| Description | Date | Identifier | |
| Letter from H.M. Hobson, Ltd. confirming the preparation of two samples of altered pressure balance connections and joints for approval. | 30th Nov 1929 | Box 44 \ 4 Scan144 | |
| Suitability of fitting a bevelled glass to a Hobson Telegauge instrument. | 4th Dec 1929 | Box 44 \ 4 Scan145 | |
| Letter from H.M. Hobson Ltd. discussing modifications to the Hobson K-S Telegage petrol gauge. | 4th Dec 1929 | Box 44 \ 4 Scan146 | |
| Modifications to a gauge, including a new packing gland and a change of material from aluminium to gun-metal. | 4th Dec 1929 | Box 44 \ 4 Scan147 | |
| Procedure to prevent liquid blockage in gauges and a note on a support for an armoured casing. | 4th Dec 1929 | Box 44 \ 4 Scan148 | |
| New fixing methods, including a 'pinch' fixing and a spring type speedometer clip for instrument installation. | 4th Dec 1929 | Box 44 \ 4 Scan149 | |
| Letter from H.M. Hobson, Ltd. regarding modifications to gauge sets and their delivery for inspection. | 4th Dec 1929 | Box 44 \ 4 Scan150 | |
| Confirming the tracing and receipt of petrol gauges. | 8th Nov 1929 | Box 44 \ 4 Scan151 | |
| Confirming the debiting of traced petrol telegage parts to the Experimental Department. | 9th Nov 1929 | Box 44 \ 4 Scan152 | |
| Payment for faulty petrol gauges that failed during a 10,000-mile test. | 11th Nov 1929 | Box 44 \ 4 Scan153 | |
| Letter to H.M. Hobson Ltd. regarding modifications to two 40/50 heads and a fused connection for a glass tube. | 7th Jan 1930 | Box 44 \ 4 Scan154 | |
| Correspondence with H.M. Hobson Ltd. regarding a petrol gauge head for Mr. Royce's car and an outstanding invoice. | 7th Jan 1930 | Box 44 \ 4 Scan155 | |
| Letter discussing the performance and reliability of fuel gauges and comparing them to the K.S. Hobson Telegage. | 13th Jan 1930 | Box 44 \ 4 Scan156 | |
| Notes on fuel vapor pressure, air surging in fuel lines, and improvements to the Sprengel pump system. | 13th Jan 1930 | Box 44 \ 4 Scan157 | |
| Potential issues and improvements for fuel system components like pumps, gauges, and tanks. | 13th Jan 1930 | Box 44 \ 4 Scan158 | |
| Summary of suggestions and criticisms regarding the Hobson gauge system. | 16th Jan 1930 | Box 44 \ 4 Scan159 | |
| Letter to Messrs. H.M. Hobson Ltd. regarding failures in K. S. petrol gauges, including one on the Prince of Wales' car. | 16th Jan 1930 | Box 44 \ 4 Scan160 | |
| Letter to H.M. Hobson Ltd. clarifying a statement about car failures, noting experimental cars have been trouble-free and referencing the Prince of Wales' car. | 21th Jan 1930 | Box 44 \ 4 Scan161 | |
| Letter from H.M. Hobson, Ltd. regarding a delay in modifying two K-S Telegages due to pattern alterations. | 20th Jan 1930 | Box 44 \ 4 Scan162 | |
| Letter discussing the investigation of gauge failures in customer cars, including one belonging to the Prince of Wales. | 20th Jan 1930 | Box 44 \ 4 Scan163 | |
| Inspection report for a faulty dashboard gauge on car No. 128WJ, caused by accidental damage during other work. | 20th Jan 1930 | Box 44 \ 4 Scan164 | |
| Letter from H.M. Hobson, Ltd. concerning a gauge failure in the Prince of Wales' car. | 20th Jan 1930 | Box 44 \ 4 Scan165 | |
| Letter from H.M. Hobson Ltd. concerning the modification of test gauges and sample spring fixings. | 10th Jan 1930 | Box 44 \ 4 Scan166 | |
| Letter from H.M. Hobson Ltd. discussing gauge modification and construction methods. | 10th Jan 1930 | Box 44 \ 4 Scan167 | |
