No success with Henson/BVM UAT. What to use?
03-02-2015, 02:08 PM
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No success with Henson/BVM UAT. What to use?
I can't stop the flameouts in my T-Rex 700 with wren 44 turbine. I'm using the UAT on 45 degree. Haven't tried all up yet. I remove every bubble on it by shaking the model after starting the turbine up.
But somehow I still have flameouts eventually. I'm really not happy with the hensen/bvm UAT, what would you suggest I could use insteady? I was thinking about the ball FCT uat model OR a Hopper tank.
What woul you do?
THanks for any input! best regards, Calil
But somehow I still have flameouts eventually. I'm really not happy with the hensen/bvm UAT, what would you suggest I could use insteady? I was thinking about the ball FCT uat model OR a Hopper tank.
What woul you do?
THanks for any input! best regards, Calil
Last edited by Calil; 03-02-2015 at 02:21 PM.
03-02-2015, 02:28 PM
#2
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A little more information would be helpful.
Are you sure your flameouts are cause by air bubbles?
Is the current UAT that you are using getting air in it when the engine is running?
If so, have you figured out how the air is getting into the UAT?
What type of system are you using to fill the tanks, and how are you sealing it once the tanks are full?
If the UAT is not getting air in it you could have a leak between the UAT and the pump inlet. The fuel nipple on the BVM UAT is rather small, and if you use the wrong size tubing on it air can get sucked in by the pump at that connection.
Pictures of your setup could help diagnose your problem.
Are you sure your flameouts are cause by air bubbles?
Is the current UAT that you are using getting air in it when the engine is running?
If so, have you figured out how the air is getting into the UAT?
What type of system are you using to fill the tanks, and how are you sealing it once the tanks are full?
If the UAT is not getting air in it you could have a leak between the UAT and the pump inlet. The fuel nipple on the BVM UAT is rather small, and if you use the wrong size tubing on it air can get sucked in by the pump at that connection.
Pictures of your setup could help diagnose your problem.
03-02-2015, 03:14 PM
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Hello Kevin
Yes this is my setup. Saturday I was told that the FESTO shouldn't be use on vacuum systems then AFTER the flameout I replaced the festo valve for the jetcat fuel valve. I'm thinking in give the Hensen/BVM UAT a second chance and use another one I have here on the vertical position, behing the main tank (like the majority T-Rexes 700 with turbine use).
I know it's air bubbles because I saw a lot of bubble and a big bubble on the UAT. I flew a lot without the last flameout saturday. But I understand that even if bubbles come to the UAT it shouldn't allow bubbles to the fuel pump. It happened after a quick rudder turn arround.
Yes this is my setup. Saturday I was told that the FESTO shouldn't be use on vacuum systems then AFTER the flameout I replaced the festo valve for the jetcat fuel valve. I'm thinking in give the Hensen/BVM UAT a second chance and use another one I have here on the vertical position, behing the main tank (like the majority T-Rexes 700 with turbine use).
I know it's air bubbles because I saw a lot of bubble and a big bubble on the UAT. I flew a lot without the last flameout saturday. But I understand that even if bubbles come to the UAT it shouldn't allow bubbles to the fuel pump. It happened after a quick rudder turn arround.
Last edited by Calil; 03-02-2015 at 03:17 PM.
03-02-2015, 03:37 PM
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Yes and also the valve was closed.
I was thinking about one and about the ball from FCT, thanks for the reply. How many flights with succes without flameouts did you get already?
I was thinking about one and about the ball from FCT, thanks for the reply. How many flights with succes without flameouts did you get already?
Last edited by Calil; 03-02-2015 at 03:48 PM.
03-02-2015, 03:41 PM
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03-02-2015, 04:09 PM
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It may not be your problem, but the Ty raps holding the valve (and tubes) do not look good to me. If they are tight enough they may cause the tubes to change their round shape and not seal correctly in the Festo fitting.
03-02-2015, 04:12 PM
#10
The feed line to the pump looks like it's 4mm tubing. That style uat cap is typically set up for 6mm like you have on your fill line. How did you get the 4mm line to fit the cap nipple?? Is the uat filling up with air or just sucking air into the pump feed line?? I don't like the festos on the fill line either.
Vin...
Vin...
03-02-2015, 05:20 PM
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The feed line to the pump looks like it's 4mm tubing. That style uat cap is typically set up for 6mm like you have on your fill line. How did you get the 4mm line to fit the cap nipple?? Is the uat filling up with air or just sucking air into the pump feed line?? I don't like the festos on the fill line either.
Vin...
Vin...
03-02-2015, 06:47 PM
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It's not Tygon, it's polyurethane. It's just yeallow after some use
03-02-2015, 11:32 PM
#16
+1 with Bob.
You need to remove the old teflon tape and put new one.
