View single post by Salada
 Posted: Thu Jun 18th, 2015 09:22 pm
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Joined: Mon Nov 4th, 2013
Posts: 1190
Herb is correct.

The drive pulleys are "crowned", meaning they are slightly convex though normally this is hardly noticeable unless a straight edge is placed across the driving surface. Flat belts will always run "uphill" if they can, hence the crown keeps the belt running true but the Driver & Driven shafts must be parallel & in the same horizontal/vertical  plane - if not the belt will rapidly climb up a misaligned pulley. On long drives belts are sometimes "crossed" into a figure of eight which can reduce drive slippage but need careful setting up to avoid the belt running 'edge to edge' and fraying where it crosses itself.

The "clutch" pulleys (or the Fast & Loose as it is known) are not crowned, as Herb says, because this would make it even more tricky to shift the belt across. The Driven pulley in a Fast & Loose arrangement is crowned, to maintain the correct centering of the belt. Setting the correct position & width of the 'jaws' of the forked belt guide is important in avoiding fraying the drive belt edges.

Regards,          Michael

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