| Description | Date | Identifier | |
| Satisfactory performance of the S.2.C.A. car heater and inquiring about negotiations regarding rheostatic switches. | 26th Sep 1938 | Box 137 \ 2 scan0161 | |
| The supply and fitting of rheostats for car heaters. | 29th Sep 1938 | Box 137 \ 2 scan0162 | |
| Letter to AC-Sphinx Sparking Plug Co. regarding noise issues with car heaters and requesting alternative motors for testing. | 6th Oct 1938 | Box 137 \ 2 scan0163 | |
| Follow-up letter requesting quotations for heaters and rheostats with specific component requirements. | 6th Oct 1938 | Box 137 \ 2 scan0164 | |
| Modifying a Vauxhall 25 HP AC car heater to reduce motor noise for use in Rolls-Royce cars. | 6th Oct 1938 | Box 137 \ 2 scan0165 | |
| Request to place an official order for car heater components from AC-Sphinx Sparking Plug Co. Ltd. for experimental purposes. | 6th Oct 1938 | Box 137 \ 2 scan0166 | |
| Request to send an official order to Messrs. Gamages for an electric car fan for demisting purposes. | 6th Oct 1938 | Box 137 \ 2 scan0167 | |
| Letter from the Experimental Department to Gamages Ltd requesting a sample of an electric car fan. | 6th Oct 1938 | Box 137 \ 2 scan0168 | |
| Quotation from S. Smith & Sons for a small De-froster Blower. | 6th Oct 1938 | Box 137 \ 2 scan0169 | |
| Dispatch of blueprints for a car-heater and defroster spindle. | 7th Oct 1938 | Box 137 \ 2 scan0170 | |
| Letter to AC.Sphinx Sparking Plug Co. querying a potential typographical error in a quotation for rheostatic switches. | 7th Oct 1938 | Box 137 \ 2 scan0171 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. regarding the supply and specification of heater unit motors. | 8th Oct 1938 | Box 137 \ 2 scan0172 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding fan spindle vibration in car heater motors. | 11th Oct 1938 | Box 137 \ 2 scan0173 | |
| Letter to AC-Sphinx Sparking Plug Co. discussing the application and modification of their car heater. | 12th Oct 1938 | Box 137 \ 2 scan0174 | |
| Request for the supply of various heater, radiator, and motor components for a production proposition. | 12th Oct 1938 | Box 137 \ 2 scan0175 | |
| Modifications to the heating and ventilating system on car 28.G.VI. | 12th Oct 1938 | Box 137 \ 2 scan0176 | |
| Letter to AC-Sphinx Sparking Plug Co. requesting a heater defrosting attachment and information on flexible hose suppliers. | 13th Oct 1938 | Box 137 \ 2 scan0177 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding the supply of special motors for car heaters and arranging a meeting. | 18th Oct 1938 | Box 137 \ 2 scan0178 | |
| Parts list and instructions for a Bentley 50 car heater and dashboard arrangement. | 18th Oct 1938 | Box 137 \ 2 scan0179 | |
| Request to send an official order to The AC-Sphinx Sparking Plug Co. Ltd. for a defroster attachment. | 19th Oct 1938 | Box 137 \ 2 scan0180 | |
| Requesting the production of four sets of parts for heaters for testing and specific car models. | 19th Oct 1938 | Box 137 \ 2 scan0181 | |
| Letter to AC-Sphinx Sparking Plug Co. Ltd. arranging a meeting at Earl's Court. | 19th Oct 1938 | Box 137 \ 2 scan0182 | |
| Letter from The British Thermostat Co., Ltd. regarding the supply of rheostats for car heaters. | 20th Oct 1938 | Box 137 \ 2 scan0183 | |
| Requesting an official order for heater parts from AC-Sphinx Sparking Plug Co. Ltd. | 24th Oct 1938 | Box 137 \ 2 scan0184 | |
| Letter from AC-Sphinx to Rolls-Royce discussing Oil Pressure Switches, Thermostats, and Car Heater tests. | 27th Oct 1938 | Box 137 \ 2 scan0185 | |
