With the increased popularity of electric propulsion, glow fuel has become less widely available. \u00a0If you’re having trouble finding glow fuel maybe you want to mix your own. \u00a0The three ingredients are oil, nitromethane, and methanol, which is also known as methyl alcohol.\u00a0 Glow engines will run without\u00a0nitromethane, but with nitromethane in the fuel your engine will produce\u00a0slightly\u00a0more power, and the needle valve will have a wider range and will therefore be easier to adjust. \u00a0Most pilots like 5% to 15% nitro. \u00a05% is plenty for me. \u00a0Lots of guys stick with 0% just to save some money and keep it simple.<\/p>\n
If you’re going to mix your own fuel you’ll have to figure out how much and what kind of oil to use. \u00a0In the old days castor oil was the standard lubricant for glow engines. \u00a0Nowadays there are some high quality synthetic lubricants that are used in commercially available fuel. \u00a0Castor and synthetic have different lubricating properties and different thermal breakdown temperatures, but they both work well for the intended purposes. \u00a0Each type has a couple of pros and cons. \u00a0If your engine overheats from a lean run, when synthetic oil is burning up and evaporating, castor is still lubricating. \u00a0When castor oil finally reaches its critical temperature it turns to goo and slows the engine down, thus preventing damage. \u00a0Score one point for castor oil. \u00a0But the disadvantage is that an engine lubricated with castor oil will soon be covered with brown gunk, which isn’t pretty. \u00a0It’s sticky, it attracts debris, and if you leave it for a week or more the throttle and piston may get stuck. \u00a0If stored for a year, it will almost certainly get stuck. \u00a0An engine lubricated with synthetic will stay clean and pretty, so score a point for synthetic. \u00a0It should also be noted that it’s not difficult to clean up a castor-coated engine, and a stuck engine will generally come loose with a little bit of heat.\u00a0 Not only that, but when you put an engine away without cleaning it first, all that gummy castor residue will protect steel parts in the engine from rust.\u00a0 The engine run on synthetic and not cleaned for storage will most likely have internal rust when you take it out of storage a year later.<\/p>\n
The vast majority of commercial glow fuel in the USA has a mix of castor and synthetic.\u00a0 To determine\u00a0which type of oil\u00a0is best for your home made fuel you probably want to think about what kind of engines you are running. \u00a0An engine with a cast iron piston in a steel sleeve will benefit from castor oil in the fuel, and more oil overall. \u00a0This category includes Cox 049 engines and a lot of older engines made in the 1950s, \u00a01960s and 1970s. \u00a0There are some later engines as well with this metallurgy, including some from Enya, the early OS FP engines, and a few others. \u00a0When in doubt, stick a magnet on the side of the cylinder and it will tell you if there is iron in there. \u00a0When these engines were new the manufacturers tended to recommend 20% oil or thereabouts, and the recommendation was most often for castor oil, or at least a mix.<\/p>\n
Another factor that affects oil requirement is the type of crankshaft bearings in your engine. \u00a0Engines with bushings tend to do better with more oil, whereas those with ball bearings can get by with a bit less.<\/p>\n
If you have newer engines, or old innovative engines that set the modern standard, it is most common to run them on 17 or 18 per cent oil, usually synthetic or a castor\/synthetic blend. \u00a0Some people use as little as 14 or 15 per cent oil, but if you’re going to do this you need to be good at adjusting the needle valve so it never goes lean, and it’s a good idea to make sure that part of your oil is castor.<\/p>\n
If you decide that you want to use castor, you can buy small bottles of it from Sig, or you can buy large or small amounts of castor oil from a website called Bulk Apothecary. \u00a0If you want to use synthetic oil, there are quite a few good types and brands out there, but I do not consider myself an expert so I will refrain from naming oils that I have not personally used. \u00a0I will say that Klotz Super Techniplate has a blend of castor and synthetic and has served very well in my engines.<\/p>\n
