Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

All righty then kids .... back to this ongoing mechanical adventure, and sorry for the extended delay. Likely to be more of the same before this tale of woe is complete, but no hurry anyway as it isn't going anywhere under its own power anytime soon!

So last post I was inside the steam chest, and while I found the D-valve and port face to be fairly flat, albeit with somewhat rounded edges and corners, and not entirely smooth, I decided that I'd do a bit of lapping and also try to clean up and square the ports themselves which were a bit out of square with some wildly irregular edges. Turns out that took a fair amount of time as the casting inside the port channels was pretty rough, and even though I didn't do a true clean-up of all of that, I do believe the steam flow will now be somewhat enhanced and the cut-off should be a bit crisper as well, however I was unable to truly "square" the port edges, and they actually seem to slant slightly to the motion of the valve. Perhaps they are supposed to as a means of phasing the open and closing of the port? Probably not, and it is just another weird artifact of a poor build, though this one does seem to be cast in and nearly irremediable. Should run better now in any event!


[ Guests cannot view attachments ]

[ Guests cannot view attachments ]


There is also a noticeable casting flaw in both the D-valve and port face surfaces that would take really serious lapping, or even milling to get past, as would the rounded edges and corners on both faces. For now I'll not go that far,and likely never will, but it could be an option if it turns out to be necessary.

I should add that the other end of the valve linkage seems pretty okay just the way it is. The eccentric seems reasonably well made and fitted with shims that will allow for adjustment with wear. Although the linkage rod is "S" bent, and it likely wouldn't have to be if the eccentric cam had been put on the other way around, there really isn't any problem with it done this way, and I have now seen photos of at least a few others done this way as well.