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Home › Scale › ✈️Aircraft › Scale Heli › Roban Scale Helicopters › Just Picked up a Roban EC-135
03-29-2017 08:37 PM  32 months ago
0Post 21
TailKiller

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Panama City, FL

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The gear ratio for these Roban 700 models is the same.. 13.8:1 The main gear and secondary gear are both 78 tooth, the white main gear pinion gear is 20 tooth and the motor pinion pulley is 22 tooth. They suggest a 530kv for the 2 blade helis and a 450kv for the 4 blade helis. The 2 blade spins higher rpm then the 4 blade. The extra 40kv will mean that you will be able to get a little higher rpm if you so choose.Dennis
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03-30-2017 02:50 AM  32 months ago
0Post 22
jwest

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cincinnati ohio

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Darn it! I just counted all the gears and you already had it posted.
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03-30-2017 03:04 AM  32 months ago
0Post 23
jwest

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cincinnati ohio

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Yes, so I guess a little more to it than than my Trex. The main shaft goes through two reductions. I didn't do the math but 13.8:1 is the number I presume. The tail is different than these pictures from the manual. It is not gear reduced but reduced with pulleys.....68t vs 22t... or about 3:1. I believe this is a higher ratio than the other Roban 800s due to the nature of the fenstron tail. I read the fenstron should be at about 15,000 rpm
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03-30-2017 03:18 AM  32 months ago
0Post 24
jwest

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cincinnati ohio

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So at the ratio of 13.8:1 on a motor with a Kv 450 running a 12S pack......should give me a rotor head speed of 1477rpm at full charge pack...correct?

I was figuring about 1500rpm average so maybe a slightly higher Kv may be required. 490Kv would give me 1608 rpm at full pack and 1417 rpm about mid charge.
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03-30-2017 03:28 AM  32 months ago
0Post 25
jwest

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cincinnati ohio

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So.....an equally important question since the fenstron can be a little weak with low rpm. What would my tail rotor speed be at with a 490Kv motor?

motor pinion 22t
main gear 78t

3.55:1

tail reduction gears,which is coupled with the main gear

tail rotor 68t
tail pinion 22t

3.09:1

Do you subtract the two to get the tail rotor rpm ratio?

1.46:1

My math:
on a 490Kv motor full pack, tail rpm 15,281
----tail rpm on half charge pack 13,462

Can anyone check my math? 15K rpm is what Roban states the tail will produce, so hopefully my stuff is accurate
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03-30-2017 09:43 AM  32 months ago
0Post 26
Andy01

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Brisbane, Australia

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RPM = 490kV x 44.4V x 0.9 / 13.8 = 1419rpm at 100% throttle towards the end of a flight.

So, if you governed to, say, 90%, you would get a headspeed of around 1280rpm, which is probably a bit fast for a 4x 700mm heli, so you may need to govern to a lower headspeed, which should be fine with a Kontroniks ESC.

As for tail speed, it would look like you main rotor reduction is 13.8:1, and your tail rotor reduction is probably 3.55 / 3.09 = 1.15:1 (I am guessing that your naming of the gears is possibly incorrect, and the tail pinion is actually the larger 68T gear and the driven gear is the smaller 22T gear, which would speed the tail up, not slow it down, but I don't have a Roban, so I am just making assumptions).

If this is the case then the ratio between the main and tail rotor should be 13.8 / 1.15 = 12:1 ratio, so whatever headspeed you choose should give you a tail speed of 12x the chosen headspeed.

So, if your chosen headspeed is 1200rpm, then the tail speed would be 1200 x 12 = 14400rpm.

Bear in mind that scale helis do not require anywhere near the power and amps of a 3D heli, so it an 850 sized motor may be overkill. I don't have a fenestron heli and I am aware that they are more power hungry than a standard tail rotor.

For comparison, my Baumann EC-145 is 4x 820mm main blades, and 2x 150mm x 41mm tail blades. I use a XNova 4035-300kV motor, 12s and Castle Edge 80HV ESC. It typically flies FF using about 1000W or 23A. Hovering is about 15-20% higher power, and peaks are around 1700W / 38A.

At a guess I would think that a similar model with a fenestron may use 25-30% more power, and your Roban is a bit smaller than my Baumann, so I would guess that you may need around 1300W to fly gentle FF, which is well within a 4035 motor's capability. Perhaps look at something like XNova 4035-480kV - it pushes out 3800W continuous which should be plenty I would think.

http://www.xnovamotors.com/xnova-4035-480kv/

The 120A Kontroniks is MORE than enough for the job - I would think that an 80A would be enough, but it may not have the features you want ?

ColinVario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )
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03-30-2017 01:23 PM  32 months ago
0Post 27
jwest

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cincinnati ohio

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Thanks Andy! Yes....I mislabeled the gears on the tail. Reverse what I said.

I don't mind having an overkill on the equipment. I guess my philosophy is that if you don't work it too hard, then maybe it will last longer or break less. Plus I already have the 850 490Kv.

So you think a head speed of 1280 is too high? I am definitely a noob to this but I thought that would be on the low end. I am open to a lower head speed but I want to make sure I keep the fenstron at around 14k to 15k. Roban seems to imply this as an optimal rpm for an effective yaw response.

Do you think setting a head speed at 1200 would be ok to start?
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03-30-2017 01:29 PM  32 months ago
0Post 28
jwest

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cincinnati ohio

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Where can I buy and price out the Baumann EC-145? The website shows the details but nothing about price.

I want to do a 145 next. My hospital uses the 145 for air care and I would like to replicate it.
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03-30-2017 09:48 PM  32 months ago
0Post 29
donnie170

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troy, AL.

