Trex F.A.Q. Updated 4-24-2007

[Cryofix]

******If you have a problem understanding what you are reading because all these new words confuse you, or a subject is difficult to grasp, skip the FAQ and go directly to Finless videos here at HeliFreak you will not be disappointed. I know when I started I had no idea what any of this gibberish meant and the Finless (Bob White) videos helped me a great deal even with my Walkera 35 and Shogun.*******

Finless Videos

Very good read for beginners Here Thanks Awamori

My blades will not track

• Small link(Link from seesaw to blade grips): Try a 1 spin adjustment for the blade that is low, mind your direction of twist on this one make sure your not adding to the distance instead of closing it. The small link attached to the blade grip is used for large gaps in tracking and should be adjust sparingly.
  
  Long link(Link from Swash to seesaw): This is where you can fine tune tracking, your long links don’t move the pitch on the blades as much as your small links, use these to fine the last 2 or 3 mm of tracking. The long link is the link from the swash plate up to the mixer arm in the seesaw.
  
  Blade balance: One of the most important things you can do to help your tracking is to make sure you blades are balanced you can find a simple balancer ReadiHeli or RcHover
  
  Contributed from Gunz:a slight bend in the feathering shaft can cause the blades to be off no matter how much adjustment is done, so make sure you know your feathering shaft is straight.
  Contributed by catfight: Another thing to consider that affects tracking is the screws that mount the flybar seesaw to the rotor housing- Loktite and retighten. This has been the answer in several cases (happens to me after crashes).

Tail boom adjustment.

• Make absolutely sure the vertical tail is truly vertical- prevents belt shredding.

Tail spins uncontrollably

• Gyro direction: Make sure you have the right direction set on your gyro, your helicopter should at best spin very slowly if your linkage is off but if it spins wildly it more than likely because your Gyro direction is set wrong.
  
  Tail blade direction: another thing to check is your tail blade direction, make sure that the tail blades are spinning up into the wash, meaning your blades will spin counter clockwise if you are looking straight at them.

Motor Bogs

• ESC
  Motor
  Blades
  Pinion
  Formula for head speed

Rex wobbles on startup and at low head speed but is smooth on lift off

• When you first straighten out your blades to get ready to fly, there's not really any way to get them 100% by eyeballing them. When the blades start to spin up, the blades will be a little off balance because of this, and the heli will vibrate.......as the blades spin faster, unless they're in the grips too tight, they will straighten themselves out, thanks to centrifugal force.......once they've done that, and got to a reasonably high speed, most of the vibration goes away, and what doesn't go away, becomes a higher frequency vibration that is difficult to see.
  Contributed by H0ndaJunkie
  Just grab blades by the end(tips) and pull. this will get it as close to even as posible. should spool up fine from here as long as you have the blades balanced Contributed by sratzo

Apex Packs Great deal? You decide

• So far I have gotten about 10-12 minutes of hover per pack and after the first few charges they have gotten stronger IMHO I like these packs.

Blue or white Gears

• There is 2 questions here fist is:Why the blue gears (Delrin) Well this is strictly preference on your behalf as far as the main gear is concerned the only advantage the blue has over the white gear is a truer circumference, because the blue is softer than the white it can obtain higher tolerances to the original specs and give you better gear mesh with the main motor pinion, the white gear because it is a harder plastic is susceptible to manufacture defects that can cause a loose mesh on one side and tight on the other(odd long gear).

• Second:
  Why use the blue (tail speed reduction) gear, simple... safety, the blue gearing for the tail drops the tail speed considerably which can and will help you if you have any problems with your tail such as a blade flying off, broken screw on the grips, etc... But the over all advantage to this is safety. If you previously had the white gears on and switched over to the blue for the tail, then you will more than likely have to reset your throttle and pitch curves according to the slower tail speeds. This means you will have to have in increased constant head speed to keep the tail speed at an rpm that does not drift because its not getting enough revolutions.

