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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Hirobo Freya/Funkey MD500D Electric
07-08-2018 02:01 AM  4 months agoPost 1
PaulBowen

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Victoria, Australia.

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Hello

I am interested in possibly converting my Freya Evo to electric so that it can be fit into a Funkey MD500D fuselage. So on that note I have some questions.

Is there a quality 5 blade main rotor and blade combination that will work with the Freya without stripping gears or drawing 200 amps? I would be using Kontronik motor and ESC and aiming for about 1200-1400rpm. I would require a setup that would give a minimum 10 minutes of flight but a preference for 15 minutes.

Does anyone have any experience with this kind of setup?

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-08-2018 02:08 AM  4 months agoPost 2
eeeeky

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Roosevelt UT USA

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The century 5 blade diamond heads are awesome. Id stay away from the chinese stuff, they can get sketchy. Vario also makes a great rotorhead. Seems like when i was testing the 5 blade heads back in the day, on a predator swinging 670mm blades they it was pulling about 80A to fart around, and about 140 pulling it as hard as my little batteries could handle.

Lets Fly!

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07-08-2018 06:41 AM  4 months agoPost 3
PaulBowen

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Victoria, Australia.

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As far as I can see the Century unit is no longer available. The Vario head is quite nice but with blades and a swashplate/follower it would almost cost more than the rest of the helicopter.

Does anyone know what the Roban units are like.

BTW my current gearing is 12t pinion driving a 95t main.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-16-2018 11:15 AM  4 months agoPost 4
Richardmid1

rrProfessor

Leeds, England

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You would need around a 500kv motor on 6s 10Ah. Easily 15 minutes scale flight.

60% of the time, it works every time!

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07-16-2018 06:15 PM  4 months agoPost 5
cobieg

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Florida

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I just test flew my 600 size with a 5 blade Diamond rotor head. I had to shim a couple of shafts to take out the end play. Other than that, it is a very nice product if you can find one.

Ron

I didn't crash. I just ran out of airspeed, altitude, and ideas all at the same time!

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07-17-2018 08:45 AM  4 months agoPost 6
Andy01

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Brisbane, Australia

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Richardmid1
You would need around a 500kv motor on 6s 10Ah. Easily 15 minutes scale flight.
With the stated gearing and 6s & 500kV, the most he would be able to govern to is about 1200rpm.

RPM = 500kV x (6x 3.7V) x 0.9 (efficiency) x 12T / 95T = 1262rpm at 100% throttle towards the end of the flight.

Governing to 95% would yield 1199rpm, which is fine if he wants to run at the low end of his stated range. No idea what blades are planned, but I would think that a 5 blade 700 for example would run at 1200rpm as a maximum, so perhaps the intended blades are smaller.

With a Kontroniks ESC, the motor kV is almost irrelevant as long as it is fast enough - it can be heavily governed, unlike CC ESCs.

I would always suggest a HV setup for a larger scale heli, not 6s. A 12s (2x 6s in series) would provide the same Watt-hours (as 2x 6s in parallel), but at half the amps, which often increases efficiency and reduces heat.

If I were to guess at a weight it might be around 20lbs maximum, and a good rule of thumb (for gentle scale flying) would be around 60W/lb for a 5 blade. This gives 1200W for FF, about 1500-1600W to hover, and around 2500-3000W for those instantaneous spikes getting out of an Oh $hit moment. This means that on 12s you would draw a continuous 25A while hovering and less for FF.

This means that you are HIGHLY unlikely to ever see anywhere close to 200A unless you are trying to run 2000rpm and do frantic 3D.

Even with a 6s setup, it would only be around 50A, so no need for a big powerful motor or a huge ESC.

Heat on both is the biggest issue you are likely to face with a fully closed in fuselage.

As for flight time, if you keep the weight down and use 2x 5000mAh lipos and fly gently at about 1100-1200rpm, I would think that 12-15 minutes would be quite possible.

Colin

Vario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )

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07-17-2018 10:28 AM  4 months agoPost 7
PaulBowen

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Victoria, Australia.

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Thanks guys for the very interesting info. I have a Jive 80HV Pro I would like to use and would use a Kontronik motor of some description. I would be looking for some nice light narrow chord scale blades but don’t really know which to use. I have owned a pair of Spin 800’s and 110 tails but they were terrible quality. Not sure why, Friday afternoon batch maybe?

