In-Flight Mixture Control
 

In searching for engines to power ballistic type planes w/ tuned pipes, I've noticed one hardware item that was popular back in the '80's the seems to have disappeared, and that is in-flight mixture control. Piped engines seem to operate in a narrower and more variable mixture range, and it's great to be able to reach down on the tx and tweak it without having to land. In a contest, a lean run can leave you with the choice of aborting the flight/round or risking destruction of an expensive piston/sleeve combo. I've purchased a couple of used Rossi's on Ebay just to get the mixture control carbs. Seems like this would be a good accessory for someone with a machine shop to offer, but there is none that I'm aware of. Anyone know of a source?

RE: In-Flight Mixture Control
 

the novarossi that i was asking about has an inflight mixture control. sounds nice, but i'm not near enough accomplished of a pilot to tell the difference right now.

david

RE: In-Flight Mixture Control
 

I used them when first starting out in pattern. Seemed to make a lot of sense to avoid a lean run. I stopped using them as I became more experienced. I found that I never touched it in flight and the added couple of ounces were not needed.

Stuart

RE: In-Flight Mixture Control
 

All major engine makers in the late 70's - 80's offered inflight mixture control for their engines. I had OS, OPS, Rossi engines with aux mixture control. A lot of marine race engines had the same mix controls. As for a universal mixture control I have never seen one (to many different carbs), but you if you know anyone with a large colection of RCM mags look through as I remember someone offering a inj/mix control for engines.

Cheers

RE: In-Flight Mixture Control
 

Here's one from OS:

http://www3.towerhobbies.com/cgi-bin...&I=LXCN51&P=ML

"Fits the following O.S. Max carburetors; 2D, 4D, 4E, 6B, 7D, 7L, 86, FS-70S, FS-91S, FS-120S-E and FS-120S-SP
Note: This also works with the OS MAX 140RX engine (70A carb)."

The 86 is the carb on the pumped SF and RF. It would probably fit the Hanno, too. But, at $31 it's a little steep.

David

RE: In-Flight Mixture Control
 

If you are looking for a universal item, Perry/Varsane sell one.
best regards,
Dean Pappas

RE: In-Flight Mixture Control
 

Thanks guys. I'm going to order the O.S. one for sure. Seems like locally, I remember using one of the very early Futaba micro servos so the weight penalty was insignificant.

RE: In-Flight Mixture Control
 

Hello,

I believe Webra has those as well.

RE: In-Flight Mixture Control
 

I was a serious competitor back then, and never used one. Conservative needle settings on the ground are all that's needed. If there is a problem in-flight (like the fuel tubing springs a leak, making the engine lean out) just kill the engine and come in. I never thought the extra complexity was worth it.

However, they do work well. For those who renmember the NorthEast crew, Art, Lance & Jeff used them on their EU1-As

RE: In-Flight Mixture Control
 

I ran mixture control on my Webra Dynamix carbs. I got rid of it after a season or so as it was more of a pain than anything. I was running a Perry pump to the carb so once you set the needle on the ground, I never really had to change the mixture while in the air.

Jeff

RE: In-Flight Mixture Control
 

Someone has one for sale for $10 on RC Groups
http://www.rcgroups.com/forums/showthread.php?t=862115
Stuart

RE: In-Flight Mixture Control
 

I remember the O.S. part worked very well. Never really seemed "complex" as the linkage was just like the throttle. Maybe the rock bands of the '60's, un-muffled model airplane motors, and high speed dental drills took a toll on my hearing, as I never seemed to have the best "ear" for setting the needle. At any rate, it always seemed like a nice convenience and even a safety factor, as you could tweak it without having to reach anywhere near the prop. Thanks again for everyone's help.

Dewey

RE: In-Flight Mixture Control
 

Hi
I am also in need to buy one for my 61 rossi
If you find a extra one let me know
Thanks
Leo

RE: In-Flight Mixture Control
 

RCDENT,

In-Flight Mixture Control ?

I think we must talk about:

In flight mixture adjustment!

The picture is of my Webra Speed with mixture adjustment by radio control used for a tuned pipe.
My problem is with this system it is possible leaning an engine without knowing the temperatuur.

For the normal exhaust I prefere a pressure controller on the fue linlet of my carburator (like a Cline but I use my own design). and also a pressure controller and exhaust checkvalve on the fueltank. Both of these controllers I use to get a mixture as constant as possible.
A Cline you can buy.

Cees

RE: In-Flight Mixture Control
 

Cees,

now that's what would, on that side of the pond, be referred to as "splitting hairs" - control, adjustment... a matter of semantics . They both mean the same thing in this context ;).

