COOLING SPINOFFThis is a "spinoff" from the Russel/Bruce "Controller Temps ....." thread. As it drifted away from just the ESC temps into cooling in general, it seemed to warrant its own broader "system wide" cooling thread. I feel this is an important issue that is greatly misunderstood by new ECL builders/converters. I hope this new thread answers some of the many cooling questions raised by new ECL pilots. With luck, we will have photos of good E cooling systems from the many talented and experienced E builders/flyer's on this forum.
GOOD NEWSThe good news is that there are many good solutions out there and it won't take too long to get this information disseminated among all ECL modelers. We also have thousands of successful E designs from the ERC world that can help give us some guidance. The other bit of good news is that it seems that our E systems are pretty tough. I have seen many good E installs, but I have also seen some amazingly poor installs with everything just thrown into a small space with little air circulation. The poor systems worked. Yes they got a little hot but they still flew great patterns. They will not last as long, and they are probably not running at MAX power and efficiency, but they still work OK. So, our goal is not to scare people or make them think that they have to have a "perfect" install to get into ECL.
You don't have to use the suggestions listed below to have a successful "OK" ECL system. My only goal is to show that with a very small amount of effort and some knowledge about cooling systems we can all have COOL systems that are efficient, powerful, and long lasting.
OUR COOLING GOAL: SAFE OPERATING TEMPERATURES:After talking with experts (Dean, Kim, etc.) and manufactures, here are the Temperature ranges we should be aiming for:
MOTOR: MIN = Zero degrees Calvin, as cold as possible ........ MAX = < 130 f (over 150 f = trouble!)
ESC: MIN = 33 f ......... MAX = < 130 f (over 140 f = trouble)
BATTERY: MIN = 70 f ......... MAX = < 130 f ( our batteries like it best between 90 f and 115 f ) when cold WX flying, reduce cooling to keep them warm.
BTW: An easy measuring device is the fingers on our NON flying hand. Humans can hold something up to around 125 f before it feels to hot to be comfortable. You should be able to painlessly touch your ESC, your MOTOR, and your BATTERY. If you can't, then you are pushing their limits, and more cooling may be needed.
OUR CL PLANES ARE DESIGNED FOR WET ENGINE COOLING, "NOT" ECL COOLINGOne of our biggest problems is that traditional CL designs have only one cooling inlet that is for the single cylinder wet engine in the inverted position, with an air outlet in the bottom of the plane aft of the cylinder. And they almost always use a large spinner above this inlet. When converting our CL planes for ECL we can quickly see that we need some changes to cool our three major parts, not just the one in front.
1. We need to horizontally SPLIT the air coming into the lower front intake with some simple baffles. The top 50% needs to be directed UP to the motor intake holes and the bottom 50% needs to be directed toward the ESC which is usually located below the battery near the bottom of the plane. The ideal is to have "unheated" air going to the ESC, NOT leftover "heated" air from the motor. ......... This is one of the main reasons for ESC overheating, the ESC deserves its OWN cool air.
2. Ideally we need a top, or side intake that brings the air into the battery area aft of the motor area. If at all possible, like the ESC, the battery deserves its own air, not hot leftovers.
3. With a little imagination and a look at WW II aircraft intakes, we should be able to make some nice looking intakes on our ECL conversions. A big help is that we are always going over 50 mph and it does not take a large intake to bring in a lot of cooling air. ........ About 1.5 sq. in. total front intake(s) should be enough if we have some simple baffles inside and adequate air exhaust exits.
4. Just think of the airflow inside your plane. Air, like water, will ALWAYS take the easiest way from INLET to EXIT. We need to make sure that the air flow is directed into the motor and not allowed to escape bypassing it. The same for the ESC. Don't let the air ignore the ESC on it's way toward the exit. Same for the battery. Your baffles don't have to be fancy, just light and effective. They can be thin balsa, or carved pieces of foam to force the air to go where it will do our system the most good.
AIRFLOW OUTLETS Another common mistake is making it difficult for the hot air to exit freely. This lets heat build up inside the plane and defeats the effectiveness of the cool inlets we made in the steps above.
1. The general rule of thumb for wet (a LOT of heat) systems is the Exit area needs to be at least 2 times the size of the inlet. We don't get that hot so our air does not expand that much, but we still must make sure that our exit is larger. The 2 to 1 won't hurt but 1.5 to 1 is a good target. If in doubt, error on the LARGE size.
2. Try to have multiple exits. At least try to have the hot motor air exit on it's own, and NOT just direct it over the Battery and ESC on it's way to a single exit. These motor air exits can be holes in the side of the motor area, or out the bottom of the motor area.
3. If you have only one large main air exit on the bottom of the plane then you should try to have baffles separating the hot motor air so that it has its own sealed routing to the rear exit hole area. The same for the ESC and Battery.
4. The battery can have the air enter the front then exit straight down to the rear bottom exit, or out the rear top if there are baffles inside to make sure the the air is forced to flow around the battery on its way toward the exit.
5. If you look at many full scale piston aircraft you will see that almost all of them have adjustable cowl flaps. These flaps at the leading edge of the air exit hole cause a low pressure area to be created at the exit hole that SUCKS the air out of the plane which causes an increase in the volume of air flowing over our E system. I think this will be a BIG help to all of our ECL planes. It will help in our cooling and if it is adjustable it will allow us to control our temps inside as outside temps change.
THE FUTURE OF ECL COOLING1. Within the next few years we will see more CL designs that are created for the use of E power. This will allow us to have a built in cooling system that is integrated with the power system from the beginning of the design. Phil Granderson's beautiful purpose built E ship is a good example of this. So is Kim's FAI E powered ship. Paul Walker's latest design, and Will Moore's beautiful round motor design also shows us what can be done when you start with a clean piece of paper for E powered planes.
2. In ERC most of the aerobatic E planes are scale models of full size aerobatic planes that have LARGE front cooling intakes on both sides of the spinner, plus another intake below the spinner. This is perfect for our ECL planes because we can direct each inlet toward each of our three components.
3. Round motor cowled designs (Yak, Sukhoi, etc.) are perfect for ECL. We will see more of these in the near future.
4. Our very narrow, small fuselage CL designs reflect the need to minimize drag back when our wet engines were VERY weak and they could not pull much drag up hill. Being from the late 1940s and early 1950s, they also reflect the influence of WW II fighters, and the air races of the 1930s and late 1940s. Today we have UNLIMITED power with our E systems (and modern wet systems like Randy's Piped PA engines). We can pull any fuselage size or shape up hill. So we can design planes that look like full scale, and are E friendly.
I hope this little post encourages others to send in their photos of their cooling designs/installs and also their ideas on cooling solutions.
Warm Regards,
Topic: Cooling our Complete System (Read 1980 times)