| Letter from H.M. Hobson, Ltd. concerning modified Telegages for trial cars, detailing issues with bezel finish and a new spring clip design. | 22th Jan 1930 | Box 44 \ 4 Scan168 | |
| Modification of capillary tubes for gauges and requesting further vehicle testing. | 22th Jan 1930 | Box 44 \ 4 Scan169 | |
| Page 3 of a letter from H.M. Hobson, Ltd. regarding the installation of a capillary tube. | 22th Jan 1930 | Box 44 \ 4 Scan170 | |
| Letter from H.M. Hobson Ltd. discussing troubleshooting issues with cars, while noting experimental models are performing well. | 22th Jan 1930 | Box 44 \ 4 Scan171 | |
| Letter from H.M. Hobson, Ltd. regarding the gauge from the Prince of Wales' car. | 22th Jan 1930 | Box 44 \ 4 Scan172 | |
| Letter to H.M. Hobson Ltd. regarding a potentially faulty telegauge head from the Prince of Wales' car, 115-WJ. | 22th Jan 1930 | Box 44 \ 4 Scan173 | |
| Letter from H.M. Hobson, Ltd. about a missing Telegage for the Prince of Wales's car. | 24th Jan 1930 | Box 44 \ 4 Scan174 | |
| Letter from H.M. Hobson, Ltd. regarding a faulty dash instrument from the Prince of Wales' car. | 29th Jan 1930 | Box 44 \ 4 Scan175 | |
| Letter from H.M. Hobson, Ltd. discussing the need to correct a gauge installation upon the fitting of a new head. | 29th Jan 1930 | Box 44 \ 4 Scan176 | |
| Letter from H.M. Hobson, Ltd. about a modification to two experimental gauge heads. | 3rd Feb 1930 | Box 44 \ 4 Scan177 | |
| Page 2 of a letter from H.M. Hobson Ltd. regarding screw tension in armoured covering and testing an alteration. | 3rd Feb 1930 | Box 44 \ 4 Scan178 | |
| Despatch of gauge heads for modification and the return of other loaned parts. | 7th Jan 1930 | Box 44 \ 4 Scan179 | |
| With notes on the Hobson K.S. petrol gauge for an instruction book. | 17th May 1929 | Box 44 \ 4 Scan180 | |
| Description of the working principle of the Hobson Petrol Gauge. | 17th May 1929 | Box 44 \ 4 Scan181 | |
| Description of a petrol gauge's capillary tube and hand pump unit operation. | 17th May 1929 | Box 44 \ 4 Scan182 | |
| Troubleshooting guide for a vehicle gauge, outlining issues such as wet or leaking air lines. | 17th May 1929 | Box 44 \ 4 Scan183 | |
| Page listing the advantages of the R.R. KS. petrol gauge. | 7th May 1929 | Box 44 \ 4 Scan184 | |
| Providing fitting instructions for a Hobson Petrol Gauge on a 17-EX car chassis. | 7th May 1929 | Box 44 \ 4 Scan185 | |
| Instructions for connecting the tank unit and clearing the air line for an erratic petrol gauge. | 17th May 1929 | Box 44 \ 4 Scan186 | |
| Letter from H.M. Hobson Ltd. regarding an amended dial drawing to include markings for 'Gallons' and 'Litres'. | 17th May 1929 | Box 44 \ 4 Scan187 | |
| Letter to H.M. Hobson Ltd. concerning the supply and marking of K.S. Telegages for patch instruments. | 18th May 1929 | Box 44 \ 4 Scan188 | |
| Requesting engraved dials for Hobson petrol gauges and an order for masks for patch instrument N.SCH.2836. | 18th May 1929 | Box 44 \ 4 Scan189 | |
| Letter from H.M. Hobson Ltd. regarding the examination and repair of a faulty K.S. 180 gauge. | 18th May 1929 | Box 44 \ 4 Scan190 | |
| Letter from H.M. Hobson Ltd. querying a potential mistake in an order for three gauges. | 24th May 1929 | Box 44 \ 4 Scan191 | |
| Letter from H.M. Hobson, Ltd. requesting a drawing showing additional lugs for fixing an instrument patch. | 24th May 1929 | Box 44 \ 4 Scan192 | |
| To clarify a parts order, specifying the need for 3 cream masks for petrol gauges, not 3 complete gauges. | 25th May 1929 | Box 44 \ 4 Scan193 | |
