I’m wondering if anyone can tell me if a custom length stroke pneumatic cylinder is allowed? I’m thinking since I’m using the word custom then it fails the COTS test but just want to make sure.
thanks-
Ray
As long as the company is willing to build one for any FIRST team that wants to buy one, then it would be legal.
That sounds good but the rules state that “All included items must be “off the shelf” COTS pneumatic devices rated by their manufacturers for working pressure of at least 125psi and burst pressure of 250psi, and used in their original, unaltered condition (except as required for assembly with other components).”
COTS is defined as:
A COTS item must be a standard (i.e. not custom order) part commonly available from the VENDOR, available from a non-team source, and available to all teams for purchase.
So wouldn’t that say a “custom” cylinder would be off limits?
D. The VENDOR should maintain sufficient stock or production capability to fill teams’ orders within
a reasonable period during the build season (less than 1 week). (Note that this criterion may
not apply to custom-built items from a source that is both a VENDOR and a fabricator. For
example, a VENDOR may sell flexible belting that the team wishes to procure to use as treads
on their drive system. The VENDOR cuts the belting to a custom length from standard shelf stock that is typically available, welds it into a loop to make a tread, and ships it to a team. The
fabrication of the tread takes the VENDOR two weeks. This would be considered a
FABRICATED ITEM, and the two weeks ship time is acceptable.) Alternately, the team may
decide to fabricate the treads themselves. To satisfy this criterion, the VENDOR would just have
to ship a length of belting from shelf stock (i.e. a COTS item) to the team within five business
days and leave the welding of the cuts to the team.)
The above clause kind of applies here, though it would change your Cylinder from being a COTS part (required for Pneumatics Rules) to a Fabricated Part.
This is a REALLY good questions for the Q&A. I believe a custom length Pneumatic Piston would be within the spirit of the rules as teams have been using them for years, but the Q&A’s answer would be final.
Ray,
I believe you are correct. COTS is defined as not “custom order” and that covers any COTS part or assembly.
Then further interpreted by this rule…
<R66> In addition to the items included in the KOP, pneumatic system items specifically permitted on 2011 FRC ROBOTS include the following items. All included items must be “off the shelf” COTS pneumatic devices rated by their manufacturers for working pressure of at least 125psi and burst pressure of 250psi, and used in their original, unaltered condition (except as required for assembly with other components).
It would seem that custom pneumatic actuators are not allowed.
This is interesting (and playing Devil’s advocate here, as we’re only using “standard” size cylinders), what would define a pneumatic cylinder as “custom”?
Let’s say XYZ Company has adopted lean, just-in-time manufacturing practices and sells pneumatic cylinders in a discrete set of different bore diameters, but at any length from 0.500" to 24.000" in 0.001" increments. Because the company wants to minimize their warehouse stock and increase efficiency by only making cylinders when an order is placed, there are no “standard” or “custom” length cylinders (as every order is made to purchase), only “standard” bore diameters.
Would this company’s internal processes as to how they manage their supply chain and manufacturing determine whether a particular item they sell is COTS or not, regardless of availability to all teams and meeting all other definitions of a VENDOR? What if the customer has no knowledge of the lean manufacturing nature of XYZ Company, as XYZ’s website does not make any mention about “standard” or “custom” sizes?
There is an alternative that might get you going and still have you using the pistons available from Bimba even if they do not meet your needs exactly.
This will work if the stroke you need is somewhere between two lengths that are available.
Select the piston that has the stroke that is the next length beyond your needs. Then cut a sleeve of tubing, you choose the material, that is the length difference between what you need and what you ordered. Make sure the ID of the tubing is large enough to slide over the piston rod and allow the rod to slide through it easily. (Make sure there are no burs on the inside of the sleeve that could scratch the rod’s surface.) Now when the piston is fully retracted, it will be held out by the sleeve. When it is extended, it will travel exactly the distance you needed. The only caveat is that the overall length of the piston is a bit longer than a custom cylinder.
Here is a picture of this in use. This system is in a relaxed state, so the sleeve is loose, but I think it explains what I mean.
hold on a sec. so according to the Bimba free parts order form they don’t offer a 5" stoke in a 1.5" bore. We ordered that same piston from a local supplier so does that make it non-COT? I would be hard pressed to look at these rules and say that a piston of any length would not be considered COT.
According to these rules, my Banebots 9:1 trannies are non-COT because it is going to take them 2 weeks to get to me. They deem 5 days is reasonable.
I think we need to apply a bit of common sense to these rules folks.
BTW: Bill is that an eye bolt attached to that upper clevis?
Art,
Do you have such a supplier? If so then there is no custom lengths right?
Wilson, you ordered one and I could order one and so could anyone else without placing a special order correct? Then it is not a custom order. Your Banebot transmission is a COTS item that is having a delivery issue. If you ordered the same part in say June, could you get it in five days?
Mcmaster has a huge selection of cylinders.
I’d go with the rule of thumb that, “If it’s on mcmaster, it’s COTS”.
Al,
I understand what you are staying, but can’t anyone order the same “custom” parts? I’m just trying to say that, in cylinders, length does not make it custom.
Another question: if I needed 5.5" stroke and ordered in “custom” from one manufacturer, but I could have ordered it out of another catalog would it be COTS?
I’m just trying to understand the rules here.
Wilson,
The OP quoted a rule about COTS and I agreed with the definition. (I have to) I further added a quote from the pneumatics rules to supplement the OP quote. If a part is custom order from one manufacturer but “off the shelf” from another manufacturer and you know it, why would you custom order the first part?
Many manufacturers are choosing to make everything in their line to order. Allen Bradley does this with pots and Globe Motor has gone this way with their motor/gearbox line. If that is the case with a specific manufacturer, then it would seem nothing is custom under the definition. Does anyone have a real part from a real manufacturer that would be a good example for this discussion? Hypotheticals are getting us no where.
Yep! It was used to both retract our kicker and then partially power the kick.
Look closer and you will see a gate latch as well.
For some reason I never knew McMaster sold Cylinders… Looks like we’ve found a new place to buy them when we’re in a pinch.
I love McMaster-Carr.
So I posted my question to Q&A. Here was the response:
- Correct, custom parts are not COTS parts.
- If any TEAM would be able to order the same cylinder with the same stroke and it is regularly stocked at a VENDOR, that part is considered COTS and can be used.
So to me that says if they don’t stock it and it is made to order then that is considered custom and is illegal.
The list of free cylinders that we can get from Bimba doesn’t seem to be a very complete list. If you use their part# configurator it seems that there is a greater variety of cylinders available. When I entered the specs for a 24 inch 3/4 bore cylinder it said it was a valid number that I could order with the click of a mouse. The same size is not available on McMaster or the freebie list. I’m going to assume that anything that easy to order is COTS.
Don’t confuse “made to order” with “custom”.
I ordered a cylinder from Bimba that is a 2 stage. Because of the thousands of combinations, they do not stock them on the shelf, but they assemble them from off the shelf parts to my order. That is a made to order item. Any team that wants one just like it can order the same part number and get one just like it.
Custom would be something not on their website and no standard order configuration. They would build something unique to my specifications.
Bimba limits the sizes available free to teams. The list of standard cylinders on their website is significantly bigger.