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).
Calculation of climbing capabilities for the 40/50 HP and 20 HP engines.
| Identifier | WestWitteringFiles\K\June1923\ Scan82 | |
| Date | 16th April 1923 | |
| CLIMBING CAPABILITIES - 40/50 HP. & 20 HP. Let d = dia. of cyl. (ins.) " S = stroke (ins.) " ηP = mean effective pressure (lbs. per sq. in.) " T = torque (ins.lbs.) Then in a 6-cyl. 4 cycle engine, work done per revolution:- ( (π d² / 4) ηP S ) 3 ins.lbs. Also T X 2π = Work done per rev. T X 2π = ( (π d² / 4) ηP S ) 3 T = ( (d² / 8) ηP S ) 3 lbs.ins. Taking the M.E.P's at the road wheels (Figs. 16th. Apr. /23) to allow for transmission losses, and substituting the following figs. in the formula we get :- 40/50 HP. 20 HP. d = 4½" d = 3" S = 4½" S = 4½" ηP = 69 lbs. per sq. in. ηP = 76 lbs. per sq. in. Max. engine torque allowing for transmission and rear tyre losses :- 40/50 HP. 20 HP. 2488 lbs.ins. 1154.2 lbs.ins. Let R be gear ratio. " D be effective tyre dia. (ins.) " W be weight of car in tons. The tractive effort in lbs. per ton at the tyre :- (R T / (D/2 W)) or (2 R T / W D) Substituting following values :- 40/50 HP. 20 HP. W = 2.75 tons. W = 1.95 D = 33". D = 31.4" T = 2488"lbs. T = 1154.2 ins.lbs. contd:- | ||