CO2 Propulsion Question

[bclemens]

Hello, all,

As I approach the last part of the Gandy Dancer (http://www.papermodelers.com/forum/showthread.php?t=1506) design I am firmly convinced that the technique of building mechanical models using a hybrid of paper/card and brass tubing has the potential of creating very interesting functioning models.

My thoughts keep going to replica steam engines driven by CO2. Not only desk-top models but possibly portable units driven by small bottles that are readily available in sporting goods stores.

http://www.papermodelers.com/gallery/data/500/thumbs/co2.jpg (http://www.papermodelers.com/gallery/showphoto.php?photo=1222)

Why CO2 and not electric? I think there is something very appealing about having the model operate by pressure just as with the real thing. And the sound would be very authentic.

I think this would also appeal to boat modelers and possibly large scale railroad modelers. I hope that a model engine, well throttled down, could run for quite some time on a small CO2 bottle.

The power chain would of course require:
CO2 bottle--> Regulator--> needle valve(throttle)--> interface to model

Do any of you know of some off-the-shelf components that could be cobbled together to produce an effective system that would do the trick? Of course the cheaper the better...;)
I expect final pressure necessary to drive the model would be fractional to very low PSI.

Thanks for your input.

Cheers!
Bruce

[John Bowden]

Not sure if this would fill the bill..............

what about those "cheap" airbrush units.......... they have the valve, hose and a larger supply of compressed "air" . You might be able to MacGyver something from them.

john

[Gil]

Bruce, The only manufacturer that I know of that's still in business is Gasparin Motors. They aren't your low cost solution though:

http://www.gasparin.cz/?show=frames&lng=en

And can be purchased through this distributor:

http://www.peck-polymers.com/html/Specials.asp

A geared electric DC motor would be a better choice from a cost and application standpoint. Besides, Gandy Dancers weren't steam powered...,

+Gil

[Jim Nunn]

How about a small aquarium air pump with a needle valve. You can’t control the pressure but you can control the air volume. Cost should be under $20 from one of yhe internet pet supply stores.

One disadvantage that comes to mind with CO2 is the low temperature produced when the gas expands this could cause problems with paper shrinkage.


Jim Nunn

[bclemens]

Much to think about, gentlemen- thanks for your input. John, I hadn't thought about airbrush units- that is worth looking in to...

Gil, those Gasparin motors are truly jewels. they would be worth having just to look at.

Jim, the aquarium valve may be just the ticket- unfortunately, as you said, it does nothing about the high pressure. The temperature issue comes, of course, from the expanding CO2 in the motor. Naturally in a real steam engine this expansion is useful- the cooling of the expanding gas in the cylinder delivers power to the piston. What I envision would be a paper/brass motor whose motion comes more from the motion of gas that is already expanded. Thus there would be little temperature differential.

I was successful years ago in building a small brass engine that ran well on breath pressure when I blew into a tube. This is the idea I want to capitalize on using CO2.

What I need is low pressure gas, already mostly expanded, with a variable flow rate. Perhaps between the aquarium, beverage, and paintball industries, there is still a simple solution out there ;)

[Oliver Weiss]

No, no, no - this is what you want: http://www.ministeam.com/acatalog/Ready_To_Run.html

Oh, get me one while you're there, willya?

Cheers,

Oliver

[bclemens]

Wow! Beautiful! At one to five thousand USD per unit, perhaps I'll buy one for each member of the forum, OK? ;)

Well, the idea here is to create a model out of card and brass tubing that looks much like one of these, runs much like one of these, but can be had for about 5% of the cost of one of these. Can we do it? We'll see...

Cheers!
Bruce

[maurice]

I wonder if he's quite ready for it Oliver. We know he's been reading too much Geoff Deason but he may not yet know about Deason successfully sailing steam powered cardboard boats in the 60s.






Mind you, I glad he's going to get one for me too. :D

[bclemens]

Maurice,
I am of the opinion that one can not read too much G.H.Deason ;)

I would like to learn more about
Deason successfully sailing steam powered cardboard boats in the 60s.

What can you tell us? Is there insight regarding the motors that can help in my quest? Keep in mind that I am not trying to build a paper steam engine. I am trying to build a hybrid paper / brass CO2 engine that looks and acts like a steam engine.

Cheers!
Bruce

[Don Boose]

I'd like to know more about Deason steam-powered boats, too. I keep my 1958 copy of Deason's Cardboard, Scissors, and Paste Engineering on the shelf above my writing desk/paper model workbench for inspiration (I have yet ever to successfully build any of his models, but I love to browse through the book).

