Pyramid variation
 

Now that we've gotten through two weeks of regionals, I wanted to see what folks have been noticing in terms of variation of height on the competition pyramids. I've seen stray posts here on CD, Facebook, etc. claiming 1" or more of variation, but I want to confirm if such findings are true. Please share any measurements or observations you have.

Re: Pyramid variation
 

Palmetto pyramids were within 3/8". That is a typical tolerance for most FIRST fields. Some of the variation was probably due to the flooring underneath. You could see a gradual change in elevation in the carpet when on the field.

We try to keep these type of tolerances in our design. Call it "room for error". We typically expect up to a 1/2" difference in field vs drawings. Overall though the two pyramids at Palmetto on the field and the practice pyramid were within "tolerance".

Re: Pyramid variation
 

The pyramids at Northern Lights were 28 5/8 in from the bottom of the bar to the floor.

Re: Pyramid variation
 

The official measurements dictate 30" to the center of the bar, right? So in fact, this was only 0.625" out of range if I understand correctly. Still not too bad.

I'm looking to see if there are any documented cases in which the pyramid was dramatically off (i.e. close to or greater than 1")

Our practice pyramid is about 3/8" off on the bottom, which I'm assuming (hopefully correctly) is within the range that could be expected at a competition and what we should be able to handle.

Re: Pyramid variation
 

30" to the center minus a 3/4" radius is 29-1/4" to the bottom of the bar, so it was low by 5/8".

That would be 3/8" out of the tolerance range.

Re: Pyramid variation
 

The problem we have been grappling with is that the pyramid pieces all "slide" together and there are no pinned connections between the assembled sections. During climbing, the sections pull apart and the pyramid turns into some sort of phsychadelic rhombus. This has been especially evident in our case as we induce a significant cantilevered load off the side of the structure. The reaction of the FTA/Field staff seems to be a shrug of the shoulders. It has been a dissappointment for us thus far and has forced us to rework several parts of our climbing mechanism to deal with the variation. A cordless drill, hammer, drift and some roll pins would go a long way here.

Re: Pyramid variation
 

We measured as low as 28-3/4 at Orlando.

Re: Pyramid variation
 

To be fair, FIRST was upfront with how the pyramid was assembled. It's not like it changed over the season. Adding something now could affect many other teams.

Re: Pyramid variation
 

Identical to this at Hub City.

Re: Pyramid variation
 

So the pyramids are supposed to come apart during game play and any attempt to make them stay together would affect other teams? How many other teams banked on them comming apart?

What would you say if the pyramid collapsed? Is it our fault because we should have known it would collapse based on how FIRST designed it?

Re: Pyramid variation
 

The measurement from the floor to the bottom of the lower rung on the pyramid used at Hatboro-Horsham last weekend was 28 1/4".

Re: Pyramid variation
 

The way the field interacts with robots has always been part of the challenge of the game. The FRC staff can not and should not be expected to build a field around a single teams robot design.
In 2005 I witnessed multiple Scoring pyramids pull up from the floor because of how many tetras were scored on these, that could have never been predicted (229 at FLR for example). Also in 2007 with the rack, who ever would have thought a team would have been able to move that completely, it just isn't foreseeable.
With the way the field has to be designed to be durable and also transportable, I think the designs this year are very well done, being able to give the most unobstructed goal, and climbing ability to all teams evenly.

Re: Pyramid variation
 

It is week 2 and I saw MC's standing on the "30" inch bar at two regionals today. At a minimum, First should unequivocally end this practice...

Re: Pyramid variation
 

The MCs are told to stay off the pyramids for the most part but for special times such as eliminations.

Re: Pyramid variation
 

The MCs should be eligible for G02 fouls. (A Yellow Card for team members climbing onto the pyramid, FWIW.) Second card means that another volunteer MCs for a couple hours. Wait, I'm not sure that's a penalty for the MC... How about a second card means the MC stays inside the netting for a match or two?

Re: Pyramid variation
 

The pyramids at SD were noticeably different from each other, with the red pyramid's 10pt bar being too low to the ground. A number of teams were having problems with that and complaining to refs.

Re: Pyramid variation
 

Sounds like it will be necessary to test on both pyramids if possible - with the way our Thursday is shaping up (6+ hours of work at last count), this might be tricky :eek:

Re: Pyramid variation
 

I saw an FTA who shall remain nameless do this to remove a 5 Point Frisbee when it took the field crew more than 5 min to figure out how to do it the right way

The problem I saw most was the sway from side to side at least on the practice one. With all the compounding error the top moved at least a couple of inches side to side when you grab the side bar, it was quite shocking, not something I would want to climb...

And if you have not seen one yet, this is what they look like taken apart.

Re: Pyramid variation
 

I was told one Northern Lights pyramid was 30 3/8" to the top of the bar and the other was 30 1/2" to the top of the bar. I believe this field is going to Kansas City next. Our robot is about 28 3/4" high and we were able to drive under.