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From what I understand 1200 rpm is the number to shoot for. The Europeans have had the kits available for a A little while longer than we have in the states so they have had time to get A few of them in the air. I have been told some of the machines have 80+ flights on them so far with no problems. Also the tail servo needs to be very strong I think it was around 300 ounces of torque.
I've got one test flight on one of mine so far and gathering the pieces to put the other one together now.

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03-30-2017 10:21 PM  32 months ago
0Post 30
jwest

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cincinnati ohio

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300oz on the tail... wow! What servos do you have on the cyclic and tail?
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03-30-2017 10:45 PM  32 months ago
0Post 31
donnie170

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troy, AL.

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I'm using OMG20's on both cyclic and the tail for now, not too happy with the tail at the moment I plan on doing more testing this weekend.
I have been told a minimum of 20kg torque for the tail if I did the conversion correctly its about 280 inches of torque. I'm going to find a better servo for the tail and I will let you know what I end up with.
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03-31-2017 01:30 AM  32 months ago
0Post 32
TailKiller

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Panama City, FL

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That Shand's heli is sharp.. My nephew's apartment looks right into the hangers and he watch it get built on site in Gainsville.Dennis
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03-31-2017 03:31 AM  32 months ago
0Post 33
MarkH

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Gilbert, AZ

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1200-1250 head speed and a 500-550 kV motor are what's working for numerous completions in Germany. The gearing for the fenestron is the reason for the higher kV motor requirement. Roban instructions are somewhat standard for all their kits and not quite complete.
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04-01-2017 09:40 AM  32 months ago
0Post 34
Andy01

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Brisbane, Australia

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Did you look at the Baumann website ? All prices etc on there - 1090 CHF for the EC-145 fuselage.

http://www.modellhubschrauber.ch/Fu...g&t=4&c=46&p=46

I run my 4x 600mm Seahawk at 1350rpm, and the 4x 820mm EC-145 at 1050rpm, so yes I do think that 1280rpm would be too high for a 4x 700mm heli. I would start at 1200rpm, and see if that could be dropped to 1150rpm and still have good tail authority.

ColinVario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )
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04-30-2017 04:59 AM  31 months ago
0Post 35
JestRR

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Florence, Oregon

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jwest....
One thing I'm gonna tell you before you do a whole lot to the fuse is to thin CA all the joints in the wood work! most every Roban heli needs to have them glued in much better than what comes from the factory. I used 1/4 bottle on mine.Mike Spinner
Florence OR
SCALE JUNKIE!!
NORTHWEST SCALEWORKS
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04-30-2017 03:09 PM  31 months ago
0Post 36
eiichivr

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tamano.okayama,japan

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EC 135, it is big.
I visited HAJIME - FACTORY on April 22. I practiced with my colleagues. HAJIME was also assembling the white of EC 135. They will decide the adjustment and color from now.

I am working on Japanese translation of the assembly manual into Japanese at their request. Helicopter flight is a beginner.

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05-18-2017 03:01 AM  31 months ago
0Post 37
swampd20155

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Gainesville, FL

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ShandsCair 2
Hey, guys!

I, too, recently acquired a Roban EC-135. I'm fairly impressed with the overall fiberglass work and paint, but not so much with the interior details. Seeing lots of places where glass clean-up needed and would it take so much to seal the wood floor and cockpit console before painting? However, considering how much work has been done for me I won't complain too much. I won't plan to make this a true showpiece, but hoping it will turn out reasonably well.

I have a question for all you electric power gurus. This is my first high-power electric - have had 450 size helis, but nothing like this! - and am wondering about the power system I've chosen, based on what I've read here. I have a Garrt 4500W, 530KV motor and a Castle Talon 120HB. This system will take a 12S battery, but I'm beginning to think I might be better off with a 10S battery? 10 x 3.7 x 530 x .90 / 13.8 = 1279 RPM. Which means to get to the target head speed of 1200 RPM I'd have to set the governor to 94%. With a 12S battery: 12 x 3.7 x 530 x .90 / 13.8 = 1535 RPM, which requires setting the governor to 78%. So, I guess my question is: is the ESC happier with the higher governor setting, if the current draw remains conservatively within its spec? Or is it happier at a lower governor setting and lower current?

Any help will be greatly appreciated!

MarshBeating the air into submission...
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05-18-2017 05:56 AM  31 months ago
0Post 38
goodhunting

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Slovenia ... somewhere in Europe

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CC ESC's are usually happier with 90% (+/-5%)settings.
78% is not bad... but 94% is better IMHO.

If you already have the 12S batteries... test fly it first. Set up the CC GOV at 80% (and one FM at 85%) and see how the helicopter behaves. Sometimes these fenestron driven tails have a story of their own...

gh
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05-18-2017 06:43 AM  31 months ago
0Post 39
DennisH

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Baton Rouge Louisiana USA

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Great looking Bird, keep us updated.
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05-18-2017 09:36 AM  31 months ago
0Post 40
Andy01

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Brisbane, Australia

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If the Talon ESCs are anything like the Ice/Edge ESCs, I suspect you may have a problem with 78%.

If you lived in Canada, you might get away with it, but Florida, probably not.

If you have several 12s packs, it might be cheaper to buy a more appropriate motor (and sell the current motor) than new flight packs at 10s, but as said above try it first - you might get lucky.

ColinVario Long Ranger 700e
Seahawk 600
UH-1N 500
Baumann EC-145 800+ (coming soon )
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Home › Scale › ✈️Aircraft › Scale Heli › Roban Scale Helicopters › Just Picked up a Roban EC-135
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