Compressor project(s)

[Gareth J]

That might work but you would need a tee with a one way NRV valve-- open to air to 'regenerate' the air in in the control line to the solenoid

That was the reason for plumbing it into the air receiver - plenty of air under pressure available to pop the unloaders.

 

[normspanners]

What does an air over oil solenoid look like?

they are actually called pilot operated valves but most people go-- HUH-------- so air operated solenoid sort of explains it ok

You could use a hydraulic one and just let air pass through the switched section but they are expensive
or just check a pheumatic one that it's seals are viton rubber and can stand oil

One possibility to show the principle these might be a little large though but shows the principle

Pneumatic Angle Seat Piston Globe Valves

Air operated 2/2 way and 3/2 angle seat piston globe valves are ideally suited for most general purpose, aggressive, corrosive, steam, thick viscous and contaminated dirty media applications up to 600 centistokes where standard solenoid valves would really struggle, fail or just be too expensive. Angle seat piston valves are available in stainless steel up to 3" BSP in stock and you can buy them online here. However bronze angle seat piston valves have almost become a redundant option due to the huge material increases for copper over the past years that have pushed Bronze costs closer to Stainless Steel. Plastic angle seat piston valves can have better chemical compatibility to stainless steel, but will suffer from lower working pressures and temperatures however engineers tend to prefer using stainless steel angle seat piston valves instead due to better reliability, performance and structural integrity.

Air operated or pneumatically controlled angle seat globe or piston valves are designed to work from a controlled compressed air supply, which is utilised to directly control the opening and or closing function of the angle seat piston valve. However just about any clean, inert non corrosive liquid or gas controlling media can be used so long as valve actuator and controlling solenoid valve materials on construction are suited.

The angle seat piston valve consists of two main parts the valve body and seals to control the media flow and the valve controlling actuator head that receives the compressed air supply, which are joined via a well packed (sealed) stem.

 

[normspanners]

That might work but you would need a tee with a one way NRV valve-- open to air to 'regenerate' the air in in the control line to the solenoid, because after a time the air would bleed away leaving a vacuum, and would not work, why use it though? just use an 'oil over air' solenoid valve would work as I had suspected

That was the reason for plumbing it into the air receiver - plenty of air under pressure available to pop the unloaders.

your not catching my drift------ this might explain it better

and the pipe to the unloaders would need to be vented from 'your ' valve when the pilot valve was energised to allow the unloaders to return to rest.
you can buy them that do that automatically

 

[normspanners]

PS you have the right cam override unloaders that allow you to manually override the air system for first starts to allow the pump to idle whilst it warms up then throw the cams to let it start pumping.
also you can try limiting it to one cylinder with them too.
I think you are very 'brave' to try to run an ac41 on single phase
mind you there are several meanings to 'brave'

 

[normspanners]

One thing you could do is restrict the air flow into the pump through a variable butterfly and have it adjustable and self limiting. so that it pumped less as pressure builds.
just use a old small car throttle body or --------which would be VERY impressive a bike carb !!!

 

[Gareth J]

Ah, sorry, that valve you've added is actually connected to what is supposed to be a solid bar in my drawing.

Thanks so much for all the pointers... I think you might be right regarding running this on single phase. Next practical step is to try running it with the motor I have. See if it even turns it over empty!

Have a lot if pondering time at the moment and minimal spannering time. Won't be wasted though as even if I put the old 3pg motor back on to sell it, the pump ought to function!

 

[penfold]

mind you there are several meanings to 'brave'

Like this?

 

[Gareth J]

Update:
I may have figured out how it once worked. In this PIC:
http://www.mig-welding.co.uk/forum/attachments/tmp_5710-img_20150510_101242-120065247-jpg.64925/

Above my finger is a bolt with a nut on it. When trying to remove it, I couldn't find any imperial nuts to fit. It's m10! On removal, it has been mangled into a matching oil way to the other side.

I think there were two oil pressure actuators, one for each side that popped the unloaders when oil pressure dropped off.

