Thread: Discussion Walkera 4F200 3 blade head
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Old Dec 17, 2010, 09:23 PM
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Originally Posted by zadaw View Post
I had a blade stike today while trying to take off. A couple of servos were stripped in addition to the damaged blades.

I find it very easy to trip over when trying to take off? Can you tell me what is the best way to take off? Do you open the throttle gradually or do you yank it up suddenly at one stage?

I wasn't facing the wind today and this was probably a big mistake, although the wind was relatively mild.
Hi zadaw,

Sorry to hear about the blade strike. One thing that hasn't been mentioned yet is throttle and pitch curves. Seems like somewhere along the way, my curves were messed up, and it caused the heli to be hard to take off and land. You might try messing with the 'hov p' and 'hov t' to see if it's better, then adjust your curves accordingly. For example, what if you don't have enough head speed at take off, or not enough headspeed for the corresponding pitch?

To answer your question, I let it spool up, similar to what ri0grand described, then I'll usually let it float off the ground, without a dramatic punch. I know people have advised against it, but I'll let it sit a few inches off the ground for a bit sometimes, then slowly climb out. It seems to handle it just fine.

People have talked about an unlevel swash, so I'd like to try to take another shot at describing my method for a level swash and good tracking blades. I came up with this all on my own, so please let me know if I'm messing something up, or can add to it:
1. Take a pitch gauge, and attach a level to the top of it. I happen to use the orange and blue pitch gauge that Wow sells, and I like it because you use the knob on the gauge to finely adjust the gauge, not just hold it in place, like some other pitch gauges I've seen/used. It also goes up to +/- 15 degrees. The level I found is from Home Depot. See pic.
2. I was taught to set your throttle hold pitch curve to be the same as your idle-up pitch curve, (at least at the hover point) which might be the same as your normal pitch curve (at least the upper half, or course). I've also used the method taught to me by dkfuji, and Finless Bob, which is to set up your pitch curves so that you've got zero degrees pitch at mid-stick.
3. Flip the little switch on the rx to the 'adj' position, bind the heli. Flip it to throttle hold. Given everything described in step 2, you should have the same pitch curves as you are using, with no throttle.
4. Carefully set the throttle to mid stick, which should, in theory, be zero degrees.
5. Pick one blade to start with, and set your pitch gauge up to it.
6. Line up the swash so that the three posts on the rotating part of the swash line up with the three stationary posts. Note the position of the blade with the pitch gauge on it, and figure out which servo your blade is lining up to (E, A, or P).
7. Note the pitch that the blade is sitting at while lined up to that servo, making sure that the blade is lined up as well as possible with the blade grip (to simulate flying position).
8. Rotate the rotor 120 degrees CW, and your blade, or at least it's post on the swash, should be lined up with the next servo. Note the blade pitch again.
9. Rotate the rotor another 120 degrees, now you should be lined up with the last servo. Note the pitch again.
In a perfect world, your readings would be zero degrees at each of the 3 positions, and your servo arms would all be right at 90 degrees.
Even if your readings are something other than zero, they should all be consistent. If they are, your swash is level. If they are not, adjust the servo-to-swash links until all 3 pitch measurements are the same. It stands to reason that if the pitch measurement taken on the same blade, at three different positions in the rotor rotation, is all the same, then the pitch must be the same throughout the entire rotation--meaning that the swash is level.
10. Once your three readings are consistent, then adjust the swash-to-bladegrip link so that you have zero pitch at mid-stick (or whatever pitch you want at whatever throttle position).
11. Once that blade is turning true, move your pitch gauge to another blade, and adjust the swash-to-bladegrip link of that blade to match whatever pitch reference you just used on the last blade.
12. Once the second blade is turning true, repeat the process to the third blade.
13. Once you are done and the heli is disconnected, be sure to flip that little switch on the rx back to the 'wk' position before flight, as I hear it will certainly flip over on take off if left in the 'adj' position.

If all blades are balanced and everything else is in zen, this should get it done. This would also be a good time to check your total (min/max) pitch.

I just did all of this to my heli last night, in addition to replacement all 6 links and a new belt (after almost 45 flights). The old belt was still running fine, but I could certainly observe the wear with a new belt sitting right next to it. She flew four good packs this morning--knock on wood.

I'm not sure if it's aging batteries or maybe an aging motor, or maybe the heavy blades, but I can tell that it's not quite as punchy as it used to be, and I keep bringing my throttle curves up slowly. How long does one expect a motor to last, btw? Happy Friday,

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