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T-REX 450 › Cyclic~~>Throttle Mixing....Anyone?
08-08-2007 02:09 PM  10 years agoPost 1
fastsc92

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NH

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Currently I don't have any mixing set-up on my MX450(Align Motor and ESC). I do however have a Raptor and it has made the world of difference on that bird by mixing 20% on both the elevator and alieron controls.

My questions is, how would I set it up on the electric. On the nitro, I had to use positive and negative values for mixing so that the throttle would open as I moved the right stick in all directions ( right alieron needed negative values, ect..) When I go to set up the mixing on the electric, I just want to make sure that I am also increasing the throttle with stick movements but I need to know that they are going in the right dirrection. This was easily seen on the nitro since you can watch the throttle on the carb. How would I set it up for this, and is it even needed for electrics?

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08-08-2007 02:17 PM  10 years agoPost 2
colsy

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Cambridge, UK

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I tried this on my 450 SE'S, but to get it to work you need to back your idle 'flat-line' throttle curve down to 70/75%, and this dropped the HS too-much.

From memory i mixed +30% ail-thr and ele-thr.

Try it, i didn't like it but you might.

Col.

Only Quote From Experience.

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08-08-2007 02:26 PM  10 years agoPost 3
kingair

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Utah - USA

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Many people use a straight line 100% throttle curve so cyc/throttle mixing wouldn't make any difference. Even without a 100% curve mid throttle is normally so close to 100 the mix wouldn't make much of a difference. It doesn't hurt to give it a try though.

There is a very fine line between "hobby" and "mental illness."

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08-08-2007 06:42 PM  10 years agoPost 4
fergus

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Ireland

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If you have a radio which shows your servo travel on screen you could use this. Just move your stick for elevator or aileron and watch the bar graph for throttle and see if it increases or decreases. If not correct change the mix value to positive or negative as required.

You will need a throttle setting that is low enough to allow for the extra mix without it trying to go over 100%. With some adjustment you could set it to have just hit 100% with full pitch and full cyclic

Depending on the radio you are using the first method is easiest. Alternatively you could set a flat pitch curve of zero degrees. Then with a linear throttle curve increase throttle until the rotor just starts to spin -input aileron or elevator to see if the headspeed increases or decreases. When satisfied the direction is right revert back to your normal pitch and throttle curves.

Regards

Fergus

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08-08-2007 06:47 PM  10 years agoPost 5
bilbo

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Boston, MA - USA

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Even without a 100% curve mid throttle is normally so close to 100 the mix wouldn't make much of a difference.
I don't find this to be true when trying for a constant head speed. Considerably higher throttle is required to hold a given RPM at 10 degrees pitch than at 0 degrees pitch for exmaple. With my setup I found a curve of about 90-75-90 gave me a constant head speed across the collective pitch range of -10/+10, and then I used cyclic-throttle mixing to get the head speed constant across the cyclic range as well.

Now that I have a Jazz 40-6-18, with a governor mode that works flawlessly, I don't need to mess with throttle curves. But when I was using the Align ESC I was able to get almost constant head speed by using a throttle curve and cyclic-throttle mixing with my DX7 radio. Here is the procedure I went through to set it up.

In my case I'm using an Align 430XL motor with an 11T pinion, and shooting for a head speed of 2650.

First step is to get your head speed close to constant across the collective pitch range, by following these steps:
  1. Start with an flat idle-1 curve of around 80%. It doesn't really matter what you start with. I also disabled the 25% and 75% points on the throttle curve, so I was just using a 3 point curve. You can enable them later if you need to in step 5.
  2. Power up the heli on the ground in idle-1 mode, and then with the collective stick at mid-stick/0 pitch, use a tachometer to adjust the mid-point on the throttle curve until the target RPM is reached. In my case this was 2650 RPM, and about 75% throttle.
  3. Now note the audible pitch of the rotor with the heli sitting on the ground at 0 pitch, and then take off into a full positive pitch climbout.
  4. If you hear the head speed drop during the climbout, land and increase the 100% point on the throttle curve. If the head speed rose, then decrease the 100% throttle point. Repeat the previous step and this step until you can't hear any head speed change between 0 pitch and full positive pitch. In my case the 100% point on the curve ended up at about 90% throttle.
  5. Now let's see if the 75% point on the curve needs to be adjusted. Start with the heli on the ground at 0 pitch, and then lift off into a hover. If the head speed changes, then adjust the 75% point on the throttle curve up or down until you can go from 0 pitch to hover pitch with no change in RPM. In my case just leaving the 75% point inhibited worked fine.
  6. Finally, just copy the >50% side of the throttle curve to the <50% side of the curve, unless you want to test inverted climbouts.
Now you should be able to go through the full range of collective pitch with pretty constant head speed, but large cyclic inputs will still bog the head. The next step I did was to setup two mixes: a aileron->throttle mix, and a elevator->throttle mix. I then experimented by doing stationary flips and rolls at full cyclic until I found the right mix so that the head speed remained constant during flips. In my case both mixes ended up needing to be at about 17%.