All of the steam engines and ships in that book are actually powered by electric motors. I wouldn't be surprised to find out that he actually put a live steam engine into a ship model, but I've never seen or heard of one.

Don

[maurice]

Next thing you'll be telling me you haven't already read the Cardfaq in it's entirety.:)
http://bellsouthpwp.net/n/8/n8hfi/card-faq/
... /Find on this page ...Ctrl+F/Deason
and see what Rob Pounds had to say (perhaps as long as 10 years ago now).

I doubt I still have any trace of "Model Boats" for July 1975 but will look.

From
http://www.myhobbystore.com/ProductDetails/mcs/productID/1887
it looks as if Deason had at least a Mamod ME 1 marine engine
http://uk.geocities.com/rolywilliams/mamod_me1.html
... not a very powerful unit

Now for my (probably defective) memory of it.
The model was a very semi-scale freighter which may have been about 3 foot long and with exagerated superstructure openings to give adequate engine ventilation. Construction I think was basically a toughened and enlarged version of that used in "Scillonian". Compact radio was still in it's infancy and was not fitted.
Yes it made it across one of the famous London ponds.

This isn't much direct help to you but thanks for clarifying your objective Bruce. I agree with Jim Nunn's suggestions and also with the notion that you cannot read too much G. H. Deason.

Can you (or anyone else) tell me how much I paid for the book in 1959 ? It may be written as something like 10/6 on the dust cover, which I no longer have.

[Don Boose]

This person admits his guilt. I have not read the Carfaq in its entirety.

Many thanks for these leads, Maurice. I will dig into my Model Boats collection. I just may have the July 1975 issue.

Do you remember the series by the chap who built the Revell clippers with tissue paper sails and sailed 'em across the nearby cow pond?

My copy of C,S & P was 12/6.

Don

[bclemens]

Thanks for the links, maurice- very insightful. And the cardfaq is an oft-forgotten source of great information. Thanks.

My wife has a CO2 bicycle tire inflater- that may be a good place to start in terms of a MacGyver thing...that feeding into a needle valve might do the trick.

[John Bowden]

The tire inflator struck a cord............ I've also seen an "air duster" that use the CO2 cartridges to clean out computers and keyboards............. maybe this could be something else to look at, since it uses a trigger to control air release.

[bclemens]

I took a trip to a local well-equipped hardware store the other day and here's what I came back with:

http://www.papermodelers.com/gallery/data/500/thumbs/IMG_3821.jpg (http://www.papermodelers.com/gallery/showphoto.php?photo=1247)

On the left you see (broken down) my wife's CO2 bike tire inflater. I got her permission to use it by promising to replace it with a better one ;)... Then comes a Schrader to 1/8" NPT fitting, followed by a 1/8th NPT needle valve followed by a 1/8 NPT to tube fitting, followed by 5' of plastic tubing, followed by my prototype test-motor.

The test-motor has a little more work to do on it, but here is the heart of it:

http://www.papermodelers.com/gallery/data/500/thumbs/IMG_3819.jpg (http://www.papermodelers.com/gallery/showphoto.php?photo=1246)

The cylinder is in the middle, the slide-valve is on the top, and the piston is on the bottom. Attached to the cylinder is the slide-valve tube. There is a small hole connecting the slide valve tube to the cylinder. Note here that there is no soldering involved. The slide-valve tube is adhered to the cylinder using CA and followed up with paper and white glue reinforcement wrapping.

The slide valve and piston are both plugged on the end with cardboard sealed with CA. The slide valve was drilled behind the plug in several places to allow a path for the cylinder pressure to escape when the piston is coming back toward TDC. This being a simple one-ended motor, all I need in the valve is to provide a head of pressure to the cylinder just at TDC, and allow the pressure to escape the cylinder after it bottoms.

I am using Inkscape and Sketchup to help me find the right places and lengths for the connecting rods and cam...

http://www.papermodelers.com/gallery/data/500/thumbs/Engine1.jpg (http://www.papermodelers.com/gallery/showphoto.php?photo=1244)

http://www.papermodelers.com/gallery/data/500/thumbs/Engine2.jpg (http://www.papermodelers.com/gallery/showphoto.php?photo=1245)

I'll keep you all posted on the developments as they arise!
Cheers!
Bruce