| Description | Date | Identifier | |
| Investigation into petrol supply failures on the Phantom model caused by air locks from fuel gassing and the subsequent solution. | 16th Nov 1928 | Box 44 \ 1 Scan257 | |
| Resolving air lock issues and petrol supply failures from the autovac tank. | 19th Nov 1928 | Box 44 \ 1 Scan258 | |
| Blueprint detailing a modification to a petrol supply system, increasing a release hole. | 19th Nov 1928 | Box 44 \ 1 Scan259 | |
| Modifications to address petrol supply failures caused by exhaust heat. | 1st Nov 1928 | Box 44 \ 1 Scan260 | |
| Fitment of Enots petrol filters on 40/50 chassis and the ventilation requirements for cars with cast dashboards. | 21th Nov 1928 | Box 44 \ 1 Scan261 | |
| Fitting Enots petrol filters to 40/50 chassis and reusing Zenith filters on 20 HP cars. | 21th Nov 1928 | Box 44 \ 1 Scan262 | |
| The fitting of a drain tap on the water pumps for Fairey machines. | 23th Nov 1928 | Box 44 \ 1 Scan263 | |
| Invoice and delivery discrepancy for special filters from Benton & Stone, Ltd. | 28th Nov 1928 | Box 44 \ 1 Scan264 | |
| Confirming the urgent dispatch of a third filter via special express parcel post. | 29th Nov 1928 | Box 44 \ 1 Scan265 | |
| Standardisation of an Enots petrol filter to replace the existing Zenith model. | 7th Dec 1928 | Box 44 \ 1 Scan266 | |
| Form for the standardisation of chassis parts. | 23th Nov 1928 | Box 44 \ 1 Scan267 | |
| Inquiry regarding the frequent choking of the petrol filter on Chassis No. 14.G.4. | 21th Jan 1929 | Box 44 \ 1 Scan268 | |
| Order for three Enots petrol filters with glass bowls and drawn aluminium bowls as extras. | 22th Jan 1929 | Box 44 \ 1 Scan269 | |
| On petrol filter issues in the 20 HP car, and the decision to standardise on the Enots filter for its greater capacity. | 22th Jan 1929 | Box 44 \ 1 Scan270 | |
| Petrol filter problems on the 20 HP model and the standardisation of the Enots filter. | 22th Jan 1929 | Box 44 \ 1 Scan271 | |
| Micro-examination report comparing the plate gaps of Zenith and Enots petrol filters. | 23th Jan 1929 | Box 44 \ 1 Scan272 | |
| Clarifying that a previous remark on 40/50 HP petrol filters was based on incorrect information and noting the trouble is attributed to dirty petrol. | 23th Jan 1929 | Box 44 \ 1 Scan273 | |
| Letter reporting on the testing of petrol filters, suggesting improvements to the filtering element's capacity and plate gaps. | 24th Jan 1929 | Box 44 \ 1 Scan274 | |
| Letter to Messrs. Benton & Stone discussing filter element specifications, comparing brass and duralumin plates. | 24th Jan 1929 | Box 44 \ 1 Scan275 | |
| Micro-examination report detailing measurements of gaps in a Zenith petrol filter. | 24th Jan 1929 | Box 44 \ 1 Scan276 | |
| Proposal to order Enots petrol filters for the J.2 series and 20 HP chassis. | 25th Jan 1929 | Box 44 \ 1 Scan277 | |
| The change of material for the Enots petrol filter element from duralumin to brass. | 26th Jan 1929 | Box 44 \ 1 Scan278 | |
| Changing the material for the Enots petrol filter from duralumin to brass plates. | 26th Jan 1929 | Box 44 \ 1 Scan279 | |
| Letter from Benton & Stone Ltd. regarding the production of petrol filters and duralumin filter plates. | 28th Jan 1929 | Box 44 \ 1 Scan280 | |
| Ordering of Enots petrol filters and awaiting further details on the filtering element. | 14th Feb 1929 | Box 44 \ 1 Scan281 | |
| Letter from Guthrie & Co. Chemical Engineers proposing a new filtration material for petrol, oil, air, and diesel oil. | 26th Feb 1929 | Box 44 \ 1 Scan282 | |
