Even a number of kit manufacturers use 3" and 4" diam. PVC pipe for the silos.You can buy it at Lowes Home Depot and plumbing supply houses. Then using 16 ply artists illustration board and 1/4" sq basswood stock, fabricate a top piece, roof , add a grain elevator along side and a few Grandt Line or Korber windows and then paint/detail. Want to see what one looks like; do a search for Korber Models and take a look. If you don't want the work of scratchbuilding you might want to consider buying the Korber kit.
Marty has done the samething, I think his are 12" by about 4' tall.
I built several tanks out of PVC and plan on making some more larger ones this winter. This is not prototypical of anything particular.
Mark
M. Gilger - President and Chief Engineer MM&G web
Web Site: http://mmg-garden-rr.webs.com/
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