February 11, 2023

Replica B-25 Bomb Release Switch

STL’s for this Project are available for purchase from Cults3d.com

I really enjoyed making the B-17 Bomb Release Switch so I decided to make one for the B-25 too… This one has some added features for fun.

Just like the B-17 Switch this one was designed from the original plans so its pretty accurate (as far as I can tell) to the real thing.  Like with the B-17 release some dimensions were changed slightly to make it easier to 3D print.

This one was designed after a B-25C (or D) I think later models used a hand held release.

Here are all of the 3D printed Parts before finishing. Supports were only required on the Guard and Wing Nuts.

The Spring is printed flat and then heated up and bent to about a 10° angle on the line.

Hardware for this one is a 3 Position Momentary Rocker Toggle Switch, (2) 8-32 & (2) 6-32 Round head screws, a pin (made from Filament), and 2 small magnets.

All of the pieces and parts after finishing and painting.

Just like on the original… the Guard and Spring have a few spots that are left unfinished because they are mating surfaces and will wear.

The original cover was black with polished lettering so I printed the part in silver PLA, painted it black, then sanded of the faces of the lettering to simulate the original finish. (I did print with a .25 nozzle to get better lettering on this part.)

I took the easier route on the design of the inside/lid mounting of this shield box because the original used some funky latch type springs so I just printed integrated mounts and tapped them after printing.

Grommet for the wire exit. (I designed a simulated printed version but decided to use a real rubber grommet instead.)

The switch just gets force tapped into the cover on this version also.

The Guard Bracket and Spring are attached to the Cover with the 6-32 screws. (guard first with the sprint on top of it) These would also have held the switch in place on the original cover.

The guard is held in place with a pin made from filament. The ends are just melted flat by heating a flat head screw driver and pushing against the end of the filament. (one end has not been melted yet in this picture.)

The cover is attached to the box with the 8-32 screws.

These are simulated thumb screws. (I believe the ones used on the original release are quarter turn lock screws.  Magnets were designed to go in the bottom to fasten them to the screws but they ended up being snap fit enough not as to not need the magnets.

Here they are snapped in place.

The switch tip extension is then pressed onto the switch to finish the Release switch off.

Just when I thought I was done with this box I decided to add a little fun to it. I found this Sound module on Amazon for $13.

It looked like a one piece module but it was just every thing was stuck to a single piece of double side tape which was great. this made it very easy to separate the board from the battery and speaker.

I did have to go back and redesign the box so everything would fit into it and still have access to the switch and USB plug.

The round hold is for the speaker and the other hole is so I can turn it on/off and charge the battery.

I did have to extend the speaker leads.

The stock module switch was also cut off so the plug could be wired to the release switch.

A quick test to make sure everything still works…

I had to hack out the switch cover with a Dremel so the board fit in position. I did redesign this part but didn’t want to reprint and refinish everything.

Wiring for the release switch. The extra red wire loop is just so pushing the switch either way will work.

The speaker is just held in place with hot glue.

The original double sided tape is used to secure the board and battery to the box side.

Here you can see the access to the on/off switch and USB connector (for up loading/recharging) on the bottom of the box.

I also added some rubber feet to keep the speaker off the desk top so you can hear it better.

Here is the finished B-25 Bomb Release Switch.

Ready to drop some bombs.

This was another fun project to build.

 

 

And now for the Fun….

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