| Requesting feedback on de-frosters used on experimental cars to aid in standardisation. | 27th Oct 1938 | Box 137 \ 2 scan0186 | |
| Letter to AC-Sphinx Sparking Plug Co. Ltd. discussing thermostat schemes, warning lights, and car heaters for Bentley cars. | 28th Oct 1938 | Box 137 \ 2 scan0187 | |
| Typed letter discussing a proposed spigot size and requesting an alternative. | 28th Oct 1938 | Box 137 \ 2 scan0188 | |
| Letter to The Leyland & Birmingham Rubber Co. Ltd. regarding an unsatisfactory flexible rubber hose for car heater duct connections. | 31th Oct 1938 | Box 137 \ 2 scan0189 | |
| Letter to The British Tyre & Rubber Co. Ltd. requesting a sample of flexible corrugated hose for experimental purposes. | 31th Oct 1938 | Box 137 \ 2 scan0190 | |
| Letter to The Avon India Rubber Co. Ltd. requesting a supply of flexible corrugated hose for experimental purposes. | 31th Oct 1938 | Box 137 \ 2 scan0191 | |
| Letter to Dunlop Rubber Co. Ltd. inquiring about the supply of flexible corrugated hose for experimental purposes. | 31th Oct 1938 | Box 137 \ 2 scan0192 | |
| Letter from the Experimental Department to Goodyear Tyre & Rubber Co. Ltd. requesting flexible hose for experimental purposes. | 31th Oct 1938 | Box 137 \ 2 scan0193 | |
| Letter from The Avon India Rubber Co. Ltd. responding to a request for a special flexible rubber and canvas corrugated hose. | 1st Nov 1938 | Box 137 \ 2 scan0194 | |
| Letter from The British Thermostat Co., Ltd. regarding issues with rheostats and the supply of an experimental thermostat. | 1st Nov 1938 | Box 137 \ 2 scan0195 | |
| Page two of a letter discussing the manufacturing of diaphragm bellows for thermostats. | 1st Nov 1938 | Box 137 \ 2 scan0196 | |
| Letter from Dunlop Rubber Co. Ltd. acknowledging a request for a sample of Flexible Hose. | 1st Nov 1938 | Box 137 \ 2 scan0197 | |
| Letter from British Tyre & Rubber Co. Ltd. regarding the supply and price of a special corrugated hose for ventilating and heating purposes. | 2nd Nov 1938 | Box 137 \ 2 scan0198 | |
| Letter concerning a sample of 3' diameter flexible rubber hose for car heater duct connections. | 2nd Nov 1938 | Box 137 \ 2 scan0199 | |
| Letter from Goodyear regarding an enquiry for rubber hose, suggesting sourcing it from their Canadian factory. | 2nd Nov 1936 | Box 137 \ 2 scan0200 | |
| Letter from The Avon India Rubber Co. declining to supply a specific type of flexible rubber hose due to not being equipped for its manufacture. | 2nd Nov 1938 | Box 137 \ 2 scan0201 | |
| Requesting modifications to a car's heating system to eliminate noise and smell. | 2nd Nov 1938 | Box 137 \ 2 scan0202 | |
| Letter from The British Thermostat Co., Ltd. regarding the return of two rheostats. | 4th Nov 1938 | Box 137 \ 2 scan0203 | |
| Letter from Dunlop Rubber Co. Ltd. regarding samples of flexible hose for heating and ventilating purposes. | 4th Nov 1938 | Box 137 \ 2 scan0204 | |
| Letter from Dunlop Rubber Co. regarding samples and awaiting a report for further suggestions. | 4th Nov 1938 | Box 137 \ 2 scan0205 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. regarding car heater parts and test results. | 4th Nov 1938 | Box 137 \ 2 scan0206 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding heaters, thermostats, and warning lights. | 5th Nov 1938 | Box 137 \ 2 scan0207 | |
| Letter to The British Thermostat Co. Ltd. about testing rheostats for car heaters and the reliability of bellows. | 5th Nov 1938 | Box 137 \ 2 scan0208 | |
