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UAT or no UAT
07-14-2009 | 07:04 AM
#26
RE: UAT or no UAT
ORIGINAL: BaldEagel
Sandor
Did the search and it seems that most who where getting problems with the Orbit Clunk where using over a 120 size turbine, perhaps that was just a case of the Orbit clunk not being able to supply enough fuel for these, it seems strange that air is able to enter the feed pipe when the clunk is fully immersed in fuel, I would not have thought that the fuel itself had enough air in it to cause this and my thoughts are that the air is entering at the front of the tank through the joint at the cap, what do you think?
Mike
Sandor
Did the search and it seems that most who where getting problems with the Orbit Clunk where using over a 120 size turbine, perhaps that was just a case of the Orbit clunk not being able to supply enough fuel for these, it seems strange that air is able to enter the feed pipe when the clunk is fully immersed in fuel, I would not have thought that the fuel itself had enough air in it to cause this and my thoughts are that the air is entering at the front of the tank through the joint at the cap, what do you think?
Mike
let me try to explain.
the Skill clunck (2 stroke engine) uses about 1 liter of gasoline for every 30 minutes of running
skill recomends changing that clunck after 50 hours of operation
now lets say 50 hours is about 100 liters of fuel.
you can easely check that 100 liters for us jetjocks is about 1-2 months of flying or 400 minutes or 6.6666hours
.some people have problems with them , some dont.
they are good no doubt.
now imagine a UAT bag wich is made with the same material BUT about 100 times as big in surface material.
there you can see the slim chance of a cavitation of your pump.
in real life you will notice that people with small engines almost never have any problems , but customers with large engine can have serious problems
still i exchange a UAT BAG once a year or 2 years..
07-14-2009 | 07:25 AM
#27
Thread Starter
RE: UAT or no UAT
Sandor
I do understand, but not all UAT's have a bag inside them, I think its only the BVM one that does, the others, certainly mine have a multi pleated paper filter attached to the fuel feed pipe solidly in the middle of the tank, admittedly the multi pleated paper will have a greater surface area than the Orbit clunk, but I still do not see where the air comes from, cavitation can only cause air bubbles inside a fluid if the air is persent in the fluid already or can enter in some manner by suction, if we take this to its logical conclusion we are saying that if the pump is cavitating it is drawing in air from either the pump seals or the fuel feed connections, if not where is the air comming from?
Going back to my days of study in fluid dynamics a pump will only cavitate if it has demands upon it that are outside its operating capability i.e. demand is too much or supply is too little, its at that point that air will enter the system from one end or the other, but only if air is able to get into the supply or demand pipework, once a pump starts to cavitate it will no longer pump effectivly, therefore if the supply is an open end air can be drawn up the supply pipe into the pump and eventually it will stall if the demand remains high enough, so I suppose I have answered my own question. its either the clunk not able to supply enough fluid to stop the pump from cavitating or the pump is of insuficient specification to supply the fuel required, interesting stuff very thought provoking my old brain needs a jolt now and again. LOL
Mike
I do understand, but not all UAT's have a bag inside them, I think its only the BVM one that does, the others, certainly mine have a multi pleated paper filter attached to the fuel feed pipe solidly in the middle of the tank, admittedly the multi pleated paper will have a greater surface area than the Orbit clunk, but I still do not see where the air comes from, cavitation can only cause air bubbles inside a fluid if the air is persent in the fluid already or can enter in some manner by suction, if we take this to its logical conclusion we are saying that if the pump is cavitating it is drawing in air from either the pump seals or the fuel feed connections, if not where is the air comming from?
Going back to my days of study in fluid dynamics a pump will only cavitate if it has demands upon it that are outside its operating capability i.e. demand is too much or supply is too little, its at that point that air will enter the system from one end or the other, but only if air is able to get into the supply or demand pipework, once a pump starts to cavitate it will no longer pump effectivly, therefore if the supply is an open end air can be drawn up the supply pipe into the pump and eventually it will stall if the demand remains high enough, so I suppose I have answered my own question. its either the clunk not able to supply enough fluid to stop the pump from cavitating or the pump is of insuficient specification to supply the fuel required, interesting stuff very thought provoking my old brain needs a jolt now and again. LOL
Mike
07-14-2009 | 07:35 AM
#28
RE: UAT or no UAT
ORIGINAL: BaldEagel
Sandor
I do understand, but not all UAT's have a bag inside them, I think its only the BVM one that does, the others, certainly mine have a multi pleated paper filter attached to the fuel feed pipe solidly in the middle of the tank, admittedly the multi pleated paper will have a greater surface area than the Orbit clunk, but I still do not see where the air comes from, cavitation can only cause air bubbles inside a fluid if the air is persent in the fluid already or can enter in some manner by suction, if we take this to its logical conclusion we are saying that if the pump is cavitating it is drawing in air from either the pump seals or the fuel feed connections, if not where is the air comming from?
