powerchute50

Hello to the forum. I have spent some time reading through the FAQ posts and the general and glow to electric conversion forums. It has been valuable because after thinking seriously about getting into electric RC, I am now convinced that I am staying with gas and glow. Electric is still trying to sort itself out, and it has a long way to go.

Manufacturers seem to be bringing out different motors almost daily, but do not post any information about them in their ads. Motor designations seem to have nothing to do with the capacity of the motor. In designing a power system for a new scratch built airplane, or converting an existing glow model, where do you go to get the technical information you need? The manufacturers web sites that I have visited are confusing and do not offer any way to judge the performance of their motors. Its only amps and volts (which make watts) so why the confusion? I should be able to look up the recommended voltage and amperage range for any motor. Then I could size my battery pack and ESC. Where is this information and why isn't it stamped on the motor and listed in the ads? All electric devices have a fail point in terms of voltage and power draw. This is not voodoo, it is just simple design. Stamp the ratings on the can, why all the mystery?

Can you imagine building an electronic circuit if the voltage and watt rating was not available for your resistors and other components? This is nonsense. Electric has got to get some language worked out so us gas modellers can come in too. It is far too loose and variable at present. It is hard to even begin describing electric propulsion systems to beginners because there is no rock to stand on in assessing power and suitablity for a given model. This is the fault of the manufacturers in my opinion.

Gas and glow forever, or at least until I can read an electric motor ad and think "hmmm, that would be just right for my 1/2 A Cox Fan Trainer". At present I read the ads and can only think Huhhh? What the heck are they talking about. Try wading through a Hacker ad and see what you can get out of it. Maybe the model designations should actually mean something. Or should Saito start calling their products XD-45p-297 instead of a .82 four stroke engine?

pmmartin

I have been into flying electric models for quite some time. These are all the questions that I have had for years. I think until these issues are addressed there are going to remain a limited number of modelers willing to tackle the challenge. I believe it is the reason many folks have only had limited success.

It is a lot of money to spend and then not being sure it will really work. I think the manufactures should take note to your post and make some changes. It certainly is almost impossible for the average modeler to figure out what they may need. Some of the vendors are knowledgeable and will help you but some may be way off as well.

smokingcrater

it really isn't that hard at all if you take the numbers and a decent program like motocalc. watts are the key term, and you rate motors with k/v...

StephenT

Guys



Come on! Life is a challenge! Step up!

woodduck-RCU

I disagree that electric flight is in its infancy, it has matured at a phenomanal rate in the past 2 years. Better products, selections, products like Motocalc to help with answers. I have almost totally switched from 10 years of glow to all electric. The intial investment may be higher but some of the motors will never wear out and can be moved from plane to plane. We have to use some basic skills when picking components such as servos, motors, batteries, weight is a major consideration. With glow power if in doubt just overpower it, if it calls for a .25 to .32 use a .36. I have been converting my glow planes to electric power switching form .15 thru .46 to AXI outrunner motors, as much or more power, no mess, no noise. MY last palne to convert is a High speed Diamond Dust with an OS 32 SX and tuned pipe.
One major advantage for me is the ability to fly almost everday at lunch, time just did not permit flyng glow planes. I can have my plane and a couple of spare battery packs ready, take it out of the trunk and fly.

Wood Duck

pmmartin

I agree that electric models are wonderful and after 50 years of IC engines, starting with control line, before radio existed I have now switched to totally electric with all my planes at least 40 size. I have planes up to 1/4 scale and they are all conversions prior to my most recent model witch is a Venture 60 E.

I do love the electric models, the cleanliness and convenience can't be beat.

I still will very much agree with the original post here. It is difficult and confusing for someone to get started. There is a lot to learn and I don't think anyone can deny that. What everyone has said in reply is correct but why can't it be made a little easier for someone to get started. Look at the Maxx Products add and think about a beginner trying to pick a Himax motor for a plane with the information that is there. I think you will agree that some of this is very difficult for someone with no experience with electrics.

Paul

powerchute50

Okay, you have some experience growing in electrics that would be useful to people like me. When I see a review of an electric model in the magazines and they state that they are using an AXI 4120/14 motor and Jazz 12-7-16 ESC, my first question is....why?