| Request to issue a covering order for 3ft of 3' car heater hose already ordered and received. | 8th Nov 1938 | Box 137 \ 2 scan0209 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. detailing the test results for high and slow speed heater motors. | 9th Nov 1938 | Box 137 \ 2 scan0210 | |
| Letter from the AC-Sphinx Sparking Plug Co. Ltd. regarding modifications and performance of vehicle heaters. | 9th Nov 1938 | Box 137 \ 2 scan0211 | |
| Letter from S. Smith & Sons regarding a delay in producing a sample heater and discussing test results and alternative designs. | 9th Nov 1938 | Box 137 \ 2 scan0212 | |
| Letter from S. Smith & Sons regarding a sample heater to be fitted on the inside of a bulkhead. | 9th Nov 1938 | Box 137 \ 2 scan0213 | |
| Supply of car heater switches, citing difficulties with coachbuilders and deciding to purchase from an external supplier. | 9th Nov 1938 | Box 137 \ 2 scan0214 | |
| Letter from The Power Plant Co. Ltd. proposing their licensed Chevroc-McAleer Car Heater and Defroster. | 9th Nov 1938 | Box 137 \ 2 scan0215 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. regarding a delay with a noisy heater. | 11th Nov 1938 | Box 137 \ 2 scan0216 | |
| Official order be sent to S.Smith & Sons Ltd. for a car heater motor, fan, and fan volute casing. | 11th Nov 1938 | Box 137 \ 2 scan0217 | |
| Letter to S.Smith & Sons Ltd. regarding the testing and return of sample heaters, and placing an order for components. | 11th Nov 1938 | Box 137 \ 2 scan0218 | |
| Letter to The Goodyear Tyre & Rubber Co. regarding the sourcing of a suitable hose. | 11th Nov 1938 | Box 137 \ 2 scan0219 | |
| Letter to Dunlop Rubber Co. Ltd. regarding samples and pricing for flexible dust extractor hose. | 11th Nov 1938 | Box 137 \ 2 scan0220 | |
| Letter to Dunlop Rubber Co. Ltd. requesting a sample fan belt. | 11th Nov 1938 | Box 137 \ 2 scan0221 | |
| Car heater switches, comparing the inferior Clayton switch to the Lucas product. | 12th Nov 1938 | Box 137 \ 2 scan0222 | |
| Request to fit a tested sliding grille control for a heating system onto a different car model. | 12th Nov 1938 | Box 137 \ 2 scan0223 | |
| Letter to The Power Plant Co. Ltd. requesting drawings and costs for a Chevroc Heater and Defroster. | 12th Nov 1938 | Box 137 \ 2 scan0224 | |
| Replacement of two nuts for a Bentley 50 car heater because the original parts are unnecessarily thick. | 14th Nov 1938 | Box 137 \ 2 scan0225 | |
| Replacement of a nut on a Bentley car heater. | 14th Nov 1938 | Box 137 \ 2 scan0226 | |
| Letter from Dunlop Rubber Co. Ltd. acknowledging receipt of a letter and confirming a sample has been dispatched for the Experimental Department. | 14th Nov 1938 | Box 137 \ 2 scan0227 | |
| Letter from S. Smith & Sons regarding outstanding loan notes for car heaters, a demister, and a defroster blower unit. | 16th Nov 1938 | Box 137 \ 2 scan0228 | |
| Letter from Dunlop Rubber Co. Ltd. regarding the supply and specification of various hoses. | 17th Nov 1938 | Box 137 \ 2 scan0229 | |
| Replacement of Clayton car heater switches with alternatives from Lucas or a custom-built solution. | 18th Nov 1938 | Box 137 \ 2 scan0230 | |
| Letter from The Power Plant Co. Ltd. regarding a quote for heaters. | 18th Nov 1938 | Box 137 \ 2 scan0231 | |
| High cost of fittings for installing a Clayton Heater on a Wraith Chassis. | 18th Nov 1938 | Box 137 \ 2 scan0232 | |
| The return of two loaned car heaters to Messrs. S. Smith & Sons Ltd. | 21th Nov 1938 | Box 137 \ 2 scan0233 | |
| Letter to AC-Sphinx Sparking Plug Co. Ltd. concerning heater installations and orders. | 22th Nov 1938 | Box 137 \ 2 scan0234 | |
