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  #11  
Old 08-12-2018, 05:20 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 728
Default Is FR-4 that much mot thermally resistive than standard gasketing material?

Is the FR-4 really that much more thermally resistive than standard gasketing in similar thicknesses? If so, use on things like engine driven fuel Pumps might be a good application.
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Last edited by rjcthree : 08-12-2018 at 05:39 PM.
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  #12  
Old 08-13-2018, 09:39 AM
EXflyer EXflyer is offline
 
Join Date: Jan 2016
Location: Chiloquin OR
Posts: 81
Default Jet Drilling

When I was in A&E school they advised not to us a drill bit on jets as the hole, just like when building your AC, is not round and can affect the fuel distribution into the venture.
In my thinking with the trouble you are having why not go back to something else for you throttle body? Having an engine quit when there is no possible place to land is not something to do. Just my FYI.
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  #13  
Old 08-18-2018, 08:19 PM
bifft bifft is offline
 
Join Date: Feb 2012
Location: Utah
Posts: 74
Default

So, tried with just the insulating plate today, as expected that isn't enough.

Have got started on the vapor return line, but since I'm not very experienced with a lathe it is taking me a while. Doing it out of steel instead of AL at least for the firewall penetration. Debating buying some stainless to do it with but have heard it is difficult to machine. On call next weekend so will have the whole time at home to work on it.

Regarding why the TBI, that's because I want the inverted capability. Gives me inverted for $10k or so less than fuel injection. Do have the carb that came with the engine if it comes to that. Would add about 10 lbs.
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  #14  
Old 08-18-2018, 08:47 PM
Mark33 Mark33 is offline
 
Join Date: May 2010
Location: Baton Rouge, La.
Posts: 312
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Hey Brian,

If you’d like I can put you in contact with my buddy that has the Ellison and the return setup on his -7 and he can step you through exactly how he plumbed it. I know he uses an on/off valve that he mounted down on the spar next to his main fuel control valve to control his bypass fuel line, but I actually think it would be a little bit cleaner installation to use a little inline solenoid with a toggle switch mounted on the dash to control it. If you’d like to PM your contact information to me I can forward it to him.

Mark
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  #15  
Old 08-18-2018, 09:09 PM
VA Maule VA Maule is offline
 
Join Date: Apr 2016
Location: Bucking ham, Virginia
Posts: 130
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Stainless is indeed tuff to machine,but it welds nicely. What are you trying to machine? Many small steel hydraulic fittings are exactly the same as standard AN fittings & a much better selection than what Aircraft Spruce carries. TBI body's fitting threads may very well be O-ring boss British pipe threads wtch are standard hydraulic fittings also. Hydraulic shop should be able to fabricate a steel or stainless steel line with ends to mate up with fittings also.
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  #16  
Old 08-19-2018, 09:12 PM
bifft bifft is offline
 
Join Date: Feb 2012
Location: Utah
Posts: 74
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Now you guys are making me rethink my plan.

So, this is what comes out of the pressure regulator for a vapor return line:



It is sealed with an o-ring, the threads are 1/4x28tpi. Doesn't match any fitting standard I can find. The hole on the inside is sized for a post on the diaphram. The exterior is a hose barb for 1.8" hose. So, I need to get something out of this and back to the gas tank. I can't find 1/8" hose barb adaptors anywhere. 1/4" and up are everywhere.

My thought was to use nylon reinforced fuel line from the auto parts store, held on with a hose clamp. Put firesleeve over that.

To get thru the firewall, make a steel bulkhead fitting like:



Not as fireproof as stainless, but would 1/8" mild steel hold up to a fire longer than 0.025 (or whatever the firewall is) stainless? Standard AN fittings don't come in stainless, so pretty much using regular steel everywhere else.

Run the same kind of hose back to the tank, don't need firesleeve behind the firewall. Adel clamp it to the existing fuel line for support. For the fuel tank end, make the same fitting without the interior barb.

This is how far I got today before my tools needed sharpening again:




Thinking about it again today, I could get some 416 stainless, try to make something that replaces the part coming out of the pressure regulator. Make it have the 1/4" inside with an o-ring, then have a 37 degree flare on the outside for -3 hose. Could then use standard AN fittings and 3003 tube back to the tank. Would need to get the 3003 in place inside the cockput, would be a chore.
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  #17  
Old 08-20-2018, 08:53 PM
VA Maule VA Maule is offline
 
Join Date: Apr 2016
Location: Bucking ham, Virginia
Posts: 130
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Save your self a lot of effort. From Aircraft Spruce order # SS AN815-4J cut one nipple off flush to nut , on the 1/4" 28 x 1/8" hose barb cut off 1/8" hose barb ,tig weld together the 1/4"28 thread to modified AN815 nut to nut . From there it's simply AN-4 back to the tanks. Get some of that nice braded SS tefion line for FWF with AN-4 female ends and bulkhead fitting #SS AN832-4J for the firewall
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  #18  
Old 08-20-2018, 09:05 PM
bifft bifft is offline
 
Join Date: Feb 2012
Location: Utah
Posts: 74
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Quote:
Originally Posted by VA Maule View Post
Save your self a lot of effort. From Aircraft Spruce order # SS AN815-4J cut one nipple off flush to nut , on the 1/4" 28 x 1/8" hose barb cut off 1/8" hose barb ,tig weld together the 1/4"28 thread to modified AN815 nut to nut . From there it's simply AN-4 back to the tanks. Get some of that nice braded SS tefion line for FWF with AN-4 female ends and bulkhead fitting #SS AN832-4J for the firewall

That would be a lot easier, if I had a tig welder. Or indeed any way to weld stainless that I would trust. Just have an old flux-core welder and I don't trust my welding skills for anything flight related.
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  #19  
Old 08-26-2018, 08:35 PM
bifft bifft is offline
 
Join Date: Feb 2012
Location: Utah
Posts: 74
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So, being on call and unable to go to the airport, still got some shop time in:



The compression fitting end held air pressure before I drilled the hole all the way through, the O-ring should be here Tuesday. Will be able to see if it holds fuel after everything is hooked up.

This 416 stainless is really easy to cut. Much easier than the mystery metal mild steel I had been using before. Going to buy the proper alloys from now on.
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  #20  
Old 09-03-2018, 09:36 PM
bifft bifft is offline
 
Join Date: Feb 2012
Location: Utah
Posts: 74
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And installed:



Got it in Saturday, but waited till today for the sealant to harden up before testing. As per Rotec's instructions, didn't install any other restrictions between the fitting and the tank (drilled mine out to the same 1/16" size as theirs).

With the boost pump on, get about 21gph going back to the tank. Too much? Well, I tried it on the ground, got up to an oil temperature of 195 without any problems running full power. Oil didn't get hotter (air only about 80 degrees, the summer heat has past) even with extended ground runs.

So, time to see if it flies. Yep, flies no problem, even after extended ground runs left the engine very hot.

With it pumping that much back to the tank, I will need to be sure to use that tank first and only run the other for short periods after the main has emptied a bit. Did that in flight today, did about 90% on the right (return line tank) and 10% on the left, landed with about the same in both.

May want to add some more restriction to that line.
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