Positive bomb release mechanism

[neistridlar]

Judging by several of the flitetest videos, it seems that dropping bombs from model airplanes is not nearly as easy as it sounds. The biggest problem seemingly being that just letting go of the bomb isn't always enough. And a second issue being that servos don't do so well under continuous load. So I decided to try to come up with a simple mechanism that would both hold onto the bomb without load on the servo, as well as pushing the bomb out once released. This is what I came up with:

It uses two pieces of moderately thin material, say 4mm plywood or similar, as well as two pins, could be barbecue skewers. The mechanism resides in a slot in the wing. The pins are attached to the wing to provide a secure stop. There is a c-shaped piece which is attached to a servo, or mounted on a pivot, and actuated remotely by servo wire. The inside of the hook-shape is circular and concentric with the pivot, so that when the bomb is grabbed, no torque is put on the servo, and only a small torqe is required to release it. This is similar to the trigger mechanism on a gun, where only a light pull of the trigger can release a heavy spring. Once the hook is released the pusher engages, and the torqe from the servo is used to push the bomb completely clear of the slot. As long as the servo has enough torqe to push the bomb out, it should be nearly impossible for it to not separate from the aircraft.

It seems odd to me that I couldn't find other examples of similar mechanisms, given how simple it is. Maybe it is because it's a bad Idea? Anyways I intended to build a prototype in the not to distant future. Hope some of you will find a use for it as well.

 

[Michael9865]

Nice design.

 

[Crow929]

I like this idea too.
I am imagining loading the bombs might be a little difficult.

 

[SavageX89]

ooo! i like it!

 

[neistridlar]

I like this idea too.
I am imagining loading the bombs might be a little difficult.

Agree. Ideally the servo would retract slowly while loading. Might be possible to load it halfway with the power off, just pushing as far as it goes, then power on to load completely.

 

[neistridlar]

A little demo video of the prototype:

It seems to work well. As you can see the prototype is a bit rough, but it still releases easily, even upside down or under load.

Now onto CAD to fine tune the design, and make it so it can actually be fitted to a plane.

 

[SavageX89]

Looks like a solid prototype. I'm excited to see how it turns out.

 

[Bricks]

Why not use a piece of wire run thru blocks with the bomb or bombs hanging between the blocks. Add a much longer control arm to the servo to pull the wire thru the blocks. Could be set up on a multi position switch so you could drop one bomb two bombs or all at the same time.

 

[SavageX89]

Why not use a piece of wire run thru blocks with the bomb or bombs hanging between the blocks. Add a much longer control arm to the servo to pull the wire thru the blocks. Could be set up on a multi position switch so you could drop one bomb two bombs or all at the same time.

I've used a similar system under the wings of my FT Cub. Wasn't super effective the way I had it. Nor was it very stable in holding the bombs.

 

[Bricks]

The spacing of the blocks should match the width of the holder on the bomb so it does not wiggle around.

 

[neistridlar]

Why not use a piece of wire run thru blocks with the bomb or bombs hanging between the blocks. Add a much longer control arm to the servo to pull the wire thru the blocks. Could be set up on a multi position switch so you could drop one bomb two bombs or all at the same time.

I explained why in the first paragraph of the OP, but the short version is: Sometimes things get stuck. this mechanism is designed to push the item clear of the mount, thus leaving it unable to stick. Nice when you absolutely need the drop to happen reliably. Say for instance you have a heavy payload under each wing, both need to release at the same time to keep the plane controllable.