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Red Cube mouting possible issue

Flyguytki

Flyguytki

Well Known Member
So I mounted the cube today, it is located just after the mechanical fuel pump before it gets to the silverhawk fuel injection servo. I was pleased with the way it turned out until a buddy of mine pointed out that fuel lines are mounted to the motor and the cube is mounted to the motor mount. Is this correct that the cube/fittings will be prone to cracking due to engine vibrations on the mounts when it it is fixed solid to a non moving piece?

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-david
 
Yep he's correct, especially with the short looking hose you have from the pump.

It's also generally recommended the the xdcr be located between the servo and the distribution manifold.
 
I tried to find a way to put it between those 2 however with the setup I have there just is no room to get it in there with the mounting requirements. I spoke with the EI Guys today and he said there should be no problem putting it where I did. I guess I will ahve to come up with a new mounting solution. Back to the drawing board.

-david
 
I am going to concur with Walt - those lines just look way to short to me, and they are oriented such that when the engine moves, the end fittings will be pulled on with every cycle - that is a great way to have a fuel leak/fire. I'll be honest - that installation looks scary to me.

Paul
 
One other thing, you do not want your fuel lines to go up hill and then back down hill, allowing a place for water and "gunk" to collect.

This may be more important in a carbureted engine but it is still a good practice.
 
Here are a few pictures of how I mounted my fuel flow sensor between the servo and the spider at the right front corner of the sump. I was concerned about mounting it to the engine but so far it's been working flawlessly. I cut up some fire sleeve to insulate the cube and used red RTV to glue the pieces together. The piece of fire sleeve on top insulates the cube from the mounting bracket. The mounting bolts were tightened just enough until the fire sleeve started to crush and then I safety wire the two bolt heads together to keep them from backing out (along with self locking nut plates). In case you can't tell in the last photo, I put two loops of safety wire between the top fire sleeve and the mounting bracket before I tightened the bolts. I then pulled the loops tight to hold the fire sleeve to the cube.

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Hose sealant?

David, are you using RTV as a sealant for your hose/AN fitting connections? I see some on the hose side of your connections and I didn't think this is a place where any sealant is used. Just curious as I'm working on my FWF.
-David H


Flyguytki said:
So I mounted the cube today, it is located just after the mechanical fuel pump before it gets to the silverhawk fuel injection servo. I was pleased with the way it turned out until a buddy of mine pointed out that fuel lines are mounted to the motor and the cube is mounted to the motor mount. Is this correct that the cube/fittings will be prone to cracking due to engine vibrations on the mounts when it it is fixed solid to a non moving piece?

IMG_0847.jpg


IMG_0846.jpg


IMG_0840.jpg


-david
Click to expand...
 
dhmoose said:
David, are you using RTV as a sealant for your hose/AN fitting connections? I see some on the hose side of your connections and I didn't think this is a place where any sealant is used. Just curious as I'm working on my FWF.
-David H
Click to expand...



David, The Red RTV was used to seal underneath the firesleeve before the hose clamp went on. It is not being used as a thread sealant.

-david
 
I would not recommend mounting to the engine... It will work for a while, but the vibration will reduce its service life. I suspect the best place is still in between the gascolator on the firewall and the engine driven pump. You'll get a momentary reading of higher flow when using the boost pump with the cube in that location, but it doesn't seem to affect the accuracy of the fuel totalizing due to the short duty cycle of the boost pump.
 
Snowflake said:
I would not recommend mounting to the engine... It will work for a while, but the vibration will reduce its service life. I suspect the best place is still in between the gascolator on the firewall and the engine driven pump. You'll get a momentary reading of higher flow when using the boost pump with the cube in that location, but it doesn't seem to affect the accuracy of the fuel totalizing due to the short duty cycle of the boost pump.
Click to expand...

This was correct in years back Rob, but I talked directly with the engineering folks that make the red cube when we were mounting ours on Tsam last year, and the design has changed - vibration due to engine mounting is no longer an issue according to them.

Paul
 
Ironflight said:
This was correct in years back Rob, but I talked directly with the engineering folks that make the red cube when we were mounting ours on Tsam last year, and the design has changed - vibration due to engine mounting is no longer an issue according to them.

Paul
Click to expand...

Paul beat me to it but I had the same conversation and I was told it was no longer an issue. I was told that some builders simply allow the cube to be supported by the fuel lines but I didn't feel comfortable with that. It doesn't show in the pictures but in addition to the fire sleeve between the bracket and the top of the cube, I also put rubber washers between the bolt heads and the bottom of the cube. I know engine vibrations are coming through the bolts but my attempts were to isolate it as mush as possible but yet firmly support the sensor.
 
an fitting

I read in some part that the sensor could not have an elbow attached, and you can hold the hose at no more tha 6 inch from the red cube with a adel clamp leaving the red cube "in the air".
 
HSANTIBANEZ said:
I read in some part that the sensor could not have an elbow attached, and you can hold the hose at no more tha 6 inch from the red cube with a adel clamp leaving the red cube "in the air".
Click to expand...

Talked with EI yesterday, as long as you are using flex line you can have a minimum of 3 inches with no angled fittings before the cube and as long as your using flex line again you can connect an angle fitting going out of the cube.

