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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Need advice on a smallish 4 blade rotor head
10-15-2011 10:58 AM  6 years agoPost 1
Dirt Biter

rrApprentice

Naas, Co. Kildare, ROI.

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Folks,

One of the items I am including in my CH53E build is an as to scale tail rotor complete with the outboard pitch control. I spent countless hours at the drawing board figuring out the mechanics for a unit that I would get made to fit a standard torque tube tail assembly. I even managed to design the lever system for the pitch that would use a non-rotating shaft through the tail rotor drive shaft.

This morning I had an epiphany and realised what a dolt I was when all I have to do is get hold of a 4 blade main rotor head that would fit either a 5 or 6mm shaft assembly thus simplifying the whole design and save me a fortune in machine shop costs!

Any ideas as to something cheap but not nasty in that size range?

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10-15-2011 12:44 PM  6 years agoPost 2
Christopher J

rrElite Veteran

Kansas City, MO Californian lost in land of Oz

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Dont know about the 4 or 5 blade head that small, but regarding the pitch control from the outside why not use a Schluter tail gear box? The shaft was hollow, the control ran through it. Beats having to machine something. The input shaft will accept a coupler for a torque tube drive or flex drive.

Christopher J
same as I ever was
"Still all set & Flying the original"

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10-15-2011 02:03 PM  6 years agoPost 3
tracknoob

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Miami Florida

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If you can't find a Schluter tail, the Kalt Barons from 20 on up mostly used the solid-rod-through-hollow-shaft approach to tail pitch control too, and it really does make for a simple, easy to implement approach -- the 90 degree tail case and gear unit can be treated as all one piece, including the pitch control pivot and rod, so all you really need to do is hook up a linkage and go.

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10-15-2011 02:10 PM  6 years agoPost 4
Dirt Biter

rrApprentice

Naas, Co. Kildare, ROI.

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I have just spent 3 hours trawling through links for a Schluter tail gear box to find out that they are as rare as hen's teeth!

I am not that keen on it though as it is a wire push rod system and I would not be able to have the cruciform with the angled legs as per the real thing but it is a step in the right direction.
Another possibility is to modify one of the Trex TT tail units I have with new side plates to take a 6mm shaft and have it bored through to enable me to use a 3mm shaft with a bearing in the cruciform to give me a replication of the full size bird. Only issue would be the weight factor but it is a possibility to bear in mind.

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10-15-2011 03:01 PM  6 years agoPost 5
reaper31

rrVeteran

Littleton, CO, usa

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i have used a trex 450 shaft as a tail output shaft, they are 5mm, i would assume that any of the trex 450 rotor heads will work for you.
they can be head for about 100 bucks at various places. still cheaper than your regular 5 bladed tail rotor from century

Robbert De Bock

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10-16-2011 10:45 PM  6 years agoPost 6
Dirt Biter

rrApprentice

Naas, Co. Kildare, ROI.

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tracknoob,

The Kalt Baron 30 that I aquired from trillian (bless her!) has an inboard pitch control similar to that of the generics that are mostly available.

Unbelievably, I have found a clone supplier with 4 blade heads, inc swash, for $35. All I need is the cruciform from the head and with a few modifications, even though it might be cr*p, it should fit the bill. The only part that I will have to get made is the pitch actuator head.

The tail rotor diameter of the Flasher 600ESP I am using for the donor mechanics, using the supplied 105 tail blades, comes out at 356mm, whereas at 1/18th true scale the tail rotor comes in at 338mm so even with the slight increase in the tail rotor diameter it would look the part. Using 100 or 95mm tail blades would bring it in closer.

Most clone 450 heads return around an 80mm bolt pitch and a typical Align 600 tail unit comes in at 70mm for the bolt pitch so I should achieve the required scale appearance without to many problems.

Here is a sketch of the outboard actuator without the pitch actuating arms shown that I'll make or have made for the tail rotor. The bearing being held to the shaft by the external circlips and in the housing by the internal circlip. The wavy washer takes up any tolerance error and packing the bearing and grease pit before assembly should ensure no torque transfer to the stationary shaft that will pass through the tail rotor shaft and through the rotor assembly. I'll fit a phosphor bronze bearing sleeve to the top of the rotor head to keep it central as it will be lighter than a bearing in its place.

Peter Wales did warn me that I was looking for a headache with the detail I was wanting on this build so I have stocked up on Nurofen Plus!

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10-19-2011 11:35 AM  6 years agoPost 7
Dirt Biter

rrApprentice

Naas, Co. Kildare, ROI.

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It was back to the drawing board again and this looks like a goer for the outboard pitch control!
I am not the world's best technical drawing artist but these serve to illustrate the idea

Here I have designed the shaft drive and support for the extended tail rotor shaft. It will have more of a taper than this to match the original

How to drive the pitch control in and out? Took a bit of thinking but this should do the trick.

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