nah, I've always done such silly things
Just now they'll be used to destroy robots
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The Engine Whisperer - fixer of things

that sounds sweet as all hell.

one thing though, did you get the fire extinguishers from out the front of sims metal at st marys? stupid question but i was going to swipe a nice extinguisher like that out the front of sims and when i went back to grab it, it was gone :p

hmmmm steering, flipper.. wonder where the inspiration came from good luck with it, a new bot in NSW is a good one after all hehe
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

hehe thanks

nah I had those extinguishers lying around at home for years in case I wanted a pressure tank for something
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The Engine Whisperer - fixer of things

Well, I've now rebuilt two of the smaller rams, possibly to be used for the flipper.
I drilled out the air feed and exit holes so the rams can operate much faster, and cleaned all the old gunk out - to be replaced with new gunk!

I also pulled apart a dual solenoid valve from a gas stove / oven, which I think I might be able to use to control the air flow.

The valves give about 8mm diameter of flow, and they're setup as two valves in series as a double safety thing for the gas supply. By adding another fitting in the middle I end up with an "in" solenoid to fire the ram, and an "out" solenoid to empty it again, all in one pretty light alloy casing.

The actual solenoids are 110v, but the coil sections are removable so I can wind my own and fit them to the casing very easily to get 12v operation.

If these can take the pressure they should flow very well, and will make controlling the ram very simple.
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The Engine Whisperer - fixer of things

One thing I thought of using for high flow electric air valves is washing machine water valves. A lot of the older machines had valves that look like they take the same coil as a common type of automotive LPS petrol lock off valve.
A LPG gas valve is a cheap and plentiful part but the flow is not very good and they tend to be very heavy.
The washing machine ones are mainly plastic.
Ballistic as Andrew knows uses auto air con valves.

yeah I was wondering about washing machine valves. As long as they handle the pressure they should work ok, and they'd flow quite a lot of air.

I'm going to have to find out where the nearest council clean ups are happening and go on a scavenger mission I think!
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The Engine Whisperer - fixer of things

More photos:

These are the small rams which I might use for a flipper.
They're a 1" bore, and have been modified for much faster action:
http://robowars.org/forum/album_pic.php?pic_id=501
http://robowars.org/forum/album_pic.php?pic_id=502

Solenoid valves from a gas oven:
http://robowars.org/forum/album_pic.php?pic_id=503

The fat ram (the one that squashed a set of bathroom scales):
http://robowars.org/forum/album_pic.php?pic_id=504
http://robowars.org/forum/album_pic.php?pic_id=505
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The Engine Whisperer - fixer of things

I like the look of those mini rams, they look very well constructed and the big ram looks wicked!
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https://www.halfdonethings.com/

yeah they're pretty good.

I just managed to pick up a SodaStream machine for $10 (with 8 drink bottles and the manual ) The CO2 bottle is full too, which is a bonus!

This now gives me an easy source of CO2, which I think is worth trying on the smaller rams for the flipper.
I could even run a regulator on the CO2 bottle to keep the extinguisher tanks at full pressure during a battle. It'd be heavier than a compressor, but can make more pressure and doesn't use battery power.
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The Engine Whisperer - fixer of things

It's very annoying that all the metal shops are closed at the moment!

Still, it's made me think of other ways to build the chassis, using bits and pieces I have lying around.

I picked up some optocouplers today so I can build my isolated FET speed controllers.
I'll end up with some small modular FET boards (which will have the optos and an H-Bridge) and some basic FET switch boards for weapon triggering.
These will plug into my custom decoder board and hopefully give nice reliable control!
I found heaps of 48A MOSFETs at work which will be handy

The other thing I tried was a very basic 12v coil wound onto the gas solenoid valve, which seems to work quite well. I'll need to fine tune it, and make sure it'll open under pressure, but it should be possible.
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The Engine Whisperer - fixer of things

Just out of interest I weighed the small fire extuinguisher on some accurate scales, and it weighs 249g with no pressure in it, and 257g with 120psi of air in it.
Considering that the 8g worth of air will run the ram for a fair few shots if I end up using liquid CO2 even the 250g (of CO2) SodaStream bottle (1.2kg full) should last for quite a while!
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The Engine Whisperer - fixer of things

dont forget in the rules air or any substance like that in numatics is not weighed

so dont worry about the weight of the air or co2 or whatever. everything else is weighed though like tanks etc etc.
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Andrew Welch, Team Unconventional Robotics

well I wasn't too concerned about 8g worth of air, it was just interesting what it weighs

The 250g of CO2 is more of a concern, but I'm aiming well below the weight limit anyway so it shouldn't be a problem.
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The Engine Whisperer - fixer of things

Today the chassis was commenced!

It's all square steel tube, the same as used on ROFLChopter, but will be welded rather than held together with alloy corner pieces (partly for weight saving, partly for strength, and partly because of all the funny angles involved)

At the moment the drive system is looking like it'll be a single 300w scooter motor, with a belt drive pulley on it, driving a wide roller style wheel made out of 4 red wheels. The pulley on the wheel is one I found in some old photocopier bits, which happens to fit the scooter belt.
If that doesn't work out I have a backup plan for a chain drive setup using much larger wheels, but that will be a fair bit heavier.

Power will either come from a couple of 12v NiMh packs, or more likely from a couple of drill packs to begin with. I think the electrical load will be quite small with only one motor, and a very simple drive train.
The pneumatics will be controlled either by servos directly, or by something faster like car central locking actuators (they're also mega cheap).

For the front steering I'll probably start with servos, but they'll have some strain relief so they don't strip gears under high load.
I found some really nice 12v actuators from Silvia air con controls, but they're too slow for what I want (very light and powerful though, with feedback switches, etc)

The main center part of the chassis will be wider than I'd originally planned, which allows for trying out different drive setups, and makes it easier to fit in other weapons.
I now have a plan for a very modular weapon system where I can install either the flipper, a hammer - by swapping the actual weapon and just connecting the ram up to it, or a crusher, which will use the much fatter ram and a different weapon linkage.

I can also use different pressure sources, and will be able to easily install either the CO2 tank, a fire extinguisher tank, or twin extinguishers for more air supply and two separate outputs.

I'm also moving more towards making the front wheel outriggers shorter, which will make the bot easier to flip sideways, but will make it a lot easier for me to make it self righting, which may prove useful
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The Engine Whisperer - fixer of things

ok, now the chassis is mostly done
It would have been finished but I only had a couple of hours to work on it today.

The main triangulated center section is all welded up, which will provide the strength for the pneumatic stuff as well as shielding for all the fragile bits.

It still needs the outrigger parts for the front wheels, but I haven't 100% decided on how they'll be done yet so I'm concentrating on the main mechanical bits.

The frame for the flipper is also done, and slots into the front of the chassis very neatly. I'll need to drill the holes for the pivot rod and make the actual cover plate for the flipper next.

Once the chassis is all together and working I'll do some basic tests of the different ram options to drive the flipper. It'll either be the single long ram, or the two small ones.
I think the small ones won't have enough power running on air, but would probably be ok on CO2. Because of the extra leverage required to get enough flipper movement though I think I'll end up bending my own flipper arm!
The long ram was the original plan, and I'll probably stick with that for now.
That also means that the small rams can be used for self righting if needed - although I have designed the chassis to be invertible if needed. The trick will be sorting out steering while inverted, but even without steering if I could drive into a wall and then use the flipper it should self right.
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The Engine Whisperer - fixer of things