| Confirming an order of three cream masks for Hobson petrol gauges. | 27th May 1929 | Box 44 \ 4 Scan194 | |
| Letter from H.M. Hobson, Ltd. regarding drawings for a petrol gauge and correcting a drawing number. | 30th May 1929 | Box 44 \ 4 Scan195 | |
| Letter to Messrs. H.M. Hobson Ltd. regarding details for a KS petrol gauge for fitting to a patch instrument board. | 28th May 1929 | Box 44 \ 4 Scan196 | |
| Letter from H.M. Hobson, Ltd. querying a dimension discrepancy on a drawing for an instrument patch casting. | 3rd Jun 1929 | Box 44 \ 4 Scan197 | |
| The concluding page of a letter from H.M. Hobson, Ltd., regarding a dial support. | 3rd Jun 1929 | Box 44 \ 4 Scan198 | |
| Internal order for one complete Hobson petrol gauge for a patch instrument board. | 6th Jun 1929 | Box 44 \ 4 Scan199 | |
| Correction sheet with troubleshooting and repair instructions for the Hobson K-S Telegage fuel gauge system. | 6th Jun 1929 | Box 44 \ 4 Scan200 | |
| Diagram sheet explaining the operation of the Hobson K-S Telegage fuel gauge system. | 6th Jun 1929 | Box 44 \ 4 Scan201 | |
| Operation instructions for the Hobson K-S Telegage fuel gauge system. | 3rd Jun 1929 | Box 44 \ 4 Scan202 | |
| Letter to Messrs. H.M. Hobson Ltd. requesting to expedite a 20 HP car for Mr. Royce. | 3rd Jun 1929 | Box 44 \ 4 Scan203 | |
| Letter from H.M. Hobson, Ltd. regarding progress on a gauge for Mr. Royce's 20 HP car. | 4th Jun 1929 | Box 44 \ 4 Scan204 | |
| Letter returning a sketch with a missing dimension of 19/32'. | 7th Jun 1929 | Box 44 \ 4 Scan205 | |
| Petrol gauge calibration issue on a 20-HP chassis and the proposed solution. | 10th May 1929 | Box 44 \ 4 Scan206 | |
| Letter from H.M. Hobson, Ltd. confirming the dispatch of a tank unit and air line for a 20 HP car gauge, with the gauge itself and a special dial to follow. | 11th Jun 1929 | Box 44 \ 4 Scan207 | |
| Telegram received by telephone concerning the dispatch of a 'toukunit' and a hold up on a dash unit. | 11th Jun 1929 | Box 44 \ 4 Scan208 | |
| Letter discussing a fix for an air leak in a Telegage pressure line and a replacement hand pump. | 24th Jun 1929 | Box 44 \ 4 Scan209 | |
| Letter from H.M. Hobson Ltd. regarding an issue with hard enamelled dials for 40/50 HP and 20 HP instruments that cannot be drilled. | 13th Jun 1929 | Box 44 \ 4 Scan210 | |
| Letter from H.M. Hobson, Ltd. regarding a delay in producing drilled dials due to a special enamel finish. | 13th Jun 1929 | Box 44 \ 4 Scan211 | |
| Letter from H.M. Hobson, Ltd. discussing modifications to a pump to make it lighter and improve the knob fixing. | 17th Jun 1929 | Box 44 \ 4 Scan212 | |
| Post Office telegram regarding the dispatch of a 'towkunit' and airlines, with a delay on the 'dash unit'. | 29th Mar 1928 | Box 44 \ 4 Scan213 | |
| Letter from H.M. Hobson Ltd. regarding issues with a replacement dial for a patch instrument for Mr. Royce's car. | 24th Jun 1929 | Box 44 \ 4 Scan214 | |
| Letter from H.M. Hobson, Ltd. regarding the replacement and installation of an instrument dial for Mr. Royce's car. | 24th Jun 1929 | Box 44 \ 4 Scan215 | |
| Letter to Major T.P. Searight concerning failures of K.S. petrol gauges. | 12th Jul 1929 | Box 44 \ 4 Scan216 | |
| Telegram regarding the dispatch of a tank unit and other items to France. | 18th Jul 1929 | Box 44 \ 4 Scan217 | |
| Request to Claudel-Hobson Ltd. to urgently send a tank unit and Triple Air Line to a representative in France for car KS 180 P. | 18th Jul 1929 | Box 44 \ 4 Scan218 | |
