Pyramid Dimension Contradiction

[TheChosen1]

Has anyone else noticed the difference in width of the pyramid bars between the game manual here: http://frc-manual.usfirst.org/viewItem/3#2 and the prop construction .pdf here: http://www.usfirst.org/sites/default...c_Drawings.pdf ? It may create some confusion when testing the robot for our team.

[Aren Siekmeier]

This also appears (I don't know yet to what extent) in the .STEP version of the pyramid provided by Autodesk. The top rung ends up short of 90" off the floor (bringing the whole top goal down with it), and the angles are off (exactly 60deg in the corner and almost 68deg on the side, as opposed to the other way around as advertised in the manual). The base also does not match the 94" spec in the manual. Somehow, however, the first two rungs are in the right positions. It would be nice to have some clarification on this, for sure.

I haven't yet been able to import the Pro/E files into Solidworks, so I don't know what issues that may or may not have.

[Jack5885]

Our team has spent hundreds of dollars (a bit under a grand I think) on building the Pyramid along with other field pieces. This is a major problem that needs to be addressed.

Not only is it out of the official competition spec, but the entire pyramid is completely unstable. The top twists around and is completely unsuitable for any kind of robot hanging activities. We will probably weld in cross-members to support it, but doing so could block our robot from climbing the pyramid-depending on our design.

Out team can't afford to throw that kind of money around if things that were supposed to be tested don't work.

[Norsk]

Hey what schematic did you use to make your pyramid? could you provide a link? i found http://www.usfirst.org/sites/default...c_Drawings.pdf

But it seems overly complex, is there a schematic somewhere with the pyramid spec on just one page.

[JesseK]

Originally Posted by compwiztobe

This also appears (I don't know yet to what extent) in the .STEP version of the pyramid provided by Autodesk. The top rung ends up short of 90" off the floor (bringing the whole top goal down with it), and the angles are off (exactly 60deg in the corner and almost 68deg on the side, as opposed to the other way around as advertised in the manual). The base also does not match the 94" spec in the manual. Somehow, however, the first two rungs are in the right positions. It would be nice to have some clarification on this, for sure.

I haven't yet been able to import the Pro/E files into Solidworks, so I don't know what issues that may or may not have.

The game manual's probably +/- 1" since it isn't clear on whether the dimensions represent the center or outer diameters of the pipe. I would trust the technical drawings FIRST put out over any other representation, if you really are designing for such a precise measurement. However, I think the angles are still mostly correct for the face vs corner views. If viewing the pyramid from corner to opposite corner, the dimensions of the top and base are not the same as what they are if the pyramid is viewed from a side, face to face (thus they're ~61 degrees in the corner perspective vs ~68 degrees in the side perspective).

I suppose it's more about exactly how FIRST designed the pyramid for manufacturing vs how they communicated the design to AutoDesk. If FIRST made an exact 68-degree angle on the sides, then the top would come up short (and be slightly narrower than advertised too). Yet if they made the top rung a precise width (more likely, I think), and the base a precise width, then they did some rounding with the advertised angle. If Autodesk took the rounded angle as an exact angle, there's a discrepancy in communication between FIRST and AutoDesk. I haven't tried to pull in the AutoDesk model yet; we've only been working in 2D sketches for the time being as we proof things.

But again, we're taking it as "90 inches -ish, probably". It's easy to make a tolerant design for climbing either pyramid dimension, IMO.

[CalTran]

I was looking at the Autodesk Inventor one and all the angles I could measure all measured out at 68.9...which is a new measurment.

[Undertones]

I'm having troubles visualizing what the problem with the specs are. Can someone explain in a way that I am likely to understand?

[misterli]

Is it possible to purchase the pyramid from FIRST?

[cgmv123]

Originally Posted by misterli

Is it possible to purchase the pyramid from FIRST?

No.

[Retired Starman]

I built one of the pyramids according to the plans for the competition field for the Peachtree Kickoff. It should be part-for-part interchangeable with the ones FIRST has built.

There is a 60 degree angle between the legs and the floor. That is, if you start at the top of one leg, go to the floor, draw a line to the diagonal leg, the angle made between the leg and the floor is 60 degrees.

If you start at the top of one leg and go to the floor, then to either of the adjacent legs, I measure an angle of about 67-69 degrees. I was using a very small protractor, however, so I'm not sure of the exact angle, but it is in this range. Looking at the pyramid from the side, the side view or view you get by projecting the vertical image on a flat surface gives a base angle, according to the plans, of pretty close to 68 degrees.

The outside dimensions of the rungs, going vertex to vertex of the rungs is

Middle Rung = 50.63 in.
Lower Rung = 75.13 in.

This assumes the weld adds nothing to the length, that is, the weld is ground down to the original tube dimensions at the corners. On my pyramid, I haven't ground down the weld and don't intend to, so our lengths are somewhat longer.

I'll have to wait until we assemble the pyramid again to get an accurate dimension on the rung heights. We are painting the pyramid now.

Remember that the pyramids are made of tubing, not pipe. Pipe is sized by internal dimensions, tubing is sized by outside dimension. The DOM tubing used in the official pyramids has an OD of 1.50 in.

If you are building a pyramid from the Team Built plans, be careful. Team built plans call for 1 1/4 in. water pipe which has an outside diameter of 1.66 in. If your robot design depends on clamping or hooking the tubing, be aware that the diameters will be different.

I would suggest that teams building a pyramid use EWR tubing which is "good enough". The finish isn't quite as smooth, there is a weld up the length (which may create a bump inside the tube, but the cost is much more reasonable.

Dr. Bob

Chairman's Award is not about building the robot. Every team builds a robot.

[Aren Siekmeier]

The Pro/E version of the field appears to have the correct pyramid geometry.

http://www.chiefdelphi.com/forums/sh...80#post1212082

[dcarr]

Originally Posted by misterli

Is it possible to purchase the pyramid from FIRST?

http://www.youtube.com/watch?v=7KiVR9rmEgc

In this video, Andy says that AndyMark may offer one for purchase - could be an option if you are unable to build one yourself.

[slijin]

Originally Posted by CalTran

I was looking at the Autodesk Inventor one and all the angles I could measure all measured out at 68.9...which is a new measurment.

I'm not sure where you're getting 68.9, but that's approximately the angle between the diagonal and the rung when measuring in the plane of a face of the pyramid.

The 60 comes from measuring the angle between the diagonal and the floor (or a plane determined by a set of rungs); the 68 (IIRC, 67.72) comes from projecting that angle onto a vertical plane parallel to an edge of the pyramid base.

[CalTran]

Originally Posted by slijin

I'm not sure where you're getting 68.9, but that's approximately the angle between the diagonal and the rung when measuring in the plane of a face of the pyramid.

The 60 comes from measuring the angle between the diagonal and the floor (or a plane determined by a set of rungs); the 68 (IIRC, 67.72) comes from projecting that angle onto a vertical plane parallel to an edge of the pyramid base.

I measured from the diagonal to the pyramid base plate

[slijin]

Originally Posted by CalTran

I measured from the diagonal to the pyramid base plate

Did you measure to the plane of the base plate, or a line in the base plate? There is a distinction.