45 degree trough angle idlers are capable of handling a higher capacity of product for a given belt width -- BUT -- the higher angle also requires longer transition lengths at all pulleys in order to prevent belt damage (longitudinal cracks at the trough junction points). This does not present a problem except at the discharge pulley, where it makes little sense to carry a greater amount of material on the carry run and then have it overflow the belt just prior to discharge. All belts, regardless of the idler troughing angle must be able to support the conveyed material while essentially flat (i.e. -- while going to the discharge pulley).
In my opinion, the real advantage of the higher angled troughing idlers is with their ability to contain material (less spillage potential) at the load point (allows some bounce room) and along the carry run (minimizes wind influence on the material and bounce effect of the idlers).
The disadvantages of the steeper idlers include the increased transition zones, increased chance for belt damage, and increased mistracking susceptibility (the wing idlers have a greater effect on tracking and the belt is affected by wind to a greater degree).
Like most conveyor components, steep trough idlers have their place and offer advantages when used judiciously. Any system should be designed with the needs of the end user in mind (even if the end user doesn't really know what those needs are) and it is incumbent on the system designer to offer the most economical system possible -- taking into account all costs, including maintenance and operational ones.
If you have specific systems to discuss, I would be willing to help as necessary (especially if I can get a trip to Australia out of it - you pay for time, my frequent flier mileage account pays for air travel).
10668 Newbury Ave., N.W.,
Uniontown, Ohio 44685 USA
Tel: 001 330 265 5881
FAX: 001 330 494 1704