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Volumetric Measuring Tool

Volumetric Measuring Tool

Volumetric Measuring Tool

(OP)
Is anyone aware of an inexpensive tool or device that will allow me to measure the volume of an irregular shaped space (i.e. glove box)? The tried and true method of ping-pong balls is not very accurate and is difficult to perform on vehicle cabinets that are open in the vertical position.

RE: Volumetric Measuring Tool

similar idea, use 1/4" or 1/2" styrafoam balls.  If the volume can hold some weight, place a plastic bag in the volume and then fill with water, measureing how much water it will hold.
Or put a plastic bag in the volume and spray in foam.  Remove bag and measure foam by water displacement or by weight (1 cubic ft foam weight .76 pounds, the foam block weights 1.52 pounds, the volume is 2 ft^3).
If one dimension is linear, then measure the area of the irregular by graph paper or weight and multiply the area by the linear dimension.

RE: Volumetric Measuring Tool

I am assuming you don't have a 3D model of the part you need to measure volume of.  Most modeling programs have a volume calculation.

Do you have the part by itself?  If it is a glovebox, I would seal it and submerse it in water.  Just measure the volume of water displaced.

I don't know how accurate of a measurement you need, but keep in mind that the above method will include be the exterior volume, not the interior volume of the glove box.  

-Reidh

RE: Volumetric Measuring Tool

(OP)
Unfortunatly, we are measuring competitive vehicles and don't have the CAD drawings. Also, because these storage bins and cabinets are installed in the vehicles we can not remove them to perform water volume tests.

If only the volume of air could be measured like water we could place a baloon type device in the empty compartment and inflate it to fill all the voids. Any thought along these lines?

RE: Volumetric Measuring Tool

Take a long bag, similar to a dry cleaners cover, and invert it.  Close the bottom portion inside the glove box and begin filling with water.  Water will slip between the door crack and fill the bag, albeit slowly.  5-10 minutes later when the water no longer enters the box you'll have what you need.

Where's the complication in this method?  How accurate would you need?

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Volumetric Measuring Tool

Quote:

If only the volume of air could be measured like water we could place a baloon type device in the empty compartment and inflate it to fill all the voids. Any thought along these lines?

Get a 'Balloon', it will need to be a fairly tough one which when fully inflated is quite a bit bigger than the space you are measuring.

Place in glove box (or whatever).

Almost close glove box, leave open just enough to either pull the 'valve' of the balloon out or maybe put some small dia tubing to the balloon.

Inflate the balloon to just over atmosphere.  You want it to take up all the room but not build up much excess pressure.  It may be better to evacuate the air from between the outside of the balloon and the walls of the glovebox but making a seal like this may be difficult.

Seal balloon.

Pull out the 'inflated balloon'.

Imerse in water, the water needs to be up to the top of the pan or spigot.  You need to make sure and not immerse it too far or the water pressure will compress the air.  I'm thinking a large but shallow pan.  Maybe push the balloon down with a large board or something so it can spread out but not be submerged too far.

Measure the displaced water.

I'm pretty sure I missed something.

If the water insists on compressing the ballon you could put a pressure gauge on the balloon to see how much and compensate to adjust the volume.

The balloon wont actually be a ballon, I'm thinking something like the heavy duty bags they use in shipping or something.


Sounds mighty complex, someone must have a better idea.

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

Reminds me of Archimedes and the king's crown.  ;]

CODE

http://www.crsep.org/PerplexingPairs/Jan.%2022.2003_Archimedes.pdf

==========================================
Business Site     http://mech.e.tripod.com
------------------------------------------
Cycle Utopia.......www.tailofthedragon.com

RE: Volumetric Measuring Tool

OK,

If you use the pressure gage you don't have to worry about how far under the water you immerse it etc.

p1v1/t1=p2v2/t2 as I recall.

There must be a better way though.

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

Kenat,

You stated "Inflate the balloon to just over atmosphere"  

What difference does the inflation pressure make?

Reidh

RE: Volumetric Measuring Tool

Well ideally it would be inflate to atmosphere but this wouldn't push out the air between balloon skin and compartment.

