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Old Oct 21, 2009, 11:44 AM
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Moorpark, Ca.
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Help with Blade-400 / DX-7 set-up

Iím looking for some information on setting up my Blade-400 to my DX-7. Iíve flown fixed wing for many years. Wanted to try a heli and have been able to teach myself much of the basics of heli flying with my real-flight 3.5 & a honeybee fixed pitch single rotor. I picked up a B-400 and DX-7 from an RCGer. The Tx was already set up for the heli by the previous owner. I have no idea of the previous ownersí ability or how he flew the heli. Iíve since just been flying her using the ĎNormalí mode. And have probably put 25 or 30 packs through her with just a few minor mishaps. Iím able to hover tail in, out, left & right, and do basic easy FF, figure 8s, albeit sometimes a bit sloppy and not symmetrical, (Iím a beginner heli pilot remember?) Iím seeking information on running the heli in idle up mode. How do I transition from ĎNormalí mode to ĎIdle upí mode and back? And, what values should be entered for throttle curve & pitch curves, taking into account my newbee status & wanting, at this point, to just do basic FF maneuvers and start to get a feel for a bit more performance oriented flying. I have a DX-7 manual and can generally follow set up instructions as I have set up several Txs for my fixed wing aircraft. What isnít covered in the manual is, what these throttle and pitch curve values mean, and what effect on the heli does changing these values have? Also not covered is the above mentioned transition in & out of idle up mode. Thanks for any help

Rick
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Old Oct 21, 2009, 12:59 PM
QiW
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south east asia
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lots of info here ... http://www.helifreak.com/showthread.php?t=41692
just clik on the one relevant to what u wanna know ... pretty clear and easy to understand videos
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Old Oct 21, 2009, 01:29 PM
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Thanks QiW! Lots of info!! Lots of reading to do.

Rick
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Old Oct 21, 2009, 04:22 PM
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Wow lots of good questions there... they are not specific to Blade 400, but 3D helis in general. You might be able to learn a bit more from this...

http://www.rchelicopterfun.com/rc-he...-controls.html

I'm not a fan of the advice on that site, but there is a good definition and explanation of the concepts.
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Old Oct 22, 2009, 12:52 PM
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Thanks Jasmine,
I agree with you with the definitions and concepts being very well presented and clear, but do not necessarally agree with some of the opinions. The info did not however tie together the concepts of flight with the actual set-up on a modern day Tx. Although as you mention, my questions are not B-400 specific, would certainly be infomative if not down right helpful to many if/when I find the answers. Thanks for the link. It's worth the read.

Rick
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Old Oct 22, 2009, 02:11 PM
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MikeyToo's Avatar
Brandenburg, KY, USA
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While snooping around on the interwebs I found this video:

http://www.horizonhobby.com/Articles...ArticleID=1907

E-flite/Horizon has put out a "beginner setting" for the DX6i/Blade 400 combination. They modify the throttle curve for higher headspeed, reduce max pitch, and add expo on all the axes. I'm plugging them into my DX7 to try and thought you might be interested. I've used both radios and the settings seem to line up.

None of this really explains the why, but it does give you a point to start from. The original settings on the DX6i were a lot more generic.
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Old Oct 22, 2009, 02:12 PM
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Sorry about that... I was too busy to post a personally-written answer. I know I've posted on this subject before, as have many others. If I remember, I'll try to come back later tonight and write something.
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Old Oct 22, 2009, 03:29 PM
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Thanks for the link Mikey. I'll definately check it out when I get home this eve.

Jasmine, I hope I didn't sound ungreatful. To the contrary, your willingness to take your time to help others is far and beyond generous! The fact that my specific questions weren't completly answered in the link is the fault of no one, and the contents were, as you correctly assumed, very relevent and informative, and, greatly appreciated!

PS. I watched your flight sim video yesterday & it was very helpful also. I took the B-400 out last night after work and found myself trying to make those smooth coordinated figure 8 turns you demonstrated. Mostely unsuccsessful as I found myself having to play catch-up with the tail near the end of the turn, but got a couple of them right. Practice practice... Thanks again.

Rick
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Old Oct 22, 2009, 05:16 PM
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Yeah practice is a funny thing. I often find myself coming out of turns and flying a bit sideways, but still under control. Often this doesn't become apparent until I do a loop and it comes out a big corkscrew
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Old Oct 23, 2009, 01:05 AM
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Ok, what isn't explained in the manual is what the pitch curve x-axis means. On the bottom you have "L-1-2-3-H" - those represent stick positions - Low=0%, 1=25%, 2=50%, 3=75%, and High=100% - the pitch curve allows you to set how much of the total collective pitch the helicopter will use at each stick position, and the computer interpolates the points in between. So, let's say you have -10 to +10 degrees of pitch available on your helicopter... this is what you can get with a pitch curve. Table relates stick position number to stick position value, to pitch percentage, to actual pitch degrees, in that order...

