If I use straight synthetic will I damage the moving parts ?
Thanks, Brett & Randy
No, if it is enough by volume, BUT it will last longer with at least 1/4 of the oil castor
Randy
" Most fuels on the market today use a synthetic base and are blended for the R/C sport flier. These are typically very low on oil content, usually in the 12% through 15% range. This is never acceptable for our use in C/L Stunt. There are many reasons but the most important is the fact that we normally do not run our engines in a peaked two cycle, but rather a broad range of four cycle and rich two cycling. Any time you run with the motor set to come on and off in the maneuvers (like a typical 4-2 break) you are not only asking the fuel to lubricate the motor, it also has to cool the engine. The only way you can run in a 4-2 is to heat and cool the parts in the combustion chamber very rapidly. This makes the oil content critical, because it’s the unburned oil that helps carry away the heat.
Years ago, most fuels had only one oil ,castor. This is still a very good oil with many good but some bad points. Some of its good points; it carries heat out of the motor and gives a good plating action on all surfaces, especially when they’re hot. It also has tendencies to move toward hot surfaces, helping to protect them. A few of its bad points; it burns and sticks to the piston sides and the ring groove and all other parts that are hot enough, and will carbonize the chamber. It will stick rings in their grooves, freeze wrist pins and build up ridges on sleeves. This causes excess friction and heat and will ruin your motor in time.
The alternative to castor is synthetic oil and almost all fuels have these in them; the vast majority has all synthetic. Virtually all fuel manufactures use one type of synthetic; these are normally polyalkylene glycol based oils. They are mostly made up of alcohol started linear polymers , of oxypropylene groups. These are made by several companies and are available in a large range of molecular weights and viscosities.
This group of oils is the modern version of the old Ucon oils and also have good and bad points. Some of the goods points; they are very good lubes without containing any wax; they have outstanding load carrying capacity, film strength, anti-wear properties, are resistant to sludge formation, and will help keep your engine clean. The bad points are they give no rust protection by themselves, they don’t plate hot surfaces as well as castor and they burn at high heats.
As you can see, both oils have advantages and disadvantages to them; it’s for these reasons that they work much better blending together than they could ever work alone. Throughout many years of flying ,testing and other research have proven this to me beyond any doubt; plus you can see this for yourself. Recently, a friend of mine had a motor that would go into the pattern and lean out and act very inconsistently. The only change that was made was to substitute one tank of my fuel in the model. The results were drastically different; the motor now ran very smoothly, going into a two cycle instantly when the nose was raised and back into a four cycle instantly when the plane was leveled. This was tried back and forth both fuels; his and mine. The results were the same every time. I see this type of thing happen much too often, and it is extremely frustrating for Flyers to deal with. They often blame these fuel problems on cooling, cowlings, motors ,fuel filters, and unfortunately some don’t have a clue how to recognize or solve this problem. This is a frustration that you can live without!
I would like to tell you there is one Stunt fuel formula to run in all motors, I said I would like to tell you that…unfortunately this is not the case, and will never be as long as we have such a wide range of motors and running styles. What I will tell you is a good formula for the most common types of engines. Make sure you pick a fuel supplier who will give you consistent fuel day to day ,and will blend fuel for your motor needs or has fuel to match your needs. Stay away from any supplier who will not tell you the oil percentage, or who say one type works for all motors. I see this much to often also, It is unfortunate, but a lot of fuel manufactures will try to fool you about the oil and nitro percentage. One trick is to measure by weight and not volume. Doing so, they can claim that the fuel is for example 18 % oil , when in reality it is only 14.9 % oil content. Using weight for ingredient , they can put in a lot less oil and nitro . Other things are changing oil types, going to cheaper Nitro’s, and adding in other types of Nitro parrafins.
