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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).
Letter from Vacuum Oil Company providing seizing temperature figures for various grades of Mobiloil.

Identifier  ExFiles\Box 145\1\  scan0195
Date  20th April 1938
  
12297
Mths.{Reg Matthews}
Please note & return
Pm
BY APPOINTMENT
VACUUM OIL COMPANY LIMITED
TELEPHONE
WHITEHALL 1010 (14 LINES)
GARGOYLE
TELEGRAMS
VACUUM · PHONE · LONDON
CAXTON HOUSE · WESTMINSTER
LONDON
S·W·1
REFERENCE
OTJ.
20th April 1938.

Messrs Rolls Royce Ltd.,
DERBY.

Dear Sirs,

For the attention of Mr. W. A.{Mr Adams} Robotham.

With reference to the interview on Tuesday last, we have pleasure in giving you hereunder the National Physical Laboratory seizing temperature figures for the various grades of Clearosol Mobiloil.

Mobiloil Arctic . . . . . . . . . . 152°C Maximum
" "A" . . . . . . . . . . 196°C "
" "BB" . . . . . . . . . . 265°C "
" "D" . . . . . . . . . . 254°C "

It will be apparent from the above that the tests as carried out by the National Physical Laboratory do show that the heavier oils have a wider margin of safety, but it is important to remember that these bearing tests are carried out with a uni-directional continuous loading of 1,000 lbs per square inch at a speed of 1300 r.p.m., consequently the seizing temperatures arrived at are not directly comparable with Motor Car practice where the loads are alternating and, therefore, much less severe from a seizure standpoint. The above-mentioned figures were obtained during a 50-hour Jakeman test on the National Physical Laboratory Bearing Testing Machine, using a bronze bush on a two-inch diameter steel shaft.

Also the seizure referred to is not a mechanical seizure in the generally-accepted sense, but an oil seizure presumably indicating boundary lubrication conditions. This figure is determined by an increase in the coefficient of friction, and can be repeated indefinitely on the same shaft and bush, without mechanical damage to the bearing.

Yours faithfully,
VACUUM OIL COMPANY LIMITED.

Chief Engineer.

UNLESS STATED OTHERWISE ALL OILS ARE QUOTED AND INVOICED PER UNIT GALLON OF 9 LBS. AND ALL QUOTATIONS ARE WITHOUT ENGAGEMENT.
  
  


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