Learning to tweak

[OzarkCopterBum]

Greets,

First off I have a Stinger .30 with OS .37, CP 15%, woodies and everything else stock. One of my biggest stumbling blocks has been the .37 and lack of knowledge with glow engines. All the mechanicals as far as the heli goes I can understand or at least think I do.

I've been concentrating on the engine. I've been running it really rich, so rich that I can barely feel any heat on the backplate. I started leaning out yesterday and got to where I can touch the backplate but not so hot that I can't leave a finger on it. I noticed that the headspeed increased significantly or sounded like it did anyway. It also produced a wobble that wasn't there before I tweaked the needle. I had experienced this before but was due to running way too rich.

I went into my throttle curve and backed it down to 60% at 3/4 and about 75% at full stick. This settled it down but didnt eliminate it "wobble". I then went to the pitch curve and upped it a little from what I was running thinking that more pitch would slow the head even more. I hit at 6 degrees pitch at 3/4 stick. So far this seems to work even though I can still hear a vibe and the tail still shakes a little.

I don't have a tach so I'm just listening to the blades and they seem to be spinning faster than previously. The heli has plenty of lift and is coming off the ground at 3/4 stick and the motor has a nice even hum with no bogging if I throw to full stick in a hover. Also theres a little low end bogging but if I bring it up to 1/2 stick slowly it seems to work better if I let the blades spool up slower.

Question is: Am I going about this right?

[bono1]

Spooling up slow is a good thing. It lets the torque come up slow so the heli does not twist as much. I sent you an email about setting the pitch curve. Sounds like you are on the right track and slowing the head more may help the wobble. Go back into the pitch curve and make it straighter for a smooth transition.
If you can not hold your finger on the backplate that is too hot.
Sam

[DavidH]

Most of the 30 size helis I have been around like to hover with the head turning at least 1600 rpm.
If your turning it less than 1600 that is why the wobble probably appeared all of sudden.

I would think you have been running the motor too rich, now that your leaning it out some. The motor is starting to run cleaner. It may not nessecarily be running faster, but just sounds like it is.

If your using a straight (linear) pitch curve. There is no reason to change the pitch curve any. Just adjust the throttle curve where needed. I would think your using a linear pitch curve, since you say the heli hovers at 3/4 stick.

Don't understand why you have only 75% throttle at full stick. Sounds to me like the throttle linkage is not setup correctly.
Here is an excellent article on setting up the throttle linkage to get the correct geometry that is needed.
http://www.ronlund.com/throttle.htm


David

[OzarkCopterBum]

why you have only 75% throttle at full stick

Linkage is fine. I set it back to 75% in the curve hoping to slow it down a little. As I was leaning it it just seemed too "peppy" and that wobble appeared. Not having a tach I just guessed that I was overspeeding the head and figured backing off on the throttle was the way to cure that.

Still flyin blind...

[OzarkCopterBum]

I got some GREAT airtime yesterday. I was able to set the throttle curve up some. It looks very much like the one pictured at ricks site though I still have the top end at about 90%. If I set it linear or at the default setting I still get a vibe at 3/4 stick running 75% throttle. If I back that down into the 65% area it goes away and flies really solid.

[flyinfool]

OzarkCopterBum,
Is there anyone in your area that has an optical tack to check your headspeed?
I would be really curious to see what speed is causing the vibration.

[OzarkCopterBum]

Not in the immediate area. Theres not even any heli's in the immediate area, hehe.
I may go to a field sunday that might have one and check it.
Again, I'm just guessing as to the headspeed being the source, but if I set the throttle back it flies great and the vibe goes away.

Am I going about this wrong? If it is overspeeding what should I be doing to slow it down?

[flyinfool]

Head speed is a combination of throttle setting, pitch, and weight.
Weight is not realistically adjustable so that leaves pitch and throttle.
I have not yet seen an OS 37 in action so I am not sure if it is going to be on the verge of overpowering a set of 550mm woodies.
Generally you want 100% throttle at full stick and you then add pitch to get your desired rpm.
However, in your case where you have a lot of power available and wood blades you may want to back the max throttle down as you have done.
Since there are no experienced fliers in your area to help out, it may be well worth the expense to get a tach and a friend use it measure and help set up your head speed. I have the Model avionics tach, it is accurate and not too expensive.

[OzarkCopterBum]

Well, I can test that by reseting the throttle curve to default then adding in some more pitch and see if I get the desired results.

[OzarkCopterBum]

Flyingfool:

I got a chance to tach my headspeed. I was hitting 1950 even with the throttle dialed way back to 50%. We fiddled with it and found the sweet spot in between 1650 and 1700 for hovering and have 100% throttle at full stick. I'm pleased as punch that I was able to diagnose a problem and had some idea of how to correct it.

It also turns out I did have some binding in the throttle linkage that I was able to fix and now its one fine hovering heli.

Many Thanks to Keith at Wilsons Hobbies in Kennett, MO and to Mike and Bill at the field for helping me through it!

[WillJames]

Glad to hear you are getting it sorted out Ozark. Sounds to me like you are learning!! :D

Best of luck with continued success!!

[OzarkCopterBum]

Now I know why everyone says to get help if you can. There are SO many variables.
At a certain point everything is done by how the heli acts and how the motor sounds. And as quick as you get something settled, something else comes up.
Coming into the hobby with no previous motor experience or any experience for that matter, has been interesting to say the least. Its alot to digest but something you've got to do if you want to succeed.

[flyinfool]

Now I know why everyone says to get help if you can. There are SO many variables.
You got that right.
That is why I always tell people that even if you need to drive a couple of hundred miles to find help, it's worth it.

Good to see youve made progress, Now that it flies the learning fun starts.