What are the characteristics of that motor that make it appropriate for that model? How do you decide? What are you using for information in converting over your glow models? How are you deciding on the motor that best replaces the glow engine in your model?

This is the kind of information that I am having no luck finding. There does not seem to be much in the way of a guide to electric motor performance. I realize that part of the problem is the fact that a given motor can run at different voltages and amp ratings. Nonetheless a DC electric motor does have a maximum voltage rating and amp draw based on the number of windings and guage of wire on the coils. It also has an optimum rating based on the design of the motor. What are those ratings and where do you find them?

What is the optimum voltage and maximum amp draw for that AXI 4120/14 motor? How about a Himax HA3618? Or a Hacker E3-49? Until I know this, how am I going to assess the power system I need for the 72" scratch built Stinson float plane taking shape on my work bench? The maufacturers know what motor to put in the Fox Bat, or the foam Mig ducted fan, or the 60 " Mustang. Why can't they share that information with us?

That's why I think that electrics are still too young to invest money in. The manufacturers are going to have to find some standards of comparison, and a common language to describe their products. How else is a gas modeller supposed to make sense of it all?

pmmartin

Everyone doesn't seem to agree with me but I think you are very right with your assesment of getting started. I have been saying the same thing and have brought the issue up to some of the manufactures. It is like once someone knows it becomes easy and then they forget about someone starting out. I almost think there are those that look at it like an initiation into the electric club and don't want others to know. They think it must be done the hard way like they did it. This however doesn't promote the use of the technology. We should try to make it as easy as possble for each other.

I will try to answer some of your specific questions as soon as I have a few minutes to do an adequate job on it. I hope maybe I will have some time tomorrow to get back to this.

Paul

StephenT

guys



Reading these foums, talking to guys at the FF and LHS is how you learned about glow. It is the same with E-Flight.

When I started flying it was with E-flight, then I had to learn glow because my son wanted it.

mvigod

It isn't easy. As a long time glow guy of decades I decided to dip my feet into electrics. Even after a few models I still don't feel they are as simple to figure out as glow models are. Basically though I decide on what I want to fly and then based on the plane, its weight and flight time requirements go from there. How do I start? Well for me I come to our electric forums and see what guys are using in the same plane and if no matches in the search I just ask. Give the specific details of your aircraft and lots of knowledgeable guys here will narrow the field of motors and esc's. Once you have the motor picked you can figure out what packs and voltage/amps you need to crank the necessary power out. You can use motocalc or ask in here and somebody can help you out.

The part where it starts to get easy is that generally most planes in each range will have a set of motors that work in them. After you follow it awhile you know a short list of what might work. Electric motors have the ability to put out a wide range of power depending on the volts you crank through them and the prop. This tends to be a wide variable.

One thing that may help is something george hicks told me. a motor will turn a certain rpm at a certain voltage. this is the kv rating. so the interesting thing is that if you apply say 10 volts to a motor with NO prop it will turn at "x" rpm. If you put a 5", 10" or 15" prop on that same motor and apply the same 10 volts it will turn the SAME "x" rpm! The difference will be that the bigger props will draw more AMPS to get to that rpm. Once he explained that for some reason it all made a little more sense to me.

I won't be leaving glow anytime soon. Electrics are fun and I enjoy them. I will fly both glow/gas/electric this year. For me they are all good.

woodduck-RCU

I would agree somewhat, there is no unformity of info between manufactures and you may have to serach a bit. But here is a good example.

I want to convert a Hangar 9 Aresti with an OS 46 AX to electric, I go to the Hobby-Lobby webpage and click on brushless motors.
I look at the various weight of plane these motors will fly, then pick AXI or ACTRO
I select AXI http://www.hobby-lobby.com/brushless_axi.htm

I scroll thru the list until I find one in the .40 size list

http://www.hobby-lobby.com/brushless-axi2826.htm

I get the weight info, prop size and batteries required , also the amp capacity of the speed control.

Matt Kirsch

My Feedback: (21)

You won't believe me, but I'll tell you all precisely why you have such a tough time understanding electrics. It's all this talk about, "motor motor motor motor motor motor." I'm here to tell you that the motor is the LEAST IMPORTANT piece of the puzzle. You're concentrating too much on the motor, and ignoring what's really important.

