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Align 3G FL760, and 450 class five-blade main rotor head.


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Burgess
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PostPosted: Thu Mar 31, 2016 3:37 am
PostPost subject: Align 3G FL760, and 450 class five-blade main rotor head.
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I'd been thinking of converting one of my T-rex450SEV2s to either a four blade or five blade main rotor. Well...waleeed00's question regarding operating a five-blade rotor head without Align 3G stabilisation, that and finding a used Align 3G on ebay for just £20.00 was all the incentive needed to purchase both...This might progress to a scale project, with an Align EC145 fuselage and 22 volt system.

Purchased the Align 3G FL760 from ebay on 18th March and it arrived on 21st March!...that's just a day longer than anything sent by 2nd class mail within the UK.

Being second hand, I decided to install it in one of my two-blade fly-bared T-rex 450SEV2. This one was really just a test bed for a rewound Turnigy X500-4000 motor, with Hextronic HET900 analogue cyclic servos and Telebee gyro. So did a refit with a spare digital servos Hobbyking HKSCM9, very inexpensive were £1.89 each, they work OK well good enough to familiarize myself with the setting-up procedure for this Align 3G.
HKSCM9 servo Spec.
Torque: 1.4kg @ 4.8v,
Speed: 0.09/60deg @ 4.8v.

Replaced the rewound Turnigy X500-4000 motor with a Kada 3500kv stator and the bell from a Hobbymate 2000kv which has a stronger magnets.

To energise the 3G in setting-up mode, one needs to first press the set button and then connect the battery...At this point I though, three hands would be a really useful. Instead I made-up an on/off switch module, using the bottom cases off two old Walker servos to encase the RS SPST switch spliced into a short servo extension lead and connected that in-between the ESC and receiver.

The problems of where to fit all the electronics, that and the JR male socket with that flange tends to splay the plugs when plugged in the receiver, will change them when I can source the correct Futaba plugs. Consequently am using a short set of Futaba-ended servo extensions.

So receiver on the bottom plate, Align 3G FL760 on the outside of starboard side frame and switch module on the inside. Extension lead set from the Align 3G FL760 with sockets to inside of port frame. ESC up front, have the connectors outside the frame for accessibility, not aesthetically pleasing, will redo later.

Set-up in small heli mode as per the manual, set the rudder link-ball at 5mm out on the output arm and kept the rudder gain high.

Turned down both Aileron and Elevator gain, and the heli reacted a little smoother than normal fly-bared control.

Rational, by testing/setting-up on two different airframes, then when both on the one airframe the Align 3G FL760 and the five-blade head, would each be relatively known quantities.

When I ordered the 5-blade rotor head on 21-3 also bought a set of narrow plastic blades from another vendor, thinking they would all arrive mid to late April.

Rotor blades:
while waiting for the plastic blades to arrive I was going to use 312mm carbon fibre reflexed blades, however, the blade holders on this five blade head are more suited to the root of 285mm 400 class blades as I've used on my Walkeras. These particular 285mm symmetrical blades and have a maximum head speed of 2400rpm...so proceeding with caution.
There's no tail authority problems even with using one of these little Hobbyking digital servos on the tail.

As this will be a near scale maybe an EC145 450, semi symmetrical blades would be the way to go, either make a set of purchase a set depending on the cost. For now I'll use these symmetrical blades to test the head and find the optimum head speed, throttle and pitch curves.

Phasing is really simple ‘phase angle' is about 90 on account of movement due to flex at the radius arm joint.
***************edit***********************
I said phase angle, however, that should be the mechanical advanced angle. Phase lag is variable depending on a number of things.
******************************************

As this being a floating head design each blade holder needs to be set to an identical pre-load setting to keep the blades in track as the head speed comes up and down from operating rpm.




Will replace the the all black blade with a stripped one




The switch in just visible behind the 3G unit.







I've an idea for a tool/gig to setup the pre-loading of the blade holders.



Burgess
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admiral
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PostPosted: Fri Apr 01, 2016 3:37 am
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Well documented setup, will be interested to see how it progresses when the blades arrive.
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Burgess
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PostPosted: Thu Apr 21, 2016 2:31 am
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Thanks Keith,

The two sets of symmetrical blades ordered from Banggood.com arrived a while back. CopterX plastic blades and generic wooden blades.
This will be a first for using either type of blade.

