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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).
The testing of Ferodo Ferogrip fan belts, models No.1 and No.2.

Identifier  ExFiles\Box 135\1\  scan0242
Date  8th November 1938 guessed
  
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FERODO FEROGRIP (NO.1)

This test was interrupted at various times due to trouble with the flat driving belt. It was found impossible to keep the flat belt slip down to a figure which gave the required fan speed. The fitting of a laminated leather belt did not improve matters so a jockey pulley was fitted using the original rubber driving belt. This finally removed the flat belt troubles and the test was continued until after 4 hours testing the fan was returned to Rolls Royce with the blades badly fractured. The replacement fan having been fitted the test was continued till a total of 5 hours 10 minutes running had been attained. At this point the vee belt turned over in the pulleys and the test was stopped. It will be noticed from the curve that the HP absorption of this fan was rather higher than that of the previous one. The motor speed was therefore slightly reduced to bring it more in line.

FERODO FEROGRIP (No.2)

During the first 30 minutes of the test the vee belt centres were increased from 13-1/4" to 13-9/16" and these were the only increases made for 17 hours 47 minutes. After 4 hours some slight trouble was experienced due to the flat belt slipping sideways against the flange of the intermediate shaft pulley. In the main this was without doubt due to the temporary jockey pulley rig which had been fitted, so the opportunity was taken to redesign and make an improved jockey pulley. Occasional adjustments were necessary to the flat belt but these were made without stopping the test and after 17 hours 47 minutes the test was stopped and the vee belt adjusted. This did not have the desired effect, that was, to reduce the slip to within the specified 4% so the test was continued at these centres. The vee belt slip in this latter period was of the order of 4.5%

After 20 hours a fracture was noticed in one of the fan blades and after 22 hours 57 minutes one fan blade sheared off through the top rivet of the spider. During the interval between the fan burst and the return of the replacement fan the vee belt was removed from the test for inspection.

On fitting the new fan and replacing the vee belt at the original centres it was noticed that the belt was slack, so the vee centres were increased by 1/16". This had the effect of reducing the slip to about 3% average. After 23 hours 30 minutes total running time, that is, 31 minutes after the new fan had been fitted the vee belt commenced to judder. This had no effect on the slip but 7 minutes after the judder was noticed, the belt turned over and left the pulleys; the total running time being 23 hours 37 minutes. For 75% of this time the test ran continuously during the mornings and afternoons, the only stops other than the centre adjustment at 17 hrs. 47 mins. being those of meal-times and stoppage throughout the night.

The belt after test shows a deformed section and in addition the cover joints are lifting slightly. One side of the joint is torn back for about 1/4"; the side walls are showing slight signs of wear but are not frayed or broken in any place other than at the joint.

Summarising the reasons for the stopping of these tests:-

Gates Vulco - cords broke after 11 hrs. 45 mins.
Dayton Cog - excessive stretch and slip 6 hrs. 45 mins.
Ferodo Ferogrip No.1 - cord broke after 5 " 10 "
" " No.2 - " " " 23 " 37 "

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