Maximum bore/stroke length for cylinders?

[ollien]

My team was considering using some 2" bore 36" stroke length pistons for the wall scale this year. Would these be legal? I see nothing in the manual regarding max stroke/bore length, nor can I find anything more recent than 2005.

Thanks so much!

[cadandcookies]

Legal? Yes. But, legal does not mean a good idea or practical. While large pistons may seem like a good idea, I'd recommend calculating the amount of air needed to actually use them.

[ollien]

Originally Posted by cadandcookies

Legal? Yes. But, legal does not mean a good idea or practical. While large pistons may seem like a good idea, I'd recommend calculating the amount of air needed to actually use them.

Of course. I just wanted to make sure there wasn't an issue with using them.

According to the 2015 pneumatics manual, at 60 psi something of this size could lift 170 lbs. The volume needed would be ~113.1 in^3, or 1853.4 ml. This would mean we'd need four air tanks to fill one piston. Doesn't seem /too/ terrible. It's definitely doable.

[IndySam]

First:

"It's a cylinder, not a piston"

Brought to you by the IACNAP campaign.

Secondly, if you are pulling the rod back into the cylinder to lift, the area of the piston (yes that's correct) is reduced by the area of the rod.

[Caleb Sykes]

Originally Posted by ollien

Of course. I just wanted to make sure there wasn't an issue with using them.

According to the 2015 pneumatics manual, at 60 psi something of this size could lift 170 lbs. The volume needed would be ~113.1 in^3, or 1853.4 ml. This would mean we'd need four air tanks to fill one piston. Doesn't seem /too/ terrible. It's definitely doable.

Get single acting pistons if you can, otherwise you'll need 8 tanks.

[kevin.li.rit]

Originally Posted by Caleb Sykes

Get single acting pistons if you can, otherwise you'll need 8 tanks.

well not necessarily, you could plumb it so one side is at a lower psi right?

[cmrnpizzo14]

Have you found anyone who sells these? I'm sure they have them but remember that it might be the heaviest single part of your robot and will definitely take away from your weight/pneumatic budgets.

[Caleb Sykes]

Originally Posted by kevin.li.rit

well not necessarily, you could plumb it so one side is at a lower psi right?

Of course there are alternatives. I was assuming the same pressure on both sides because that is the simplest arrangement.

[Sperkowsky]

Originally Posted by cmrnpizzo14

Have you found anyone who sells these? I'm sure they have them but remember that it might be the heaviest single part of your robot and will definitely take away from your weight/pneumatic budgets.

We have one we accidentally bought 4 years ago. it's actually only around 11 pounds.

[Kyle Butzerin]

Here's one

McMaster-Carr, http://www.mcmaster.com/#6498k485/=10n6o8z

That's one way to go, we are thinking of almost the same concept, and are preparing to arm many tanks on our bot this year.

Expensive, but it could work, honestly we are looking at putting 2 on the robot stored at an angle. Therefore, roughly half the power per cylinder is needed, but twice the air... the bore wouldn't need to be a mile wide though, which is a plus.

[cmrnpizzo14]

Originally Posted by Sperkowsky

We have one we accidentally bought 4 years ago. it's actually only around 11 pounds.

Sweet Jesus...

[ollien]

Originally Posted by Caleb Sykes

Get single acting pistons if you can, otherwise you'll need 8 tanks.

Yep. Ours is double acting, but we could get away with firing it once using 4 tanks, yes?

Originally Posted by cmrnpizzo14

Have you found anyone who sells these? I'm sure they have them but remember that it might be the heaviest single part of your robot and will definitely take away from your weight/pneumatic budgets.

Our coach acquired them through the typical BIMBA voucher in our rookie season. He had no idea how large they were and we've just had them laying around. I took a look and thought they might be effective for this year.

[kevin.li.rit]

You could fire only once if you spring loaded the return/lift motion

[ollien]

Originally Posted by kevin.li.rit

You could fire only once if you spring loaded the return/lift motion

Makes sense.

[CryptoStorm]

you don't really need to worry about the volume of your tanks as you need to worry about the volume of your pump and the diameter of your tubing.

filling a cylinder like that with 1/4" tube would take forever.