Typically, when wanting to do something specific other things make demands on your time...

#1 I had to do an emergency repair on my C70 off-side front door window regulator, one of the Bowden cables failed leaving the window fully down, pit-props to hold the glass up while awaiting a cable set. I made-up a mounting plate to hold the winding motor in place and powered it via a DC ESC and my spare 2.4ghz RX so I could rase and lower the window using my TX without having it in the door and thereby facilitate primary setting-up and adjustments when the complete window regulator cassette was back in the door. Really handy to be able to stand out side and rase the window.
#2 Car MOT prep
#3 me MOT at Hospital
I got a 12 month certificate for the car but nothing for myself...that's life.

Helicopters...
Plastic Blades, first impressions,
Black plastic visibility problems,
Pronounced flexibility,
Pronounced surface roughness
Chord CoG is forward.
Foil section 13% thickness at approx 27% chord, with large leading radius. Might suit lower head speed with high pitch angle.

L/D ratio may not be very efficient.
Weight and blade CoG all blades close match.
I'm tempted to just reshape the foil section and smooth out the surfaces, however, will try them first.

The 5-blade head is a generic from world.rcshop so not a high end product. Strip down, apply thread-lock and reassembled.

Static mechanical setup with collective at mid-stick in Idle-Up, I started with all five pitch link-rods at identical lengths, however, each blade had a slightly different pitch angle. On close inspection found the link-balls were not centred on a line round the swashplate rotor. So I made a split-ring jig to keep all blade holders at 0 with this in place, set each link rod to the required length.

Used 5mm strips of white self adhesive label of equal lengths to rap around the ends of the blades. I came across a set of luminous stick-on page markers five colours, and stuck them on the white strips, just the job for tracking 5 blades.

Blade holders: with the blades fitted they all droop down, however, all the blade tips are at different heights, but pulled in to track around mid stick. Consequently lots of vibration as the head spooled up and down.

Normal flight mode
Pitch.....50, 62, 75, 87, 100
Throttle..00, 55, 60, 60, 60

With those curves the heli would suddenly lift-off vertically, so I reset limits to normal pitch and throttle curves:
Pit 45, 70, 75, 75, 75
Thr 00, 55, 60, 60, 60

with collective approaching mid-stick the heli tends to drift/slide leftwards too easily.

Reset to:
Pit 42, 50, 75, 75, 75
Thr 00, 55, 75, 75, 80
Now at the same stick position the heli suddenly lifts-off.

Conclusion: flexing at the radius arm hinge pin had an effect like an advance and retard mechanism. Fitted later version with radial ball raced radius arm.







I like to have the whole of the blades in track rather than just the tips at all head speeds, so head off and do a basic mechanical setting check.

With the 5mm ply split ring in the blade holders locking them at 0 pitch, and swashplate leveller tool inverted on the shaft and up against the underside of the swashplate. Spin the head, any maladjustment of pitch link-rods, the swashplate will lift-off or push against the swash levelling tool.





Keeping the ply-ring in the blade holders refit head into heli with blades at 0 pitch, servo-arms at 90 to main shaft adjusted servo to swash link rods link-rods.

Refit the blades and the tips are all at different heights, the blade holders exhibit different amounts of damper pe-load, so need to make a setting apparatus and either produce additional spacers shims, or ease-off each blade holder screw to match all blades to the height of the lowest blade.

Nevertheless, cyclic control with the plastic blades which are 310mm drag bolt to tip, slow response, with the 285mm foam filled blades cyclic response is much crisper.

Plastic blades, two lines of thought,
#1 shorten one set to 285mm and see how they function.
#2 keep the other set at 310mm and re-profile at least the outer half on each blade.

Now need just need to make that apparatus for setting the pre-load on the blade holders, and hopefully achieve all blades in track at all head speeds.



Burgess
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tombo242
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PostPosted: Fri Apr 22, 2016 4:27 am
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Are you sure that there is no warp in the blades Burgess, I usually find that any 'out of track' is caused by a faulty blade if the roots are in line they should track.

Just a passing thought which I'm sure you've covered already.