Pitch curves? Beginner and advanced

• Beginner: A pitch curve is the rate your main blade pitch raises or lowers depending upon your radio settings and stick position. When setting up a radio and heli for the first time everything works off MID stick on your throttle(collective). Make sure your motor is disconnected before you attempt setup any curves as you will need to use your throttle (collective) stick to test. (unplug any 2 wires from your ESC to your motor)
  
  At mid stick throttle(collective) your blades must be at 0 degrees of pitch; at high stick you should have about 10-11 degrees of pitch and low stick should be at -10 -11 degrees; at this point we are only looking at the mechanical aspect of the head using a full range of pitch of 0 low to 100 high
  
  We now know when we move the stick to 100% we have +10 degrees, at mid stick we have 0 degrees and low stick we have -10 degrees.
  
  My suggestion for any beginner is to set your pitch up so that you have -2 degrees on low stick, 0 degrees on mid and +10 on full. The reason for only -2 degrees is simple, as a beginner(at least myself) you have a tendency to want to drop your throttle(collective) as quick as possible if you should get into any trouble, and with a pitch setting of -10 degrees at low stick you will SMASH your helicopter into the floor, so we need to eliminate all that pitch without touching anything mechanical.
  
  This is were Pitch curves come into play, on any radio if you go into the menu settings you will find a spot to adjust your pitch curves, most radios have a 5 point pitch curve which allows for a finer tuning of you pitch opposed to a 3 point curve the Spektrums offer.
  
  5 point setting: 35-40-50-75-100
  3 point setting: 35-50-100
  
  What this will do is make your low stick automatically go to 35% stick even when the throttle is all the way down, so instead of giving a full -10 degrees of pitch when you pull your stick all the way down you should now be giving about -2 to -3 degrees on your negative, this will allow the helicopter to come down much smoother and softer if you drop your throttle(collective) very fast.

Note from Gary JP4 as a beginner you should not have to worry about your idle up curves right away just make sure you normal hover curves are set correct so you -2 -3 on low 0 at mid and 100 at full. Thanks Gary


Why do people mount their gyros under the boom?

• When you crash, the fly bar can destroy your expensive gyro if it is on top. Even a minor crash while hovering can sometimes take out the gyro making it a very expensive crash. Most people move it to a protected spot that is still assessable for making adjustments.
  
  Rick makes nice mounts for the SE, XL, and SuperFrames that allow you to easily mount your gyro safely under the boom where it is still accessible to make adjustments. Here is his website.
  
  http://www.wavelandps.com/clearly/

Tail Belt Tension: How tight?

• Check the tension at the tail belt pulley, looking down just behind the main shaft.
  
  According to the Trex manual: "you should be able to apply light tension to the belt with your finger until it reaches a point 3/4 of the way to the opposite edge..."
  
  Personally, I like to use a small screwdriver to test the belt tension as my fingers are too pudgy to allow me to push the belt and see how far it moves.

How to adjust the tail belt tension:

To adjust the tail boom tension, loosen the screws in the tail block. Grasp the boom firmly and pull backwards (towards the tail). Make sure your other hand is grabbing on a solid piece of the frame. If the tail boom does not move, try loosening the two screws securing the horizontal fin to the tail boom bracket as well. Once the tension is correct, tighten all the screws (remember to reapply loctite).


How to keep the tail belt from loosening:

• The most common cause of the tail belt loosening is the tail boom slipping forward in the tail block. To prevent the slipping you can wrap a small piece of packing tape around the boom where it is gripped by the tail block. This tape increases the OD of the boom to allow the block to get a better grip.
  
  Alternatively, you can put an extra tail servo mount on the boom right up against the block, the mount will also keep the boom from sliding back.

Contributed by Glucoseboy

What does Heading hold mean?

• It is actually Heading hold - the gyro will maintain a "heading" (the direction you are flying) unless you apply some rudder.

