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Red Cube mounting solution?

agirard7a

Well Known Member
Per recommendation of the manufacturer, the cube is to be mounted downstream from all pumps. I came up with this mounting solution which seems it should work. Please feel free to comment if anyone sees potential problems here. This is mounted on an 0320 carbureted standard Vans cable attach bracket. I built my own hoses and have yet to fire sleeve.

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From an old country farmer

While ferrying an RV 7 from TX up to Denver, all the bell and whistles went off when a fuel line broke inside the AN fitting on the fuel servo. It was mounted much like yours.. One mans opinion, never mount a sensor or transducer on the engine, there is just to much vibration. In the ancient past, a couple of years ago, it was recommend that you mount the fuel flow transducer on the firewall with a couple of inches of straight flow before and after. Dave
 
While I don't see any issues with the mount itself, I'd recommend two things. Replace the aluminum AN fittings with steel, and send those lines to Bonaco and have them duplicate the length with braided stainless lines.
 
Mounting?

Dave, thanks for that response. I purposely mounted
In this fashion thinking if it was mounted on the fire
wall, there would be greater movement of the outgoing line
From the cube to the carb due to the static mounting on the FW.

However, I need to listen to experience.
My thinking is that although there is fibration when mounted
To the engine, the Cube and lines would all be as one. I also am
influenced by past posting on this issue.

I will speak to the manuf. of the red cube and get their
opinion on this. I will be sure to post as others are dealing
with this issue. Again thank you.
 
I think that tight end radius on the one side will put significant lateral stress on the AN fittings ...enough to be a concern. As others said, steel would be better.
The EII/red cube people told me that it needs to be mounted with flex lines on both sides (which you have). When I questioned if they meant that requirement for cubes piped to the engine (because of vibration), they said no ...regardless of location. That seems to fly in the face of hundreds of RVs that have the red cube hard piped on the cabin floor ahead of the FI pump/filter without leaks or troubles.
My experience with EII was not good; I came away with zero confidence in what they told me for a number of reasons. FWIW.
 
The perfered way is to have approx. 4" straight inlet and outlet on cube bends near cube create turbulance and create eronius readings also steel fittings would be perfered.
 
I especially agree with the steel fittings replacement, I recommend steel fittings on all FWF lines personally. Tight bend radius and short line are also not the best arrangement (the short line acts like a rigid line with virtually no flex).

Another point from a maintenance stand point, cleaning the inlet screen on the carb with your setup will require removing the "cube" to get the short line off the inlet fitting. I'd be cussing you at annual for not thinking about maintenance.
 
Bit of a conundrum.

Great input. Thanks to all. It would be great to have a straight
Run in and out and understand the need. However with the limited
Locations to mount this thing I am not sure at this point how to accomplish this.

I will for sure change out to steel fittings. However, I have some very
intersting feed back about the stainless lines. Apparently, certified aircraft
do not use the stainless lines which my AP confirmed. The Teflon inner lining
Is more susseptable to heat and wear and have had known problems.
The hose I am using is 303 hose an apparently very dependable. Just an FYI.
Also the aircraft company that sold the hose told me the same story. He does not stock the stainless as most of his market is certified.
 
Change of plan

After some great input from some experienced
folks. (exactly what I was hoping for). I am changing
the mounting location to the fire wall, in the process making sure there is long straight as possible long runs in and out of this thing to absorb fibration.
Using steel fittings and keeping the 303 hose. Will post pics when done.
 
Follow up from an old country farmer

Routing for the fuel line would be, thru the fire wall then 303 to the fuel pump, 303in a large circle to red cube on the firewall then 303 again to fuel servo or carb. This has worked well on my 4 my 6 and on my 7. Dave
 
Hey Al. Most of us that build hoses, firesleeve all FWF hoses. Granted, if you expose a teflon hose to high heat, it can fail. (firesleeve protects it). If you allow the outer braid to contact a bracket, a mount, or anything else, the braid can be damaged, and a liner could fail. Again, as Walt said, good planning is the best policy. Whether you use 303, or teflon, at least firesleeve your fuel hoses. The cotton outer braid can burn pretty good under heat. There is steel ( not stainless) reinforcement, with a nylon reinforcement, then the a nitril (rubber) liner. Protect it. Whichever way you choose to go.
Tom
 
Note that the manufacturer no longer recommends 4" or 2" of straight hose on the inlet or outlet. In fact, they say it will work "just fine" with 90 degree fittings on either side. Still, for smooth flow in lines in general you'd want to avoid that unless absolutely necessary. The straight hose requirement is a holdover from the old fuel flow sensor, which was not a red cube and which I understand used different measurement technology.

Note also that the gauge will read just fine when mounted between the electric and the engine-driven pumps. Two tanks so far on mine and the fuel used has matched the fuel added within .5 L on each fill up... No calibration needed.
 
This is how I installed it.
The idea was not mine. I copied someone else on this forum.
Installation is 90% compliant with red-cube instructions (they say that also the outlet should be straight). Readings are accurate.
I now have 150 hours of flight and everything is OK (only had to change the red-cube after 30 hours because it stopped working).
I made the braided steel hose and then covered it with firesleeve (I bought the tool on Spruce).

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Timely Topic

Anyone mount the red cube to the back side of the Brake Bracket doubler? I've been scratching my head for a place that's close and thought why not? There's plenty of room on the other side for attachment hardware.

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This is what I did with the red cube: I fabricated an aluminum angle and used adel clamps to mount it to the engine mount - no need to drill holes and easy to replace if it doesn´t work. On this angle I mounted the red cube. See pics:

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Large circle? bend radius & slack?

Dave. Could you send me a picture of your installationas well? Thanks. Email to: [email protected]

I had the same idea in mind for the installation as you did, but got some doubts concerning bend radius and slack of the line, yesterday. I thought to use AE466 hose but it will probabaly not work out with these.
 
Here is a note from Jan 9 2013 on a red cube mounting discussion:

I talked with the factory before mounting my red cube. They preferred it on top of the engine with a straight flow in and a straight flow out. They said the vibration will not be an issue. I have an IO360 M1B and it was quite easy to mount. I got a bracket exactly like the fuel spider mount for the injection and put it on the other side. You can make on or buy one from Lycoming. The one is offset from the other in the forward aft direction and they are on either side of the centerline. I also have a top plenum for the cooling air and it fits quite comfortably.


If you need pictures, send me a note and I will take some.
There are other discussions on this subject if you search for them.
 
I have mine mounted to the engine. It is the red cube, and is working fine. As the previous poster stated, it is perfectly acceptable to mount it on the engine. I agree that you should uses steel braded line with steel fittings and fire sleeve. It does need to be after all the fuel pumps to obtain the best accuracy.
 
My -9A is set up to fly from the RHS, so I made a simple bracket out of .125 and, with a reinforcement plate on the aft of the firewall, made use of the 6x unused holes that the flex brake line bracket would normally be mounted to.

It is downstream of everything, and with a couple of custom lines from TS and fittings from Earls, will fit easily, and with minimal bending stresses on the hoses.
 
YMMV,

210 trouble free hours on this setup (picture while under construction)

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- massive stainless steel bracket to mount to the engine.
- steel fittings only
 
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