From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of roof specifications for Saloon and Limousine Goshawk-11 models.
| Identifier | WestWitteringFiles\K\June1923\ Scan65 | |
| Date | 12th June 1923 guessed | |
| DETAILS OF BODY CAR ROOFS. Details. | (Saloon) 7-Goshawk-11. | (Limousine) 3-Goshawk-11. Average height above frame of roof between windscreen and front and rear step iron. | 4 ft. 5 15/16" | 4 ft. 5¼" Width at rear of front seats. | 4 ft. 6½" | 4ft. 3½" Area of roofing. | 4880 sq. in. approx. | 5377 sq. in. approx. Thickness of roof. | 5/16" approx. | ⅜" approx. Weight of roofs (Wt. of 1 cu. in. of material taken as .02" lbs.) | 30½ lbs. approx. | 40 lbs. approx. Details of roof stiffening. Wt. 1 cu. in oak .027 lbs. Wt. 1 " " steel .27 lbs. | Steel 55.5 cu. ins. = 14.9 lbs. Oak 1017.75 cu. ins. = 27.48 lbs. | Steel (?) Oak 938 cu. ins. = 25.3 lbs. Details of top framework of body (1 cu. in. taken as .027 lbs.) | 1270 cu. ins. = 34.3 lbs. | 1270 cu. ins. = 32.7 lbs. [Drawing of roof framework perimeter with text: TOP OF FRAMEWORK AS TAKEN] Total wt. of roof without steel stiffening. | 92.3 lbs. approx. | 98 lbs. approx. Wt. of steel angle iron. | 14.9 lbs. | (?) Wt. of aluminium drip moulding (.18 lbs. per ft.) | 3 lbs. | ------ Total weight of roof. | 110.2 lbs. | 98 lbs. | ||