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Robowars Sportsman Cup 2016 - 10/11 Dec - QLD
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pilleya



Joined: 31 Mar 2016
Posts: 91
Location: Sydney


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This seems like a reasonably simple way of controlling butane gas flow:

https://www.youtube.com/watch?v=F6ylQJUOM6I

They are pretty cheap as well: http://www.ebay.com.au/itm/like/152179341613?lpid=107&chn=ps

Although the flame probably needs to be a lot bigger to be effective.

I'm having a look at some camping Butane gas canisters, they seem a really durable and pretty safe way of holding the gas. Although they are expensive at about $10 for a 100 gram can. They also aren't the best shape for putting in a bot.

http://www.globetrekker.com.au/optimus-gas-100g-eu-butane-propane?gclid=Cj0KEQjwg8i_BRCT9dHt5ZSGi90BEiQAItdjpK9Etdtq57uj2SlZUaExiqmFZVRQd-3LfUizRwVTCzgaApkG8P8HAQ

I've just noticed that they are a mix of 70% butane and 30% propane so I'm not sure if it is legal, but it certainly seems saver than some of the other options as they have a really good screw thread on the cap of the can as well.

I was just thinking of making a custom fitting that goes from the canister to a 12v solenoid, and then a electric ignition does that seem reasonable?

Post Mon Oct 03, 2016 5:26 pm 
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Don
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Joined: 21 Feb 2010
Posts: 355
Location: Gladstone, Queesland


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Excellent, great bit of research being done here its good to see,
I have not hacked into one of those automatic airfreshiners myself before but I would say that it might not be a good item to use due to the fact it probably doesnt have a thread or any other useable connections,strong enough for a combat robot and would stick to a small 12v solinode valve,somthing like this: http://www.ebay.com.au/itm/131867571833
or I belive arron has mentioned a nitrous valve for a car before.

the can size probably isnt that small either because you also need a main active weapon so its not like you will be flaming non stop for the maximum fight time of 3mins and 1 can could possibly last more then one match

Post Mon Oct 03, 2016 5:48 pm 
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miles&Jules
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Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD


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Might be a good idea to probably put the date of this event as part of the title of this thread- also no mention of registration in this thread-might help with people who only check here💥
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www.mulesfilm.com.au
www.wombokforest.com.au

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Post Tue Oct 04, 2016 8:50 am 
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marto
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Joined: 08 Jul 2004
Posts: 5459
Location: Brisbane, QLD


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Updated First post.

Robowars is coming to Gladstone on the 10th & 11th of December and we are looking for new builders to take part in our next competition.

Registration is open on:
http://www.buildersdb.com/

More info on Facebook:
https://www.facebook.com/events/153628805089585/

The event will be for the sportsman class in the SPARC Rules.
http://www.robowars.com.au/wp-content/uploads/2016/07/SPARC_RobowarsRules_v1.0.pdf

Tickets will be on sake at the door with the exact time and Venue still TBC:

Adults $10
Kids (under 16 free)
Sorry no EFTPOS

This event is brought to you by, Queensland robotic sports club (QRSC).
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Post Sat Oct 08, 2016 6:39 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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How much butane in grams?

I'm considering putting a flamethrower on the Slaying Mantis and bringing it to Gladstone, but I'm wondering if there is a definitive ruling on how many grams of butane is allowed? The rules say 4 fl oz which is a volume measurement, but butane and propane are sold in Australia in canisters labelled in grams, which is a mass measurement.

To convert between the two you need to know the density of the substance which is complicated in this case because the canisters are pressurised - enough pressure to keep the contents in liquid phase at room temp. Some of the numbers given so far in this thread differ wildly from my own research on the topic, but I'm no chemist.

I went here:http://encyclopedia.airliquide.com/Encyclopedia.asp, looked up isobutane and got the density of liquid butane as:
Liquid density (1.013 bar at boiling point - around 0C for butane) : 593.821 kg/m3

At this density, 4 fl oz works out to 70g, but the liquid butane in question is neither at 1.013bar nor at boiling point, so I don't know whether this conversion is truely valid. Perhaps someone else can present more convincing working?

If 70g is the max allowed then the 60g Tradeflame butane refill from Bunnings looks like a good option, but I have seen people here quoting numbers north of 100g, so it'd be good to see how you worked that out.

