| Description | Date | Identifier | |
| Clarifying that a filter was sent on a loan account and should not be paid for. | 28th May 1936 | Box 135 \ 3 scan0117 | |
| Follow-up letter from S. Smith & Sons regarding a quotation for a new oil filter. | 20th Aug 1936 | Box 135 \ 3 scan0118 | |
| Letter to S. Smith & Sons Ltd. rejecting their oil filters after testing due to performance and size issues. | 3rd Sep 1936 | Box 135 \ 3 scan0119 | |
| Return of two Smith's oil filters that were loaned for testing. | 3rd Sep 1936 | Box 135 \ 3 scan0120 | |
| Letter from S. Smith & Sons regarding potential failure causes of their filter. | 7th Sep 1936 | Box 135 \ 3 scan0121 | |
| Letter from S. Smith & Sons regarding a returned filter and a new two-in-one oil filter design. | 7th Sep 1936 | Box 135 \ 3 scan0122 | |
| Dispatch of a pressure oil filter and two-stage relief valves for the Wraith II. | 2nd Jul 1936 | Box 135 \ 3 scan0123 | |
| Letter from S. Smith & Sons regarding a postponed visit to discuss a filter question. | 11th Sep 1936 | Box 135 \ 3 scan0124 | |
| Oil feed trouble causing sludge in the Phantom III chassis, comparing different oil brands. | 21th Sep 1936 | Box 135 \ 3 scan0125 | |
| Letter to S. Smith & Sons Ltd. providing information regarding an oil filter. | 23th Sep 1936 | Box 135 \ 3 scan0126 | |
| Letter from S. Smith & Sons acknowledging receipt of drawings and advising a filter arrangement is being prepared. | 26th Sep 1936 | Box 135 \ 3 scan0127 | |
| Follow-up letter from S. Smith & Sons requesting the normal working pressure for a specific flow rate and temperature. | 29th Sep 1936 | Box 135 \ 3 scan0128 | |
| Letter to Messrs. Smith & Sons Ltd. providing the normal working pressure corresponding to a specific flow rate and temperature. | 30th Sep 1936 | Box 135 \ 3 scan0129 | |
| Letter from S. Smith & Sons regarding a new 'BLUECOL' anti-freeze booklet. | 21th Oct 1936 | Box 135 \ 3 scan0130 | |
| Letter from S. Smith & Sons regarding their new BLUECOL anti-freeze booklet. | 22th Oct 1936 | Box 135 \ 3 scan0131 | |
| Design of a Bentley Suction Oil Strainer and Sump. | 26th Oct 1936 | Box 135 \ 3 scan0132 | |
| Collapsed and clogged oil pressure filter gauze element after running for 13,920 miles. | 9th Nov 1936 | Box 135 \ 3 scan0133 | |
| Notification regarding a collapsed main filter from a Phantom III being sent due to sludge formation. | 10th Nov 1936 | Box 135 \ 3 scan0134 | |
| Order for one dozen Tecalemit filters for use on experimental chassis unit beds. | 13th Nov 1936 | Box 135 \ 3 scan0135 | |
| Letter from the Experimental Dept. to AC-Sphinx Sparking Plug Co. requesting a sample oil filter for trial. | 31th Dec 1936 | Box 135 \ 3 scan0136 | |
| Letter from The AC-Sphinx Sparking Plug Co. Ltd. arranging a meeting to discuss oil filters. | 6th Jan 1937 | Box 135 \ 3 scan0137 | |
| Fitting Tecalemit type filters to production Bentley cars and their use on the test bed. | 24th Dec 1936 | Box 135 \ 3 scan0138 | |
| Defect in the Phantom III Tappet Oil Filter, detailing a modification to correct a bad oil seal. | 19th Feb 1937 | Box 135 \ 3 scan0139 | |
| Withdrawing the standardisation sheet for the Tecalemit oil filter on Bentley & 25/30 models due to oil pressure loss. | 31th Mar 1937 | Box 135 \ 3 scan0140 | |
| Recommendation to fit an internal guard to Phantom III suction filters to prevent them from collapsing. | 5th Apr 1937 | Box 135 \ 3 scan0141 | |
