Author Topic: Model Compressor---Maybe  (Read 24191 times)

Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #15 on: December 01, 2017, 10:15:09 PM »
Hoo Boy----

Offline 10KPete

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Re: Model Compressor---Maybe
« Reply #16 on: December 01, 2017, 11:04:52 PM »
I think that would make a fine, low pressure, compressor, Brian. Might be fun.

Pete
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Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #17 on: December 02, 2017, 01:22:18 AM »
I'm going to need 8 of these guys. Four for air being sucked into the cylinders to keep it from flowing back out when the piston reverses it's travel, and four for air going out of the cylinder to the balloon to prevent the air flowing back from the balloon into the cylinder. The "incoming air" units are all "stand alone". The "outgoing air" units will all be plumbed to a common spigot where the balloon attaches. There is some "gravity effect" with this type of valve, so all eight will have to be installed "right side up".

Offline Gas_mantle

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Re: Model Compressor---Maybe
« Reply #18 on: December 02, 2017, 01:59:59 AM »
Should be an interesting project Brian, I'll be interested to see how it performs.

What sort of bore/stroke do you envisage ?

Offline MJM460

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Re: Model Compressor---Maybe
« Reply #19 on: December 02, 2017, 03:09:08 AM »
Hi Brian,

Looking like another one of your great projects.  I will be keenly following along.

I am sure that you know this, but I thought that I would just add a comment on the difference between a pump and a compressor in case anyone else would also like to make a similar compressor.

There are just two differences, the intent of the designer, and the clearance volume.

The intent of the designer determines how much torque is required to turn the shaft and how much speed is required to get the required flow, so determines the driver specification.  Also how much temperature rise in the fluid as it passes through the machine.

But the only difference in the actual machine is the clearance volume.  For a pump, clearance volume does not matter, although it can limit the ability of of the pump to handle a little bit of air or vapour.  For a compressor, the ratio of the clearance volume to the total of clearance volume plus swept volume is an absolute upper limit to the pressure increase that can be achieved.  In addition, that same ratio determines the flow for each stroke of the piston.

It is important for a compressor that those ball valves are located as close to the cylinder as practical, so as not to unduly increase the clearance volume.

MJM460




The more I learn, the more I find that I still have to learn!

Offline Jasonb

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Re: Model Compressor---Maybe
« Reply #20 on: December 02, 2017, 07:34:24 AM »
Brian if you don't want to make 8 valve assemblies you could leave one end of each cylinder open and then just have single acting pistons which would only need two valves per cyl, think IC engine pistons rather than steam engine pistons that you have now. It would mean less air volume but would reduce the load on the engine that is running the compressor.

You could even fit flap valves to the top of the pistons and do away will all 4 of your valve assemblies, go and look a a bicycle pump which has similar simple valves and is single acting

Offline Ian S C

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Re: Model Compressor---Maybe
« Reply #21 on: December 02, 2017, 10:14:10 AM »
I used a Scotch Yoke on my first Stirling Engine, A V type GAMMA motor with success, and also on a water pump driven by another of my motors.
Ian S C

Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #22 on: December 02, 2017, 02:48:24 PM »
Well---That certainly looks interesting!! I have never built a Scotch Yoke mechanism before. I can recycle three of my gears and one large pulley from the "Auto-reversing mechanism" that didn't work.

Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #23 on: December 02, 2017, 02:54:42 PM »
Should be an interesting project Brian, I'll be interested to see how it performs.

What sort of bore/stroke do you envisage ?
1" bore and 1" stroke.

Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #24 on: December 02, 2017, 03:46:26 PM »
That should do it---

Offline Florian Eberhard

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Re: Model Compressor---Maybe
« Reply #25 on: December 02, 2017, 04:10:12 PM »
Hi Brian

For a Compressor in such a small size, it is crucial to keep the dead volume as low as possible - at least if you want your compressor to be efficient.
And i think it is also advisable to enable only very few movement of the ball in the clack valves (so the valve losses are as small as possible)

Cheers Florian 

Offline crueby

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Re: Model Compressor---Maybe
« Reply #26 on: December 02, 2017, 05:53:46 PM »
That should do it---

Must be pumping helium, it took off!!

Another fun project to watch...

Offline Flyboy Jim

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Re: Model Compressor---Maybe
« Reply #27 on: December 02, 2017, 06:16:43 PM »
That should do it---

Must be pumping helium, it took off!!

Another fun project to watch...

Fusion 360 users "OUT OF CONTROL"!  :lolb:

Another fun "Brian Project" to watch.  :popcorn:

Jim
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Sherline 5400 Mill
"You can do small things on big machines, but you can do small things on small machines".

Offline Bobsmodels

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Re: Model Compressor---Maybe
« Reply #28 on: December 03, 2017, 01:52:26 AM »
Hi

Here is a little steam scotch yoke engine (coles castings).  I used to pump up balloons with it and hand them.  I was advised to stop doing it as a child could choke on a deflated one.  I could probably just pump one up on a valve that could deflate it and inflate, might be fun demo.

Bob

Offline Brian Rupnow

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Re: Model Compressor---Maybe
« Reply #29 on: December 03, 2017, 02:03:56 PM »
So, I have all the reclaimed "odds and sods" from the auto-reversing mechanism that I never got to work. I can re-use two of the bras gears, the dark steel gear, the large pulley and the round part with three smaller holes in it at 120 degrees apart. I will also re-use the rack and flatbar, but not on this project.

 

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