L => 0% stick => 0% pitch => -10 degrees
1 => 25% stick => 25% pitch => -5 degrees
2 => 50% stick => 50% pitch => 0 degrees
3 => 75% stick => 75% pitch => +5 degrees
H => 100% stick => 100% pitch => +10 degrees

This would be a typical pitch curve for idle-up setting - it gives you a smooth transition of collective pitch going from the most extreme negative pitch with the stick all the way down, to the most extreme positive pitch with the stick all the way up. This is commonly written as a "0-25-50-75-100 pitch curve"

Now, in a full scale helicopter, you fly with both hands and both feet... but on a RC helicopter, you don't have feet controls, so we have to control an extra thing with the 4 control axes we have available. Turns out the best way to do this is to control throttle and collective pitch using one axis - the left side vertical axis, which we call the throttle stick, or collective stick depending on the subject at hand. This means you need some way to relate a given stick position to both a throttle value, and a collective value, both at the same time. So, in all flight modes, you must program both a pitch curve as above, and a matching throttle curve. The principle is the same... you simply relate some key stick positions to actual throttle values, and the computer interpolates the points in between. So a typical throttle curve might be...

L => 0% stick => 0% throttle
1 => 25% stick => 60% throttle
2 => 50% stick => 80% throttle
3 => 75% stick => 90% throttle
H => 100% stick => 100% throttle

This would be a good throttle curve for a 400-class helicopter flying in the "normal mode" - as you can see, the throttle itself goes up faster than the stick positions, and this is good because it means we can have the appropriate amount of throttle when we are flying. So now, if I show the typical pitch curve and throttle curve together, you should be able to see how this allows good flying ability by linking two controls to one stick.

L => 0% stick => 0% throttle => 40% pitch => -2 degrees
1 => 25% stick => 60% throttle => 45% pitch => -1 degrees
2 => 50% stick => 80% throttle => 50% pitch => 0 degrees
3 => 75% stick => 90% throttle => 75% pitch => +5 degrees
H => 100% stick => 100% throttle => 100% pitch => +10 degrees

Helicopters don't fly too good if the throttle is varying a lot, but helicopters need to vary upward/downward force of the rotor disk quite a bit - with fixed-pitch helicopters the only way to do this is by changing the throttle, but with collective pitch helicopters we have a much better and faster way of varying the force that the rotor disk is giving - by varying the collective pitch, which happens much faster than a throttle change. This is a major reason why CP helicopters fly so much better than FP helicopters, and it makes very precise flying possible. The rotor disk can almost instantly change the amount of force it is giving - it can change as fast as the servos can move.

So, what you get with the pitch and throttle curves listed above for normal mode, is as you start to move the stick up, the head speed gets high right away and you still have negative pitch, so you don't take off. When you get the stick half way up, you have 80% throttle and zero collective pitch, which actually will give you a little bit of lift on most helicopters. When you start to get above there, you start to get positive collective pitch on the blades (not too much) and super high head speed - so that at about 60-65% stick, you should have enough lift to hover. The collective pitch rises rapidly as you move the stick up, but you have lots of throttle available, so as the pitch increases, the increased drag on the blades won't make the head speed drop. In addition, as you come in for a landing, when you get down around 50% stick, you still have plenty of head speed in case the helicopter is dropping too fast - you can instantly have more lift, rather than having to wait for the motor to come back up to speed. This is the primary issue with FP helicopters - when you lower the throttle to reduce lift, it can take a long time to increase the lift again, particularly if the helicopter is falling.

If you want to do stunts, it is desirable to have lots of negative pitch available, but you don't want the blades to stop spinning, so you use a different throttle curve and pitch curve, so that you have both power and pitch available when you want to go negative. A typical throttle curve for stunt mode is 100-90-80-90-100, with the pitch curve mentioned above. This makes it so that in the center with zero pitch, you have 80% throttle, but as you move away from there and the pitch increases, you get extra throttle to compensate for the extra drag on the blades, whether you go positive or negative collective. For electric helicopters, it is practical and popular to simply run 100% throttle all the way across... so, a 100-100-100-100-100 throttle curve. I usually say I'm running a "balls to the wall throttle curve" - and in that mode, the only way to vary the force of the rotor disk is with pitch changes, and as I mentioned before, this happens almost instantly - allowing tic-tocks and other 3D moves. A side effect of this is that since the motor output isn't changing very much, the anti-torque tail rotor doesn't have as much work to do, and you get much better heading control. This is why I recommend learning to fly in idle-up mode, even for rank beginners.

