LITERATURE REVIEW
From ITDG (1976) no useful facts emerged.
From Bryce (1967), the strength, durability, density and impregnation properties of several African timbers were obtained. These are presented in Table I. For bearings and slides, Bryce states that hardness and even wear are the main requirements, and that oily texture is an advantage. He recommends the use of East African afrormosia, African Blackwood, Msaraka and Brown Olive.
Booser (1961) recommends operating limits for wooden bearings. They are presented in Table II.
Atkinson (1972) states that hardness and natural oiliness are important characteristics of timber for use as bearing material.
Coombs and Pearson (1974), working with oxcatrs carrying loads up to 2 tonnes, found that for a 38mm diameter steel shaft, a radial clearance of 1 mm was essential. If these impregnated bearings are carefully run-in at slow speeds (ox work) then the clearance increases to 1.5 - 2 mm and the bearing surface attains a highly polished appearance. After reaching this condition, the bearings are able to withstand higher speeds (Land Rover towing). They found that wear during the running-in periood is rapid, after which wear rate reduced to a constant value with time. They found that wear was approximately proportional to load, but increased rapidly for small increments in speed.