \ 1 scan0076 | |
| Request to The Light Production Co. Ltd. for the supply of pistons. | 22th Mar 1939 | Box 148 \ 1 scan0077 | |
| Order for 20 pistons to be sent to The Light Production Co. Ltd. | 22th Mar 1939 | Box 148 \ 1 scan0078 | |
| Letter from The Light Production Co. Ltd. regarding Piston EW 2121 and the preparation of a new drawing. | 24th Mar 1939 | Box 148 \ 1 scan0079 | |
| Letter from The Light Production Co. Ltd. regarding the supply of 20 Pistons P.451. | 24th Mar 1939 | Box 148 \ 1 scan0080 | |
| Letter to The Light Production Co. Ltd. requesting the production of 20 flat crown pistons, part number EW.2115. | 27th Mar 1939 | Box 148 \ 1 scan0081 | |
| Internal request to place an order with The Light Production Co. Ltd. for 20 pistons. | 27th Mar 1939 | Box 148 \ 1 scan0082 | |
| Order for a set of pistons and the machining of ring grooves. | 27th Mar 1939 | Box 148 \ 1 scan0083 | |
| Blueprints for a modification to Aerolite Pistons on a Bentley Chassis. | 28th Mar 1939 | Box 148 \ 1 scan0084 | |
| Letter providing a provisional specification and recommendations for a raised crown piston for a Leyland engine. | 28th Mar 1939 | Box 148 \ 1 scan0085 | |
| Letter to The Light Production Co. Ltd. regarding a specification change for an order of 20 pistons. | 29th Mar 1939 | Box 148 \ 1 scan0086 | |
| Invoice details from Hepworth & Grandage Ltd. for various Phormicast rings for experimental purposes. | 29th Mar 1939 | Box 148 \ 1 scan0087 | |
| Authorising payment to Hepworth & Grandage Ltd. for piston rings for an experimental trial. | 30th Mar 1939 | Box 148 \ 1 scan0088 | |
| Letter from Wellworthy Piston Rings Ltd. discussing pistons for a Leyland lorry and patents on cylinder heads. | 30th Mar 1939 | Box 148 \ 1 scan0089 | |
| Letter from The Light Production Co. Ltd. regarding piston skirt dimensions and part numbers. | 31th Mar 1939 | Box 148 \ 1 scan0090 | |
| Letter from Wellworthy Piston Rings correcting engine stroke information and requesting piston head specifications. | 31th Mar 1939 | Box 148 \ 1 scan0091 | |
| Letter to Wellworthy Piston Rings Ltd. regarding raised crown pistons and a streamline Bentley. | 31th Mar 1939 | Box 148 \ 1 scan0092 | |
| Letter to Wellworthy Piston Rings Ltd. concerning a bump crown piston design. | 3rd Apr 1939 | Box 148 \ 1 scan0093 | |
| Letter from Wellworthy Piston Rings Ltd. acknowledging receipt of a letter while Mr. Howlett is away. | 3rd Apr 1939 | Box 148 \ 1 scan0094 | |
| Letter from The Light Production Co. Ltd. regarding drawing P.461 for piston part EW.2121, discussing elliptical grinding. | 4th Apr 1939 | Box 148 \ 1 scan0095 | |
| Letter from Wellworthy Piston Rings regarding the casting of bump crown pistons for a Leyland 3 1/2' Cub Engine. | 4th Apr 1939 | Box 148 \ 1 scan0096 | |
| Letter from Wellworthy Piston Rings Ltd. discussing the re-wording of a patent and a proposed meeting. | 12th Apr 1939 | Box 148 \ 1 scan0097 | |
| Weaknesses of a patent application for a piston design and proposing next steps. | 12th Apr 1939 | Box 148 \ 1 scan0098 | |
| Wording of a patent application for a piston and cylinder head design. | 12th Apr 1939 | Box 148 \ 1 scan0099 | |
| Commentary on patent specifications, discussing piston design and compression ratios. | 12th Apr 1939 | Box 148 \ 1 scan0100 | |
| Clarification needed for a patent claim on combustion chamber and piston head design. | 12th Apr 1939 | Box 148 \ 1 scan0101 | |
| Letter to The Light Production Co. Ltd. concerning piston drawings, elliptical grinding, and an order for 14 pistons. | 13th Apr 1939 | Box 148 \ 1 scan0102 | |
| Letter to Wellworthy Piston Rings Ltd. concerning a provisional patent for a piston and arranging a meeting. | 13th Apr 1939 | Box 148 \ 1 scan0103 | |
