we use polyester fiber in our wheels (mainly because we have it) its a fairly loose mesh and we have had no problems with air bubbles.
wet the fabric out first (put it on a bit of something smooth, pour some urthane over it and rub it with a (gloved) finger) then wrap it around the hub.
The reason we use the fabric is because the wheel has a lot of leverage over the hub and we have seen some hubs actually spin inside the wheel, we were using @25mm hex bar so thats not an easy achievement.

If you can put a slight taper on your mould you shouldn't need a 3 part mould, ours are one part (with a locating "pin" thats about 47 parts). though on the mill its probably easier to do it like that, Be careful not to make a non round wheel if you make a round thing then cut it.

Make sure your fiber isn't going to go near the surface of the wheel or you will have no traction.

I believe we pay about $60 for a 1kg kit.

In related news we are looking at doing another batch of wheels.
"new and improved", red wheel size and made with spokes of hard urithane for lightness and with a funky shape for shock absorption, all coated in a delicious layer of thick creamy extra squishy urithane for traction.

oh btw viscosity is a bit thicker than water from what i remember depending on temperature, it can get down to around honey.
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Thanks for the great advice Jake! I don't want to open the can yet, but this urethane is wierd stuff; it is the size of a 1/2 liter paint tin, yet if feels almost empty compared to a normal paint tin . It doesn't seem to be shaking around in the can either..

I would rather make a one or two piece mould but doing the taper on a mill would take a rotary table, which I don't have. It sounds like I need to make the mould watertight before I pour any wheels, which is where the wax release agent comes in - something with a bit of body could help seal up the joints in the mould. Failing that, I might try a really thin rubber gasket.

I machined some hubs for extra grip:





The grooves were made with a roughing cutter to get the serrated look. I will roughen the rims up further, wrap a few turns of kevlar over the grooves and that should stop the tread seperating from the hub.

I'm having trouble machining the bottom of the UMHW mould smooth enough to be leakproof; I wonder if giving it a really rough surface and then painting it with a thin coat of urethane before slapping on the bottom plate (well coated in release agent!) will form a gasket?
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one of the parts is really thick the other is like water. We wound up putting the thick one on an iron to warm it up till it could be poured. Water tight is the way to go, you can use plasticine to fill any gaps you might have. (and to stick on any leaks that form) our stuff has a pot life of about 5 minutes to plan and reherse your steps.

if you really want to stick the urithane to the wheels then do the first stage of anodising.
all you need is a bucket, some battery acid and a 12v battery pack (eg a car battery)

just don't do the hot water stage then do your urithane pour.

wrt kevlar I don't know if the urithane will stick to it if its fiberglassing kevlar, they put all sorts of magic coatings on these things. I'll get dad to have a look at this post, he is the expert on it all. Also you probably don't want to make it too tight around the hub or it may cause air bubbles under it in the voids you cut and weaken it, All the fiber does is stop the wheel from expanding to the point where it can rotate on the hub.
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Interesting... I had to open the urethane tin for a look - the base part is completely clear and is more like syrup than honey, it flows but not real fast. The hardener is black and thicker. The pot life is 35 minutes at room temp (25c) and a full cure time of several days. I don't like my chances of pouring urethane in only 5 minutes - 35 sounds much better. I know the Flexane brand is available elsewhere, so I will try to get a bigger pack from the distributor and avoid RS Overcharge.

I was going to use the evil aluminium cleaning solution - it is about 3/4 Sulphuric acid with another agent that really eats into ali at room temperature - perhaps I can use that as an anodising bath for an even more porous surface.

I was definitely going to wind the kevlar on loosly. I was also thinking of tying a few small loops into it for the urethane to grip. The thread is just under 1mm diameter and it doesn't mention anything about fuberglassing in the notes. I will drop a few turns into whatever is left in the pot for a strength test. I will have about 60 metres if you want to try some.

For leakproofing the bottom of the mould, I managed to get a good & smooth cut on the UMHW and I will sandwich a thin rubber sheet between the mould body and the polycarb backing plate. The plasticine idea is great, I will find some or use blutack.

The moulds are on hold until the final supplies arrive - about a week. In the meantime, it's wiring and motor mods.
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Gotta love McMaster! The parts I need to finish the moulds are almost here; they are sure to arrive in time for the weekend

Today, the power wiring was finished and small and boring parts for the wheel assemblies (let's call them Pods, OK?) were fabricated. The power switch has changed position slightly to shorten the motor leads. The motor's direction can be reversed by swapping the leads around and everything will transfer to the Ti frame with no alterations.





The motor pods are basically two vertical plates with the motor sandwiched between them. I made some aluminium spacers to between the motor and the Ti, plus a UMHW motor support:



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Sounds like its going good cant wait till its done so I can see it in action.
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looks like id would strengthen that frame up a ton if you made that front ali square out of one piece
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Scissorhands is really starting to take shape; there is a chance it could be going at the next event if the waterjetting gets done quickly.

@ Glen: Hmm, sounds like an SS2 motor?! The wheel pods are a bit of a hack - they save weight but are over-complicated. Perhaps the next version will have something simpler.

The extra parts for the wheel moulds arrived today . The kevlar cord looks like a winner; very stiff and not at all slippery. The polyester mesh isn't so good; it is very smooth & shiny so nothing much will stick ot it. It is extremely rigid, so I can probably cut the bulk out of the belt and just leave a skeleton to hold the kevlar in place. On the other hand, I might be able to use the kevlar by itself - its like wire!
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Progress:

The wheel moulds are really looking good! All the parts arrived yesterday and I fabricated the first mould tonight:





In the exploded view, you can see the locating pins that keep everything aligned. in the finished mould, there will be a thin gasket between the body and the backing plate to seal it. Boring the hole thru the mould body was easier than expected; I hogged out most of the plastic with a large wood drill and finished the last few mm with the boring head on the lowest possible speed. The finish is pretty good, with small grooves like the surface of a vinyl record (remember them, kids?)





The split in the mould body is a very good fit and a little wax squeezed into the gap should prevent any leaks there. The next step is to attach the backing plate and fill the mould with water for a leak test.
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Nope whats vinyl
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A journey of a million miles begins with a single step followed by a hell of a lot of other steps so get walking

just spoke to dad, he suggested breaking the edge on your milled out sections, the sharp corner there might well cut the urethane. Its difficult to pour the stuff to be level with a surface too, so its handy to have some extra room over the top of the part you want to make for "wiggle"
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Um, not quite sure I understand that - the top circular edge of the mould? The volume of the mould is so small that I am wondering if I could use a syringe to 'inject' the urethane around the hub - it could be way cleaner and more precise than pouring. It probably depends on how thick the mixed urethane is and whether I can get more 50cc syringes cheaply.

I don't know how they do it, but those Whyachi wheels are poured flush with the top of the hub and mould and are very neat.
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I think he's talking about the hubs, they do look like they could slice.

my rough recollection i think they look like they are molded on all sides?

or just be very accurate ;-> either way.
They probably have done it a few times too which helps.
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Ahh, I get it now; I was looking at the UMHW plastic & thinking "What's going to cut the tread on a smooth cyclinder?" I can round off the edges of the slots a little to reduce the chance of tearing.

The Whyachi wheels look like they have been injection moulded but really they are just poured very carefully. The tread thickness at the rims is only 7mm so I should be able to pour the urethane quite accurately
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