Message Number: 14 From: "VR Bass" <[EMAIL PROTECTED]> Subject: Re: Wheels >Harry, you mention a lot of hand work. If I understand it correctly, the EDM >method creates spokes without a draft angle Vance, Yes, in most cases, but one could certainly use a tapered electrode . . . The advantage to using EDM would primarily be to get the spoke geometry, profile, and spacing dead-on and produce corners that only hawk's sight and a dental drill could do otherwise. The hand work would come in when you begin to work the rim, spokes, and hub to final shape and couldn't be avoided. Even if one used a tapered electrode that would result only in draft. Profiling and rounding off would continue as usual, at least to the extent it was required. >This is not necessarily a bad thing in all cases -- True, some locomotive wheels (although mostly UK) did have rectangular spoke profiles. >They'll be fine for outside-frame locomotives, where you don't really see >the wheel except in silhouette. Yes, but then there goes the Mark Wood approach to wheels out the window doesn't it. This partly explains why we don't have such products here. (That and a lesser per capita ratio of compulsive behavior amongst the male population :-) >when you work with a caster, be sure to talk about the necessity for >concentricity, I understand for some (many?) there is a benefit from wheels that need a minimum, if not no, machining, but in the model engineering and real worlds this would be the exception rather than the rule. When either making a pattern or buying a casting I always assume I'll machine its critical surfaces. >I think the lack of a raw material source was what was holding up the >foundry I work with. Knowing that there are sources of gray iron bar >means that we could get iron castings without worrying about what's in that >Ford engine block. Once upon a time, and maybe still, you couldn't do better than an old engine block as you could be sure these were done in new iron. Then the usual source for aluminum for a lot of home foundries has always been busted up pistons. Admittedly most foundries doing structural or appearance grade casting in any metal always prefer to use fresh metals for quality control. (By the way there are companies that do nothing but supply pure metal in ingots for foundries.) The ones that make "trash" castings, dead weights, drain grates, manhole covers, and such don't much care, but in any case it's the foundryman who needs to know what he's doing. Even new metal needs admixtures, flux, degassifiers and the like, and careful control of pouring temperature. As you've seen from recent posts the moulding processes (molds, forms, risers, sprues, etc) are critical, especially where the sections are small, and ours are tiny. In the grand scheme of things the metal source seems almost secondary. Cheers, Harry