Glow plugs, hot or not.
For many of us Nitro fans, glow plugs are a mystery. They need to be lit to start the engine but after that we really don�t know anything about them, other than they work. As soon as we have problems with an engine that has run reliably for a few seasons we start fiddling with carb adjustments or fuel. Not to say they aren�t possible problem areas, but there is another possible problem you could have overlooked because you didn�t know how, or why it worked. It�s your glow plug.
How they work
Glow engines are often referred to as 2 stroke diesel model engines. This would be incorrect. Although they do not have a dedicated stand alone ignition system they do have a �chemical reaction� ignition. Where diesels work through compression, glow engines operate through a chemical interaction that causes the element to �glow�. That�s how glow engines got the name glow engines, easy enough. What happens is the element in your glow plug is coated with platinum, the platinum has a chemical reaction with the methanol which is what our �glow� fuels are based on. Without this chemical reaction our engines would not run.
Glow engine timing
I am asked from time to time if �glow� engines can have their timing adjusted. I always tell people, yes, that�s easy. Buy higher nitro fuel. Our glow engines have their compression ratios set by the manufacturer based on what fuel the manufacturer believes the prospective buyer will run. It�s not good to deviate from that to much unless you don�t mind buying a new engine soon. The compression, and fuel �nitro content�, work together to achieve the correct ignition timing. The basics idea is simple. Most European engines are higher static compression engines due to nitro being so expensive. They expect their consumers to run FAI or 5% nitro. Most engines destined for the US market have lower compression ratios because the manufacturer is expecting 5% to 15% nitro to be used. Higher nitro advances the timing as well as higher compression ratios. Run an OS max FP on 30% and you most likely won�t have it as long as you would running it on 10%. The reason is you have advanced the timing and the power output to a level above what the manufacturer intended.
Glow plug types
There are as many glow plugs out there as there are opinions. My old stand by for many years was always the K&B KB1L. It always worked so I used it in everything. Then came my first tuned pipe engine and suddenly my KB1L would only last about 3 flights and sign off. I learned my first lesson about glow plug heat ranges and application. Stick with what the manufacturer tells you and you should be fine. Once you start modifying engines and exhausts you will get a quick education on how well your airframe glides unless you are smarter than I was and install a cold enough plug to deal with the �hot set up� you have put together. There are other solutions like head shims but that�s a different discussion. Dead sticks will be common until you learn the lesson. Below I have some guidelines.
Enya #3 Hot, for sport flying and 4 strokes #4 slightly cooler for sport flying #5 Medium heat for stock sport engines with higher nitro. #6 cold plug for high nitro and tuned pipes
K&B KB1L hot for sport flying under about 20% nitro. KB7300 is for 25% nitro and higher. They also make an idle bar plug but I don�t care for it.
OS MAX F is long reach 4 stroke, A5 is a medium heat sport for .60 and up, #8 medium heat for general sport flying A3 is hot for engines up to .60
Rossi Rossi makes a line of plugs from R1 to R8. R1 being �very� hot and R8 being �very� cold. In my experience they are one of the best plugs on the market that money can buy, period. The R2 is the most common �sport� plug. The R4 is the cold plug that I use in piped engines.
There are many other plugs available but these I have experience with. Fox makes a plug that many people use and have luck with. I have no use for them and have never had luck with Fox plugs. I have replaced many fox plugs in peoples engines with KB1Ls just to hear people say � wow, my engine actually idles�.
For 4 stroke engines of any make I have always used OS Max plugs. Even in my YS engines I use the OS Max plugs. They work.
Glow plug life span
The life span of your glow plug varies greatly depending on how you treat it. Lean runs are the quickest way to burn the coating off of your plug and render it �glowless�. I hate it when someone tells me the reason their engine quit has nothing to do with the plug. They pull the plug and politely (not really) show me how it glows with a glow starter attached. I would like to say �Dah, it�s got 1.5 volts telling it to glow, how does it work in the engine Einstein????� But I haven�t ever said that yet. My point is just because it glows with a driver doesn�t mean its going to glow through chemical reaction in your engine. I have read that a plug treated well and not abused will last somewhere around 30 to 40 flights. I have to tell you I have more than that on some of mine but I don�t try to set lean needles either.
In the end
I guess I hoped to shed some light on an often mysterious part of our model engines. Don�t forget to check your glow plug if you have an idling or running problem and remember that just because your glow driver makes it glow that doesn�t mean its working in your engine the way it should. Try to stick with what the manufacturer of the engine tells you to run if your engine is stock and you are running the recommended fuel. If you are modifying your engine in any way take notes on what works and for how long. Remember that higher nitro and tuned pipes will most likely demand a cooler plug if you want the plug to last more than a few flights. I hope this was helpful.
Contributed by: Rusty Scott, Guildhall Fun Flyers 3/8/2007
Choosing a prop for your airplane the right way..
A propeller is nothing more than a thrust generating RPM governor for your engine. Don�t overcomplicate it. With the incredible selection of props we have available to us today there is no logical reason I can think of for not testing different engine / prop combinations. Remember it�s a hobby, have fun�����..
A. Tools needed.
I can�t stress enough to �tach� your engine. When your done, �tach� it again and enter the combination and results into your journal. Remember to note temp and fuel used. Higher temps or higher humidity will result in lower RPM settings and corrupt your test data. Cooler temps will raise your RPM as will lower humidity.
