hallstro

This question has likely been answered, but I am new to e-power.

When considering a glow conversion to e-power, what is the electric motor equivalent to the Cox 0.49 size engine? How are glow engine equivalents computed?

Thank-you.

Dave

Time Pilot

Pulled this off Wikipedia:

The Tee Dee was tested by Aeromodeller Magazine in 1962 and the output power was recorded to be .105 bhp (78 watts) @ 22,000 rpm with a max torque of 5.5 oz.in. at 18,000 rpm on 25% Nitro. [6] (Note: The modern Norvel AME 049 engine which has a ceramic coated aluminum piston outputs .2 bhp (150 watts)@ 17,000 rpm).

One horsepower = 746 Watts.

There are many factors to be considered when converting, propeller efficiency being one.

You're going to want to start looking in the 150 Watt class motor, and then either gearing the motor for the proper prop if you use an inrunner/brushed motor, or getting an outrunner with the appropriate kv (how many times the motor will turn per minute x the volts). A 1000 kv motor will spin 1000 times in a minute with one volt applied; 10,000 x per minute with 10V applied.

For fast planes, we choose higher kv's and smaller props, for slow flyers lower kv motors and larger props, and somewhere in between for those inbetween planes.

What kind of a plane are you trying to power?

hallstro

Thanks for the info Time Pilot!

I have a ton of old magazines and it seems that 1/2A flight was very popular back in the early 70's. I have many of the articles scanned and am considering scaling them up in Photoshop for building.

The 1/2A SST (RCM magazine - pictures soon) is a nice design as are many other types featured in American Aircraft Modeler, RCM, etc. I have a few acres and it would awesome to step out the back door and launch a small powered ship across the pasture without disturbing the neighbors. While they aren't that close, the whine of a Cox screamer might be a bit much.

I am very new to e-power and it seems to be the way to go in the future. My garage full of glow models will have to wait!

I keep scanning the magazine articles and posting them out online, in case anyone is interested. I post at http://cid-7528d863b07432c0.skydrive.../RC%20Aircraft from time to time.

Thanks again.

Dave

Time Pilot

This the one?

http://www.rcmmagazine.com/store/sto...ctsaREmsA6G9a6

My opinion for that plane, and please seek the advice of others, would be to look for a motor in the 150 watt class that spins an 8x6 or maybe 9x6 prop.

hallstro

Wow! Great information. Thank-you so much for the advice.

Yes...that's the design. I built the 1/2A SST way back when and powered it with a throttable Cox .049 engine. Now that I am reliving my childhood (grin!) except with the addition of computer radios, micro-servos, and LiPo batteries, it would wonderful to give this one a try again.

Half the fun of RC is building and this one affords the opportunity to cut a constant-chord foam wing.

Thanks again for your terrific help with my newbie question

Dave

aeajr

My Feedback: (2)

EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT
http://www.rcuniverse.com/forum/m_7100376/tm.htm

As you will learn from the article, asking what the equivalent of a .049 is not the best approach. The best approach is to start with the weight of the plane. In truth, there is no exact equivalent of an .049, but there are many motors that will fly the plane that used to have a .049 motor. .

Glow motors are not the same as electric. They don't size the way glow motors size so don't try to do it that way. Read the article on sizing an electric power system.

What you will learn is that in the world of electrics we talk about watts/pound, not glow motor equivalents. So, tell us about the plane you are trying to power. How much does it weigh as a glow plane. How much does it weigh empty.

And because electric motors can be modeled to fit many different situations, there are more questions to ask.

What kind of flying are you trying to achieve?

Indoor? Slow flyer? Scale flying? Sport aerobatics? (This might be the most typical glow flying style) Pattern? Pylon? 3D? 4D? ( himmm, some options not available to glow pilots. )

Electric motors are very flexible. You can take the same motor and change how it behaves by applying different voltage and different props. For example, I have a brushless outrunner in one of my gliders. I can run it with a 10X7 prop and an 11.1V pack. The motor produces 300 watts and will take the glider straight up. I can also fly it on a 7.4v pack with an 11X8 prop and the motor will produce 150 watts. It takes my glider up at a 45 degree angle and I can make the plane lighter with the smaller battery pack. Same motor with two set-ups.

The point is not what motor I am using but what watts per pound power/weight ratio I am running.

It seems more complicated, but it can also become pretty easy once you get the feel. And let's face it, not all .049 motors are equal either. And electric pilots have access to more types of flying than glow pilots. How would the little lady feel about you lighting up your .o49 in the living room ... hummm?

There are programs that can help you pick the right motor/battery/prop combinations for a given plane. Motocalc is one example. Virtually all of them start with the weight of the plane in ready to fly trim.

hallstro

Wow...thanks so much for the good insight. I agree that switching from traditional glow to electric power is a change of mindset. I do have much to learn and your terrific info and links are greatly appreciated.

I have a number of smaller aircraft designs in mind for conversion to electric power because I am primarily a builder.

I will continue to monitor the Forums and will check the links you provided. I learn something new each I log on and experienced modelers like you are so kind to pass on the wealth of knowledge you have gained.

Dave

aeajr

My Feedback: (2)

Glad to help.

As a biuilder you may find more flexability in electric because you can build for a wider variety of situations.

Sailplanes

indoor

3D and 4D (planes that fly backwards)

Why not build a slow flyer that you can fly in front of the house, or even in the house? My friend built one that is under an ounce, all up. You can even get them RTF so you can fly while you buld the next one.

Vapor
http://www.horizonhobby.com/Products...ProdID=PKZ3300

Or this arf
http://www.horizonhobby.com/Products...ProdID=GWS1040

As a builder, what is your focus?

jsflagstad

I have that same plane, I bought it from my Woods class teacher (who also organized our RC club) in 7th grade (1985). I still have it somewhere, it has a TeeDee .049 on it.

hallstro

Hey jsflagstad, did you ever fly the model? Was it a good flyer? I built one of these ships many moons ago and sold it before I ever flew it! You should pull it out of the closet, dust it off, and give it a go.

Let us know how it goes.

Dave

jsflagstad

Well, it was my trainer with a wide open TeeDee .049 so it saw some rough stuff. It is in OK shape, but it needs some work.

stoick

RE: Electric Equivalent of .049? I am building a Guillows balsa model of 'The Spirit of St Louis ' which calls up for a 049cu glow engine. What size electric engine can I put into it for scale flight please

jsflagstad

I think the best advice would be to look in the 150 watt power range.

JS

Mooch123

I am also a newbie to electric. I have an older bd5 1/2 that originally had the .049. My dad actually flew one of these, and was hoping to put electric in the pusher configuration. As i understand, perhaps the 150 watt engine would be suitable. It weighs 23 oz. with foam monocote covered wings. Any suggestions would be appreciated.