Help needed in debugging a fuel system fault.
12-01-2012, 09:05 AM
#26
RE: Help needed in debugging a fuel system fault.
Ragz, this was flight no 5, when we just started to get comfortable with the UB and started pushing her with full thrust verticals and passes, anyway the Oly pump in the UB compared to your SG hawk is working muck harder because of the multiple tank setup against just a single big tank feeding the accumulator in your SG hawk. Multiple tanks setup combined with soft tygon...... Who knows.
12-01-2012, 10:54 AM
#27
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RE: Help needed in debugging a fuel system fault.
Rags,
As part of my previously mentioned debugging, I installed a CAT instead of a UAT since the UAT was collapsing under vacuum. I LOVE the CATs (airtrap, not the fuzzy things that steal earplugs). Th have multiple sizes and it might be worth consideration.
Dave
As part of my previously mentioned debugging, I installed a CAT instead of a UAT since the UAT was collapsing under vacuum. I LOVE the CATs (airtrap, not the fuzzy things that steal earplugs). Th have multiple sizes and it might be worth consideration.
Dave
12-01-2012, 03:28 PM
#28
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RE: Help needed in debugging a fuel system fault.
Hi Ragz,
Everyone has been dancing around it. Pneumatic Resistance in the fuel lines between tanks. Hardware too small.
This can cause leaks on a proven system, which will give the air bubble issue. I have switched to the large festo fittings from Tom Cook at Jet ModelProducts. I use the 3/16 ID tygon fuel line from the vents, thru the tanks, and Tom's fuel accumulator, to the pump. Any thing on the suction side of the pump is 3/16. Pump to turbine is usually 4mm which is fine. My Olympus is slightly stroked and performs flawlessly with this set-up. JMP has everything you need. An easy check is when you fuel up. If there is any swelling of any tank in your system, there is resistance.
Jack Holland
Everyone has been dancing around it. Pneumatic Resistance in the fuel lines between tanks. Hardware too small.
This can cause leaks on a proven system, which will give the air bubble issue. I have switched to the large festo fittings from Tom Cook at Jet ModelProducts. I use the 3/16 ID tygon fuel line from the vents, thru the tanks, and Tom's fuel accumulator, to the pump. Any thing on the suction side of the pump is 3/16. Pump to turbine is usually 4mm which is fine. My Olympus is slightly stroked and performs flawlessly with this set-up. JMP has everything you need. An easy check is when you fuel up. If there is any swelling of any tank in your system, there is resistance. Jack Holland
12-01-2012, 06:02 PM
#29
RE: Help needed in debugging a fuel system fault.
Ragz,
Yes tygon can collapse.. I use 6mm clear so I can see whats happening.. You need to go thru the system again and make sure all the fittings and connections dont have a restriction... on my rookie, it did the same thing.. it ended up being the tank vent having some additional brass casting.. I drilled it out and problem went away.. I used to see the tanks and traps flex...
Troubleshooting>>
Take the main feed line from the air trap and push fuel backwards through it and flush the system into the header tank.. then pull the header and dump it and clean it.. check the fittings while there.. then put it all back together.. fill it normally, and pull the fuel through the trap with your fueling pump... you can use a smaller battery or lesser voltage but if it flows through the trap and tanks and the bungs with the fueling pump, it will work normally... i use my pump to check out my systems on every install before running it...
if you are pulling fuel thru your main line and watch the tanks to see if any of them are getting sucked down or sqeezed on the sides, watch for bubbles... on my elan, I got a piece of fiberglass out of the system.
when its all done.. put it all together and run the motor half to 2/3 and make a ground run and feed all the fuel out down to the header to make sure...shake it, watch for bubbles.. I dont like the soft tubing myself..
Yes tygon can collapse.. I use 6mm clear so I can see whats happening.. You need to go thru the system again and make sure all the fittings and connections dont have a restriction... on my rookie, it did the same thing.. it ended up being the tank vent having some additional brass casting.. I drilled it out and problem went away.. I used to see the tanks and traps flex...
Troubleshooting>>
Take the main feed line from the air trap and push fuel backwards through it and flush the system into the header tank.. then pull the header and dump it and clean it.. check the fittings while there.. then put it all back together.. fill it normally, and pull the fuel through the trap with your fueling pump... you can use a smaller battery or lesser voltage but if it flows through the trap and tanks and the bungs with the fueling pump, it will work normally... i use my pump to check out my systems on every install before running it...
if you are pulling fuel thru your main line and watch the tanks to see if any of them are getting sucked down or sqeezed on the sides, watch for bubbles... on my elan, I got a piece of fiberglass out of the system.
when its all done.. put it all together and run the motor half to 2/3 and make a ground run and feed all the fuel out down to the header to make sure...shake it, watch for bubbles.. I dont like the soft tubing myself..
12-02-2012, 10:22 AM
#30
RE: Help needed in debugging a fuel system fault.
ORIGINAL: c_makhija
Hi Oli, I was flying anurags UB when she flamed out. All the 3 tanks are sealed and no leaks found. I know it's proven, but I still doubt the 8mm tygon which is used all over, it seems soft since its new and I feel could collapse when the oly is at full thrust, thus drawing fuel from the accumulator momentarily. I personally still prefer the stiff PU tubing. I could be wrong of course.
Chatty.
Hi Oli, I was flying anurags UB when she flamed out. All the 3 tanks are sealed and no leaks found. I know it's proven, but I still doubt the 8mm tygon which is used all over, it seems soft since its new and I feel could collapse when the oly is at full thrust, thus drawing fuel from the accumulator momentarily. I personally still prefer the stiff PU tubing. I could be wrong of course.
Chatty.
I use the large tygons in conjunction with the BF-300 in several different setups and never had a problem.
Bare in mind the the 300 requires a much higher fuel flow than the AMT.
Once again, you do not need the engine running to test the system. Just run the pump at max thrust voltage and loop the fuel line back into the jerrycan...
