I left the final choice up to Angus, as it's his bot we are basing the design around.

Since I can't make bot parts for a few weeks, I blew all this month's bot budget on a new secret weapon - its death by cuteness:






As you can see from the monitor, she already likes Robowars
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

theres a lolcat in there somewhere
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Mechanical engineers build weapons, civil engineers build targets

Very cute Nick!-Have you named him or her yet!

She is called Moonbeam for reasons that escape me
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Urethane time
I finished off the new, wider wheel molds today and also the custom syringe to inject the plastic:




The wheels will be 40mm wide and each one uses 60ml of urethane, way more than the first batch. Its going to be a challenge to mix and pour 1/4 of a liter before the urethane starts to set, the 4mm tube on the syringe should help...
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

worst case you can use the syringe to induce nightmares in people ;->
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Mechanical engineers build weapons, civil engineers build targets

Good idea, I could replace Jolt's teeth with two slime filled syringes and call it "Lethal Injection"
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Hey I use slime as a key component in my robots! That will just make me stronger!

So I guess I shouldn't use a weapon made from gaffa tape either?


Progress
I am setting up for the urethane pouring; which will either be tonight or tomorrow. Getting every last detail right will make for better wheels and lower stress levels . The urethane stuck to the plastic hubs fairly well last time, but I am still going to use special primer paint to make the urethane stick even better this time.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

More progress
The urethane pouring went amazingly smooth and successful, not a drop spilled and the results look near perfect I will be able to take the wheels out tomorrow for testing, I hope the plasticiser additive gives the right hardness - I am aiming for Shore 45 to 50A

This is the set-up ready to start mixing the plastic. Since I know the volume of the molds and the plastic components are mixed by weight, I have to measure the resin by volume, then do a quick calculation and add the right amount of hardener by weight - its more complicated than it should be but it seems to work




The molds after pouring. I overfilled them slightly and will trim the excess plastic off with a razor for a neat appearance:



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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Progress

The wheels are out of their moulds and look pretty good. They are still a bit soft and should cure to about the right hardness, possibly a tiny bit harder than my old Whyachi wheels.


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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Hey Nick!-You can lengthen the amount of working time in urethanes
by cooling one or both parts in the fridge before use-this slows exothermic
reactions down-youd need to do a test batch to check that it works
with the product youve got, but it seems to work well-you dont
get a huge increase in the work time but you do get some!-Jas.

Working time was great for this batch The enlarged tube on the syringe made a huge difference, although I am going to go for an even larger tube next time. The plasticiser seemed to slow the reaction down and doubled the de-mold time. I plan to add more hardener next time just to keep the process times down.

The wheels seem to be hardening up to full cure and will definitely be a little harder than the Whyachi wheels. they still have amazing grip due to the 40mm width. I like them so much I am going to make another batch right away.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Planning:
I spent the evening setting up to make another batch of hubs and getting parts together for another flame thrower test. The next idea is to try a minature fan-forced blower. I have a box of these high power 40mm fans looking for a use:





They pump a lot of air for a small unit and are actually two fans stacked to form a single unit. I have some tube with a matching diameter to make the body of the burner and the main question is whether to inject liquid gas or vaporised gas and whether to inject it in front of behind the fan. The liquid gas injected thru the fan blades sounds best but testing will tell...

Just had another thought; perhaps this could be combined with a catalytic element like those used in gas soldering irons to make a giant hot air gun? the BTUs of heat output would presumably be the same and it sounds safer .
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

hey nick,
Looking at this a centrifugal blower would probably be better.. We sell ones with a metal surround and metal fins... You could just spray gas into the air in duct and have it blown out, and to ignite it, all you need it some Nichrome 80 wire which is wired to the batery to ignite the gas and away you go... You'll get much better distance than the fan setup you are looking at and on top of that the wire will keep the fire going and its easy to turn on and off, unlike an electric starter.. (as you apply current it glows red hot and as you apply more voltage it gets to near white hot and doesnt blow)

Interested to see how this pans out!