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Location of Red Cube fuel flow sender.

C

chris mitchell

Well Known Member
I'm trying to sort out the firewall forward of my RV-4, with a Lycoming IO-320 D1A, with Superior horizontal draft cold air sump and Bendix RSA5 AD1 fuel injection system. three steps forward, 2 back it seems.

Current problem is that it appears very difficult, if not impossible, to fulfill all the requirements that are stipulated for the location of the Red Cube. However, it would seems - from reading as many threads as I can bear on a Sunday morning - that the best location for a fuel injected engine, is after the servo and before the flow divider. Is that a commonly held view that most of us could ascribe to?

Am i right in thinking that a pretty standard routing for the fuel line from servo to divider runs from the servo (remember its at the front, not underneath) under number 2 cylinder, then vertically up through the intercylinder baffle between cylinders 2 and 4, and then terminates with a 90 degree connection to the flow divider?

Sooo - can anyone see a problem with mounting the cube directly onto the little elbow that comes out of the top of the servo? I can fabricate a little bracket to help support the cube from the front of the sump/engine case joint.

The only remaining problem as far as I can see is how I actually attach the cube to the servo outlet. The latter is an AN4 male connector; the inlet on the cube is an female 3/8" pipe thread. I cannot see an AN fitting that will give me this combination of connections, so I would need to use a short length of pipe and an adapter in the cube. Any better suggestions?

I could put the cube up at the flow divider end, but I am still left with the 3/8 female pipe thread to a male AN4 flare problem.

As ever, thanks for help!

Chris
 
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Chris, I chose to mount mine directly under the flow divider. Anything downstream of the servo will give you the best fuel flow readings. I routinely compare what my fuel flow says I have burned to what I actually pump when I top off and it’s always less than 2 gallons and most of the time less than a gallon difference.

Edit: in re fittings, here’s where I got what I needed: http://www.titanfittings.com/product-p/ss-6501.htm
 
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The raw flow divider ports should be NPT. Mine were, and I used a short male/male NPT nipple to attach the transducer to the divider. "Hard" mounting is not reccomended, but it served me just fine for 300 hours.
 
Chris, we helped Mark and others with this install. Its out of the way, and in cooling air. And with it very near the centerline of the case, we felt that vibration would be negligible versus other locations. Mark opted to use a stainless fitting instead of the steel ones we use, and that is excellent.

Tom
 
I just went around the tree on this myself. This is what I did in the past:
- RV-8A with backfitted AirFlow Performance injection, the Grand Rapid fuel sender (smaller than the Red Cube) in the line between the throttle body and spider, with a large diameter firesleeve around it. Has worked perfectly for 1000 hours.
- RV-10. Red cube mounted in the tunnel per plans (between the boost pump and engine pump). Easy mount. The flow changes when you turn the boost pump on but goes away. Overall accuracy alway within a half gallon of actual over 500 hours.

For the new RV-8 I re-read the insturctions. No hard mounting to the engine, no angled fittings on the cube, up slope, etc. I finally decided on a couple of adel clamps to hold the cube on the engine mount, between the engine pump and the throttle body. This spot meets all the instruction guidelines.

Carl
 
So Mike if I follow correctly, I?d put an AN 912 reducer in the top of the red cube and then an 04 p4 stainless elbow to connectto the divider inlet? The cube would be vertical and located in position by the elbow alone?
Have I got that right?

Thanks
Chris
 
In my installation, it was a an816 from the flow divider to the stainless elbow fitting I linked earlier and then the red cube, then another an816 that allows connection to your flexible fuel line. I?m away from the hangar and can?t remember all of the exact sizes but you want to match the outlet of the servo all the way to the flow divider. I wouldn?t think any reducers would be a good idea
 
chris mitchell said:
So Mike if I follow correctly, I?d put an AN 912 reducer in the top of the red cube and then an 04 p4 stainless elbow to connectto the divider inlet? The cube would be vertical and located in position by the elbow alone?
Have I got that right?

Thanks
Chris
Click to expand...

This is not a red cube but the concept is similar:

2vlwbyd.jpg
 
Here's a picture of what I'm describing, although this isn't my particular installation. It is very similar though.

IMG_2165.jpg
 
It's generally considered bad practice to place a flow meter in close proximity to flow disturbances such as elbows, sudden changes in pipe/tube diameter, and other obstructions. I don't know the details for the red cube, but would imagine this holds.

Usually leaving 10 pipe diameters upstream and 5 or so downstream of a flow meter is considered OK, depending on the type of instrument.

