I'm looking for suggestions, ideas, recommendations on how to design
anti-roll/spin into a typical model rocket.
Is it possible to design a rocket such that it will not roll on boost and coast?
Do a Google search on "rollerons".
An Idea I had in Evansville just came to mind Shockie.
Use old R/C helicopter mechanical gyro's. their cheap in the flee markets
I got two and you can't turn them when they are on.
the new Peizo gyro's have made the mechanical spinning gyroscopes obsolete.
put two at cross angles to keep the rocket straight or one to keep it from
rolling., or all three.
run's on 4.8 volts at BTW.
would make a real great NAR R&D project my Wave Rider Friend.
You might be on to something. I have a video of mid powered rocket in
the UK that flew with out fins. Even when the motor cut out the rock
was still pointing up. Weird and erie at the same time.
I looked up rollerons as they are used on the fin tips of the sidewinder missile.....
for the model rocket I have in mind they would only be 1/4" to 1/2" square, and it appears to me that the rotating wheel is enclosed in a box that can swivel freely......?
and how does this rolleron increase roll stability?
The little spinning wheel acts like a gyroscope... if the rocket is
rolling, the gyroscopic action wants to twist the movable part of the
fin so it acts like an aileron trying to roll the rocket the other way.
If you're only talking about a small rocket, then go with a 4-fin
design. Fins should be small, symmetrically airfoiled (i.e. flat,
with rounded leading and trailing edges), long root chord, and
short span. Align carefully with the long axis of the rocket.
Place the launch lug between 2 fins, not in a fin-BT joint.
I don't agree. Hemisphere airfoils encourage vortex drag at the tips
which is a contributing factor to low spin rates.
I would have said the opposite about rooot and span since a higher
aspect ratio fin (sticking out more) has more damping action as to spin.
Assuming it is straight to begin with.
I refer the reader to my prior post on the matter.
I invite BB to go away. While this was a tech post and probably wrong,
many of his posts are simple trolls or outright personal attacks.
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: email@example.com>
On Tue, 7 Oct 2003 21:18:28 -0400, "shockwaveriderz"
What kind of mission are you trying to perform? What are the
size/weight constraints you are working with?? Rollerons would be too
heavy for a 'typical' model rocket, whatever that is anymore.
On Wed, 8 Oct 2003 00:01:17 -0400, "shockwaveriderz"
That is what I suspected. Fins, particularly those with large spans,
have natural roll damping. If you remember the old Estes Camroc
Carrier(?), it had canted fins on the booster stage to help ensure
straight flights, and large uncanted upper stage fins that quickly
damp out the spin imparted by the booster fins.
Rollerons also provide roll damping. However, they are not practical
for your application and are best used for R&D.
At the FG level you could certainly go active and use a HH gyro system
to hold a fixed roll angle over your short flight duration.
I also built a high performance Cineroc carrier for the cross
Mississippi project. The fins were 3 1x2x1/16" plywood elliptical
fins. I would strongly recommend much larger fins for high pitch yaw
damping on video rockets. I built adjustable spin tabs into the fins,
so that any roll could be trimmed out over a series of flights. Of
course we never got a series that exceded 1 flight on each rocket. The
fins were cut from the trailing edge root to about the tip. Build up
a couple layers of Titebond on the edges and then glue together with
Tightbond. Finish and build as usual. The roll trim tabs can be
adjusted by heating and bending.
I indicate my fin slots within .001" using an indexing head on a Bridgeport
mill . My rockets don't exhibit any spin, either. Fin alignment is probably
the most important thing in preventing spin.
Monterey Machine Products
1504-A Industrial Park Street
Covina, CA 91722 U.S.A.
4 relatively long span fins, carefully aligned and shaped, and a
symmetric airframe; undamped, unbalanced forces are your enemy.
Symmetry and detail will minimize the tendency to roll making the job of
any active anti-roll devices either easier, or unnecessary.
Perfect fin alignment is probably the most important factor, period.
It goes without saying that a properly built fin alignment jig will go a
long way in preventing roll.
I wonder if offsetting the launch lug drag by having a second, oppositely
placed launch lug would delay pitchover substantially? Thereby prolonging
the time the camera would point downwards? Then again, shots of the
horizon as the rocket arcs over near apogee might be desireable.
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