So what percentage do you try? For motors like Fox .35s, OS Max 35s or the old McCoy’s and K&B’s, use a fuel with 26 to 28% oil content; preferably half castor and half synthetic, up to 75% castor is OK. These motors have very small bearing surfaces, and are subject to much wear and heat, most are all plain bushing motors and most have unbushed rods. They need a lot of oil to help cool the engines. Since these motors run hot, they need extra oil to keep them lubed,clean, and to carry out heat . If you have one of these that is in very good shape but, is just starting to get some brown or black varnish plating on it, the synthetic mix will clean it up for you, resulting in increased life. Do not use the synthetic blend in an old motor that has a lot of time on it with all castor fuels; the synthetic will remove the castor varnish off the piston and sleeve and will in some cases, leave you with the worn-out motor that had to start with. Also always try to NOT use prop shaft extensions with these engine, as it adds a lot of wear on the crankshaft bearing.
For motors with larger bushings and bushed rods like to OS FP , Magnum GP series, Tower, and Brodak’s a 22-25% half-and-half oil mixture works the best. For S.T. .46 51,and .60s and most all ball bearings Stunt motors, a 23% half blend works best. Again the Synthetic blend will help keep the engine clean, and insure long life. If you use all castor in these types, it can stick the ring in the groove , resulting in poor compression and shortened engine life. If you have a ringed engine that castor has gummed up badly, most times running the synthetic blend will free the stuck ring, and the engine will return compression and power for you.
The tuned pipe motors like a little more synthetic and I recommend a 15% synthetic, 7% castor blend or a 20% half and half with 1 ounce of Aero-1 fuel supplement. Although many use 1\2 – 1\2 with great success. This works very well in the Precision Aero , OPS and Max VF engines, Super Tigre Thunder Tiger, AERO TIGER and most all of these type engines..
Four Strokes engines also like the blend, I have found that a 15 % synthetic – 3% castor blend works well for them, normal oil percentage is 18 to 20 %. This will vary some from engine to engine, but is a good starting point. Most like 10 to 20 % nitro, going up to 25% to 30% in the hot summer weather. Aero-1 Fuel additive can help 4 strokes tremendously, as these engines are lubricated mostly by “blow by” and can run very hot. Fuel and tanks are also very critical for 4 stroke operation. Make sure you have a tank that delivers fuel easily to the engine, as four strokes don’t seem to like having to pull fuel from the tank. Use as short a fuel tank as possible and keep it close to the engine. A lot of people use muffler pressure or pumps to help feed the 4 stroke engines. I have used OS VF pumps, Perry vibration pumps and Perry pressure pumps with my test on 4 strokes. I would suggest,as we do with 2 strokes, to use a Sullivan “Crap trap” fuel filter. They hold a lot of junk ,and have a very good double cone design, that pushes the debris away to the sides and almost never stop up. If you get a stopped up filter on a four stroke ( or 2 stroke for that matter) you can burn the engine up in one flight
When you use motors for the first time, you should also make sure you have the motor properly broken in. This will range from six tanks of fuel for one engine to almost two gallons for others. OS, for example, says two hours running time for their motors. A good break-in procedure is to use the same fuel as you will for your Stunt run ,and try to do your break-in on a bench; this is a lot better and an easier way to do a proper break-in. A diameter, one inch smaller than you plan to run at, at a 3 or 4 pitch, should be the prop to use. This will let the motor turn many revolutions more per motor run time. Start out in a very sloppy four-cycle for cast iron lapped piston and most ringed motors, slowly progressing to the fastest it will run in a four-cycle, then put it in a short two-cycle burst for short times. After the correct amount of time it should be able to run in a two-cycle without heating up and going leaner. Using 3 to 6 ounces per run with 5 to 10 minutes cool down time in between.
For ABC, AAC ,ABL, ABC-R and ABN motors, start out in a very fast four-cycle and about every 45 seconds; pinch the fuel tube to kick the motor into a momentary two-cycle. These types of engines normally take more break-in time than do their iron lapped piston cousins . If you can run the motor in a fast four-cycle and without touching the needle, pinch the tubing to lean the motor into a two-cycle for 20 seconds or so, then it should go right back to a four. After breaking in the engine with a few tanks of fuel , you can start using the needle to cycle back and forth from 2 to 4 cycle. When it is broke in you should be able to hold a 2 cycle for 30 seconds or so, and come back to a 4 quickly by turning the needle richer . If not, it probably needs more running time.
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Topic: Useing Castor in a Super Tiger .60 ?? Randy Smith (Read 2077 times)