Setup info about GY401 delay

• Set the 401's "DS" switch to only if you have digital servo, and set the delay to "0". The delay feature is for the slower analog servos that can't keep up with the 270Hz pulse rate generated by the 401.

How to calculate your head speed

• A simple very easy to use spreadsheet was created in order to do this exact thing so there is no need to know complicated mathamatatical equations, and here it is http://video.helifreak.com/?subpath=...calculator.xls
  Here is a simple easy to use calc for headspeeds
  http://www.readyheli.com/Online_Head...lator_s/81.htm

Contributed by Raven_darkcloud

How to check your Cyclic pitch(s)

• 1) Put a pitch gauge on one of your main blades (not the paddles) and set your collective pitch to ZERO using the collective stick on your TX. Leave it there.
  
  2) Position your blades so that they are parallel to the tail of your heli and input maximum "AIL" on your TX cyclic stick. Rule of thumb is that your max deflection should be around SIX degrees (both UP and DOWN). Adjust ATV (End-Point) if it is off a little. If it is off a bunch, check to see that you have the correct servo-arm lengths. (NOTE: more cyclic pitch is not always GOOD because it is added to your collective pitch and can cause blade stall at max/max deflection. SIX degrees added to TEN degrees is a lot.)
  
  3) Position your blades so they are at right angles to the tail of your heli and input maximum "ELE" on your TX cyclic stick. Same rule of thumb and same remedy.
  
  4) Most heli's that I've seen come out about right with 100% ATV (or 50% if it's part of the swash mixing for CCPM). Most heli's that I've seen will have the correct throws if the movable part of the swash-plate just comes to the "flat" on the swash-ball (not all the way to the mast).

Contributed by HeliHam

Lubes, Maintenance, misc…

• For lube use triflow. When it comes to maintenance Check all parts and screws before and after every flight. Tear down and clean every 10 to 15 flight hours. Blow the motor out with caned air or non conductive electrical cleaner. Clean bearings with isopropyl and re-lube. Inspect belts and gears for wear. Check shafts to be sure they are strait.

Contributed by Raven_darkcloud

Head Speeds; where do you want to be?

• 1. Bob "Finless" White's NEED MORE HEADSPEED camp. Usually, anything above 2800RPM at 0 pitch will satisfy this outspoken crowd. Anything above 3100RPM has a good probability of exploding your wooden blades, so you need carbons to be able to drive that high safely.
  
  Pros: more headspeed makes your heli dramatically more stable and wind resistant, while giving you tons of power for extreme 3D maneuvers and even easier hovering for newbies.
  Cons: Your tail sometimes explodes in midair like it got on the wrong side of Al Qaeda, and if you crash the bird running that kind of headspeed it results in quite a bit more damage (particularly stripped servos) than a lower speed. Flight times are often shorter than 7 minutes, and tales of destroyed LiPos are common.
  
  2. The Aerial Photography "How low of a head speed can I get away with" camp. These folks are all about duration and inertia. 335 Pro Wood blades are popular with these people, and head speeds as low as 1600-1800RPM aren't unusual. Who needs 20C batteries when some nice 8C 3100mAh batteries will do the same job for this sedate crowd? Lots of Sunday Hoverers in this group, and they have a devoted following.
  
  Pros: Long flight times, fewer destroyed LiPos, and relaxing fun.
  Cons: Lots of tales of severe tail wobble (direct related to lower headspeed), uncontrollable tail spinouts if you punch the collective hard, higher pitch required, and some difficulty with wind.
  
  3. The In-Betweeners. This is me. Living somewhere between 2200 and 2800RPM.
  
  Pros: Decent performance, reasonable stability, 8-10 minute flight times.
  Cons: Often the worst of both worlds from a stability, wobblies, duration, and LiPo durability standpoint.

What is idle up/sports mode/..... what does it do and how?

• In order to control a collective pitch heli we need to mix two controls onto the left stick, that is throttle and collective pitch.
  
