Thunder tiger mini Titan ARF PRO build

Started by gauravag, January 06, 2010, 09:23:29 AM

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gauravag

Ok, i managed to get the heli to point straight in rate mode, and with no rudder input !
I had to tweak the length of the pushrod to achieve this but i think its good now. The servo arm is also perpendicular to the servo/boom.

I got the heli back in HH mode. I am still not too happy here. I get some uncommanded left and right movement, depending upon the gain setting.

If i let the gain too high eg 90-100 i get the heli to move to the right with tail wags ( moves to right with jerks )  and if i set the gain low to something like 20, there is no wag but the heli wants to turn left. In between at 50-60 gain as well the heli does not really stay locked in to one heading. I mean ideally i should not be needing any rudder for the heli to stay in a 1 minute hover, right ?
The rudder trim/subtrim is 0 and revo mix is INH, and all other mixes in radio are off ( except the gyro gain, throttle hold which i enabled ) .

I run out of battery time , since i have only one pack, i get to do this testing for only about 5-6 minutes at a time .

Any ideas ?

anwar

It is possible that it is your thumbs doing it inadvertantly :) 

Adjust your THROTTLE curve so that you can hover without any throttle adjustments (ie, without the heli going up or down) at some throttle stick position, and take your thumb off the left stick completely and see if it still drifts.

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gauravag

I had thought of that !!! When in a hover i moved my hand away from the throttle/rudder stick , even then the heli wanted to turn itself ... :((
I also checked the vibration. but I do not think that is too much ..

anwar

#78
Hmmm. Usually, HH will mask many setup issues.  So I am pretty sure you have missed something in your radio setup or how the heli receiver is wired up. Just need to hunt it down. 

One more suggestion.  When you switch from rate to HH, fully shutdown both the heli and the radio.  Power up the radio again in HH mode, then power the heli back up, wait for it to initialize (3 to 5 seconds) and see if it holds better.
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gauravag

I think its a issue with the gain channel.
When i connect the gyro gain wire to channel 5, and switch the gyro to HH mode using the TX , with any gain amount, and the heli staying on the ground i see a servo creep to the left .
If i try this without the gain wire connected, there is no creep.

Now while flying i have been observing that the heli is wanting to turn to the left in HH mode. This co-relates to the servo creep i am seeing.
Tomorrow morning i will fly without the gain signal wire connected to see how the tail performs...

gauravag

Came across another thing today. I wanted to adjust the End point of the rudder servo, so that the maximum travel on either side does not cause binding.
Now, i switched to rate mode, and adjusted the dial on the gyro (the potentiometer) so that with full left and right inputs the tail pitch slider does not reach the ends.
However, since my tail pitch slider is offset to the right in the neutral position ( as you suggested in order to get the heli to track straight in rate mode without input ) , i need to set the EPA to quite low, to avoid the tail pitch slider going to max right, but what that does is , it does not give full travel to the left. If i adjust the EPA for the left travel, the servo binds when it goes to the right.
I think the EPA should be set differently in both directions. but the gyro doesnt support this ?

Also, i have been downloading and watching the Bob Finless videos, the beginner ones. In one of them ( i think the Gyro setup ), he has said that for tail setup, in rate mode, when the stick and trims are neutral the arm should be perpendicular AND the pitch slider should be exactly centered.

Isnt this contradicting to what we have been trying to do here - get the heli to track straight by giving some right pitch in neutral condition ?


RotorZone

It is normal to have the offset on Raptors. Just set it so that it doesn't bind. Using less of the available travel on one side is not an issue.

anwar

#82
Bob has multiple videos.  There is one where he uses a Telebee gyro, which is a very low end gyro.  If you watch the right ones, you will understand what he is suggesting is the initial setup for HH (set the tail slider perpendicular, use HH and fly). Later, he does clarify that you should set it to rate mode and adjust mechanically, then permanently move to HH and fly. 

