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).
Sub-frame performance, detailing how road surface imperfections cause frame deflection and dash movement.
| Identifier | ExFiles\Box 41\3\ Scan443 | |
| Date | 15th December 1924 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. -2- EXPERIMENTAL REPORT. Expl. No. REF:HS{Lord Ernest Hives - Chair}/TMW/LG15.12.24. sets and at low speed full throttle. The general impression, however, of comfort, tranquility, and sweet running which one retains, is perhaps the best testimony to the excellence of the sub-frame principle from a riding point of view, while the advantage to the Coachbuilders, in being able to build the body on the sub-frame previous to the chassis being received, is obvious. The above tests were carried out with the scuttle entirely isolated from the dash, and considerable sideways movement was noticeable at this point when sub-frame was insulated. Investigations shewed that the scuttle remained rigid with the body and that there was a negligible amount of movement on the rubber pads, not above .002". From this point forward the main frame developed lateral movement, taking the dash with it. What appears to be going on is that the uneven road surfaces deflect the main frame at the front, in either direction, as far back as the front sub-frame suspension. Here, by reason of the main frame cross member, the sub-frame bracket and sub-frame cross member all being concentrated, added to which is the whole weight of the forward portion of the body, the most rigid point of the main frame is found. The front road springs, not being definitely controlled sideways, allow the frame to deflect and twist as far back as this point, thus causing the sidways movement of the dash referred to; the amount of this being proportionate to the blow received by either front wheel. Itis also noticeable that, if either of the rear wheels is raised from the ground contd :- | ||