DIY Halo Helmet

[riley876]

Working towards making an Ice Halo clone,  but with a foam that I know is up to the task.  Trying to cast a single piece of foam in one hit.

First attempt in expanding polyurethane foam, straight after being cut from the mould:


I've made it significantly thicker in the rear (35mm) vs the front (25mm),  since the front is probably lower risk than the rear. Fit is great, it's tight, but elastic enough so that it's really quite snug.   Will be covered in faux fur,  or camo fabric or something.   Looks about as silly as Ice Halos always look.  *shrugs*.

My mould from MDF & Ply (UGLY but functional):


Used a 30kg water bottle sitting on top of the mould to constrain the foam, whilst it was expanding to increase it's density.  Not convinced it constrained it sufficiently,  not like you can get by squirting into a sealed container.   Going to try using foam straight from the freezer next time.  Needs to be drop tested to check the density (and therefore another made it it's place...)

[riley876]

Weight is 30 grams.  I expect any fabric covering would easily double that.

[riley876]

Covered in faux "rat" fur:



Needs a little loop added to hook under my ponytail, so there's no way it can fly off in combat.   Though it's tight enough that I doubt it will.   But otherwise good to go.

Finished weight: 62g  (vs about 400g for a "real" helmet)

[Live2Sk8]

That looks really great!  I admire your ability to try making things yourself.  And good idea on the ponytail loop.

[riley876]

In case anyone is tempted to follow in my footsteps.

I've been experimenting with 2-part polyurethane foam.   

Previously I've been using the 1 part aerosol can variety.   The results have been marginally OK, but it's horrible to work with.  It's messy, sticky (i.e. doesn't flow),  hard to get voidless pours etc.   Also it expands too much, leaving a foam that's a little too sparse.   So therefore needs a constrained (i.e. nearly airtight) mould to get a decent density.

In contrast the 2 part polyurethane pours and sets like a dream.  Great density even unconstrained.   Great internal structure.

But I've found a major problem:   Shrinkage.

After a couple of weeks, my 2-part-polyurethance test halos have shrunk to about 2/3 of the cast thickness (and hence are now 50% denser - too dense).   It seems that the blowing agent (the gas that does the foaming, and ends up in the closed cells in the foam) is a flourocarbon with a 23degC (74F) boiling point.   i.e. the heat from the reaction boils this,  hence causing the expansion.   The flaw is that sometime later, once the ambient temp drops below this, it falls below the boiling point, condenses, and therefore shrinks, pulling the foam in with it.   Not helpful!

In contrast, the 1-part-in-an-aerosol can stuff doesn't seem to shrink at all.  I think because the blowing agent in that is butane, which has a 0degC (32F) boiling temp.   It might shrink if left in an ice rink for a long term, but when actually worn, I doubt it would get close to that.

I'm thinking about trying to dissolve butane in the 2-part stuff.   Might need to heat it (before mixing) to boil the existing fluorocarbon blowing agent out, and then freeze it, so I can mix in some liquid butane.   PITA!    Then the question remains as to how well it's foam and set near 0C.

[Query]

I saw a girl using a real "halo". It was bright pink, nicely finished, and looked very fashionable. (For a girl.) Didn't look dorky at all.

Can you make yours look that good? 

Maybe the real ones contain a stretchy fabric on the inside, which helps, both appearance-wise, and in holding it on the head. But you'd need to be able to sew neatly.

[riley876]

LOL, I'm neither a neat person nor a "pink" person.  *gag*

However, what I did do was paint one up in a forest camouflage.   Because you never know when you'll be inline skating in a forest and you need to not be seen.

It was one of the incredible shrinking ones, so I'm not inclined to post a pic.   Will post a pic of its replacement when I get my process sorted out.

So far not one person, not even my coach, has commented on my halos.  So I take this as proof that either it's not silly at all, or else that it's SO silly that no one dares make a comment.   Or else that the camouflage paint job is working so well, that no one has even seen me!

I think fabric on the inside isn't necessary, since in my design the foam IS the structure, it doesn't need fabric holding it together.  The foam against the skin doesn't seem to be irritating and the foam is a little elastic itself, which seems to keep it snug enough.   Long term I wonder if it might stretch and need a bit of packing.  Sucking it and seeing.