I propose measuring the volume by displacing water.

If you don't use the pressure gauge then as air is compressible the water pressure would compress it as the balloon is submerged this would effect your volume measurement.

If you compensate for pressure difference with a gage reading both in the glove box and submerged in water then you're home free and can inflate to well over atmosphere to fill the gaps.

I'm thinking filling macgyvers2000 bag with dcastos balls (only maybe the really small ones like in bean bags) may be a better idea.

(macgyvers2000 & dcasto, that wasn't a joke at your expense)

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

Hey, I'm all for the bean bag beans idea... whatever gets the job done, and if you spill those a vacuum cleaner takes care of the mess.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Volumetric Measuring Tool

Leaving the practical realm and heading into the theoretical world, you could seal the glove box so that it is airtight with the exception of an air-hose quick disconnect fitting.  Using an air tank of a known pressure and mass, hook it up to the glove box until the tank and glove box are in equilibrium.  You would know the air pressure in the glove box (same as air tank), and the mass delta of the air tank by weighing it after it has reached equilibrium with the glovebox.

From this, you could calculate the mass of air in the glove box, the density of the air in the glove box, and thus the volume of the glove box.

This would be a huge pain to perform, and you would need fairly accurate measuring equipment.  But if you have an excess of time and money, I would highly recommend this method.

-Reidh

RE: Volumetric Measuring Tool

1.  Place a plastic liner in the cavity.
2.  Squirt expanding foam sealant into the cavity.  I suppose that I would try to get the softest version of that stuff from the <Home> supply <Depot> store or equivalent.
3.  Cut out the foam block without destroying too much of the volume.
4.  Put foam pieces into a container of known volume.
5.  Fill the container to the level mark with water.
6.  Remove the foam blocks.
7.  Do the math:  Max- Remainder = Cavity Volume.

TygerDawg
Blue Technik LLC
Advanced Robotics & Automation Engineering
www.bluetechnik.com

RE: Volumetric Measuring Tool

Why do you need to know the volume??

When you get the data what are you going to do with it??

RE: Volumetric Measuring Tool

Probably put it in a sales brochure.

Our vehicle has 25 cubic feet of storage, the competitor only 19.

Or use it as a design target to exceed for the same reason.

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

What about sand?  Fills just about everything, easy to pour, easy to measure, easy to vacuum out, and fairly easy to reclaim from a vacuum cleaner.  Blowing it in to vertical areas might be a bit tricky, but getting it out is certainly easy enough.  And it's cheap...which makes accountants happy.

Not the most accurate of methods, but I figure it would get you close enough?  

RE: Volumetric Measuring Tool

I suspect the OP is measuring the luggage capacity of hire cars in order to benchmark them. Filling them up with sand is not going to make many friends!

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Volumetric Measuring Tool

Yes...but it could be an excellent prank, albeit an expensive one!  For some reason I saw the word "glovebox" and went with it.  Now I see why the styrofoam ball comment was made.  I learn something new everyday in these forums.

RE: Volumetric Measuring Tool

Smaller spheres will be more accurate as the size of the sphere reduces, at some point this becomes trivial.

You can also estimate the packing efficiency of any size sphere.

This really isnt that complex, it all depends on the accuracy that you need from teh measurement, I'm sure that 1/4" beads would provide accuracy to <0.25ft^3.

I wouldnt use styrofoam, the static charges would just be annoying.

RE: Volumetric Measuring Tool

Small balls in big bag in glove box or other space (as I previously mentioned).

What I didn't make clear before:

Seal bag, 'burping' excess air.

Place bag in displacement tank, no need to measure packing efficiency.

Ta-da.

So what did I miss?

You maybe be able to do the same with sand but it will be heavy, and if the bag tears will be more difficult to clear up, probably.

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

Guys/gals... the OP made only two posts within two hours of each other, and nothing for nearly three weeks.  I think we could say this thread is dead.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Volumetric Measuring Tool

(OP)
I am still following the feedback here. However, I've yet to see a solution that is either easy to execute in the field or simpler than the ping-pong ball or bean-bag appraoch. Unfortunatly, I am going to be measuring the interior cabinet space of heavy-duty trucks and motor homes, both of which have some very large and very irregular storage cabinets. In some cases, I would have to use several hunderd ping-pong balls and counting these would be really impractical.

