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dinosaur · 03-12-2013, 08:55 PM

I am pretty new to helicopters...I have a TREX 600N which I crash, and I recently built an Embla 450E. I am confused about my head speed on the Embla. The manual states 2100 - 2200 RPM for hovering and 2900 - 3100 for 3D. I can't even get the helicopter off the ground with less than 3000 RPM. I am up to 3450 RPM and it is just starting to fly normally.

So, my question is why do I have to go so high on head speed? I live at about 7000 feet above sea level, so the air is thinner. Is that what is going on?

Also, how high can I safely go on head speed? Thanks for your help.

Dave

kcgraves · 03-13-2013, 05:12 AM

If it is not taking off at that head speed I would check your blade pitch. Not sure what the Embla is suppose to be for pitch, probably in the +10 to +12 range at full stick but it sounds like it is less than that.

Top end depends on motor, pinion, and blades (carbon vs. wood). If it is stock I would stick with the manual at around 3100. But again it depends on what components are in it.

dinosaur · 03-13-2013, 11:39 AM

Good point. The Embla can go +/-16 degrees with the FBL head. I have it set to +/-11 for IU1 and +/-14 for IU2. I have verified the blade pitch many times thinking it must be off, but it is good. I have also checked the head speed with the phone app and it says the RPMs are right on also. Seems to me that the blade pitch, head speed and weight are the only things that would affect take off. That's why I was wondering about the altitude of 7000 ft.

kcgraves · 03-14-2013, 04:54 AM

The altitude could be the issue. Not enough air going through the blades for lift. Where I am it is only 500 feet. Might want to post in the Main Topic forum with a heading about altitude and lift and see if you get any responses.

dinosaur · 03-14-2013, 08:59 AM

Thanks, I will check with some guys from the local heli club about the effects of altitude. I am still wondering what is the max head speed that I could run. What can other 450s run?

kcgraves · 03-15-2013, 07:08 AM

I don't have a 450 anymore but using stock motor, pinion and ESC the headspeed should be around 3000 - 3200.

Do a search for a head speed calculator and enter your values for pinion, main gear, etc. and see what it says the top speed is for what you have. If you are running stock Embla components whatever it says in the manual is probably close to what it will do.

dinosaur · 03-15-2013, 10:39 AM

I went from the stock 12 tooth pinion to 13T to get up to 3450 RPM. I have a 14T and a 15T on their way. I just don't want to have the head fly apart on me.
It looks like other 450s have run up to 3800, although most run lower. I will just take it up slowly and see how it goes.

It is really bugging me though, because I think something is not right with the build. I have been over it many times and I just can't find anything wrong.

Thanks for your suggestions kcgraves.

toyturbo · 03-21-2013, 01:19 PM

5000ft elevation is the problem, the air is very thin up there where you are in Colorado. Professional athletes work-out and train in that kind of atmosphere because it conditions their bodies into developing stronger and more stamina. Good for training, bad for flying helicopters! Just out of curiousity, what do your pitch curves look like?

dinosaur · 03-22-2013, 05:47 AM

I think you are right about the altitude being the culprit. I found this thread to be very informative on the effects of high altitude on RC and full scale aircraft:

https://www.helifreak.com/showthread.php?t=177128

My pitch curves are:

Normal -3/+11
IU1 -5/+11
IU2 -11/+11
IU3 -14/+14

All are zero pitch at mid stick and straight lines from low to mid and mid to high. One person in the linked thread commented about increasing pitch around mid stick to make the heli more flyable.

Anyway, I am installing a larger pinion and I will let you know if it helps.

03-12-2013, 08:55 PM	#1 (permalink)
dinosaur Registered Users Join Date: Mar 2013	What's Up With My Head Speed? I am pretty new to helicopters...I have a TREX 600N which I crash, and I recently built an Embla 450E. I am confused about my head speed on the Embla. The manual states 2100 - 2200 RPM for hovering and 2900 - 3100 for 3D. I can't even get the helicopter off the ground with less than 3000 RPM. I am up to 3450 RPM and it is just starting to fly normally. So, my question is why do I have to go so high on head speed? I live at about 7000 feet above sea level, so the air is thinner. Is that what is going on? Also, how high can I safely go on head speed? Thanks for your help. Dave

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03-13-2013, 05:12 AM	#2 (permalink)
kcgraves Registered Users Join Date: Oct 2008	If it is not taking off at that head speed I would check your blade pitch. Not sure what the Embla is suppose to be for pitch, probably in the +10 to +12 range at full stick but it sounds like it is less than that. Top end depends on motor, pinion, and blades (carbon vs. wood). If it is stock I would stick with the manual at around 3100. But again it depends on what components are in it.

03-13-2013, 11:39 AM	#3 (permalink)
dinosaur Registered Users Thread Starter Join Date: Mar 2013	Good point. The Embla can go +/-16 degrees with the FBL head. I have it set to +/-11 for IU1 and +/-14 for IU2. I have verified the blade pitch many times thinking it must be off, but it is good. I have also checked the head speed with the phone app and it says the RPMs are right on also. Seems to me that the blade pitch, head speed and weight are the only things that would affect take off. That's why I was wondering about the altitude of 7000 ft.

03-14-2013, 04:54 AM	#4 (permalink)
kcgraves Registered Users Join Date: Oct 2008	The altitude could be the issue. Not enough air going through the blades for lift. Where I am it is only 500 feet. Might want to post in the Main Topic forum with a heading about altitude and lift and see if you get any responses.

03-14-2013, 08:59 AM	#5 (permalink)
dinosaur Registered Users Thread Starter Join Date: Mar 2013	Thanks, I will check with some guys from the local heli club about the effects of altitude. I am still wondering what is the max head speed that I could run. What can other 450s run?

03-15-2013, 07:08 AM	#6 (permalink)
kcgraves Registered Users Join Date: Oct 2008	I don't have a 450 anymore but using stock motor, pinion and ESC the headspeed should be around 3000 - 3200. Do a search for a head speed calculator and enter your values for pinion, main gear, etc. and see what it says the top speed is for what you have. If you are running stock Embla components whatever it says in the manual is probably close to what it will do.

03-15-2013, 10:39 AM	#7 (permalink)
dinosaur Registered Users Thread Starter Join Date: Mar 2013	I went from the stock 12 tooth pinion to 13T to get up to 3450 RPM. I have a 14T and a 15T on their way. I just don't want to have the head fly apart on me. It looks like other 450s have run up to 3800, although most run lower. I will just take it up slowly and see how it goes. It is really bugging me though, because I think something is not right with the build. I have been over it many times and I just can't find anything wrong. Thanks for your suggestions kcgraves.

03-21-2013, 01:19 PM	#8 (permalink)
toyturbo Registered Users Join Date: Feb 2006	5000ft elevation is the problem, the air is very thin up there where you are in Colorado. Professional athletes work-out and train in that kind of atmosphere because it conditions their bodies into developing stronger and more stamina. Good for training, bad for flying helicopters! Just out of curiousity, what do your pitch curves look like?

03-22-2013, 05:47 AM	#9 (permalink)
dinosaur Registered Users Thread Starter Join Date: Mar 2013	I think you are right about the altitude being the culprit. I found this thread to be very informative on the effects of high altitude on RC and full scale aircraft: https://www.helifreak.com/showthread.php?t=177128 My pitch curves are: Normal -3/+11 IU1 -5/+11 IU2 -11/+11 IU3 -14/+14 All are zero pitch at mid stick and straight lines from low to mid and mid to high. One person in the linked thread commented about increasing pitch around mid stick to make the heli more flyable. Anyway, I am installing a larger pinion and I will let you know if it helps.

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