| Page 2 of a letter from Guthrie & Co. promoting a new filter for petrol, oil, and air. | 26th Feb 1929 | Box 44 \ 1 Scan283 | |
| Blueprint showing the design and dimensions for a petrol and benzine filter. | 28th Feb 1929 | Box 44 \ 1 Scan284 | |
| Letter to Messrs. Benton & Stone Ltd. regarding a modified filter element required for testing and standardisation. | 28th Feb 1929 | Box 44 \ 1 Scan285 | |
| Letter from Benton & Stone Ltd. regarding production issues and the upcoming despatch of modified filter elements. | 1st Mar 1929 | Box 44 \ 1 Scan286 | |
| Instruction to fit two Enots petrol filters to cars 20-EX and 22-EX. | 8th Mar 1929 | Box 44 \ 1 Scan287 | |
| Letter to Benton & Stone Ltd. regarding corroded duralumin filter elements from fuel tests, suggesting a reversion to brass plates. | 15th Mar 1929 | Box 44 \ 1 Scan288 | |
| Letter from Benton & Stone Ltd. discussing the testing of dural filter elements and the switch to brass plates for production. | 18th Mar 1929 | Box 44 \ 1 Scan289 | |
| Test report on the performance and restriction of different types of Enot's petrol filters. | 1st Apr 1930 | Box 44 \ 1 Scan290 | |
| Letter to supplier Benton & Stone Ltd. regarding performance issues and requested improvements for filter element packs. | 9th Apr 1929 | Box 44 \ 1 Scan291 | |
| Letter from Benton & Stone Ltd. concerning the production and testing of petrol filters. | 10th Apr 1929 | Box 44 \ 1 Scan292 | |
| On laboratory corrosion tests of duralumin filter plates, recommending the use of brass packs for the first batch of filters. | 1st Apr 1929 | Box 44 \ 1 Scan293 | |
| Letter to Messrs. Benton & Stone Ltd. clarifying that filter packs should continue to be supplied in brass, not duralumin. | 11th Apr 1929 | Box 44 \ 1 Scan294 | |
| Oil filter, forwarding a letter for discussion and comments. | 16th Apr 1929 | Box 44 \ 1 Scan295 | |
| Letter from the American branch to the English branch regarding the development of oil filters and a request for new designs. | 5th Apr 1929 | Box 44 \ 1 Scan296 | |
| Clarifying the terminology of oil 'filters' versus 'strainers' and discussing various oil cleaning technologies. | 17th Apr 1929 | Box 44 \ 1 Scan297 | |
| Correcting a previous postscript regarding oil filter manufacturers, 'Auto Klean' and 'Streamline'. | 19th Apr 1929 | Box 44 \ 1 Scan298 | |
| Advantages and disadvantages of the Auto Klean oil filter. | 22th Apr 1929 | Box 44 \ 1 Scan299 | |
| The merits of externally-cleanable oil filters, referencing Zenith, Enots and Auto Klean types. | 22th Apr 1929 | Box 44 \ 1 Scan300 | |
| Performance, advantages and disadvantages of the Auto Klean filter. | 22th Apr 1929 | Box 44 \ 1 Scan301 | |
| Oil sump filters and the benefit of externally cleaned filters, referencing the Auto Klean filter on a Sunbeam car. | 3rd May 1929 | Box 44 \ 1 Scan302 | |
| Comparing the Cuno and Purolator oil filters, discussing weight, materials, and cost. | 3rd May 1929 | Box 44 \ 1 Scan303 | |
| Seeking clarification on the difference between Cuno Auto-Klean and Auto-Klean oil filters. | 8th May 1929 | Box 44 \ 1 Scan304 | |
| Letter discussing the performance and testing of a Cuno Auto-Klean oil filter, with an analysis of residue collected. | 30th Apr 1929 | Box 44 \ 1 Scan305 | |
| Page two of a letter discussing the high cost of filters compared to competitors and sourcing alternatives. | 11th May 1929 | Box 44 \ 1 Scan306 | |
| Sending a sample 'Auto Klean' lubricating oil strainer with accompanying drawings. | 11th May 1929 | Box 44 \ 1 Scan307 | |