RE: Volumetric Measuring Tool

Use the principle of the helium pyncnometer which will measure the true density of sand particles or just about anything else.

Use air to inflate a very thin plastic bag (e.g., garment cover from the laundry) into the volume so it is filled. Inflate to a known pressure, perhaps 10 inches water column (w.c.) to fill the void, then deflate to 1" w.c. Then use a simple syringe to inject a known additional volume of air (e.g., 100 ml). Measure the pressure increase, say 2" w.c.

From the known volume of air injected into the unknown volume of the bag and the measured pressure change you can easily calculate the unknown volume. Correction should be made for temperature changes.

A slanted tube mannometer can accurately and inexpensively read measure these pressures. No mess to clean and gravity is not a problem.  

RE: Volumetric Measuring Tool

A measuring tape and a bit of reasonable estimation can actually get you quite close most times.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Volumetric Measuring Tool

OK, so you don't like the water displacement idea (in any of its forms).

How about hand held laser scanners.  There is at least one, possibly more, on the market which I believe allow you to scan an items geometry and then create a solid model from it.

It should then be possible to interrogate this model to get a good approximation of the volume.

Not sure if it would work for your kind of thing but worth looking into?  I had an email with some details but can't find it now.

KENAT, probably the least qualified checker you'll ever meet...

RE: Volumetric Measuring Tool

Think
 
1.  Tracer gases -put a known quanity of gas into your volume and then measure the concentration (by some electronic detector means).

2. Leak detector technology that use gases

Maybe these people(or similar companies) could give you some guidance.

http://www.lowener.se/e/Helium%20leak%20testing%20systems.htm

RE: Volumetric Measuring Tool

Empty cardboard boxes for the bulk of the space and ping-pong or Styrofoam balls for the remainder.

RE: Volumetric Measuring Tool

How about pouring semi-flexible foam into the cavity (inside a bag). After the foam sets, remove the foam (either in one piece or in sections). Bag the foam. Measure the volume by displacing water in a bucket of water (measuring by weight of displaced water or measuing the volume of overflow.

RE: Volumetric Measuring Tool

"counting these would be really impractical"

Often small parts are 'counted' by mass rather than unit.  Several hundred ping pong balls should be weighable on a tabletop balance.  If you use competition-grade balls (??) they should be very uniform mass.

If loading them into vertical compartments is too tedious then you should employ more engineering interns.

RE: Volumetric Measuring Tool

Place the vehicle on a huge scales, then fill the compartment with a material of known density and re-weigh.
The heavier the material the better as any scales large enough to take a campervan is likely to have a poor resolution.

RE: Volumetric Measuring Tool

"A measuring tape and a bit of reasonable estimation can actually get you quite close most times. "

No kidding!  As a consumer, not an engineer, I would say the total volume is not the metric anyway; it's how useful the shape is, how accessible, how well lit, etc. If one glovebox is 2 cu. inches bigger but it's an odd shape that collects lint and is hard to clean, I am not impressed.  Not that I've ever even looked at a glovebox when considering a purchase....

RE: Volumetric Measuring Tool

There is an ISO standard collection of luggage for that very reason.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Volumetric Measuring Tool

I have used sand in a garbage bag many times before to measure cavities into which I wish to build speaker enclosures.  In the case of audio work, getting really close was good enough, but if you just want a 98% estimate, use sand.

In some cases, I just put the bag in the cavity and fill it with sand.  For more progressive curves and cavities that does the trick.  If you have oddly convoluted shapes, what I suggest is using a light-duty "repositionable" spray adhesive on the bag.  Then you can poke it into odd shapes and have it hold in place.  If you don't, you can't be assured that the bag is fully displacing.

To add accuracy, I will use an air hammer with a custom-made flat anvil to settle the sand, then after I pour the sand in a measuring vessel I use the air hammer again to make sure its leveled out similarly.

Perfect?  no.  Super close?  yes.

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