BillJ

My Feedback: (19)

OK ..First THANK YOU to all that helped with my spaggetti wiring issue...Ready to move to the next level....Yellow A/C F 18 twin...Alignment of the Bifucated pipe to frame and engine....I have basicly built a couple of doughnuts at the rear which should center the thrust tube in the AC openings.... HOW do I know that I'm fairly STRAIGHT in the forward end (single opening) of my pipe alignment to the end of the engine ? I believe that I am to leave about a one inch gap between pipe end and engine end. Same on the intake end aprox 1 inch...pipe
My theory is that pipe should be level to thrust line of the aircraft, to eliminate adverse pitch trim. So engine needs to align to the level exhaust so that thrust is straight thru the pipe and not cocked or tilted. I am working with prior engine mount but no brackets or formers to attach my bifucated tube.(except as noted on the exiting end) HOW CRITICAL IS THIS ? I understand that you can burn up a pipe(TAMS and P-180) if exhaust is not centered

Could it be as simple as looking down the exhaust and eyeballing the exhaust to the engine ??

Sorry I don't have my camera here to give a clearer image.

This plane was turbine by first owner/ converted to twin electric by second . Now going back to turbine by third (me)

Appreciate the education


Bill

Countryboy

My Feedback: (25)

There are several ways to center the turbine in the pipe, ranging from simple to exotic. I went with a faily simple method that works quite well. I think the pics will speak a thousand words.

RCISFUN

My Feedback: (44)

Doesn't get any better than that!

BillJ

My Feedback: (19)

Thank you countryboy.....Exactly my kind of help....Firing up the band saw

Dr Honda

My Feedback: (4)

Geezz... Now I feel bad. I just eyeball it. (lol)

rcjetsaok

My Feedback: (7)

Bill,

You are getting great advice on the front alignment, the only thing I would like to add is concerning you " Donuts : at the exaust end.. By putting solid donuts around the pipes that center them in the fiberglass exhaust nozzles, Is that you are creating an air dam. The ram air in the fuselage needs all the places it can get to exaust. The inlets on this airplane are huge and the engine needs very little in comparison. What you will run ito is that the ram air in the fuse will seek other outlets to escape.. IE: gear door openings. My exaust nozzles are not restricted and I still have main doors that will not close all the way... I have considered going to a bigger air cylinders on the doors, .. It also helps to keep the rear as open as you can around the exaust nozzels for cooling reasons. I used bolts for anchors/stand-offs for my pipe nozzle's. Here's how I did mine..


Good luck on the project !!! ,


Danno

BillJ

My Feedback: (19)

Danno,
Very good point...I can use the doughnuts for alignment then attach similar to your method....How are the bolts you're using attach to the tube ? Do you have any pics of the front end of the tube and how it is being held in your airplane..... This plane has been thru a couple of conversions and many of the original formers and braces have been modified or are missing]


Bill

rcjetsaok

My Feedback: (7)

Bill,

My pipe is a Tam Pipe. Tam has straps that go around the outside of the pipe nozzles that are movable/adjusatable. They have a 4/40 blind nut on them. I uses a piece of 4/40 all thread and made my stand off. It has a nut on the inside of the fiberglass nozzle to adjust my distance and the the outside lock nut to tighten it all in place. on the front I have a piece of hardwood that is glues/bolted through the belly ( 1/2X3/4 ) at the 6 o'clock position standing vertically with a 8/82 threaded insert buried in the top ( Dubro ) and a 8/32 bold through the thick part bell mouth to hold the pipe in place. The height measurement is critical for centering of the pipe. then at 10 and 2 o'clock I drilled a hole in the bellmouth and used safety wire to anchor the pipe to the rear wing spar former thats between the pipe and engine. That whole set up is rock solid. that cannot move any direction at all. I'll try to get some pic's of the front, but it's hard to see with the engine in there... send me a PM or e-mail with you phone # and I'll be glad to visit. I have built 5 of these airplanes, and there are a few other things I would likr to talk with you about. Great project, your gonna love it !!!.

Danno


P.S. It's the the big Gray thing in the front !!!

rhklenke

My Feedback: (24)

Bill,

In addition to centering the engine in the opening of the pipe, you also need to make sure that the engine is aligned with the pipe. An engine that is centered in the pipe, but misaligned with the direction of the pipe can cause uneven heating and hot spots as well. Its not super critical, but a difference of more than a couple of degrees should probably be corrected.

At the aft end of the pipe, most jets have a former that has notches cut in it to let the ram air out of the aircraft. That is, in my mind, simpler, and more common that the standoffs that Danno made, but his method seems to work well and his picture looks great - even the jet...

It sounds like Danno has a lot of experience with that aircraft. I know that there are (or have been) issues with that airplane with turbine power with respect to the formers, wing mounting, etc. being strong enough. It would probably be worth having someone like him look at the "innards" of your plane to be sure that its going to be strong enough...

Bob

Countryboy

My Feedback: (25)

Although Danno's method is more free flowing (less drag), what Bob mentioned looks like this and is probably the norm. Also, in regards to what Bob said in his first statement.. if careful use is imposed with the jig I showed, you will achieve not only centering, but also alignment of the turbine to the pipe. You just need to make sure the disk that fits in the pipe is square in the pipe.