| Test bed report on the efficiency of an A.C. oil filter when used on a 4 1/4 Litre Bentley engine. | 20th Apr 1937 | Box 135 \ 3 scan0142 | |
| Distortion of the Phantom III oil strainer and a proposed modification using a supporting frame. | 5th May 1937 | Box 135 \ 3 scan0143 | |
| Decision to delete the designed pressure oil filter on the Wraith in favour of a bye-pass filter. | 21th May 1937 | Box 135 \ 3 scan0144 | |
| Order for two dozen Tecalemit filters for experimental chassis unit test beds. | 26th May 1937 | Box 135 \ 3 scan0145 | |
| Installation and cartridge renewal instructions for an oil filter. | 14th Apr 1937 | Box 135 \ 3 scan0146 | |
| Standardisation of parts for the Phantom III Tappet Oil Filter due to difficulty in dismantling. | 14th Apr 1937 | Box 135 \ 3 scan0147 | |
| Standardisation of parts form for the Phantom III, detailing production feasibility and cost estimation for new tools. | 20th May 1938 | Box 135 \ 3 scan0148 | |
| The premature sludging of Phantom III pressure oil filters, recommending an alteration to the service interval. | 9th Jun 1937 | Box 135 \ 3 scan0149 | |
| Recommending a change to the service interval for pressure oil filters based on field experience. | 9th Jun 1937 | Box 135 \ 3 scan0150 | |
| Turnings found in the filter of Phantom III chassis 3.BU.78. | 14th Jun 1937 | Box 135 \ 3 scan0151 | |
| Night Letter Telegram requesting half-a-dozen filter casings and elements for testing. | 23th Jun 1937 | Box 135 \ 3 scan0152 | |
| Telegram received by telephone confirming the immediate dispatch of filters, casings, and elements. | 26th Jun 1937 | Box 135 \ 3 scan0153 | |
| Cablegram from Webb in Detroit to Robotham in Derby, requesting the immediate dispatch of filter parts. | 26th Jul 1937 | Box 135 \ 3 scan0154 | |
| Western Union telegram confirming the immediate dispatch of General Filters casings and elements. | 25th Jun 1937 | Box 135 \ 3 scan0155 | |
| The temporary fitting of a general bypass filter to a Wraith III engine. | 8th Jul 1937 | Box 135 \ 3 scan0156 | |
| Payment authorization for two invoices received from General Filters, Inc. in Detroit, USA. | 17th Jul 1937 | Box 135 \ 3 scan0157 | |
| Request to send a covering order to General Filters, Inc. for goods that have already been dispatched. | 27th Jul 1937 | Box 135 \ 3 scan0158 | |
| Letter from General Filters, Inc. confirming the shipment of improved design filters and cartridges. | 28th Jun 1937 | Box 135 \ 3 scan0159 | |
| Letter detailing the results of initial tests on oil filters and cartridges. | 4th Aug 1937 | Box 135 \ 3 scan0160 | |
| Letter asking for information on the performance of a by-pass oil filter, including cartridge replacement mileage and efficiency. | 5th Aug 1937 | Box 135 \ 3 scan0161 | |
| Letter to A.C. Sphinx Sparking Plug Co. requesting A.C. bye-pass oil filters and details on their setup. | 5th Aug 1937 | Box 135 \ 3 scan0162 | |
| Modification to the Special Bye-pass Oil Filter on the Phantom III (32-EX). | 9th Jul 1937 | Box 135 \ 3 scan0163 | |
| Official order be placed for A.C. oil filters with A.C.Sphinx Spark Plug Co. | 12th Aug 1937 | Box 135 \ 3 scan0164 | |
| Cablegram from Chicago to Derby regarding a patent application filed by General Motors. | 13th Aug 1937 | Box 135 \ 3 scan0165 | |
| Letter to A.C. Sphinx Sparking Plug Co. Ltd. regarding the purchase and technical specifications of oil filters. | 17th Aug 1937 | Box 135 \ 3 scan0166 | |
| Internal memorandum requesting an urgent order for A.C. oil filters. | 23th Aug 1937 | Box 135 \ 3 scan0167 | |
