cylinder angle

Hello folks me again with another odd question, first off I don't like to be a bother but I tend to do a search in the forum to see if there are any prior posts but I might be getting the question wrong as nothing ever shows up most times anyway don't shout at me if this question has been asked before.

I was studying some loco drawings and looking at old photos and the angle of the cylinders on loco's like the "crab", Big Bertha and the 9f had quite a rake on them would I be right in thinking this gave better tractive and adhesion qualities as the power is more downward to the track but the pay of fwas power to the hammer blow on the rails.. reason for the question would changing the rake on lets say a robroy give it more grunt. and what would be the problems with the geometry.

Normally its to line up the longitudinal centerline of the cylinder with the driving axle center at mid suspension travel, to ensure that the power delivered is even on both strokes and in forward and reverse.

Of course the shorter the frame length the more steep the angle wil be.

hi martin,

usually an inclined set of outside cylinders is inclined for clearance reasons. inside cylinders are usually inclined to avoid interference with the front coupled axle.

in forward the outward stroke has an effect on pushing the wheel down if the cylinder is steeply inclined, but on the inward stroke the opposite is the case which is not a good thing at all. have a look at the way Rocket was modified soon after building to reduce the inclination!

cheers,

julian

Certainly in the case of the 'Crabs' the inclination of the cylinders was purely to avoid clearance problems with lineside objects such as platform edges. They had a relatively low pressure boiler (180psi) and had large diameter cylinders to compensate for this.

John