Anyone tried couterweighting the tailgrips?

[cptsnoopy]

I did the mod described here http://www.helifreak.com/showthread.php?t=41309 to my trex 450se and even though I have not flown it yet (due to wx) I can tell a huge difference on how much pressure the tail servo is required to push/pull to move the tail grips out of zero pitch. (this is without the blades on)

So, I thought that this idea might work well on the stock tail of my converted eRaptor50. I tried spinning it up without blades and as expected, the grips try to center with quite a lot of force. I then tried putting some counter weights on by getting an extended 3mm bolt (instead of the stock blade mounting bolts) and adding bushings and nuts to each side. I was unable to come up with a combination that worked well. I could reduce the force required to move the blade grips back and forth but for some reason the grips were trying to center with the slider bushing closer to the tailbox than in the center of the tail shaft. I did not have enough time to play with it some more so I decided to ask here and see if anyone has tried this and been successful? Thanks for any input offered. :)

[Silenus]

I'm still building my Titan but I am definitely planning on trying this mod on it. :thumbup:

[fixxxer]

Sounds kinda interesting, may give it a try at some point.

[EricW]

Good idea, very interesting...
How do you measure the difference in force, or is it a known fact cause it's used on full scale heli's??
Would love to reduce the amount of load on my tail servo and make the tailrotor more stable, it's a small sacrifice to add some weight to the tail..

Eric

[cptsnoopy]

Good idea, very interesting...
How do you measure the difference in force, or is it a known fact cause it's used on full scale heli's??
Would love to reduce the amount of load on my tail servo and make the tailrotor more stable, it's a small sacrifice to add some weight to the tail..
Eric

to measure the difference (not scientifically) take your main blades and tail blades off (I took my whole head assembly off leaving only the swash on the main shaft). Then, take the rudder control arm off the lever arm at the tail. spin up the helicopter to normal rpm and try to move the rudder control arm. you will find that it is very difficult to move out of center due to the "tennis racket effect" caused by the extension off of the blade grip to hold the ball link. when this mod is correctly done, the centering effect is negated and the pitch slider can be moved with almost no effort and it will stay at whatever position you leave it. then the only resistance to control input will be from the air load on the blades.

if you get time, read the this thread as they have discussed it at length. http://www.helifreak.com/showthread.php?t=41309

[Silenus]

Edit: snoopy just beat me too it! :P

In that post linked above (i reccomend reading it btw, quite interesting) they describe a test you can run to "feel" the difference. First disconnect the linkage rod from your tail servo so that you can grab it at the end and move it manually, causing your tail pitch slider to move back and forth. Now, take of your main rotor blades AND your tail blades, strap your heli down, and spin up the motor to it's normal flying speed.

When this happens the tail grips should naturally center themselves (this is the "tennis racket" effect described in the thread). When you manually move the linkage rod with your fingers you should notice a significant load in trying to change the tail grip pitch. Note that this load can be high even without any additional aerodynamic load from the tail blades themselves (you can also try this test with the tail blades on just be careful you don't accidentally yaw your heli when changing tail pitch!). As you add weights as described in that thread you should be able to greatly decrease or remove the force required to change pitch on the tail. Depending on the weight added you might reduce the auto centering effect to just a slight amount or even make it so that the tail pitch will remain wherever you last leave it.

Yes this this test is not in fact taking a measurement, but should be plainly clear just by the feel that it will lower or remove the extra load on the tail servo. Even if it didn't help hold the tail better, or piro more consistenly (which it has for many) its still a good thing for the servo to work less! :thumbup:

[EricW]

Thanks guys.
Great explanation.
I will definitely read the thread.
And maybe do some experiments myself.
Love this kind of stuff.

Edit:
Wow that was a long one!
Really interesting stuff, worth to test the feel by hand on the tail coming weekend and maybe try the mod with a long bolt going through the original bladegrip holes, I still use plastic grips.
I'm not a 3D wizard at all :D , but like more precise steering and less wear on my servo..
IMO this works for every RC heli tail, the influence will maybe be bigger or smaller on some though..
Thanks for the link!, should read more in the Trex450 topics...

