PDA

View Full Version : TREX250 Tail analysis, spacer upgrade and Chinese weights


Pages : 1 2 3 4 5 6 [7] 8 9 10 11

toyturbo
03-31-2009, 01:12 PM
The only way it'll work better is if the metal tail control arm eliminates the slop between it and the plastic ball on the pitch slider. That's the only place that there's any slop left in mine. If it doesn't eliminate the slop, then it's nothing more than bling as I'm sure the plastic one is quite strong enough. I'm considering attempting to fill the hole in my plastic arm with epoxy, and then redrill it smaller until the pitch slider ball JUST fits. Might just be the ticket. :thumbup:

I gotta ask, will the entire tail assembly from a Gaui 200 fit? How about just the rotor itself and the slider? :dontknow

Actually the new metal pitch slider has a longer pivot point compared to the stock plastic one. The ball is positioned further from the attachment point (4-5mm) which creates better mechanical leverage thus increasing tail control/authority. The tail servo doesn't have to move as much to get the same pitch deflection, easing the load on the servo. I would recommend getting one if I were you!

Vinger
04-01-2009, 12:13 AM
Actually the new metal pitch slider has a longer pivot point compared to the stock plastic one. The ball is positioned further from the attachment point (4-5mm) which creates better mechanical leverage thus increasing tail control/authority. The tail servo doesn't have to move as much to get the same pitch deflection, easing the load on the servo. I would recommend getting one if I were you!
If the ball is further out, YES on the mechanical advantage but a definite NO on less servo movement ACTUALLY more servo movement for the same effect at the tail.

LONGER ARMS = LESS throw

harryboe
04-01-2009, 11:06 AM
If the ball is further out, YES on the mechanical advantage but a definite NO on less servo movement ACTUALLY more servo movement for the same effect at the tail.

LONGER ARMS = LESS throw

I don't agree! It's more like using the full servo travel.

SAME ARMS = MORE throw / MORE resolution / LESS speed

.. and speed was not the issue so far.

Thrashaero
04-01-2009, 01:50 PM
i have the longer arm metal bellcrank...and it has significantly reduced my overall throw. :thumbdown:

i'm also not particularly impressed with how there's slop with it vs. the bushing it comes with.

Vinger
04-01-2009, 03:19 PM
I don't agree! It's more like using the full servo travel.

SAME ARMS = MORE throw / MORE resolution / LESS speed

.. and speed was not the issue so far.
Maybe I was not very clear in my explanation, but let us try again.

If the belcrank has a longer arm (where the pushrod attaches), then with the same arm lenght on the servo side, one would get LESS pitch change (throw) than before. The torque required from the servo would be reduced as you now have mechanical advantage from driving a longer arm from a shorter servo arm, comparitively speaking, BUT definately reduced pitch change range.

If you still can't understand it, picture a small pinion driving a large gear - large gear moves slower, but has more torque. The reverse of a larger pinion will drive the gear faster is also true, but with less torque than before. Hope it is clear as mud now.........

helidude3
04-01-2009, 04:19 PM
guys, what ever, there has been evidence that there is less servo travel so you must be right. Anyway, Can't you just use a longer arm. Instead of putting the ball at 5mm, you put it at 7 or even a little more to get max travel?

Mikej
04-01-2009, 04:45 PM
Having a longer arm on the bellcrank means that you will need less power, but more movement to create the same amount of movement at the tail slider. This means that you can use a less powerfull (less torque) servo and that you will have greater resolution (accuracy) as the servo will have to move more - all sounds good to me :)

Mike.

rotary65
08-06-2009, 08:35 PM
Hey guys, the Trex 250 I just got from Flying Hobby has tail grips with built-in weights. Are these as effective or not? Should I still install Heim Joint's weights or will it be too much?