Electrics will be more complicated, because you have more components to deal with; you're basically building an engine from its component parts. Plus, you have to seriously take weight into consideration. With glow, you just shoehorn the biggest engine into the nose of the plane. Electrics take a little more finesse, but it's not something that's beyond the grasp of the average modeler, even without the expensive tools like Motocalc, or a Whattmeter. You don't need to know a thing about Kv, Io, or any other motor constant. Volts, Amps, Watts, and a couple of simple rules of thumb are all you need to be successful.

You just have to change your frame of mind. If you don't want to, then maybe electrics aren't for you. They aren't for everybody, just like glow isn't for everybody, just like powered flight isn't for everybody, just like radio controlled flight isn't for everybody, just like flight itself isn't for everybody. Nobody's forcing anybody to do anything, despite what you think.

With electrics, you tell the plane how much power it's going to have. It's not determined by what you bolt to the nose. You determine how much power the plane gets, break it out into a battery, then, AND ONLY THEN, do you consider a motor. Nearly all motors are rated in terms of Volts (or cell count) and Amps. If you find a brand that isn't, then you simply don't consider that brand.

samolot

My Feedback: (14)

Well, in my case, Electrics are the way to go. I live in NYC, and there is no room in apartments to set up a hangar and start building from scratch. Neighbors complain about the noice, and its just plain frustrating having to work during the day, not the night, which is when i love to just sit down and spend a couple hours on a model. Electrics are much smaller so storage is great. And by the way, hobby-lobby has a great selection of electrics. I beleive towerhobbies is for glow guys and hobby-lobby is for electrics. Electrics are also much cheeper and come built with sturdy foam. This would be my conclusion:

If your starting, go electric, cause if you crash a glow, you just wasted like 300$. If you crash an electric, epoxy, and your flying again.

Now coming back to your question, i agree that it is quite young. Electrics i believe just werent meant to be scratch builders. Give it some time, more powerfull engines will come and more and more planes will have all-wood constructions, (right now there is onl one, the Hobbico Superstar EP, but it is severly underpowered). Its all a matter of powerfull electric engines. Right now, Glow is the way to go, if your scratch building. Trust me sooner or later we will have electrics everywhere with solar panels on the wing to charge the battery while your flying, and glow will become an old-time tradition.

mikefev

Another valuable asset in electric flight along with a WHatt Meter is a scale of some sort to weigh your model with all the components. I recently converted a Great Plains Big Stik ARF to electric. Here are the stats:

Weight with all components including 10 cell NIMH battery, 5.12 lbs
Motor is an Electrifly 600 with a gearbox that comes with a 30 amp ESC purchased from Tower.
I used standard servo's and attached the motor to the supplied glow engine mount.
I have tested it with a 12 X 6 electric prop.

Following are readings recorded using a Whaat Meter and a Digital Tach

8800 RPM drawing 263 Whatts at full throttle using a 10 cell NiMH battery.

Based on my limited knowledge it should fly but will not be aerobatic. Somewhere I read a thread that the following requirements were needed to determine feasability of electric flight.
50 Whaats per pound = will fly the model
60 to 75 whaats per pound = mild aerobatics
100 + whaats per pound = 3D flight

My long term plan is to eventually power the STIK with an AXI 2826/10 or 12 motor powered by Lithium Poly batteries

Always remember, GO LIGHT!!!!!

VR Mike

pmmartin

To All:

Here is some pretty good information from Aveox. It makes things a little easier and from my experience this is right on the mark. This works for all electric motors not just Aveox!
Paul

http://www.aveox.com/rc/rules.html

Engine to Cell conversion
Engines
Batteries

0.15 Glo
7 – 8 Cell

0.25 Glo
10 – 14 Cell

0.40 Glo
16 – 20 Cell

0.60 -.90 Glo
24 – 28 Cell

Number of Cells/sq-in wing span
High Wing Trainer
1 Cell/50 sq-in

Aerobatic
1 cell/35 sq-in

Power by WeightHigh Wing Trainer
50 Watts/1 Lb

Mildly Aerobatic
70 Watts/1 Lb

Severe Aerobatic
100 Watts/1Lb

Greg Covey

I like the models that you can just pull out of the box and give a toss.

