Converting my Graphite 2 to electric... - RC Groups
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Oct 28, 2017, 12:41 PM
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Help!

Converting my Graphite 2 to electric...


Greetings,

I hope I am posting in the right forum... and please forgive my complete lack of knowledge regarding electric gliding. It's my first attempt.

I decided to convert my Graphite 2 to electric. I don't need a rocket that takes off vertically or does extreme aerobatics but would like to have just enough power to get me up to altitude and help me with an aborted landing.

Estimating Graphite to be about 5 -5.5lb flying weight so is 500-600W sufficient for my stated needs ( as per Hacker site recommendation of 100W per pound for sport flying) ?

Below are recommendations for motors from Hyperflight's site:

Kontronik Kira 500-30 with 6.7:1 box, 18x10 prop, 4S 3Ah LiPo (62A, 3300 fpm)
Hacker B50 9S with 6.7:1 box, 17x10 prop, 3S 2.5Ah LiPo (84A, 2900 fpm)
Hacker B50 9S with 6.7:1 box, 16x10 prop, 3S 2.5Ah LiPo (69A, 2400 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 17x11 prop, 3S 2Ah LiPo (63A, 2400 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 16x13 prop, 3S 2Ah LiPo (59A, 2050 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 16x10 prop, 3S 2Ah LiPo (47A, 1900 fpm)

Can you recommend other motor combinations?


Lastly, how do I go about deciding which speed controller I will need?

I'm sorry about these basic questions... but would really appreciate any suggestions and insight !
Tomasz
Last edited by Nagarjuna; Oct 28, 2017 at 05:41 PM.
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Oct 28, 2017, 03:20 PM
dare to thermal
Check this:
https://www.hacker-motor-shop.com/Br...catalog&p=7201

500-600W is ok. You should have an idea of the max weight for the motor and the batterie as well for the position of the batterie in the fuselage. The hacker A30 is about 170gr - i wouldn´t go heavier. Your electrified sailplane(!) shouldn´t be heavier (or only a few gramms) than without the electric stuff. The controller is for about 30% more current than the motor: 50A plls the motor -> your controller should be able to handle about 70A.

Good luck,
Bernd
Oct 28, 2017, 03:55 PM
Cognitive dissonance
kcaldwel's Avatar
Depending on how much you want to spend, and the diameter of the fuselage, some of the direct drive motors can work well for much lower cost than a gear motor. The Turnigy Gliderdrive motors have good reports for the cost of them.

https://hobbyking.com/en_us/turnigy-...-6-1120kv.html

I usually run my ESC closer to the max current draw I am expecting, for 50 to 55A motor current I'd use a 60A ESC. Margin is nice, but ESCs get bigger, heavier, and more expensive with larger current capability.

Kevin

Edit: There are also the new Axi sailplane outrunners in a variety of kV and sizes:

http://www.espritmodel.com/axi-35-28...-motor-v2.aspx
Last edited by kcaldwel; Oct 28, 2017 at 07:48 PM.
Oct 28, 2017, 08:53 PM
Registered User
Thank you both for taking the time to reply. This is very helpful.
Tomasz
Oct 29, 2017, 12:06 AM
Registered User
scirocco's Avatar
I'm waiting for my Graphite 2E to be built

For your stated performance goals 50-60W/lb will be plenty and the B50 / Kira 500 class motors are overkill for that - the link Bernd posted has more realistic options a fraction of their weight

If the nose is big enough to get a Glider Drive in, then that is a simple and economical solution that will readily handle the power you need. Because the power needs are relatively modest and thus either the smaller 3850 @ 142g or the large 3858 @ 180g could handle the power, I'd look at how the model will balance with a motor and flight battery and use motor weight as a criterion in motor choice.

I'd be choosing the lower Kv versions: 3850-960 or 3858-840 as more suitable for an efficient climb with a large prop

You won't need any more than a 3S 1400-1600 pack to deliver 5-6 20-30s climbs - unles using a heavier battery makes sense for balance purposes.