| Follow-up letter to The A.C. Sphinx Spark Plug Co. concerning trials of their oil filters. | 23th Aug 1937 | Box 135 \ 3 scan0168 | |
| Complaint about stripped threads on the Phantom III Hydraulic Tappet Filter Body cover. | 27th Aug 1937 | Box 135 \ 3 scan0169 | |
| Recommendation to revert the Wraith suction strainer from a double gauze system to a single gauze filter for reasons of maintenance and cost. | 2nd Sep 1937 | Box 135 \ 3 scan0170 | |
| Letter to The AC Sphinx Spark Plug Co. regarding the trial installation and performance of their oil filters. | 3rd Sep 1937 | Box 135 \ 3 scan0171 | |
| Query regarding the correct jet hole size in ZS.1 filters for a pressure of 30lbs/square inch. | 7th Sep 1937 | Box 135 \ 3 scan0172 | |
| Order for 2 dozen Tecalemit filters for experimental chassis unit test beds. | 7th Sep 1937 | Box 135 \ 3 scan0173 | |
| Clarifying the use of Tecalemit filter elements on production and experimental cars. | 8th Sep 1937 | Box 135 \ 3 scan0174 | |
| Instructions and list of new blueprints for the Wraith III Chassis oil filter, section 5203. | 21th Sep 1937 | Box 135 \ 3 scan0175 | |
| Instructions for fitting an A.C. Bye-Pass filter and modified core covers for the Wraith III cylinder block. | 21th Sep 1937 | Box 135 \ 3 scan0176 | |
| Standardisation of a support guard for the oil sump filter to prevent gauze collapse on the Phantom III. | 23th Sep 1937 | Box 135 \ 3 scan0177 | |
| Cost estimation and proposal for a modification using a sweated sleeve in 'E' Series chassis end caps. | 1st Nov 1932 | Box 135 \ 3 scan0178 | |
| Letter from Jervis B. Webb Company inquiring about the market potential and manufacturing rights for their filters in England. | 13th Oct 1937 | Box 135 \ 3 scan0179 | |
| Comparison of 'AC' and 'General' type oil filters, including a performance test on chassis 32-EX. | 16th Nov 1937 | Box 135 \ 3 scan0180 | |
| Cost reduction and standardisation of the Phantom III suction filter guard. | 4th Nov 1937 | Box 135 \ 3 scan0181 | |
| Letter to Mr. Jervis B. Webb in Detroit regarding the comparison, sales, and manufacturing of a filter. | 16th Nov 1937 | Box 135 \ 3 scan0182 | |
| The second page of a letter discussing negotiations and attaching a tester's report. | 16th Nov 1937 | Box 135 \ 3 scan0183 | |
| Comparison document on 'AC' and 'General' type oil filters, including maintenance and test results. | 16th Nov 1937 | Box 135 \ 3 scan0184 | |
| Letter to Jervis B. Webb regarding a potential business opportunity for his oil filter with S. Smith & Sons. | 3rd Dec 1937 | Box 135 \ 3 scan0185 | |
| Invoice from General Filters, Inc. for the supply of No. 5 Cartridges. | 7th Dec 1937 | Box 135 \ 3 scan0186 | |
| Invoice from General Filters, Inc. for six No. 5 Cartridges. | 7th Dec 1937 | Box 135 \ 3 scan0187 | |
| Shipping memo from General Filters, Inc. for six cartridges sent for test purposes. | 7th Dec 1937 | Box 135 \ 3 scan0188 | |
| Order for 3 AC oil filters for use on a Bentley. | 8th Dec 1937 | Box 135 \ 3 scan0189 | |
| Testing a Tecalemit filter on the suction side of a pump for production units. | 21th Dec 1937 | Box 135 \ 3 scan0190 | |
| The use of Tecalemit filters on unit test beds for chassis engine tests. | 21th Dec 1937 | Box 135 \ 3 scan0191 | |
| Letter from General Filters, Inc. to Mr. W. A. Robotham concerning manufacturing and pricing options for a filter. | 21th Dec 1937 | Box 135 \ 3 scan0192 | |
