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want to make glider electric

Old 01-30-2009, 09:57 AM
  #1  
gwill
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Default want to make glider electric

I have an Explorer 2m glider by thunder tiger. http://www.rcuniverse.com/product_gu...cfm?kit_id=313. I have used a power pod with a cox .09 engine on it and it has worked great. I want to make it electric. Any help on what to get and tips would be great.

Thanks
Old 01-30-2009, 10:54 AM
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qldviking
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Default RE: want to make glider electric

to convert to electric is quite easy, The main point to watch is using some down thrust, I usually add about 3* down and also about 2* left thrust. I usually cut the nose block off, make a 1/8" ply firewall, with vent holes set to the angles mentioned. I glue this in with epoxy and I like to use 1/8 x 1/8 tristock to brace all round. balancing point remains the same.
Old 01-30-2009, 11:42 AM
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jollyroger
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Default RE: want to make glider electric

gwil, do you plan to use the power pod to mount the motor in?
Offhand, I would mount the motor in the nose of the plane instead if it's not too much trouble.
Now, it depends how large the glider is and the flying weight. You only need 60-70 W/lb. for most of these types of gliders and that's a lot. You could even get by with 50W/Lb.
On my Great Planes Spectra, I use a Multiplex480G(4:1) and 13X6.5 prop along with a 3S pack. My DJ Aerotech Chrysallis uses a Hyperion 3013-14 and 13X6.5 folder on a 2S pack. Total power draw is 204 watts. At 37 oz, it's plenty for a glider such a this.
My tendency is to use a 2S pack and enough prop to provide enough thrust, not speed...remember these planes aren't F5B rockets.
So go easy on the watts, good props such as the Aeronaut CF are some of the best unless you want to spend your wallet empty on A Rudy Prop.
There are plenty of small outrunners which will work great with these types of gliders.
Good luck and cheers
Old 01-30-2009, 01:50 PM
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Tall Paul
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Default RE: want to make glider electric

Here's three ways to mount..
The pylon mount has less of a configuration change, should you want to go back to the pure glider. ( You won't. )
With a can motor and gear box, usually there's a firewall involved for the mount.
For a 400 sized outrunner, the rear stick mount is very easy to install.
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Old 01-30-2009, 02:05 PM
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qldviking
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Default RE: want to make glider electric

I like the firewall mount system, The 2m glider I have converted I often switch from elect to straight glider and back again, I have a nosecone fitted with 2 small nylon bolts that scew in the same holes the motor mounts to, and no other mods needed. My cone is moulded from a plastic drink cup (heathrunk over a mould) with a 3/16 balsa base which the screws screw into. When I get the glider back from my nephew I will take photos
Old 01-30-2009, 03:19 PM
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gwill
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Default RE: want to make glider electric

I am not going to use a power pod when I go electric.
Old 02-08-2009, 08:03 AM
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maynardrupp
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Default RE: want to make glider electric

I don't know much about electric power, but everyone with regular electric airplanes use brushless motors and LiPo batteries. All of the small geared setups that I have seen for 2 meter gliders seem to use the "480" motor. I think this is not a brushless motor. They also seem to use the heavier NiMh batter packs. I do see the above photos and one of them has an E-Flite 450 brushless motor with no gearbox and a hub for a folding prop. Do you not need a gearbox with those brushless motors?I am trying to upgrade an old "electric Lady" with a modern power setup. I will mount the power package in the nose.
Old 02-09-2009, 06:01 AM
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Default RE: want to make glider electric

The link provides no information about the plane's weight or construction.

It looks like a built up wood design. I am going to guess it weighs about 40 ounces without the power pod. Let's plan for 45 ounces all up with the electric motor and lipo batteries, or about 50 ounces with NiMh batteries.


Forget brushed motors - you want a brushless motor.

You can go for an inrunner with a gearbox, or an outrunner, depending on how much room you have inside the fuselage. An inline gearbox will fit in a narrow nose. An outrunner needs more width to allow the outer motor casing to spin freely.

plan for 60 to 80 watts per pound. At 45 ounces your glider weighs 2.8 pounds. So something in the 175 to 250 watt range would work nicely, depending on how steep a climb you want.

You want to select a motor that will take a 9 to 12" prop

You can plan to run on 2 cell or 3 cell lipo or 7-10 cell NiMh.


Here are some ideas. These are just examples.

I have this rimfire 30-35-1250 in my 2M Dust Devil.
http://www3.towerhobbies.com/cgi-bin...&I=LXLWU0&P=ML
On 2 cell lipo with an 11X8 prop, it runs about 150 watts on a 2 cell lip. Gives me a 45 degree climb an pulls 20 amps on the bench. I like it.