If you are forced down the skinny geared inrunner path by the glider nose dimensions, then probably the most economical solution that will readily handle 5-600W is the Tower Ammo inrunners with their 4.3:1 planetary gearbox. As an example, the 28-45-3600 + 4.3:1 weighs about 190g and with 3S 1400 and a 13x7 starts off close to 500W, and by the 5th climb is down to about 350-400W. That's good for 10m/s in a Pulsar 3.6 ~ 1600g.
Oct 29, 2017, 01:03 AM
Registered User
Appreciate your insight and suggestions.
Oct 29, 2017, 02:42 PM
Registered User
Jebera's Avatar

Old School


Quote:
Originally Posted by Nagarjuna
Greetings,

I hope I am posting in the right forum... and please forgive my complete lack of knowledge regarding electric gliding. It's my first attempt.

I decided to convert my Graphite 2 to electric. I don't need a rocket that takes off vertically or does extreme aerobatics but would like to have just enough power to get me up to altitude and help me with an aborted landing.

Estimating Graphite to be about 5 -5.5lb flying weight so is 500-600W sufficient for my stated needs ( as per Hacker site recommendation of 100W per pound for sport flying) ?

Below are recommendations for motors from Hyperflight's site:

Kontronik Kira 500-30 with 6.7:1 box, 18x10 prop, 4S 3Ah LiPo (62A, 3300 fpm)
Hacker B50 9S with 6.7:1 box, 17x10 prop, 3S 2.5Ah LiPo (84A, 2900 fpm)
Hacker B50 9S with 6.7:1 box, 16x10 prop, 3S 2.5Ah LiPo (69A, 2400 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 17x11 prop, 3S 2Ah LiPo (63A, 2400 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 16x13 prop, 3S 2Ah LiPo (59A, 2050 fpm)
Kontronik Kira 500-36 with 6.7:1 box, 16x10 prop, 3S 2Ah LiPo (47A, 1900 fpm)

Can you recommend other motor combinations?


Lastly, how do I go about deciding which speed controller I will need?

I'm sorry about these basic questions... but would really appreciate any suggestions and insight !
Tomasz
Hello Thomas,

Forget the motors you listed above, I have some of them, they are all good ones but Old Fashion.
The Graphite is already a big plane, the hackers B50s and Kontronik Kira are also big and AMPs thirsty, they like big bateries, the heavy ones.
Today, we have some cutting-edge technologies with very little geared outrunners, they are 105g heavy and delivery a good punch on wats and big propellers.
Please check a few examples here:

https://www.reisenauer.de/artikelauswahl.php5?kid=139

And much more here:

https://www.reisenauer.de/artikelauswahl.php5?kid=39

Anything then that is a waste of money.

I do not wanna say that is the only option, everything is a compromise, those motors are not cheap but, according to your list, you are not looking for cheap stuff, other motors are cheaper but much heavier and deliver fewer watts and I have been running those motors for several years and never had a single issue, just lub the gears every year and you are good.

Good Luck!

André
Oct 29, 2017, 09:09 PM
Registered User
sneu's Avatar
Some interesting advice here---my opinion is since you have a plane that is considered somewhat heavy current by F5J standards, would be to put enough power to actually take advantage of the speed that the plane and give it enough power to preform well when the light floaters are getting blown away in the wind. The weight difference between the floater setups some have suggested and the one below are on the order of 5 oz----not much when you are already in the 80oz plus range.......

To that end that plane could easily handle a 1110/1Y/P29 motor with a 4S 850 70C battery spinning a 16x8 prop. The motor/battery is much smaller than the ones you had been looking at but able to handle over 1000 watts. (https://www.soaringusa.com/NEU-1110-1Y-6.7/1.html) The gear drive has a strong 6mm shaft that actually can take considerable abuse. The internals are the same as the P32 gear drive which is used in F5B gliders at over 7000 watts---so it is quite strong.

I have a old 75 ounce Aspire that has the above power setup----lots of fun with more than enough go to actually call it fun.

Keep the 100 gram motor/drive setups for the early morning floaters.

Have fun!
Steve Neu
Oct 30, 2017, 12:05 AM
Registered User
Thanks for all the replies, guys. Very informative and helpful.

I've read through some older posts on geared vs direct motors and it appears that geared motors are preferred for gliders or is it up for debate? I fly in a public open space and non powered gliders are tolerated so I don't want to draw too much attention from neighbors down the hill with a loud motor, which I read gear boxes can be?

I am looking at an inexpensive new Hacker B40 - 9L direct drive locally - specs listed below - and I am wondering if it could be a potential candidate to power my Graphite? Dimensions wise it t will fit perfectly.