| Letter from H.M. Hobson Ltd. regarding the correct fitting of plugs and caps on chassis before shipment. | 18th Jul 1929 | Box 44 \ 4 Scan219 | |
| Concluding page of a letter to W. A. Robotham regarding despatch to coachbuilders. | 18th Jul 1929 | Box 44 \ 4 Scan220 | |
| Letter of enquiry to Messrs. Peto & Radford regarding the use of Cadmium Electrodes for testing accumulator cells. | 24th Jan 1928 | Box 44 \ 5 Scan001 | |
| Letter from Peto & Radford regarding the use of Cadmium Electrodes for testing accumulator plates. | 28th Jan 1925 | Box 44 \ 5 Scan002 | |
| Letter from Peto & Radford regarding the use of Cadmium in testing starter batteries. | 28th Jan 1925 | Box 44 \ 5 Scan003 | |
| Letter discussing the use and interpretation of readings from a cadmium electrode for secondary batteries. | 29th Jan 1925 | Box 44 \ 5 Scan004 | |
| Letter discussing the practical value and purpose of a cadmium stick. | 29th Jan 1925 | Box 44 \ 5 Scan005 | |
| Laboratory report on the impurities found in a Cadmium Rod sample. | 2nd Sep 1925 | Box 44 \ 5 Scan006 | |
| The interpretation of voltage readings in a secondary cell using a cadmium electrode. | 2nd Sep 1925 | Box 44 \ 5 Scan007 | |
| Page detailing the correct condition of battery elements during discharge. | 1st Sep 1925 | Box 44 \ 5 Scan008 | |
| Chart of readings for use with a Cadmium Electrode Voltmeter, showing voltage ranges for good cells. | 1st Sep 1925 | Box 44 \ 5 Scan009 | |
| The machining properties of cadmium, noting its softness and tendency to bend. | 7th Dec 1925 | Box 44 \ 5 Scan010 | |
| The investigation into the utility of the cadmium electrode to test the condition of any cell. | 1st Sep 1925 | Box 44 \ 5 Scan011 | |
| Table of test results for various types of electrical cells under different conditions. | 22th Apr 1926 | Box 44 \ 5 Scan012 | |
| Explaining the use of a cadmium electrode to test the electrical condition of positive and negative battery plates. | 22th Apr 1926 | Box 44 \ 5 Scan013 | |
| Page of test readings for various types of electrical cells showing their condition and voltage readings. | 26th Apr 1926 | Box 44 \ 5 Scan014 | |
| Using a cadmium electrode for testing accumulator element condition. | 26th Apr 1926 | Box 44 \ 5 Scan015 | |
| Continued document discussing battery cell design, ribbed separators, and voltage readings using a cadmium electrode. | 26th Apr 1925 | Box 44 \ 5 Scan016 | |
| Table of test results for various battery cells under different conditions, with a recommendation for testing methodology. | 26th Apr 1926 | Box 44 \ 5 Scan017 | |
| Data sheet showing cadmium readings for various types of battery cells. | 1st Nov 1927 | Box 44 \ 5 Scan018 | |
| Instructions regarding Cadmium readings on batteries under various charge and discharge conditions. | 26th Oct 1927 | Box 44 \ 5 Scan019 | |
| Set of crucial instructions and maintenance advice for accumulator users. | 2nd Dec 1927 | Box 44 \ 5 Scan020 | |
| Set of instructions on how to store a battery (accumulator) and warnings about potential damage from improper maintenance. | 2nd Dec 1927 | Box 44 \ 5 Scan021 | |
| Page discussing the diagnosis and faults of accumulator (battery) plates. | 2nd Dec 1927 | Box 44 \ 5 Scan022 | |
| Cautionary note on purchasing accumulators with celluloid components. | 2nd Dec 1927 | Box 44 \ 5 Scan023 | |
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