Rubberband Catapult for the Steam Tramp

[Brooks]

We made a simple, rubberband catapult for the Steam Tramp. This morning we had a great launch of the RC plane off the catapult while the Steam Tramp was underway under steam. Totally cool, looked just like the real thing, Plane then flown to the lawn where it made a good landing: Bob as Pilot, John as Tramp Skipper, Brooks as Air Boss. Did not get that one on film, of course. The next attempt, the plane had cold motors, due to a glitch perhaps, and it went straight into the drink; naturally that was the one I filmed, hoho. The RC gear got wet and quit, though it had dried out and was working again by the time I got home. The rest of the launches were of Bob's glider, with the Tramp at its mooring, and John filmed them well. The wind ribbon on the aftermast was useful to John while manuevering the Tramp; the upwind bearing felt by the skipper on shore was not necessarily the same bearing for the Tramp at sea.

Mods to the plane: 1. The RC plane (Mattel Skyforce Canadian Firefighter) needed rudimentary landing gear, outrigger skids really, to keep it upright while awaiting the shot. Some 0.032" SS wire plus masking tape did nicely. The plane also needed a launch hook, and a paperclip plus filiment tape handled that. The Glider only needed the launch hook.

The Catapult: Simple design flight deck made out of cardboard. The RC release is just a nested brass tube that protrudes through the deck, holding the ring on the end of the rubberband. Flip the "gear" switch on the TX, and the tube retracts, freeing the rubberband for the shot. The launch rubberband is stretched about 7 inches; not much force is needed for these light foam planes. The only mod for next time is to put some rails on the flight deck, at the rear of the fuselage in launch position, to keep the light RC plane from being blown out of alignment while the Tramp is manuvering crosswind prior to it's turn into the wind for the launch. And to waterproof the RC gear *grin*.

[Brooks]

Couple movies, a glider launch, and the cold shot RC plane launch.

http://1stclass.mylargescale.com/Brooks/boats/catapult1.zip

[Brooks]

Had several good launches this morning using this frame on the Fire Tramp (moored). When my boating buddies get back from camping, we can try it while the Tramp is under tow. Another dunking of plane, though. Not sure why it did not climb after launch. I had taped-up the Rx, hoping to make it waterproof, but to no avail. I'll try some silicon conformal coating on the PC board.

Good points of the Lego frame:
a) Easily adjust rubberband tension.
b) Simplified RC latch.
c) Frame easily modified, good for experimental work, or engineering for different ships.
d) If painted grey, or made with all grey Legos, would look more like the open framework catapults (used by warships for spotter planes) than the cardboard launch ramp style catapult.

Bad points:
a) Fusalage supports (to keep fusalage from blowing off the frame prior to launch) are unique to the particular aircraft.
b) RC latch requires Tx in hand to set (or a friend to operate Tx while you set the latch).

[tim slocum]

Brooks awesome catapult. A little idea from our BB model warship brothers, to keep your reciever dry, blow up a baloon and push the reciever into the baloon as you slowly let air out.Make sure all your wires will be comming out the opening of the balloon.It may take a few tries to get a good baloon/rx seal. If done correctly, the balloon should conform to the rx making it waterproof. I've even heard of people incasing their rx in a solid block of silicone.Also, you could put the rx in a small tuperware type container with a small hole for the wires.Add silicone where wires exit the container. Just a few ideas.

[Brooks]

Hi Tim, I will try the balloon idea, I like the idea of tight conforming. The rx I need to waterproof is the airplane's; it fits tightly into the square in the fusalage just under the wing (empty in the photo cause it's out and drying). I use condoms, the unlubed ones, for my regular RC float plane's rx, and they don't conform, so I can't use them. But the balloons, or the spray-on silicon, may do the trick.

Incidently, thanks for the idea of making the tramps into aircraft carriers :-)

[tim slocum]

Brooks, when I suggested the tupperware idea,I forgot you where talking about inside the airplane,I'm 40 going on 80!! You know Brooks, they converted alot of fixed wing carriers into helicopter carriers...Hmmmm. I've been tring to get someone in the heli forum to recommend the best palm sized heli,but it seems these "toy" type heli's dont get no respect at all in the rc forums. I STILL havent built my barge made from WalMart "hulls" yet!! Do you think they ever had a helipad on a barge??

[machdog]

Bob flying.


http://video.google.com/videoplay?docid=9056260316333060233&pr=goog-sl

[Umi_Ryuzuki]

This is fantastic work.
If you get a moment you ought to patent it.
Some how some company is going to start selling one commercially, and
it might be good to benefit from it later... :p

Now if we could just match up the scale, this would be the ultimate in "totally cool"!
:cool:

[Brooks]

Thanks for the kind words, Umi. I notice that the Google site has numerous Lego catapult movies, it may be too late for a patent :-). I don't know any 1/72 RC planes, which is too bad, as they would be neat launching, zooming, and kamakazi-ing your warships in combat (instant sink, or immediate-head-to-shore-for-repair rule?). Since there was a possible US kamakazi in the Midway action (a land-based bomber was, possibly, photographed atop a Japanese heavy cruiser, I think), both Allied and Axis ships could use the technique.

The Mattel firebomber scale is not too far off the 0-scale ships, at least based on the size of a figurine compared to the cockpit of the firebomber. But it's a multi-engine plane, and pretty big to be prototypically launched from a catapult... a single engine spotter plane look better :-). People have taken the Mattel RC stuff and put it on other planes. I tried it on a Guillow's balsawood biplane glider, and it worked, for instance. Maybe a profile Rufe could be mocked up for your weekend battles :-).

http://www.hobbylinc.com/htm/gui/gui45.htm

[Brooks]

Sprayed with silcone conformal coating, the Rx's PC board becomes water-resistant. I also drilled drain holes in the grey plastic Rx box, and snipped a bit of foam off the battery backing plate, leaving drain scuppers. When the plane goes into the drink, you shake the water off, blow on the Rx to displace droplets, and you are good to go again :-).

http://www.mgchemicals.com/products/422a.html?PHPSESSID=7f6073cc2300daaaebaf1f40b28b68 46