Post Mon Oct 10, 2016 7:59 pm 
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Don
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Joined: 21 Feb 2010
Posts: 355
Location: Gladstone, Queesland


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hello, thats exciting to hear.
To be honest Iam less concerned about the overall amount of gas, as Iam with the overall safety of the system, do you have any other details of what you want to consturct?

Post Mon Oct 10, 2016 8:43 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Hey Don. The Slaying Mantis has had a major refit since the nationals. Based on what i learnt there, I have focussed on making the lifter ultra-reliable and will drop the saw and possibly also the claw to do so within weight. It now runs off a heavily geared ATV starter motor.

I have been researching the flame option for two potential cases:
1) put a torch on the Mantis for some lift and cook action
2) put a torch on the second robot I've been designing

Option 2 is more likely. My second design has an internal structure CNC cut from 10mm 6061-T6 hardened Aluminium plate (assuming my machine can cut this at a reasonable feedrate) and will have an outside skin made from a stainless steel mixing bowl. If I put a flame on it the gas canister will be encased under several layers of 10mm aluminium. I was planning on using the valve in the 60g butane refill canister to control gas flow and actuating it by moving the whole canister with a servo with the canister's outlet stuck in an immovable outlet tube. Ignition would come from a spark gap.

Post Mon Oct 10, 2016 9:17 pm 
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Don
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Joined: 21 Feb 2010
Posts: 355
Location: Gladstone, Queesland


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is the second bot part of mantis like a clusterbot or is it a separate entry?

Post Mon Oct 10, 2016 9:36 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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From page one "A SERVO ON A CAN WILL NOT BE ACCEPTED!"

Sorry to be a bastard, but Don is right to say that; pushing a can with a servo has so many ways to fail in the on position its just not safe. For the fairly low flow rate from a small gas can, you could use a small and fairly cheap nitrous oxide injector valve. They are operated from 12 volts and are rated for more than enough pressure.

An electronic BBQ lighter from eBay makes an excellent spark gap igniter. They run off a 1.5V AA battery and if you increase that to a C cell, you can probably simplify things and just leave it running for the full 3 minute match.
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Post Mon Oct 10, 2016 9:38 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Second entry. And thanks for pointing out the no servos on cans rule Nick. I had read that long ago before I'd really thought about it.

I've found the 1.5V BBQ lighters. You can buy a similar thing in the BBQ aisle at Bunnings for replacing the spark in your BBQ (a battery powered one, not a piezo). Has anybody tried running those directly off a 3S LiPo? I pulled one apart and they have no active components apart from two transistors and a Zener. Basically a simple relaxation oscillator driving a transformer. Haven't tried it yet but I'm guessing it will work directly off the LiPo or maybe the BEC output from an ESC with little or no modification. That way you avoid an extra battery.

Post Mon Oct 10, 2016 9:49 pm 
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Don
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Joined: 21 Feb 2010
Posts: 355
Location: Gladstone, Queesland


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also flame throwers are not classed as an 'active weapon ', and to be a sportsman you will need one, there no reason a bec wouldnt work but most of them output 5 to 6volts. Also I myself have never been able to find any at bunnings other then the pezo manual clicking ones.

Post Tue Oct 11, 2016 5:55 am 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Here is the Bunnings sparker:
https://www.bunnings.com.au/gasmate-2-point-electronic-ignition-kit_p3170717

Understood about the active weapon. If I wind up building the second design it would also have a flipper or grabber.

Post Tue Oct 11, 2016 6:33 am 
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Don
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Joined: 21 Feb 2010
Posts: 355
Location: Gladstone, Queesland


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awesome thanks for that, they never use to have them as a standard item. I look foward to seeing your design.

Post Tue Oct 11, 2016 9:23 am 
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miles&Jules
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Joined: 19 May 2010
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Location: ipswich QLD


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So how is everyones flame throwers going i havent seen any backyard pyro videos yet😄
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www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

Post Thu Oct 27, 2016 10:26 pm 
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miles&Jules
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Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD


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We are looking at booking accomodation soon for m&j does anyone know yet where event is? And nearest motel? And are we all going to try and stay at the same motel BattleBots style? Any suggestions? We are thinking of driving up maybe at this stage. J&m
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www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

Post Fri Oct 28, 2016 2:46 pm 
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