About end points, you will typically never go that for the purpose of preventing the slider hitting either end.  People reduce the end points to slow down how fast you can pirouette using the tail.  Whether the tail slider hits either end is prevented by adjusting a "limit" pot on many gyros, and not using end-points in the radio.  On the TG6100M, you should use the "EPA" pot on the gyro to do this.  Most gyros recommend that you use an appropriate hole on the rudder servo arm so that the EPA ends up being around 80% of the maximum available for that pot ("EPA" pot on TG6100M, "limit" pot on many other gyros).
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gauravag

Ok, i hovered today with the Ch5 wire disconnected and the gyro in HH mode and the gain on the pot set to 50. There was a very slight drift to the left. Like 45 degrees in 10 seconds. Is that kind of drift normal ? ( i am new to gyros so may be expecting a lot from them ! )
Funny thing is that with the ch5 wire connected, there is even more drift to the left . I tried the gain on the radio at 30,50,70 but it didnt really help much.
The manual for this gyro doesnt clearly indicate how the Ch5 is used. and i couldnt really locate more information on the internet.
At this point, I think i am going to fly in HH mode, with the ch5 disconnected and move on to practice side hoverings.
I am pretty good with tail in hoverings and have been moving the heli forward-backward .


anwar

#84
No, a HH gyro should not drift that much (at least not in a consistently reproducible manner), without pilot input. Please double check everything, including how well the gyro is mounted (funny things happen if the gyro encounters vibrations, for example if the double side foam/tape used to mount the gyro has gone weak etc).

There are multiple threads online about people using the green wire to fully control the gyro (for both mode and gain settings) remotely from their radios.
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gauravag

Had a crash today. Was trying to hover the heli with its side towards me and man that looked so tough ! I have the tail in hovering very well practised now. I can keep the heli just at one place with barely any stick movement. Also i do forward - stop - backward - stop.
Broke the main blades, the stripped the main gear. Had replacements for both and got it back in the air in 20 minutes :) :)

Lesson learnt - not to be over confident and take things slowly. Will be practicing sideways flight in the sim more before trying out in real.

anwar

Take it easy Gaurav :)

Remember to fly in a large open area, and try any new moves/orientations at a bit of distance from you and at a good height (but not too high or far that you cannot see the heli orientation properly).
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vinay

Gaurav, my suggestions, throw those training yellow balls and use ping pong balls if they can stand the weight. What I noted was that those yellow training balls hold on to the grass etc when lifting off, giving a feeling that the Heli is not trimmed >:D.

gauravag

Vinay,
Somehow i like my training gear, and i think it has saved me a lot of crashes so far.I purposely do not fly off grass just for the reason that when getting into a hover gradually, the training gear catches the grass and spins the heli sometimes.

BTW, as a long term airplane flier, and now just starting helis i notice a few things i am doing, out of habit, but is not well suited to helis :
- When in a even slightly dangerous situation, out of habit, i seem to pull the throttle back. Also i have seen that instinctively i also give in up elevator .
- I need to learn to give 'pure' inputs. Most of the time i have seen that when giving an aileron input i am also giving some up elevator. When practicing hovering, i need to learn to give pure inputs.
- Not so much used to backward flying

I learnt that side hovering needs a lot of practice, and have come back to the sim for that. Somehow on the sim i can do a good nose-in but side hovering is still something where i crash very often. I think this is because i am not used to giving true cyclic inputs yet.


Now one question. I wanted to see if my blades are tracking properly. For that when i get the heli into a hover at eye level, I see the flybar 'disc' clearly, however the main blade disc is not very clearly visible. Its kind of fuzzy. Do you think this means my blades are out of track ? Note that i am using wooden blades and the tips arent painted , they are natural wood color.

RotorZone

Wait till you go back and fly planes. I was cutting throttle (negative pitch in heli) when going inverted :o

Backwards is not as simple as one would think. Backwards when tail is pointed to you is natural flying but doing a full backwards circuit or fig 8 takes some practice. Don't try it on the heli first, try on sim.

Plane flying experience helps too in some cases. I was very comfortable flying FF circuits like a plane. Even nose in attitude, but I couldn't do a nose in hover at that time confidently.

If you cannot see the blades properly try against a different background. They should be in the same plane, not fuzzy. But woodies are sometimes difficult to track, one flight they'll be perfect, next flight they'll be  bit off.

gauravag

Thanks Rajesh.
One question. These wooden blades come with a Thunder Tiger decal, one red and one black. If i put these on top of the blades, would it help to 'see' them track ?
Or would i need to put them on the leading edges to see them ?

anwar

The way we typically use those stickers is to identify which way to change the linkage rod lengths (tighten them or loosen them). 

So you take the heli to eye level hover, and see if you see two separate "disc"s being created by the two blades.  If there is only one disc from both the blades, you are all set.  If there are two separate discs, we need to adjust linkages.  So put the colored tapes on one of the blades to mark it, and hover again at eye level.  This time you should be able to identify which disc is higher and which one is lower.  Adjust accordingly until you have only one disc.

