Tech How to make your own shift knob

Here we go for the third time I hope the servers are up and going. Heres how to put me out of buisness. There are many ways to do this this is the easiest way I have found so far.First we take out original in this case its my shrunken head and since were pouring it from the bottom any thing that hangs down will get air bubbles so we need to make vents. I just make some clay into strings on this one the ear lobes and pony tail will need vents. Since I already made the vent in the pony tail when I made the original all I have to deal with is the ear lobes just make a string that goes from the ear lobe to the surface it is sitting on.

Next we find a container on this one I stole my girlfriend's big gulp and cut off the bottom. You dont want it to much bigger than the original since this stuff is 20 bucks a pop and I'm a cheap bastard.

Now we tape the bottom this will end up being the top when your done. The masking tape also holds the original down since I put foil as the inside of my original it is boyant and will float to the top wich is a bad thing. I learned this the hard way.

Center it and stick it down making sure your air vents are touching the tape.

Next I like to find out how much mold material to make by pouring in some water to cover it and then dump it into a measuring cup. After it dries out we mix our material I use Smoooth-On products OOMOO 30 it's a silicone rubber mold, and you mix it one to one.There are many others that work just as well. Mix it in a plastic bowl it will clean up better and use an old measuring cup because you will never get it clean again.

Now pour it in the cup. Pour it to the side you will be less likley to get air bubbles on the bottom. Treat it like a beer.

Now since you've made a big mess clean up because you need to wait about 5 hours before you can demold. Once dry remove the tape and the cup. Here you can see the three air vents I made around the large hole.

On mine I needed to cut a slit in it from the back of the neck to the tip of the pony tail to get the master to pull out. You may need to do more it depends on the shape of the knob. Carefully pull the mold away from the master the best you can then yank it out. The mold is very rubery so you should'nt have to make very many cuts in it.

Now you have a mold put a rubber band around it this will hold all the slits you made in it closed mix your resin up and pour it in. Remove after it hardens the same way you took out the original. See easy as pie. If your original has has any negative space in it (holes) or deep undercuts you will need to make a two peice mold wich is a whole different can of worms and that is a tech for another day. Any questions.

 

COOL! I'm doing this.

Questions..

What is the original made of (clay?)
What resin do you use to cast?
Is the mold reusable for a few?

 

Imake the original out of super sculpy you can get it at Michaels and art place usualy have it.

For the resin I use Smooth-On products Smooth-Cast 305 its a medium. It sets up in about 30 minutes the quicker setting stuff you'll end up with more bubbles and thats a bad thing.

The less intricate the detail the more uses you'll get out of it My day of the dead one I've probably made 40 of em and its still going Now the shrunken head one I've already had some issues and all I got out of it was 6 of em. Buy some mold release youll get alot more use.

There is also brush on molds that are near indistructable but you have to make a secondary shell that goes around it but once you take off the outer shell you can flip the rubber mold inside out and pop it out that way. There are a million ways to do this this is just the way I started out with I'm still learning.

 

Post deleted by leadsleadolds

 

Great post, man- thanks! I'm already thinking of stuff I want to make now...

 

This is a great post, so I'm tossing it BTTT...

Do you use a release agent?

 

Incredible post! Keep it coming! I can't wait for the 2 piece mold.

CaddyRat

 

For anyone interested .... Michaels has Sculpy on sale for $1 right now. I bought a few chunks today to try my hand at making some tiki necklace charms & a shift knob for my wagon. WWS

 

You can use 100% silicone caulk to make your molds. It's way cheaper and is nearly indestructible. It withstands temps. to 600 degrees so you can cast with pewter if you want. I have made molds like this for 20 years and it works great.

 

thanks for the tech.

can you buy Smooth-on products at Micheal's too?

 

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You can use 100% silicone caulk to make your molds.

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Where did you get it? I made shift knobs a couple years ago, from the smae stuff posted here...it really is cool! The hardest part is making a nicely sculpted original. Definitely think "simple" for your first designs...you'll get better beginner results and be more likely to try it again. I did 3 designs, each one a bit more in depth than the one before it. I even had the Barons over for "Make Your Own Shift Knob Day" and they had a blast. Fun for the whole family.

 

I get my smooth-on stuff at reynolds advanced materials there local but I think they got a website. Also dentist supply places also have it or similar products.

I would imagine using silicone you would have a problem with air bubbles

 

Maybe I missed it but, where do you get the 2 part silicone for the mold? Thanks.

-Jeff

 

I have been wanting to make a shifter knob out of resin. Thanks for this post..
I seen this in Dick Blick would something like this work??
http://www.dickblick.com/zz349/36/products.asp?param=0&ig_id=7330

 

It may work but heres a link to where I get mine. mold & resin people.

 

Tech-o-matic

 

The only thing that is confusing to me is the vents. Could we explain on a special ed type of level for me?

 

If you brush on or spoon on a coat before pouring it in you have less problems with air buubles on the surface as you have allready coated it well

 

I just got my shrunken head shift knob today! WAs wondering how it was made. Maybe that's mine getting cast! This is cooler than the pictures show!

thank you LSO!



jerry

 

Here's a web site with a lot of information about using common bathroom silicone for moulds and how to get it to set properly for thick applications ...

http://forums2.gardenweb.com/forums/load/hypertufa/msg1217385422593.html

 

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I would imagine using silicone you would have a problem with air bubbles

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If you put it on in thin coats, 1/8" or so, there is very little problem with air bubbles. you just have to take your time. It is important to let each coat cure before applying the next one. You can use diluted dishwashing soap to keep it from sticking to your application tool (I usually just use my finger). I use it to make molds on very detailed sculpture and have very few problems with it.

 

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Where did you get it?

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Walmart

 

Roothawg because Im pouing the liquid in from where the neck is on this one to make the knobs air would get trapped in the ear lobes and the pony tail, so all I'm doing is giving it an escape route by putting strings of clay for it to the top of the mold. Which while you are pouring the mold it is the bottom. Clear as mudd right.

 

I know you can bake the sculpy to make it hard, do you do that? I would think it would help then you could make a new mold from the same original.

 

I tried the silicone caulk method described in the website above. It works great, but it isn't overly pourable, and should probably be vacummed to get all the air out.

-Jeff

 

Yes I do bake it most the time you can use it again but still sometimes they break pulling em out.

 

Could you coat the original in vaseline or some other lubricant to get it out of the mold easier?

How heat resistant is that sculpy stuff, I have a friend who could make a mold for casting aluminum or other metals, would this stuff work (I dont know how they make the mold but I figure intense heat is involved).

Thanks, rjb

 

Theres acouple ways to do what your thinking lost wax is an easy way. You could could use the mold I show here and cast one out of wax. Burry it in the apropriate sand and the hot metal burns away the wax and leaves you with a metal version of it. Not the best way for doing multiples but works great for a single. In the tech section these a post on casting aluminum that might help you.

 

what about the vaseline, do you know if the oomoo would react with it or something?

 

might have to try my hand at this one.

good tech,

Geno