View Full Version : Help.. mounting tail servo (JR ds3400G)

01-23-2007, 02:40 PM

01-23-2007, 03:35 PM
You can get little rubber grommets with metal inserts that go into the mounting slots/holes of the servo (my 9650 came with them, but you can buy them separatley). This helps isolate the servo from vibration and makes a nice hole for your mounting screws.

It looks like your servo should mount right up. What trouble are you having?

You can mount your servo on either side of the brackets, and you can rotate the servo to get the control arm to line up with your linkage. ---I have my 9650 mounted on what I would call the back side or outside of the brackets. This pushes the servo further away from the tail boom, and I have it rotated about 45 degrees so the bottom of the servo is pointing up in the air.

01-23-2007, 05:11 PM

01-25-2007, 01:33 AM
Don't feel bad. My brain has bouts of flatulence too and my thumbs are occasionaly stupid. I just finished puting my TRex back together after it attacked me while trying to learn side-in hover.

01-25-2007, 02:50 PM

01-25-2007, 10:02 PM
Hummm... I haven't had any problems with binding.

What do you have plugged where on the RX? The ESC *has* to be in channel 1 (THR) during the binding process, with the throttle closed. (see SmartSafe description below)

1. Power down everything
2. Insert bind plug
3. Power up the RX (this may be where things are whacky - are you using your BEC from the ESC to power the RX?) The RX LED should be blinking.
4. Establish failsafe stick positions on the TX (throttle all the way down, flight controls neutral)
5. Press the button on the back of the TX and turn it on. Keep depressing the button on the back until the LED on the RX goes on solid - the bind button LED on the TX should also go on solid).
6. Disconnect the battery from the ESC.
7. Turn off the TX

Now... to adjust your cyclic/collective servos... you should disconnect the motor from the ESC... unplug all three connections between the ESC and the motor (note, there will be no beeps in this setup, because the ESC actually uses the motor to create the beeps... just be aware of that).

Turn on the TX, and then plug in the RX... watch it's LED... it should flash and then go on solid. You should then have full control. Now it *sometimes* takes a bit for the TX and RX to synch up... because they search and lock on to two different channels. Oh, and the RX/TX will *not* synch up if the throttle is not fully closed (down). That is a failsafe mode called "SmartSafe"... so if the THR (channel one) on the RX does not "see" that the throttle is in it's "failsafe" mode... it will not synch to the TX. I think you mentioned you plugged the ESC into another channel to power the RX... but remember the position of the other channel is *also* remembered during the bind process (and therefore the ESC will not be controlled by the throttle - which is why the motor spun up) and probably why your TX/RX are not synching.

Now, once bound... you should not have to rebind unless you change something (and not to synch up the TX/RX... but rather to store new failsafe settings, like rudder trim). It should *always* see each other. If that is not the case, you should contact Horizon tech support.

As for the one-way bearing... you can either get the Align tool (it's rather nifty... I have one) or just use two sockets...just find one that fits around the bearing, and one that is the same size or slightly smaller than the bearing... just be careful of the alignment when you start to press it out.

01-25-2007, 11:52 PM
Thanks, I throught it had to be in any channel other than the throttle. I'll try that and see if it helps.

01-26-2007, 02:42 AM

01-26-2007, 03:21 AM
Hehe... yeah, but you're gonna love it!

All things require a bit of a learning curve... it's worth the effort, though!

Let me know if you need any more help... I've got Blade Pros, T-Rex 450SAs and 450SEs, a HDX450SE, and a T-Rex 600... I just swapped all but the Blades from a DX6 to a DX7... so I've probably been there, and will be glad to help where possible. I'll also tell you I don't know, when I'm clueless... hehe.

Oh... and *nice* birdies!

01-26-2007, 03:48 AM
It seems to be working fine now. I am going to get this up and running soon. The next step is calibrating the bird. I'll be reading..