Based on my experience with industrial flow meters I would avoid installing a 90 degree elbow directly before or after a flow meter if at all possible.
 
Carl Froehlich said:
- RV-10. Red cube mounted in the tunnel per plans (between the boost pump and engine pump). Easy mount. The flow changes when you turn the boost pump on but goes away. Overall accuracy alway within a half gallon of actual over 500 hours.
Carl
Click to expand...

Carl,

What do you mean by "it goes away"?

I have the red cube in this position and see the same behavior when turning pump on. But I see about 2 gallon error or more depending on total time I have the pump on between fueling.
 
jwilbur said:
Carl,

What do you mean by "it goes away"?

I have the red cube in this position and see the same behavior when turning pump on. But I see about 2 gallon error or more depending on total time I have the pump on between fueling.
Click to expand...

I guess I don?t run the boost pump as long as you do.

Carl
 
Carl Froehlich said:
I guess I don?t run the boost pump as long as you do.

Carl
Click to expand...

Maybe that's it. I've been doing lots of short flights with lots of takeoff and landings. Good news is the error is always in "the right" direction in showing less fuel than is actually there.
 
Mark - thanks for that photo, exactly as I imagined and helpful to have it confirmed.

The pipe diameter is 1/8 so I this setup I?d guess that the 10 diameter rule is just about ok through the first section of the elbow. I guess it?s just a necessary compromise to get the cube in place after the fuel servo. The alternative is to have a section of tubing but then the cube would just be dangling, down between the cylinders, or else more pipe work wth the cube on top of the engine, and tubing looping around and back down.

Out to the work shop to stare at the engine. I?ll post a photo of whatever I finally decide and install.

Thanks to all for their input.

Chris
 
Mark - if you hang it off the spider recommend using steel fittings. You may want to do some sort of periodic inspection of the spider to make sure the weight of the cube and associated moment arm during vibration is not causing problems (fatigue cracks and such). A call to Don at AirFlow Performance (if using that system) might be worth the time to see what they say.

If possible, consider a bracket across the top of the engine to mount the cube in about the same place but not solely supported by the spider.

Carl
 
Chris---The pic Mark posted is the way we've done them for 5 years. AN816-4 (1/8 npt to -4) STEEL or stainless into the flow divider, Industrial 6501-4-4 (90* -4 JIC/AN to 1/4 npt) STEEL or stainless on the outlet of the flow transducer, and a AN816-4-4 (1/4 npt to -4) straight STEEL or stainless for the inlet of the transducer.
As some have stated on VAF, its good practice to have some straight flow into and out of the transducer. That was generally for the old FloScan. It certainly didnt like turbulent flow. BUT, the cube is a more robust transducer and has shown that it really doesnt care. A bunch of RV's and others are flying this configuration. Yes, we consulted with Don about this a long time ago when we were looking to make install packages. Different configurations were test flown by Team AeroDynamix in 2 airshow seasons, with excellent results.

We asked EI for a 'recommended" install location, and never got a straight answer. So and extend flight test program with several other beta testers was done.

So---why did we do it? Simple---with all the different sumps, servos, and exhausts, yes exhausts, there is no way to have a 1 kit fits all. Even the RV14, were the cube is located in the plans between the fuel pump and the servo, has 2 different hoses for the 2 different models of planes. WE found that most guys needed 2 hoses, 1 long and 1 short for their installations. 1/2 the time the short hose needed modification die to installation issues. So we tried to make it easier by putting it at the flow divider, and even that doesnt work in every case.
Carl---yes we've looked into a bracket at the flow divider, like a purge valve bracket. Just havent gotten there yet.

But to answer the question, yes it works, yes its in cool air, and yes its an easy install.

Tom
 
I'd add that this installation works in terms of accurately measuring fuel flow. I went out this morning and filled up. The red cube told me I needed 29 gals, I topped off with 28.76 according to the pump. This was after flying a 3 leg Pilots N Paws trip last week, and adding 10 gals before the third leg. Lots of high flow, low flow up and down and it still was that accurate. I'm very pleased.
 
While we cannot give exact installation advice as each aircraft can present its own unique set of challenges, here are a few requirements and recommendations:

1. The flow transducer must be installed after any and all fuel pumps.
2. The flow transducer should be installed by suspending the transducer from flexible fuel lines, using adel clamps.
3. The flow transducer should be mounted horizontally, with the wires pointing up. If it is to be installed at an angle, ensure the output port is facing up to allow air bubble to evacuate the transducer.
4. 90 degree fitting are not prohibited, but can cause turbulence, resulting in difficult to calibrate K-factor settings.
5. The flow transducer should never be installed using hard lines to the engine, creating leverage on a fitting or boss that may break due to its moment and engine vibration. Such a break could be a fire hazard.

