Re: Pre-740 Engine Stuffing Box Chamber
Posted by:
Peter Brow (IP Logged)
Date: April 25, 2008 01:04AM
Hi Pat,
740-style "shaved piston" crossheads look very good, compensating for frame flex in a curious way, like a universal joint. I plan to try these with Babbitt lining for the semi-cylindrical crosshead slides, which in my engine design have much larger bearing area than an equivalent Stanley. 4140 "stressproof" frame rods are another good flex-handling feature. You probably know about Mike Clark's stressproof-alloy frame rods on his H5 engine; they look even better in person than in pictures, and combined with other features & details too numerous to mention, his very authentic car runs brilliantly. He also has a handy and foolproof system of compact drip-catching pans for wherever he parks, amazing that he found room on an H5 to stow them!
Straight wrist pins and modern bearings are good ideas, and I have heard nothing but good about properly-chromed rods and Monel rods. Personally I plan to lock the pistons to their rods, as rods screw into the crossheads with locknuts and can be removed at that end. For integral crossheads and other designs, I like your cotter pin setup.
My engine design, now extremely close to final blueprints and shop, isn't "exactly" a Stanley, except for general layout, dimensions, and steam parameters, but it follows the proven features of the Stanley design close enough that I think/hope it will give good results on the road. I have based it on the Herb Schick Model 740 Stanley blueprint set, though I have scaled it down to 4" stroke and have also made many changes for improved durability, use of off-the-shelf components and modern materials, and the simplest fabrication possible. Most of my design work the past year or so has been _removing_ various gizmos & features, lots of them, which I once thought would be desireable or needed. Getting really serious about _exactly_ how to build things -- and about what really works & doesn't work in steam cars -- has led to all sorts of changes relative to my initial plans.
The design is now greatly simplified. For one example, thanks to your report I just eliminated a long-planned device to remove water from the crankcase. "Ingenious but fortunately superfluous". Previously I had assumed that Stanleys (and any engines closely patterned after them) had the same crankcase-water trouble as Whites and Dobles.
Hi Caleb,
Can't say as I have considered genuine labyrinth seals for piston or valve rods. I have seen illustrations/descriptions of the Doble seals you mention, and as I recall(?), those were a sort of segmented external-contracting solid metal seal-block system. I looked into something like that some years ago. I will take another look at it. Does anyone reading this have any info about these kinds of rod-seal boxes? Were they ever used successfully in steam car engines?
Soft stuffing box packing looks easier to work with. Just cut rings and stack them in stuffing box with gaps 180° apart. Should give less wear on the rods than a solid metal seal, too. I have a reel of "Garlock 98" equivalent made by Palmetto Packings, a pure graphite rope packing, extremely high temperature/pressure ratings, soft, noncorrosive, and should "graphite-plate" rods. I plan to try this in my engine. I have heard good things about this type of packing in steam use. So far, I've only used it for repacking antique water valve stems in my house. Its temperature and pressure ratings are kind of overkill for that app.. LOL
BTW, you mentioned a multi-port short-travel slide valve idea long ago, which I just found info on. See pages 40-43 of "Valve Gears", available from Lindsay Books. It is called the McIntosh & Seymour "gridiron valve". Apparently successfully used sometime prior to 1906. The version illustrated has separate inlet & exhaust slide valves, at top & bottom of cylinder respectively.
Peter