Ok first a bit of the back story for this question. I am working on makeing a mascot head for a friends school. Normally I would just free form this out of foam but I wanted to play with modeling the head out of clay then pulling a pattern off of that using tape.  Here are a couple shots of the clay head and then the foam prototype. The prototype is the pattern I pulled increase by 150% and then made with 1/4 inch foam.  The prototype is perhaps about half the size it needs to be in the end product.



We are planing on using a bicycle helmet on the inside of the final head. the helmet needs to fit inside the head so the performer can look out the mouth of the mascot.  Here is my question or what I am trying to figure out. I can measure the outer circumference of helmet and then the outer circumference of the prototype where I figure the bottom of the helmet should be in order to try and figure out how much more I need to increase the pattern but I am not sure how to take into consideration the 1/4 thickness of the foam.  Are you following me yet?  I really need the inner circumference of the prototype but can't really get inside there to measure accurately.  I am pretty sure that I can't just subtract a 1/4 inch from my measurement or do I? I was always so bad at math.

Perhaps if I state the problem in a different way. If I have an hollow ball that has a 1/4 inch wall and measure the outer circumference how can I find the inner circumference?

BTW: Once I finish this project I want to do another one which I'll detail and do a tutorial on the process of making a clay model you can pattern off of.  There are a couple things about this model that would not really work as a hand puppet but the increase of 150% from my original to prototype is just about right for a hand puppet. Figured it would be a great way to get some shapes and patterns for things that folks are always asking about.

Another quick note. The images in the above are hosted on Dropbox.  It is another one of those services like Flicker. The cool thing about it is that I can take pictures with my camera and then with their app I can send them right to Dropbox.  There is also an app for your computer that lets you access the files and share them.  It is a pretty sweet set up and basic service is free. http://db.tt/8HJP5Dye

Shawn,
   What is the circumference of the helmet?  Foam head? I think I might know, but I want to check the figures.

Julie

You would ask a question I don't have the answer to yet.   Have not gotten the helmet yet... was just trying to be prepared. Hope to get the helmet this next week. I am kind of tag teaming this project with another person and they where going to pick up the helmet.

I do have the measurement on the prototype of course. I guess it really is not a full circumference because I am measuring from the back of the mouth around the back of the head to the back of the mouth on the other side. That is 22 1/2 inches.  I am going to have to kind of eyeball the measurement I think on the helmet most likely because I want the front of the helmet to come to just about the back of the mouth or set back just a bit maybe.

So, do you think you want the brim/edge of the helmet to fit at the bottom edge of the head or would it sit deeper into the head?

Julie

I am thinking that the brim or bottom edge would fit right along the line you see through the cheek. Does that make sense? The front front or brim of the helmet would fall right behind the back part of the mouth. the mouth itself is going to have screen in it. Still playing things a bit by ear. I think the farther forward I can get the face in mascot head the more visibility the puppeteer will have.

The scale is kind of off on this but maybe this gives you an idea of where I am going.

You know the more I look at my mock up I am wondering if I am going to end up with the performers head further back in the puppet head. hmmm... I may end up having to cut the mouth a bit further back to open it up some. BTW this is the image of the mascot I am working from that they have on the wall of their gym.  I am going to have to add on top of my base structure to really get the angry look of their mascot but that does not really worry me to much.

I'm going to chime in, but not with math...since I am not that hot in that department.

I just wanted to say that

A) The foam looks great so far. I am super jealous of your talent and

B) Once you get the helmet, I would also double check the height (i.e. how far down is it going to go to meet the fabric for the rest of the costume, covers the chin, etc.) once you figure out the size you need to fit the helmet, just to keep it in mind when you are doing your build. I did a cosplay build for someone once, and I was off by one inch on the height, and had to go back and start again. (I didn't get all the way through, since I had the forethought to have them try it on first.)

Anyway, please post pics when you are done. Can't wait to see how it turns out!

I'm probably complicating things, but here goes the math.


Measurements

1st. Measure from to top front lip area to the brace middle of the head.  Think about it as a straight line.  Let's assume for this example the measurement is 11.25"  Subtract .25 for the thickness of the foam at the back only since it doesn't look like there will be foam in the front. Diameter 11" divide this by 2 that will give you the radius, 5.5"

2nd. Looking down from the top of the head measure across with width where you believe the placement of the brim will occur. Let's assume for this example 8.5", subtract .5 which is .25 for each side..8" divide by two, 4" radius.

This the the formula

2 X 3.14 X square root (radius of longest measurement squared + radius of shortest measurement squared) divided by 2

Let's plug in e figures

5.5 squared is 5.5 x 5.5=30.25
4 squared is 4 X 4=16

2 X 3.14 X square root (30.25 + 16) divided by 2

6.28  X sq root (46.25)/2

6.28 X sq root 23.13. This is a good websites for sq root http://www.math.com/students/calculators/source/square-root.htm

6.28 X 4.81

30.21 is the inner circumference.

Use the same formula to calculate the outer circumference of the helmet.  Let's assume for this example e circumference is 42.26

Divide 42.26 which is the number you want to increase to by 30.21 which is what you have.  That is 1.40.  Multiply by 100 and you get 140% is what you need to increase the pattern by.

I agree with Lola you might need to think about the height of he skull, but the increase might take care of that.

Julie

If you get the numbers and what me to check them I'd be happy to.  Not guaranteeing, it's been a long while since I've had to use this stuff.  See now our parents told us we'd use math for something important. Do you think this is what they had in mind. LOL

Julie

Ok now my head really hurts.   I'll have to really look at it again once I have all the parts in the same room.

Yep the whole fit to the performer is going to be a pain. For one thing this is for a school and who knows which student is going to end up wearing it. We are already figuring on that for the body part of the costume but that is always a bit difficult to plan for with a mascot head. It is for a high school so you could end up with a freshman to a senior. If something is to big you can always pad out the inside of the helmet to help make a snug fit. I might need to look at some way to secure different helmets inside depending on the person wearing it.

Thanks for the input! I'll keep you all updated as I move forward.

Looking forward to seeing the process.

Julie

I have a few tips that might help you out with this since I've a built a few mascot (fursuits). 

It appears that the head is not going to be one of those typical huge mascot heads which will make things much easier for you.  My first suggestion would be to reconsider using a bicycle helmet as the base for a couple of reasons 1) they are notoriously hard to keep firmly on the head when the performer is very active. 2) they can limit the shape and placement of the mascot eyes and mouth which can lead to vision and ventilation issues for the performer.

My recommendation would be to build the head "Balaclava" style which will be formfitting but still flexible enough for a  reasonable number of different head sizes to use it.  To build this you cover a model with sheet foam and build out from there.  You can use your clay technique (which I use BTW).  A great item to have is a full size head armature, you can get them here:  http://www.monstermakers.com/product/deluxe-full-head-sculpting-armature-life-size.html.

Make sure you figure in putting a fan in the head for ventilation! It can get over 120 degrees inside a suit head in a big hurry.

I recommend checking out the LiveJournal Fursuit group,  there's a ton of information there and plenty of people willing to help out.   http://fursuit.livejournal.com/

Here's an image of one my costumes:



Good luck with your mascot project, looking forward to seeing how it turns out.

For myself, I'm actually doing mostly puppets now because costumes are very time consuming to build.

Cheers!

Shunaka
www.furville.com