Is this cylinder legal?

It’s a 2-inch bore with a 12-inch stroke. It accepts the tubing that came with the kit and operates fine with the compressor and solenoid valves. I ordered some 2-inch, 18-stroke cylinders with our voucher from Bimba, but I don’t think they will be in before bag day. This one was donated to us. The writing on the cylinder under the Bimba logo is LT-3112-D and underneath that is &*].

If the cylinder is legal, is the mount it’s attached to legal? Provided that it does not make our bot weigh too much.



Edited to add more pictures.

All legal.
Restrictions are just that it be rated appropriately, take 1/4 tubing, and it remain unmodified.


What a relief! Thank you!

In general, if it isn’t illegal, it’s legal. You seem to have covered all your bases with checking rules legality, so you’re good!

R84 lists the allowed pneumatics components

R84I allows pneumatic cylinders without restrictions. As long as that cylinder doesn’t break any other rules (which it doesn’t look like it does from a quick look), you should be fine.

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Outside of what has already been discussed, one possible issue in regards to the mounting guide would be the price of that unit. Similar (at least in spirit) industrial guide units for cylinders can get pretty pricey.

If the donor has a BOM or drawings for the guide unit, it may be possible to use it directly, or create a cheaper and less “industrial” assembly better suited for FRC loads.

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What is the fair market value of it? It needs to be <$500 per R13.

On a side note, do the rules not require the fittings to be push-connect style? I could have sworn that was a rule but I cannot find it. I ask because this photo appears to show a different style.

Air solenoid valves have a maximum fitting size, they must have 1/8 NPT (or smaller) and all tubing must be 1/4 or smaller,

But cylinders don’t have a max fitting size. Cylinders ‘take’ 1/8 NPT or 1/4 NPT. Or Metric in some cases. Cylinders bigger than 1-1/2 inches bore actually have 1/4NPT fittings, so may need bushings to install a 1/4 tube fitting in them.

When you say “take 1/4 tubing” you mean “can be fitted to take 1/4” tubing"

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R84c is probably the relevant section of the manaul

R84. The only pneumatic system items permitted on ROBOTS include the items listed below.

c) Solenoid valves with a maximum ⅛ in. (nominal, ~3 mm) NPT, BSPP, or BSPT port
diameter or integrated quick connect ¼ in. (nominal, ~6mm) outside diameter tubing

Emphasis mine. I read this section as two statements, separated by the bold “or”. The first states that solenoid valves with ports larger than a 1/8" NPT (which, as an overall size, is not nominally 3mm) port are not allowed, regardless of the type of fitting that may be placed in that port to interface with tubing. The second part is, in my opinion, essentially intended to make the commonly-used SMC manifold with integral push-to-connects explicitly legal, despite the fact that it does not have “ports” in the typical sense a manifold block would.

I don’t read either of these statements as requiring quick connects/push-to-connects for tubing, only ensuring port/tubing size restrictions are respected.

Edit: As @hrench points out above, those port restrictions apply only to the solenoid valves themselves and not actuators.

Our solenoid valve is fine, I’m asking about the cylinder.

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I’m pretty sure that’s exactly what he meant.

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If the block/bearing assembly a COTS item you’ll need to show it’s cost.

If the block/bearing assembly was custom made by someone (the donor?) outside of this year’s build cycle then I think it might be illegal.

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I can’t tell if that was useful information or pedantry.

Can you see how they work any better in these pics? They operate like all the other ones, just a metal lip instead of a plastic one. You push the tubing in, and in order to remove them you push the metal lip down. “Like a chinese finger trap” as one of my team said.

@Christopher149 had a somewhat tangential concern about fitting requirements, which is what I was addressing with my statement about port sizing. Sorry if this caused confusion.

What you have on that cylinder are likely similar to the “quick connects” Christopher was referring to, but yours just happen to be metal and have a protrusion in the middle of them that most plastic varieties don’t have. All push-to-connect tube fittings I’ve seen operate in a similar way.

Saying there’s a difference between “takes 1/4” tubing" and “can be fitted to take 1/4” tubing" may be a bit pedantic, but I’m also of the belief that in engineering or technical situations things should generally be communicated as accurately and unambiguously as possible.

In the end, this is very likely a legal cylinder. To determine if the guide unit is legal, please take into consideration what James and myself have brought up in terms of price and when it was assembled.

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Looking at similar models on the Bimba site I think the thruster it’s attached to far exceeds the $500 limit. Thanks for the heads-up!

I don’t think the guide unit is legal due to what I’m seeing on the Bimba site. Wow these are pricey.

It’s enormously heavy anyway, so I think I’d like to see my team rig something up.

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We solved the same problem with a handful of OTS parts from McMaster.

All of the McMaster PNs are in our OnShape directory, linked in the first post.

Hope this helps.

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Hold on a second:

You have a Bimba TE-3112-D Composte Bearing Thruster (2" bore, 12" stroke) with Dowel pins option which can speced out on their catalog page 3.11:

Even cooler is the nifty create your own CAD site here.

The catalog which requires math says those options = $726.26. The CAD page shows $778.

Both of them say it might have been ordered without the cylinder ( aka TEV-3112-D ) , the catalog says call Bimba for a quote, but the CAD site says is $688 (implying the cylinder is ~$90)

And furthermore on page 3.14 the cylinder itself is a separately available COTS part LT-3112-D which I can find no list price in either place: However, it is available from this company: for $112.90 (ignore the picture as it is a generic small bore LT-xxxx)

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Thanks for the info. I referenced that bimba page above in another response, and determined that the thruster was too expensive to use. A team member’s dad is a machinist and he’s going to look into making us a lighter and cheaper assembly.

However, the cylinder itself may also be too expensive, as it turns out, because the industry mentor who donated it to us said that it might be rated for continuous use which may drive the price up higher than $500. He’s going to check and see if he can get a BOM for the cylinder and thruster assembly so we can know for sure. In the meantime, I’m going to call bimba for a quote.