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Need a table top that can push stuff upp in the air Answered

Okay so i need some help with a prop for a photographing stuff in mid air.

I need a device (flat surface) that I can place objects on and it will shoot them up in the air.

Imagine a bowl of popcorn or a pair of glasses with water in them flying up in the air etc.

I will then have sensors that will trigger the camera at the right time. (these devices and system I already have)

My dream would be to be able to control this "jump table" device thru a simple solenoid valve. (12v)

So my rough plan is to have to sheets of wood 40cmx50cm about 1cm thick.

Next is to have a pneumatic cylinder in between these two that will push the top plate up and down.

I probably need some sort of guides in the corners of the plates so it moves correctly.

The pneumatic cylinder will be controlled by a solenoid valve, the solenoid valve i hope to turn on/off with a 12v power supply.

The easiest solution for air source would be a co2 cartridge.But if that's to much pressure for the components maybe a cheaper air compressor in a smaller size is usable ?

So what im looking for in general advice in terms of pressure and pneumatic cylinders, which i do not have any experience with.

This video pretty much has the basic components i need i guess ?

Any general advice what to look out for when choosing components and air source ?

Thank you!

Discussions

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PaulL320Yonatan24

Reply 5 weeks ago

Thank you, but i think you failed to understand what im trying to do here. I'm talking about high-speed photography, not simple photoshop tricks.

Im a professional photographer, i can assure i have the knowledge of doing basic stuff shown in the video. :-)


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Downunder35mPaulL320

Reply 4 weeks ago

I think that is part of the problem here ;)
You might be an expert in your field but not that much in the technical department - no offence!

Just to get on the same page here:
You have something on a plate or similar, maybe a bunch of items.
You want to take pic of these items once they got pushed up into the air.
Preferably of course with a lot of light and short exposure times.
For that I amfar from being an expert as I simply don't use a camera often enough.
But I have done quite a bit of time sensitive pneumatics and hydraulics over the years.
As you seem to insist on going this route:
Normal operating pressure for air cylinders is in the region of 4 -12 bar.
The faster you want to move the piston, the more air air pressure you need.
Depending on the cylinder size also a suitable pressure vessel to store enough air.
A proper sized compressor will do here.
Now for some fineprint...
If you let a cylinder just slam into the other end enough times then your cylinder will fail really quickly.
That means for such operations the exit valve on said cylinder is usually closed before the piston can reach the end - like an air cushion to stop the impact on the metal.
Best control option here is to use reed contacts embedded into the cylinder or added on the outside.
You big problem however is not really the firing and timing for this action.
Your problem is to get enough acceleration in a set amount of time to make the things fly up - in a controlled way.
For instant high pressure in the cylinder you need big valves that act quickly.
Again no big deal.
But the mechanical part of all will be.

If I assume you need a minimum throw height of 10cm then of course you also need a cylinder with at least 10cm lift.
Not to reach the disatance but to ensure you get enough acceleration during the movement time of the piston.
Said speed must be higher than the lift off speed of your items.
Lets say you matched all parts to do just this.
You then would need precise high speed timers to set your camera.
Even with those it can be tricky as the cylinder will not always move as expected!
In time critical applications the air is kept really dry, the calinder well oiled and much more just to ensure the working conditions stay within tolerances for as long as possible.

I think I can see what you are trying but did you consider to do it the other way around to have it much easier?
Thinking of freefall here and just "dropping" the platform with the cylinder...
Less time sensitive, less complex for the mechanics and timers...
And in reality the same result in the pic apart from the fact that odd shaped items will stil fall straight instead of going a bit sideways or tumbling around.

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PaulL320Downunder35m

Reply 4 weeks ago

Thank you all good info!

Will take this into account, mechanics, and the building isn't an issue as I have access to tools and people who know how to use them.

Yes for those of who do not know the photographic parts it might seem to complex for what you get, it's not. Being able to reproduce the timing is crucial. Dropping might be a route for some shots but can't replicate some of the moves I want to make.

