Topic starter
01/02/2007 2:47 pm
Looking at the side view of the engine, it appears that the cylinder is supported on six tabs, three per side that rest in a saddle on the timbers. It looks as though the cylinder "floats" in those saddles and is not bolted to the timbers. Is this what is actually there or am I misinterperting what I see? (My vision is more than a little "impaired".) Seems like the stresses on the cylinder could cause it to jump out of the saddles if it were loaded heavily of if the wheel hit something solid. Also, is the valve wheel visible about the center of the cylinder the throttle for this engine? Pardon my ignorance, but the only way I know to learn is to ask.
01/02/2007 8:37 pm
Hank, I've not studied the Arabia's cylinders in great detail, but the usual way was to bolt all of the supports to the cylinder timber. The supports were slotted to allow some expansion and contraction of the cylinder. One pair of the supports was throughly blocked and wedged to prevent fore-and-aft movement of the whole engine. The system was weak and subject to wear so provision was made to take up the 'slack' from time to time. Captain Jim Howard once told me that he had seen cylinders move as much as two inches at every stroke! on wood-hulled boats!
The valve wheel is the throttle. The Arabia was a sidewheeler, so each engine had its own throttle valve.
01/02/2007 8:46 pm
There is a side view of the cylinder in the link about the Arabia's engine. The center set of supports rests in a channel-shaped casting. Wedges could be driven in front and back to adjust the location of the cylinder and to hold it there. The end supports were merely bolted down as I described earlier.
Topic starter
01/02/2007 9:44 pm
Thanky. Now that I look closely, I think that I can see the bolt through one mounting tab. I suppose that the gaps between the sides of the center tab and the support saddle/channel is where the wedges would have been driven.
Would have been kinda hazardous to use the throttle with that kind of setup, wouldn't it. (Of course safety wasn't a concern at the time....)
02/02/2007 12:35 pm
You can see the identical set-up on the Belle of Louisville today. More than likely the other steamboats still in operation have a similar arrangement. The wedges could be used for making certain the longitudinal center of the cylinder is the exact distance it is supposed to be from the shaft centerline. The shaft pillow blocks have a similar wedge-in-channel system. The wedges are bolted into position to hold them where driven. The bearings in the pitmans also are adjusted and held by wedges. What would you use in lieu of wedges?