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Old Jul 10, 2015, 10:28 AM
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Question
Head speed & Collective for 450 size, MD500

Newbie in scale helicopter, so looking for some advise from anyone experienced with this configuration.

-Trex 450 pro (2 blades) with MD500 scale.

My question is;

-What is the suitable Head speed and collective pitch?
-How to know that the head speed and collective is match?


Thanks for any help.
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Old Jul 10, 2015, 12:42 PM
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A good speed to start would be somewhere in the range of 2200 to 2500 rpm for a two blade head. That is fairly easy to get with a change in motor and maybe the pinion. Pitch does not change from 3D as it will still be in the range of 11 to 13 degrees. What should change is the amount of cyclic movement. That can easily be reduced to 6 or 7 degrees and that is changed by the swash mix setting. As for the gearing, if you have the 121 tooth main, then the 12 tooth pinion with a 2500 to 2600kv motor will work just fine on 3s. For 6s, then a 1250 to 1300kv motor will give the same results.

When working with the 150 tooth main, a 15t pinion will give the same results with the 2500 to 2600kv motor. There are only two choices for main gears, one is the old standby and the other is the one found on the newest versions. No matter what, your head speed, when kept to those rough limits, will not create as much body resonance and should keep unwanted vibrations from setting up. 450's in scale bodies are notorious for vibrations that get the body dancing across the ground and the usual suspect is very high rotor rpms. Hope this helps.

Don
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Old Jul 10, 2015, 04:59 PM
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Yup... we had perfectly acceptable results with 2200 RPM on the head.

But we used 12T pinion on 150 maingear, and the standard 3500 kV motor on 3S.

You might want to try asymetric blades, to get a bit more flight time out of your battery.

Brgds, Bert
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Old Jul 16, 2015, 08:24 AM
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Quote:
Originally Posted by Brutus1967 View Post
Yup... we had perfectly acceptable results with 2200 RPM on the head.

But we used 12T pinion on 150 maingear, and the standard 3500 kV motor on 3S.

You might want to try asymetric blades, to get a bit more flight time out of your battery.

Brgds, Bert

We calculated head speed for 12T pinion, 150t main gear and 3500 kv motor at 100% throttle the result is 2700 RPM. How do you get 2200 RPM with this setup? please advise..
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Old Jul 16, 2015, 08:25 AM
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Originally Posted by Keyrigger View Post
A good speed to start would be somewhere in the range of 2200 to 2500 rpm for a two blade head. That is fairly easy to get with a change in motor and maybe the pinion. Pitch does not change from 3D as it will still be in the range of 11 to 13 degrees. What should change is the amount of cyclic movement. That can easily be reduced to 6 or 7 degrees and that is changed by the swash mix setting. As for the gearing, if you have the 121 tooth main, then the 12 tooth pinion with a 2500 to 2600kv motor will work just fine on 3s. For 6s, then a 1250 to 1300kv motor will give the same results.

When working with the 150 tooth main, a 15t pinion will give the same results with the 2500 to 2600kv motor. There are only two choices for main gears, one is the old standby and the other is the one found on the newest versions. No matter what, your head speed, when kept to those rough limits, will not create as much body resonance and should keep unwanted vibrations from setting up. 450's in scale bodies are notorious for vibrations that get the body dancing across the ground and the usual suspect is very high rotor rpms. Hope this helps.

Don
Thanks a lot Keyrigger, Very useful info.
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Old Jul 16, 2015, 12:21 PM
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What I would recommend is to purchase an ESC that has governor capability. Some flybarless controllers now can be used as a governor but you will need to still purchase an RPM sensor like those from Eagle Tree. You can also set the RPM with a tachometer for somewhere around 92% of full head speed so that you keep a constant speed over the course of the flight and that also prolongs the battery life in the air. I don't have a governor setup right now on my small helicopters (they see very little airtime) but my larger helicopters are all governed. There are also speed controllers from the past that had helicopter modes as part of the programming you did when you set them up. I use a Kontronik Jazz 55A speed controller in my Logo 5003D and it has an automatic governor that when I set a flat line throttle curve, it immediately goes into governor mode and holds the motor at that RPM setting. It is very good but no longer in production however, a slightly smaller version of the Jazz might be found used and that would fit into a 450 size scale setup. Just for good measure, you can find two Castle Creations ESC's that will work for you nicely. One is the Edge Lite 50 (smallest they make in that series) and the other is the Talon 35. Both have built-in governor systems but you do need to purchase a Castle Link USB adaptor. Those adaptors are inexpensive and well worth the cost. Hope this helps.

Don
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Old Dec 23, 2015, 09:53 PM
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Now, completed my MD500 with 4 blade rotor head. Final configuration is Align motor rewind to 2500kv with 14t and HBW V3 50A run with GOV store mode. Very nice and smooth flight.

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in this VDO, the motor still 3500kv and 35A ESC but for final config. no any difference except i can run at lower head speed and Temp at ESC and motor has reduce 10-30 c.
MD 500, 4 Blade 450 size FULL FLIGHT 1-1/2 (2 min 0 sec)


MD 500, 4 Blade 450 Size FULL FLIGHT 1-2/2 (1 min 36 sec)
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Old Dec 24, 2015, 12:20 AM
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Nice!! Love the looks and sound. I am just getting started on a MD500 fuse on my Blade 450 3D.

As a silly question, why can't you just combine your throttle and pitch curves to give you the desired RPM's? Is it because the motor might not have developed enough torque at a lower head speed?
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Old Dec 24, 2015, 12:47 AM
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Originally Posted by HeliFlyer14 View Post
Nice!! Love the looks and sound. I am just getting started on a MD500 fuse on my Blade 450 3D.

As a silly question, why can't you just combine your throttle and pitch curves to give you the desired RPM's? Is it because the motor might not have developed enough torque at a lower head speed?
We rewinding the Align 3500kv motor down to 2500kv (special made: low kv, low power consumption but more torque than original motor) because of i need more torque in low rpm condition (for my opinion, Scale flight should be run at low RPM as much as possible but the heli must be stable and easy to control)

With original 3500kv you can reduce RPM to desire RPM by change the pinion or adjust TH curve but it still less torque and more power consumption when compared to rewinding motor (short flight time and more heat at ESC+motor)



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