New belts of heavy construction, e.g. considerable thickness in proportion to width, will not trough so well to start with; when empty, such belts may rest almost entirely on the inclined rollers and bear very little on the centre horizontal roller. It is this horizontal roller which does the training or centering. The inclined rollers tend to pull the belt out of centre. For this reason, therefore, when a new belt is started and some difficulties are experienced in training this new belt when empty, it will be best to train the belt just sufficiently so that running without damage to belt becomes practicable.
The belt should then be run under load for several days and gradually be trained until the belt runs true.
It will generally be found that a few days running under load will take out initial stretch and make the the belt trough easier.
This will cause better contact with the centre roller and help to keep the belt centred.