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Do what yer' Momma said...
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Fuel sender float wire - View Thread
Let's see if I have this right before I cut anything. According to the drawing...the X (length out from the sender unit) for the float wire should be 3 1/4. The Y (distance from the X to the top of the float ball...should be 3 1/4. I assume that means we cut the float wire to meet those specs. It seems obvious since the length of that wire is about a foot but I don't recall it being mentioned anywhere. And what did we all finally decide on the rubber gasket for the sender unit. Toss it?
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Fuel sender float wire - RE: - View Thread
Yes you can cut it. The idea is to have the float reach the max up stop on the sender just prior to it hitting the top tank skin and max down position just prior to hitting the bottom skin. You may have to do a little bending etc to get it perfect. I cut a piece of junk wire and fitted it, then matched it with the real float wire. Not planning on using the rubber gasket, just havn't done it yet. By the way, I have a flop tube in the left tank and therefore the sender is in the second bay. How did you all with this set up route and support the sender wire back to the fus bay?
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Fuel sender float wire - RE: - View Thread
Van's sends a little 8 1/2 x 11 drawing of the float arm and it says it's Full Scale. But, of course, it's not. Anyway there is no Z dimension on my drawing. But ow looking at the sender unit closely,yes, I can see that there's an additional bend required and then going back to looking at the drawing, I can see it indicates a 3/4 bend that looks to be 3/4 " from the 3 1/4" X dimension. Sure hope so, anyway; otherwise....new sender unit ordering time.
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Fuel sender float wire - RE: - View Thread
I'm assuming you bought a digital meter, if not let me know I'll help interpret the analog meter scale. On the meter you should find a selector that says "Ohms" or Resistance" or have the Omega alpha character, or a range that has the same. Set on Ohms and if the meter is not auto ranging select the closest MAX resistance value to what you want to measure, for example 200, 2000, 20K (20,000), 200K etc. For the sender select 2K (or 2000). By the way they could do it in 100, 1000 .... etc Put the leads in the meter in the Ohms and common sockets if not permanently attached and place the leads across the sender, one on the frame and one on the terminal. You will be reading resistance... no external power needed or wanted! For resistance readings lead color does not matter unless you are measuring across a diode. In that case, the reading will be very high with the leads in one position, very low if reversed. Piece of cake. They should have given you a booklet with the meter, but hope this helps.
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Fuel sender float wire - RE: - View Thread
Try bending the wire in a sharp clamp like two pieces of angle in a vice to get a good tight 90 deg bend. Some tapping with a hammer might sharpen the bend to get it to tuck into the sender better. Don't wack it while its in the sender, though. The multimeter should have its own internal power source. Set it to ohm and place one lead on the terminal post and the other to the mounting plate. Polarity will not matter for checking resistance but you can use the red on the terminal post. Unless you have a very expensive digital meter, you will only get a rough idea of the resistance values. But you should be able to tell if it is working properly.
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Fuel sender float wire - RE: - View Thread
I don't know what kind of multi meter you have but there is usually a selector that selects resistance, voltage and current measurments. On the ohms selection there is a scale such as X1 X100 X1000 X1M that is the ohms muliplier scale. The ohms is self battery powered for resistance readings. now the leads polarity doesn't matter ( unless there is a diode device in the circuit.... but I digress) if you are just measuring resistance such as the float resistance, so you can just place the probes on the two leads and whatever the meter needle reads on the scale you are on will be the resistance in ohms for instance, if the meter needle is on 50 and the scale is X100 the resistance is 50 X 100 ohms(5000 ohms). If the scale is X1 and the needle is all the way over to 0 that is a short ( 0 ohms ). if you are measuring from the center tap of the resistance to one side or the other you will see the needle swing as you move the float or potentiometer. I you are going to measure voltage then the red lead should be on the positive side (such as a battery), unless it is a digital meter then it won't matter (the display will show a minus sign if its reversed but the reading will be valid), and the dial selector should be on the voltage scale which uses the same X1 X100 etc as a scale factor times the reading.