If anyone would like additional information, please PM me your e-mail address and I will be happy to send you our installation instructions.
 
Dave----I think that most builders are using 'similar' engine types, like injected Lycomings. Yes differences in sumps, servos and exhausts for these non-certified planes to sometimes create some installation issues.

But what I think MOST builders would want is a recommended location for the transducer. Us included. And because we asked that question 8 years ago with a similar answer, we tried to find a good compromise.

All indications is that it works. So has EI done any testing with the cube in different locations and attitudes?

Tom
 
I have installed the "cube" in many different locations over the years in numerous aircraft. Some of the locations are in the "list" of bad locations that was posted. All installations have been accurate. I suspect the cause for inaccuracies have more to do with how exact you fill the tank to level each time rather then the location of the cube.
 
darata said:
While we cannot give exact installation advice as each aircraft can present its own unique set of challenges, here are a few requirements and recommendations:

1. The flow transducer must be installed after any and all fuel pumps.
2. The flow transducer should be installed by suspending the transducer from flexible fuel lines, using adel clamps.
3. The flow transducer should be mounted horizontally, with the wires pointing up. If it is to be installed at an angle, ensure the output port is facing up to allow air bubble to evacuate the transducer.
4. 90 degree fitting are not prohibited, but can cause turbulence, resulting in difficult to calibrate K-factor settings.
5. The flow transducer should never be installed using hard lines to the engine, creating leverage on a fitting or boss that may break due to its moment and engine vibration. Such a break could be a fire hazard.

If anyone would like additional information, please PM me your e-mail address and I will be happy to send you our installation instructions.
Click to expand...

Sure you can do however you want but I think following the advice from the guys that make the cube, and likely have been doing this longer than most of us, would probably be the prudent and safe way to plan your installation.
 
Agreed Walt----if they were to give us a recommendation we'd make a package for it. That recommendation probably isnt coming anytime soon. So in response to builders requests, we worked on the problem.

Not trying to start a flame war here. WE asked for a recommendation and received none. So attempting to work in the criteria they published, we came up with a few different ideas.

Tom
 
TS Flightlines said:
Agreed Walt----if they were to give us a recommendation we'd make a package for it. That recommendation probably isnt coming anytime soon. So in response to builders requests, we worked on the problem.

Not trying to start a flame war here. WE asked for a recommendation and received none. So attempting to work in the criteria they published, we came up with a few different ideas.

Tom
Click to expand...

Tom,
I don't think EI can recommend a location for the RV except for the info they have already provided, the truth is everyone has a "better idea", some may work but fuel systems, can be hazardous to your health if they fail. So based on the current recommendation from EI hard mounting to the spyder would be contrary to their guidelines.

I have lots of customers request things, I have no problem saying no if I think it is outstide "standard practice", manufacturers recommended guidelines or my personal comfort zone.
 
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I think the best place to mount it would be a location that you can mounted to be safe in terms of vibration, heat and other factor that could possibly effect the fuel lines or the life of the transducer. In my RV7A, I mounted in the tunnel between the electric fuel pump and engine driven pump. The accuracy was within 0.5 at most, most often within 0.3G. This is when I filled the tank to the top and flew it till the next fill up and I filled it again to the top, usually during X-country trip.

In my RV14, it is mounted after the engine driven pump but before the servo. This is what VANs recommends and look to be a good place.
 
As we are the manufacture of the cube, not an approved installation facility, we can only make general recommendations based on how the part was tested. Aircraft can be modified in multiple different ways that could alter a specific installation guide, making such a guide practically valueless. Especially in experimental aircraft. Additionally, we do not employ an A&P. As such, specific installation questions should be posed to a licensed mechanic. Lastly, AC 43.13 can be referenced for the FAA's acceptable methods, practices and techniques.
 
Dave---first we all like the cube. For our information, when EI did the tests on the engines, where did they mount the cube? I'm assuming that running engine tests were done. I guess what I'm asking is what was the installed location(s) during the tests, and we'll mimic those and develop an install package for them.

Again----not trying to flame a fire here, but trying to solve a couple of problems that builders have.
Walt---I agree and there are certified installations out there on engines like those in RV's and other experimentals. If the cube is installed on the engine, it doesnt know if its on an RV or a certified aircraft. It just knows that its either between the pump and the servo, or the servo and flow divider.