  The PC and TC tell how much pitch and throttle for a given stick position. In a collective pitch heli (CP) we want to maintain a constant rotor rpm and vary height by changing the pitch of the main blades. As you increase the pitch of the main blades you increase the lift they create but you also increase the drag so the rotor system wants to slow down so you have to add throttle to maintain rpm. As you decrease the pitch to descend you unload the system and if you don’t back off the throttle the rotor will overspeed so you want less throttle. Your pc and tc setup the relationship between pitch and throttle.
  
  Flight modes allow us to have different pitch and throttle settings for various types of flying with each flight mode switch position being programmed separately.
  
  Normal mode is where we do most of our training. Normal mode shuts the motor off at low stick (electric) or goes to idle (nitro) for the throttle and increases as the stick position increases, at the top of the stick movement we should have full throttle. Hover position should be about 5 degrees of pitch and 50 percent throttle around mid stick (more on this later). Usually the pitch is set up for between -2 and -4 degrees at bottom stick 5 or 6 at mid and 9 or 10 at top stick.
  
  Idle up modes are used for aerobatic flying (stunt mode is the same thing), you can have several idle up modes with different head speeds, dual rates or whatever for different types of flying.
  A typical idle up pitch curve would be -10 at bottom stick, 0 at mid stick and +10 at full stick with upright hovering at 3/4 stick, inverted hovering at 1/4 stick. Your throttle curve would be 100 percent at bottom, around 50 percent at mid stick going back to 100 percent at top stick so that at bottom stick you have full negative pitch and full throttle and at top stick you have full pitch and full throttle.
  
  Once you get used to flying in idle up many people set up their normal mode to hover at 3/4 stick by manipulating the pitch and throttle points so that the helicopter doesnt jump when you flip the flight mode switch.
  
  Other flight modes can be set up for different head speeds, competition often requires a different feel for hovering etc but many of us spool up in normal, flip to idle up and go fly, land at half stick, flip the idle up switch to normal and let the heli spool down. Different people do it different ways and this is just the basics so you understand whats going on.

Tracking vibrations:

• Here is my unsafe method of tracking vibrations; I have a workbench with 4 holes drilled in it and I use tie straps to tighten down the heli. (Not a recommended method)
  
  First thing i do is remove all blades, tail and rotor, at this point you eliminate your first possible cause for vibrations; at this point what you want to do is slowly spin up your heli but be aware do not overspeed your motor, with no load on your motor your RPM's will soar rather quick and this could damage the motor if you maintain this type of speeed with no load. Once the heli is spinning you may be able to see the vibrations still there:
  Head
  If you have a head Vibration there are 4 things to check your spindle shaft(feathering shaft); now don’t be afraid to replace this, this shaft can bend just by landing hard. Next is the main shaft what I like to do is take the entire head off and leave the main attached to the main gear and then spin it up, carefully check to see if there is vibration or wobble. Your main gear, you main gear can actually warp under heat and stress, this can cause the heli to get louder when its running and casue vibrations. last is your dampeners make sure you replace them every so often to ensure you get no slop in your grips.
  Tail
  Simple way to test is break down the tail to just the spindle and spin it up if you have a vibe replace the bearing and/or the tail shaft these two thing are the most common cause for vibrations in a tail. If this is not the casue then replace the tail parts 1 by one until you can see the vibration.

This should be pretty simple to follow and will organize data significantly

FAQ original Post will be an editable post and all good confirmed information from the following discussion will be rendered into the top post. This information should be debated and confirmed by other members.

Simple Form

Member question:

Member’s answers numerically listed according to relevance

Optional links (Finless video, maybe vendor link, or copyrighted site outside the freak)


Anyone wishing to contribute to the FAQ forum or stickies can PM me with your question(s), question(s) and answers, or suggestions.