But you can do this without those tapes also. Just note one blade using some *existing* nick/cut/marking on the blade or the blade holder, and adjust by trial and error.

I have also seen people use bigger tapes to balance the blades.
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gauravag

Had a great time today.
Yesterday my parcel from HobbyCity arrived with 3 Turnigy 2200maH 3S Lipo batteries.
They are smaller in size, compared to the Ace Hobby battery i have on the mini  Titan.
As on the website all batteries came with the XT-60 connector, which is what i am using on my heli and charger too.
The batteries were half-charges ( exactly ! ), and after charging, i had 4 battery packs !!

I took my heli to a nearby field, and got a good 10 minute flight from each Turnigy Lipo.
Note that the Ace hobby battery struggles to give me anything above 7 minutes flying . And i am just hovering as yet.

So i did 4 flights today and adhered to tail-in hovering, along with practising tail-in circles, and go-left-stop-go right-stop manoevers. Also tried to do some side hovering, but i need some practice to gain confidence.

I am sure my servo setup/trim/subtrim is not optimally tuned yet, but i will tweak that later, when i have had some practice on this.

At this point, i am just enjoying flying, and plan to go every morning, since the field is barely 2 minute drive away

gauravag

Charged my new Turnigy batteries, and they took in around 2200mAh Wow ! My Ace Hobby batteries were taking in only 1650 mAh . I guess these Turnigy batteries pack in more mAh then what says on their specs.
Now lets see how they fare over a period of regular use.

anwar

Bad idea to discharge them that low.  How many volts was across the packs when you started the recharge ? 

Also, there is some discussion that lipos have also a "break-in" ("conditioning") for longer life by charging at 0.5c for the first few charges, and discharging them only to half the rated mAH (although this is debated).  In any case, too deep a discharge is really bad.
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gauravag

I am not getting them too low. The charger read 10.5 volts when i put them on charge.
The ESC cutoff is set to normal for Lipo, and as soon as the RPM seems to quiver i land the heli.
On my ACE Hobby 2200mAh battery pack, i am regularly using and putting in around 1650 mAh, but on the Turnigy i somehow used around 2100mAh and the voltage still read 10.5V

I will make a note to charge them at .5C for the next few times.

gauravag

I had 4 flights today again. Getting more confidence. Started practicing side hovering too. I think i have it pretty much when the heli faces the right. But when it faces the left then i still cannot give the correct inputs.
I guess practice will make me perfect.

Now i did do some forward flight. Slowly got the heli to go left and then right. Got most of it fine, but need some more practice controlling, when the heli faces the side.

I read on Raptor Technique website to try and practise some easy auto-rotations from 2 feet or so. I will be trying them next time i fly, as i will need to adjust my Throttle hold curve for that. I intend to make the TH curve the same as the one i fly with, and try doing autos from two feet, by just hitting the hold switch.

Now the sad part. I wont be able to fly till next week. got some travelling/work to do. But hopefully will be back very soon and continue learning.

I am tempted to install my RealFlight on my laptop and practice when i get time in-between work/flights.
Now thats called heli-mania in the true sense.





gauravag

Got back today. Hovered the heli this morning. All looks good, but somehow i am still not too happy with the gyro's headlock. I am thinking of swapping this with a HK one to see if its a gyro issue.
Anyways, i should be practicing daily now. Will get some pictures soon as well.

gauravag

Been flying regularly now.
One question i had was, since my last crash, i noted that the hovering time has reduced  from 8-9 mins to 6-7 mins. Now the batteries are fine, since they take a charge of around 1800maH . The motor feels a little hotter than before, so perhaps its something there. The main shaft was changed on the last crash, so that cannot be the culprit.
I think it would be :
- Feathering shaft ( can this cause excessive battery drain ? this was not replaced, but the hovering/flying is normal )
- Tail rotor shaft. I have a hunch this could be a culprit, as though it was not replaced, i have noticed the gyro acting funny sometimes. There is a little vibration on the boom at 20% throttle, but goes away at 50%. What would be the symptoms of a bent tail shaft ?

What else could cause a shortened battery life

Please dont tell me that the bearings have gone :):):)


gauravag

Changed the tail rotor shaft today. Not much difference. Getting the same 6 minutes.
Inspected the belt and tension. All ok.
Now i am doing some forward flights too. Very little though could that make a difference ?