The Dark Knight Sticky Bomb Gun 3D Printed Build – Post #3

So – I’ve been working on improving upon my design on the Sticky Bomb Gun from The Dark Knight (TDK), as I really don’t want this to be a static prop – I want it to be able to fold up and expand out, just like in the movie! I also want it to have a digital timer, but that is going to have to wait.

As I’ve mentioned in the past, most of the design relies on the use of magnets to make things stay in place where I want them. I’m not really concerned with magnets showing where they shouldn’t or don’t in the original because hey I like the way that magnets look!

I did receive my shipment of brass rods from and they definitely are the right size and were cut correctly as well! I made sure that after I received them, I measured them with the digital caliper and added about 1/64″ extra room in all the holes for them just to make sure they would fit.

I also put together all the previously-printed parts of my sticky bomb gun prototype. I did this very quickly, I might add, using just hot glue and some wood dowels from some foam brushes I had. Even though it was assembled hastily, it is simply amazing to be able to hold this thing in my hands!

After messing around a bit more with my 3D printer to make sure I was going to have successful prints, I started the process again with the rear handle/butt, the “spinner” that attaches to that, and the first main piece that those rods extend from, and really really sanded the handle and spinner down. I didn’t even know there was 2500-grit sandpaper until last week!

Now it’s time to test how those rods actually move in and out of that thing. Unfortunately for me (and everyone else reading this) I am nowhere near a mechanical engineer, nor am I someone who knows what I’m doing. What I tried to do is make sure that those four holes on that big rectangular piece match up with the four holes on the “spinner” piece. I actually did a copy/paste of the face from the bigger piece and made it into the smaller piece just so they’d line up!

There was also some uncertainty around how to ensure that a) the rods fit all the way into the “box” and b) the rods didn’t come all the way out of the box when I pulled on that rear handle. I think I’m either going to go with just a cotter pin on each rod, or maybe even a “plug” that I’ll print that will fit (and be glued) inside the end of each rod inside the box that will prevent it from coming all the way out. Anyone have better thoughts on that? Please comment below if so!

I also didn’t want the handle to “rock” when in the open position due to not enough plastic holding the rods inside that box. So, I designed the box with about 40mm of “hole” inside the box to hold the rods in place. However I noticed that the rods don’t come out enough, even though the measurement was dead on! I measured my Hot Toys version and it shows a 11.25mm distance when open. Multiplying that times 6 (since it’s 1/6 scale) it comes out to 67.5mm, so that is what I planned and designed for. Unfortunately when you look at it, it just doesn’t match up proportionately to the eye — they should come out a lot more than that, like 90-95mm.

That means I need to change the width of that area holding those rods in — I moved it down to about 11mm to give those rods enough room to come out, while still hopefully leaving enough to hold them in without rocking. I think I’m going to have to test that and see how well it works, but it seems to at least look right!

I’m going to give that first piece another print and test and see how it goes ..



Check out the Finished version 1 of the Sticky Bomb Gun here!

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