So, if EI will tell us where they mounted it for testing, then I would think that would be an approved location. Using that information, we can make an install package thats safe, and approved--at least by the test installation.

Guys----I think there are alot of us out there that have some ideas on the cubes install location. Some of those may or may not adhere to all the criteria. WE certainly have everyones best interest in mind.

Tom
 
I have replaced a number of these units on various customer aircraft, as well as my own. It seems to me they have a weakness to heat and vibration.
The best location for accuracy is between the servo and the flow divider. This leads every one to consider somewhere between these two components. And that puts the unit somewhere on the back or top of the engine. Right where the heat and vibration accumulate.
I mounted the last install on a aluminum plate adell clamped to the engine mount. Others I have seen adell the cube directly to the mount. This helps isolate the vibration and puts it a little lower in the cowl to avoid the oven bake that occurs after shut down. The install instructions mention a firewall location. This would also work if there is space available. There is the additional hose length and clutter to consider.
 
Mark Dickens said:
Here's a picture of what I'm describing, although this isn't my particular installation. It is very similar though.
Click to expand...

Mark, if you know the source of the photo, be sure to contact the builder
and tell him to replace that blue aluminum fitting with a steel fitting. Much bad juju there!

IMG_2165.jpg
[/QUOTE]
 
DanH said:
Mark, if you know the source of the photo, be sure to contact the builder and tell him to replace that blue aluminum fitting with a steel fitting. Much bad juju there!
Click to expand...

Agreed. This is a photo forwarded to me by Tom S. My installation is all steel.
 
Dan, Tom and Mark---yes the installer changed the aluminum fitting to steel. On the fitting package we market, all are steel fittings. That customer just bought the 90* fitting, and YES was told to change the nipple after we saw the pic.

Yes, the transducer is in cooling air, and he and others havent reported any issue.
BUT---we are always looking to improve things, and this install, even though it works well, certainly falls into that catagory. Thats why I was trying to get Dave to give us a recommendation. They kinda did with the install guide for the computer. but as we know, not all installs are the same. YES----it would be fabulous to mount them low, near the servo, but, gee that heat thing crops up again. SEVERAL installs with it in the lower location, and no issues. BUT, because not all sumps, servos, and even exhausts are created and installed the same, that means a singular install package isnt going to work. There will be 2 hoses, a short and a longer one, and just about always the short one is mismeasured. Even 1/4 inch makes a difference. So our thought of eliminating 1 of the 2 hoses would make the install alot more universal for more builders.

So, we'll continue to work to improve this install. Any one have any great ideas, we'll certainly listen!

Tom
 
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Tom and Bruce, Yep, heat is a consideration.
We've installed these near the rear baffle; near the servo under the #1 cylinder/sump area on a Rocket, under the #4 cylinder like on the RV14s;
on top of the engine mounted on a plate adel clamped to the pushrod tubes; just about every place we can think of. Early day of testing these install locations was with an airshow team. Various locations and install hose packages. So multiple testing scenarios at the same time. We didnt hear of any issues.
Lee's Rocket has it mounted under Cylinder 1 near the intersection of the sump and cylinder. No issues. Paul Dye on the RV3 has it mounted low, above the servo at the sump parting line. No issue that I've heard of and I'll bet he flys as much as anyone. Several had it mounted vertically, under the Right lower baffle, with a short hose to the servo. Many more have it mounted on top of the engine with various connections to the flow divider, both hose and fittings.

NO we havent put thermocouples in these areas to see what the temps are--anyone want to do that? Same for the upper location. I'll bet that it really doesnt matte as much as we think---the cube is pretty robust.

Again---looking for ideas--
Tom
 
Here is what I did. A short line from Tom and the line to the divider is supported a few inches past the cube. Hopefully this will reduce vibration. Not run yet still building.
AF1QipMPU779hDjZesUK1opFOeZ11FceHGyTrVlTMs1C
 
With Tom's help, I mounted my red cube underneath the 1-3 intercylinder baffle and after the servo on my -9A. The in and out hoses are roughly equidistant from the servo and purge valve/flow divider complex respectively and the cube sits right below the intercylinder baffle, oriented just off vertical and seems to be doing just fine. The exhaust is the trombone style from Vetterman. I just ordered some 1 time use self adhesive circular temp indicators from McMaster Carr today. The temp ranges are from 230F to 400F. I plan on flying trips and recording the temp on the cube. I'll report the results.

David
 
is the red cube sensitive to vibration?

Is vibration a consideration for the electronics or the spinning rotor?
 
Cube

NLPete said:
Here's my compromise.
vqsbyo.jpg
Click to expand...

