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T-REX 250 › Back with 250SE tail wag....
06-05-2010 04:00 PM  7 years agoPost 21
neilg.

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north of borston

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knock kock

it's Neil g. chimming in:

anyone mention voltage?

and if this was a kit, did you notice the pictures of what you get are not the same as advertised?

In Nomeni Patri Et Fili Spiritus Sancti

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06-05-2010 06:47 PM  7 years agoPost 22
HarveyR

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France - North

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dizzymarkus, I take note of the idea/offer, if I don't find any solution, I'll be back to it (I'd pay shipping back and forth and any parts needed).

About voltage, I'm on 5Volts (I leave the throttle stick at the bottom at the end of the ESC setuip). What I'm still not sure about are the "Electronic Timing Option" and what "Throttle Response Speed" settings, it seems people don't know there's otherwise I guess I'd get some replies. This is the TREX250SE Super Combo, so it came pre assembled and with all electonics. I've got a s9257 in replacement of the DS420, at first it worked out "ok" (still wagged but better).

I've done another load of tests today with the Robbe 3D Gyro, but no success, exactly the same behaviour as with the GP750, quite amazing two so different gyros have such similar behaviours.

I even tested with no Gyro at all, but there wasn't enough wind... flying in the wind with no gyro isn't that hard (at least with 550mm helies) and it would have been interesting to note any wagging. But no wind so it was too hard to keep control of the tail.

I'm going to set it back up to the best I got : 24mm tail blades (or something) and GP750 and recheck the whole heli (that's why I'd like the exact ESC parameters people are using). In this configuration it is "flyable" but wags quite a bit and has little piro rate.

I'll see how it goes, maybe try to get a video showing the heli in flight so you guys can see what happens with low and high gains.

I remind that an strange point according to me is that it wags even with very low gain (it doesn't hold but it wags). With higher gains it holds and still wags (much faster). I find this special, as in my experience, wagging happens only with too higher gain.

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06-05-2010 08:23 PM  7 years agoPost 23
neilg.

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north of borston

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did you recalibrate your gyro?
is your tail servo on 6v?

i ain't a rocket scientist, and i made my heli work. maybe you should s&*t can the pushrod, if you are using the guides, and go caron fiber like suggested.

In Nomeni Patri Et Fili Spiritus Sancti

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06-05-2010 09:38 PM  7 years agoPost 24
HarveyR

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France - North

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Yes I did recalibrate... I'm not a rocket either, but I have had some experience in 15 years of heli flying, but never really had this kind of problem. Basically it's usually simple, just increase gain until it starts wagging then go back down a little and that's it, I don't think this has ever failed for me. This problem reminds me more of vibration problems. These are a pain because (like my tail wagging) it's sometimes really hard to find what exactly is causing the vibration, you check blades, change shafts, do this, do that and it's still vibrating.

The servo is running the same as the rest (5V). About the mods, dizzymarkus listed quite a few mods to make his work, maybe I'll go that path.

Please: what "Electronic Timing Option" and what "Throttle Response Speed" do you have on the ESC, I'm sure these could have impact ???

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06-05-2010 11:13 PM  7 years agoPost 25
raptor50luvver

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Dorset UK

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Your tail grips are binding 100percent do you know someone else who has a 250 so you can maybe swap them to try

shorter tailblades equals less centrifugal force so less pull on them to lock causing wag

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06-06-2010 08:44 AM  7 years agoPost 26
HarveyR

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France - North

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I'll test today spinning the heli on the workbench (without main blades) to see if the tail pushrod stays smooth. I know it's smooth at rest, I'll see with the motor spinning if the centrifugal force causes the grips to block and make the push rod. I've already tested pulling at them pretty hard and they still seemed smooth, but I'll do this new test whatever.

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06-06-2010 01:27 PM  7 years agoPost 27
neilg.

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north of borston

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i emailed Align . Told them their tail servo is crap in a very dignified manner. Maybe they wil send me a goody. i am going to ask a stupid question in a new topic, might mean something, might not.