I get fairly decent and consistent westerly winds here in coastal N. CA, and happen to have some nice hills too so power was simply to aid with altitude on less than perfect days and landings.
As it is my first foray into electric aided gliding, I don't want to spend a fortune though knowing myself it will probably evolve into an addiction ;-)

How would I know what size prop would be best choice for the B40 Hacker in this application?

Powerange max. 700W (15 sec.)
Idle Current @ 8,4V 1,88A
Resistance (Ri) 0,0143 Ohm
RPM/Volt (kv) 3333 U/min-1
Weight 158g
Diameter 27,6 mm
Length 56 mm
Poles 2 pole Insiderunner
recom. Speedcontroler 40A to 70A Brushless
recom. Timing 0° - 5°
Shaft Diameter 3,17 mm
Oct 30, 2017, 01:30 AM
Registered User
Quote:
Originally Posted by Nagarjuna
I've read through some older posts on geared vs direct motors and it appears that geared motors are preferred for gliders or is it up for debate? I fly in a public open space and non powered gliders are tolerated so I don't want to draw too much attention from neighbors down the hill with a loud motor, which I read gear boxes can be?

I am looking at an inexpensive new Hacker B40 - 9L direct drive locally - specs listed below - and I am wondering if it could be a potential candidate to power my Graphite? Dimensions wise it t will fit perfectly.
Gear box noise in the power range you are considering is inconsequential. In fact, the Hacker you are considering is probably not a great choice because when you do the performance calcs for that kv & lack of gear reduction, you will very likely land on a smallish Pitch x Dia combination to achieve efficiency. That prop may likely make more noise than the background sewing machine hum of a gearbox. Go on Youtube, Google F5J & listen to any of the launches. They are very quiet because of larger props spinning at lower rpm. The small diameter shaft on the Hacker will not be your friend on any kind of a nose landing & it limits your selection of folder spinner hubs. The motor can diameter & length is very similar to 11xx series Steve suggested... just without the gearbox.

http://www.castlecreations.com/flight-calcs This is a very good scoping tool. Just select the appropriate parameters & you can vary & determine suitability including things you haven't considered yet - requisite pack size / cell count / C-rating, ESC amp rating, power level, duration & thrust. There is no real 'debate'. There is just a series of pros & cons within practical limits that you have to factor for yourself.
Oct 30, 2017, 08:16 AM
Registered User
sneu's Avatar
Quote:
Originally Posted by Nagarjuna

Powerange max. 700W (15 sec.)
Idle Current @ 8,4V 1,88A
Resistance (Ri) 0,0143 Ohm
RPM/Volt (kv) 3333 U/min-1
Weight 158g
Diameter 27,6 mm
Length 56 mm
Poles 2 pole Insiderunner
recom. Speedcontroler 40A to 70A Brushless
recom. Timing 0° - 5°
Shaft Diameter 3,17 mm
That motor needs a gear drive for glider use---without one you will have to use a much smaller prop than is optional for a large glider. Also the shaft is too small to survive typical glider spot landings in a direct drive configuration. That motor is better suited for a pylon racer.

Steve Neu
Oct 30, 2017, 10:59 AM
Registered User
Thanks for answering my questions and dispelling my ignorance.
Looks like I'm in the market for a gently used 1110/1Y/P29...
Oct 30, 2017, 11:27 AM
Cognitive dissonance
kcaldwel's Avatar
You need a motor with a kV rating that will turn a big prop somewhere around 10,000 rpm. The kV number tells you how many rpm per volt the motor will try to turn - there will be slippage due to the prop load. For direct drive, you also need a motor with a big enough shaft to survive landings on the spinner. A 4mm shaft is minimum, 5mm will be better. Direct drive is simpler and cheaper, but most newer glider fuselage only have room for a 28mm diameter motor max. Small diameter motors have low power ratings at lower rpm and low torque, so you end up having to use a high rpm motor with a gearbox to drop the prop rpm. If you have room for a 36 to 37mm diameter motor, direct drive will work well and can be very simple and cheap.

A 3S battery has a nominal voltage of 11.1 volts, and a 4S one 14.8V (3.7V x number of cells in series). Battery voltage can sag well below that, depending on the size (mAh) and C rating, but starting with the nominal voltages will get you started. So a 1000kV motor on 3s is trying to turn about 11,000rpm, and a 600kV motor on 4S will try to turn about 8880rpm. Big props turning slower will give you a better climb rate.

