- Joined
- Dec 17, 2017
- Messages
- 104
- Reaction score
- 61
I always thought to calibrate and mark my header tank fuel level rod. My float was sinking so I got a new Ercoupe float from Uni-vair (2" x 1.25"), Got a .125" 7075-T6 rod from Alexandria Precision, warmed up the end of the rod and mushroomed it a little, drilled out the center of the float to .125", drilled a small shallow recess in the float to receive the mushroomed rod end, coated the mushroomed end of the rod with catalyzed Vinyl Ester Resin (boat resin which is temperature and chemically very stable), inserted the rod all the way in until the mushroomed end received into the recess in the float then filled the small recess with resin.
I now have a float that won't sink with a lighter more resilient fuel indicator rod (7075-t6 is extremely resilient, the original mild steel rod bent easily). The float is 90% of the displacement of the original cork float but the Aluminum rod is only 50% of the mass so the new combo floats very lightly in the gas. The original steel rod was .109" diameter so i drilled out the brass guide in the center of the gas cap to .150" to receive the .125" 7075-t6 rod. I spent some time with the drill bit and heavy cutting compound, used for polishing car paint, to polish the brass guide tube and lend it a slight flair at the ends for better slide action of the rod.
Now tell me there are no other Electrical Engineers or hobbyists out there who hasn't been flying along in their Cub and thought to themselves, "Self, it sure would be nice to calibrate and mark the fuel rod to know how many gallons are left in the tank. Can't put numbers on it because they won't be seen, hmmm... I know! I will use the resistor color code to represent numbers and paint color bands on the rod corresponding to the # of gallons left!
Putting the tail wheel up on a 55 gallon drum to hold the airplane essentially level (I always hanger the Cub that way so I don't have to duck all the time to get around in the hanger), I drained the tank through the gascolator then drained the tank sump to discover my tank has .4 gallons of not usable fuel. I poured the .4 gallons back in the tank then proceeded to pour one gallon at a time back in and measured what height the rod was until I had put 11.25 gallons in and the tank was full. Buy the way, I think the bottom of my tank is pushed up which would account for the .4 gallons unusable and the less than 12 gallons total.
I then scuffed up the rod with the coarsest, sharpest, ScotchBrite pad I had (new green pad), marked the gallon stations according to my measurements (exactly 1.125" spacing by the way), and painted the rod with those tiny jars of Testors Hot Fuel Proof Paint from the hobby shop according to the resistor color convention:
0-9 = Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White. To remember the order of colors, there is a politically incorrect mnemonic that can be found on the Web that, once you hear it, you will never forget it. Anywho, I will lightly scuff the enamel paint once fully dry then coat the whole thing with catalyzed urethane clear (Deltron) for abrasion resistance, insert it into the gas cap then heat the tip (very hard to bend it cleanly otherwise) and bend it 90 degrees like the original. I am thinking of coating the painted rod with Conversion Varnish (catalyzed lacquer). It is used to coat table tops and furniture and I have found it to be the toughest, hardest, most impervious to chemicals, coating that I have ever found. I will have to lookup its specs for fuel resistance first though.
This Float/Rod combo is very buoyant and will measure down to that last quart of fuel. It also slides very nicely so there should not be those times when you are flying along and the fuel rod suddenly drops 2".
It used to be with the original float rod that when the rod had completely stopped floating and was firmly hanging on its hook, then I was at minimum fuel which is 2 gallons left which equals the required minimum of 1/2 hour of fuel. A person would want to plan on landing when that rod was hanging by the hook. I am going to have to relearn using my new fuel rod now...
I now have a float that won't sink with a lighter more resilient fuel indicator rod (7075-t6 is extremely resilient, the original mild steel rod bent easily). The float is 90% of the displacement of the original cork float but the Aluminum rod is only 50% of the mass so the new combo floats very lightly in the gas. The original steel rod was .109" diameter so i drilled out the brass guide in the center of the gas cap to .150" to receive the .125" 7075-t6 rod. I spent some time with the drill bit and heavy cutting compound, used for polishing car paint, to polish the brass guide tube and lend it a slight flair at the ends for better slide action of the rod.
Now tell me there are no other Electrical Engineers or hobbyists out there who hasn't been flying along in their Cub and thought to themselves, "Self, it sure would be nice to calibrate and mark the fuel rod to know how many gallons are left in the tank. Can't put numbers on it because they won't be seen, hmmm... I know! I will use the resistor color code to represent numbers and paint color bands on the rod corresponding to the # of gallons left!
Putting the tail wheel up on a 55 gallon drum to hold the airplane essentially level (I always hanger the Cub that way so I don't have to duck all the time to get around in the hanger), I drained the tank through the gascolator then drained the tank sump to discover my tank has .4 gallons of not usable fuel. I poured the .4 gallons back in the tank then proceeded to pour one gallon at a time back in and measured what height the rod was until I had put 11.25 gallons in and the tank was full. Buy the way, I think the bottom of my tank is pushed up which would account for the .4 gallons unusable and the less than 12 gallons total.
I then scuffed up the rod with the coarsest, sharpest, ScotchBrite pad I had (new green pad), marked the gallon stations according to my measurements (exactly 1.125" spacing by the way), and painted the rod with those tiny jars of Testors Hot Fuel Proof Paint from the hobby shop according to the resistor color convention:
0-9 = Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White. To remember the order of colors, there is a politically incorrect mnemonic that can be found on the Web that, once you hear it, you will never forget it. Anywho, I will lightly scuff the enamel paint once fully dry then coat the whole thing with catalyzed urethane clear (Deltron) for abrasion resistance, insert it into the gas cap then heat the tip (very hard to bend it cleanly otherwise) and bend it 90 degrees like the original. I am thinking of coating the painted rod with Conversion Varnish (catalyzed lacquer). It is used to coat table tops and furniture and I have found it to be the toughest, hardest, most impervious to chemicals, coating that I have ever found. I will have to lookup its specs for fuel resistance first though.
This Float/Rod combo is very buoyant and will measure down to that last quart of fuel. It also slides very nicely so there should not be those times when you are flying along and the fuel rod suddenly drops 2".
It used to be with the original float rod that when the rod had completely stopped floating and was firmly hanging on its hook, then I was at minimum fuel which is 2 gallons left which equals the required minimum of 1/2 hour of fuel. A person would want to plan on landing when that rod was hanging by the hook. I am going to have to relearn using my new fuel rod now...