In Nomeni Patri Et Fili Spiritus Sancti

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06-06-2010 08:25 PM  7 years agoPost 28
HarveyR

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France - North

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SOME BIG NEWS: I tested spinning the heli on the bench (without main or tail blades), and guess what, the higher the revs, the harder it is to slide the tail pitch slider. When at 90% ESC, it gets pretty hard, too hard for the servo, so it gets jerky. And this is without tail blades, so add the weight of the tail blades and I'm starting to understand why the servo/gyro aren't managing their job very well (and why reducing the weight of the blades by trimming helps a lot).

So, I took the tail grips off to see how it was inside. The bearings are real crap, the inner axis isn't parallel to the outer axis. No joke, there's about 20° between them (on both bearings). By forcing, you can get them back parallel, but you can see there's a problem. So I've decided to try to find some descent bearings to put on it (or some replacement Align ones).

In the meantime I've put it back together and by fiddling about got it kind of free (better than before), and then I tested it, and it's much better, not totally good, but much better. In fact it was so much better that I decided to do some "real" flights. In fact I did three before a crash in a role (my fault, what an idiot).

Not much damage. So, I'll rebuild and get the bearings, and hopefully I'll be able to finish this thread. Thanks to you all for your help, as checking the grips while spinning isn't a habit I have, but I'll add that to my diagnostic tool box. If no one had suggested this, I don't think I would have thought of testing.

neilg, see my reply in other thread. Now, I wonder if the ds420 is that crap, maybe it's the tail bearings/grips that are at cause from the start. Maybe when I get it all straight, I'll test again with the ds420 just to see.

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06-07-2010 12:10 AM  7 years agoPost 29
neilg.

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north of borston

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i was reading about this much debated chinese weight mod: i wonder if dizzy has any comments on it.

In Nomeni Patri Et Fili Spiritus Sancti

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06-07-2010 08:06 AM  7 years agoPost 30
PATRICKLEECE

rrNovice

Fort Wayne, IN

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I'm running all the stock align electronics that came with the SE super combo.. and to my surprise they actually work pretty great! I did have some issues at first with the tail. i had to take my grips off and file down the hub to reduce slop. then after a couple little spills i couldn't get rid of the wag, turns out my tail shaft was just slightly bent. i had never noticed it, was just enough to cause some vibration which lead to the wag. so you may want to replace the tail shaft, if you haven't already. don't give up once you get it up and running, it's an absolute blast to fly!

PATRICKLEECE

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06-07-2010 09:10 PM  7 years agoPost 31
HarveyR

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France - North

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I've ordered the brocken parts + a new tail assembly (Align) just in case the bearings are better in this one.

As I've heard about the chinese weight mod, I took a look on youtube to see what they are about. From what I see these aren't aimed at all at fixing the problem of the bearing not supporting the radial force, in fact, as these put additional weight on the grips, I'd say it makes it worst.

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06-08-2010 01:50 AM  7 years agoPost 32
dizzymarkus

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Oswego, NY

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The weights make the needed force from the servo less to move the tail a certain distance. HemiJoint did an excellant video elsewhere :0) showing just how much the difference was -- IMHO if you have the right servo for the job they are not needed -- but there goes that can of worms hehehe I can currently get my tail to go so fast it blurs and you never know where its going to stop hehehe

You are absolutely right the slop in the grip bearings are riduclas, yet some say its needed. I dont believe that -- some sand down ever so slightly the hub to make the bolt a tighter fit :0) I myself got the Microheli grips (I really dont like MH ) to fix the slop. In my experience the micros like low gain also. Also yes I had the same symptons as you Sir -- raise the gain, it would wag faster -- lower the gain, it would wag slower.

Markus

I reject your reality and substitute my own :0)

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06-09-2010 04:23 PM  7 years agoPost 33
ume

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Switzerland

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I had the same problem with my Trex 250. Check the main drive gear mesh. I did that, and the tail is not wagging anymore.
Hope you cansolve the problem.

urs

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06-10-2010 04:56 PM  7 years agoPost 34
neilg.

