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solentlife
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Joined: 30 Dec 2010
Posts: 927
Location: Latvia / UK

PostPosted: Tue Sep 03, 2019 11:21 pm
PostPost subject: Blade pitch
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OK ... as I should - I did all the pitch setup work before taking rebuilt 450 SE V2 out there to test.

I set -4 through to +12 pitch range. I know its a bit more than recc'd ...

I go out there and find that one blade needs 1 full turn on the blade holder link for both blades to track together.

Fine.

Later on the bench - I decide to check all again but this time using a Flybar lock I 3D printed. This physically locks the Flybar horizontal.

Now I find I have -6 through +10 on one blade and -3 through +12 on the other ... if I switch to Idle up - I have when centre stick -2 on one and nearly zero on other ...

?????????

Oh How I love Heli's !!
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Burgess
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Joined: 27 Mar 2012
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Location: Wales

PostPosted: Thu Sep 05, 2019 12:51 pm
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When I'm setting up a rotor head, I have a flybar locking jig which I made that holds the flybar control frame at 90 degrees in both orientations, also a U shaped plate close fit in the holders, that slots into the blade holders to keep them parallel to each other.
With the head and shaft removed, and these two tools in place, and slide the swashplate levelling tool inverted up under the swashplate an just nip up a shaft lock collar under the levelling tool.
Holding the levelling tool and rotate the head while observing the contact of the swashlate base to levelling tool arms. If any of the links are not exactly equal lengths the swashplate will lift when the link that is shorter comes past.

Set all link rods to those recommended in Align Trex SEV2 Manual.

I'm using T6EH-M Transmitter which is the same as Radio Link and for any new heli set-up, I always begin with sub-trims at 00% and EPA at 100% and setting the mechanical position of the servo arms as close to 90 degrees to the main shaft, then tweak using the sub-trims, 1,2,6, and check each arm returns to it's 90 degree position. From here on do not change these sub-trim setting.

For the next step it is really handy if you have a spare swashplate and main shaft, saves disassembling the rotor assembly.
Fit the shaft and lock ring and snap on servo link rods and drop on the levelling tool.
Set Swahsplate to A 50%; E 50% P 50%
set the Idle up pitch curve to 00%; 75%; 75%; 75%; 100%, this save being super critical centring the collective stick for zero degrees.
From here the adjustments are made to the servo link rods.
First move pitch to 100% and note the position of the top of the tool with the bottom edge of the top drilling, it needs to be level. this indicates witch way the servo links need to be adjusted.

Return to centre stick position and adjust the servo link rods as required to eliminate any gaps between arms and levelling tool. Move stick to bottom position an adjust EPA to eliminate air gaps. Move stick to top position and adjust be EPA.

Reset Idle Up Pitch to liner 00%; 25%; 50%; 75%; 100%
Set Normal Pitch to 50%; 62%; 75%; 87%; 100%

Now in Idle Up, lower and rase the collective while observing the contacts of swash plate arms to levelling tool arms, they should remain in contact through out the full range of movement.
Next in Normal it is critical for the swashplate to remain perpendicular as it rises up into the hovering position.

Reset the Swahsplate A 28%; E28% P 50%
The reduced cyclic pitch makes for a more softer reaction.
Throttle 00%; 25%; 72%; 74%; 78%
I prefer a flatter throttle curve while dialling in.
Pitch 50%; 62%; 75%; 87%; 100%
Or even 55%; 62%; 75%; 87%; 100% for initial lift-offs for checking tracking and CoG. To check the CoG lift off to five six foot, and gradually increase left or right rudder, the heli should stay on station and spin.

To prevent variance synchronise the last three points on the pitch curve
Idle Up Pitch 00%; 25%; 75%; 87%; 100%
Normal Pitch 50%; 62%; 75%; 87%; 100%
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solentlife
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PostPosted: Thu Sep 05, 2019 6:55 pm
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Tks for long write up ...

I have to admit that after having rebuilt that lot 2x already in last few days -I'm not really looking forward to removing it all to slide on the levelling tool.

I have considered using the Tie-Wrap method where a Tie-Wrap is put on the shaft ... cut the tail to match the swashplate links and then use that to make sure its level.

I know that the links mm lengths given in Trex Manual do not agree with the Heli I have .. never have for some strange reason. I even took it to an experienced Heli guy to check this and he confirmed that the Align lengths did not work for my 450 ... which is strange as I use Tarot gear specifically SE V2.
There is also the fact that I do not have my links INSIDE the framework - but outside ...
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Burgess
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PostPosted: Fri Sep 06, 2019 6:24 am
PostPost subject: Re: Blade pitch
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solentlife wrote:
... I set -4 through to +12 pitch range. I know its a bit more than recc'd ...

