2767 Sticks to HAB level 3


#21

Particulate filter. Vane pumps don’t like to ingest anything.

I happen to be old enough to get the vacuum tube thing.


#22

You’re overthinking it Richard–ours didn’t have a gauge and was just a cheap particulate air filter from Harbor Freight! We were concerned about the potential for damage to the vane pump.


#23

What kind of Air tank are you using?


#24

We fabricated them from aluminum tubing and 3D printed end caps. FYI 3D printed parts can be porous.


#25

And thats legal?


#26

R84-M addresses this


#27

It is perfectly legal if it is not part of your pneumatics system. My team cut a clippard air tank in half and then used epoxy to put a piece of lexan on the open end to use for our vacuum system


#28

I had a couple of questions about the modifications you guys made to the vane pump. Is there a reason you chose to drive the pump shaft with a pulley off of a 775 rather than make an adapter to drive the pump shaft directly inline with the 775? Was the pulley ratio you used 1:1 or did you find that you needed to increase or decrease the pump shaft speed?

On the topic of the suction plate, did you guys face any trouble with seaming the weather stripping foam where the loop terminates and/or leaks? How long did your plate hold enough suction on the competition HAB surface to support your robot?

Overall this is a super cool idea and implementation and I look forward to watching you guys compete!


#29

I love off-the-wall ideas and ingenious ways other than the norm to conquer the obstacles FIRST gives us and this one is one of my favorites so far this year for the HAB 3 climbing.


#30

Thread title should be: “2767 sucks at HAB 3 climb”

3/10, very disappointed.

But seriously, the safety kick-stand, use of a vane pump, and overall packaging look wonderful. Great job.


#31

I’ve never used a vacuum system, so pardon any ignorance. I understand that a vacuum system needs to be separate from the pneumatics, but can/do teams use solenoids controlled by the pcm? Can you even use the same solenoids, or are there vacuum specific solenoids?

Also, are there any sort of pressure regulating or safety mechanism that are typically employed? I would imagine a pressure sensor that lets your pump know when to shut off.

Side note: This lift mechanism is amazing. We are a rookie team, and we have been loving all the different ways teams have tackled the challenges presented this year. We didn’t expect how different some of them would be.


#32

Yep. The safety kick stand has inspired us on our climb. It’s so simple but it’s something we didn’t think about before seeing it.


#33

Two reasons for the pulley drive:

  1. Speed reduction
  2. Easier alignment and packaging.

We simply cut the weatherstripping very carefuly with a razor knife to make a tight joint. There was no sealant in the joint itself. When under compression from the vacuum, this joint gets pressed together more tightly as the sealing material is compressed. As far as the time to hang, it will depend on the “cup” seal with the hab, the sealing in the tubing path, and the total volume of the vacuum system. In our case we have several liters of vacuum accumulator, which helps. We haven’t tested to failure recently. Early on, when we still had a lot more leaks in the tubing connections etc., we were over two minutes before it let go. Now, I’d guess at least three times that. HOWEVER, there is some concern as the season wears on that the hab surface will get chewed up and may cause issues.


#34

If you used a strip of material for the seal, was there not a gap between the two ends of the strip? How did you ensure air did not escape through this gap?


#35

See above. This is one of those rare times when things actually work out in your favor–The physics helps.


#36

The same solenoid valves can be used as in pneumatics. We have a cheap pressure sensor in the vacuum line to allow us to sense when seals are made and throttle back the pump speed. No safety mechanisms are needed since any stored energy would lead to implosive effects rather than explosive effects.


#37

You can use any solenoid with the PCM that falls within R34, electrical, pneumatic, etc. We use off the shelf Humphrey valves and since the system is not pressurizing air, it is not considered pneumatic under R84-M.

My guess is since the best you can do is -14ish PSI, (we typically hit -10 PSI) a vacuum system is less volatile then pneumatic thus you have R84-M.

We do have a pressure regulator (MPX5100DP wired into the Talon analog input) and control the vacuum to a lower level when handling hatches and cargo. This is mainly to limit the heat buildup in the pump.


#38

Interesting idea. While you MUST keep your air compressor on the robot, I don’t think there is a rule when it comes to a vacuum pump. One could argue that is this no different than using a special jig and motor to wind up gas shocks or garage door springs for later use. Which, incidentally, have both been used for climbing in the past.

Ah - I forgot you are using the vacuum for multiple purposes.


#39

How long does it take for it to form a seal? Are you providing any downforce on the plate for the initial seal?


#40

Less then 1 second to assure a seal and another second to build enough vacuum to guarantee it’s stuck.

The down force is the weight of the mechanism only.