powerchute50

I don't understand the emphasis on batterys in the estimation of the motor you will need for a given model. The Aveox info says 16-20 cells for a .40 model. So that is 24 volts for 20 cells. If I use 2300 mah batteries and aim for a 5 minute flight time, what will that battery pack give me? 2.3 amps for one hour, 4.6 for 30 minutes, 9.2 for 15 minutes, 18.4 for 7.5 minutes, or 36.8 amps for 3.75 minutes. So say I settle for 30 amps to get closer to 5 minutes. I want to search the manufacturer web sites for a 24 volt motor that will draw no more than 30 amps constant power.

So what? How does this tell me what I want to know about my model performance? I know what the model will draw for power, and how long the battery pack will last, but I have no idea whether my model will even fly with that motor and battery combination.

It makes more sense to aim for the performance you want in your model. If I want my scale Super Cub to fly at 50 mph using a 6 inch pitch prop, my motor rpm for that pitch speed will have to be 10,000 rpm. If I want to use a 12 inch prop, I will have to determine what the power draw will be for than performance. I may not be able to get 10,000 rpm from my electric motor, so I will pitch the prop up to 8 inchs and suffer a higher amp draw from the motor. I may want a 14 inch prop for floats. What will that draw on the motor? Which motor will I choose for each application? How does model weight affect motor performance?

It makes more sense to size your battery pack to supply the motor that will give you the model performance you want, not the other way around. But picking this motor/battery combination requires some technical information on the various motors that a manufacturer sells, and this info is sadly lacking at present.

I think that this is the reason most electric ARFs and RTFs come with the motor. You supply the battery and flight pack. The manufacturer has sized the combination for that particular model. This will probably be the pattern for the future, but it leaves us kit and scratch builders out in the cold.

pmmartin

Most of the ARF's that I have seen and had experience with that come with motors are badly underpowered. My conversions are all well powered and they pretty much follow the Aveox rule of thumb. Look at the power tool industry. The more volts the more power. It is actually watts the tells the story which is the result of volts and amps.

I think you need to study ElectriCalc http://www.slkelectronics.com/ecalc/index.htm . This I think should help in learning and making the kind of decisions that you wish to make.

Paul

Matt Kirsch

My Feedback: (21)

Tell me, why is it that I can easily, successfully convert ANY plane to electric by starting with the battery, while those who start with the motor do nothing but scratch their heads and complain about electrics being immature and too complicated? Hmm? Doesn't that tell you something? Perhaps you're taking the wrong approach...


powerchute50, the emphasis is placed on the batteries because that's where the POWER comes from. It takes X amount of power to turn Y prop at Z RPM, no matter what motor you choose. That's physics at work.

Now, let's go with your example: 20 cells, 30 Amps. You go out and pick a motor that's rated to handle AT LEAST 20 cells and AT LEAST 30 Amps, not a motor that draws 30 Amps on 20 cells. It does not matter what motor you pick, as long as it can handle the power. Its output can always be fine-tuned to match the plane through propeller and gearing.

When was the last time you said, "I want my scale Super Cub to fly at 50MPH on a 6 pitch prop," with a glow powered plane? Never. Why is it suddenly an issue with electric? It isn't. You're making it more complicated than it really needs to be.

Why would you run a 6" pitch prop at 10000 RPM when you can run a larger-diameter 9" pitch prop at 6666 RPM for the same speed and get more thrust (better acceleration) more efficiently? Glow engines are limited to smaller diameter props due to the limited amount of torque the can produce, and gearboxes are not practical due to the vibration. Just like in full scale, you want to spin the largest propeller that's practical for the plane, gearing if necessary, to take full advantage of the available power.

Remember, these are all just basic concepts to keep in mind, rules of thumb. You don't have to be a whiz with math or have all these fancy analytical tools. There is enough data out there now to make an informed decision.

pmmartin

Matt Kirsch:

Very well said. This is turning out to be a very good thread with a lot of useful information! It is nice that most contributors are trying to be helpful rather than critical. Congratulations folks for the assistance that you are contributing to the initial issue. That is what makes these forums so useful.