I did the same thing exempt mine is connected directly to the 90 out of the servo. With a 45 degree fitting on the out side up to the spider. There was about an 1/8" clearance between the cube and the servo that I filled with high temp RTV to stabilize itwhich probably wasn't needed but did it anyway. The 90 fitting is made of steel. That you Tom for making up the fittings and hose.
 
I am not yet finished but I will install mine as welle between the servo and the spider. I did not want to let it hang freely so I made a bracket out of 4130 and installed the Red Cube on some rubber standoffs. The fuel line will go through the inner baffle up to the spider. I just need to corrosion protect the bracket and let TS do some fuel lines which fit. The open holes on the bracket are for a nutplate to attach a p-clamp for the starter cable.
(And yes of course I will replace those lock nuts with metallic ones for the final installation.)
5jtavm.jpg

15d8ln5.jpg

2mcwzk3.jpg
 
Yep we can make some short hoses. The trade off for the short length is that the hose has less flexibility because the stems of the fittings are internal in the hose, and the distance between the 2 is short. Example---for OUR -4 straight hose ends, the end of the stem to the inside flare of the fitting is .750. So for a 2 inch long hose, that leaves .250 of free space between the stems for flexibility. OTHER fittings will have a different dimension. The one picture above is probably 1.25 flare to stem, so you can see that a really short hose would just about be a rigid tube. WE try to get a minimum of .500 between the stems if possible---depending on the application.

So we'll keep playing with this.

Tom
 
This is a GREAT set of posts with photos of installations with the IO series of engines. Does anybody have photo(s) of an installation on a Lycoming O-360 engine?

:cool:
 
Here is my IO360 mount in prototype fitting mode. I could not find those nice rubber standoffs (like YvesCH) and used baffle material in a "U" shape. Just did not want all that high freq vibration from the sump. The bottom of the U is riveted to the 4130 bracket. The the fitting hoses were sent to Tom along with the stock hose for modification. The baffle material has really weak stiffness in the rock and roll axis. Keep in mind that the hose connecting to the spider will be really stiff in the vertical axis, i.e. along its length.
oRgHxAlAveA8yLsy7R9n6L073jchZBg5SlhE5J1GHtmRY72U_ps6-DqdppOjB6heGYSYMRUnRf587w1t43pyZaiwbL5uQsvAKPaRaU6dzCXsUFYFyudv7Pc7HnhQedOTFcomnKMgx-NVBRFuFwXpYBj0FKRYyM1b8lcdUv7OEZpURsxedlpNmcpj2o-M4_TP05924h_WJ6em50-V7D6vfecqIkYbuWINXKW_kLgaKa6Ei-8QZF-8tDPmtHpE7ns4oq3isDcmxypAuV0osiC6CqemiFsEZ9ABBFHxlVjLcPaDYNaNIBWSPExN2JhI2WLKqIq1t_5fHZhInfCgEowwSRC7Tj_-1mRfBC8HM211QVocuiUgnOJM6ukG2BhQZbO9FjQx_R8fjgoCEOJcATZz25_U29Zq5wnBLvdv05XdOQWGh7YSVcVA-cLFPy5DsEH6_V3oA4GA840wqcpCxsP1bKc6LdNqYcj6FtIies1dtOot4CKCqlWet4cbW5RwcrSqRbtec9QwOoLV-387-DpqnzTHQUy_AQcpDM6AibbRqJSWZLJATLNUSFkyBKrg3WwXU4BSiUH_lYIu9o4p6k727ib4tFsFzb-l3qt7pS80aB0PvjuddXzRCiinSf3LU2tBlUZxvPtUje0Z1Z9QsYaYlGnu4YeimTBIki3vVeD3s9R6HR1fufv3z56e=w538-h717-no
 
Come to think of it,

Bill has a great idea there. I remember back in the automotive days these little threaded rubber mounts for stuff. McMaster Carr has rubber bumper cushions, threaded and unthreaded, studded and unstudded. For those using the lower near sump location, and didnt want to hang the transducer from the hoses, using a couple of these with a 'mounting bracket' would stabilize things, and dampen the vibrations.
Still goes against EI's published statement of not mounting the cube, but suspending it, but better than hard mounting in that location where 2 hoses are needed. Like ALOT of builders, Bill has chosen a vertical orientation, and that too goes against EI's published statement, BUT also DOES WORK, as shown by alot of flying installations. So, by isolating the cube by some rubber bumpers on a bracket, this might be an option for some builders.
Look up bumper cushions on McMaster Carr.

Tom
 
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