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help with pump design

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vince wakefield12/11/2011 22:56:22
6 forum posts
Hi, I am wanting to make a small pump that is run from compressed air that will pump oil up about 300mm at a rate of about 200ml/min.
 
i want to use the minimum amout of air and be able to make all the components on my lathe or piller drill.
 
I have the idea of 1 piston with a chamber at each end one for compressed air and the other for pumping the oil. a few springs and valves might help.
 
Thats about as far as i can go, if it makes any sence can anyone direct me to any planes or am i trying to make somthig thats not possible.
 
Cheers
 
 
 

Stewart Hart12/11/2011 23:07:41
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674 forum posts
357 photos
Try "southworth" they do a rang of small pumps and may have something that will fit you're requirements.
 
Stew
Maurice16/11/2011 22:38:37
469 forum posts
50 photos
Maurice16/11/2011 22:39:06
469 forum posts
50 photos
Richard Parsons17/11/2011 11:52:42
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645 forum posts
33 photos

HI Vince


Why not use a gear pump driven by a small ‘Windy Billy’ (air turbine)


Rds


Dick.

vince wakefield17/11/2011 12:23:38
6 forum posts
an "air turbine" sounds like it will use a fair bit of air, i would also have to buy a gear pump and i am trying to keep costs down as much as possible,
 
my current thinking for the pump is to use a piston and a couple of check valves and for the motive force an air pump like this
http://www.floridaame.org/GalleryPages/g1EX0033.htm.

perhaps combining the 2 into one unit with both the engine and pump running from one crank. Although i am concerned that it might be a bit fast for this design of pump and may need gearing down but i suspect i will have to make it before i know if it will work or not.
 
Thanks for the idea.


Richard Parsons17/11/2011 15:29:44
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645 forum posts
33 photos

There are two simple types of rotary oil pump. The first is the ‘gear pump’, the second is the rotary eccentric pump. Both of these can be built quite easily if you have access to a lathe. There is a third type which is the swash plate pump. This has multi cylinders, which may be spring loaded and are pushed up/down by a plate which is fixes to the axle at an angle.


Finally there is the peristaltic pump. Here the rollers mounted on a disk squeeze the oil pipe moving little pockets of oil from the inlet to the output.


The drive could be either an air turbine or a steam engine running on air.


Finally you could buy a steam boiler feed pump kit, which could be run on air


I have just re read your requirements – I would try a motor car wind screen washer pump from a breakers yard.


When I was into submarines I often made gear pumps at vey little cost.

Les Jones 117/11/2011 17:00:44
2292 forum posts
159 photos
Hi Vince,
What about using a system without a crank. Have a piston in a cylinder with oil on one side and air on the other. Have the piston rod coming through a seal and use the motion to operate a spool valve with backlash in the linkage to the spool valve. The valve would only be moved from allowing air in to allowing the air out at the ends of the stroke of the piston. An alternative would be to use a mechanism like a toggle switch to operate some other type of valve. On the oil side you would just need two non return valves.
 
Les.
vince wakefield17/11/2011 17:32:04
6 forum posts
Thanks guys,
 
Les, that is exactly what i would like to make, i have already ordered some non-return valves as i was planning on using a simple piston with the valves to make the pump part, Do you have any links to "spool valve with backlash" as this stuff is all new to me.
 
cheers
 
Vince
Les Jones 117/11/2011 17:57:12
2292 forum posts
159 photos
Hi Vince,
I have no links to information on spool valves. My understanding is a spool valve is basically a rod that is a close sliding fit in a housing. for each port on the valve there are two holes in the housing on opposite sides of the rod. At this point the rod is reduced in diameter so that there is a path between these two holes for the fluid. If the rod is then slid in the housing the full diameter of the rod blocks the path of the fluid. For your purpose you would need a two port version. When one port was closed the other would be open. The backlash just means there would be play in the linkage. For example if the travel required by the valve was 5 mm and the stroke of the cylinder was 20 mm then you would need 15 mm play in the linkage, For example a 3 mm pin between the ends of an 18 mm slot.
 
Les.
vince wakefield17/11/2011 19:18:00
6 forum posts
How about this for a desgn.
 