I will also look to set guidelines when asking a question in the forum, like:

My motor bogs down what am I doing wrong?
What we need to know is:
Motor
ESC
Pinion
Blade type and size
Battery size, type, manufacturer
Any other pertinent information


Ed

[rdlohr]

Thanks Ed for taking this on. I made it a sticky for you.
Rick

[Cryofix]

working on this now will be a few more days till finished, also trying to get ready for this weekend at SRW Brooklyn event.

[rdlohr]

Take your time. Thanks for doing this for all of us!

[rdlohr]

Off to a great start!

[JimmyGunz]

Cryofix,

I am new, and searched the site for many answers. A summary is a great idea!

I know it is a work in progress, i saw something that might help beginners like me. On blade tracking: a slight bend in the feathering shaft can cause the blades to be off no matter how much adjustment is done...right? I had a landing where a a rotor blade hit ground... checked out the heli and blades ,no visible damage, but i noticed, a battery later, blades would not track no matter how much adjustment. It would track at 0 degrees, then be off at ~6 degrees, and vice versa. It drove me nuts until i decided to dig in the spare parts bag and try replacing the feathering shaft. Problem solved. I know there are probably many resons for blade tracking problems, but on a beginner level, with some rough landings, is this a common thing?

Thanks again,
Jimmy Gunz.

[Gary JP4]

Really good stuff, looks like this is going to be good. Thanks for spending the time.

One suggestion. I think since this part is directed at new folks you should clarify that the +or- 10 or 11 deg pitch is in idle up or stunt mode and where you suggest limiting to -2 or -3 deg is in normal mode. I assume you are suggesting beginners fly in normal mode with those settings.

[Awamori]

http://www.heliguy.com/nexus/glossary.html
Someone linked this before and I think it would be very good for noobs who might be afraid to ask. I picked up some text book answers when I read it the first time. :wink:

[rdlohr]

Cryofix: This is shaping up very nicely. Thanks for your time and effort!

Rick

[Cryofix]

No problem thanks to everyone who is helping with all this great information

[Finless]

Cryfix,

Long link: This is where you can fine tune tracking, your long links dont move the pitch on the blades as much as your small links, use these to fine the last 2 or 3 mm of tracking.

You should tell them which link is the long link. e.g. the long link is the link from the swash plate up to the mixer arm in the seesaw. It's the longest link in the head.

Bob

[catfight]

Cryofix,

Maybe add these to the FAQ?

My blades will not track Another thing to consider that affects tracking is the screws that mount the flybar seesaw to the rotor housing- Loktite and retighten. This has been the answer in several cases (happens to me after crashes).

Tail boom adjustment. Make absolutlely sure the vertical tail is truly vertical- prevents belt shredding.

[robl]

The 401 answer makes no sense. You have to specify that you are talking about the 9650 servo otherwise lots of newbies will burn out their servos by setting the ds switch to on with an analog servo.

[Cryofix]

Updated sorry was reading but not comprehending

[miragewsu]

General Maintence section might be usefull. What to oil and with that type of oil. Also, make sure all screws are tight in head and tail. They will come off in flight! Links to different sites with tips on learning to fly.

[sratzo]

[

• When you first straighten out your blades to get ready to fly, there's not really any way to get them 100% by eyeballing them. When the blades start to spin up, the blades will be a little off balance because of this, and the heli will vibrate.......as the blades spin faster, unless they're in the grips too tight, they will straighten themselves out, thanks to centrifugal force.......once they've done that, and got to a reasonably high speed, most of the vibration goes away, and what doesn't go away, becomes a higher frequency vibration that is difficult to see.
  Contributed by H0ndaJunkie

Just grab blades by the end(tips) and pull. this will get it as close to even as posible. should spool up fine from here as long as you have the blades balanced

[ormandj]

Good tip sratzo, you can also check for slop in the grips this way.

[sratzo]

your right. you can also hold the heli with blades vertical and the blades will not fall under there own wieght. but will move in the grips if you tap on them. :glasses2: :glasses2:

[shanea1]

Very helpful thanks

[Scoopy]

how about cyclic pitch with the flybar level??

Sam