Would you be interested in flow divider to injector hoses instead of rigid tubing?
Tom
Tom
Van's Air Force
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Hoses for flow dividers
- Thread starter TS Flightlines
- Start date
My question(s):
Would it be lighter, less expensive, easier to install, or longer lasting?
The cheapest thing about flying is the pilot. Being a cheap pilot, I am also lazy so would only pay more for an easier way, longer lasting, and lighter product.
Yes I was an engineer before I retired.
Gary, thats actually one of details to work out. Obviously the ball seat hose ends would need to be developed. We were thinking about it for about a year, after some of our fellow RVers had some rigid injection line failures.
The biggest obstacle is the hose ends, so obviously some cost analysis would need to be done. I have 2 versions prototyped, just havent gotten back to them.
Tom
The biggest obstacle is the hose ends, so obviously some cost analysis would need to be done. I have 2 versions prototyped, just havent gotten back to them.
Tom
[email protected]
Well Known Member
Already done
I voted no because I installed SDS EM5-F and it has the flexible lines.
BUT, I guarantee you that if I had fuel injection and the ridged lined they would be replaced with the flexible Teflon lined stainless steel lines.
These type of things make me sleep well knowing it won't be a problem on the next flight.
My three cents worth Art
I voted no because I installed SDS EM5-F and it has the flexible lines.
BUT, I guarantee you that if I had fuel injection and the ridged lined they would be replaced with the flexible Teflon lined stainless steel lines.
These type of things make me sleep well knowing it won't be a problem on the next flight.
My three cents worth Art
Plummit
Well Known Member
I'll answer with a resounding "YES". I'm not cheap and would go for it in a heartbeat.
-Marc
Stewbronco
Well Known Member
Firesleeved and insulated??
Heh Tom....definitely YES ...I am assuming firesleeved and insulated ...might help a bit with hot starts ....only concern( not a big one though) Is how much support would be needed to hold them in place ?...that is only advantage I can see to SS lines .
Heh Tom....definitely YES ...I am assuming firesleeved and insulated ...might help a bit with hot starts ....only concern( not a big one though) Is how much support would be needed to hold them in place ?...that is only advantage I can see to SS lines .
Can you get hoses that have as small of an internal cross section as the 1/8" SS lines? If you double the ID of the tube / hose, that doubles the amount of fuel that can boil off after shut down, and could/would make hot starts more difficult.
Larry
MED
Well Known Member
Larry, thats an interesting point. Some of the .125 OD injector lines are .020 wall, some we've seen is .035, which is more common. So on the .035 wall version that makes the ID .055. A -2 teflon hose is .079 ID. A AN800 primer ball end is .076 ID at the head.
In our SDS injector hoses, we (and Ross) use -3 hose with .125 ID, but the stem ID is .079. WE have seen any issues with that.
Now----2 teflon hose is HARD to get, and the hose ends, especially a primer style hose end would be expensive to manufacture, and frankly counter productive. If the -2, .079 hose ID were used, the stem OD would need to be minimum of .085 to get an expansion grip on the liner. And with a crimp fitting, you have to have some wall thickness to be able to crimp the collar, the braid, and the liner onto. That means minumum of +-.020-.030 to give enough retention under max rated pressure. You dont want a thin walled stem or the wall would compress, restricting, or even breaking during the crimp process.
So what leaves us with .025-.045 stem ID, and that in itself is flow restrictive. Would help the hot start, but probably not provide enough fuel to run the engine at max power. WE know that using a -3 hose ( .125 ID, .079 stem ID) a IO540 will run at max power output just fine.
As for firesleeving, yes it can be done. As for integral firesleeving, thats debateable, and again not cost efficient.
The purpose of the exercise was in response to some owners that had rigid line failures at the braze joints. (Whether the line was supported properly isnt part of this exercise.) Whether its practical is another discussion. Yes, several engineering points, developement, engine performance and yes, hot start operations are all part of it. I was just asking whether there was interested builders.
Tom
In our SDS injector hoses, we (and Ross) use -3 hose with .125 ID, but the stem ID is .079. WE have seen any issues with that.
Now----2 teflon hose is HARD to get, and the hose ends, especially a primer style hose end would be expensive to manufacture, and frankly counter productive. If the -2, .079 hose ID were used, the stem OD would need to be minimum of .085 to get an expansion grip on the liner. And with a crimp fitting, you have to have some wall thickness to be able to crimp the collar, the braid, and the liner onto. That means minumum of +-.020-.030 to give enough retention under max rated pressure. You dont want a thin walled stem or the wall would compress, restricting, or even breaking during the crimp process.
So what leaves us with .025-.045 stem ID, and that in itself is flow restrictive. Would help the hot start, but probably not provide enough fuel to run the engine at max power. WE know that using a -3 hose ( .125 ID, .079 stem ID) a IO540 will run at max power output just fine.
As for firesleeving, yes it can be done. As for integral firesleeving, thats debateable, and again not cost efficient.
The purpose of the exercise was in response to some owners that had rigid line failures at the braze joints. (Whether the line was supported properly isnt part of this exercise.) Whether its practical is another discussion. Yes, several engineering points, developement, engine performance and yes, hot start operations are all part of it. I was just asking whether there was interested builders.
Tom
This doesn't really translate, as ross' injectors seal closed at shut down and don't bleed any fuel in the intake, regardless of heat. The bendix system injectors are always open and allow boiling fuel to bleed into the intake chamber. Not saying it is a deal breaker, but I suspect that it is advantageous to minimize the amount of fuel being dumped into the intake chamber after shut down / heat soak. You also need to account for re-filling those lines before start up, else things will be rough untill all the air is bled out and larger hose volume means a longer time for this to happen. This also doesn't apply with Ross' setup.
I get the desire to eliminate a failure point, but wonder if it introduces new issues.
Larry
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LOL---you are much better at math than I am. And YES---there are alot of things to consider. I wasnt trying to compare an electronic injector to an open orifice style mechanical one. BUT---in the SDS system at 40+ psi the return is on the fuel block, not the injectors. So single line to each injector. I would think that there 'might' be some residual fuel left in the injector hoses--well at least some that didnt vaporize similar to a rigid tube.
So is the residual fuel 'cooler' because its in a teflon liner and not a stainless tube? Gee-I dont know, but my feeling is yes, but to what point, I dont know. Sounds like some thermocouples in a hose port to test the fuel temp would be a fun exercise, but under what conditions?
Gee---sounds like we need a test plane. If only mine were finished---not anytime soon!
Tom
So is the residual fuel 'cooler' because its in a teflon liner and not a stainless tube? Gee-I dont know, but my feeling is yes, but to what point, I dont know. Sounds like some thermocouples in a hose port to test the fuel temp would be a fun exercise, but under what conditions?
Gee---sounds like we need a test plane. If only mine were finished---not anytime soon!
Tom
The SDS fuel return is also a sealed system; It is sealed by the pressure regulator on the return lines. It is designed to open and bleed ONLY above it's set pressure, which I presume is around 40-45 PSI. We can ask Ross, but I would expect the entire fuel rail and it's branches to hold 40 PSI for an extended time and not have any air in it even after a heat soak, as there is no means for it to bleed or leak below 40 PSI. Excess pressure from expanding fuel is bled off by the regulator, but very different from an open bendix system which can boil off most of it's fuel post spider due to heat.
Larry
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MED
Well Known Member
Thank for pointing out my limited math skills.Good to see someone keeping me in check.
Easy mistake . . . not that I have ever made it . . .
I have seen two (2) fail in the past 25-years. (Two different airplanes.)