I have an old 2.2kg (78ounce) glider (Onyx) that I electrified with a very low-cost ($16 at the time) 37mm, 150g outrunner. There are thousands of flights on the motor at this point, and is still going strong. It is a 600kV motor with a 5mm shaft that I have been running on low cost Nanotech 4S 1300mAh 45C batteries with a cheap 50A ESC and BEC for the airborne power. It gets 3 climbs to 150m in 20 seconds or so on a battery charge. The 4S battery allows you to get higher power (Watts = volts x amps) levels at lower amps, so you can use a smaller ESC. I did have to turn the motor shaft around though, so it is not a drop in.

https://hobbyking.com/en_us/turnigy-...___store=en_us

With the older, larger diameter fuselages, it is quite possible to have a low cost direct drive system work very well, even on a heavier glider. Direct drive is definitely quieter than any gear drive set-up I have, and is generally pretty maintenance free.

Kevin
Last edited by kcaldwel; Oct 30, 2017 at 11:35 AM.
Oct 30, 2017, 11:30 AM
Registered User
Quote:
Originally Posted by kcaldwel
You need a motor with a kV rating that will turn a big prop somewhere around 10,000 rpm. The kV number tells you how many rpm per volt the motor will try to turn - there will be slippage due to the prop load. For direct drive, you also need a motor with a big enough shaft to survive landings on the spinner. A 4mm shaft is minimum, 5mm will be better. Direct drive is simpler and cheaper, but most newer glider fuselage only have room for a 28mm diameter motor max. Small diameter motors have low power ratings at lower rpm and low torque, so you end up having to use a high rpm motor with a gearbox to drop the prop rpm. If you have room for a 36 to 37mm diameter motor, direct drive will work well and can be very simple and cheap.

A 3S battery has a nominal voltage of 11.1 volts, and a 4S one 14.8V (3.7V x number of cells in series). Battery voltage can sag well below that, depending on the size (mAh) and C rating, but starting with the nominal voltages will get you started. So a 1000kV motor on 3s is trying to turn about 11,000rpm, and a 600kV motor on 4S will try to turn about 8880rpm. Big props turning slower will give you a better climb rate.

I have an old 2.2kg (78ounce) glider (Onyx) that I electrified with a very low-cost ($16 at the time) 37mm, 150g outrunner. There are thousands of flights on the motor at this point, and is still going strong. It is a 600kV motor with a 5mm shaft that I have been running on low cost Nanotech 4S 1300mAh 45C batteries with a cheap 50A ESC and BEC for the airborne power. It gets 3 climbs to 150m in 20 seconds or so on a battery charge. The 4S battery allows you to get higher power (Watts = volts x amps) levels at lower amps, so you can use a smaller ESC. I did have to turn the motor shaft around though, so it is now a drop in.

https://hobbyking.com/en_us/turnigy-...___store=en_us

With the older, larger diameter fuselages, it is quite possible to have a low cost direct drive system work very well, even on a heavier glider. Direct drive is definitely quieter than any gear drive set-up I have, and is generally pretty maintenance free.

Kevin
Very good info. Thanks Kevin !
Oct 30, 2017, 02:50 PM
Registered User
If you haven't done so already, begin with test-balancing the plane to see how much weight you need in the nose to get it to balance properly.

I have two Graphite-2, one Graphite-2e and one Graphite-2 (F3J version). On my Graphite-2e I need a LOT of weight in the nose. I had to replace my previous motor (it burned due to a faulty ESC) this summer and I chose a MVVS 5,6/690 GLIDER, which, together with a 3S2200, makes the plane balance almost perfectly when the battery is almost as far up front as possible.

I don't remember the power consumption, but together with an Aeronaut 16x10 I climb to 200m in 20-23s. I ran it a couple of times on a 5S1500 but that was not very efficient and didn't supply much static thrust so the launches were quite scary. I think 4S would be better than 3S but I don't have any and I'm not willing to spend money buying one just for a test when 3S is good enough.

Remember though that the Graphite-2e has the tail-servos in the tail, the F3J-version (Graphite-2) has the tail-servos in the nose (at least mine has) so it probably don't need that much metal up front.


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