HEIM JOINT
08-07-2009, 11:19 AM
Check out the test of them http://www.helifreak.com/showthread.php?t=130227&page=3 post #1

HEIM JOINT

rotary65
08-07-2009, 01:38 PM
Thank-you very much much for the link. From the video, the Align weighted grips reduce the force to 5 oz at 20 degrees pitch. Since your weights on the stock grips reduce the force required from 6 oz to 1.5 oz, is it reasonable to assume that adding them to the weighted grips will result in a further 1 oz reduction ( to .5 oz)? If so, that will reduce the loading beyond the ideal point of 1.5 oz. Perhaps it will not be that dramatic a reduction.

Should I modify your weights (once I receive them) to reduce their weight to compensate or just install them as-is?

HEIM JOINT
08-08-2009, 08:55 AM
If your tail control system is totaly slop free you could probably get away with the current weights as is. The only reason 0 pushrod force is not ideal is most tail control systems have some slop and having some pushrod force left loads the slop out on either side of zero pitch. As far as trimming the weights yourself, unless you have a milligram scale to match them with I would not suggest it. My weights are matched to within .002 gram both nuts and bolts to eliminate any possibility of vibration caused by the weights.

rotary65
08-12-2009, 07:07 PM
Received and installed my pretensioner and chinese weight sets. The packaging and instructions that accompany the parts is very nicely done and would make installation very straightforward even if I hadn't watch the videos - I was impressed!

Although I'm sure the weights are doing their job, I am amazed at how well the pretensioners and GAUI bearings work. The only slop now is from the slider and ball links; overall play in the system has been dramatically reduced (ZERO in the grips).

As a side note, my Align driver was too imprecise to take out the grip screws, even with heat; coincidently the M5 Torx worked great taking out the original Align screws - at least, it worked for me.

Thank-you for offering this product/service!

rightflyer
08-27-2009, 07:39 PM
I installed the chinese weights and preload bearing spacing upgrade. I also followed the video in making sure all the bushings were not binding and free moving. Well my tail hunting/wagging is gone, but my heli now just spins on the ground. I advanced gyro gain to about 50 with no change. Any suggestions on where to look next? Servo, gyro?Thanks.

Thrashaero
08-27-2009, 09:12 PM
I installed the chinese weights and preload bearing spacing upgrade. I also followed the video in making sure all the bushings were not binding and free moving. Well my tail hunting/wagging is gone, but my heli now just spins on the ground. I advanced gyro gain to about 50 with no change. Any suggestions on where to look next? Servo, gyro?Thanks.



Typically you should reverse the correction direction in the gyro (servo direction). This should not affect your user-input direction. it is the correction direction that is backwards, perpetuating a continuous yaw because the gyro is giving the servo backwards direction and of course unable to satisfy a 0 yaw so it just keeps it jammed to one side.

rightflyer
08-27-2009, 09:54 PM
I thought about that, but it is funny because I was able to do hover before the upgrade. So that told me it seemed to be set correctly but what do I have to use. I am glad my other 3 helis were not this much of a problem to get flying.

dna001
08-28-2009, 10:12 AM
I installed the chinese weights and preload bearing spacing upgrade. I also followed the video in making sure all the bushings were not binding and free moving. Well my tail hunting/wagging is gone, but my heli now just spins on the ground. I advanced gyro gain to about 50 with no change. Any suggestions on where to look next? Servo, gyro?Thanks.




Sound like to me you have put your tail blade holders on back to front, it should be leading edge control. I bet you have them trailing edge, Been there done that, got the head ache to prove it :-)





.

rightflyer
08-28-2009, 06:48 PM
Good suggestion. That makes tons of sense since it was flying normally before I took the tail apart. I will check it out. Thanks.

rightflyer
08-28-2009, 08:13 PM
Just got done redoing the tail and it is back to hovering. However, the small tail wag is impossible to shake. Even down all the way down to 20 gain, it has a small left-to-right wag even with the chinese weights.

johnnychimpo
09-02-2009, 07:02 AM
Even the newest updated tail grips, the ones with the large weighted ends, do not perform as well HJ's weights with the original grips.

rightflyer
09-02-2009, 05:11 PM
I did some more work on the tail and spent a lot time adjsuting the gyro gain slowly and it is hovering with very little hunting. However if I go to fly forward flight it does some hunting. Still it was the best flying I have had with it.

