blueflyer

blueflyer

Well Known Member
I have searched the archives about the Red Cube installation and did not see an answer to my question, so please excuse me if this has been answered already.

I was thinking of installing the red cube on the throttle bracket. I have seen where vibration has been discussed as being a bad thing, but I also saw where some folks actually bolt the red cube to the oil sump itself. That seems a little conflicting, so it seems that vibration might not be such a big issue. The throttle bracket is about the same elevation as the carburetor, so I could avoid the fuel line curving down after leaving the red cube (a downward pointing fuel line downstream of the red cube is discouraged in their literature). This way, the fuel line leaving the mechanical fuel pump would go straight towards the ground where it runs into the red cube mounted on the throttle bracket, then the fuel line runs (basically) at a zero elevation change from the red cube to the carburetor.

What would be your thoughts on that installation location?
 
In my opinion the red cube dos not have to be mounted to anything except a fuel line in and out. A clamp might be needed to secure the fuel line and that could be bolted to the throttle bracket or the sump if necessary.

Mine is hooked up vertical between the fuel controller and flow divider. There is nothing in the area to bolt it to and I think it is ok. It does work so far.
 
I was mounting mine against the firewall, someone pointed out correctly that it should only be mounted on a horizontal surface, due to some sensitive bearings inside. Just saying.
 
Mine is hooked up vertical between the fuel controller and flow divider. There is nothing in the area to bolt it to and I think it is ok. It does work so far
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Further to above, I have seen an installation advice document saying:
(LAA) Both transducers are designed to be rigidly mounted with the electrical connections pointing up (to allow vapour venting).
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The wires MUST NOT come out of the bottom of transducer. Wires pointing up is the best
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(Dynon)When placing either sensor, ensure that the three wire leads are pointed straight up.
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I could easily place the red cube horizontally (and with wires up) on the throttle bracket. It seems like an ideal location, but I am concerned about vibration the cube may feel from being attached to the bracket.
 
Can you get Five inches of straight line in and out with out a 90 degree or 45 degree in the cube?



William
RV8A flying
RV7 finishing
 
Kitfoxbill said:
Can you get Five inches of straight line in and out with out a 90 degree or 45 degree in the cube?



William
RV8A flying
RV7 finishing
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I dont believe the modern cubes require that. Correct me if I am wrong.

Edit: After discussing with EI the red cubes have no such requirement.
 
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I don't recall seeing a 5 inch minimum of line on either side of the red cube. From reviewing the archives, it appears the 90 degree/45 degree fitting are no longer an issue.
 
An old post of consolidated info from the horse's mouth:

Mathew Sharp said:
As far as I know Dynon distributes both the FloScan 201B as well as EI's FT-60.

The FloScan unit is much more sensitive to the angles/fittings entering and exiting the unit. EI's unit does not care. You can run 90 degree fittings in and out of ours without problems.

JPI does not sell EI's FT-60:cool:

Maybe you can get Dynon to trade you for a FT-60?

Good luck!

Matt
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Mathew Sharp said:
You do NOT want to rigid mount the transducer to the motor (any part) using just a fitting. It is a huge safety issue. The fitting could theoretically fatigue and break. You absolutely need to have flexible line on both sides of the Floscan 201B or the EI FT-60 (that Dynon now utilizes).

After manufacturing/supporting flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after both fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more. Frankly we don't care if the thing flows straight up, or if you put 90-degree fittings in and out (FT-60 only) of the transducer. Just don't mount it upside down or flowing sharply downhill.



Hope this helps,

Matt Sharp
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Mathew Sharp said:
Hello All!

Your friendly neighborhood EI Tech support rep here!

There are really two issues in regards to EI?s specifications on flow transducer placement.

1. Accuracy of the output of the flow transducer.
2. Safety.

Issue one is pretty basic. After manufacturing flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after the mechanical fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 and 231 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more.

The other more serious issue is in regards to safety. We want to make absolutely sure that the fittings on the transducers never are subjected to conflicting vibration planes. The engine will flex in the motor mounts creating conflicting vibration planes between the engine and the airframe. This is why the ?flexible line in? and ?flexible line out? is called out so often. This is also why we don?t want the transducer rigid mounted, via a fitting, to a carburetor or fuel pump. A contradicting vibration plane will focus the energy directly to the fitting. It is our sincere concern that with the two conflicting vibration planes here could cause the fitting to fatigue and crack. This would be bad?and we have seen it happen?.

On the bright side, we don?t care if the thing flows straight up, or if you put 90-degree fittings in and out of the transducer. Just don?t mount it upside down, flowing sharply downhill, or before the pumps. :eek:

Please let me know if you have any questions or if we may be of any assistance.

Matt Sharp
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Thanks Brian, that (those) post(s) is my understanding as well. I was going to gather the info but decided to work on my build this morning instead. Learning to search the forum is a skill all builders should learn, it would have yielded that information pretty quickly, that is what I did some time ago.

I really like the benefits of mounting this cube after the mechanical pump as it gives the greatest vapor/cavitation margin at higher temps and/or higher vapor pressure fuels.
 
Brian
your posts in the archives (and now listed here) were spot on. I spoke with EI this morning. They didn't care about the vibration as long as the vibration was from one source (ie the cube was ok on the throttle bracket, but don't tie the throttle bracket into something else where I would get 2 sources of vibration).

They also didn't care about the 90*/45* fittings, but said if I was to use a 45* or 90* into the cube, I should use the matching 45*/90* fitting on the side leaving the cube.
 
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Does the red cube have to be physically mounted, or is it OK to suspend it in the fuel line between the mechanical fuel pump and the carburetor?
 
Does the red cube have to be physically mounted, or is it OK to suspend it in the fuel line between the mechanical fuel pump and the carburetor?


I suspended mine. It weighs not much more than the fuel line it replaces. The fuel lines are quite stiff and therefore provide sufficient support.

Doug M
 
EI would be more than happy to answer that quick question with a phone call. I should call them and ask them. I too thought about that avenue, but it didn't seem too much more difficult to mount it.
 
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