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HomeAircraftHelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › Alternate feathering shaft / modded insert thoughts
12-01-2011 07:15 PM  6 years agoPost 1


London, UK

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I have been tweaking the rotorhead on my Futura lately
to get it flying more like I want for FAI stuff and a
thought occured to me.

By having some longer inserts made two things could be
accomplished; 1. The use of an alternate and more readily
available feathering shaft. 2. The spacing of where the
O-rings support the shaft would be wider so it would limit
the teeter range of the feathering shaft as well as effectively
stiffen the dampening on teetering movement without
harder o-rings.

I am going to see about having a pair made as soon as
I find the best feathering shaft to base it on. Perhaps
the Raptor 90/720 as it is also 8mm but I am not sure of
the length at the moment.

Anyway, I'm just thinking out loud here and curious if anyone
has tried something along these lines and / or if anyone
would be interested if I have someone turn out a few
pairs. (I guess I would have them done with space for
3 o-rings as that would probably give the widest range
of tuning options).

12-01-2011 08:57 PM  6 years agoPost 2
Heli 770



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Raptor/G4 feathering shaft length, 118.5mm.

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12-02-2011 12:33 AM  6 years agoPost 3


London, UK

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Thanks for the info on that. It looks like the stock Robbe
feathering shaft is 99mm so that extra 9mm ish on each side
would probably make a noticeable difference.

12-03-2011 06:07 PM  6 years agoPost 4


London, UK

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Someone has volunteered to make up a pair of new
inserts. So next week I'll post off to him a pair of
the stock ones along with a hub.

It should be an improvement in rigidity and also the limited
ability of the shaft to teeter and twist should make it
just that bit more precise. It also means that the rotor
disc will increase a bit, so 690s will now be effectively
creating the same disc size as 700mm.

As a comparison, the stock Robbe hub with inserts is a
total of 44mm wide, the Avro head is 70mm wide.

The new inserts should make the total width about 62mm

12-22-2011 03:53 PM  6 years agoPost 5
trillianrrVeteran - London, UK - My Posts: All  Forum  Topic

Got the new parts now
OK, today I received the new parts.

Here are the new inserts with one of the stock inserts
in the pic for comparison (the new ones are 9mm longer
on the outer portion). In the foreground is a spacer
for the mixer arm mounting onto the grip.

Here is the feathering shaft I am using for this project.
This is the Raptor 60/90/G4 part and is 118.5mm long. The
stock shaft is on the left for comparison (approx 18mm

Here is a dry fitting. Note that the spacer between the
grip and mixer arm is less than the 9mm of the new inserts.
This will introduce a bit more correcting delta but at
the same time the feathering shaft is now more limited
in how much it can teeter. I'll see if the effect is
good or bad or not noticeable and can always add another
spacer and longer bolt.

Here's something I discovered when choosing bits for the
new head; There are two sizes of flybar control arms. I
didn't realise this. The smaller of the two is going
to give more deflection of the flybar and thus faster
response so I am using two of the smaller arms.

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HomeAircraftHelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › Alternate feathering shaft / modded insert thoughts
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