Builds The Mule: My OM617 swap and other improvements

[davegonz]

The only downside I see running it in the frame rail is that you can't see leaks or damage to the hose (if it even happens). Run some rubber edge trim around the openings and you should be good.

Don't forget to not over tighten those AN fittings !

 

[UZJ40]

I don't think there's anything wrong with inside, but if you're not using steel braided hose, I'd use some sort of chafing tape. Only a matter of time till the frame wears a hole in one of your fuel lines.

 

[DTSkyCop]

Incredible build here... Nice work...

 

[DPV7070]

The only downside I see running it in the frame rail is that you can't see leaks or damage to the hose (if it even happens). Run some rubber edge trim around the openings and you should be good.

Don't forget to not over tighten those AN fittings !

Oh don't worry, I've learned my lesson about over tightening things. My current victories include: 1 knuckle stud, 1 backing plate to knuckle bolt, multiple M6 and M8 bolts, etc. It's genetic I guess. My grandpa used to say something like, "tighten it down until it feels like it's going to let go, then back it off a half turn." He cracked more switch plate covers than any other electrician of his day.

I don't think there's anything wrong with inside, but if you're not using steel braided hose, I'd use some sort of chafing tape. Only a matter of time till the frame wears a hole in one of your fuel lines.

I was actually thinking about something along those lines. I'll have to wait until Tues to talk to some of our Airframes folks to see hat they recommend.

If I can get the fitting through the frame rail and over the factory crossmember that transects the frame, then I'll problably have to go outside. Either way, it's not gasoline so (knock on wood) hopefully no worry about explosions. If it did get a hole, I imagine I'd probably know since it'd be sucking a bit of air making it run like pooh...

 

[Cruising Canuck]

I've experienced air in diesel lines a couple times. It doesn't run like poo, it just dies.

 

[jstncse]

Do it. That hose will survive inside the frame just fine and you do not have to worry about getting it hung up on something.

 

[Weber Sarge]

Just a note about using those push-on AN fittings -
I had an issue with a fuel pump sucking air when I used those in the tank lines on my Sami - turns out they will not leak under pressure but would allow air to come in with a vacuum on the line somehow . Ended up using a different fitting , I suppose a clamp would probably fix the issue but just wanted to add an observation...
Sarge

 

[DPV7070]

Just a note about using those push-on AN fittings -
I had an issue with a fuel pump sucking air when I used those in the tank lines on my Sami - turns out they will not leak under pressure but would allow air to come in with a vacuum on the line somehow . Ended up using a different fitting , I suppose a clamp would probably fix the issue but just wanted to add an observation...
Sarge

Thanks for the heads up! I'm going to really hawk the clear fuel filter after the installation so I can observe any air that might be entering the system. I'm also using Loctite 565 on the threads of all fittings. Its an anaerobic sealer that should prevent any air through that avenue.
---------------------------------------------------------------------------------------------------------------
Also, another question: is it a bad design to have the feed line come from the tank (which is below the IP, then rise above the IP, then run downhill to the IP? In other words, the highest point in the fuel system is not the IP. Is this asking for trapped air in the system? Obviously I can bleed at the nozzles, but I was thinking priming issues?

If this kicks my ass, I'm sending the project to hibernate in TN for a few years...

 

[Weber Sarge]

It shouldn't be an issue , is there any sort of pusher/primer pump ?
Sarge

 

[davegonz]

Yeah, he's got a lift pump on the engine near the IP leading to the filter. I also think he'll be OK.

 

[DPV7070]

I was probably overthinking the line routing...

I got the feed and return lines roughed in yesterday. I'm going to clean the frame up and give it a shot of rattle can before the final installation (since I was in there anyways).

I decided to go outside the frame rail, except for a small portion that will get some extra protection, since I'm going to be building a skid plate that should protect the fuel lines from anything road or trail borne. It also allows me to space them off the rail so they will only be in contact with their mounting points.

I'll try to get some pics today.

 

[davegonz]

Good to see you back at it.

 

[DPV7070]

Quick update:

I've got spiral wrap for the portion of the fuel line that will run inside the frame rail and all the other stuff this job calls for.

But, the combination of not being able to fly, my back hurting, and the return fuel line system is pissing me off

Sooooo...there's going to be some brazing in the near future on a brand new tank just as soon as I grow a pair of bigger BALLS. Good thing I have an old tank to practice on and an already sizable set...

The return line via the vent is just not going to work. So, going to put a hole in a brand new tank and use a -6 AN weld bung with a bit of steel fuel line brazed to the bung that runs at a depth (like the pickup line) just above the bottom of the tank, and then the bung brazed to the tank.

I've been practicing a bit on some scrap and it's going ok. However, I think the rod I'm using might be too thick, yeah that's right I said it , so I might be looking for something more suitable to the task.

Stay tuned to watch me self implode

 

[UZJ40]

What do you fly?

 

[Weber Sarge]

You can use either thinner brazing wire or more heat . If you're welding an old tank need some reading first - gotta stop the chance of igniting old fumes . If it's being done with a mig - gonna have to widen those welds out as bungs welded to sheet metal have a very high chance of porosity . Bring the tank over and I'll tig it ...
Sarge

 

[DPV7070]

What do you fly?

Tiltrotors

You can use either thinner brazing wire or more heat . If you're welding an old tank need some reading first - gotta stop the chance of igniting old fumes . If it's being done with a mig - gonna have to widen those welds out as bungs welded to sheet metal have a very high chance of porosity . Bring the tank over and I'll tig it ...
Sarge

I think I'm going to look for some thinner brazing rods to avoid excessive heat. It's a new tank, so there's no problems with explosions...although, a nice explosion would buy me a really nice Cruiser.d

 

[DPV7070]

A torch was lit, a hole was drilled, and a return line was brazed (term used loosely, ha) in.

Update coming soon...

 

[DPV7070]

Looks like the steel shrunk and opened a few cracks which leaked during the pressure test. More brazing = more cracks. Anybody got a good way to seal a tank? POR-15?

Not happy right now...

 

[jstncse]

That should not be a problem, try heating the area with the torch again and "flow the brass", perhaps you were using too much heat.
I wouldn't try to seal it with anything, if you have to braze it again the sealant will cause problems.

 

[DPV7070]

That should not be a problem, try heating the area with the torch again and "flow the brass", perhaps you were using too much heat.
I wouldn't try to seal it with anything, if you have to braze it again the sealant will cause problems.

This is what I did. I checked it again, no leaks under pressure. Sand blasted it, degreased and then por15'd it. We'll see how it works out.

Here's some pics of my carnage:

Using the old pickup tube for the return side

Brazed on. This would be the last time I felt like I knew what I was doing...

Used the old tank to measure and see where the return tube would be in relation to the pickup tube. No turning back now

Tacked a washer on. I figured this would help distribute stress evenly from the weight of the return line, fitting, etc.

Here's the whole getup waiting to be brazed

Here's the first attempt, but it had some serious leaks.

Final product, blasted and ready for por-15

I wanted to cover that last crack better, but it wasn't leaking under, and I'm ashamed to say I did this, but 90psi.

It looks like a gob of POR, but that's two light coats.

Anyways, the heating cycles are what killed it. I also found out my acetylene regulator is f'd up, so I think that complicated the process and was making things too hot.