Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

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rubem
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Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 09 Jun 2021, 01:30

Hi everyone,

I'm assemblying a pinball table similar to the one in the Electropneumatics kit. This project has some challenges for me, the main one being that I'm a complete novice on pneumatics :shock: But thanks to you guys, this forum and the picture pool, I've been able to understand enough to get it working so far. The model is not identical to the Electropneumatics kit because: 1) I don't own the kit itself; 2) Some pneumatic parts are the classic Festo ones and 3) Some parts are non-ft, see here:

Non-ft.png
Non-ft.png (202.62 KiB) 439 mal betrachtet

The two small 3/2-way 5V solenoid valves behave similarly to the ft ones. I've included a voltage regulator on each and now I can operate them from 9V. They work well with the TXT or directly via a push-button. I'm also using 2 membrane check valves (shown above) between the compressor and the solenoid valves so that each one has its own separate air reservoir (a blue cylinder). I'm not using the big 2/2-way solenoids for now.

I don't have any red pneumatic cylinders, so I'm using an old 45 mm Festo cylinder with spring for one flipper. It works well. For the other flipper I used a leaking Festo cylinder 45 which I've pried open (someone already did it in the past, it had a lot of glue), cleaned it up very carefully, inserted a (different) spring and sealed it back with hot melt glue so I can work on it again if necessary. It has good performance, but it extends a bit less because of the different spring. Playable, but not great.

I'm still experimenting with cylinders. I took a very stiff blue cylinder, pried it open and removed the gasket/O-ring so it became a single-acting cylinder, and runs much smoothly. Then I inserted another spring in it and sealed it with hot melt glue, so it became a "red" cylinder. However the spring is too strong, so it requires extra force and the movement is too slow for pinball.

What I really want is to be able to extend and retract the cylinders pneumatically. This way I could use cylinders without springs, which would be ideal for maximum force. I learned that this can be done using an extra 3/2 way valve for each cylinder, but I don't have them, my pneumatics inventory is quite modest. I have two strong 2/2-way valves (see above), two air tanks, some old Festo valves and Festo actuators. Is it possible to accomplish this with the parts I already have?

Thanks a lot in advance for your help and patience with this "pneum-newbie".

Warmest regards to all,

Rubem

P. S. I use a blue ft compressor via a relay that connects it directly to the 9 V supply. The TXT outputs provide a lower voltage and the airflow decreases significantly.
Zuletzt geändert von rubem am 09 Jun 2021, 23:15, insgesamt 1-mal geändert.

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steffalk
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von steffalk » 09 Jun 2021, 10:30

Hello Rubem,

You can construct a 3/2 way valve from two 2/2 way valves. For each side of a cylinder, you need one 3/2 way valve. You can construct them like this:

[Air pressure] --- [2/2 way valve] --- [One cylinder end] --- [2/2 way valve] --- [free air]

The two valves are connected to the same pin of the cylinder. Open exactly one of them at a time: One to get air into the cylinder, the other to get it out again.

The alternative is one 4/2 way valve: 4 ways (one for each pin of the cylinders, 1 for the compressor, 1 for the free air output) and 2 positions (cylinder expanded or shrinked).

You can construct such valves on your own using nothing more than standard fischertechnik parts! See "Druckluftsteuerungen (Teil 1)" (pneumatic controls, part 1) in ft:pedia: https://ftcommunity.de/ftpedia/2014/201 ... df#page=58. While the text is written in German language, I guess you can see everything needed in the pictures. If not, feel free to ask here.

Best Regards

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rubem
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 09 Jun 2021, 23:30

Hi Stefan,

Many thanks for your quick answer! With some effort I was able to translate most parts of the ft:pedia article, and I find the idea of clamping/kinking hoses to control the airflow simply brilliant. Although I suspect that this kind of solution is better fit for more experimental models (they also take a lot of precious space), the idea of DIY valves is intriguing, maybe I'll test it, let's see.

In the end the simplest / most compact way would be to purchase two additional 3/2 valves anyway...

Thanks again,

Rubem

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rubem
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 10 Jun 2021, 14:38

Hi again,
rubem hat geschrieben:
09 Jun 2021, 23:30
In the end the simplest / most compact way would be to purchase two additional 3/2 valves anyway...
...I just ordered the two extra valves :D

Meanwhile I have another question: I wonder why my blue ft compressor is so noisy to the point of being annoying, is this normal? Could it be that it became noisier after only several hours of usage (not continuously)?

Greetings,

Rubem

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steffalk
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von steffalk » 10 Jun 2021, 15:36

Hello Rubem,

I have several of the blue ft compressors, and I find them loud when they are attached very fix to a model, standing on a table giving resonance. I usually fix them on ft springs and not directly to any model. It is really the compressor itself that is so loud, or only if it is built into a model? If it is loud by itself, it may well have some damage.

Regards,
Stefan

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rubem
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 10 Jun 2021, 16:00

steffalk hat geschrieben:
10 Jun 2021, 15:36
Hello Rubem,

I have several of the blue ft compressors, and I find them loud when they are attached very fix to a model, standing on a table giving resonance. I usually fix them on ft springs and not directly to any model. It is really the compressor itself that is so loud, or only if it is built into a model? If it is loud by itself, it may well have some damage.

Regards,
Stefan
Good catch! Yes, in fact the compressor is very firmly attached to the model and there are lots of BS30s in contact with the desk surface, so probably my whole desk resonates. I recall having seen the trick with the ft springs in one of your models from the picture pool. I don't have any plastic ft springs, but I have several springed feet #31307, maybe they help. I'll make some tests this weekend to determine if I can pinpoint the cause.

Thanks again,

Rubem

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H.A.R.R.Y.
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von H.A.R.R.Y. » 10 Jun 2021, 17:26

Hello,

it does not need to be ft always and everywhere. If you just want to decouple the vibrations of the compressor you could use simple rubber bands and fix them into an ft frame. More stable and durable might be some rubber bands with some surface clothing like hair ties, elastic waist band, ...

The compressor itself usually does not put problems since it is connected by flexible wires and hoses. The only two things you really want from its fixture:
  • Stay were it is.
  • Do not rotate due to its inertia.
Cumprimentos
H.A.R.R.Y.
[42] SURVIVE - or die trying

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rubem
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 10 Jun 2021, 17:44

Hi H.A.R.R.Y,
H.A.R.R.Y. hat geschrieben:
10 Jun 2021, 17:26
it does not need to be ft always and everywhere
Yes, I also think that way. I think I have some black rubber foam pieces in the storage area, they'll probably look better than my yellow rubber bands (looks are important). Maybe I'll use them if the mold odors are not too strong :D

Thanks for the ideas!

Abraços,

Rubem
Zuletzt geändert von rubem am 15 Jun 2021, 16:36, insgesamt 1-mal geändert.

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rubem
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Re: Fragen und Experimente zur Pneumatik / Questions and experiments with pneumatics

Beitrag von rubem » 15 Jun 2021, 16:36

Hi Stefan and H.A.R.R.Y,

Simply placing four self-adhesive silicone discs under the pinball table feet reduced the noise significantly, so my conclusion is that there is nothing wrong with the compressor. My desk was just resonating and amplifying the noise. I will still experiment with foam rubber when I have the time, and I'll post the results here.

Thanks again,

Rubem

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