Maintaining the Efficiency of Steam-wagon Brakes.
Page 27
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THE efficiency of any form of cam brake on steam wagons depends uPon the Movement of the cam in relation• to the face of the pad of each brake shoe. To be ideal, the brake should be designed to work with a cam always central and shoes with pads of equal thickness. However, many cam brakes on steam wagons are designed with the hinge and the cam pin housing formed on a part of the casting carrying the axle bearing-block, this being done for convenience and neatness. The result is that as the bearings begin to wear and drop, one brake shoe will drop with it, thus the perfect working of the cam will be altered, one shoe being brought into contact with the drum before the other, and resulting in inefficiency.
When this uneven working of the brake occurs, the shoes should be carefully examined, and packing inserted behind the pad of that shoe which doe not come into contact with the drum, Another cause of error in this type of cam brake is one which occurs very frequently, and results in much trouble, particularly as it is somewhat difficult to trace. It is shown in our illustration, the trouble being due to excessive tightening of the nuts on the bolts (AA), which hold the spring plate in position. These bolts are very strong, and if a fairly long spanner be employed, a tremendous leverage can be exerted with the result that the arms which carry the brake he hinge pin and cam spindle become displaced to as
great an extent as in. This displacement has the same effect as the wearing down of a bearing, viz., uneven expansion of the brake shoes. Therefore, when attending to a wagon, great care should be exercised not to tighten these bolts unduly.
We would draw the attention of users of steam wagons to our editorial comment on brakes in last week's issue.