HAC450H5H - 5 Blades Multibladed head for 450Size - RC Groups
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Aug 06, 2008, 11:54 AM
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HAC450H5H - 5 Blades Multibladed head for 450Size

I recently purchase a HAC's multibladed (5 bladed) head for my TRex450 scale. It is going to replace/use in my MD500E

The packages comes without any user manual at all. Just bubble wrapped.

It comes with everthing from swash plate and above (except blades of course). Including a compatible main shaft.
Visual inspection looks ok. All linkages are already assembled. All screws appeared to be in loctite (green color I think) except there is one linkage ball at the blade grip came loose. The assembled configuration is in leading edge with main rotor spin Clockwise. The linkage from swash to blade grips angle (or phase angle) is NOT in 90Degree. It is around 45Degree. {See picture}

It come with only one swash plate follower/driver linkage {see picture}. It will be good if it is at least 2 (for stronger holding and as well as balance in weight when spinning)

It is a rigid head design where a M4 (or 4mm Allen screw) is use for the spindle/link for the blade grip to hub. {see picture}

The swash plates that come has its inner swash plate a bit smaller than normal TRex450 size. The swash plate design as a flawed/bad design in such a way that the bottom hole for the main shaft way too small diameter. This restrict the maximum tilting angle of swash plate can go before the bottom hole surrounding hit the main shaft. {See picture}

Not happy with the above flaw, I fix whatever I can.
1. Apply new loctite on each blade grip's linkage ball.
2. Widening up the swash plate bottom hole using pen knife and slowly cut the surrounding to make it bigger diameter hole.
3. Also replace the compatible main shaft to Align main shaft. Don't trust their main shaft

Because I going to use it for my MD500E, I reconfigure it to be leading edge when spinning Counterclockwise. I flip all blade grips to 180 and also flip the swash plate linkages. I readjust the phase offset to be in 90Degree as well.

After adjusting the linkages for proper blade tracking, I spin it up. It appeared everthing is in straight line. The hub looks centered and the blade grip to hub are in perfect 90Degree. They done a good job producing a perfect alignment even though their 30/50size multibladed has been badly reviewed due to poor design/manufacturing.

The stability is also there as well. That mean it is possible to fly using this multibladed head without gyro assist BUT remember that flying multibladed is different from flying flybarred+paddles configuration.

Due to it is rigid head (which I don't like), when spinning, when u apply cyclic, the rotor disc try to tilt BUT it cannot tilt due to rigid head. This causes the whole head to shake/vibrate. When u release cyclic/return to neutral, the vibration is gone. The vibration can be visually seen on the swash plate as well. Using flexible blades (ABS) doesn't help reduce/eliminate the vibration as well.

For me, I prefer to fly with cyclic gyros, I also install 2 gyros as well. It is GWS PG-03 that I have for quite a while.

Do a test hover in living round and it appeared to be stable. Test flight outdoor also appeared to be flyable. Due to it has more blades, it is actually more sensitive to wind. Flying in windy condition can easily cause the heli to sudden and frequent drop or increase in altitute. Again, due to rigid head, each time when I apply cyclic, I can see the heli vibrate a with its blades goes out of track...until I release the cyclics.

No happy with the rigid head, I decided to modify it to have some sort of flapping hinges. Bench test spinning and now, there is no vibration/shake when I apply cyclic. The rotor disc tilt as I want it to when apply cyclics. I still in the process of further testing it. If everything runs good, I will then put it back to my MD500E fuselage.

Last edited by Super_Hornet; Aug 06, 2008 at 12:06 PM.
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Aug 06, 2008, 12:19 PM
Registered User

I already modify it with some sort of flapping (and lead/lag) hinges. Notice that if the flapping hinges is soft (weak damper), it tend to cause sudden pitch changes fluctuation when using heavy blades.

I make the flapping hinges damper stronger/stiffer a bit and now much better.

Today, when I was debugging the rotor head, I notice the each time when I increase the pitch, the inner swash plate get twisted a bit and causing the pitch changes to "lag" a bit and this also changes the phase angle abit. All this is due to the swash plate driver/follower is only have 1 linkage. One swash plate driver linkage to hold/fight against 5 blade grip linkages is too much for it to handle.

Thus, I decided to modify it again. This time I make the blade grip linkages to be in 90Degree downward (or straight line). By doing so, I solve the inner swash plate get "twisted" around every time there is a pitch changes but introducing new problem to solve.

Because of having blade grip linkages to be 90Degree in this rotor head, the phase angle is LESS than 90Degree. That mean I need to have some phase angle offset. Due to I do not have Helitronix mixer to do the phase changes (or the eCCPM mixer I use do not have phase change), I need to create some mixing on the TX.

While playing around the TX mixing, I notice that I can actually DO NOT require TX mixing at all. What I need to do is to change/connect the channel to the 3 servo in a different arrangement. By doing so, I manage to make the blade grip linkages with straight line AND do not require phase angle offset Even my gyro position do not require to change at all!

Just finish doing hovering test in living room, It is much stable AND do not have sudden collective punch up. Next step is to test outdoor.

Due to my camera's battery is completely flat right now, I can't take any picture of it. Wait till the battery is fully charge, I will try to take some more picture of it.

Aug 06, 2008, 03:11 PM
US Navy AT2 1987-1995
USNAviationjay's Avatar
this a different head the the Lightning Heli 5 bladed?
which one did you use before?
Aug 06, 2008, 07:55 PM
Registered User
This is the first commercial multibladed head that I ever purchase

I not sure whether HAC and Lightning is from the same company or not. Here is the link:
Aug 06, 2008, 08:13 PM
Team Mulikow
Gino CP's Avatar
What do you mean by "rigid head" and "flapping hinges?"
Aug 06, 2008, 08:31 PM
Registered User
Rigid head => Blade grip to rotor hub cannot flap up/down and lead/lag sideway. In other word, the blade grip is firmly bolted to the rotor hub.

Flapping hinges => The blade grip can flap up and down as if there is a hinges. Just like your door can swing over the hinges.

Flapping only or Flapping+lead/lad is commonly found in full size helicopter with multibladed head.

Rigid head in real/full size heli does exists but their blades is design to flap instead.

Two bladed heli is commonly use teeter design.

Aug 07, 2008, 11:31 PM
Registered User
The straight linkages and different servo channel arrangement works. {see picture}. Remember this configuration DO NOT REQUIRE any programming mixing on the TX. This is achieve by rearranging the channel that connect to the 3 cyclic servos. Due to no mixing is required on the TX, the cyclic gyro remain the same position.

The straight linkages does encounter situation whereby the swash plate follower/driver is very very close to one of the linkages. But on full collective and with cyclics movement, it does not cause any problem. So that should be OK. {see picture #2 and #3}

Successful outdoor test during Thursday nite. Manage to test 1 pack before heavy rain It turn out to be much stable than previous configuration.

{ The rotor head configuration shown on the pictures are in Counter Clockwise rotation with leading edge controlling. Top button was temporary removed }

Aug 07, 2008, 11:33 PM
Registered User
Below show how the blade grip can flap up and down

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