ON a 3 cell lipo with a 10X7 it runs about 280 watts pulling about 27 amps on the bency. The plane will climb at just about 90 degrees.

Or this maxx pro package. Replce the prop with a folder of the same size
http://www.maxxprod.com/mpi/mpi-264_...ombo%2019A.pdf

Or a 28-15-3043 inrunner which includes a gearbox. This would run with a 3 cell lipo and a 12X6 prop.
Here you have a long thin package that can fin in a narrow space and does not requre clearence to deal with a spinning can.
http://www.maxxprod.com/pdf/HB2815-xx43.pdf

These are just examples.

Depending on how much lead you have in the nose of the plane the motor or motor/gearbox or motor/battery may simply replace the lead so the weight gain may be minimal. In fact, as compared to the powerpod, the plane may be lighter.

In all cases be sure to provide airflow for cooling the motor/battery and don't forget an exhust hole for the hot air.
Old 02-09-2009, 09:18 AM
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maynardrupp
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Default RE: want to make glider electric

Thank you very much for that information. I will probably opt for the Maxx Prod. brushless gearmotor. The brush type motors always needed a gearbox to swing a big folding prop like a 12". Can the brushless motors swing that big of a folder without a gear box? My plane was a Goldberg kit called and was an electric version of the "Gentle Lady". The plane is in Detroit and I am currently in Miami so I cannot be more specific.
Old 02-09-2009, 10:46 AM
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Default RE: want to make glider electric

some of the brushed motors swing a 12" prop quite well, my old impulse has a cobalt 50 that swings a 13 x 7 @ 14,700rpm, 65 amp esc, 10 cell pack, and flies really well with that set up. I did try a newer brushless/lipo setup. but needed more ballast so went back to the old one and used the new set on another glider. I stull fly comp with it and its still cometitive against newer gliders, so I am quite happy with it
Old 02-09-2009, 12:01 PM
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aeajr
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Default RE: want to make glider electric


ORIGINAL: maynardrupp

Thank you very much for that information. I will probably opt for the Maxx Prod. brushless gearmotor. The brush type motors always needed a gearbox to swing a big folding prop like a 12". Can the brushless motors swing that big of a folder without a gear box? My plane was a Goldberg kit called and was an electric version of the "Gentle Lady". The plane is in Detroit and I am currently in Miami so I cannot be more specific.
The outrunners can swing large props without gearboxes. The inrunners typically use a gearbox.
Old 02-09-2009, 12:10 PM
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Default RE: want to make glider electric

Just make sure the Kv rating chosen is low enough for a DD outrunner turning a 12" prop, especially if you plan on 3S lipo to get the Watts needed at a reasonable current level.
Pete
Old 02-09-2009, 12:33 PM
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Default RE: want to make glider electric


ORIGINAL: pilotpete2

Just make sure the Kv rating chosen is low enough for a DD outrunner turning a 12" prop, especially if you plan on 3S lipo to get the Watts needed at a reasonable current level.
Pete
To say this differently, look at what props are recommended for that motor. Maxx pro, for example, provides charts that tell you which prop and which battery will provide what amp draw and watts so you can use these as guides to help you select the right combination.
Old 02-10-2009, 01:14 AM
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Default RE: want to make glider electric

There's a number of smaller motors in around the 2 to 3 oz mark that'll work well for this use. However these motors often come in a variety of windings that use the same housings and magnets. Also how the windings are connected alters the Kv value and the ability to turn small or large props. So while I can understand that aeajr is trying to keep the brain work down for you I would say that at least SOME homework is going to be needed to find the right motor and avoid adding any more weight than you must.

Figure on adding around 6 oz to the model once you remove the flight pack battery and replace it with a Lipo, ESC and motor. The weight boost may be less but 6 oz more is a safe number. With this much in mind weigh your model as it sits as a pure glider. Add the other 6 oz to that figure and then calculate the power you'll need based on 70 watts per pound. Some will suggest that 70 is too low but they are used to models that climb like modern jet fighters. 70 will EASILY produce a spirited 40 degree climb angle that'll have you at 500 feet in less than one minute. It IS supposed to be a sailplane first and foremost after all. In fact I've flown a sailplane and an old time prewar free flight model with RC and electric power with far less. My climbs at 43 watts per lb are more of a strong uphill glide but even at that level my models hit 500'ish feet in about 1.5 minutes of power. So don't feel you need any more. In fact anything over 60 watts per lb would be awesome. The motor and battery pack needed for 60 will be all the lighter as well. And lighter always flies righter.....

