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A question regarding tube sizes...

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#1 gunner1



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Posted 13 February 2018 - 02:48 PM

So, I'm curious as to tube sizes - in particular inner diameters and outer diameters. I'm starting to get things together to start making "sugar rockets" and have it figured that I'll use 3/4" i.d. tubes with 1/8" walls for the engines. This creates a tube that is 1.00" in total o.d. Now, to attach headers I want to use tubes that are 1" i.d x 3" (or 4") long. My question is this: will the header still fit over the engine tubes? It seems to me that they'd be the same size. Or am I over thinking it?

#2 Arthur



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Posted 13 February 2018 - 05:31 PM

As paper tubes, an engineering fit is unlikely and both tubes will change size and shape with extremes of humidity. If the bore is specified then it's unusual for the OD to be specified also. However should there be a gap, it will be small enough to fill with white glue, if there is an interference fit then maybe some sand paper may ease things.

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#3 Bensmith



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Posted 20 February 2018 - 04:19 PM

I use 1" ID tube to fit over my 1lb tubes all the time for headers. Humidity and temperature fluctuations may make the fit a bit looser or snugger, but it works quite well. 1lb NEPT tube and 1" ID x 6" long tubes for the headers (available from www.cannonfuse.com) all work very well together.

#4 Seymour



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Posted 02 March 2018 - 10:31 PM

I tend to use a larger tube than 25mm ID for headers on 3/4" (19mm ) ID when making small headers, often 30mm ID cake tubes. These are great for very short end burners using one or two increments of fuel since they don't go too high.

I use strips of paper and tape wrapped around the top of the motor tube to bulk it out to the ID of the header casing tube.

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