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Engine Demonstrator Compressor Project

An HPLV compressor?

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Speedy Builder510/03/2014 14:11:39
2878 forum posts
248 photos

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

JasonB10/03/2014 15:11:35
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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 Wyatt10/03/2014 16:17:53
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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 udall10/03/2014 17:29:30
2032 forum posts
41 photos
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 udall10/03/2014 17:32:09
2032 forum posts
41 photos
By the way. .what about wallpaper/cappuccino coffee maker steam generators with suitable condenser
Neil Wyatt10/03/2014 17:47:40
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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

RRMBK10/03/2014 18:18:02
159 forum posts
18 photos

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.

Michael Gilligan10/03/2014 18:56:06
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23121 forum posts
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Posted by JasonB on 10/03/2014 15:11:35:

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.

.

Jason,

A serious question [although I don't want it to take the thread off-topic] ... Do you think any of the ME suppliers could actually sell a casting kit for a price that competes with those ready made pumps?

MichaelG.

JasonB10/03/2014 19:13:18
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25215 forum posts
3105 photos
1 articles

No I doubt it very much and by the time you have added some barstock, bearings etc it would cost more than you can go out and buy one for. The same could be said for a lot of projects in MEW you can order one over the net for less than it would cost in materials etc but that does not seem to stop people wanting to make things.

J

DrDave10/03/2014 19:40:38
264 forum posts
52 photos

Brian's mention of scuba made me think of an industrial nitrogen cylinder: large volume at some 300 bar should keep a V10 going for a few minutes. But (one of the) obvious problems would be controling the temperature if the flow was too high. And the safety of all that stored energy.

Michael Gilligan10/03/2014 19:53:41
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23121 forum posts
1360 photos

I suppose this is as good a time as any to post a link to the HSE pages.

This seems a good place to start any investigation of the regulations.

And ... For those who might enjoy loophole-spotting;

there is an interesting "Exception" listed on that page !!

MichaelG.

.

Edit: Just realised that Neil has already posted a link to the book.

Edited By Michael Gilligan on 10/03/2014 20:00:53

Steve Withnell10/03/2014 19:56:15
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858 forum posts
215 photos

I found some piston based aquarium pumps claiming 60 litres of air per minute at upto 20 PSI. £49.95.

They would have to be quiet, because of location, not sure how "smooth" the supply would be, or how to smooth it if indeed it was "lumpy"!

If my maths is any good, each rev on a single cylinder Victoria would require 0.5 litres and a good speed for this engine is 100rpm, so 50 litres per minute. My Victoria will run at less then 10PSI.

So unencumbered by knowledge and experience - this should work?

Steve

JasonB10/03/2014 20:06:30
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25215 forum posts
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Steve not sure how you got there but I recon 3.15cu in which is about 0.05lts  or 50cc per rev.

 

Can someone check my maths - 1" bore x 2" stroke

0.5 x 0.5 x 3.142 x 2 = 1.57

1.57 x two as its double acting = 3.15 or 0.05ts using online converter

 

I've got an 80lts airpump on my koi pond gets a lot louder when there is a restriction or the depth (pressure) increases and runs hotter

Edited By JasonB on 10/03/2014 20:08:14

jason udall10/03/2014 20:38:23
2032 forum posts
41 photos
Neil..my guess would be three at 120degree but if not would like to know reason for 135..
Michael W.if I have in someway offended please pm me and I will try to understand where

Neil Wyatt10/03/2014 20:53:33
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19226 forum posts
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86 articles

> Neil..my guess would be three at 120degree but if not would like to know reason for 135..

Probably that I'm stupid. I added 45 to 90, instead of dividing 360 by 3.

I think Michael has slightly crossed lines. I can guess who he's complaining about, but that person appears to have made no contribution to this thread?

Neil

WALLACE10/03/2014 21:45:37
304 forum posts
17 photos
WRT my earlier ramblings on simple aquarium pumps, I've found the make -it's 'Hy-Flow' ( or rather was - they're no longer made ).
They do seem to be highly regarded and go for silly money second hand !
W'
jason udall10/03/2014 21:53:16
2032 forum posts
41 photos
Wallace..that seems to be a common event...good things disappear..weak rubbish prospers..
dcosta10/03/2014 22:55:10
496 forum posts
207 photos

Hello Wallace, good evening.

About the Hy-Flow pump...

You could have avoided some work if you had read the message I addressed you on this thread yesterday at 21:08:03.
And I would have been a little happier for someone to recognize my contribution with some information for the matter under discussion.

Best regards
Dias Costa

WALLACE11/03/2014 07:35:25
304 forum posts
17 photos
Hello Dias.

Indeed, I would have done all those things if I had seen it.

Unfortunately, my browser goes to the last page of posts so it's easy to miss replies if they're near the end of the previous page.

And I don't have the reply notification email box ticked as I try to limit how many emails I get - a few days off work and it's depressing to come back and find there's hundreds in there !

W.
Ian S C11/03/2014 11:25:43
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7468 forum posts
230 photos

I opened up the case of the little medical compressor today, it is a diaphragm type. The diaphragm is 2 5/16" diameter, by about 1/16" thick. The stroke is 1/8", the crank is formed on the end of the motor shaft. the motor is a 1450 rpm shaded pole type, could not see the specs, probably between 150 and 200 Watts, and that's about it.

A suitable compressor would (in my opinion) have a similar motor, a diaphragm about 3"/3 1/2" diameter, a stroke of around 3/16". I'm not sure what sort of valve is in the pump, probably a reed valve. Ian S C

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