Tom.
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Burgess
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PostPosted: Fri Apr 22, 2016 9:12 am
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Yeah Tom, there is very minor span-wise differences with the plastic blades, however, there is the same error occurs with which ever blade set is fitted. Spool-up the head to spread-out the blades, then disconnect battery, rotate the head by hand as the blades pass a vertical register marking-off for each. There's a difference between the highest and lowest of 10mm. Deflect each blade holder vertically and the variation in resistence against each damper rubbers (O rings) is palpable.

What I'm looking to do is produce shims with thickness adjusted to equalise the pre-load of each blade holder...great fun.
When I've made the apparatus for measuring this I'll post photos.

Right now though it's a case of time management and rain dancing, it's been quite worm and dry these last three days. I need to redo the soft top, and service each wheel station on the C70. Saw the doc on Tuesday and have been able to defer that procedure, which is a relief.



Burgess
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Burgess
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PostPosted: Sat Apr 23, 2016 10:51 pm
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Keith,

Still need to do the blade holder pre-loading, however, after trying the 325mm plastic and wooden main blades found the heli suffers from poor tail authority. With the 285mm main blades tail authority is just fine so no need to fit multi blade or larger tail blades, and with a smaller rotor ‘disk' the heli is far more agile. -A set of Walkera blades suchas those used on the 36, 60, Creator 400, Hikco 400 class helis would be a good choice. But for now I'm back with those foam filled blades, they have a maximum rotation speed of 2400RPM so need to limit head speed below that.

At present I'm using a Turnigy X500-4000, with a 11t pinion which at 100% throttle would result in a head speed of 3326RPM, at 65% this drops to about 2162RPM, hence the lower pitch curve percentage linier throttle curve.

Normal flight mode
Pitch.....50, 62, 75, 80, 85
Throttle..00, 65, 65, 65, 65

I've reduced cyclic response but increased collective
Swash mixing:
A 20%
E 20%
P 60%
However, I will soon fit a 3200kv motor and then redo all those settings.

Recently found a good source of potential blanks for making wooden rotor blades, so I'm in the process of producing a pair with compound foil section blades, and will also be making a two-blade set of semi-symmetrical blades.



Burgess
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Burgess
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PostPosted: Sun Apr 24, 2016 9:20 pm
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I reexamined the blade holders and removed the one with the greatest movement perpendicular to the shaft and the one with the least movement, and found variations, too much clearance between the central bore and the shaft also excessive clearance within the race.

Like this not to scale


The problem with these small bearings is that some manufacturers make the running clearances slightly larger to allow for expansion when the bearings heat up at high RPMs. I've often thought of replacing blade holders bearings with bush bearings. So the problem is poor quality radial bearings, considering the price of the head I'm not really surprised.



Burgess
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tombo242
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PostPosted: Mon Apr 25, 2016 2:58 am
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Seems to be a problem with the manufactures anything to keep costs down. Can't blame them really - I've been there myself in business. However in this case the bearings do not do the job that they are supposed to do so that is not satisfactory at all.

Maybe the Chinese need to update their engineering some.

Tom.
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Burgess
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PostPosted: Fri Apr 29, 2016 5:26 am
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Decided to shorten the other set of plastic blades down to 285mm weight and CoG all match.
Charged a LiPO and spooled up...no lift increased pitch percentage and only slid leftwards. Lifting the heli by the rotor head felt some odd movement. Stripped the head down, found the swash-rotor was now free to move up and down within the radial bearing, only about 0.6mm but that is enough to effect pitch curve, and that's the reason for why the heli was suddenly leaping upwards.

The bottom edge of the rotor has been swaged over to form a flange, decided to make a flat circlip from a paper clip, used a 14mm socket as a former, then hammered the wire circle flat, work-hardening resulting in reasonable spring qualities. Cut the tangs off and slipped the clip on.

Enlarge this photo and the that flange is visible at the bottom of the swash


Made the clip 0.1mm thinner than the gap.





Clip fitted


I used the upper portion a the former.



In either the full or shortened form, these plastic blades seem to need a greater pitch angle to generate lift-off than ridged blades do with the same throttle curve.
Will next try smoothing out the foil surface.