| Letter from S. Smith & Sons regarding a sample heater and the return of certain HaDees Heaters. | 22th Nov 1938 | Box 137 \ 2 scan0235 | |
| Defects with the small Clayton heater switch on experimental cars and proposing a solution. | 23th Nov 1938 | Box 137 \ 2 scan0236 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding a noisy heater unit motor and its dispatch. | 24th Nov 1938 | Box 137 \ 2 scan0237 | |
| Modifications to the dash and windscreen for a new AC car heater. | 25th Nov 1938 | Box 137 \ 2 scan0238 | |
| Instructing the fitting of a Smith's HaDees car heater to car 1.B.50. | 26th Nov 1938 | Box 137 \ 2 scan0239 | |
| Instruction regarding the fitting of a car heater, ensuring the chassis is sent to coachbuilders first and space is left for the heater. | 28th Nov 1938 | Box 137 \ 2 scan0240 | |
| Request to design a flexible moulded rubber hose connection for a car heater fan drive. | 29th Nov 1938 | Box 137 \ 2 scan0241 | |
| Letter from S. Smith & Sons (Motor Accessories) Ltd confirming a quote for 500 Smith Heaters. | 29th Nov 1938 | Box 137 \ 2 scan0242 | |
| The supply of Lucas Car Heater Switches. | 29th Nov 1938 | Box 137 \ 2 scan0243 | |
| Letter from S. Smith & Sons confirming the weight of a front die casting for a HaDees Heater. | 29th Nov 1938 | Box 137 \ 2 scan0244 | |
| Letter from S. Smith & Sons regarding the price of a Car Heater left for testing purposes. | 29th Nov 1938 | Box 137 \ 2 scan0245 | |
| Official order for a car heater from S.Smith & Sons Ltd. | 30th Nov 1938 | Box 137 \ 2 scan0246 | |
| Request to see a sample of a Lucas car heater switch before placing a quantity order. | 30th Nov 1938 | Box 137 \ 2 scan0247 | |
| Letter from The Power Plant Co. Ltd. finalising designs for a combined heater and defroster unit. | 1st Dec 1938 | Box 137 \ 2 scan0248 | |
| Sample car heater switch being sent for examination. | 1st Dec 1938 | Box 137 \ 2 scan0249 | |
| Requesting a design scheme for a heating system for Wraith and B.50 chassis models. | 1st Dec 1938 | Box 137 \ 2 scan0250 | |
| Letter to The Power Plant Co. Ltd. confirming a meeting to demonstrate their designed air conditioning equipment. | 3rd Dec 1938 | Box 137 \ 2 scan0251 | |
| Price quotation from S. Smith & Sons for 500 Smith Heaters. | 5th Dec 1938 | Box 137 \ 2 scan0252 | |
| Continuation of a letter from S. Smith & Sons discussing making a more efficient and better-looking part. | 5th Dec 1938 | Box 137 \ 2 scan0253 | |
| Placing an order for 50 Lucas car heater switches with black knobs and front plates. | 6th Dec 1938 | Box 137 \ 2 scan0254 | |
| Requesting modifications to the defroster ducts and heater intake for car 1.B.50. | 7th Dec 1938 | Box 137 \ 2 scan0255 | |
| The pricing of Clayton Heater fittings for the Bentley 'M' Series, referencing manufacturing costs for the Wraith. | 8th Dec 1938 | Box 137 \ 2 scan0256 | |
| Letter to Metalastik Ltd. regarding the feasibility of vulcanising a rubber sleeve for a car heater drive. | 10th Dec 1938 | Box 137 \ 2 scan0257 | |
| Inquiry regarding the vulcanisation of a rubber sleeve to steel or brass adaptor pieces for a car heater drive. | 10th Dec 1938 | Box 137 \ 2 scan0258 | |
| Proposing a more economical scheme for fitting car heaters to Wraith, B.III, and B.50 chassis. | 12th Dec 1938 | Box 137 \ 2 scan0259 | |
| Instructions for fitting heater pipes and a list of attached prints. | 12th Dec 1938 | Box 137 \ 2 scan0260 | |
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