Eric

[cptsnoopy]

I tried playing around with the counter balance on the stock TT tail blade grips and I see why it does not work as well compared to the SE tail grips on the Trex-450. The arm that comes off of the base of the blade grip is not aligned with the center of the blade grip like it is on the 450. I looked at a Logo14 thrusted tail setup and it is not aligned either. To counter balance so the blades are centered will require that the weights be added perpendicular to the arm coming off of the blade grip. If you do like I did and place the weights on an extended blade grip bolt the slider will center near the tail housing and it will be easier to feed right rudder than left rudder. I don't think that is optimal but since the heli requires right rudder just to hover I am going to try and fly it this way a little bit and see how it goes. There is considerably less effort required to move the slider either way after adding some weights.

[cptsnoopy]

I flew the eRaptor today and found that my attempt to counter balance the blade grips made little if any difference on how the tail felt during flight. I removed the counter weights for the second flight and there was no real significant difference. I will repeat however that the way the raptor grips are designed it is not a simple matter to balance them. Of the three 600 size heli's that I have, only the Trex-600 stock tail grip would be simple like the 450. Both my Logo and eRaptor tails are not aligned perpendicular to the blade grip bolt like the Trex's. I also tried out the Trex-450SE with the mod and there is a significant improvement and it is well worth doing the mod.

If anyone else gives this a go and has good results, please post. Thanks. :)

[brovic777]

I don't see the need for them, my Raptor and Mini-Titan fly perfect without it.

If it aint broken, don't fix it.

[cptsnoopy]

I don't see the need for them, my Raptor and Mini-Titan fly perfect without it.

If it aint broken, don't fix it.
what gyros are you using? I am a long way from perfect using the 401 on my raptor. I have a video of a friend doing some nice flying while the camera is mounted rearward on his Trex-600. We were amazed at how much his CF tail control rod was flexing and bending during flight. There was no support from servo to tail and he was using a GY-611. At first I did not know why it would flex that much during flight and then after looking into this mod it is obvious. Another thing to note is the amount of extra work the tail servo is doing to push the blade grips from where they naturally center instead of just pushing air with the blades. If your helis are flying perfect, do not test the theory and see how much effort it takes to move the blade grips. You would be impressed... :D

[brovic777]

what gyros are you using? I am a long way from perfect using the 401 on my raptor. I have a video of a friend doing some nice flying while the camera is mounted rearward on his Trex-600. We were amazed at how much his CF tail control rod was flexing and bending during flight. There was no support from servo to tail and he was using a GY-611. At first I did not know why it would flex that much during flight and then after looking into this mod it is obvious. Another thing to note is the amount of extra work the tail servo is doing to push the blade grips from where they naturally center instead of just pushing air with the blades. If your helis are flying perfect, do not test the theory and see how much effort it takes to move the blade grips. You would be impressed... :D

For my Mini-Titan I'm using a 401 w/9650 and on my Raptor im using the 611.

I don't think my Raptor can fly any better than this:

9m2c-XocryE

[cptsnoopy]

Jason does some mean flying with your heli for sure! It is easy to see the difference, that tail is rock solid. :)

[brovic777]

Jason does some mean flying with your heli for sure! It is easy to see the difference, that tail is rock solid. :)

Sure its mostly because Im running that $360 Futaba GY611 gyro/servo combo. It better run perfect at that price!!!

[mx400]

The new jr 7703d is sweet as well, I think it flys every bit as good as the 611. I'm replacing all my gyro's with it.

[brovic777]

The new jr 7703d is sweet as well, I think it flys every bit as good as the 611. I'm replacing all my gyro's with it.

You got any link to where your getting it from?

[uragano47812]

You got any link to where your getting it from?

Heliproz for exemple, but don't know if it is right in stock. few days ago it was there.

[mx400]

Horizon had them to for a while. Dont know about now.