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north of borston

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harvey, come out of the workshop and let us know how things are progressing

In Nomeni Patri Et Fili Spiritus Sancti

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06-11-2010 09:35 AM  7 years agoPost 35
HarveyR

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France - North

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Waiting for the parts for the 250SE (should come soon, ordered them Monday from HeliDirect, expect them today or tomorrow). I'll be back about this, and I think it will be OK because the problem is pinpointed (bearings lock when tail revs up). As said, I ordered a replacement Align tail assembly, so I'll have new bearings in case they're better than the ones I have, and if not, I'll go to the bearing shop to order some SKF ones (or other good brand).

ume, did yours also wag whetever gain? wag slow with low gain and fast with high gain? or did it only wag fast with high gain and with slow gain just drift? Because for me this "wag even with lower gain" symptom is specific to the "stiff tail control" problem (whetever is causing this stiffness). Wagging fast with high gain is more related to vibrations or too higher gain setting (different symptom, different problem).

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06-12-2010 02:10 AM  7 years agoPost 36
erick4178

rrNovice

gardena ca usa

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I had this same wag plus i could not set the gain higher then 19 or the tail would go crazy so i changed the tail servo to the Jr ds3500g and put the 760 3g system in and the tail wag is gone

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06-13-2010 03:57 AM  7 years agoPost 37
jbdww

rrElite Veteran

Round Rock, Texas

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I had the same wag and went through the step to fix it. Close to center ball link, big tail servo, carbon rod, chines weights, shorter tail blades, new align tail, etc. The final fix was for sure the micro heli tail, and the heli has been flying perfectly every since.
Joe

Skids Up
http://www.jbdww.com
http://twitter.com/jbdww/

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06-13-2010 06:03 PM  7 years agoPost 38
Moparmyway

rrNovice

NY, NY

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I have posted before, but there is a HUGE amount of slop in the stock Align tail. Just grab both blades and move the servo back and forth by twisting the blades. See the slop between twisting them left compared to twisting them right ?

The MicroHeli tail assy went on (MUST be patient, and lube everything before assy) and solved the exact same problems on mine that you are describing on yours.

See the 4th post from the top.
https://rc.runryder.com/helicopter/...?top=1276448410

Look here for pictures, post #163
http://www.rcuniverse.com/forum/m_9...e_7/key_/tm.htm

I grab the new tail assy and twist both directions, it is as sturdy and slop free as my larger T-Rex's

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06-14-2010 09:33 AM  7 years agoPost 39
HarveyR

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France - North

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Thanks for the links, maybe I'll get one of those tail assemblies, but for my case I'm just about sure now that the problem is to do with the tail grips to hard to turn (change pitch) WHEN the tail is spinning fast. Mine is smooth when stopped. Just have to rev it up to see/feel it get sticky and hard. That's why trimmming the blades helps, because it makes the weight lower, so less centrifugal force, so less locking of the grip. Im my opinion the problems boils down to crap tail grip bearings that can't handle the radial force generated while spinning.

I've received the parts and rebuilt my 250SE and right now it's flying just like it was before the crash, that is "acceptable" compared to what I'd been experiencing the last few weeks (it still wags slightly and I can't push the gain very high, but it's fliable). For now I've decided to just have fun with it and done a few flights around the garden this WE, and it is fun (and hard/interisting to fly in this confined space, compared to flying .90class at the field in unlimited sky space).

After, my plan is to test the new Align tail assembly I've received just to see if by some chance this one is better (it's exactly the same as I have, but maybe the bearings will have less defects). If not, I plan to shop for high quality bearings (titanium balls and running surface, I know these make a big difference). I'm sure that high quality bearings which will handle the radial force will solve the problem(providing the "static" setup is smooth and slop free, good quality bearings will give this same smoothness in dynamnic). I'm just about sure that the DS420 could be put back on after too.

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08-13-2010 03:47 PM  7 years agoPost 40
Richardmid1

rrProfessor

Leeds, England

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I have had 2 250SE's now and I am going to put the 42mm tail blades on it! I hear people cutting the tail blades down to 25mm!!!

The heli is quite sensitive on collective, maybe I should cut the main blades down?!

TURN THE GAIN DOWN! Oh no I need to turn my gain down to 19% boo hoo! If thats what it needs do it!! A gyro is still affective down to 1%!

60% of the time, it works every time!

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T-REX 250 › Back with 250SE tail wag....
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