[BProckets] Cluster ejection

[Mike Harris]

For sheer pins, just small plastic dowel or nylon bolts, of a size 
determined to sheer off upon the ejection charge but otherwise hold 
together. styrene rod from hobby stores is popular in smaller (to 4 inches) 
rockets; 2-56 nylon in 4" or so. 1 or more depending on diameter and total 
amount of resistance needed for the application.

Here's a good page off an oustanding site:

         http://www.info-central.org/construction_shearpin.shtml

regards, Mike

At 07:10 PM 3/1/2005, mrgizmo wrote:
>I never thought of that, that would not be a nice sight to see my recent
>scatch build in flames. What are shear pins and what do they accomplish?
>
>Thanks
>Mike
>
>
>----- Original Message -----
>From: "Mike Harris" <mikeharris at privatedata.com>
>To: "Black Powder rockets discussion list" <bprockets at amateurrocketry.com>
>Sent: Tuesday, March 01, 2005 6:15 PM
>Subject: Re: [BProckets] Cluster ejection
>
>
> > No it is not a great idea. Maybe now your motor that didn't start now
>fires
> > up from the top from the match at the same time the chute ejects thus
> > turning it into an interesting pyro sky work that hopefully at best
>results
> > then in a flame flare (burning rocket) coming down under chute.
> >
> > Most likely you won't be *that consistent* with your ejection delays and
> > that the bonus charges won't blow anything up. Any charges post fact are
> > not relevant. So use shear pins, not friction fit, for your nose cone, and
> > have a long enough shock cord to dissipate even a triple ejection
> > separation, and you should be fine.
> >
> > Either that or, as most with EX do, use electronics for any ex motor.
>Along
> > those lines, the magnetic apogee kits are cheap, effective, and cool.
> >
> > Sure it's cool to do *everything* including ejection delays, but it's
> > another problem to learn to do right and is perhaps the most critical
>short
> > of not cato'ing your motors, so why not ensure you get your rocket back
>for
> > it's next flight.
> >
> > regards, Mike
> >
> > At 02:03 PM 2/28/2005, mrgizmo wrote:
> > >That is a great idea about using 1 chage that is quickmatched to all
>theee
> > >motors, I never thought of that, its likely what I will use.
> > >
> > >----- Original Message -----
> > >From: "Dan Durachko" <DanDurachko at psu.edu>
> > >To: "'Black Powder rockets discussion list'"
><bprockets at amateurrocketry.com>
> > >Sent: Monday, February 28, 2005 12:27 PM
> > >Subject: RE: [BProckets] Cluster ejection
> > >
> > >
> > > > I imagine the engine loading procedure and mount design would preclude
> > >such
> > > > a measure but could you cross-match (w/quickmatch) all three of the
> > >ejection
> > > > charges to synchronize them and ensure ejection?  Also, I imagine
>there's
> > > > enough slop in powder amounts for efficient ejection that you could
>load
> > > > each of the three engines in the cluster with 1/2 the amount needed
>for
> > > > positive ejection and even if all three fired you still wouldn't cause
>any
> > > > damage?  Let me know how things work out and how you did it.
> > > >
> > > >
> > > > Good point, I guess the dilemma isuse one ejection charge and if that
> > >motor
> > > > dosnt ignite the fiberglass nosecone turns into a pretty dangerous
> > > > projectile. But if I use 3 unsyncronised ejection charges the result
>could
> > > > burn up the chute(s).
> > > >
> > > > > >I am currently finishing up a 1/3 scale Harpoon AGM-84, which will
>fly
> > >on
> > > > a
> > > > > >cluster of 3 G-75's I was just wondering if I should just set up
>one of
> > > > the
> > > > > >motors with an ejection charge or all three?
> > > > >
> > > > > I've wondered about this too.  I guess it kind of boils down to
>whether
> > > > you
> > > > > feel you can reliably get ignition of all 3 engines in the cluster.
>How
> > > > bad
> > > > > might 3 synchronized (or unsynchronized) ejection charges be
>anyway???
> > > >
> > > >
> > > >
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