Rubber band power

Rubber band power

Post by People are animals, to » Tue, 15 Feb 1994 20:54:00



Anyone interested in ***-band power?
It's cheap, it's effective, and it poses a major
parachute ejection challenge.
So far I have only used sling-shot type launchers.
Maybe the band could turn on board counter-rotating props.

I've gotten 100 feet or so of altitude using a *** band
attached to a stick at one end, and to a hook on the model.
I had a 1.325 "  diameter model with a parachute that went
less high.  The parachute wasn't too reliable but it worked.
It was in a hatch which pulled open by *** band action
when decreasing force on an airfoil allowed the hatch to
open.  There must be a better way -  and also a more
efficient launcher design.   Any ideas?

Nathan

 
 
 

Rubber band power

Post by Andy Dingl » Wed, 16 Feb 1994 08:17:09


When I was a kid I had a commercial sling-shot rocket, with parachute
recovery. It had a moulded plastic, ready-assembled, body about 15" long.
Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
hatch was kept closed during flight by a long lever down the fixed side of
the fuselage with a hook near the pivot at the top, and a tiny vane at the
aft end.

Flights of a couple of hundred feet (not always vertical !) were possible,
when powered by a long enough stretch of glider launch bungee.

--

Klein bottle for sale.     Apply within.

 
 
 

Rubber band power

Post by Willia » Wed, 16 Feb 1994 10:59:15


While we're mentioning "alternative" power sources, you might as well also
consider compressed gas mortars.  Mortars are the method of choice for
launching "real fireworks", achive altitudes equal or greater than most
model rockets, and when powered by a CO2 cylinder/burst disk arrangement
eliminate and chance of fire problems.  The challange is to build a rocket
(or other device) that can take the acceleration, and to figure out a way to
deploy recovery/etc somewhere near apogee...

Chops

PS:  But it's STILL not a rocket!

 
 
 

Rubber band power

Post by kaplo.. » Wed, 16 Feb 1994 15:50:26



Quote:
> Anyone interested in ***-band power?
> It's cheap, it's effective, and it poses a major
> parachute ejection challenge.
> So far I have only used sling-shot type launchers.
> Maybe the band could turn on board counter-rotating props.

> I've gotten 100 feet or so of altitude using a *** band
> attached to a stick at one end, and to a hook on the model.
> I had a 1.325 "  diameter model with a parachute that went
> less high.  The parachute wasn't too reliable but it worked.
> It was in a hatch which pulled open by *** band action
> when decreasing force on an airfoil allowed the hatch to
> open.  There must be a better way -  and also a more
> efficient launcher design.   Any ideas?

> Nathan

I first heard this story from the "original" pink book lawyer, from some early
single-digit NARAM. Paul Hans (now part of ISP) had a *** band assisted
tower launcher. To his embarasment, he misfired, but th emodel was still
tracked at something around 300'! That's why the pink book now has the rule
that no momentum can be imparted to the model that did not come from the motor.

Bob

 
 
 

Rubber band power

Post by People are animals, to » Wed, 16 Feb 1994 21:27:00


Quote:
>When I was a kid I had a commercial sling-shot rocket, with parachute
>recovery. It had a moulded plastic, ready-assembled, body about 15" long.
>Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
>hatch was kept closed during flight by a long lever down the fixed side of
>the fuselage with a hook near the pivot at the top, and a tiny vane at the
>aft end.

How does that parachute system work?
How does the lever release the parachute, and
what provides the force for opening the
hatch.

Was it reliable?

Thanks for the further info.

Nathan

 
 
 

Rubber band power

Post by Michael Matthew Gusli » Thu, 17 Feb 1994 03:05:07


Quote:

>When I was a kid I had a commercial sling-shot rocket, with parachute
>recovery. It had a moulded plastic, ready-assembled, body about 15" long.
>Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
>hatch was kept closed during flight by a long lever down the fixed side of
>the fuselage with a hook near the pivot at the top, and a tiny vane at the
>aft end.

Yeah - I've got one of those aeronautical kits - from the same people who
brought you the 20-in-1 RatShack kits.....

I never built the thing, though.  The balsa was the worst I have ever seen.
I would hate to see the actual model rocket one in flight on a high thrust
motor.  Can you say "shred"?

Quote:

>Klein bottle for sale.     Apply within.

Moebius strip for sale.     Apply inside.

- Michael "It wasn't a mistake, it was a learning experience" Guslick

 
 
 

Rubber band power

Post by C. D. Tavar » Thu, 17 Feb 1994 04:45:42



Quote:
> >When I was a kid I had a commercial sling-shot rocket, with parachute
> >recovery. It had a moulded plastic, ready-assembled, body about 15" long.
> >Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
> >hatch was kept closed during flight by a long lever down the fixed side of
> >the fuselage with a hook near the pivot at the top, and a tiny vane at the
> >aft end.
> How does that parachute system work?
> How does the lever release the parachute, and
> what provides the force for opening the
> hatch.

The one I had as a kit was shaped like a jet aircraft, but I assume
it's the same.