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-17-2018 11:20 AM  4 months agoPost 8
Richardmid1

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Leeds, England

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Andy01
Even with a 6s setup, it would only be around 50A, so no need for a big powerful motor or a huge ESC.
More like 32A average draw.

To run 12s he would need a 250-300kv motor which aren't that common if available at all.

A 500kv motor and 120A esc on 6s would barely heat up at all in this setup and a 6s ESC is much cheaper than a 12s ESC.

Go to a 520Kv motor, or use a 13T pinion (more efficient and less gear stripping potential), or run the optional 93T main gear. Many more options for motors and gearing when run on 6s.

60% of the time, it works every time!

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07-18-2018 09:24 AM  4 months agoPost 9
Andy01

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Brisbane, Australia

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A XNova 4035-300kV would do the job very nicely. That is the motor I use in my EC-145.

As I said above a Kontroniks ESC (active freewheeling) allows him to govern at low %, so he probably could use a 500kV motor. He also said above your post that he planned to use a 80A HV ESC.

I think that 32A at 22.2V (= 710W) might be a touch optimistic unless the heli is super light. I would think that the best that would be likely in normal scale forward flight with 5 large blades would be around 55W/lb of weight (generally 50W/lb is the accepted rule of thumb for a 2 blade), so to get down to 710W, the heli would weigh around 710 / 55 = 12.9lbs (under 6 kgs) which is probably doable with small lipos and no need for any ballast but then 15 minute flights might be stretch using small lipos.

In my experience, all 3 of my larger helis are about 18lbs (the EC-145 flies, but no doors etc as it is not complete), and;

Long Ranger - 2x 710mm @1350rpm flies on about 850-900W, so about 49W/lb
Seahawk - 4x 600mm @1350rpm flies on about 1000-1100W, so about 58W/lb
EC-145 - 4x 820mm @1050rpm flies on about 950-1000W (if I am very gentle), so about 54W/lb and hovers at about 68W/lb.

Colin

Vario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )

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07-18-2018 03:01 PM  4 months agoPost 10
Richardmid1

rrProfessor

Leeds, England

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You are correct, I didn't take the weight into account.

So if it is 60W/lb and weighs 15lb+ then anything over about 12 minute flights would be a struggle, correct?

60% of the time, it works every time!

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07-18-2018 11:28 PM  4 months agoPost 11
Andy01

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Brisbane, Australia

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Pretty much - assuming 2x 5000mAh lipos. If the OP stepped up to 6000mAh then 15 minutes might be doable.

It depends a lot on weight and flying style. Some MD500s get flown a bit more aggressively than, say, a Long Ranger if they are modeled after a "sports" style or military heli.

To give you an idea, I get 2x 6 minute flights on my Vario Long Ranger and put back about 3600mAh into each of the lipos, so stretching to the 80% "limit", I could get about 13½ minutes. In my bigger EC-145 I get 8 minutes and put back about 3300mAh, so 4000mAh (80%) would give me nearly 10 minutes. The EC-145 is a bigger and probably heavier model than the OP has though.

To answer a couple of the OP's questions;

Make sure you tame down the ESC settings to avoid stripping/melting plastic gears. I have Castle ESCs and I obviously use a very soft start (about 40 seconds spool up), and also slow down response times (rate of change of speed), governor gains etc. I have no idea about Kontroniks settings, but I would think that they would have similar settings.

As regards blades, I am very happy with my Helitec blades. They have two ranges for the larger sizes - the pairs which have a wider chord (64mm from memory in the ±800mm blades) and I think 56mm in the multiblade sets. I went with two pairs of 820mm x 64mm for my EC-145. The guy's name was/is (it is a few years since I bought mine) Kai and he was probably the most helpful / communicative person I dealt with at any European shop (most of them either don't speak much English or are very slow/poor to respond). On Scalerchelis.com, there has been several people say that they were not happy with Spin, and moved to Helitec and were impressed.

Colin

Vario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )

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07-19-2018 10:46 AM  4 months agoPost 12
PaulBowen

rrKey Veteran

Victoria, Australia.

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Thanks guys for such great information.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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