Other Parts and Materials

[joann halloran]

Reply to this post to ask a question about Parts and Materials in the Robot that are not LEGO or TETRIX related.

[hotshot2]

Q: Greetings,

In reference to <r5> c13 (Compatible mechanical fasteners (nuts, bolts, screws, etc.)), what constitutes an incompatible fastener? For example, a #6-32 all-thread rod is compatible w/the provided nuts and standoffs--is it legal?

Thank you

A: Threaded rod, used as a bolt/screw would be allowed, but threaded rod used as a structural element would not.

[hotshot2]

Q: Greetings,

In reference to <r5> c1, c2, c3, c4, c6, and c9, how is the maximum dimension determined? For example, do you consider the diagonal when measuring an 18" x 18" square? Likewise, what is the maximum dimension of a 1" x 48" strip that is formed into a hoop of diameter ~15"?

Thank you

A: the total area of each type of material must be less than or equal to 576 sq. in. (i.e., 24" x 24") and the individual pieces must be able to be cut from a 24"x24" piece of raw material.

Your hoop example would satisfy the area constraint, but would fail the extent constraint.

[hotshot4]

Originally Posted by 2009FTC3595
Q: I believe there is a discrepancy in the game manual regarding the allowable length of cable tie. R5c allows for 11" zip ties (page 30) while the robot check list (page 51) specifies a maximum cable tie length of 8". Which is correct?

Thank you

A: Thank you for pointing out this discrepancy. Rule <R5>c22 allows non-metallic cable ties up to 11" in length. The Competition Inspection Checklist will be updated.

[hotshot4]

Originally Posted by 2008FTC0135
Q: I noticed that the amount and types of plastic sheeting allowed this season is way more than it was last year. Are teams allowed to use up to 24"x24" of all the different types of plastic for a total of 16 sq feet allowed (4 sq ft of each of 4 different materials).

A: Yes, so long as no other rules are violated in the process.

[hotshot4]

Greetings,

The all-thread was just an example--I'm hoping you will answer the general question of what constitutes an incompatible fastener.

Thank you

This is in regard to the original question in post #2.

A: It is impossible for us to list and/or rule on all compatible or incompatible fasteners. However, information about the intent of the rule should provide sufficient guidance.

Rule <R5>c13 allows "compatible mechanical fasteners (nuts, bolts, screws, etc.)." The intent of this rule is to allow teams to use fasteners from any supplier that are substantially the same as TETRIX fasteners. Compatible fasteners are characterized by using the same thread characteristics as TETRIX fasteners. For example, an acceptable substitute for the TETRIX 6-32 thread, 1/2" length socket head cap screw is a 6-32 thread, 3/4" length, button head cap screw purchased at a local hardware store.

Threaded rod with the same thread characteristics as TETRIX fasteners is basically a headless screw and would be an acceptable substitution as long as it is used as a fastener and not as a structural element.

[hotshot4]

Q: Another question regarding <R5> c13: Does "compatible fasteners" include 6/32 washers. We think washers would be good to prevent damage to the plastic ears on the controllers and servos when screwing them down. Washers also could be useful as thin spacers.

Note that washers are already in the Tetrix kits (with the pivot bearings); but they are not 6/32 washers.

A: Yes, washers that are compatible with 6-32 screws are allowed.

[hotshot4]

Q: Any non-metallic zip ties may be used up to 11" long as stated by <R5>c22. The question is: Is the length before or after the zip tie is put on the robot? Can an 18" zip tie be cut down to 11"?

A: Zip ties longer than 11” may not be shortened and used for Robot construction.

[hotshot3]

Q: Is it possible to use more than one thickness of a particular material as long as the total area for that material does not exceed 576 sq. in. or the extent constraint? For example, use a 12" x 24" x 0.0625 sheet of Polycarbonite and a 12 x 24 x 0.093 sheet of Polycarbonite. This would constitute a total for Polycarbonite of 24" x 24" that is within the thickness limit.

A: Yes.

[hotshot3]

Regarding the allowed plastic materials, I cannot find Kydex plastic at Home Depot or elsewhere. Is it a thin, flexible plastic that I might find sold under a different name as a different product (ie thin flexible cutting board for kitchen use)? Also is ASB plastic the same as the rolls of plastic sold for painting tarps etc at Home Depot that come in various mil of thickness? Thank you.

A: To quote some of the product literature, "Kydex-T is a proprietary acrylic/PVC thermoplastic sheet that is cost competitive with fire retardant ABS/PVC (FR-ABS) formulations while providing higher impact strength, rigidity, tensile strength, abrasion resistance and extensibility. Unlike FR-ABS, Kydex-T normally requires no drying, and offers significantly greater resistance to a broad range of corrosive chemicals and cleaning solutions. Kydex-T is available in eight gauges from .028" to .250", two distinctive surfaces textures, and a range of popular colors. Excellent forming properties result in uniform wall thickness and crisp detail, plus easy machining and fabricating using conventional methods, further expanding finished part possibilities."

Kydex can be bought at online retailer like professionalplastics.com and others. Use Google to find one for you. Be mindful of the size and thickness limitations from Rule <R5>c.

ABS stands for Acrylonitrile-Butadine-Styrene plastic sheets. An ABS Plastic sheet is an easily machined, tough, low-cost rigid material. It can be turned, drilled, milled, sawed, die-cut, sheared and routed. I don't think it is the same as the tarp used for painting sold at Home Depot. ABS can be bought at lots of online retailers including McMaster-Carr (Part #8586K452). Use Google to find a retailer for you.