Re: Pyramid variation
 

Did anyone encounter more level one bars lower than nominal specs during Week 3?

Re: Pyramid variation
 

The 10pt bars on each side of the pyramids at Boilermaker were all different heights. The lowest being 28 and 1/2" preventing us from going underneath a couple bars and just barely scraping by on the others. We managed to lower the highest point on our robot enough to slide under all bars by the end of the regional.

Re: Pyramid variation
 

At Greater Kansas City, when I measured Thursday morning, they were pretty close to being in spec. The red pyramid was about 29.75" to center, and the blue pyramid was about 29.5" to center.

Re: Pyramid variation
 

When I measured at Lake Superior, the two pyramids were virtually identical... no more than 1/8" off in height for any of the level 10 bars. They were all about 1/4" below the ideal, however.

Variation should be expected and planned for. When we built our robot, we planned for an extra 1" between the top of the robot and the bottom of the lower bar, in order to ensure we could go under. We also built in an extra couple of inches of reach, in case the spacing between the bars wasn't exactly 30". As a result, variation in the pyramid design wasn't even something we thought about at the regional - the climb just worked.

Re: Pyramid variation
 

We (FRC Team 1501) robot was 28.5 to the top of our lifting hooks. When going under the pyramid they would scrape the bottom of the bar. We had to mill off some of the hook.

Re: Pyramid variation
 

Having been around on Wednesday to help setup 2 practice pyramids and see the field pyramids set up as well, I have one theory as to their height variation. When assembled, the multitude of slip joints do have some slop/play in them. The four legs can be allowed to flex/spread outward, or can be forced inward before their location is fixed on the floor by the wooden inlays, carpet, and tape. This can lead to some variation in the horizontal bar height depending on how much they are or are not allowed to spread. In KC the legs of the pyramids we helped with were cinched inward with a winch strap all around before the foot flange locations were set, and these crossbars ended up very near the 30" to center spec. The crossbars we saw in Hub City were all significantly lower.

Re: Pyramid variation
 

Wait a second -- FTA's at other events actually let teams MEASURE field elements???

Any time I've asked to do so at Virginia or DC, even on practice day, I've been told 'no'. I don't know why -- it seems to me that it would only help all FRC teams if the FTA's made official measurements and then posted them for all teams to see.

Re: Pyramid variation
 

I believe this is new for 2013.

Re: Pyramid variation
 

Check out rule 5.5.7 (new for 2013)

The pyramids at Chestnut Hill were close to spec - about 28.75" from floor to the bottom of the low rung. At Hatboro-Horsham, we measured as low as 28.25". The same exact field (the MAR field) was used at both events.

I think the discrepancy is caused by how tightly the sides of the pyramid are pulled together when it is being attached to the floor. At Hatboro-Horsham, there were noticeable gaps between the corner pieces and the horizontal bars (e.g. the connector pipe was visible). At Chestnut Hill, everything seemed much tighter (virtually no gaps). The gaps would let the corner pieces sit at a shallower angle relative to the ground, causing the pyramid to "shrink" in the vertical direction.

Re: Pyramid variation
 

Hmm, must have glossed over that section. This is awesome! We're close to the 28" hard limit I put on us, so it'll be nice to know if we can't drive under one of the 8 bars.

Re: Pyramid variation
 

I also overlooked 5.5.7 and believe it is very good news that team personnel can verify pyramid bar height.

However, I also believe that the simplest solution to pyramid variability would be an amendment to the playfield setup procedure for FTA's requiring a height check and adjustment of the base plate positioning. This change could help relieve teams of the need to perform ad hoc modifications to their robots that may otherwise prove to be completely unnecessary at future events. Just my .02;)

BTW,
I am available to assist with any field setup adjustments in Utah and Spokane...Just pm me..

Re: Pyramid variation
 

This is an interesting idea. Has anyone been able to get data about how much the pyramids change over the course of match play? They flex a lot and I've noticed the pipes routinely coming apart; I had to push some back together after every match I reffed. Does anyone know just pushing things back together enough to keep everything in spec once it's readjusted? Or would more work be required? Regardless, even doing it once would be better than the current way now.

I know we cleared all 8 quite well in a practice round, and were surprised the next day that we hit one, but I'm not sure what did it.

Re: Pyramid variation
 

One of the things I didn't realize until week two of competitions this year (the first week I had to assemble the field) is that the bar height spec is to the base carpet. There is a layer of masonite and a second layer of carpet on top of the masonite around the pyramid. That has thickness that makes the measured bar to carpet distance seem short.

Wetzel

Re: Pyramid variation
 

If I remember right, the pyramids at Hub City were different heights. I believe the red tower was higher than the blue (I know from personal experience because I rammed the red tower with about an 1/8" of the top of our robot, and then cleared it (accidentally; robot got stuck) on the taller blue one. If I remember right, the red pyramid was the one that was 28 5/8" with the blue one being about 28 7/8" to the bottom, but don't hold me to that.