This still isn't quite as good as a governor, because it doesn't take into account the speed of the helicopter, so you can still hear the HS changing in a dive or fast descent, but it gets you pretty close to constant head speed, certainly closer than just a flat 100% curve.

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08-09-2007 12:09 AM  10 years agoPost 6
chopperdudes

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Toronto, Ontario, Canada

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but think about it this way. yes a constant hs is what is prefered. however, with a 100% flat throttle curve, you get max power for climbouts at both ends, and your headspeed will boost back up near midstick allowing for better entry into manuevers and unloading the head. it's saved me multiple times when i threw too many moves together and bogged the head and the tail started not holding. by going to midstick in the middle of a flip or roll you'll hear the hs get back up and you'll be out of trouble. it also allows for that little 'bump' when entering without boggin the head down.

mother earth, STOP JUMPING UP AND ROBBING MY WALLET!!!

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08-09-2007 12:13 AM  10 years agoPost 7
MJWS

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Airdrie, AB - Canada

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Yep. Quicker recovery and more energy stored in the head for when we want to apply pitch. On a nitro where we blow up if we crank on it with no load this is a problem. The electrics are great with an almost flat curve.

Mike

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08-09-2007 01:11 AM  10 years agoPost 8
fergus

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Ireland

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The almost flat curve or 100% is fine for wild 3d but for general flying and mild 3d wont you loose out with flight times?

Fergus

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08-09-2007 01:25 AM  10 years agoPost 9
MJWS

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Airdrie, AB - Canada

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Depends on pinion and gearing. You can gear for a lower headspeed and long flight times and still run flat curves.

For mild flight there isn't any significant advantage to running flat curves beyond that they are simple and work well.

Mike

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08-09-2007 09:58 AM  10 years agoPost 10
menace

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Sydney, Australia

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i use 100% thr Flat curve and still use ail-thr and ele-thr mixing to 25% and i can notice the difference when flying without the mixing, it gives the motor that extra boost under load and sends the HS up quicker while executing a maneuver and u come to mid-stick than without the mixing.

its personal choice, but if u can do without the mixing, then your collective maneagement is pretty good...mine is pretty untidy so that is why i mix.

!boo!

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08-09-2007 10:34 AM  10 years agoPost 11
fergus

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Ireland

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If you have throttle set to 100% then how does mixing make a difference? The motor is already flat out before you give cyclic. Where is the extra power coming from??

Fergus

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08-09-2007 03:05 PM  10 years agoPost 12
chopperdudes

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Yeah exactly... how's mixing gonna help when the motor is already working 100%

mother earth, STOP JUMPING UP AND ROBBING MY WALLET!!!

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08-09-2007 04:43 PM  10 years agoPost 13
MJWS

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Heh. Afterburner, BABY. The only way I can see mixes working with a 100% curve is if your endpoints are screwed up and you weren't really getting 100% in the first place. You could do it in gov mode somehow, but it's still the same... you didn't have 100% initially.

You can't 'overdrive' an ESC. At 100% The FETS are just open letting all current flow.

Mike

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08-09-2007 05:22 PM  10 years agoPost 14
fergus

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Ireland

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I really don't see the point in the 100% throttle curve guys. I suppose it depends on your style of flying but with the 100% method the throttle and hence headspeed is crazy around zero stick when the blades are not creating any lift. It slows down for 1/4 and 3/4 stick when you are hovering (But it is still high and therefore twitchy) and when you need the headspeed to stay up during full cyclic deflection it slows down!

I understand the point about the headspeed picking up between manouvers but wouldn't it be better to just have the headspeed constant all the time and use your cyclic throw or flybar settings to adjust roll or flip speed! Hell if the headspeed is too low change the pinion or get a more powerful motor. As I said it depends on your flying style or what you are used too but why not set it up right to begin with and have a more predictable and stable heli?

