pic: Just finished our pyramid. Conduit seems to work fine.



Decided to make the pyramid out of conduit to save some money. Seems to be holding up.
Gussets were cut out of 1/8" steel using our CNC plasma cutter.

Can’t wait to climb this thing.

SO MANY G02 VIOLATIONS! :ahh:

What’s she weigh in at?

You guys own a cnc plasma cutter? lucky. How does my team get one? Very nice pyramid

that looks way better than U-bolts and plywood

Hahaha:p
Sweet pyramid guys!

Haha, yea. It’s incredibly useful. I managed to pump out the full set of gussets in less than 15 minutes.
We have the 4’x4’ table made by these guys: http://www.plasmacam.com/indexfla.php

I’m not quite sure of the overall weight. It’s really not that easy to weight this thing.

Thanks for the compliments guys. We just want to give some inspiration to teams out there. CONDUIT WORKS GREAT! =)
Albeit, we had to use extra ventilation and masks to weld this thing. It was well worth it.
The hardest part was probably assembling, we needed about ten people and a dozen 2x4’s cut to length to get this thing in position.

And I’m sure that the judges would overlook the G02 violations in this case. :wink:

Did you use thick walled conduit.

Is the OD spec of this material not ~1/8" larger than the 1.5" of the game pyramid tube spec?

We were also thinking to use the conduit and ignore the size difference.

-Dick Ledford

Which set of specs did you use? Noting the differences between the different drawings we are a little concerned about building ours until the GDC clarifies which one is correct…::rtm::

I’ve learned the hard way that all FIRST specs are nominal. Failure to plan around that fact has bit us on more than one occasion!

Not really the answer I wanted but at least it’s honest :smiley: guess we’ll just pick the one closest to the dimensions given by the game manual…

Well, let’s be honest… Did they give us a spec on how thick the powder coat is? (I do not believe they did!)

Building for less-than-perfect fields is essential for success!

Kudos to you and thanks for posting this variant.

Can you confirm my back of the envelope calculations that the distance from center to center of the horizontal members in the plane parallel to the floor is approximately 22 inches?
:smiley:

Good job, I was wondering if this might work. The competition pyramid has to be built to a pretty high standard, given that it has to stand up to up to three robots for many matches, but something lighter should certainly be fine for testing.

Echo that, inquiring minds really want to know - the $$ difference is about 3x.

Andrew,

I am pretty sure that the 30 inch measurements are in the plane parallel to the floor (the length of the diagonal members are 104 inches).

It never occurred to me that the actual distance (in the sloped plane) was greater than 30 inches. My (probably wildly innaccurate) visio model shows it to be about to 32.4").

The conduit we used had about a 1/16" wall thickness. Make of that what you will.
We built off the specs from the “Game Specific Drawings,” not the team version.
We don’t really mind discrepancies in pipe diameter and angles (a couple of corners are a few degrees off). If you can’t build a robot to tolerate those minor differences in designs and implementations, you are really building it too precisely. As in Logomotion, many teams had very fast minibots, but the tolerances needed to get them onto the pole were just too small. We’re thinking the same logic applies to this.
For those of you asking about measurements, the center of the piping in each rung is 30" vertically off the ground. The slant height is about 32"-33" if I remember correctly. Just use some simple trigonometry to figure it out precisely.

This is thinwall, aka EMT. It’s the less expensive stuff. It runs around a dollar a foot at my local big box home center.

CORRECTION MADE. IGNORE WARNING BELOW.
WARNING FOR CHECKING POSSIBLE RADIUS VERSUS DIAMETER ERROR ON THE SUGGESTED ITEM (spherical washer)!!!

MOSTLY OFF THE SHELF H/W CAN ALLOW BOLTING YOUR CONDUIT TOGETHER & WITHOUT GUSSET PLATES NEEDED.

Here is how to save even more $$$ and time, esp. if in-house welding not so good or not available.

You can buy mostly off-the-shelf hardware from McMaster Carr to sturdily bolt your pyramid together.

