Tungsten would be better. But then you would need a much better motor with a lot of torque to get it rolling. Here is an update, I tested 74 F units had 66 good and 8 bad. So far that was all the locomotives that were awaiting decoders in the F series. Of the 8, 6 were my favorite DRGW scheme, 2 F7's and 4 B Units and a pair of NP B units. That takes care of all the DC locomotives awaiting decoders. Next up is pulling the remaining decodered units and testing them. The box is getting heavier with all the bad locomotives. In the end, it might be cheaper to put them all in the car and drive them to Longmont CO.
This latest talk about the Zink pest is beginning to make me wonder about my IM F units? I haven't had them out in awhile, guess I need to pull them out and check'em.
At a melting point of 6190 degrees Fahrenheit, casting becomes a problem. (Zamac compositions, by comparison, melt at 410-420 degrees F.). Casting probably isn’t really viable at all, certainly not for hobby-grade suppliers. Maybe a sintering process. It would be much harder to machine as well. Frames would have to be sintered/molded a lot closer to final dimensions. Folks who do home-brew DCC/sound installations that include frame cutting to make space (including the KOBO guy), and more general kitbashers, will have some adapting to do. All this would have an impact on pricing, as well.
Platinum and gold are almost as dense as tungsten or depleted uranium and much easier to work with. "Darling, what happened to all my jewelry?"
It sounds like the units with the decoders have had the issue much more frequently than the units without decoders. Is it possible that the decoder could play any role? I'm not suggesting that you did anything wrong/incorrect, just curious as to the possible reasons the DC units seem to be in better shape (although losing even the 8 of those is bad enough).
Hopefully Intermountain is a stand-up company, we in Z scale had the same situation with some early GP38's. The company recognized the problem, and for just shipping costs, replaced the whole chassis minus shell for free. They made sure the material was far better from then on! Hopefully they will do the same for you owners.
Having dealt with IM on this exact issue with a couple of SD40T-2, the company did 100% customer service, sent me replacement frames. Now it being how many years since these were produced, not sure how many extra frames they would still have. Maybe if they get their new products in (updated SD40T-2s & F7s with sound) maybe they will have spare frames from them. Of course these newer frames would be even lighter with having room for the speaker.
I don't know about the F units, but with the SDs the frame has changed enough that it requires a different decoder.
Tungsten was a bit of tongue in cheek silly humor. Perhaps a better choice might be stainless steel or some other metal. With most of the frames changed now for decoder boards and some even ready for sound, it seems there is very little modifications that need to be done for decoder installs now.
I heard back from Intermountain, basically they will do nothing about the problem other than to charge me for replacement parts. So it become essentially buying the locomotive twice. Not a chance of that happening. Not a single penny more to Intermountain for me. So into the the local dump go all these defective locomotives.
If you can salvage the shells, trucks and internal electrics I'd at least keeps those or sell them. That is not good customer service especially to a prolific IM collector such as yourself. I would have expected they at least offer to make you whole on a portion of the affected locos. Perhaps you could get all the frames in a box and before you toss them snap a pic and post it up. A pic is worth a thousand words as they say and this would put an exclamation point on their lack of customer service.
Aluminum or Brass, I would think. Both are machinable, and the right alloys will remain bright and dimensionally stable. Brass has a lot of history in model locomotives. Material cost and higher melting points for either mean more expensive castings.
I've found the same results with electric bikes. The warranty doesn't exist if THEY don't check it out. So you ship it to them and back to you at YOUR expense. Usually unfixed. The local mechanics won't touch it without there total assistance.