Fergus

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08-09-2007 05:57 PM  10 years agoPost 15
MJWS

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Airdrie, AB - Canada

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By the time we are considering mixes we are looking for performance. Not stability. Not flight time. Performance comprised of power and agility.

Headspeed doesn't drop noticeably between unloaded and hover on a high power rig with a flat curve. Most of us flying hard have cyclic, and collective completely maxed out. With the lightest paddles and longest flybar. HS is completely constant until we are WAY into the pitch. Agile with maximum available power is the intent.

Predictable and stable is a completely different goal. Even then the torque curve on electrics is so flat that a shallow throttle curve say 100 90 80 90 100 is still the best. Gear it correctly for your desired headspeed. This allows our controller to function far more efficiently.

Remember on a mini there is real torque, all we have is inertia in the blades, and some RPM we can play with. You can't gear it deep, use a nice low curve and try and power it out. There is no significant torque even with 500w and an outrunner.

Edit: I see you have an H2... same principle if you try and flog it you have to rev the crap out of it. Your Joker on the other hand makes enough torque to use more reasonable curves.

Mike

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08-09-2007 06:32 PM  10 years agoPost 16
fergus

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Ireland

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As I said Mike it depends on flying style and your ultimate goal. I meant setting it up 'right' in the context of the question origionally posted in this thread i.e how to go about setting up cyclic - throttle mixing the answer to which does not (in my opinion) involve setting a 100% throttle curve and then setting up mixing on top of it as previously posted in this thread.

As to if its needed or not that is the question you have answered and explained well. I accept for hard 3d on a mini with low torque then a flater curve is better. I remain unconvinced about 100% across the board and then considering collective - cyclic mixing though. The ESC is maxed out as it is. The answer is don't use mixing at all in that instance.

I also don't agree with your own statement that when we are considering mixes we are looking for performance (power and agility)not stability not flight time. I think mixes are there to give a constant headspeed throughout the cyclic and collective pitch range and therefore provide stability. The opposite of what you said. Thats just my opinion for what its worth.

Fergus

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08-09-2007 06:52 PM  10 years agoPost 17
fergus

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Ireland

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Sorry Mike I see you edited your previous post while I was responding too it and your reference to my quote on setting it up "right" has been removed.

Regards

Fergus

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08-09-2007 06:54 PM  10 years agoPost 18
chopperdudes

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Toronto, Ontario, Canada

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remember though, if you use a v-throttle curve and lets say you set it up to 100% at both ends so you'll have as much punchout as possible, and adjust the headspeed so it stays that way even if ur just hovering, you will still bog the motor more when you punch full collective than us with 100% straight. this is because we have more rpm to start with in the first place going into the verticle climb. same goes for cyclic. if ur using a mix, it'll still bog more than that of a straight curve.

as MJWS pointed out, those of use that fly hard will max out collective and cyclic. i go more extreme and max them out independently, so that it'll bind in the corners. but i don't go on the corners so it should be fine. however, if your flying hard and somehow bog the motor, you'll be glad you have a 100% straight throttle. dont' ask how i know

mother earth, STOP JUMPING UP AND ROBBING MY WALLET!!!

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08-09-2007 07:21 PM  10 years agoPost 19
MJWS

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Airdrie, AB - Canada

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Heh. Yeah. Didn't initially notice what you'd been flying, Fergus. For AP or F3C it's all about consistency. On these little guys I mostly beat on em.

I do have one flight condition with more curve to it for messing around and gentle long flight times. Cyclic -> Throttle is there. But if you make a mistake it doesn't recover or pull anything like the flat curves do. That high center lets us recover from a BOG at the maximum possible speed. Absolutely critical when throwing these unforgiving little beasts around down low.

Mike

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T-REX 450 › Cyclic~~>Throttle Mixing....Anyone?
08-09-2007 08:01 PM  10 years ago •• Post 20 ••
fergus

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Ireland

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Absolutely Mike I see what you are saying. The position I am coming from is one where you don't let it bog in the first place. In other words you set up your throttle in such a way that say at +/- 10 degrees pitch you only use 88% throttle then by adding 25% mixing you reach 100% throttle at max cyclic and collective throw. Your headspeed remains constant and you don't bog the motor. You would still use a shallow 'V' curve and keep the throttle up around center stick or zero pitch (as you would do with all electric helis in order to let the ESC perform best). I do appreciate however that for extreme 3D this may not give the desired punch or headspeed required. Im not up to that type of flying ( Yet)!!

Regards

Fergus

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