Does that make any sense? Let me know if you have questions, because I think I'll post that on my blog.
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Old Oct 23, 2009, 08:32 AM
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And then to really gum up the works, you can have an ESC with a governor mode. The idea for this is that it keeps the headspeed constant regardless of pitch setting.

On a real heli, you control throttle and collective pitch with the collective stick. Move the stick up and down and you change pitch, twist the grip like a motorcycle and you change throttle. As you change collective pitch load you compensate with more or less engine power to keep the RPM on the head constant. In the RC world we perform the same function by overlapping the pitch and throttle curves - more pitch, more throttle. But this is only an approximation. A good governor ESC can match them much more closely.

I finished plugging in those settings last night and I'd say they're not just for noobs. Ok, the decreased pitch in the swash mix, the expo and d/r are definitely noob settings, but they run the headspeed up in both normal and idle up, which isn't a bad idea, unless you're allergic to high headspeeds.
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Old Oct 23, 2009, 10:55 AM
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WOW!! What a fine explanation Jasmine. Thank you so much for giving something you can never get back. Your time! So real quick, let me do a quick explanation using the table that Mikey linked us to and written out like your example and assuming a -10 deg. to +10 deg. amount of collective pitch. We'll see if the light bulb is burning bright or if I'm still in the shadows. The curves recommended by e-flight, are like this;

L=>0% stick => 0% throttle => 35% pitch => -3 deg.
1=>25% stick => 42.5% throttle => 42.5% pitch => -1.5 deg.
2=>50% stick => 60% throttle => 50% pitch => 0 deg.
3=>75% stick => 80% throttle => 75% pitch => +5 deg.
H=>100% stick => 100% throttle => 100% pitch => +10 deg.

If my calculations are correct, it would appear that these settings are a slight bit more conservetive than the ones in your example not taking into account any D/R or expo??? Am I getting it?? Thank you both for your efforts.

Rick
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Old Oct 23, 2009, 11:42 AM
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Brandenburg, KY, USA
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Quote:
Originally Posted by RickAvery
If my calculations are correct, it would appear that these settings are a slight bit more conservetive than the ones in your example not taking into account any D/R or expo??? Am I getting it?? Thank you both for your efforts.
Rick
Considering that they're supposed to be "beginner" settings they would tend to be more on the conservative side.

If you wanted to prove your calculations, you could do so easily. Disconnect the ESC, power up the DX and heli, put a pitch gauge on one blade, go to the throttle curve display on the TX and check the pitch at each of the throttle points.
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Old Oct 23, 2009, 01:10 PM
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Moorpark, Ca.
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Thanks Mikey,
As the heli set up drill is new to me, a pitch gage is not yet in my posession. I did order one on Tues. so I expect it any day. I will try out your suggestion above. Thanks!!

Rick
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Old Oct 23, 2009, 01:30 PM
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Quote:
Originally Posted by RickAvery
WOW!! What a fine explanation Jasmine. Thank you so much for giving something you can never get back. Your time! So real quick, let me do a quick explanation using the table that Mikey linked us to and written out like your example and assuming a -10 deg. to +10 deg. amount of collective pitch. We'll see if the light bulb is burning bright or if I'm still in the shadows. The curves recommended by e-flight, are like this;

L=>0% stick => 0% throttle => 35% pitch => -3 deg.
1=>25% stick => 42.5% throttle => 42.5% pitch => -1.5 deg.
2=>50% stick => 60% throttle => 50% pitch => 0 deg.
3=>75% stick => 80% throttle => 75% pitch => +5 deg.
H=>100% stick => 100% throttle => 100% pitch => +10 deg.

If my calculations are correct, it would appear that these settings are a slight bit more conservetive than the ones in your example not taking into account any D/R or expo??? Am I getting it?? Thank you both for your efforts.

Rick
Yeah I think the pitch numbers are ok - 35% is 15% less than 50%, and that means you'll get 30% of the available pitch, so -3 degrees is right. In the settings above, the throttle isn't as high as I like it, but it would probably work ok. Personally, I like the throttle really high, or use a governor to keep the head speed constant (and fast). The problem isn't necessarily the actual head speed, it's the huge variation in head speed that leads to issues such as a mushy feel on the collective which leads to 'bouncing' and the changes in the torque, which leads to bad gyro behavior - something that the Blade 400 is very prone to do.
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