Nitromethane can be found in small jugs online from various sources with various levels of shipping costs from reasonable to outrageous. \u00a0One good way to get hold of nitromethane is to buy the 5 gallon can of 50-50 mix of methanol and nitromethane from VP Fuels if you have a local VP dealer. \u00a0This is also a great place to get pure methanol. \u00a0Even if you don’t have a VP dealer nearby, if there is a drag strip or a hot rod fuel shop you can almost always buy methanol. \u00a0Just watch out for unknown “nitro” products. \u00a0Racing fuel shops have products labeled with the magic N word that are actually nitro-something-else. \u00a0You have to see the whole word, and then you know it’s actually nitromethane.<\/p>\n
It is customary to quote glow fuel components by volume, not weight. \u00a0A gallon (128 fluid ounces) of fuel with 20% castor oil and 10% nitromethane has 25.6 fluid ounces of oil, 12.8 fluid ounces of nitro, and 89.6 fluid ounces of methanol. \u00a0Note that these are not ounces by weight, they are fluid ounces. \u00a0The obvious way to mix a gallon of fuel is to pour each component into a measuring cup or cylinder with markings on the side, and pour them into a gallon jug. \u00a0But if you want a trick to make it easier in the future, measure one ingredient and pour it into the jug, then make a permanent mark on the jug using a sharp object to scratch the plastic, marking the level of this ingredient. \u00a0Then add another ingredient and mark the level, etc. \u00a0After the first batch you’ll never use (or wash) a measuring cup again. \u00a0If you’re making more than one gallon at a time, pour the finished gallon of fuel into a different jug and use the marked jug again to make another.<\/p>\n
The most accurate way to mix fuel is to use a scale. \u00a0Because fuel components are measured by volume, the volume has to be converted to weight by referring to the density of each component. I’ll save you some searching by sharing the information I found.\u00a0 These densities are stated in grams per milliliter.<\/p>\n
Let’s say you want to make a gallon of fuel just like the stuff you usually find at the hobby store, with 5% nitro and 18% oil. \u00a0The first thing you need to do is sit down at your computer and open\u00a0a google window. \u00a0Type “fluid ounce milliliter” into the window and a unit converter will pop up on your screen. \u00a05% \u00a0of a gallon is 6.4 fluid ounces. \u00a0(128 x .05 = 6.4) \u00a0On the google page, when I type 6.4 into the first box, the second box tells me that this is 189.271 ml. \u00a0At 1.14 grams per ml, this is 215.77 grams of nitromethane. \u00a0(189.271 x 1.14 = 215.77) \u00a0My scale measures to the nearest 5 grams, so I’ll just call it 215 grams.<\/p>\n
18% of a gallon is 23.04 fluid ounces of oil. \u00a0Going back to the google window, this is converted to 681.374 ml. \u00a0At .95 grams per milliliter, this becomes 647.3 grams of oil. \u00a0On my scale that’s 645 or 650, either of which is close enough.<\/p>\n
The remaining 77% of this gallon of fuel is methanol. \u00a0Multiplying 128 ounces by .77 yields 98.56 fluid ounces of methanol, which google tells me is\u00a02914.7671 ml. \u00a0Multiply that number by the density of methanol\u00a0(.79 g\/ml) and you get 2302.67 grams of methanol, or according to my\u00a0scale, 2300 grams.<\/p>\n
Figure out the formula for each fuel blend you want to make and record them in a computer file or on a piece of paper so you don’t have to do the math over and over.<\/p>\n
Now here’s the easy way to do the mixing. \u00a0You’ll need a scale, a small funnel, a rag, a paperclip, an empty fuel jug, and your fuel components. \u00a0Set the scale on a low bench or table at about waist level. \u00a0I am fortunate to have a huge restaurant sink, so I put the scale down in one of the basins. \u00a0Put a small rag on the scale and set your empty jug on it. \u00a0The rag will catch any accidental drips. \u00a0Straighten the paperclip and bend it to make a big V. \u00a0Hang the V on the top of the jug with one side in and one side out, then put the funnel on the jug. \u00a0The paperclip allows air to escape around the funnel instead of coming back up through the funnel and creating burps and bubbles. \u00a0Now turn the scale on and hit the Tare button so it says zero. \u00a0Pour oil into the funnel until the scale says 650 grams. \u00a0Here’s the best part: \u00a0You don’t have to wash the funnel because the weight is accounted for and it’s still in the funnel! \u00a0Hit the tare button to set the scale back to zero, and pour nitromethane into the funnel until the scale says 215 grams. \u00a0Zero the scale again and pour methanol into the funnel until the scale says 2300 grams. \u00a0Make sure you use the methanol to wash the previous ingredients from the funnel into the jug as you pour.\u00a0 Now you have a clean funnel and one gallon of glow fuel. \u00a0Put the cap on and give it a brisk shake to mix it.<\/p>\n