I never used them (although I have it on an identical Webra w/ Dynamix carb) but it strikes me as though you would want to set the "max lean" point to still be a tad rich when run static. Once in the air, unloaded, the engine picks up a few RPM's leaning out the mixture. The adjustment then allows you to richen slightly to prevent over-revving. Dunno, it strikes me as important to be able to get the engine on the pipe when static and not figure it out in the air.

David.

RE: In-Flight Mixture Control
 

doxilia, i would get ready for a load of proof as to how and why you are wrong. and in broken english so you will have no idea whether you are really right or wrong. i learned a while back to not question at all. i just avoid the situation entirely. (trying to be diplomatic)

david

RE: In-Flight Mixture Control
 

He, he...:D

No worries. If I'm going to put my finger in it, I'll take the heat. [8D]

Honestly, Cees strikes me as a great guy and offers insightful and helpful comments on various threads I've seen. He also takes the time to work up elaborate sketches on things to explain his point. Finally, I'm grateful for the diversity of modellers present on RCU and appreciate the different backgrounds and cultures present. I think RCU would be a lesser place if it weren't for the broad scope it offers. I read and occasionally participate in some of the foreign language (i.e., less universal) forums on other sites and the perspectives can sometimes be a little culturally skewed which sometimes diminishes the content.

I guess the different backgrounds and cultures concept reminds me a bit of events recently transpired just south of the border... :D. Some will be happy, others won't but in any event, it will be interesting to witness what some might describe as a fundamental paradigm shift [sm=wink_smile.gif]

RE: In-Flight Mixture Control
 

Both Davids,

I do not exact understand your posts but I think so maybe I give a wrong response, but let me give a reaction,
I am triggered by: "splitting hairs" - control, adjustment... a matter of semantics

My profession is an instrumentation and control engineer for more than 40 years and my job is to design industrial installations and factories.
In my profession I can speak about control a mixtures ratio (but also speed or temperature) when I can measure it. So measure the physical quantity of both air and fuel.
Only when I can measure these , I can create a correcting element and feedback in a control loop, so servo or valve to keep my mixture ratio (or speed of temperature) constant and /or on the setpoint that I want on that moment.

When I have a mixture (ratio) control I would be happy, because this really would prevent my engine for overheating.

Because it is too complicate to measure the air and fuel flows with high accuracy I use pressure control on fuel inlet of the engine and tank, and temperature detection and guarding on the engine.
When thinking in this direction and making my equipment it is clear for me and so I speak about remote adjustment of the mixtures ratio on my Webra.

Of course, to keep a mixture ratio CONSTANT it is not necessary to use a controller, dosing is also a method and that’s injection, but in that case watch the temperature to check the dosing..

If I am wrong and/or stubborn with this kind of formulating I do not exact know, but it makes it clear for myself. And do not worry I like every reaction and it’s my way of posting the facts.
So do not make a hot item of it, from this moment you know what I mean and there is not a discussion about how it works.

BTW there are people with planes with electrical propulsion! With a speed controller inside? Not for me, it is a VSD Variable speed drive.

Using the adjustment under loading conditions is clear David One, in the air with a resopipe but I think that’s not the discussion.

Cees

RE: In-Flight Mixture Control
 

Cees,

I understand where you're coming from. No one is really taking issue. Being fluent in other languages, I'm familiar with the common, yet typically incorrect, literal translations we sometimes use. This is particularly so with the English language.

All I meant to emphasize is that, in English, in this context, a "flight mixture control" or a "flight mixture adjustment" would be understood to mean the same thing.

I suspect that many modelers (including myself), particularly in this forum, have similar professional backgrounds to yours so we understand each other.

Now..., let's see a model with such a carburetor fixture in operation! :D

Cheers, David.

RE: In-Flight Mixture Control
 

David

That's right,
I don't need(levalve) it.
Look at my thread about the : Redesign and recon........

I am also interested if anybody still uses this system.

Cees

RE: In-Flight Mixture Control
 

That's interesting, Cees! Now that I know we are of the same age I did the math and found that you must have managed becoming an engineer at age 15, ten years earlier than I (1976). You must be one of those legendary engineers being in demand by all employers: not older than 25 and at least 10 years work experience. ;)

RE: In-Flight Mixture Control
 

Hello Ustik.

Maybe,
In 1966 I did start my education on a steel factory, theoretical and practising in instrumentation but also making my first money with that. first diploma's in 1968, age of 17 as instrumentation engineer. In that period I already finished my working 3 channel first tip tip equipment with Metz servo's . Soon after that the proportionals and first fuel pressure controllers but also variometers for gliders.

