Cutting Donuts

 The Thrifty Rocketeer blog continues...

Whether you're launching low power or high power rockets, virtually every rocket relies on centering rings to hold the motor tube or casing in place. 

Whether they are made of wood, plastic, fiberglass or card-stock, the purpose is to hold and transfer that thrust from the motor to the body tube and to keep the force centralized for a smooth and steady flight.

In the case of low power rockets, the centering rings always adapt between the size of the motor and whatever body tube your rocket may feature.  As a result, there are certain custom sizes of centering rings that are available from virtually every parts supplier.

(If you're up-sizing a rocket, and are trying to fit a larger motor into an up-sized body tube, you probably will be looking at a customized wooden centering ring made from plywood.)

But virtually every rocketeer has looked at a toilet paper tube or a paper towel cardboard tube and thought, "Gee, that might make a neat little rocket."  Along with this thought comes thoughts of various fin arrangements, design and balancing for either appearance or performance or both.

But frequently overlooked is the need for appropriate centering rings.

Oh, I know what you're thinking... "Why, I'll cut mine from cardstock with a pair of scissors."  And this could work, with the appropriate wood glue and filets holding them in place, along with making it more secure.

But last week I was at Hobby Lobby, making a quick run for a pair of motors and a small disposable rocket, when I found myself behind a woman who was checking out with hole punches.


Not just any hand held punches, but a desk top set that punched out an entire 1" circle. She had two, of differing sizes.

I asked her if those were fixed dimensions or adjustable, and she confirmed they were fixed sizes and intended for paper... to make party decorations or favors.  I sighed, thinking that I had either found a perfect fit for body tubes (not very likely) or missed the mark.

Then she suggested a "cricket" cutter which might be able to handle card stock.

I am unfamiliar with this, but an on-line inquiring revealed that it might be a "Cri-cut" that she was suggesting, possibly available from the local public library.


A phone call to the library was disappointing, as they did not have one, but they suggested an Ohio Maker Space that rented tools, and might have either a "Cri-cut" or a laser cutter.

Now, I don't have enough business to justify buying a laser cutter, but an hourly rate to use something pre-programmed to cut a series of centering rings might be attractive.  
Except, how much is your time worth?  Is it not easier to just buy the right sized rings from your rocket parts supplier?

This has been the Thrifty Rocketeer, musing, "Just how many rings would you have to cut to make a laser printer worth the investment?"

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