| The testing of Cuno Auto-Klean filters and the similarity between the American and English versions. | 14th May 1929 | Box 44 \ 1 Scan308 | |
| Letter to Messrs. Benton & Stone Ltd. regarding petrol starvation issues caused by Enots Petrol Filters. | 7th Nov 1929 | Box 44 \ 1 Scan309 | |
| Letter from Benton & Stone Ltd. regarding issues and testing of 'Enots' petrol filters. | 8th Nov 1929 | Box 44 \ 1 Scan310 | |
| Sending a petrol level indicator back to Messrs. Claudel Hobson after testing. | 5th Jul 1926 | Box 44 \ 2 Scan001 | |
| Letter from H.M. Hobson Ltd. confirming readiness to proceed with sample gauges upon receipt of specifications. | 20th Jul 1926 | Box 44 \ 2 Scan002 | |
| Letter to H. M. Hobson, Ltd. regarding a delay in developing a dashboard reading petrol gauge. | 19th Jul 1926 | Box 44 \ 2 Scan003 | |
| Internal order request for one complete Hobson Telegauge from Messrs. Claudel Hobson. | 8th Nov 1926 | Box 44 \ 2 Scan004 | |
| Request for the results of experiments on a dashboard-affixed Claudel-Hobson petrol gauge. | 12th Nov 1926 | Box 44 \ 2 Scan005 | |
| Request for information regarding an erratically behaving 'King Seeley' petrol gauge. | 18th Nov 1926 | Box 44 \ 2 Scan006 | |
| Letter from H.M. Hobson concerning an erratically behaving Hobson K-S Petrol Telegage instrument. | 19th Nov 1926 | Box 44 \ 2 Scan007 | |
| Page 2 of a letter from H.M. Hobson, Ltd. regarding the installation and trial of gauges on a 20 HP chassis. | 19th Nov 1926 | Box 44 \ 2 Scan008 | |
| Letter from H.M. Hobson Ltd. regarding the fitting and calibration of parts for a 20 HP experimental car's petrol tank. | 25th Nov 1926 | Box 44 \ 2 Scan009 | |
| Letter from H.M. Hobson Ltd. regarding the trial and calibration of fuel gauges for a 40/50 HP car. | 25th Nov 1926 | Box 44 \ 2 Scan010 | |
| Performance of Claudel Hobson petrol gauges fitted to Phantom and 20 HP cars. | 29th Nov 1926 | Box 44 \ 2 Scan011 | |
| Letter from H.M. Hobson Ltd. regarding Hobson K-S Telegage service or correction sheets for 'Phantom' and 20 HP cars. | 23th Dec 1926 | Box 44 \ 2 Scan012 | |
| Asking for an opinion on the newly manufactured King Seeley Petrol Level Indicator. | 24th Dec 1926 | Box 44 \ 2 Scan013 | |
| Test report on the Hobson K-S petrol level indicator fitted to experimental cars. | 24th Dec 1926 | Box 44 \ 2 Scan014 | |
| Alteration to the instrument board for the 10-EX Sports Phantom, specifically the dimensions for an oval petrol gauge. | 30th Dec 1926 | Box 44 \ 2 Scan015 | |
| Letter to H.M. Hobson Ltd. inquiring about calibrating a new model fuel tank and the potential for a custom dashboard gauge. | 30th Dec 1926 | Box 44 \ 2 Scan016 | |
| Letter from H.M. Hobson Ltd. regarding the calibration of a Hobson K-S Petrol Telegage and unsatisfactory instrument masks for the Phantom model. | 31th Dec 1926 | Box 44 \ 2 Scan017 | |
| Letter discussing the design and production of gauge masks for a 20-gallon fuel tank. | 31th Dec 1926 | Box 44 \ 2 Scan018 | |
| Letter from H.M. Hobson, Ltd. regarding a fuel tank modification and a sample mask for a 40/50 HP car. | 31th Dec 1926 | Box 44 \ 2 Scan019 | |
| Letter to H.M. Hobson Ltd. regarding the design, specifications, and fitting of a K-S Telegage. | 1st Jan 1927 | Box 44 \ 2 Scan020 | |
| The despatch of K-S Telegage parts to Messrs. H.M. Hobson Ltd. | 1st Jan 1927 | Box 44 \ 2 Scan021 | |
| Letter from H.M. Hobson, Ltd. apologising for a delayed response and requesting to postpone a matter until the following day. | 4th Jan 1927 | Box 44 \ 2 Scan022 | |
