3-shot Internal Bomb Bay Design  
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3-shot Internal Bomb Bay Design - 4/28/2008 1:02:47 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		hi all. I designed and built an internal bomb bay mechanism that gets a lot of good attention at the field, so I thought I would share the design here for others. I built a clone of a Senior Telemaster, the Hobby Shack "Skyrider", to serve as the bombing platform so the dimensions of this mechanism are suited to fit an airplane with the interior volume of the Senior Tele. The design is very simple, and easily changed to accomodate other models.

I started out with several design criteria.
1. I wanted at least 3 shots before I had to land and reload.
2. I wanted the bomb bay to be internal.
3. I didn't want to have to take off the wings to reload.
4. I wanted the whole thing to operate on a single switch on my transmitter.
5. I wanted to be able to fly and drop s single, larger "bomb" if I wanted to.
6. It had to work extremely reliably (so that I didn't look foolish at teh field!).
7. Had to be lightweight and made from scrap materials I had laying around.

I managed to accomplish ALL of the above. Personally, I drop hackey sak balls since they don't go very far after impact. I also drop small parachutists and other objects. So, having said all that, let's see if I can adequately desribe it with photos and such...

What follows is a sequence of photos showing the steps in the operation of the bomb bay mechanism.
Photo1: Everything is cocked and ready
Photo2: Servo opens bomb bay doors. First bomb is dropped. Spring loaded clevis clicks into position behind 2nd saw tooth.
Photo3: Servo closes bomb bay doors simultaneously pushing sliding ratchet mechanism down. 1st saw tooth pushes 1st internal door latch out of slot allowing 2nd bomb to fall onto bomb bay doors.
Photo4: Servo opens bomb bay doors again. 2nd bomb falls. Spring loaded clevis clicks into position behind 3rd saw tooth.
Photo5: Servo closes bomb bay doors simulantously pushing sliding ratched mechanism down. 4th saw tooth pushes 2nd intenal door latch out of slot.
Photo6: Servo opens bomb bay doors. 3rd bomb falls.



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       Post #: 1

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:19:45 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		As you can see in the photos, everything is made from readily available materials. The wood is all 1/8" light ply, balsa, and a few inches of 3/8" square hardwood stock. The internal doors are made from bent coat hanger wire and 1/32" balsa. There are no complicated hinges, I simply drilled holes in light ply sides. The springs you see are leftover from Sullivan tailwheels. (The Sullivan tailwheels come with 2 springs meaning you always have one leftover.) Of course, you can use whatever you have laying around. The photos are of my one and only prototype, and there are a couple pieces on there that aren't neccessary. (I was experimenting with different way to spring load the clevis). In the end, my best clevis idea is pictured. I soldered one of my Sullivan tailwheel springs to the side of a clevis. At the end of the clevis is a short bit of 2-56 threaded rod and a bit of nyrod to make the length adjustable. Then I put a piece of fuel line over the whole thing to keep it from turning on it's own.

I'm providing a dimensioned drawing, but if you can figure out how this works, there are very FEW critical dimensions. The length of the door arms that clip into the slots is sort of critical since, if you make those too long, they'll hit other things. The most critical dimension is the spacing of the saw teeth. Even this can be adjusted to accomodate models of various size. Let me know if you need some help, adn I'll happily lend advice.

(in reply to iiiat)
       Post #: 2

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:24:03 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		In the photo, you see a 2nd spring (besides the spring soldered to the clevis). Thsi spring prevents the sliding saw tooth mechansim from slidign backwards and the servo drags the spring loaded clevis up and over the next saw tooth. Attach a spring wherever is easiest for this purpose.



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       Post #: 3

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:28:51 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		In my model, the bom bay is exactly the same width as the fuse. I glued sticks of balsa on the internal sides of the fuse that hold the bomb bay mechansim in position, them a spring clip (I made from a Briggs and Stratton recoil starter spring) clips onto the landing gear block to hold the whoel thing up in the plane.

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       Post #: 4

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:32:10 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		In my model, the top of the bomb bay is very close to the wing bottom, so there was no need to put a cap on the top of the bomb bay. The internal doors can be left open to accomodate a larger "bomb" like a large parachutist or water balloon or whatever.

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       Post #: 5

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:37:15 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		I could give tons of little details that are mostly specific to my model, such as the holes for the cloths hanger hinges are about 1/4 inch from the edge of the bomb bay walls. This was to clear the small balsa sticks I glued inside the fuse that hold everything in position.

Here's another photo of the internal doors showing how I bent the coat hanger wire. Notice that I used double doors and that a small balsa tab on one door holds up the other side.

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       Post #: 6

RE: 3-shot Internal Bomb Bay Design - 4/28/2008 1:39:13 AM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		Leaving one side mostly open makes loading easier.

(in reply to iiiat)
       Post #: 7

RE: 3-shot Internal Bomb Bay Design - 4/29/2008 12:36:28 AM   
farr301


 

Posts: 121
Joined: 8/11/2007
From: Allen, TX, USA
Status: offline 		Thats's a very nice setup. I'm sure everyone would enjoy a set of plans

Farr301

< Message edited by farr301 -- 4/29/2008 12:38:35 AM >

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       Post #: 8

RE: 3-shot Internal Bomb Bay Design - 5/5/2008 5:29:28 PM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		Thanks Farr,
If anyone has any questions, I'd be happy to answer. I'm repeating myself again when I say that very few of the dimensions are critical. It's a very simple design that can be easily modified. For instance, all the 3/8" dimensions are 3/8" becuase that's the size of the hardwood stock I had laying around. *shrug*. I used 1/2" for the saw teeth because 1/2" is easy to work with. *shrug*. After you stack the 3 saw teeth together, the location of the 4th saw tooth becomes self evident and depends on the distance between the first internal door and the 2nd.

I think the main thing to be carful of is to not let the swinging door levers get too long so that they might hit other things.
There's no need for the sliding mechism to be centered in on the side of the bay. In fact, it's probably better to build it closer to the side near door levers so that the levers dont' need to be very long.

Maybe I'll build another so that I can document the build here. I realize all the made up terms aren't helping to make things any clearer.

(in reply to farr301)
       Post #: 9

RE: 3-shot Internal Bomb Bay Design - 5/5/2008 6:16:34 PM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		I don't know if animated GIF files work here, but I've taken the sequenc eof 6 photos above and created an animated gif. W'll know if those work here in a moment.

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       Post #: 10

RE: 3-shot Internal Bomb Bay Design - 5/5/2008 8:04:10 PM   
Tall Paul



Posts: 4606
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: offline 		I did this one using a 2" diameter mailing tube.
Holds three ping-pong balls, drops one at a time.

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_____________________________

Sparky Paul
http://www.angelfire.com/indie/aerostuff

(in reply to iiiat)
       Post #: 11

RE: 3-shot Internal Bomb Bay Design - 5/5/2008 8:09:50 PM   
iiiat



Posts: 196
Joined: 8/25/2005
From: Mount Juliet, TN, USA
Status: offline 		Brilliant! I love it!
Can be rubber banded onto any plane. I may steal that one some time.

Thanks Tall Paul.

Tom

(in reply to Tall Paul)
       Post #: 12

RE: 3-shot Internal Bomb Bay Design - 5/10/2008 8:47:08 PM   
TJR1



Posts: 268
Joined: 3/20/2007
From: Mobile, AL, USA
Status: offline 		Does anyone have ideas for an internal, removeable Bomb Bay design? Also something simpler than the 3 shot design introduced here, although it's interesting .

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(in reply to iiiat)