[fenderstrat]

I've been following this one since the beginning and still kinda on the fence.it seems everyone says WOW what a difference on the bench,then many are saying "I really didnt feel much in the air"..I'm still a little suspicious of the actual use of a test that spins the heli up with no blades...its kinda like taking the tires off of your car ,riding it down the street,then saying it needs a suspension upgrade because of the way it performed.HHMMM.....its not designed to perform right with no blades......all this time everyones tail has been awesome especially the T-rex guys,all I've heard is how incredible the t-rex is bla bla bla and now in the blink of an eye the stock tail is almost"unflyable"I need more concrete data on this one other than "I think it feels a little better"

[cptsnoopy]

I've been following this one since the beginning and still kinda on the fence.it seems everyone says WOW what a difference on the bench,then many are saying "I really didnt feel much in the air"..I'm still a little suspicious of the actual use of a test that spins the heli up with no blades...its kinda like taking the tires off of your car ,riding it down the street,then saying it needs a suspension upgrade because of the way it performed.HHMMM.....its not designed to perform right with no blades......all this time everyones tail has been awesome especially the T-rex guys,all I've heard is how incredible the t-rex is bla bla bla and now in the blink of an eye the stock tail is almost"unflyable"I need more concrete data on this one other than "I think it feels a little better"

A friend of mine was flying a Trex600 with a camera mounted on it backwards so he could get forward video while flying backwards. A side effect of looking backwards on the heli was getting to watch the CF tail control rod bend like crazy when trying to add left rudder (servo arm moving towards the rear). The reason it was bending is because the "tennis racket effect" of the blade grip control arms sticking out plus the effect of air pressure against the blades. It does not take a rocket scientist to figure out that the "tennis racket effect" is adding to the air load against the blades and is completely unnecessary. Unless you try it out yourself, you will not appreciate what everyone else is talking about. When I did the mod to my 450 heli, it made a considerable improvement. I could not correctly apply the mod to my eRaptor50 so my test was inconclusive. I would have to get a different tail setup to do it correctly like the one from Quick UK. So instead of needing more concrete data from someone else, try it yourself, it is not that hard to do.

[fenderstrat]

cptsnoopy.....yes I understand what you are saying completely,and while this isnt rocket science I'm sure some of the physics involved is quite interesting......My thing is this,I'm not in the habit of jumping on every "mod" that comes along.I'd rather wait till its fairly well proven...when the MINI TITAN first came out and people were having tracking problems,first it was "glue the rotor hub to the main shaft"then came "glue the bearings into the arms" then everyone had a surefire winner"cut 3-5mm off the balde grip arms"and in the end NONE of them solved ANYTHING.the simple fix was metal upper mixing arms,simple and very effective....So,my instincts tell me to wait a little with these mods to see what works and what doesnt,next week there may be a new tail mod that everyone swears makes the tail"so much better"

edit:something very intersesting today at work popped up,a magazine called "rc fly" or something was brought in by a co worker...anyway in itwas a review of the GAZAAR MARS and the tail blades had counterbalances on the leading edge of the blade itself...so while this mod no doubt works the question is "where to place the weight"

[ghtracey]

I wouldn't classify this as a mod that "works" or not. The benefit from this is reduced servo load == longer servo life == longer battery life == longer flights. Why waste torque moving the blade grips away from center when there is no need to?

The counterbalances on the leading edge of a blade that you mention I could see offsetting the torque required to turn the blade itself, similar to performance airplanes, where a small surface it "backwinded" helping rotate the control surface. I don't think that this would offset the centrifugal force caused by the control arms though, to defeat that, the tail blade grips need to be balanced around the feathering shaft axis. That's what the "mod" in question does.

Seems to me that this type of balancing would significantly reduce torque loads in the main rotor head as well, but that would be harder to measure.

[EricW]

When done properly and very well balanced, yes IMO.
With unbalanced or inaccurately placed weight rotating out of center it will create enormous unwanted forces in the feathering shaft causing vibrations and maybe even more work for your Gyro>servo combo.
So when you mod it yourself, be as accurate as you can to make it work.
I understand some people don't want to take the risk.
I would like to see CNC aftermarket grips for the MT with a option to place some weights.

Eric

[mx400]

Yeah thats what worries me, without a drill press it would be very difficult for me to get the holes drilled where I wanted, if not drilled accurately it probably would do more harm than good.

[fenderstrat]

that was my point,wait this out a little till it gets refined some....if the weights are not placed properly the "mod" could make things worse,also I'd rather add weights to a legthend blade bolt,the idea of drilling into the blade grip to remove any material may not be so good...the blade grips(main/tail) see some of the highest forces on a heli and the last thing they need is to be weakend

I wouldn't want to drill into the blade grip right away only to find out next month that after 50 flights the grips are cracking,mid flight