Popular Science Monthly 



will generally be distributed somewhat. 

 If the heavy marks which usually appear 

 at first are simply removed by light 

 scraping, these "point bearings" are gen- 

 erally enlarged, but a much longer time 

 will be required to distribute them. 



The number of times the bearing must 

 be applied to the journal for testing is 

 important, especially when the box or 

 bearing is large and not easily handled. 

 The time required to distribute the bear- 

 ing marks evenly depends largely upon 

 one's judgment in "reading" these marks. 

 In the early stages of the scraping op- 

 eration, the marks should be used paiitly 

 as a guide for showing the high areas, 

 and instead of merely scraping the 

 marked spot the surface stirrounding it 

 should also be reduced, unless it is evi- 

 dent that the unevenness is local. The 

 idea should be to obtain first a few large 

 but generally distributed marks ; then an 

 evenly and finely spotted surface can be 

 produced quite easily. 



In fitting brasses when these are of 

 the removable t\'pe, two methods may be 

 used. The upper half of the engine base 

 may be inverted on a suitable bench or 

 stand and the boxes fitted by placing the 

 crankshaft in position, clamping down 

 one bearing cap at a time and fitting each 

 bearing in succession until they bed 

 equally. From that time on the bear- 

 ings should be fitted at the same time 

 so the shaft will be parallel with the bot- 

 tom of the cylinders. Considerable 

 time and handling of the heavy crank- 

 shaft may be saved if a preliminary fit- 

 ting of the bearing brasses is made by 

 clamping them together with a carpen- 

 ter's wood clamp and leaving the crank- 

 shaft attached to the bench. The 

 brasses are revolved around the crank- 

 shaft journal and are scraped to fit wher- 

 ever high spots are indicated until they 

 assume a finished appearance. The final 

 scraping should be carried on with all 

 bearings in place and revolving the crank- 

 shaft to determine the area of the seat- 

 ing. When the brasses are properly fit- 

 ted they will not! only show a full Ijear- 

 ing surface but the shaft will not turn 

 unduly hard if revolved with the same 

 amount of leverage as afforded by the 

 flywheel rim or starting crank, bearing 

 caps being bedded down and lubricated. 



137 



A 



Liners Vi^Jl d:^: 



B 



HingedJype 

 Hinge 



Retdining Bolts 



Fig, i6. Outlining common types 

 of connecting rod big ends 



Bearings of white metal or babbitt 

 can be fitted tighter than those of bronze 

 and care must be observed in supplying 

 lubricant as considerably more than the 

 usual amount is needed until the bear- 

 ings are run in by several hundred miles 

 of road work. Before the scraping 

 process is started it is well to chisel an 

 oil groove in the bearing as these 

 grooves are very helpful in insuring uni- 

 form distribution of oil over the entire 

 width of bearing and at the same time 

 act as reservoirs to retain a supply of 

 oil. The tool used is a round nosed 

 chisel, the effort being made to cut the 

 grooves of uniform depth and having 

 smooth sides. Care should be taken not 

 to cut the grooves too deeply as this will 

 seriously reduce the strength of the 

 bearing bushing. 



Rcmctalliiig and Fitting the 

 Connecting Rods 



Fitting and adjusting the rod bear- 

 ings, especially those at the crank pin 

 end, is one of the operations that must 

 be performed several times a season if a 

 car is used to any extent. There are 

 two forms of connecting rods in general 

 use, known respectively as the marine 

 type, shown at Fig. i6, A, and the 

 hinged form depicted at Fig. i6, B. 

 The hinge type is the simplest, but one 

 clamp bolt being used to keep the parts 

 together as the cap is hinged to the rod 