ALSO! the Hanson UAT is not the same as the BVM UAT. It has in-line porous element that is placed inside the bag and filters the fuel.
Check that here:
http://www.ultimate-jets.net/blogs/f...considerations
This is adding a lot of suction drag upstream the pump. However, the flow should not be that high with your Wren.
You need to remove the old teflon tape and put new one.
ALSO! the Hanson UAT is not the same as the BVM UAT. It has in-line porous element that is placed inside the bag and filters the fuel.
Check that here:
http://www.ultimate-jets.net/blogs/f...considerations
This is adding a lot of suction drag upstream the pump. However, the flow should not be that high with your Wren.
03-03-2015, 05:36 AM
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Mine is the BVM UAT. I already put more teflon before I used it, it was brand new but I reinforced the teflon. I removed the festos and the cap end for this:
Since I can't find a ball-cock valve for 6 mm I put this 4mm Jetcat valve on it. If you guys know where can I find a 6 mm valve please give me the link here.
The UAT is empty because it's another one that I'll try in the weekend and when I toke the pictures it was empty. It's full now. I always let it with kero inside to avoid bubbles on the pickup bag
Since I can't find a ball-cock valve for 6 mm I put this 4mm Jetcat valve on it. If you guys know where can I find a 6 mm valve please give me the link here.
The UAT is empty because it's another one that I'll try in the weekend and when I toke the pictures it was empty. It's full now. I always let it with kero inside to avoid bubbles on the pickup bag
03-03-2015, 05:53 AM
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03-03-2015, 06:35 AM
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The UAT at the end of flight show some air bubble (arround 1 centimeter diameter) even with no manouvers, just hover. And when I start up the turbine I shake the helicopter and some bubbles goes to the fuel feed line.
I will try my another UAT. Both are BVM not hanson. I'll let you know now without the festos.
I will try my another UAT. Both are BVM not hanson. I'll let you know now without the festos.
03-03-2015, 07:50 AM
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I do that, It was full with kero for months (I fly every weekend), never let it dry. But everytime I fill with kero I had to to that, every single flight, and always there was bubbles going to the pump. Then it stops, I fly without issue (until saturday) and then again and again. It does not seens right to me have to shake the helicopter before every single flight. I'm redoing all the fuel line.
Last edited by Calil; 03-03-2015 at 07:53 AM.
03-03-2015, 07:55 AM
#23
Ditto what Vincent said. That being said, festos should not be a problem, but using tygon with festos is. Stick to the clear standard size tubing for that (4mm, 6mm).
I wasted two good airframes, and 4+ UAT's trying to figure out an air leak problem. Turns out it was a pump nipple that was loose. Some manufacturers opt for the high quality barbed fittings that are a royal pain to disconnect, and sometimes it leads to the fitting separating from the pump wihtout you being aware. The fix is easy, you just CA it back into place. I had to setup a bench run to see where the bubbles where coming out of, until it was clear where the problem was.
Check your pump. An air leak at the pump will lead to a loss of power and eventually airframe. Some bubbles here and there from the UAT or tanks should not be a problem, the engine can take them. My UAT always has air in it, and it doesnt create any issues.
Do a bench test if you have to. Just dont risk your airframe. You are guaranteed to lose it if you dont get this right.
David
In addition, use the largest diameter tubing you can all the way up to the pump, AND ON THE VENTS!!!. This reduces load on the suction side, and negative pressure on the UAT.
I wasted two good airframes, and 4+ UAT's trying to figure out an air leak problem. Turns out it was a pump nipple that was loose. Some manufacturers opt for the high quality barbed fittings that are a royal pain to disconnect, and sometimes it leads to the fitting separating from the pump wihtout you being aware. The fix is easy, you just CA it back into place. I had to setup a bench run to see where the bubbles where coming out of, until it was clear where the problem was.
Check your pump. An air leak at the pump will lead to a loss of power and eventually airframe. Some bubbles here and there from the UAT or tanks should not be a problem, the engine can take them. My UAT always has air in it, and it doesnt create any issues.
Do a bench test if you have to. Just dont risk your airframe. You are guaranteed to lose it if you dont get this right.
David
In addition, use the largest diameter tubing you can all the way up to the pump, AND ON THE VENTS!!!. This reduces load on the suction side, and negative pressure on the UAT.
Last edited by FalconWings; 03-03-2015 at 07:58 AM.
03-03-2015, 07:59 AM
#24
I do that, It was full with kero for months (I fly every weekend), never let it dry. But everytime I fill with kero I had to to that, every single flight, and always there was bubbles going to the pump. Then it stops, I fly without issue (until saturday) and then again and again. It does not seens right to me have to shake the helicopter before every single flight. I'm redoing all the fuel line.
03-03-2015, 09:42 AM
#25
Larry/Instructor