(at least I'm not the only Kansan on this forum.. I went to a Metallica / Godsmack concert down there a few years ago... .)

01-26-2007, 04:02 AM
Cool... setup can be tricky - but there are little helpful hints... for example, if you've watched Bob's assembly vids... at the point to set the servo arms and links at 50% throttle for 0 pitch on the blades and all mixing arms and flybar level... just set the Normal Pitch curve on the TX to 50% on all three points. No guessing then... no matter where the throttle is, you're there to set up the mechanics. It works great.

Also, be sure to set throttle hold... it's *very* useful... have it hold throttle at -5% and set up the corresponding pitch curve to match the curve you set in Normal mode. During preflight, switch to hold (disables the motor) and run all cyclics, rudder, and collective (throttle) to make sure all mixes are working correctly... it also can be used to do autorotations (more learning - and you may want to adjust the pitch curve for hold mode at that point).

What part of KS? Last concert I went to was Dream Theater in KS City a couple years ago... *nice*

01-26-2007, 04:18 AM
I'm in Gardner. Just southwest KC area. Thanks for all the tips. I'm sure I'll need all the help I can get.

- mike

01-27-2007, 02:25 AM
Setting up the TRex was not so bad once I got past my stupid beginner mistakes.

The tail is/was the big area on my TRex that is very touchy for set-up. It flies great but the tail slowly rotates left or right in a hover depending on the tiniest tweeking of the linkage or servo mount. When I get it right I can hover for minutes without touching the rudder control.

Leapfrog: Can you give me a tutorial on setting up throttle hold? I am still working on nice smooth hovers and orientation (side-in...) and do everything in normal mode.

01-27-2007, 04:25 AM
PilotDane - what gyro are you using?

01-27-2007, 05:12 AM
Yeah, sure... Throttle hold is basically configuring a "predetermined" throttle setting to a switch on your TX... and it has a corresponding pitch curve associated with that throttle setting. In other words, the throttle is held fixed (usually zero or slightly negatively gained) and the rest of the head interaction functions normally - according to the pitch curve you have set.

If I remember correctly, you have a DX7... no?

So if you are doing your flying in normal mode, then simply set up the "throttle hold" pitch curve to match your normal mode pitch curve (select "list" mode using the UP and SELECT buttons simultaneously, then select the "THRO HOLD" menu... by default, it is inhibited (INH). Press the "Increase" or "Decrease" button to enable the function. By default, the menu shows that the throttle position ("HOLD POS.") is -5.0%... and I just use that value. That menu also allows you to set which switch to asign to the function... the default is the top right "hold, rudder D/R" switch... (I accepted both defaults). Now, by enabling the T/H function... a new pitch curve shows up in the menu: "PI CURV HLD" (selecting with the "UP" and "SELECT" buttons again... select that, and just enter the same pitch curve values you have set for Normal mode... and you're done.

Now, how I use it... I power on the TX... and then select HOLD (switch in the "1" position - the TX screams if you power it on in TH mode)... then power on the bird. It will initialize normally (just like you have it in Normal mode). The difference is that no matter what you do with the throttle stick, the motor will not spin up. All of the servos will function normally... and I have a little pattern I go through for preflight... check each cyclic movements (right alieron, left aileron, back pitch, forward pitch, left and right anti-torque [rudder]), and then collective (up throttle and down throttle)... all while watching the heli to ensure everything is smooth and moving in the right direction. I then walk the heli out to the helipad, and when I'm ready to fly I switch out of TH mode and advance the throttle.

"Weeeeeeeee! starts here."

Now... as you progress, you'll want to change the throttle hold pitch curve a bit to allow for auto-rotations. Basically, set a bit more negative pitch for the full down throttle, leaving the full up range normal. Negative pitch is used (really, it depends on the altitude you're doing these from) to keep the headspeed up as the birdy is decending without power... and the collective is moved more positive as you approach the ground for flare to landing.

Hope that helps... and let me know if I left something out (<- that was a stoopid statement) - what I meant to say was if I didn't make anything clear.

