TflE KOYAt ARTILLERY INSTITUTION. 
123 
EXPERIMENTS ON FRICTION. 
BY 
COLONEL H. CLERK, R.A., E.R.S. 
Since the introduction of heavy rifled guns into the service, it has become 
necessary to use powerful compressors to check their recoil. 
The following experiments were instituted with a view of ascertaining the 
best materials of which to make the compressor, and the best mode of 
applying that material so as to obtain the greatest amount of resistance to 
the recoil, combined with the least strain upon the carriage or platform. 
These experiments were made under the direction of Mr Butter, chief 
draughtsman of the Royal Carriage Department; and I now forward his 
account of them for the information of the members of the Royal Artillery 
Institution.* 
They consist of five series :— 
(a) To ascertain the effect of varyiilg the amount of surface. 
(b) To ascertain the effect of varying the amount of pressure. 
(c) To ascertain the effect of varying the number of surfaces. 
(d) To compare statical and dynamical friction. 
(e) To obtain coefficients under the same conditions of rate of motion,” 
and “ wear.” 
In each series various materials were used, such as hard and soft woods. 
Iron, and gun-metal, in different combinations, viz. wood and wood together, 
wood with metals, and metals with metals. 
The various experiments on friction, as hitherto carried out by Rennief 
and others, have been mostly with the view of ascertaining the amount of 
resistance offered by various machines, &c., to the transmission of force, and 
have dealt almost exclusively with statical friction, or the resistance offered 
* These experiments were commenced in Oct. 1865, but the pressure of other business has 
delayed their completion till the present time, 
t Vide Phil. Trans. 1829, Eennie “ On Friction 4 ” 
[VOL, VI.] 
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