Pyramid variation

[NXTGeek]

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.

[dcarr]

Originally Posted by NXTGeek

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.

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

[nathannfm]

Originally Posted by mwmac

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...

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.

[Tom Ore]

Originally Posted by jspatz1

Identical to this at Hub City.

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.

[mwmac]

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

[wesbass23]

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.

[CalTran]

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.

[Jon Stratis]

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.

[Wayne Doenges]

Originally Posted by wesbass23

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.

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.

[jspatz1]

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.

[JesseK]

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.

[Nate Laverdure]

Originally Posted by JesseK

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

I believe this is new for 2013.

Originally Posted by 5.5.7 Measurement

The ARENA will be open for at least one (1) hour prior to the start of Practice MATCHES, during which Teams may survey and/or measure the FIELD. The specific time that the FIELD is open will be communicated to Teams at the event. Teams may bring specific questions or comments to the FTA.

[Jared Russell]

Originally Posted by JesseK

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.

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.

[JesseK]

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.

[mwmac]

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..