Message text written by "John Carmichael" >How many degrees should I incline the dial? Is there some set standard that builders use for things like sidewalk drainage?<
In Britain, the gradient usually quoted as being the minimum required for draining a pavement (What you call sidewalk <g>) is 1 in 40, which is easy to remember and to set up if you are prepared to mix your units since it's (just about) equal to 1 inch in a metre!. With some surfaces in Britain we typically work to minimum gradients of 1 in 80 (one inch per 2 metres) with no problems as some surfaces drain more efficiently than others. We find that block or brick paving usually drains well at shallower gradients (up to 1:80), assisted by the chamfers on the top edges of the blocks/bricks. Tarmac is notorious for holding water or 'ponding', due to small deviations in surface level resulting from the inaccuracies inherent in hand-laying tarmac. This type of surfacing is best laid to a steeper gradient such as 1 in 40. Some persons recommend steeper gradients - especially for pipes - and up to 1 in 10 is mentioned for those but you shouldn't have to get any steeper than that. Be careful that they don't ask you to cone the surface of the dial or also to provide a cross fall (that is drainage in all or two directions). The delineation suffers. For big dials I usually insist on a flat chapter ring with drainage provided inside and outside the ring. That way the drainage and the delineation are correct, the dial looks better when the time ring is flat, it's easier to calculate but much, much more importantly it's easier to lay out and to do cross-check measurements as the dial is being laid. Hope this helps Patrick -