The jet was hollow and the parachute was inside.  The latch keeping it
shut was at the nose and was attached, via a long, skinny boom, to the
jet's tailfeather.  A *** band applied force to raise this boom
away from the body and open the latch.

You would launch the model using a hand-held slinghot, holding it by
the tail feathers.  The airflow over the body in flight kept the
tailfeathers back and down, and thus kept the latch closed.  Once
the model slowed down, the force of the *** band overcame air
resistance and opened the clamshell, releasing the parachute.

Quote:
> Was it reliable?

It was reliable unless you launched it on a low trajectory.  It has to
slow down to work.  If it doesn't slow down, it prangs.
--



 
 
 

Rubber band power

Post by Andy Dingl » Thu, 17 Feb 1994 07:07:28




Quote:
> [I said]
> >When I was a kid I had a commercial sling-shot rocket, with parachute
> >recovery. It had a moulded plastic, ready-assembled, body about 15" long.
> >Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
> >hatch was kept closed during flight by a long lever down the fixed side of
> >the fuselage with a hook near the pivot at the top, and a tiny vane at the
> >aft end.

During flight, aerodynamic loads keep the lever alongside the rocket body.
At apogee, it noses over and the weight of the lever tips it forwards and
outwards, unhooking the latch at the front. Aerodynamic forces then pulled
the hatch backwards and open.

Sounds crude, but it worked fine. Don't forget that catapult launching isn't
exactly HPR. It was reliable for many flights, until a bad landing tore the
hatch hinge off. I never found a way of reattaching the soft-ish plastic
parts.

--

                    Free the Halifax One !

 
 
 

Rubber band power

Post by Mark Bundi » Thu, 17 Feb 1994 22:53:44



Quote:
(Andy Dingley) writes:
> When I was a kid I had a commercial sling-shot rocket, with parachute
> recovery. It had a moulded plastic, ready-assembled, body about 15" long.
> Half of the diameter was a "crocodile jaw" hatch, hinged at the rear. The
> hatch was kept closed during flight by a long lever down the fixed side of
> the fuselage with a hook near the pivot at the top, and a tiny vane at the
> aft end.

> Flights of a couple of hundred feet (not always vertical !) were possible,
> when powered by a long enough stretch of glider launch bungee.

Higher flights are possible.  In 1971, I saw Guppy Youngren assist in the  
launch of such a model by allowing someone to climb on his shoulders in an  
effort to increase the stretch of the ***.  After having the bird pass by  
his nose by the narrowest of margin (the "launch stack" of two people was a  
bit wobbly), Gup decided to stick to black powder power.....

=================================================================
Mark B. Bundick         "Running a NARAM will never be harder
NAR Vice President      than keeping NAR history straight"

 
 
 

Rubber band power

Post by People are animals, to » Sat, 19 Feb 1994 20:32:00


Quote:
>Higher flights are possible.  In 1971, I saw Guppy Youngren assist in the  
>launch of such a model by allowing someone to climb on his shoulders in an  
>effort to increase the stretch of the ***.  After having the bird pass by  
>his nose by the narrowest of margin (the "launch stack" of two people was a  
>bit wobbly), Gup decided to stick to black powder power.....

How about sticking a 10 -15 foot pole in the ground at a slight angle
and stretching the *** band from that?  How high would the
projectile go?  This would be really safe - no hands near the
end of the *** band!

Also, will the ***-band force be proportional to the distance
stretch as they taught us in Physics 101, or will it be less
due to time lag, or something.  If I find time I might write a
computer program for altitude prediction.

 
 
 

Rubber band power

Post by Iskandar Ta » Wed, 23 Feb 1994 00:20:19



Quote:

>Higher flights are possible.  In 1971, I saw Guppy Youngren assist in the  
>launch of such a model by allowing someone to climb on his shoulders in an  
>effort to increase the stretch of the ***.  After having the bird pass by  
>his nose by the narrowest of margin (the "launch stack" of two people was a  
>bit wobbly), Gup decided to stick to black powder power.....

There are these gliders that date back to the 40's that have wings
that rotate 90 degrees, then fold backwards. They're launched with a
stretched ***band. The highest I've seen one of these launched was
at the '90 Nats - someone climbed up on to the top of a motor home and
they stretched a *** band from the top of the motor home to the
ground.

Speaking of vertically launched *** powered toys, there is a French
butterfly shaped helicopter toy that dates back to the latter part of
the last century. Pretty simple - looks like a stick *** model
except it has a propellor the length of the wings. I imagine you could
make it look like almost anything you wanted to - I've seen pictures
of a Gee Bee R2 shaped one. Why not build one of these with a piece of
BT-50, huge delta fins, a carved nosecone and a rotor, say, a foot in
diameter? Matching the *** cross section to the rotor, you might be
able to get this thing to hover for a short amount of time.

Can someone draw up one of those rocket-powered helicopters and post
it on sunsite? Maybe Postscript might be a good file format for this..

--
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Iskandar Taib                          | The only thing worse than Peach ala