What is the difference between the 4 fin and 5 fin draft caps on the Fisher Stoves and the time frame they changed them?
Fisher Stove Draft Fins
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Baxter Fisher invented the EZ-SPIN trademarked draft cap for his son Bobby's stoves. (Patent is on first page of Everything Fisher thread) The challenge was making a cooler cap than the original pipe cap on the first stoves. Bob insisted he patent it himself to take advantage of royalties and sell to other manufacturers as well. They were marketed by his brother Don and father Baxter. They sold originally for $4.50 per set to their stove fabricators, even after Bob told them they would be too much. A fabricator in Utah started making their own, and the price was reduced. The 4 fin was redesigned a few times, and continued to use the same patent number. (even after changing to 5 fins) The side profile of the fins was changed from a more square fin to rounded, and they were shortened to not protude out as far in the center. (there are a few oddities before the patent number was applied for, such as smaller diameter and no rim on the back, so the fins stick out farther than the round diameter. I have one set like that with no EZ-SPIN marking, presumably before they were trademark named)
Later the 5 fin was made available to fabricators. This was shortly after the first year (1976) of the double door stoves, since all '76 doors seem to have 4 fin. You can't pin point a time, since fabricators were using the old stock as they were building stoves, until they ran out and started using the new. The 5 fin Varieties include; With or without center steel threaded insert / nut. A Canadian patent was added in 1978 along with the US # on back, polished alum. edges or brushed alum. edge, aluminum plated with brass, or cast of solid brass instead of the common aluminum. Part numbers of the 5 fin are 237-288 with pattern number 1 through 4. Many are stamped with a large capital H that I'm unsure of it's meaning, and MIP 2 also appear on many.
Later the 5 fin was made available to fabricators. This was shortly after the first year (1976) of the double door stoves, since all '76 doors seem to have 4 fin. You can't pin point a time, since fabricators were using the old stock as they were building stoves, until they ran out and started using the new. The 5 fin Varieties include; With or without center steel threaded insert / nut. A Canadian patent was added in 1978 along with the US # on back, polished alum. edges or brushed alum. edge, aluminum plated with brass, or cast of solid brass instead of the common aluminum. Part numbers of the 5 fin are 237-288 with pattern number 1 through 4. Many are stamped with a large capital H that I'm unsure of it's meaning, and MIP 2 also appear on many.
Thanks Coaly for the info.The reason I asked is because my Dad bought a Mama Bear that has the 4 fin draft caps to heat his old farm house with this past winter. Amazed with the heat it put out too, would run you out of the house. After looking through your many post there was one that had mentioned the 4 fin caps. So I figured I would ask about them. Thanks
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