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Polaris - Demon Designs - NSW


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Glen
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Joined: 16 Jun 2004
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Polaris - Demon Designs - NSW

Hello! Quite annoyed by facebooks extortionate method of pay for exposure so back to forum build reports we go.

Placeholder for V1.0 of the build > V1.5 in the 2nd post
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Post Wed May 23, 2018 4:53 pm 
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Glen
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Polaris V1.5

So on the 2nd version - this was a quick rehash of the robot in 3 weeks due to having been flat out with This is fighting robots in China.

The main goals were to improve the reliability of the flipper and also to make it easier to work on. Some parts like installing the bungee cords were an absolute pain! Lastly he needed to be bulked up to the weight limit due to being over 1kg under last time.

Lets get stuck in - here's how it stood after the last Vivid event. The electronics really didn't fit and the wiring snaked between the frame and ram, super exposed and all, so The entire electronics bay got rearranged.



Plasma cut a bunch of mounts for the new arrangement - the part on the left is a bulkhead to stop wiring getting sucked in the drive wheel and mounts the removable power link, the 1.2mm aluminium in the center is the mount for the reciever and drive speed controllers, the L shaped pieces on the right is the new battery bay.



All welded in place. Much better than the awfulness that it replaced Smile not much heavier either.



The flipper controller is just too big to fit in the small electronics area - so that was relocated to the opposite side of the robot with the wiring running around the front, tucked under the buffer tank. Here is the mount for it, a folded piece of 1.2mm aluminium and one of those hobbyking velcro straps clamps it in. Weight is basically nothing!




The PCplus polycarbonate printed (phew) lid mounts shattered so i replaced them with 2mm folded aluminium ones, with countersink rivnuts - one of my new favourite things.



Probably one of the biggest changes was how the bungee attaches to the flipper arm. The last version had rods running between the flipper arms and the bungees were tied to them with a knot, to remove them meant unpicking the knot or unbolting the hook from the base of the robot which in itself is fine but trying to bolt it back on with bungee tension was next to impossible.

This time i made a hook out of 6mm steel plates. Then the bungee cords tied on to a steel eyelet that could be drawn down and placed onto the hook. To remove the cords i just have to pull on the eyelet and unhook. Super easy and it worked great. no torn bungees this event!



My big charger is still in Shanghai so i grabbed one of these tiny ISDT chargers. Decent for $60, and fits in with my desire to make everything lighter, that 23kg luggage allowance disappears quick.



on to the most major change of them all.

Polaris has a thirst for liquid co2. A LARGE ONE. Due to the main tank laying flat and at a higher level than the buffer plus the giant flow rate of the main valve, the liquid decants straight into the buffer and blows out the ram if the robot gets knocked about. Co2 expands something like 10x when going from liquid to gas, so losing a tiny amount drastically decreases the amount of flips the robot can deliver!

First port of call was to test a bunch of theories i had. The first was to use a pneumatic muffler in the tank to try stop the liquid migrating past. the mufflers do stop liquid at atmospheric pressure, but testing showed liquid co2 blows right through it at high pressure, although they do stop filth getting into the pneumatics!

Next test was a pneumatic expansion chamber. A pair of tiny holes in a chamber that cause the liquid to expand going through it. Here's a 3d print cross section of what i was looking to do -



gas would flow in the chamber around the outside, and then pass through the pneumatic muffler, there are 1mm holes on the inlet and outlet. Turns out i had a full pressure 0.8mm orrifice valve that was very similar internally. The problem that arises is this is one neat way to make dry ice due to the joule thomson effect! After only a second or two of liquid flow it would block solid with dry ice, and it takes minutes to thaw out. Basically, doesn't work at all.

The solution is the obvious one. An anti siphon tube in the main tank. Its just a piece of brass tube rolled into a curve, with the end crimped shut and a 1mm hole drilled in the side near the end. This prevents the sloshing of liquid into the system during operation, however if run upside down will ingest liquid. For whatever reason this didn't seem to be much of a problem. Did not see any liquid exit the ram during the event so calling that a win.



While servicing the pneumatics, there was an agressive leak. Seems that all the o rings in my china burket had perished. Not co2 compatible or the o ring slot is badly designed. Something to fix but for the time being i put the spare set in, good as new.



The last port of call on the gas works is extracting some more powers. The distance between the ram and the flipper arm is about 15mm due to a design change midway through the original build i didn't catch, so made up a 13mm spacer to use all the rams travel, the increase in power is really noticable but it also causes more side load on the ram and increases its tendancy to jam up sometimes. I chose to run without it ultimately although it was installed for the rumble and worked okay.

Sub looms finished up, the flip controller sits in the purple PCMAX polycarbonate box to the left.



The weight was actually less than before due to the heavy last minute electronic mounts of v1.0, Time to pack on the pounds with some 3mm steel pontoons. These should prevent being stacked on ones side and also act as some stiffening / spaced armour for the front, where the buffer tank is uncomfortably close to the side panel.

Together they are about 600g.



The remaining weight went into a 5mm aluminium back panel to replace the HDPE one. The pockets were done on my new router as a bit of a test. The design was taken from a lego factory documentary that i was watching while soldering the electronics - a window in one of their buildings looks just like it and I loved the shape - bit weird lol.



Frame all done with the pontoons welded on. Didn't snap a pic but there is a folded sheet metal shelf that spans the upright panels that hold the flipper itself on, just behind the ram. A bunch of LED strip sits there.



Now my robots are nearly always finished just before i leave! no time for paint. But after seeing so many awesome paint jobs and themes at the China event, now is the time to step up. Here the robot is being masked up, and my crappy hand drawn guide haha.



Primer - really neccessary as condensation that drips off the co2 system rusts the frame badly.





Paint all done - complete with his fusion reactor in the middle Smile



Glamour shots!




And at the event. Can't be happier with Polaris' progress and performance. Everything worked spot on really and his flipper power is right up there with the best. Only bad points were the flipper arm takes time to come down as a result of not using a vent valve still only a bleed hole in the ram (next time will have an active valve) and self righting is a bit of a pain, got to time it just right!



Probably won't do much next time aside from intergrate a vent valve and redo the flipper controller on it own PCB instead of a jumble of wiring. A new robot is needed to enhance it further!
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Post Wed May 23, 2018 4:53 pm 
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Cpnwolfe



Joined: 29 May 2012
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Location: Rockhampton/qld


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Looks swish as! the pics dont do it justice!
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Post Thu May 24, 2018 9:31 am 
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Valen
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That's a sexy looking robot, Going to be even better when it doesn't get stuck in the floor Very Happy
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Post Thu May 24, 2018 1:03 pm 
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Philip
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Joined: 18 Jun 2004
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Location: Queensland near Brisbane


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Your drives are impressive. Are you happy with them? Do you think the Banebots gear boxes and brushless motors are worth the extra expense as compared to drills? Have they lasted for a long time?
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Post Wed May 30, 2018 7:08 pm 
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Glen
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Joined: 16 Jun 2004
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Yes definitely worth it in all regard. Polaris, Glitch and obliterator all share the same setup and no failures between any of them. They are pricey but worth it to me! And brushless controllers like the red brick 70 with the simonK flash are cheaper than the brushed equivalent now.
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Post Wed May 30, 2018 8:18 pm 
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