| Letter from H.M. Hobson Ltd. arranging to fit a Hobson K-S Telegage and dash-board unit to a car. | 5th Jan 1927 | Box 44 \ 2 Scan023 | |
| Correspondence from H.M. Hobson Ltd. regarding the Hobson K-S Telegage, discussing fitting arrangements and pricing for an improved gauge. | 6th Jan 1927 | Box 44 \ 2 Scan024 | |
| Page 2 of a letter from H.M. Hobson, Ltd. detailing a price reduction on gauges. | 6th Jan 1927 | Box 44 \ 2 Scan025 | |
| Letter to H.M. Hobson Ltd. regarding the supply, fitting, and design of a fuel gauge for a 40/50 HP car. | 8th Jan 1927 | Box 44 \ 2 Scan026 | |
| Letter to H.M. Hobson Co. Ltd. regarding an objection to the oval case of the King Seeley Petrol Gauge and requesting a new rectangular design. | 14th Jan 1927 | Box 44 \ 2 Scan027 | |
| Letter from H.M. Hobson Ltd. discussing the installation of a Hobson K-S Telegage and requesting a tank drawing. | 10th Jan 1927 | Box 44 \ 2 Scan028 | |
| Letter from H.M. Hobson, Ltd. discussing the disposition of an overflow pipe and gauge face dimensions. | 10th Jan 1927 | Box 44 \ 2 Scan029 | |
| Inter-office inquiry regarding the King Seeley Petrol Level Indicator. | 17th Jan 1927 | Box 44 \ 2 Scan030 | |
| Inquiry from the American branch to the English branch regarding a King Seeley Petrol Level Indicator. | 17th Jan 1927 | Box 44 \ 2 Scan031 | |
| Inquiry from Rolls-Royce of America to the UK regarding particulars for the King Seeley Petrol Level Indicator. | 17th Jan 1927 | Box 44 \ 2 Scan032 | |
| Letter from the American branch to the UK branch regarding fuel level indicators. | 18th Jan 1927 | Box 44 \ 2 Scan033 | |
| Letter from H.M. Hobson, Ltd. enclosing a blueprint showing five samples of dashboard units for the Hobson K-S Telegage. | 19th Jan 1927 | Box 44 \ 2 Scan034 | |
| Blueprint showing five different designs for the Hobson K.S. Telegage fuel gauge. | 20th Jan 1927 | Box 44 \ 2 Scan035 | |
| Selecting the best K.S. Telegage face from blueprints provided by Claudel Hobson for an instrument board. | 20th Jan 1927 | Box 44 \ 2 Scan036 | |
| Letter to H.M. Hobson Ltd. regarding parts for a King Seeley Petrol Gauge for a 10 HP Fiat car. | 20th Jan 1927 | Box 44 \ 2 Scan037 | |
| Letter from H.M. Hobson Ltd. acknowledging receipt of a letter and confirming they have written to Mr. A.G. Elliott regarding a Hobson K-S Telegage. | 24th Jan 1927 | Box 44 \ 2 Scan038 | |
| Letter to H.M. Hobson Ltd. regarding the fitting position of a Hobson Telegage for a 40/50 HP car. | 27th Jan 1927 | Box 44 \ 2 Scan039 | |
| The King Seeley (K-S) petrol level indicator, discussing its performance, calibration, and potential improvements. | 2nd Feb 1927 | Box 44 \ 2 Scan040 | |
| The testing of a Hobson K-S petrol level indicator on two experimental cars. | 24th Dec 1926 | Box 44 \ 2 Scan041 | |
| The design and calibration of a Claudel Hobson dash board petrol gauge. | 5th Feb 1927 | Box 44 \ 2 Scan042 | |
| Letter to Messrs. H.M. Hobson Ltd. regarding carburettor tests, a telegage unit for a 20 HP car, and delays with a 40/50 HP car. | 12th Feb 1927 | Box 44 \ 2 Scan043 | |
| Blueprint detailing the calibration of a Goshawk petrol tank. | 12th Feb 1927 | Box 44 \ 2 Scan044 | |
| Letter from H.M. Hobson, Ltd. regarding a discrepancy with a Telegage unit for a 20 HP car. | 14th Feb 1927 | Box 44 \ 2 Scan045 | |
| Page 2 of a letter from H. M. Hobson, Ltd. regarding 40/50 tank calibration. | 14th Feb 1927 | Box 44 \ 2 Scan046 | |
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