B. Flying style
You really need to know what type of flying you are going to do and what you are expecting from your airplane. Ask yourself, � What is the number one thing my airplane needs to do well?� No one propeller will give you speed while providing �3D� performance. A good rule of thumb is, Aerobatics demand low pitch blades with the greatest possible diameter. Speed demands high pitch blades with smaller diameters. Sport flying often is a compromise that lies between. Remember that both increasing the pitch and increasing the diameter lowers RPM. Decreasing pitch or decreasing diameter raises RPM.
Aerobatics 4 / 5 degrees of pitch Prop for the top of the RPM range
Sport flying 6 / 8 degrees of pitch Prop for the middle of the RPM range
Speed 9 / 14 degrees of pitch Prop just under peak RPM
Another factor that is harder to predict is blade width. Keep this one in the back of your mind. Wide blades lower RPM with more bite while narrow blades bite less and have a higher RPM value.
C. My experiences
D. Pitch experiences
1. 4 pitch gives instant throttle response, but cuts down on top speed.
2. 5 pitch gives excellent throttle response with better speed for sport flying
3. 6 pitch gives good all around throttle response with a slower build to peak rpm but has good sport flying speed
4. 7 pitch will tend to build in a dive to peak RPM and may sag a little on an upline. Good speed with thrust starting to suffer.
5. 8 pitch is usually not a good sport prop pitch for smaller nitro engines (.25 to 1.20 ) this is where the speed props start in my experience.
E. Diameter experiences
1. Diameter is thrust. Low pitch propped engines have their RPM limited with diameter when selecting a fun fly or aerobatic prop.
2. This is my favorite way to prop an engine. Low pitch / large diameter. I like throttle response, good vertical performance and the ability to have a strong prop wash over control surfaces at low air speeds.
3. Large diameter props have a beneficial braking effect during a downline maneuver.
4. Smaller prop diameters work better for speed. .45 DF engines have been run with 8 inch diameter props with 10+ pitch angles to obtain insane speeds in delta airframes. The small disc offers less resistance at speed while rpm is maintained with pitch. Remember pitch is forward speed.
F. Engine RPM
G. Tuned pipes
1. Don�t overlook fuel. The Fuel you use in a Nitro burner can have an impact on your set up. In extreme cases it can have a huge impact. Test with whatever it is you are going to run. A change from 5 to say 20 percent nitro will have an effect on engine RPM.
Contributed by: Rusty Scott, Guildhall Fun Flyers 2/26/2007
From May 2007 Issue of AMA Insider
(Nat AMA Newsletter)
Understand the charge of your batteries (NiMH and NiCad only).
Batteries are not complicated if they are explained easily. They are the most important piece of equipment in your aircrafts operating system to understand and maintain. I constantly hear confusing information and tons of techno babble about batteries. Here is the down and dirty of charging your batteries.
There are several rates you can use to charge your batteries. Different rates require different amounts of time to fill your batteries. I say fill because that is what you are doing filling a container for energy. There are max rates for given packs that shouldn�t be exceeded.
Capacity 10 � This is the rate you wouldn�t exceed for an overnight charge. This is Pack capacity divided by 10. The sum will give you the rate you can use but not exceed for overnight charging. Example: 1650 mah divided by 10 = 165 mah charge rate.
Capacity 3 - This is the rate you would use for a quick six hour charge. This is Pack capacity divided by 10. The sum will give you the rate you can use but not exceed for a 6 hour charge. Example: 1650 mah divided by 3 = 550 mah charge rate.
3C � This is the rate you would use for a Fast 15 minute charge. This is Pack capacity X 3. The sum will give you the rate you can use but not exceed for a 15 minute charge.
Example: 1650 mah X 3 = 4950 mah charge rate.
Note: fast charging is best done by specialized chargers that can detect a peaked pack and not overcharge them. I wouldn�t recommend manually fast charging an Rx or Tx pack. Try to use a �fast� charger for 15 minute charging.
Can I use my 50 mah wall charger to charge my 2200 mah Rx pack? The short answer is yes. The real answer is� not unless you want to charge your plane all week long to fly on Sunday, then do it again all next week!� This is not a very efficient way to charge your �big� packs.
I will do this with no mumbo jumbo or techno babble. Figuring the time is easy. Now that you know how to figure the MAX charge rates for your pack it is very easy to figure the time needed to peak it.
Learn it, know it, live it! The rule is Pack capacity X 1.4 = sum divided by Charge rate to come up with the time it takes to charge your pack.
Here is an example of a 1650 pack on a 50mah charger.
Question: How long will it take to charge?
Example: 1650 mah pack X 1.4 = 2310 ���2310 Divided by 50mah = 46.2 hrs
Answer: 46.2 hours to peak a 1650 pack on a 50 mah charger!
Knowing that 165 mah is the max you can overnight a 1650 pack lets do the math on that.
Example: 1650mah pack X 1.4 = 2310���2310 divided by 165 mah = 14 hrs
One last example is a 2400 mah pack on a 50 mah wall charger. This starts to get way to long in the tooth to be a viable charging method.
Example: 2400 mah pack X 1.4 = 3360��..3360 divided by 50 mah = 67.2 hrs *
The Rules, follow them!
I hope this makes a confusing subject easier for people to understand and helps them maintain their batteries better. If anyone has questions it�s always better to ask then to guess. If you are new to the hobby or just don�t know because you didn�t need to, no question is a dumb question������