It seems there is no real science to this, I think I hve read on mounting the cube just about anywhere in the system and you will get a fairly accurate reading. Once a decision has been made there are no complaints, now all I have to do is pick a new location. Thanks for all the help

-David
 
Adding to the chorus, I had the same vibration discussion with EI, and was told the same thing regarding the use of elbows, etc. Mine is mounted on a home made 4130 bracket, oriented vertically up, where the left mag would be (electronic ignition in my case). Straight AN4 going in, 90 degree AN4 going out. I have 50 hours of data now. The red cube is dead accurate. Mounted between servo and flow divider, the reading is unaffected by use of the boost pump. I made a point of ensuring that the only fuel line that spanned from moving engine to fixed motor mount or firewall was the line from firewall to mechanical pump.

To the OP, when running anything (hoses, wires, cables) from the fixed firewall or engine mount to the engine, it's important to understand that when the engine moves on it's mounts, it's mostly rotating. On an axis more or less concentric with the crankshaft. Try to visualize how the engine motion will tug (or not) on the item in question before committing to making the connection.
 
Ironflight said:
This was correct in years back Rob, but I talked directly with the engineering folks that make the red cube when we were mounting ours on Tsam last year, and the design has changed - vibration due to engine mounting is no longer an issue according to them.

Paul
Click to expand...

I got the same info from them when I installed mine last year. Thus, it's between the FI servo and the spider, mounted via steel bracket to the sump bolts, and wrapped in a hunk o' firesleeve much as seen here.
 
Thanks so Much for all the help, I have taken everyone's advice and moved the transducer. It can sometimes be hard to hear how wrong you were however I am very glad I asked, my Life's a little more important than my ego.

Thanks again!

-david
 
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Thanks so Much for all the help, I have taken everyone's advice and moved the transducer. It can sometimes be hard to hear how wrong you were however I am very glad I asked, my Life's a little more important than my ego.

Thanks again!

-david
 
Ironflight said:
This was correct in years back Rob, but I talked directly with the engineering folks that make the red cube when we were mounting ours on Tsam last year, and the design has changed - vibration due to engine mounting is no longer an issue according to them.
Click to expand...

I wish I knew that two weeks ago before I started mounting mine... :). Oh well. It's in now, I'm not going to move it.

There seems to be a lot of "misinformation" about these cubes that is based on the old Flowscan sender:

1. Need straight 6" section at inlet/outlet - no longer true, in fact the red cube will work with 90degree fittings on both ends.
2. Mount to non-vibrating structure - no longer true, apparently it can now take the vibration.
3. Mount between engine driven pump and carb - nope, works fine between the boost pump and the engine drive pump. Others have mounted one in each wing to get the flow out of each tank separately, upstream of both pumps.
 
Just my .02 worth-

I've had many customers mount their cubes in all sorts of locations. From tunnels to next to the spider. Between the mechanical pump and the servo. Servo to spider. On the firewall before the mech. pump. All with various plumbing. I havent heard of anyone having a real issue.
Some made changes due to other accessories, but as far as I know of, not because of an errratic flow issue with the red cube. The older flow scan was a different issue.
Tom
 
The "misinformation" seems to come from EI themselves. I have an installation document of theirs that clearly specifies how it should be installed. Their recommendations are non-vibrating surface, no heat, between servo and spider, etc. If they changed their recommendations, they should put out a new install manual (and maybe they have as mine is probably dated).

Pet peeve ventimg time: :( MANY companies serving the experimental aviation market seem to answer an endless line of questions via phone/email from customers asking about their products. This costs them time and frustration. Wouldn't it be cheaper, simpler, and less frustrating for them if they invested some time in drafting a new manual from time to time? Vans is notorious for this. They must receive thousands of phone calls per year asking the same questions time and time again about errors or omissions from their manual. Most companies provide a few page manual that can easily be revised and re-printed, saving them hours of customer service calls. Venting done. :D



Snowflake said:
I wish I knew that two weeks ago before I started mounting mine... :). Oh well. It's in now, I'm not going to move it.

There seems to be a lot of "misinformation" about these cubes that is based on the old Flowscan sender:

1. Need straight 6" section at inlet/outlet - no longer true, in fact the red cube will work with 90degree fittings on both ends.
2. Mount to non-vibrating structure - no longer true, apparently it can now take the vibration.
3. Mount between engine driven pump and carb - nope, works fine between the boost pump and the engine drive pump. Others have mounted one in each wing to get the flow out of each tank separately, upstream of both pumps.
Click to expand...
 
Mods

Actually, it would be great if one of the mods with time on their hands :p would go through all the red cube posts and delete all the old ones with the old information in them.

I read through a LOT of posts because I was worried I'd mount mine wrong only to find in the end that it wasn't very critical.

Put it on the firewall between the electric and mechanical pumps because it was very convenient there. Solid as a rock as well.
 
Red Cube

I know this is an old thread, but wanted some thoughts. I was planning on mounting mine inside, just downflow from the pump. Any thoughts?
 
after mechanical fuel pump

For FI, the best place is between the throttle body and the spider, and 2nd best is between mechanical fuel pump and the throttle body. Anywhere else, and you are providing a higher chance of vapor lock due to the slight restriction of the red cube. Some also report inconsistent fuel flow readings if the red cube is between the boost pump and the mechanical fuel pump, but that would not concern me as much as possible vapor lock.

I put it between the throttle body and the mechanical fuel pump, the 2nd best place, mainly because I was too lazy to re-do the beautiful connection that Mattituck did between the throttle body and the spider.

YMMV, of course!
 
Carl---The 14 plans show the transducer between the mechanical pump and the servo. There are 2 different set ups, depending on whether its a 'A' model or a tail dragger.

Tom
 
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