| Letter from Wellworthy Piston Rings Ltd. confirming a meeting with W. A. Robotham. | 15th Apr 1939 | Box 148 \ 1 scan0104 | |
| Letter to The Light Production Co. Ltd. regarding the future production of pistons for a 4¼ litre Bentley. | 17th Apr 1939 | Box 148 \ 1 scan0105 | |
| Letter to Light Production Co. Ltd. confirming tin-plating as a standard feature on all supplied rings. | 17th Apr 1939 | Box 148 \ 1 scan0106 | |
| Letter from The Light Production Co. Ltd. regarding a discrepancy in drawing references for a piston order. | 17th Apr 1939 | Box 148 \ 1 scan0107 | |
| Letter from a patent agent concerning patent application No. 37227/38 for an 'Anti-Detonant Combustion Space'. | 18th Apr 1939 | Box 148 \ 1 scan0108 | |
| Letter to The Light Production Co. Ltd. clarifying details on drawing number EB.4740. | 19th Apr 1939 | Box 148 \ 1 scan0109 | |
| Performance, testing, and benefits of 'Razend Crown' pistons, proposed to be renamed 'Power Dome' pistons. | 20th Apr 1938 | Box 148 \ 1 scan0110 | |
| Solicitor's letter advising on the trademark protection for the term 'POWER-DOME'. | 20th Apr 1939 | Box 148 \ 1 scan0111 | |
| Second page of a letter concerning the potential acceptance of the word 'Powerdom'. | 20th Apr 1939 | Box 148 \ 1 scan0112 | |
| Letter from The Light Production Co. Ltd. concerning the production and delivery of pistons. | 21th Apr 1939 | Box 148 \ 1 scan0113 | |
| Letter from The Light Production Co. Ltd. discussing modifications to a die, piston ring coatings, and delivery schedules. | 25th Apr 1939 | Box 148 \ 1 scan0114 | |
| Letter from patent agents regarding patent application No. 37227/38 for an 'Anti-Detonant Combustion Space', enclosing a relevant sketch from the Alta Car & Engineering Company. | 25th Apr 1939 | Box 148 \ 1 scan0115 | |
| Diagram showing two different combustion chamber shapes. | 25th Apr 1939 | Box 148 \ 1 scan0116 | |
| Letter from Wellworthy Piston Rings Ltd. regarding the strategy for obtaining a final patent. | 25th Apr 1939 | Box 148 \ 1 scan0117 | |
| Letter to The Light Production Co. Ltd. regarding the supply and testing of experimental pistons. | 25th Apr 1939 | Box 148 \ 1 scan0118 | |
| Request to The Light Production Co. Ltd. to prepare 14 pistons with a .360 bump, based on piston design EW.2170. | 26th Apr 1939 | Box 148 \ 1 scan0119 | |
| Letter to Messrs. Walford & Hardman Brown regarding a pending patent application and the potential impact of a prior user's design. | 26th Apr 1939 | Box 148 \ 1 scan0120 | |
| Order for 14 pistons to be sent to The Light Production Co. Ltd. | 26th Apr 1939 | Box 148 \ 1 scan0121 | |
| Letter to The Light Production Co. Ltd. requesting expedited delivery of six split skirt pistons. | 27th Apr 1939 | Box 148 \ 1 scan0122 | |
| Letter from The Light Production Co. Ltd. regarding the testing and despatch of P.461 Pistons. | 28th Apr 1939 | Box 148 \ 1 scan0123 | |
| Letter from patent agents discussing a 'Bentley Piston' patent application and potential prior art from the Alta engine. | 28th Apr 1939 | Box 148 \ 1 scan0124 | |
| Letter discussing the feasibility of obtaining a patent for an engine design in light of similarities with the Alta engine. | 28th Apr 1939 | Box 148 \ 1 scan0125 | |
| Testing and fitting of R.R. split skirt pistons to the W.III No.4 Unit. | 28th Apr 1939 | Box 148 \ 1 scan0126 | |
| Letter to a supplier discussing piston ring distortion and the 'bedding in' process for engines. | 1st May 1939 | Box 148 \ 1 scan0127 | |
| Letter from The Light Production Co. Ltd. regarding piston specifications and drawings. | 1st May 1939 | Box 148 \ 1 scan0128 | |
| Letter from The Light Production Co. Ltd. regarding the production schedule for Piston EW.2170. | 1st May 1939 | Box 148 \ 1 scan0129 | |
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