The only special items are the making of (12) 1.25" OD conduit tube inserts, for which we are using 1.25" OD bar stock of 2011 aluminum (~$10/ft @speedy metals.com), which pieces then need to have two holes drilled/tapped @5/16-18 (or M8-1.25) into their OD for the assembly bolts to thread into.

Then ~1-1/4" long flanged button socket cap screws protrude out from the IDs of the horizontal tubes, first passing thru a spherical washer against the tube’s ID, then going through a 5/16" hole in backside of the horiz. tube wall, then through a pair of flat-to-flat (curved ends out) nylon tube spacers that will give an ~1/2" tube spacing between the slope tube and the horizontal tube, then thru the slope tube 5/16" hole, and finally they thread into the tapped holes of the custom made aluminum inserts fitted inside & holes aligned to the slope tube.

So to have the inserts work as corner joint anchor points at each level, pairs of 5/16" holes are drilled into the slope tubes at proper angle and elevation. The 1.25" OD aluminum plug inserts (~2" long w/ pair of tapped holes) are then slid up into the slope tube and aligned with that level’s pair of tube holes, and the cap screws are fitted through both tubes, along with the rest of the H/W stack to give a reasonably strong joint.

I forgot to mention that small holes are also needed on the outside of the horizontal tube for the allen wrench to fit through while tightening the joints. These can be drilled as a pilot holes in the process of doing the backside larger holes. Since this wrench hole size is so small, it doesn’t affect much as far as interacting with the robot differently than a proper pyramid will, which is another reason for choosing the flanged button socket head cap screws (smaller wrench size & curved profile head top).

Keep in mind that the spacing between horiz. conduit tube and sloped tube can be adjusted wider by adding a washer or two between the pair of curved end nylon tube spacers.

Hope this assembly helps teams get their test pyramids built a little more quickly and easily than otherwise might have been possible for them.

Flanged Button Socket head bolts:
Min. length needed is ~1-1/4" and McMaster only goes to 1" on 5/16-18 so we went M8-1.25 x 30mm instead of 5/16". Other places have the longer 5/16" cap screws. Stay with button head (not socket head) or length gets too long to fit easily thru hole from inside of the horiz.tube ends.


http://images2.mcmaster.com/Contents/gfx/large/92137ac1l.png

Note that the curved end nylon tube spacers are made to match a 1-1/8" OD tube size, but they should crush down and flex enough to still give decent stability of the horiz. tubes.
If we find they wobble too much, with all the money we saved, for plan B we bought a 1.5" dia. ball end mill (3/4" shank, to do some reshaping of the curved ends. We can also use larger dia, or square, nylon bar stock to make some one piece spacers with the two curved cuts in the ends made at the proper skew angle to each other, something that is not an issue with the smaller radius spec., off-the-shelf pair being able to swivel relative to each other.


http://images1.mcmaster.com/Contents/gfx/small/92842ac2s.png

CORRECTED FOR BEST TUBE ID RADIUS MATCH => Male spherical washer with 15mm radius (gives match to 1.2" ID tube) - expensive at $1.70 each & may be cheaper elsewhere, or perhaps not even required.
CORRECTED SPEC. ID- 10.5mm OD-21mm; Note for thin wall conduit use next size up Metric washer with 17mm radius (either size will still work OK with 5/16-18 or M8 cap screws) => http://www.mcmaster.com/#98148A103
http://images1.mcmaster.com/Contents/gfx/large/94007a038p1l.png
http://images2.mcmaster.com/Contents/gfx/large/91944al1l.png

Home Depot has the 1/8" ( is this the heavy wall?) 1-1/4" conduit with a 1.51 OD spec & 1.25 ID spec. at the same <$1 a foot here in Chicago.
Online price — http://www.homedepot.com/Electrical-Electrical-Boxes-Conduit-Fittings-Conduit/h_d1/N-5yc1vZbohlZ1z113dh/R-100400410/h_d2/ProductDisplay?catalogId=10053&langId=-1&storeId=10051#.UPH0rvKQk9I

-Dick Ledford

Gussets were cut out of 1/8" steel using our CNC plasma cutter.

Is Isaac Clarke on your team? :yikes: