Engine Demonstrator Compressor Project

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Neil ,

(1) Air supply needs to be reasonably even so that means a receiver or more than one active cylinder end . Easiest is to have at least two cylinder ends direct flow .

(2) Flow calcs are piddlin easy but complete waste of time on a project like this . If swept volume of compressor is generously greater than that of engine and running speeds about the same that will do . Simple pro rata if running speeds mismatched .

(3) Rex Tingey (spelling ?) described a very neat small compressor ME 1970/80 period .

(4) There has been a pre assumption of traditional designs with motor and crank etc . If this is actually going to be a collective design project then start with blank sheet of paper !

How about:

A swashplate compressor .

A rotodynamic compressor – just for the hell of making it work (not that difficult) ?

A free piston compressor actuated by either a solenoid pair or a true linear motor winding ?

A chemical gas generator – Co2 ?

An MHD actuated mercurial compressor ? Not a serious suggestion – more a thought seed .

Regards ,

Michael Williams .

Edited By MICHAEL WILLIAMS on 09/03/2014 22:58:52

[Michael GilliganParticipant @michaelgilligan61133]

Posted by MICHAEL WILLIAMS on 09/03/2014 22:49:24:

(4) There has been a pre assumption of traditional designs with motor and crank etc .

.

Michael,

… by some contributors.

MichaelG.

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Diaphragm , bellows , Wankel principle , Roots principle , gear pair (and inversions) , radial vane , screw pair , wobble cam pair , Tap water actuated accumulator/displacer , Hot air engine free piston .

Or what about an ‘on demand’ boiler like a modern combi boiler or older type Geyser ?

[jason udallParticipant @jasonudall57142]

Given.
Pressure 30psi
Delivery (20 cc at 100 rpm)..2000 cc/m or 2l /min..
Quiet..
Prime mover electricity (assume mains)
How about solenoid /piston combo..
2 l/min is 2/3 cc per sec
Plenty of solenoids of that scale without even needing to wind coils…..

###
===== ==<===
HH |=====?
===== ===>==
###

##…coil

HH piston/magnetic slug

Edited By jason udall on 10/03/2014 00:00:15
Looks like that diagramme mangled…

Edited By jason udall on 10/03/2014 00:01:30

[I.M. OUTAHEREParticipant @i-m-outahere]

Hi all,

I know of a company here in Australia that sells a modified car airconditioner pump that is then fitted to the engine of a 4WD so to be used to inflate tyres after lowering the pressure for driving or if you get a flat.
I wonder if this would supply enough volume for what you need ?
Could be driven by an electric motor / v belt set up.

Ian

[JasonBModerator @jasonb]

Neil as you say their is some valve lift at lower pressure sso losses need to be allowed for. Also as I mentioned in Allan's thread most compressors quote the displacement not the actual air delivered which is termed FAD and can generally be taken as about 2/3rds the displacement. You also need to remember that as the air is put under pressure the volume decreases.

As for how fast I run the Easton, this is a good example, speed being restricted by thealve but as the tank is used up you see me open up teh valve a bit more but it starts to slow again towards the end.

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 09/03/2014 21:24:02:

Any thoughts on making a piston to run in soil pipe?

Use the rubber off the end of a WC pan connector on a plywood piston.

[Clive HartlandParticipant @clivehartland94829]

Remember whatever method of air pressure you generate you will also get moisture/water in the lines. You will need water traps and an air dryer.

Clive

[Les Jones 1Participant @lesjones1]

The old idea of using a sealed unit type fridge compressor might work if it would deliver enough volume. I vaguely remember trying one over 40 years ago. The only think I remember is that it was capable of giving a pressure of about 300 PSI (This fact would suggest that it would not be capable of delivering the required volume.) I remember cutting the casing open to have look at the compressor and I think the cylinder was about 1.5 – 2" bore and about the same stroke. If it would deliver the volume it should meet the low noise requirements.

Les.

[michael coleParticipant @michaelcole91146]

I have a hand pump for inflating for boats/beds tha sort of thing. Dia is around 4 inch and the stroke is around 12 inch. All plastic and double acting, pumps on the down and up stokes. Around 100 pumps per min at max but you would need a replacement pumper after a couple of minutes at that rate.

[Ian S CParticipant @iansc]

I can run my wobblers off a 3lt garden spray pump, not sure what pressure, but it is a way of getting a arm exercise. Tried an aquarium pump, mine is a little box about 3" x 2" x 1 1/2", it has a rubber bulb inside, pressed by an oscillating armature, next to a 230V coil. No go with any of my motors, I use it to aerate my citric acid bath. It sits there and hums at 50hz. Ian S C

[JAParticipant @ja]

I remember the physics teacher at school blowing up kids' balloons with town (coal) gas by filling a container with gas (from a very low pressure supply), shutting off the tap on the container, attaching the balloon and then connecting the container to the mains water through a second tap. The water then forced the gas into the balloon.

I am not sure what the water supply pressure is but it has to be at least 16 psi. Could such as system, either directly into a receiver or to indirectly pressurise the receiver be used?

I believe that it is illegal to take energy from the mains water supply in the UK.

JA

Edited By JA on 10/03/2014 11:03:24

[jason udallParticipant @jasonudall57142]

Coffee break thought
.
Platform on “spring”.
Bellows( inner tube) under platform.

Viewer stands on platform and compresses innertube..generating enough ca for duration of view ( say 10 minutes)..step off and on if longer desired….
Look ma that demos interactive…

[Michael GilliganParticipant @michaelgilligan61133]

Posted by jason udall on 10/03/2014 11:02:19:

Look ma that demos interactive…

.

Nice one, Jason

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

MichaelW,

Excellent list of thought-provokers !

One more to add [unlessI missed it] … peristaltic pump

Typically used for liquids but; might work with Air.

MichaelG.

[Tim StevensParticipant @timstevens64731]

Has anyone considered a rotary compressor as used for cabin pressure or car superchargers?

And perhaps a Wankel engine – which could be used as compressor over both halves of its rotation.

Cheers, Tim

[Gordon WParticipant @gordonw]

Without knowing how much air is required and at what pressure it's difficult to suggest any thing, without being over moronic. A plastic pipe with leather washer, washers easily made, or buy sealing ring for the pipe. Water pressure could be used, it used to be used to pump beer in parts of Scotland. Think it would be OK legally as no water is used. Even a small pump with low volume output would be OK if a big receiver is used and plenty of time . I've run a little wobbler of a car tyre. Just a thought- would not similar regulations apply to air pressure as steam, in a public place?

[jason udallParticipant @jasonudall57142]

..directed at no one in particular.. (reading the thread i can’t find who any way ) …
With regard to moronic suggestions. .there is room for ( in this phase of development) all thoughts ( I have heard “blue sky thinking” used for this also “brainstorming”…)..
If this sort of open ended discussion offends well maybe start your own thread..include a suitable term in title..
As for me..once in a while ..dare to try new ( sadly few are new) thoughts..even you might learn something.

Edited By jason udall on 10/03/2014 14:06:28

[Speedy Builder5Participant @speedybuilder5]

To suit the 'Greens', use an exercise bike to power the pump – "If you want to see it go my boy, get on the bike and pedal fast."

BobH

[JasonBModerator @jasonb]

Do any of our American members know what system is used for the US shows such as GEARS and NAMES as they have an air supply provided to every display. I should think its a couple of big industrial compressors feeding into a "ring main" of pipework and more practical than a compressor on each stand.

What we need is for one of the ME suppliers to offer a casting kit for a pump like these then we can power it in whichever way suits, maybe belt it upto one of the traction engines outside.

[Neil WyattModerator @neilwyatt]

For clarity, the pressure systems regulations don't apply to pipework (i.e. pipes that don't leave a premises) that hasn't got a receiver OR systems with a working pressure of less than 0.5 bar (excluding steam).

Any system for other than personal use, e.g. at a show, would probably have to use a properly inspected compressor or be restricted to 0.5 bar/7 psi or the alternative is a pump that has smooth delivery of air and doesn't need a receiver.

**LINK**

I think there are two possible routes this could take:

1 a large rotary or three-throw pump to give smooth delivery of bulk air at modest pressure for use in public demonstrations. (i.e. an alternative to a bulky, noisy, commercial unit designed for high pressures).

2 a smaller pump designed for home building to power one large or several small engines in a domestic setting. (i.e. an alternative to small, noisy pumps that tend to provide low volumes at high pressure, rather than the reverse).

Neil

[jason udallParticipant @jasonudall57142]

If the delivery pipework is of sufficient bore and length. .it might function as enough of a receiver to sustain the model between compressor strokes….other wise the compressor needs to complete multiple strokes for each model stroke ( and more for multi piston models)..
Again a mains (think electro magnet ) solenoid oscillating a piston of sufficient capacity would serve….

Mad thing is much of the design effort is to meet the regs ( once they them selves are unravelled!)..rather than the real challenge. .*shakes head sadly*

[jason udallParticipant @jasonudall57142]

By the way. .what about wallpaper/cappuccino coffee maker steam generators with suitable condenser

[Neil WyattModerator @neilwyatt]

Hi Jason,

I deliberately didn't mention that the pipework could act as a receiver..

In theory three pistons at 135 degrees to each other will produce a steady pressure, if the valves are arranged right. In practice not really constant, but good enough I would guess.

I can't possibly comment on off label use of such products in my new role.

Neil

[RRMBKParticipant @rrmbk]

Hi Niel and all

I think your idea of the drain pipe and piston seems excellent, Piston easily sealed with a leather or light fitting O ring . In the UK you might want to consider the yellow Gas pipe which is larger diameter and very smooth bore, to reduce friction. It would also be more stable in the suggestion I am about to make.

Consider this in the context of Michael G’s accumulator. Say 2 mtrs long, standing vertically with a weight on the piston. Initially, fill it with air at say 1 to 1.5 bar. At the start of a demonstration period this could be done quickly with a battery tyre compressor if no mains available, or slowly with a quiet aquarium pump both of which you can obtain quite cheaply.

This will give you a large volume of air which you can tap off from near the base of the cylinder as required by using an outlet valve to control flow. For an exhibition, where mains is available keep the aquarium pump feeding into the accumulator via the top of the piston through a Non return valve .

A suitable pressure gauge on the accumulator and the position of the piston will give you a good idea of how the volume of air is holding up. If it starts to get low, stop the display engines for a while or shut down a few until the output from the aquarium pump is greater than the demand and your accumulator will recharge. Alternatively accept the noise for a few minutes and quickly fill up with the noisy air compressor.

If you are really lucky one of your club members may be a diver in which case you have a perfect silent solution. Blag a couple of their diving cylinders and regulator for the day and make a suitable connection to top up your accumulator from that at 1 bar or whatever safe pressure you intend to run at.

If your tube is 150mm dia by 2 M tall that gives approx. 1000 ltr , pressurise to 1 bar – that gives a useable say 700 bar ltrs – usage of 3.5 ltrs / min at 1 bar = 200 minutes or 3.5 hours. A Divers cylinder is approx. 1000 bar litre so two cylinders will keep you going all day. As an example, I keep a fully charged diving cylinder with suitable regulator and connector on my boat and it inflates my little Avon dinghy perfectly to about 20 psi.

If you have more engines stand more accumulators up in the bank and couple them together.

Just to keep the UK safety aspect in control PSSR is intended for equipment “ at work “ so as a club using it for public display I don’t think it applies, but if you get as far as considering the design viable it might be worth taking professional advice.

However common sense tells us that the amount of stored energy is pretty small and a pressure of 1-1.5 bar extremely unlikely to result in catastrophic failure, but you will need a simple pressure relief valve on the accumulators. New gas pipe is pressure tested and certificated in a manner that drain pipe isn’t. Divers cylinders are regularly tested and certified, and your electrical aquarium pump may need to be tested and declared safe.

I think the most probable incident is the discharge going full bore and the weight/ piston making a bit of a noise when it hits the bottom of the cylinder behind you giving rise to brown trousers syndrome!

Happy Hydraulics Games – and may the force be ever in your favour.

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