01-27-2007, 01:48 PM
Thanks Mr. Frog: That is exactly what I was looking for. Once already I have had my neck strap bump the throttle while getting up from plugging in the heli's battery.

Mike: I've got the Futaba 401 and 9650 digital servo (yes, I know... not very creative... everyone seems to have that combo.)

01-27-2007, 07:17 PM
I decided to go against the mainstream ...and get a 500T/DS3400G.. we'll see what ?'s that brings..... (I've read to mount this gryo under the main gear instead of under the tail)
Last night I sat down and actually got the head aligned and balanced!! I had to watch Bob's video on CCPM several times.. Now I get it.... at least I think..

01-28-2007, 12:23 AM
first hover... :) well sort of.. I am still waiting for a gyro so it kind of spun around in slow circles after I dialed it in.... Everything appears to be tracking good. The swash and head is leveled.. the blades have 0 pitch at 50 and I have a +/- 9 max and low left stick...

01-29-2007, 05:12 AM

Nice Mike!

As for the G500T and DS3400G... I've paired that set up on one of my birdies (actually, my SE). I found the G500T a bit "tricky" to set up, and a bit "sensitive" to fly... it does well enough, but plan on turning the gain *way* down in HH mode. It likes to wag a bit. Just my two pennies.

I installed mine on the lower nose tray, back as far as I could get it towards the motor.

01-29-2007, 05:35 AM
i am going to try and mount it right beneath the main gear.. hopefully it will help. i was told this combo was pretty good.. almost the best out there. i should get it tomorrow afternoon, so i'll let you know. i'm off the next 2 days so all i have is heli time :)

01-29-2007, 05:44 AM
leapfrog - is that a good pitch ratio... i was told to gun for +/-6 but i didn't want to get used to that... i tried for 11 but found i was binding the head,.. i'll have to adjust all the links to accomodate that pitch,, felt that the 9 degree was a good starting point..

01-29-2007, 06:24 AM
Yep... that's about perfect... you *can* detune it (as suggested), but then again, you also don't have to use all the stick (pretty much the same thing).

+/- 9 degrees is a really nice throw on these helis. The most I've gotten out of a 450 head without severe CCPM interaction is +/- 10 degrees... (interaction showed up at -11 which said that I didn't have the swash perfectly centered... but it was *really* close).

To be honest, you are not going to be using that throw anyway. It's more important that you have the pitch at 0 for a 50% stick, and that the swash, flybar, and mixing arms are level (especially the mixers - they throw the gain into the mix)...

One hint... set your throttle curve a bit higher than you think "normal"... a higher headspeed for a given pitch is more efficient on the 430L (especially in hovering). I have mine set to move through 75-80% as the head goes positive pitch in Normal mode... That's my personal preference, your mileage may vary.

01-29-2007, 06:47 AM
great... I'm glad I don't have to go through the head again.. my cp6 value on my Tx(dx6) is set at 65% and that gives me the 9 degrees according to my pitch gauge. I can't wait to start playing with the gyro..

(and a cool pic from cali)

01-29-2007, 06:50 AM
Oh man... the shell casings falling away are way cool... (I need a mini gat - actually two - for a "certain model" I'm working on)

Sounds like you've got your finger on the pulse. Let me know how the gyro config works out.

Brutal E
02-28-2007, 01:47 AM
I want to do a scale Cobra that sucker is tough.

03-01-2007, 07:48 AM
Hehe... yeah, no doubt. A Cobra would take a while... and would be tough to stuff most mechanics into that thin fuse... not impossible, but challenging.

I'm just starting my .50-sized Airwolf... using Rex 600 mechanics... it's not so much a "scale" project (seeing as it's a TV star more than a true 222 build)... but it was a nice place to start for me. I've accumulated a *ton* of data... and plan on doing a pretty decent job (interior, rivets, etc)... should be a fun build, and one to learn on.