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admiral
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PostPosted: Fri Apr 29, 2016 6:13 am
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Hi Burgess, this is a KDS that I've set up with a 4 blade head last week, test flew it last Saturday and it flies great, blade tracking is spot on. I did all of the adjustments at mid pitch adjusting each blade in turn to 0°, while the blades are thin flexible plastic they track well in a hover, I would not trust then for any radical moves, but as it is going into a scale Bell 222 body that should only ever get moderate sports flying.

The KDS is one I bought by accident on Ebay and sold all of the accessories, Tx/Rx etc and recovered all my money, the reason that I'm using it is that I had a Torque Tube tail drive that would fit that body, the body currently has a Blade 400 in it and I can't get to the tail to tighten it enough so while it flies I keep loosing tail authority.







[/url]

The other reason for changing was that the 4 blade head that I had was not suitable for the Blade 400.
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Burgess
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PostPosted: Fri Apr 29, 2016 11:31 am
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Think I drew the short straw with this particular floating head Keith, but I wanted to try one, so spending time sorting this one out is worth the effort. Had a rethink and stripped the head out again. Removed the circlip and then pressed that inner swash rotor with a G cramp eliminating that gap and in the process found the link-balls now rotate in a concentric circle. Reset all pitch link rods to the same lengths, fit the 285mm foam-blades and at zero percent collective all are within 0.1 of 0 degrees static and no sudden leap upwards when spooling up.

On the bright side, I now know how to trouble shoot one of these cheep floating 5-blade heads in the future. Now I need a near-scale 450 size fuselage to suit...but which Confused




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Burgess
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PostPosted: Sun May 01, 2016 7:30 am
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Readjusting feathering shaft pre-loading:

The pack of brass shim-spacers 4x5x0.78mm arrived today, so I replaced each of the original 4x5x1mm alloy shim spacers with two brass shims; the static height of the blade-tips are now within around 4mm of each other. I don't fully trust those foam filled blades, now have the wooden set fitted. With all blades at 0 spooled up and they maintained the differenced displayed during static check.
Next, adjust the individual thickness so that the static blade tip heights match and the pre-load perpendicular resistence too.

With the plastic blades fitted in this floating blade-holder head they need 7 degrees of pitch to start lifting, and then it's more of an unpredictable leap up then controlled accent. Whereas the wooden ones start at 5 degrees and very controllable accent.




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PostPosted: Mon May 02, 2016 2:40 am
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Burgess wrote:

On the bright side, I now know how to trouble shoot one of these cheep floating 5-blade heads in the future. Now I need a near-scale 450 size fuselage to suit...but which Confused


What about a Hughes 500E they have 5 blades and the 500 body for 450 is readily available the only visible difference is a slightly pointier nose on the 500E.
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Burgess
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PostPosted: Mon May 02, 2016 8:34 am
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Yeah, I had thought of Hughes 500, did hope to get an Align kit but they've been out of stock for a little while at Align-trex.co.uk. Just found one on ebay.com might have my name on it.



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Burgess
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PostPosted: Mon May 02, 2016 11:41 pm
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When I get the Hughes 500 fuselage I'll fit a shaft driven tail, may need to re-locate the rudder servo directly under the boom as with the Pro configuration. Also thinking of converting to a 22 volt system, higher volts lower amps ought to help reduce watts lost to heat.

I like the look of scale-like plastic blades, so I'm going to produce a two-blade set of semi symmetrical wooden blades out of beach and trial on a T-rex 450, if successful make another three and fit then to this.

I reset the Swash mix to A20%;E20%; P50%
and pitch and throttle curves
Pitch 50;62;75;87;100
Throttle 00;65;75;80;80

Found why one blade tip is lower than the others static or dynamic, the attitude of the stub feathering shaft is determined by the position on the pivot screw in relation to the O ring horizontal centre line, if a fraction above or below the angle of the blade root to tip will be up or down. The screw is a fraction above that centre line and that's why the blade is angled downwards. The pivot screw goes into a tapping, so will need to effect any adjustment via positioning of the O ring. Doing so with each hopefully will bring the stub feathering shafts to a common angle...This is a Men in Black pie problem....cherry pie I think.



I now have a choice of shims to determine the amount of ‘flap' movement. Also the od of the blade holder bearings are 9mm leaving very little flat in contact with the blade roots will fit some of those half-round Align spacers to increase contact area and stop the blade holders digging into the blade roots.




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