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. |
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发表于 2007-12-9 20:53
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