Going back to my days of study in fluid dynamics a pump will only cavitate if it has demands upon it that are outside its operating capability i.e. demand is too much or supply is too little, its at that point that air will enter the system from one end or the other, but only if air is able to get into the supply or demand pipework, once a pump starts to cavitate it will no longer pump effectivly, therefore if the supply is an open end air can be drawn up the supply pipe into the pump and eventually it will stall if the demand remains high enough, so I suppose I have answered my own question. its either the clunk not able to supply enough fluid to stop the pump from cavitating or the pump is of insuficient specification to supply the fuel required, interesting stuff very thought provoking my old brain needs a jolt now and again. LOL
Mike
Sandor
I do understand, but not all UAT's have a bag inside them, I think its only the BVM one that does, the others, certainly mine have a multi pleated paper filter attached to the fuel feed pipe solidly in the middle of the tank, admittedly the multi pleated paper will have a greater surface area than the Orbit clunk, but I still do not see where the air comes from, cavitation can only cause air bubbles inside a fluid if the air is persent in the fluid already or can enter in some manner by suction, if we take this to its logical conclusion we are saying that if the pump is cavitating it is drawing in air from either the pump seals or the fuel feed connections, if not where is the air comming from?
Going back to my days of study in fluid dynamics a pump will only cavitate if it has demands upon it that are outside its operating capability i.e. demand is too much or supply is too little, its at that point that air will enter the system from one end or the other, but only if air is able to get into the supply or demand pipework, once a pump starts to cavitate it will no longer pump effectivly, therefore if the supply is an open end air can be drawn up the supply pipe into the pump and eventually it will stall if the demand remains high enough, so I suppose I have answered my own question. its either the clunk not able to supply enough fluid to stop the pump from cavitating or the pump is of insuficient specification to supply the fuel required, interesting stuff very thought provoking my old brain needs a jolt now and again. LOL
Mike
i dont know anything about fluid dynamics, i can only tell you from experiance we have seen almost all of it..
and yes there is some kind of small airbubbles inside the fuel itself , have your pump run at full power and draw thru a to small tubing and watch the foam starting to come more and more.
on all our uat,s we do use the same bag as BVM does ,it is a normal automotive Fuel Strainer , however these are performance parts.
the filterering is incredible and stops even contaminated fuel or water drops to pas thru the membrane.
also run the fuel fast enough thru the fuel lines and see the static discharges sparking of the fuel and inside the tanks..
07-14-2009 | 07:45 AM
#29
Thread Starter
RE: UAT or no UAT
I guarantee you know more about fluid dynamics than you think, air is a fluid and I will take a wager that you know about laminar flow and boundary layers.
I use a "Mr Funnel" fuel filter funnel to transfer my Kero into my fueling station and am always amazed at how much water and crud it stops from going into the system.
I will do some experiements on a restricted fuel line and see what happens.
Mike
I use a "Mr Funnel" fuel filter funnel to transfer my Kero into my fueling station and am always amazed at how much water and crud it stops from going into the system.
I will do some experiements on a restricted fuel line and see what happens.
Mike
07-14-2009 | 07:51 AM
#30
RE: UAT or no UAT
ORIGINAL: BaldEagel
I guarantee you know more about fluid dynamics than you think, air is a fluid and I will take a wager that you know about laminar flow and boundary layers.
I use a ''Mr Funnel'' fuel filter funnel to transfer my Kero into my fueling station and am always amazed at how much water and crud it stops from going into the system.
I will do some experiements on a restricted fuel line and see what happens.
Mike
I guarantee you know more about fluid dynamics than you think, air is a fluid and I will take a wager that you know about laminar flow and boundary layers.
I use a ''Mr Funnel'' fuel filter funnel to transfer my Kero into my fueling station and am always amazed at how much water and crud it stops from going into the system.
I will do some experiements on a restricted fuel line and see what happens.
Mike
Run a pump on lets say 4 volts , let it run in a open loop and lengthen the fuel line as you go.
07-14-2009 | 08:32 AM
#32
Joined: Mar 2004
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From: UK
RE: UAT or no UAT
ORIGINAL: Jgwright
<snip> since discovering pleated paper filters I have only used them for my tanks, <big snip>
John
<snip> since discovering pleated paper filters I have only used them for my tanks, <big snip>
John
Where do you buy the pleated paper filters from? Mail order? Local shop (eg garden machinery store, boat chandler, Halfords ....etc)?
Cheers
Gordon
07-14-2009 | 01:23 PM
#35
Joined: Mar 2004
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From: UK
RE: UAT or no UAT
ORIGINAL: BaldEagel
Gordon
Mick Reeves has them on his web site.
Mike
Gordon
Mick Reeves has them on his web site.
Mike
ORIGINAL: Jgwright
Gordon
I have not been able to get them in the UK, they have to be sourced from the USA or Canada.
John
Gordon
I have not been able to get them in the UK, they have to be sourced from the USA or Canada.
John
Gordon
Edit: Well I should have looked harder. The AC GF-470 comes up almost at the top of the list by clicking the cross-reference tab! I feel a session with my Unimat-3 will be happening in the near future. Thanks John.
Meanwhile its back to RCJI. I've been going though the past 6-7 years issues to catch up on turbine operating tips. Amazing how the li'l Wren is concentrating my mind and I've only got as far as putting it on a test stand.