Paul

stefanP

My Feedback: (2)

Matt very well said.When deside to build a plane I look at the over all project first.Try to get in my head a feel for the plane.Well take for instance a warbird or a highly aerobatic plane. A plane of this caliber will need to be near 1to1 power/weight ratio or better to fly they way you'd expect it to. (my opinion here) I think lots of people want e-power to be like fuel.Just get a big enough motor and it will fly.Not taking consideration; wing load,speed of flight,flight times,battery weight.Now I'm not as technical as pmmartin or Matt but I read a lot of articals and use a few simple tools that have made my E flying very rewarding; Calulator, Voltsx Amps=watts rule,Asto Flght Watt meter,and a Fishing scale from WalMart Also use another rule of thumb,During static thrust test the plane must pull AT LEAST 1/3 of the R.T.F. WIEGHT inorder to fly at all.People in my club are always amazed that my planes fly so good.I tell them I do my HOMEWORK FIRST!! then go to the feild with with confidence that the plane will fly and now it's up to me to be able to fly the plane. Anyhow thats my 2cent's I hope this may help,

stefanP

Greg Covey

In addition to RTF packages (that are not underpowered these days Paul!) , I also like these examples from Hobby Lobby and Tower Hobbies. This is just a small sample of hundreds of pre-tested and pre-packaged models.

Glow Planes with links to conversion reviews:
[link=http://www.hobby-lobby.com/extra300.htm]Graupner Extra 300S[/link]
[link=http://www.hobby-lobby.com/pipercubj3.htm]J-3 Piper Cub[/link]
[link=http://www.hobby-lobby.com/glowtoelec.htm]Glow To Electric Conversions[/link]

Electric Planes with Recommended Power Systems:
[link=http://www.hobby-lobby.com/sport-planes.htm]Sport Planes[/link]
[link=http://www.hobby-lobby.com/warbirds.htm]Warbirds[/link]
[link=http://www.hobby-lobby.com/scalelec.htm]Scale Planes of all sizes[/link]

Tower Hobbies
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGZV3&P=7]63" 4.3lb Multiplex Magister RTF[/link]
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGZV2&P=7]Magister ARF with Glow or Electric Recommendations[/link]
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAWF5**&P=ML]49" 2.7lb Hobbico Superstar EP RTF[/link]

The RCU on-line publications with video provide excellent details for converting many glow planes to electric power. [link=http://www.rcuniverse.com/magazine/]RCU Magazine[/link]

pmmartin

I will not agree with this. Many of the ready to go out of the box models, particularly balsa ARF models have brushed motors that are way too small. You are affiliated with Hobby Lobby and Tower. They are an exception and do a good job normally. I think one of the best sources of information and properly configured models for the beginner is certainly Hobby Lobby. They should be complimented and given credit for doing it right. If you buy from another source it seems like you may be taking a chance.

I would say it is best if you have seen it fly or read a report here or the Ezone before you make a purchase unless you are experienced.

Paul

Happymcc

My Feedback: (1)

I have been switched to electric totally for almost 3 years and hvae been trying to get
into it for 15 years . Just about 3 years ago electrics made it and maybe surpassed gas.
It is hard to sort out what to get and you can waist a lot of money if you just jump in .
I went to the first SEFF and took a pad of paper and a pen and asked a lot of questions .

You were talking about gas to electric conversions . I my mind the way to go is strait
electric there are a lot of kits out there now for electric , try one of those . The gas
kits are built for gas and just to heavy .

Hope you try it and good luck

Greg Covey

Paul,

Sometimes you remind me of my wife (but not by appearance) when you suggest things without actually giving an example. Electrics have drawn more people into the hobby in just a few years than glow-powered planes did in decades. Perhaps we are talking about different things or are seeing the original topic in a different manner.

My last post gave several examples. Here are a few more...

[link=http://parkzone.com/]ParkZone[/link]

[link=http://www.hobbyzonesports.com/]HobbyZone[/link]

[link=http://www.horizonhobby.com/]Horizon Hobby[/link]