I did combine work and study many years after that.
Wanted? Not only than, still in this period now on my age of 57 years!! Last project a wastewater threatment plant in Kazachstan!.

Cees

RE: In-Flight Mixture Control
 

Since we're talking professions, my BS is in Eng'g physics (1972). I've spent my career involved with selling and spec'ing industrial sensors for automated equipment.

RE: In-Flight Mixture Control
 

But WEDJ,

You must have the sensors for us. For our fuel ratio controller.
So a fuel flow transmitter and an airflow transmitter,
Supply voltage 5 VDC
Rangeability 1 : 100
Ranges to discus about, depending on the engine

I am making a joke, but interesting, nearly the same profession.

Cees

RE: In-Flight Mixture Control
 

Actually, I work now for Contrinex, a Swiss Company. We make Inductive, photoelecric and ultrasonic sensors, primarily on/off, a few analog devices. www.contrinex.com

Yes, when I saw what you do, I almost laughed. It explains your instrumented Taurus, a marvel of engineering and ideas.

RE: In-Flight Mixture Control
 

hAS ANYONE TRIED THE cARBsAMART BY csm ON AN AIRPLANE? It is designed for rc heli's. It has a temp sensor on the head and a mini servo for the main needle valve hooked to a small computer. You set the desired head temp [for my 50 sized heli it is set at 110C] and it does the rest . It only uses the RX for power and is not controlled by the radio'.

RE: In-Flight Mixture Control
 

I just bought a Carb Smart for my Raptor 30, but I have yet to get into the instructions.

The heli with collective pitch keeps the engine spinning within a very narrow rpm range. Throttle is applied to the engine when the load increases on the engine. This was not done by metering after measuring any engine parameter in real time, before the Carb Smart came along. It was a preset set of throws which had to be adjusted by trial and error after the heli landed.

However, an airplane engine is not focused upon a very narrow rpm band, as the helicopter is focused, so it isn't likely that a heli tuned Smart Carb device will be all that useful unless collective pitch is used on the airplane, which has been done before, long, long ago.


Ed Cregger

RE: In-Flight Mixture Control
 

Interesting thoughts ED. I use a carbsmart on my Raptor 50 and it works great. You will like it alot on your 30. My flight times went up by 3 to 4+ minutes on my Hyper 50. Your thoughts on narrow rpm band of a heli are intereting,, . But load = heat at any rpm band at what ever rpm the motor is. I think it might be worth a try because the carbsmart only uses temp as a guide to open or close the main up to 1/2 turn. [it is adjustable so you can limit throw on either end of travel]. On my carbsmart at idle it will be at its leanest setting that I set and richen under load based only on temp. I don't understand your reasoning about a narrow rpm band being a problem. Idealy you want a constant engine temp that is safe under all load conditions that is all. Maybe I am missing something here. Your thoughts?

RE: In-Flight Mixture Control
 

They're useful for adjusting the top end either in-flight or on the ground as a pose.
The problem is whether you're able to adjust the mid range for example without the specialist carb.
That's an easy test to do before you but or build in the mixture equipment.
Set up the top end and idle as normal, them go to the rich/ lean point and try twisting the needle valve.
If it cures the problem, go for the mixture equipment.
I have a 91FX and a Perry that's still rich in the midrange, even after adjusting the pump and idle needle.
Manually adjusting the needle in the mid range doesn't cure the problem because the carb isn't the type that allow midrange adjustments!
Thus for me it's pointless using the in-flight mixture controls (and I have several including OS) as they do ZIP!
Try the manual test first before you spend money and time.;)

RE: In-Flight Mixture Control
 

I'm thinkin' - I'm thinkin'! <G>


Ed Cregger

RE: In-Flight Mixture Control
 

Turboomni.

In the past I did remark that the old system is mixture adjustment, when looking the way it works.
Mostly a reason for me was that using control it isn’t really the right description.

Now you show me why, because your system is really a mixture control, no adjustment.
I think about the system it is good In a heli, in normal level flight and a nearly constant position of tank versus engine and power range.

When the level of the fuel in the tank lowers the temp will rise and richen the mixture.

I think this system is designed this way because you really cannot measure the mixture in the crankcase only the effect of e lean mixture and that can be the temperature. (oxygen in the exhaust?, WEDJ do you have a sensor for that?)

In a plane I think it is better to control the pressure of the fuel near the inlet of the carb.
Look at my 61 FX, with pressure control on engine and tank.
The position of the plane and g-forces do not disturb the carb anymore, he “thinks” the tank with right and constant fuel level, is right along side him. You automatic have a constant mixture.

