I will never need to measure a drum. Put on your shoes and drive. No offence meant to Julian's kindness. I don't have the character to buy a mic to measure a drum to give to someone.
The "techniques" are brainstorming thoughts to illustrate that any home device that will expand, like a turnbuckle or modified turnbuckle, can be used to get a "set" of the inside diameter. Pull it out and measure the tip to tip of the DIY unit. If it's within a 1/16 of "not sure" then recycle the drum to scrap. I don't intend the suggestions to measure to .001 accuracy. This is all predicated on if you can find the spec for your drums.
Don't forget, one "technique" is take them to a "brakes are us" and ask the person to measure.
Tim, thanks for your suggestion on tips. It's nice you think they are worthy of that. If you were joking, I get that also because of the funkyness of the ideas. There is always something to pick out and message from a brainstorming exercise that ends up a good idea.