 
Air on thre right and oil on the left via 2 one way valves (not shown)
 
first do you think it would work?
 
if yes then can anyone suggest how to work out the spring strenth for the pump side if i was to use 30psi and the bore was 15mm. i suspect the spring would need to be smaller then the bore & maybe a stroke of 12mm or so.
 
All the numbers above can be changed.

Edited By Katy Purvis on 01/06/2015 12:29:07

Les Jones 117/11/2011 19:56:02
2292 forum posts
159 photos
Hi Vince,
I do not see how your valve system will work. I assume the air comes in from the right and exhausts at the top. I assume to start the spring on the left of the piston (Which I forgot to mention would be required for my idea to work.) is stronger than the one holding the ball valve shut. When the air is switched on the piston would move to the left but would stop as soon as the ball valve closed. The piston would stay in that position. Even if the air was removed the piston would stay in that position. You need the air to be switched on to the right hand side of the piston only when the piston reaches the right hand end of the travel and remain on until the piston reaches the left hand end of the travel. At that point the exhaust pot needs to be opened an remain open until the piston reaches the right hand end of the travel. This is why the backlash is required between the piston and the changeover valve. The valve does not have to be a spool valve. It could even be as simple as the valve system on an oscillating steam engine. A positive toggle action on the valve would make the pump more reliable so it did not rely on the inertia of the piston to cause the full travel of the valve.
 
Les.
Stub Mandrel17/11/2011 20:56:21
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4318 forum posts
291 photos
1 articles
Vince's sytems will work in theory, because that's exactly how my Gasparin CO2 motor works. However the gasparin has a prop which acts as a flywheel - my guess is that a spring will only work at one resonant frequency and will not succeed with a varying load.
 
Neil
Hugh Gilhespie17/11/2011 22:59:22
130 forum posts
45 photos
Probably just me, but if that's a ball valve on the right, in the air intake, surely it will never open?
 
Hugh
vince wakefield18/11/2011 01:20:39
6 forum posts
the idea is that at rest the ball valve is opened by the pin on the piston,
 
air is injected into the cylinder and the piston is pushed down, the valve closesand the pressure is released via the side port,
 
the spring then pushes the piston back to the top and we start again.
 
in theory the spring is just taking the place a fly wheel.
 
it only needs to run a 1 speed, the less air pressure it needs the better, but i could go up to 80psi if i need to.
BERTO19/11/2011 00:13:24
46 forum posts
Hi Vince.
Have a look around on the internet for how a pneumatic double diaphragm pump works , it may give you some ideas .
You did not mention the viscosity of the oil or what pressure you need it to be supplied at ?
For a fun project you could try an air powered oscillating engine to turn a rotory vane pump or even a piston pump (crank or cam operated ).
 
Regards .
Ian .
Ian S C19/11/2011 09:55:05
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7468 forum posts
230 photos
Vince, how about using an oscillating engine as the pump, driven by another slightly bigger oscillating engine. It could be made similar to a V twin, with one cylinder driving, and the other pumping. Ian S C
vince wakefield19/11/2011 10:40:04
6 forum posts
Posted by Ian S C on 19/11/2011 09:55:05:
Vince, how about using an oscillating engine as the pump, driven by another slightly bigger oscillating engine. It could be made similar to a V twin, with one cylinder driving, and the other pumping. Ian S C
this was my original thought, but if it can be made without any rotating bits there will be less wear and simpler to make, its just getting the balance between the air pressure, the spring strength and the force needed to move the oil.
 
I may start with a strongish spring and high air pressure and see if i can get that working and then reduce until it won't pump any more, then up it a bit. just means having a load of springs of differant strengths but all the same dimentions and/or have a variable preloading on the spring
 
The oil to be pumped is used cooking oil, the one way valves i have ordered are for 6mm pipe but i can get larger if i need to reduce the resistance of the oil flow part of the system.
 
Thanks for all the idea's
Ian S C20/11/2011 01:20:59
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7468 forum posts
230 photos
Vince, you might have a bit of fun with the springs if its anything like a free piston hot air engine that I have been playing around with since 1998, I don't think I,v got it quite right yet. The pumping rate will vary according to the temperature ie., fast when warm, and dead slow/ stop when its cold. Ian S C

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