What's the Kv value you ask? It's the RPM per volt that the motor will try to turn the prop. Motors with lower Kv values are like a car in first gear. Lots of grunt with big props but not very fast. Sounds like just what a glider needs because it IS what a glider needs. Motors with mid Kv values for their size are great for casual sport flying models. And high Kv values are good for fast speedy models. Note that as motor size goes up the Kv range falls. So don't try to compare small case size motors to large case sizes. But within the range of motors you want for your model you can compare Kv values directly.

For a typical 2 meter model you want a motor that will handle 250 watts comfortably so it doesn't overheat. It should be able to run steady at around 20 amps with a 30 second burst at 25. Not that you'll want to run it that hard for long. Also the Kv value should be less than 1200. At 1200 the prop will be in the 10 inch diameter range on 3 cells. If you can find a motor with a Kv under 1000 then it'll likely be grunty enough to work a 12 inch folding prop without over heating.

At least all this is how I'd pick a motor for my models. In fact I did and I'm updating the motors in my sailplane and old timer from the old brushed can motors to newer brushless. In my case I'm also losing around 8 to 10 oz on each model by going with the new stuff over the old.
Old 02-10-2009, 06:33 AM
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Default RE: want to make glider electric

Last year I got tired of the high start for everyday thermalling, so I electrified my GP Spirit 2m. It looks to be in the same class as the OPs, so I'm offering my setup.

I started with the GP T-600R motor, a 7.4 LiPo, a gearbox, and a simple on-off switch for the motor. This setup was cheap ($19 for the motor, gearbox, and switch). This setup had been recommended by Great Planes on their website for this class glider. The results were less than satisfactory.

Last month I switched to a Rimfire 35-30-950 Outrunner, an 11.1v 1250 mah LiPo, and a 35 amp Silver Series ESC. The total weight was about 6 oz less that the brushed motor setup (All up weight on the plane is now 39 oz). With a 10x6 Folding prop, the plane now easily climbs out to 0ver 500 feet in 30-45 seconds. I get about 6 to 8 climbouts on a single charge.

To mount the motor, I cut off the nose, added a plywood firewall, and just screwed the motor mount directly to the firewall. I'm going to make a fiberglass cowl to fair between the spinner and the firewall.

Brad
Old 02-10-2009, 08:36 AM
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Default RE: want to make glider electric

gwill,

BMatthews and I are of similar mind in regards to your need. Don't let small differences concern you as this is not an exact science. Whether 40 watts or 50 watts or 60 watts is the minimum is a matter of personal preference and objectives, not right or wrong. Whether 200 watts or 250 watts or 300 watts is too much is likewise a matter of opinion.

Too much power is never a problem as long as your throttle is on an variable control. On my Dust Devil I ended up with a 300 watt motor that takes the plane straight up using a 3 cell lipo. I simply don't use full throttle. In fact I changed the prop and went to a two cell which give me a more moderate climb. I didn't do it because the 3 cell 300 watt set up was bad. I did it because I have four 2 cell lipos and only 1 suitable 3 cell lipo. So I can swap packs with the 2 cell set-up. I get about the same climb at full throttle on the 2 cell set-up as I do on the 3 cell set-up at about 60% throttle. So either one works to provide a climb that meets my expectations.

What will you likely use for batteries? Lipo? NiMh? This may be a matter of what you have as opposed to what we suggest.


I don't know how much you know about electric power so I provide these resource links:

> EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC FLIGHT
> http://www.wattflyer.com/forums/showthread.php?t=31071
> http://www.rcuniverse.com/forum/m_7100376/tm.htm
Old 02-13-2009, 09:22 AM
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Default RE: want to make glider electric

I don't know much about electric power, … I am trying to upgrade an old "electric Lady" with a modern power setup.
I know less than nothing but have traveled the same road with a Gentle Lady.

I used a brushed geared motor that was available. First I used a 6 cell 1400mah NiCad and then a 7 cell 1200mah NiCad pack that was available. Both were way down on power and not any fun.

A friend brought a 3-cell A123 2300mah pack to the field and the flights were very successful.

Bill
Old 02-13-2009, 09:32 AM
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Default RE: want to make glider electric

During most discussions around electrifying gliders we make references to watts/pound as a benchmark for selecting motor/battery combinations. If this is not something that is familiar to you, you should find this discussion helpful:

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

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