Hello everyone,

I’m interested in building a mechanical head and I’m trying to get my head around the steps required to get something like that built. I’m looking at designs by Ron Cole and Jim Randall. They have been very generous by sharing info and pictures, but it is always difficult to interpret things from a distance. Specially things like linkages are difficult to visualize from 2d pictures without being in front of the puppet to see how things move. My main aim right now is to get the design(silicon skin) properly attached and registered to the head shell and the mechanics. Attached is a drawing of my understanding after looking at many examples online. Please correct any erroneous assumptions that I might have. 

Best regards,

Steven

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That looks like a pretty good process, although you need to be sure the shell is spacious enough for what you are putting inside. Also, use retarder and deadener when pouring the silicone so it has time to flow down to the bottom of the mould, or even better, inject so the silicone flows into the mould at the lowest point.

Do post pictures of your progress!

The design seems solid so far. Skinning a core definitely requires a fair amount of finessing no matter the method for doing so. Now, forgive me if I'm reading the diagram wrong, but it looks like you have to pull the silicone skin on and off of either the core or shell at least a couple times during the casting process. My only concern with that is with the undercuts caused by the screw heads and given how thin the silicone skin is for a puppet head mech is, there's likely a reasonably high risk of tearing the silicone around areas where it has to slip over the head of a screw. Once silicone tears (even in one small spot) it can be quick to tear more. Instead of screws as registration I'd lean more towards a solid shape like a small truncated pyramid or short cylinder, it'd minimize the amount of corners to have to stretch the silicone around.

Absolutely. Since this is my very first time doing this style of puppet I'll be doing some experiments. Specially comparing silicones like Dragon Skin 10 NV vs GI-1110 for the silicone, and Smoothcast 300 vs TC-816 for the mould. I also think I read somewhere large syringes can be used as an injector. Lots of things to try out.

Thanks 

Simon Tytherleigh said:

That looks like a pretty good process, although you need to be sure the shell is spacious enough for what you are putting inside. Also, use retarder and deadener when pouring the silicone so it has time to flow down to the bottom of the mould, or even better, inject so the silicone flows into the mould at the lowest point.

Do post pictures of your progress!

Ethan,

That makes sense. I would have to look in McMaster-Carr to see if they have something like that. Otherwise maybe I can model and cast something like that in plastic and see if it holds.

Thanks,

Steven 

Ethan Bartholomae said:

The design seems solid so far. Skinning a core definitely requires a fair amount of finessing no matter the method for doing so. Now, forgive me if I'm reading the diagram wrong, but it looks like you have to pull the silicone skin on and off of either the core or shell at least a couple times during the casting process. My only concern with that is with the undercuts caused by the screw heads and given how thin the silicone skin is for a puppet head mech is, there's likely a reasonably high risk of tearing the silicone around areas where it has to slip over the head of a screw. Once silicone tears (even in one small spot) it can be quick to tear more. Instead of screws as registration I'd lean more towards a solid shape like a small truncated pyramid or short cylinder, it'd minimize the amount of corners to have to stretch the silicone around.

Cosgrove Hall did something like the for their foam latex puppet heads for Wind In The Willows.  Since it was a TV series the foam would get a lot of wear and need to be replaced more often than the armature, so they made replaceable skins that slipped over the underskull and mechanisms.  They had plaster (or was it resin?) cores that duplicated the underskulls, except there was a simple bump where the toggles to move the skin would stick out, rather than undercutting behind the toggle like yours do around screws with mushroom heads.  They were just ball and socket toggles to move the skin, rather than complex geared or cable mechanisms, but there was a similar need to create a hollow on the inside of the skin where the toggle would locate itself.

The only bit I question is having screws where the head locks in to the silicone, possibly filling clay in around the threaded part near the head would create a hollow where the screw fits in, but isn't so much locked in.  Yes, the silicone will flex and come off, and in your simple diagram that looks pretty straight forward, but the actual shapes are more complex, and it's not just a rectangular wall on one side only.  It might be an over-the-head skin, or it might be just  facemark,  but either way the silicone will be inside a mould that goes all the way around.  It may not be so easy to flex the silicone off screws on several sides if the silicone is narrower just below the screw head.

So your basic idea looks right.  A core to pour the hollow skin, and a fibreglass underskull  matching the shape of the core that will hold the mechanisms.   I've only done something like this for larger hand puppet or radio control heads,  my stop motion heads are smaller and simpler with the silicone or foam latex cast around a head block with wires for moving the jaw and eyebrows that get embedded in the silicone/latex.  I'd like to see how this goes for you.

All great points Nick. Everything works in theory until you try it! I’m gathering all the materials in the coming days, we’ll see how I get on. Lots of things to figure out. I’m very appreciative of this resource. You guys are lifesavers. I’m sure I’ll have a thousand questions going forward. 

Cheers,

Steven


StopmoNick said:

Cosgrove Hall did something like the for their foam latex puppet heads for Wind In The Willows.  Since it was a TV series the foam would get a lot of wear and need to be replaced more often than the armature, so they made replaceable skins that slipped over the underskull and mechanisms.  They had plaster (or was it resin?) cores that duplicated the underskulls, except there was a simple bump where the toggles to move the skin would stick out, rather than undercutting behind the toggle like yours do around screws with mushroom heads.  They were just ball and socket toggles to move the skin, rather than complex geared or cable mechanisms, but there was a similar need to create a hollow on the inside of the skin where the toggle would locate itself.

The only bit I question is having screws where the head locks in to the silicone, possibly filling clay in around the threaded part near the head would create a hollow where the screw fits in, but isn't so much locked in.  Yes, the silicone will flex and come off, and in your simple diagram that looks pretty straight forward, but the actual shapes are more complex, and it's not just a rectangular wall on one side only.  It might be an over-the-head skin, or it might be just  facemark,  but either way the silicone will be inside a mould that goes all the way around.  It may not be so easy to flex the silicone off screws on several sides if the silicone is narrower just below the screw head.

So your basic idea looks right.  A core to pour the hollow skin, and a fibreglass underskull  matching the shape of the core that will hold the mechanisms.   I've only done something like this for larger hand puppet or radio control heads,  my stop motion heads are smaller and simpler with the silicone or foam latex cast around a head block with wires for moving the jaw and eyebrows that get embedded in the silicone/latex.  I'd like to see how this goes for you.

when I cast the silicone i first apply a harder durometer silicone around the screw heads to help the skin stay on

That's clever! I'll give that a try, thanks for the info!

Greyguy said:

when I cast the silicone i first apply a harder durometer silicone around the screw heads to help the skin stay on

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