I go out there and find that one blade needs 1 full turn on the blade holder link for both blades to track together.

Fine.

Later on the bench - I decide to check all again but this time using a Flybar lock I 3D printed. This physically locks the Flybar horizontal.

Now I find I have -6 through +10 on one blade and -3 through +12 on the other ... if I switch to Idle up - I have when centre stick -2 on one and nearly zero on other ...

?????????

Oh How I love Heli's !!


That is a wide discrepancy between each blade pitch angle.
Examine for lost motion in:
#1 the bearings of the blade holders.
#2 the linkage between the swashplate and the blade holder.
#3 And for warp in one or both blades.

Clamp the blades together at the roots back to back and measure the distance between LE and TE on the blades at the tips and the roots.



Burgess
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solentlife
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Joined: 30 Dec 2010
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PostPosted: Sun Sep 08, 2019 4:44 pm
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Appreciate all the detail ...

Gave her another go yesterday .. and she's powering up nicely with very little vibration ...

Trying to decide why she's sliding to the left as soon as she gets light on the skids ... to counter it puts her leaning too much to the right for 'comfort'. I know I need to 'grin, grit teeth' and get her up out of ground effect and then she'll likely just have the usual slight lean to the right ... but its unnerving !

I have a feeling that tail rotor is slow in action as I am swinging left - right too much and on one lift - she started to rotate ... I was only about 10cms of deck - so put her down ...
Strange as its not all the time ... but you just have this sense that the slider may be binding on the shaft. I have to say I have never liked the single L arm design and considered swapping for the Tarot Y yoke design that means servo load is evenly placed on the slider top and bottom.

At least she's still in one undamaged piece !!
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Burgess
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PostPosted: Tue Sep 10, 2019 7:24 am
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The reason for the left-slid, it a two-fold, as the heli becomes light on the skids, the airflow down through the main rotor creates a cushion of air (ground effect), and the airflow from the tail rotor pushes the heli to the left.

Try adjusting the first two Pitch curve points to 50%; 55%, or even 50%; 50%, keeping the pitch angle low for the first two points, allows the heli to spool-up and the tail rotor to gain authority. Minimum air flow down through the blades and maximum tail authority. Trial and error for your optimum.

To reduce the right tip, by reducing the swashplate aileron percentage to around 28% and like-wise for the elevator.

Tail rotor authority:
need a fast servo, I have a number of Emax EC9257 on my 450s
2.5Kgf.cm, 0.08Sec/60degree.

There is a couple of ways to setup the servo.
#1 connect the tail servo direct into the receiver and the servo will centre. Fit the output arm/disk on the servo
output shaft, with one of the holes at 90 degrees above the output shaft. Reconnect the gyro in channel 4 and servo to the gyro.
#2 with the system powered up transmitter in rates
Position the arm/disk as above. This allows maximum servo sweep movement which makes for finer adjustment and high torque.

Next, loose-off the servo boom-mounts to permit the servo assembly to just slid, adjust till there's about 5 to 7 degrees of positive pitch on the tail rotor-blades and nip-up screws. Set gyro gain at about 70% trial and error increase til it hunts and back off a couple points till tail hold steady. Adjust servo position on boom till heading is dead ahead.

Also the CoG needs to be direct under the main shaft, an easy check. With the battery in place, hold the heli by the main rotor blade holders, and main shaft horizontal and the heli should hold at any angle. If the not reposition the battery.



Burgess
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Burgess
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Joined: 27 Mar 2012
Posts: 1087
Location: Wales

PostPosted: Sun Sep 15, 2019 5:16 am
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solentlife wrote:


...I have to say I have never liked the single L arm design and considered swapping for the Tarot Y yoke design that means servo load is evenly placed on the slider top and bottom.

At least she's still in one undamaged piece !!


Tail rotor pitch control:

Have a look at these tail rotor pitch controls for Copter X 450, and Dynam E-Razor 450, they control the slider top and bottom.

CX450-02-11 Plastic Tail Rotor Control Set
Price: £7.29
ERZ-012 Plastic Tail Blade Controlling Set
Price: £4.99
ERZ-112 Metal Tail Blade controlling Set
Price: £6.49

http://www.internetmodelshop.com



Burgess
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