Recommendations for a floppy heart prop?

[helix_3]

I'm working on a life-sized beating heart, and I want it to look as realistic as possible. Making it move won't be too difficult (servos), but I'm having a bit of trouble figuring out how to procure the heart itself. Real beating hearts are very squishy and floppy, but everything I have found is made of cheap, semi-flexible plastic.

So, does anyone have any ideas? If necessary I can buy a heart-shaped jello mold and fill it with latex, but I have no experience with such an involved process, nor do I know if that will create exactly what I want.

 

[cavx]

I would think Latex should work pending how thick you make the walls.

 

[rescue542]

I agree. I think to get as close to the feel of a real heart, latex is probably going to be the best thing.

 

[helix_3]

I would think Latex should work pending how thick you make the walls.

Do you think a latex walled heart, filled with a gelatinous fluid (ie styling gel, flower arrangement gel, etc) would look good? I want to make sure the heart moves and jiggles with inertia.

 

[ahoudini]

Um, I am all for squishy and ooky, but the heart, itself, is made out of thick muscle and ought to jiggle about as much as a raw rump roast. It is not as hollow as it seems. Now the cut-off great vessels coming into the top ought to jiggle, depending on length. The aorta is thick walled and so think 1 1/4" OD latex tubing with about 1/4" wall thickness and for the vena cava and pulmonary arteries and veins, 1" OD with 1/8 " wall thickness. Just depends whether you are going for maximally real or maximally ooky! Seems like you could carve something the rough shape out of foam rubber, with a cavity inside for your servo (maybe leaving it open to the down side), skin the whole thing with Plastidip and paint 'er up…

 

[helix_3]

Um, I am all for squishy and ooky, but the heart, itself, is made out of thick muscle and ought to jiggle about as much as a raw rump roast. It is not as hollow as it seems. Now the cut-off great vessels coming into the top ought to jiggle, depending on length. The aorta is thick walled and so think 1 1/4" OD latex tubing with about 1/4" wall thickness and for the vena cava and pulmonary arteries and veins, 1" OD with 1/8 " wall thickness. Just depends whether you are going for maximally real or maximally ooky! Seems like you could carve something the rough shape out of foam rubber, with a cavity inside for your servo (maybe leaving it open to the down side), skin the whole thing with Plastidip and paint 'er up…

A heart is undoubtedly fibrous and tough, but when in motion they do look pretty jiggly: Live Beating Heart and Heart Surgery - YouTube (NSFW-ish) I agree on the latex arteries; that's an excellent materials to use for this project.

 

[ahoudini]

I'm gonna concede this one. The fact that different parts are contracting at different times definitely gives it a jiggly look. If you were trying to mimic this with just one servo, a jiggly material would definitely help achieve that look. What about just a slush cast latex shell with the servo horn attached via cord to the inside of the shell at two different points? When it rotates one way, it pulls in on one part, and when it rotates the other way it pulls in on a different part and the first part relaxes.

 

[rescue542]

Ahoudini, you really have this heart thing down. Is there any real good way to make a realistic model of the heart?

 

[ahoudini]

Some of the commercially available latex props look pretty good. Failing that, get some good images online and sculpt it out of clay, make a plaster mold and cast it in latex. Like making a mask, just in miniature. I would search ebay for "latex heart prop" first and see what you can find. A person's heart is about the size of their fist but, as with most props, you could cheat slightly bigger if you are worried about it being seen.

 

[rescue542]

I could send you some scans of the anatomical heart drawings from my paramedic book if you want but they're not the best.

 

[helix_3]

I'm gonna concede this one. The fact that different parts are contracting at different times definitely gives it a jiggly look. If you were trying to mimic this with just one servo, a jiggly material would definitely help achieve that look. What about just a slush cast latex shell with the servo horn attached via cord to the inside of the shell at two different points? When it rotates one way, it pulls in on one part, and when it rotates the other way it pulls in on a different part and the first part relaxes.

That's more or less my current plan. I'm not sure if cord/ rigid wire will create too pronounced of a contact point with the shell (ie it looks like it's poking through at a single point), so I might 3D print some big rounded servo horns to better spread out the contact points. Or perhaps I will make some rounded panels, adhere them to the interior wall of the heart, then anchor those to the wire? I will have to play with it and see what works.

Can you recommend any latex sources? I saw that Hobby Lobby carries some at a reasonable price.

I could send you some scans of the anatomical heart drawings from my paramedic book if you want but they're not the best.

Thanks for the offer, but I'm content with what I can find via GIS.

 

[ahoudini]

I use mold builder for small jobs like this, or even the latex meant for backing small rugs to make them slip proof. You can usually get these at local hobby/craft stores. Monster Makers is great for larger volumes. You don't want the thin stuff sold for direct application on the skin.

 

[helix_3]

Aw yis, 40% off hobby lobby coupon time. Now I just have to wait and find a Halloween heart jello mold that I like.