Also, my motor is a crap starter, won't start cleanly on its own, let alone attached to that flywheel. But on the occasion it does fire up, it will wind the compressor over onloaded. Putting this compressor on hold for now and concentrating on the big one. It's much more complete and should be a relatively easy fix.

 

[normspanners]

VOILA I found it!!! there is the reason for the inlet casting. I knew I'd seen hyd unloaders somewhere in the back of my cells.
BUT doesnt explain the diaphragm though, in your app.
The actuators in this application defiantly unload the cylinders till the oil pressure is up, there will be springs inside the cylinders pushing the acctuator pistons down, unloading the cylinders until enough oil pressure is felt under the piston to overcome the springs, any oil that passes the piston rings then is fed back down the drains into the royal blue oil filler /cover on the crank case at crankcase pressure ie 0 psi ish this leakage will allow the pistons to return to their rest positions when pump has stopped.

 

[Gareth J]

Think we're getting there! That diaphragm thing IS an actuator, there is a brass rod that pokes out the top which would (if it wasn't broken off) pop out when there was oil pressure.

Clearly, the unloaders I have don't accommodate a lever like the ones in your picture but this machine seems like a bit if a mix of parts.

Will plug it into my receiver and see what the motor is capable of on both/one cylinder.

 

[normspanners]

 

[normspanners]

Right it becomes clear, if you now look at my pic in post 20 you can clearly see the lever to the actuator on the other side of the compressor head, the diaphragms are a more modern method than the brass cyl's. IMO
what you are short of is the unloader valves similar to the ones in the pic above ^^ and the taper screw adjuster adjusts the time in which the oil pressure bleeds away, allowing the diaphragms to relax.
TFFT I have been wrecking my brain trying to fathom it .

 

[normspanners]

That is the setup you need lister peter, driving ac 41 smallish tank so pressure does'nt drop off too much before pump kicks in.

 

[Gareth J]

Yep, it's nice to have gotten to the bottom of the mystery inlet manifold oil gallery.

Yes, I think you're right, some kind of non electric power source has to be the way forward with this one, I need to buy too much stuff to try to work it with electric and even then, it'll probably be a non starter.

Attempting to rebuild the cracked caps on the big one tonight...not all smooth sailing.

 

[Gareth J]

Still plodding with this one. Ditched the motor. Found a nice 90° gearbox with an ideal 2:1 ish gear up.

Only trouble with that is, it's driving the pump backwards, one (or more) of the bearings in the 'box have gone and it means the pump would have to be way off centre.

However, I botched the pressure gauge onto the take off and it makes oil pressure backwards! So I'm thinking now the direction of rotation may not be critical.

In which case, all I need to complete the bodge is a flanged PTO stub to bolt to the flywheel, mounted in an a-frame (think the scrapheap may be able to yield that) and were getting somewhere.

Will have to be run with a tractor that has a 1000 output gearbox unless i want it screaming but that's not a problem.

 

[Gareth J]

Flange. Hoho

Can also make out the unloader actuator peeking out from behind. It's from the other compressor.

 

[Gareth J]

+ tank + frame.

Hopefully the air will have so much momentum it'll just shoot on into the receiver vessel

 

[Gareth J]

It works!

The unloader mechanism is a joy to watch in operation, it fires, the unloader valves pop, the machine idles and the tractor eases off. When pressure drops, they close off again, the tractor grunts and it charges up.

Will run an open 1/4" fitting at 5 bar at around 600 shaft rpm. Compressor should be good for 710rpm so has more to give.


I turned it up to 150psi - the compressor's stated max - but things got a bit warm and the blue signal pipe blew off.

Need to fit a blow off valve as it's a bit scary relying on just the unloaders

 

[Gareth J]

Also got some documents for the AC35/AC41 from compair which have been very useful. Can upload them somewhere if anyone would like them.

 

[Gareth J]

Makes the little 35 wobble with the torque at higher pressures. And I need to find a shorter shaft.