Force required to pull HATCH through brushes at LOADING STATION

We have a plywood mockup of the LOADING STATION, build as per the drawings. The Brushes are mounted in the correct orientation. We are finding that the HATCH is surprisingly hard to pull “straight” off (ie perpendicular to the face of the LOADING STATION), unless we slightly lift it vertically.

For those teams that have build the field element, with the official brushes, what are your observations with manipulating the HATCH? Any measurements of the force required, and if you are pulling it straight off or using another method.

I have purchased the official brushes and done some initial pulls. I definitely have found that pulling the hatch out on one side works better than trying to pull it directly out. Also note that the force will depend significantly on how far apart the brushes are, and may be somewhat higher on the unofficial AM hatch covers, as the one I purchased appears to be about 1/8" oversize. I should have some actual force measurements (with the oversize hatch cover) tonight or tomorrow night.

Our plywood mockup is using the official P/N brushes and a quick verification did not find and dimensional errors in the mockup. My next step is going to be to verify the model against the official field drawings, and CAD models as there are “issues” some years with the plywood models.

We also noticed that pulling on the top edge or on the side required much less force. Unfortunately all of our current prototypes are gripping via the hole in the middle or the top and bottom edge and produce a fairly straight pull. The one field walk-through video makes specific mention about how easy it is to pull the HATCH out, but he is pulling on the top edge. I am trying to sort out if we have a model issue or a design challenge. I also wonder how consistent it is going to be LOADING STATION to LOADING STATION, especially at the later events.

I would assume that all everything is nominal, and that consistency is a “you” problem, not a “them” problem. (In other words, design for unreasonable variation in the specs.)

QFT. The first year I really did this (2013), the pyramid rungs and frisbee feeders were either two high or too low; neither of our robot systems worked without serious mods. My experience is that if you double all the tolerances in the field drawings, you’ll only be disappointed in one item about every other year.

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I completely agree about designing for the worst case, and assume that the fields will be significantly out of spec. Our worst issue was also with the pyramid, as we build a climber that went up the inside, and the mechanism was heavily dependent on correct geometry. None of the fields we played on were within their claimed tolerances. On the other hand, we could pick up the pyramid.

What I am trying to discover is what are other teams early experiences with the LOADING STATION. My current belief is that after playing with the HATCH and LOADING STATION in cad and our mockup, that due to tolerances, brush variation, and general wear and tear that HATCHES may require significant force to pull straight off. However that is based off limited testing with one plywood mockup. We could have messed up how we built it.

If you go checkout the official cad there is a circular object about 1 inch in diameter that shifts the the Hatch up and across a bit allowing for a much lower level of withdrawal force needed.

Even with that stop/rest/whatever it is, the HATCH is still not symmetric in the brushes (when you place things using the CAD models) . Potentially that is an attempt to address the different amount of brush contact on the two sides, to balance out the forces. It still seems to require significantly more force to pull it straight out than with a twisting motion and more force than I was expecting from the Field tour videos.

Q&A 238 just added some valuable info. The part they spec’ed for the Team version of the loading station has a slightly different profile. The Real field version requires lower perpendicular force to remove the HATCH PANEL

Q238 Hatch Panel Loading Station competition field design

Section 4.8.1.2 details the Hatch Panel portion of the Loading Station. We have built a model to the specifications of TE-19108 & the rubber fork of the Frost King brushes forms an ~¼" rubber lip requiring a vertical lift of the panels before they can be removed through the brush portion. We have examined the CAD models of the competition field and don’t see a corresponding lip. Is it expected to be able to remove a panel with only a motion perpendicular to the alliance wall?
asked 3 days ago by FRC 2834

LOADINGSTATION

Answer

Thank you for pointing out that there’s a difference between the FIELD version of the LOADING STATION HATCH PANEL dispenser and the Team Version.

It is possible to remove a HATCH PANEL from the official FIELD’S LOADING STATION without lifting it. TE-19108 performs similarly to the FIELD LOADING STATION (GE-19130 and GE-19155), but there are differences. GE-19138 and TE-19108-16 have slightly different profiles, which results in the HATCH PANEL on the TE version sitting slightly lower relative to the assembly. This means the HATCH PANEL is more likely to be caught by the lip of the bottom brush on the TE version than the official FIELD version.

Please look for updated Team Drawings and more information about this in Team Update 08 (link won’t be live until update published on 2/1)

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