Technical feather stuff

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Re: Technical feather stuff

Post by kickboxer » Fri Jul 01, 2011 7:22 pm

yes haz

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MicroGravity100
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Re: Technical feather stuff

Post by MicroGravity100 » Fri Jul 01, 2011 7:25 pm

Yes, but would it be heavy or stand up to spinners?
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Re: Technical feather stuff

Post by kickboxer » Fri Jul 01, 2011 7:29 pm

it isnt that heavy.
and yes if you get the right thckness

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Re: Technical feather stuff

Post by haz » Fri Jul 01, 2011 7:31 pm

i think its something like 2mm steel is the same weight as 8mm hdpe but dont quote me on that, anyway the new murphys law us twice the size of the old and is made out of 12mm hdpe and only weighs 5.7kg

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Re: Technical feather stuff

Post by terminaldamage » Fri Jul 01, 2011 9:56 pm

If you're fighting spinners, 4mm steel is usually sufficient. Yes it can be heavy if used extensively but if you think about the important areas you want to protect and armour them with the thicker stuff, you can then save weight by using the thinner stuff (or alternatives, such as the aforementioned HDPE) on the less exposed areas of your robot.

With regards to pneumatics, it's only dangerous if you don't treat it with respect and don't follow strict safety protocol. If you are aware of, and respect, the power of such systems, then you stand a better chance of avoiding accidents. I've been building and competing with featherweights for a fair few years now but am only recently venturing into pneumatics, so it's a learning curve for me too. If you're confident that you can incorporate a pneumatic flipper into your first build, then go for it. I couldn't give you an overall figure for the cost of the pneumatic parts but it won't be uber-cheap. I'd estimate around £150-£200 for low pressure components.

The ram you linked to would be quite weak for a flipper. One key parameter of pneumatic rams is their bore (the diameter of the inner chamber). The larger the bore, the larger the volume of gas that can enter the chamber to force the piston out, therefore the larger your flipping force will be. For my system, I'm currently looking at cylinders with a bore of approximately 40mm-50mm. The stroke (the length of travel of the piston rod) is something that you can choose based on the physical size of the system rather than the desired force, but one thing to bear in mind is that the longer the stroke, the larger the volume of gas being used each time you fire your piston, so your gas supply will be used up more quickly.

As an example, here's a 50mm bore, 100mm stroke ram on eBay. A bit more expensive than the one you linked to but more likely to produce a better performance:
http://www.ebay.co.uk/itm/PARKER-P1E-T0 ... _603wt_905

If you can make it along to the AWS in Pontefract, I'll be there and will have my featherweights with me so will be happy to chat about any aspects of building these crazy contraptions.
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Re: Technical feather stuff

Post by haz » Fri Jul 01, 2011 10:06 pm

hey, ill bring my excuse for a featherweight along too, steet fight! :lol:

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Re: Technical feather stuff

Post by MicroGravity100 » Sat Jul 02, 2011 6:29 am

LOL, I don't think it'll be ready in time for Maidstone in November, let alone the AWS in two weeks!
Haz, are you sure that street fights are allowed, coz I heard that they were banned for some reason.
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Re: Technical feather stuff

Post by MicroGravity100 » Sat Jul 02, 2011 6:36 am

Oh, and the ram on the page says it's double acting, will that diminish the power?
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Re: Technical feather stuff

Post by haz » Sat Jul 02, 2011 6:51 am

ppffft, rubish, i rebuilt murphys law in 4 days!

not a good example i know :roll:

yeah it will use more gas but i don't know wheater it will be enough to matter.
i kind o ment it as a joke about the steeet fights but if people are up for it then why not? dont see why they are banned, how would "they" know if there was a figh 8)

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Re: Technical feather stuff

Post by MicroGravity100 » Sat Jul 02, 2011 7:51 am

My Grandad is busy most of the time, and I normally only see him a few times a year. He's going to be telling me how to do things because I know nothing and I'm going to do them. Fun, but it'll take a long time.
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Re: Technical feather stuff

Post by Remote-Controlled Dave » Sat Jul 02, 2011 10:42 am

MicroGravity, I think Jamie meant he'll talk to you about it at the AWS, not for you to actually bring your feather along...also, Haz, before you challenge Jamie to a street fight, you might want to know that his feather has a big spinning drum...lol
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Re: Technical feather stuff

Post by terminaldamage » Sat Jul 02, 2011 12:15 pm

Yeah that's what I meant :)
Getting along to an event (with or without a robot) and asking questions/looking around other robots will probably teach you a lot more in a few hours than you could ever learn on the forum in a few weeks.

Not sure if the drum will be spinning or not, it needs a working battleswitch and its belt tensioned, but those are two-minute jobs so I guess I could see :wink:
But could only do at spin-up demo with it at most, outside and a safe distance away.

The ram is double acting which means you use gas to fire it and gas to retract it (less gas is used for retracting as there is less internal volume due to the space taken up by the piston rod) but if you want to conserve gas, one option is to get some bungee cord and attach it to your flipper, and just have that pull your flipper back down. This is a method used in most full pressure systems as they only tend to have one inlet to the ram, which is used to fire, so the bungee pulls the flipper back down when the gas is exhausted out of the ram. You'd need to make sure the elastic force of the bungee isn't so high that your flipper is struggling to flip against it, but you could play around with different types of bungee cord (more elastic, less elastic, more strands, less strands etc) and see what option works best.
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Re: Technical feather stuff

Post by MicroGravity100 » Sat Jul 02, 2011 12:25 pm

Thanks for all the info, Jamie.
I'm signed up for the AWS and I will be there, and I would love to talk to you about building a featherweight. I've found everything required now except pipework, so does anyone know ehere I can get some Pipework for the ram and gas bottle? :)
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Re: Technical feather stuff

Post by joey_picus » Sat Jul 02, 2011 1:49 pm

I can sell you a gas bottle Jarvis actually :) I've got a 600g one with tap and connector for a regulator that I got before I realised that pneumatics were something I was out of my depth in - are you interested?
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Re: Technical feather stuff

Post by MicroGravity100 » Sat Jul 02, 2011 2:35 pm

Thanks Joey, that sounds perfect! How much?
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