Wazzer
10-01-2009, 11:12 PM
Hi Guys

Is there a web page or somewhere to buy these spacers and weights from?

Does anyone have a picture or two of what you get in the kit? Unfortunatley i dont have acces to you tube to watch the videos (its blocked on my works network)

Thanks in advance
Ben

Ben

HEIM JOINT
10-02-2009, 08:39 AM
Send me a PM and I will give you all the purchase info.

Thanks, HEIM JOINT

daniel.messem
10-06-2009, 09:07 AM
PM sent - cant wait to try em out! :banana

HugoCraft
10-19-2009, 11:34 PM
Okay I'm new to the 250 class heli's comming from a great holding 450 that has a JR770 w/ 3500G. So I bought the 250SE super combo and built it watching finless videos and so far my tail is holding fairly well at a gear/gyro endpoint of 28 which equals about 19.44 True Gain. But I've only flow it in 5+ MPH Winds and every now and then the tail will slightly wag back and forth maybe 1/4" left/right a couple times. This little heli keeps me on my toes giving me the noob feelings that I haven't had in a while so I really haven't pushed it that far yet. But I've done a few 15' tail slides and it felt like the tail held.

Also mine will piro really really really wicked fast but when I let go of the rudder stick it stops rock solid. I'm using the correct inside hole on the servo wheel, rudder endpoints of 150 on my DX7, I did the gyro travel limit thing like finless did in the tail setup video, and I have no delay set in the gyro. I need to get the piros on video because its FAST! I'm not sure if thats a good thing or not. :shock:

I'm running the KBDD tail blades but when I grab the blades there is a slight about of slop left/right with the tail servo not moving. How much of problem is that? Is that normal or should I try to get it out? Will the metal Align Metal Tail Rotor Control Arm Set H25092 (http://www.helidirect.com/align-metal-tail-rotor-control-arm-set-h25092-p-10528.hdx) solve that or make the tail better? If anything I wish I could get the "Bearing Holder" (25T009) in metal since it appears that where the slop is comming from. I'm talking about the plasitc ball unit that the arm goes to that slides the tail shaft.

Thrashaero
10-25-2009, 11:10 AM
the align metal rotor control arm you linked doesn't do you any good. it has slop in it and binds as well, if not worse than the original plastic arm. the problem is the hole of the arm vs. the bushing that it's supposed to ride on. there's slop there, and of course when torquing something like that causes it to tilt vs. the bushing, introducing bind.
it also does not have a smaller hole for the ball link on the slider (so it could have less slop).

so i found that align metal one to be useless. i changed it out for a microheli bellcrank arm that has a bracket that goes over top of the slider that it supposed to work with. since that microheli slider has a post on the top to be used with the bracket guides for 2-point control of the slider (so it binds less in the case the bushing in the slider gets worn on the tail shaft.)

it really cleaned up the performance of my tail, due to a lot less slop, primarily in that ball link where the slider ball sits into. also, instead of bushings on the bell crank pivot point, it uses 2 bearings which works much nicer.
though, the downside to the microheli parts...some modification necessary to that upper bracket guide (so the post on top of the slider moves freely when it tilts back and forth depending on it's position along the tailshaft).
just look up threads on that microheli parts and you'll see a thread where i explain in more detail about how to get it modified.

the other downside is that there are consumable parts that can't be readily replaced, such as the bushing in the slider (that slides on tailshaft)...it's flared instead of screwed in place.
also, the plastic cup on the end of the bell crank that drives the slider ball tends to wear out and i'm not sure where to get another cup.
until i can get another cup, my tail performance has degraded a bit due to the slop from the worn out cup. it could've been my fault since i put graphite as lube in there and it probably did more harm than good.

however, at first you'll notice a real difference and it still works better than the align metal crank/plastic slider...even when it's worn out.