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Need help making a fake hypodermic syringe Answered

Hello. I'm set to film a scene where a needle is used to inject someone. I've found a lot of places that sell and rent fake hypodermic needles, but way over my budget. Is there anyone here who would/could be interested in making one for these? I attached a video of one being demonstrated. I'm just having a mental block on how to create one myself.


http://www.youtube.com/watch?v=htxmJFg-dik

There's definitely a spring mechanism, and the tip is dulled. Other than that, I'm lost.

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TonyS297
TonyS297

9 months ago

I was able to get this working okay. I took a syringe, cut the metal tube short (almost flush with the plastic portion), smoothed the end, then used a sewing needle (with the tip snapped off and sanded) for the retractable part. A soft spring with the end bent around is threaded into the eye of the needle. To keep the spring in place, a sheet of Mylar (doesn’t have to be) is glued onto the backside of the tip. Since the assembly takes up some room, the tube that normally goes into the tip is drilled out, meaning this design won’t work as easily on the thin 1mL syringes, and also, the tip isn’t held well into place (I put an o ring around the tip as a temporary fix to this. Glue would also work).
Also, to simulate pumping liquids, a brass tube is routed through the plunger. Holes and a channel in the plastic were made with a soldering iron; a drill would probably work too. The center of the sealing piece has a hole drilled down its center and a channel for the tube cut into its side (it pops off with some force on my syringes). Afterwards, it is put on over the tube and both the tube and the sealing piece are glued to the plastic part of the plunger with CA (for convenience).
Since this wasn’t very clear, if anybody reads this, I might respond to comments depending on whether I get notified.
This is hardly the optimal design.
Make sure the spring is very easy to compress, because otherwise it’s a little painful to push the tip into the skin, especially when angled from the vertical.
I had to coil my spring tighter since it was too large originally.
My needle exerts about 150g of force when it’s fully compressed. Less would be better.
The assembly leaks a little through the gap between the fake needle and the tube of the real needle. It also leaks from the compromised luer lock. Silicone grease might be able to seal up the former and that or glue could fix the latter, if you intend to use it with liquids.
There can’t be much air gap between the piston and the liquid with this design.
This is hardly optimized, if that isn’t clear. Don’t feel restricted by the design choices I made. Most are the result of laziness and availability.
I also put a little CA glue on the end so that when it is “pulled out,” it tugs a little on the skin like a real syringe. That didn’t work all that well, since it’s still pressing into the skin for most of the release. I’m not sure how this could be fixed practically. Possibly, the sliding needle could be loosely friction fit (instead of the spring) so that, with glue, it is both pushing when it would be pushing and pulling when it would be pulling. Controlling the amount of resistance would be hard. It might be accomplishable by filling the tip with some viscous liquid and putting a big thing on the back of the needle.

8A853C9D-3378-4824-A90F-E5D8CE431EA4.jpeg2F357AC0-D30B-4550-8CF5-68ECBACBA944.jpegF649B51D-585F-4617-AF2B-159BF0DA5882.jpeg1CE2626A-A406-4B55-A198-BD5AF127BE9F.jpegA0019AB8-EF75-4CCB-A978-21FB538A9EB6.jpeg03163EAB-B50F-49B4-9435-1CC88F3542ED.jpeg503AE702-8387-4CBB-9447-71632C1BDA43.jpeg
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TonyS297
TonyS297

Reply 9 months ago

Also, the tip only retracts half a centimeter or so.

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ekwhoa
ekwhoa

6 years ago

Did anybody ever find a proper way to accomplish this?

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Tomdf
Tomdf

8 years ago

So I did some extensive googling and couldn't find a design for these at all. I'm shocked honestly, these fake syringes have been a standard prop for decades. It must be a trade secret. I'd really like to see some ideas for this as well.

How much do the ones you found cost? Are you handy with a dremel and epoxy?

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Tomdf
Tomdf

Reply 8 years ago

Ok, so I couldn't stop thinking about these; I've always wondered how it was done. Anywho, this is how I would do it. The concept relies solely on finding two syringes, one small enough to fit just inside of the other. The metal tube can be found in the hardware store, and the spring inside a cigarette lighter.

I'll stop by the apothecary tomorrow and see if they'll let me peruse their hypodermic selection. I think this would work.

syringe prop.jpg
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fl3xtra
fl3xtra

Reply 8 years ago

That looks awesome. i'm gonna have to try this, very soon. lemme know if you have any luck. i wouldn't mind dropping a some money to have this built.

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Tomdf
Tomdf

Reply 8 years ago

For sure, this is now officially on my build list. I can't believe the pre-fab ones are that expensive, that's insane! If we get these working let's go into business lol.

I did go down to the pharmacy to get syringes, but they weren't too keen on just letting me browse what they had. I'm planning on ordering some 5ml and 3ml off the internets. When I finally do get them and have a functional version I will likely just post it as an instructable.

If you finish something before me I'd be very interested in checking it out.

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fl3xtra
fl3xtra

Reply 8 years ago

try your local veterinary office first. they might be a little more open to the idea of handing out syringes. i'm gonna call mine tomorrow.

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fl3xtra
fl3xtra

Reply 8 years ago

where were you planning on getting the metal tube?

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Tomdf
Tomdf

Reply 8 years ago

My first stop will be a hardware or craft store to find one of those K&S precision metal displays, I'm fairly certain it will have something small enough.
If that doesn't work I'll end up turning to McMaster Carr for these 1/8" outer diameter aluminum tubes.

I'm not sure what kind of finish this metal tube should have to hide it, but right now I'm thinking that a mirror finished would be best. My theory is that it would be camouflaged by the reflection of the liquid.

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fl3xtra
fl3xtra

Reply 8 years ago

Hey Tom, just seeing how your progress was coming along?

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Tomdf
Tomdf

Reply 8 years ago

Hey there, the progress is moving, but rather slowly. I did learn that buying syringes online or from a pharmacy is a pain and they mostly come in bulk anyway. I did find a set of syringes at my parents house (they live on a farm and have some vet supplies,) but they had pictures of dogs on them -_-

My next attempt will be to print that picture out and take it with me to a vet supply store so I can explain what I'm trying to do. Maybe it is just the town I live in, but people get suspicious when I try to tell them what I want, and I think the plans would show that I'm not just making the story up.

Have you found anything of use?

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bajablue
bajablue

Reply 8 years ago

I was just going to suggest a Veterinarian's office, Tom. It's perfectly legal to purchase needles and syringes... and they probably won't even ask questions.

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fl3xtra
fl3xtra

Reply 8 years ago

Hey Tom, thanks for replying.

So far I've found these can cost from $200-500. I'm pretty handy, as long as I have directions, or some kind of tutorial. Thank you for finding that.