13mm motor spinner
 

Already printed, no supports required. Waiting for a combination of city fire ban ending plus nice (not cold) weather to launch on an away pad. To be powered by two A3-4s which will eject after the 4 second delay.

The 45 degree blade angle was chosen simply because it was a guaranteed minimum angle to not need supports. Relative airflow vector may prevent otherwise certain airfoil stall. The combination of factors affecting that relative airflow - upward velocity, RPM and resulting airfoil lift might make for interesting flight characteristics during ascent. Recovery characteristics will also be interesting to discover.

The very sturdy 155mm (6.1') diameter vehicle weighs 36 grams (1.27 oz).

:cool: Any idea what kind of altitude it should get? Seems like a pretty good small field bird.

Nice. For a few years. Dollar Tree had some Gyro Copters about 5 to 6" diameter, meant to be rapidly "pushed" along a spiral stick, that caused it to spin rapidly and fly with its on lift, till it slowed too much. I converted a few, using a single 13mm engine in the center.

A few years after that, Target had some large Gyro-copters, pulled by a string to spin them up. About 15-16" dia. Great size to fly on a C6.

More info: https://tinyurl.com/55pcw6w3

I have 79 13mm motors. I bought a LOT of packs for $1 each when our Walmart clearanced all Estes products years ago.

That spinner would be a good way to use them up faster than I currently do!

I really have no idea at all, not even a wild guess. Too high of an RMP versus vertical velocity will result in airfoil stalls and a turbulent "shadow" for the next airfoil in line. It could at some point in the ascent even become more like a super-draggy spool. If so, I'll reduce the airfoil count to three and also reduce their angle of attack while keeping the motor tilt at 45 degrees.

Lucky you for sure. This could be a motor burner alright. I had no 13mm motors other than some A10-0s given to me years ago and just bought a 4-pack of the more suitable A3-4s at full retail. If perfected and found to be consistently safe and sufficiently impressive/worthwhile, I'll post the STL.

Since this would be a true motor burner, I've wondered why Estes hasn't to my knowledge offered something similar to my design using tilted motors for spin-up.

Maybe after launching mine from an away pad, I'll find out why...

Smart phone video of first flight taken by someone else. It went quite high and landed in the middle of that baseball field seen downrange. As I expected, recovery was like a spool - tumbled. No damage to the craft at all. The 13mm A3-4 motors eject from the craft to slightly lighten it for descent.

I'm going to do additional launches to see if it's possible to optimize the design. I'll be taking my own videos next time with a DSLR.

https://www.dropbox.com/s/nzgz7nk5aih15h6/IMG_2544.MOV

Here is one made from a Honda fan blade: http://dars.org/gallery/s4s2001/fanblade.mpg


Bill

Next up is a test of a 3-blade version to see if it performs even better because of possible blade turbulence "shadowing" in the 4-blade version.

Even though there was no ejection charge damage on the original version, I've added a vent on the new versions. The pods were moved outward a few millimeters for more spin torque.

I'll also be testing flight safety with one motor failing to ignite.