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Fuel sender float wire - RE: - View Thread
The inexpensive multimeters that I have used usually have a rotating selector switch. Your owner's manual will probably have some explanation of the functions (and ranges) that the meter can handle and, if it's an analog meter with a deflecting needle, how to read the needle's position on the scales. To measure resistance, the meter will have an internal battery that will power it. Therefore, resistance is NOT measured on circuits that are hooked up to a power source (one way to fry a meter is check resistance on an energized AC circuit). Often the meter will have more than one set of receptacles for the leads to plug into - one set is for resistance and voltage readings, the other set(s) is for current measurement. Plug the probe leads into the resistance set (which may be identified either by an R (for resistance) or the Greek letter "omega" (which looks like a horseshoe or upside-down U) to indicate ohms (the unit of measurement for resistance). For resistance it doesn't matter which lead is used on which end of the circuit. With the selector switch set to the resistance range that needs to be measured [0-1, 0-10,0- 1000, (1000 is 1K ohms)], touching the two leads across what you want to measure will give a reading either by needle deflection (if the circuit resistance isn't infinite) or by digital value. Remember, there shouldn't be any voltage in what you are testing before you try to measure it - the meter's battery will supply a low DC voltage to measure the resistance to current flow. If this doesn't make any sense, call me and I'll try to walk you through an example if you have a cordless or cell phone to take with you while you use the meter. I appreciate your efforts as a moderator and will help where I can. As an engineer who has lost his job due to the disruptions in the protein markets caused by the one case of mad cow disease, I've got the time, but hopefully only for a short while.
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Fuel sender float wire - RE: - View Thread
I followed the dimensions for the float wire and they worked out OK. I just used Pro Seal on the sender with no gasket. I also put ProSeal on the screws. No leaks so far with the sytem full of fuel for over a month. I did use the cork gasket on the cover plate. I put Proseal on both sides of it and plenty of sealant on the screws. I also pro sealed the fuel tube and fittings.
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Fuel sender float wire - RE: - View Thread
Don't forget the Z dimension which is, if I remember correctly, about 1" bent at the end to insert into the center hole of the sender. That keeps it from rotating as opposed to swiveling. Clear as mud?
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Fuel senders - View Thread
Gang I am about to take the plunge and order the wing kit. Its time to make the decision on whether to order float or capacitive senders. I'm looking for the following info:
1) The main argument that I hear to buy capacitive is that there is "no moving parts" and so it should last longer. Has anyone actually had or heard of a float system failing? How many hours of flying did it take for it to go kaput?
2) Somehow I don't like the sound of electric current, however small, flowing through my fuel to measure the capacitance. From you guys that have built these systems, is this a valid concern? Is a short possible that can blow up your wing?
3) Finally, are the guys with the float systems happy? Are the fuel indicator needles in the cockpit fairly steady or do they wobble almost to the level of unreadable like almost every trainer I have flown?
Any other comments on the pros or cons of these systems?
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Fuel senders - RE: - View Thread
I did the float senders. So far so good. (52 hrs) The draw back is you can't monitor the first 5 gallons or so in each tank since the dihedral puts that fuel above the floats reach or arc. Once the first hour is flown off full tanks (or 1/2 hr off each) they start to register. I am using an EI dual dual gage. This gage has settings to vary the time to update the indicators so you don't get the wild swinging normal gages experience. It is pricey, but very nice. I was able to calibrate the tanks and use 32 gallons as the full setting (16 each). Once I reach the level that the senders start to sink as the level goes down. I have an accurate reading of my fuel level. I also calibrated the empty reading to have a 4 gallon reserve in each tank. I limit my flying to 3 hrs between fuel stops. That's plenty for this old gal's comfort level.
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Fuel senders - RE: - View Thread
This was recently discussed on the yahoo subaruaircraft list. If you plan to use any gas other than avgas, the capacitive system will not read out consistently. This applies especially to mogas since its capacitive properties change throughout the year for the seasonal blends. It my understanding that avgas's properties are fairly consistent through the seasons. Also, mixing avgas and mogas will result in quantity discrepancies if using capacitive.
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| The "cover your butt" section |
This website was built to document my work on my RV-9A in
compliance with the FAA requirements needed to certify my aircraft. My experiences and comments are by
no means to be considered as instructions on how to build an RV-9A or any other aircraft.
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