| Letter from Jervis B. Webb Company regarding the potential manufacturing and sale of a filter in England. | 8th Dec 1937 | Box 135 \ 3 scan0193 | |
| Letter from General Filters, Inc. to Mr. W. A. Robotham regarding filter cartridges and pricing. | 7th Dec 1937 | Box 135 \ 3 scan0194 | |
| Advertisement flyer for the new improved model of the General Oil Filter, detailing its features and applications. | 7th Dec 1937 | Box 135 \ 3 scan0195 | |
| Promotional leaflet for 'The Economy Filter', detailing its features, benefits, and operation. | 21th Dec 1937 | Box 135 \ 3 scan0196 | |
| The fitting of a Tecalemit filter during engine running-in and dynamometer tests. | 21th Dec 1937 | Box 135 \ 3 scan0197 | |
| Using Tecalemit Filters for chassis engine tests and the necessary precautions. | 22th Dec 1937 | Box 135 \ 3 scan0198 | |
| Quotation from S. Smith & Sons for 200 or 500 lots of No. 2 size Smith Oil Filters. | 28th Dec 1937 | Box 135 \ 3 scan0199 | |
| Letter to S. Smith & Sons requesting a quotation for 200 or 500 Engine Oil Filters while testing is underway. | 23th Dec 1937 | Box 135 \ 3 scan0200 | |
| Letter to C.W. Nichols of S. Smith & Sons regarding correspondence, pricing and design improvements for filter components from General Filters, Inc. | 30th Dec 1937 | Box 135 \ 3 scan0201 | |
| Letter to the AC-Sphinx Sparking Plug Co. regarding the favourable test results of their A.C. Filter and arranging a discussion based on price. | 31th Dec 1937 | Box 135 \ 3 scan0202 | |
| Requesting the setup of a test rig to compare four different brands of bye-pass oil filters. | 3rd Jan 1938 | Box 135 \ 3 scan0203 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. arranging a meeting to discuss the performance of their AC Oil Filters. | 3rd Jan 1938 | Box 135 \ 3 scan0204 | |
| Letter to C.N. Faulconbridge of AC-Sphinx Sparking Plug Co. Ltd. arranging a meeting to discuss the AC Oil Filter. | 4th Jan 1938 | Box 135 \ 3 scan0205 | |
| Technical description and operational guide for a general oil filter, including a cross-section diagram. | 4th Jan 1938 | Box 135 \ 3 scan0206 | |
| Cross-section diagram and operational description of a general oil filter. | 6th Jan 1938 | Box 135 \ 3 scan0207 | |
| Correspondence from S. Smith & Sons regarding a comparison of a General Filter design with their own. | 6th Jan 1938 | Box 135 \ 3 scan0208 | |
| Letter from S. Smith & Sons to W. A. Robotham regarding cost-saving design modifications and enclosing related documents. | 6th Jan 1938 | Box 135 \ 3 scan0209 | |
| Internal memorandum comparing the performance and longevity of their filter design against American competitor filters. | 5th Jan 1938 | Box 135 \ 3 scan0210 | |
| From S. Smith & Sons discussing the design principles of oil filters, including the texture of the cleaning element and maximising surface area. | 5th Jan 1938 | Box 135 \ 3 scan0211 | |
| Letter from Scammell Lorries to S. Smith & Sons about oil filter experiments and engine bore wear. | 28th Sep 1937 | Box 135 \ 3 scan0212 | |
| Inspection report detailing cylinder bore wear and crankshaft measurements. | 27th Aug 1937 | Box 135 \ 3 scan0213 | |
| Piston skirt dimensions and engine condition report for Chassis No. 8303/3. | 27th Aug 1937 | Box 135 \ 3 scan0214 | |
| Front cover of a leaflet for a Smith's Oil Filter. | 27th Aug 1937 | Box 135 \ 3 scan0215 | |
| The Smith Oil Filter, complete with laboratory and road test results. | 27th Aug 1937 | Box 135 \ 3 scan0216 | |
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