Now let’s assume that you’ve been to the swap meet and found a gallon of 20% nitro fuel for cheap. \u00a0You want to dilute it with methanol and oil to make three gallons of 6.67% nitro fuel. \u00a0Assuming that the original fuel has 18% oil again, and that you want 18% in your final product, you just need to split the fuel into three jugs and add the correct amount of methanol and oil. \u00a0First, put an empty jug and funnel on the scale and zero it. \u00a0Pour the entire gallon of fuel into the empty jug. \u00a0Now you know exactly how much the fuel weighs. \u00a0Divide by three and pour this much fuel into an empty jug, then again into the other empty jug. \u00a0Now each of the three jugs contains 1\/3 of the fuel. \u00a0You will be making 2\/3 of a gallon of 0% nitro fuel to add to each jug. \u00a02\/3 of 18% is 12%, so you can do the math to find out how much oil to put in the fuel. \u00a0Or you can go to the numbers quoted above for a full gallon and multiply by 2\/3. \u00a0In any case the final answer is 431.5 grams (rounded off to 430). \u00a0Because methanol is 82% of this fuel, and you’re making 2\/3 gallon, the total methanol content comes out to 1635 grams.\u00a0 Add 430 grams of oil and 1635 grams of methanol to each of the three jugs and you’ll end up with three gallons of 6.67% nitro glow fuel.<\/p>\n
It’s worth noting that if you want to do a little bit more math you can split your jug of 20% to make two gallons of 5% and one of 10%, or any other combination you want.<\/p>\n
If you start with the 50-50 mix of methanol and nitro from VP, use double the volume for whatever nitro percentage you want. If you want 10% nitro, then you’ll need 20% of a gallon of 50-50 mix, which is 25.6 fluid ounces. \u00a0Use the density data for 50-50 mix to find how many grams that is. \u00a0When it’s time to add the methanol, remember that you already put 12.8 ounces in when you added the 50-50 mix.<\/p>\n
Maybe your most economical option for obtaining nitro is to buy a gallon of really high nitro fuel at the hobby store, and dilute it with methanol and oil sourced elsewhere. \u00a0Or maybe you buy\u00a0a lot of weird fuel at swap meets. \u00a0I happen to have a gallon of 30% nitro Cool Power helicopter fuel, and two gallons of 15% Byron fuel that I got at the swap meet. \u00a0My plan\u00a0for this stuff is to dilute it with\u00a00% Omega, because I can get a good discount at the hobby store if I buy it by the case. \u00a0I also have my own methanol and oil. \u00a0The heli fuel has 23% oil, the Byron has 18% oil, and the Omega from the store will have 17%. \u00a0\u00a0\u00a0If I\u00a0mix the three jugs of swap meet fuel, eight gallons of 0% Omega, plus 116.5 ounces of methanol and 11.5 ounces of\u00a0oil, the final product will be\u00a012 gallons of fuel with 5% nitro and 17% oil.<\/p>\n
You may notice that I don’t care about the difference in the type of lubricants between one type of fuel and another. \u00a0The helicopter fuel from the swap meet is all synthetic, whereas Byron and Omega have a castor\/synthetic blend. \u00a0As a mild mannered sport flier I find that I get good performance no matter what kind of oil I use. \u00a0I want\u00a0at least some castor oil in the mix, but other than that I don’t worry about it. \u00a0If you are into pylon racing or 3D aerobatics, or if you have a tightly cowled engine, maybe you should be more concerned than I am.<\/p>\n
With just a little bit of arithmetic the possibilities are endless. \u00a0I apologize if this article is long and boring, but I thought I should go through all of the details for those who are math impaired.<\/p>\n","protected":false},"excerpt":{"rendered":"
With the increased popularity of electric propulsion, glow fuel has become less widely available. \u00a0If you’re having trouble finding glow fuel maybe you want to mix your own. \u00a0The three ingredients are oil, nitromethane, and methanol, which is also known … Continue reading