Temperatures I also measures and I know the temperature rises very fast when the mixture is too lean.
In the FX the result can be destroyed main ballbearing because of the wrong position of the ballbearing in the crankcase, too far afterwards after overheating and cooling down after that

About the rich midrange David, can that have to do with the normally uncontrolled (and too high?) tank pressure that is used mostly or a too high Perry pump pressure? Because I do not have problems with that, also not with my MVVS 10 cc 0.60 and MVVS 7,5 0.45.

With pressure control the inlet pressure of the fuel to the carb, after the regulator is very low, so the carb has to “suck” the fuel out of the regulator in a situation you can compare with “no tank pressure”.
So when you have a problem with a rich midrange, what happens when adjust the carb with NO tankpressure and NO pump ? Of course not to fly with it, only to see the result of adjusting on the midrange.
When it is oké than maybe a Cline regulator you can use.

Cees

RE: In-Flight Mixture Control
 

I have tried a Cline, Like it until I got air leaking into the fuel line form the regulator to the card. No idea where the air was entering, everything was glued and sealed. Still, it was unusable for me.
Have adjusted the Perry to the max point, any less pressure from the pump and it can't carry the fuel from the CG mount tank.
Point is, unless you have a carb that is designed to allow midrange mixture... like your old Webra and some new heli carbs... an in-flight mixture needle added into the equation may not fix the problem
If the engine responses to manual needle valve adjustments in the problem area, all well and good, go for the servo mixture solution.
If it doesn't... then you're wasting good money. And carrying around an extra servo.

RE: In-Flight Mixture Control
 

David.

The air you are talking about, was that realy air? I do not think so!

When it was an engine with a backplate mounted needle valve it was vapor I think.
When the temperature rises, the crankcase becomes hot, so also the needle valve unit.
Evaporation of the fuel gives bubbles so the engine get more problems, leaning and more temperature rising.

I did remove the needlevalve and use an enlarged Moki carb on my Os Max 61 FX. for this reason.
I could enlarge the bore because the pressure controlles (like Cline) does his work, the carb does not have to make much "sucking" pressure.

Cees

RE: In-Flight Mixture Control
 

David from “Aircraft and Instrument Panel Illustrations”.
I did make an illustration for you from a (spare) part of my aircraft. LOL

I did take a look in the physical date of methanol.
Methanol boils at 65 graden Celcius, 149 Fahrenheit.
65 degrees Celcius, 149 Fahrenheit, isn’t high!!

The OS Max engine backplate is normally integrated with the needle valve, see picture.
I think they later did make the unit separate so the heat conduction to the needle valve is less.

I do measure the engine head temperature near the plug normally above 150 degrees C (302 F). Overheating above 200 degrees C (392 F).
It isn't strange that in some situations , fuel, plug type, crankcase ventilation, propsize, leaning mixture, environmental circumstances (TEMP!) etc, the temp of the needle valve rises above the evaporation temp of 65 C / 149 F !!!!

(That overheating is the problem after the engine stops. this heat in the material of the head of the engine, which is a lot of material, transfers of the other parts of the crankcase.}

When using a normal OLD! carburetor, from the "pioneer days", the needle valve automatic is situated in the coldest part of the engine by the evaporation of the fuel!, also in the summer, but, yes, we with our little engines want everything the big boys have so also “vapor lock”.


Cees

RE: In-Flight Mixture Control
 

Thanks for that.
I'm using a different remote needle assembly than the stock 91fx NV.
Unfortunately, there is no transfer of heat from the engine to this NV that could be causing the bubbles in the fuel line.
The bubbles are originating from the cline. Fuel in is perfect, fuel out... bubbles.
Hummm.
Thanks anyway.

Regarding the cARBsAMART. A couple of the guys are using them down at the strip and are very happy!

RE: In-Flight Mixture Control
 

David,


Than there is something wrong with that Cline, you are right.
There is a membrane inside, maybe there is a pinhole or leakage in that membrane.'
When you can find the thirt opening, so not fuel in- of outlet than maybe you can check.
Put a very little pressure, by blowing, in the outlet (to carburator) with a piece or fuel line and with the Cline under water. Closed inlet.
When you see air bubbles from the third (sensor?) opening, there is a hole in the membrane. When bubbles somewere from the casing maybe a crack in that.
I do not know the inside of the Cline, but I think it is something I show on the picture. I use also a reference to pick up the pressure near the carb.

Succes Cees

RE: In-Flight Mixture Control
 

Very interesting... I'll try it out tonight.
Thanks for the tip.