The camera triggering is not a problem I have all that sorted, I have several controllers (which is capable of 50um of precision) including dual ir/laser sensors along with the sound sensor.
These shots will be frozen by flash duration, not shutter speed so the timing will be close enough even if a cylinder doesn't move exactly the same speed. The trigger will be laser/ir that is triggered when the top plate crosses it.

Also, this is for a series of photos for a project, so have a budget to work with.

So a small air compressor or a simple co2 cart won't give me enough pressure, will a tank with compressed air be high enough? Worst case scenario we could just bring in a good air compressor?

I realize the challenge will be the penumatics and the mechanical construction.

Will probably buy some parts and play around on a smaller model to start with.

Again thank you for taking the time!


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Yonatan24PaulL320

Reply 4 weeks ago

To summarize my thoughts, I think to make it work, you'll find a very complicated solution, to a problem with a method that that could be eliminated... guess. But I don't have enough background info.
There's a video on Youtube I watched a while back, I think it was this one that might give you a few other ideas though:

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Downunder35mPaulL320

Reply 4 weeks ago

There is no real math required if you only need single shots anyway.
You have a given volume of air for the cylinder.
Same for the cylinder of the compressor - or the extra air tank if you use a tiny compressor instead.
What you want to do is keep volume and distance of movement as limited as possible.
A small and just finger thick cylinder will be able to push quite a lot of light parts.
But it will struggle to produce the force required to do hard work with a heavy platfor or heavy parts on it.
A short but thick cylinder might be best suited.
Preferably one that has some build in protection so you won't have to bother about the impact when the piston hits the other end.
Most industrial cylinders will do fine here.
That then only leaves the air volume and required pressure.
As said, around 8 bar is standard anyway and tha is what every cheap compressor will offer you.
If you ask in a supply store for a pneumatic cylinder that has your max travel distance, fast speed and the right volume for single use with a standard compressor they will be able to offer you a selection.
From experience I tend to say that larger diameter hoses and the valve close to the cylinder in question works best.
Having all on the compressor side with just a thin hose going to the cylinder can reduce the travel speed slightly.

I don't know if can find any cheap ways of obtaining one but there are magnetic "actuators" out there.
Often used for locking machanisms but if in doubt "ancient" industrial relays can be modifed for this purpose too.
What happens is that with the inrush or current the magent will either push or pull on a core.
Travel distance is usually just around 1-2cm unless you make your own piston and add some strong neodymium magnets to it.
Would be the cheapest option if you can score a suitable electromagnetic actuator or old and big relay.

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OneDadAndHisGirls

4 weeks ago

Maybe if you could simplify it using springs and a quick release trigger or pull cord? The sketch isn't beautiful but it's easier to doodle to show than use words imho :)
Whichever method you devise, all the power to you!
I would calculate in the weight of transport if this is something you would be putting away between uses or taking with you for change of background. Simple design equals simple fix in case something happens that's less than desirable.

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PaulL320OneDadAndHisGirls

Reply 4 weeks ago

Yes an aluminum profile frame with a platform on ball bearings might be an easier solution as the Downunder has given me enough information on pneumatics to make me suspect it might require too much pressure to do this on a rig that should be able to be moved from the studio.

Thank you so much for the sketch! Will certainly consider this approach!

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Toga_Dan

4 weeks ago

Co2 is at 800psi at room temp. I suggest a small compressor, or even portable air tank instead.

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PaulL320

5 weeks ago

Thank you for the reply!

Here's my reasoning to use a cylinder.

Exact control and that is needed when having a laser that will trigger a camera with a precision of a 100um.

I would really like to start the action electronically and with precision, Once the setup is done this will be a requirement anyways.

The surface need to be hard, it needs to be able to control at which angle the objects fly up in the air.

Thank you for taking the time!

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Toga_DanPaulL320

Reply 4 weeks ago

100 um... remind me... um means micrometer? Decimeter? I forget

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PaulL320Toga_Dan

Reply 4 weeks ago

Your not the only one, i mean us not um. Time vs speed. .-)

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Downunder35m

5 weeks ago

Why not just use some rubber band and a lever?
Not that easy to get an instant push from air cylinders but quite easy if you let a lever bang under the platform.
Especially if said platform would be a stretched rubber surfce...
Like a drum....