Last year I ordered a Blackhawk kit from Mario Andres at FRH in Germany. The kit duly arrived and it was enormous. I set it to one side while I finished other things and then a little later some more parts arrived from Mario with the explanation that the original design wouldn't work and needed to be changed.

I finally got started on the model last week, and the first thing I did was to investigate the tail system. I worked out where one failing was and then fixed it, and then I mounted the tail rotor gearbox so it was at the correct angle to get a shaft down to the intermediate 135 degree gearbox at the base of the fin. Therein lay the problem. Having tipped the shaft forwards, I had tipped the output shaft backwards, and even though I spent 3 days fumbling around with this thing, I couldn't get it right.

THIS IS A HELL OF A WAY TO START BUILDING A HELICOPTER!

The other option is to use a cable drive and this is what Mario recommends, but I don't like cable drives. I don't like Broccoli and I have never tried that either.

I spent another sleepless night pondering this problem and came to the conclusion that if the output shaft was in the correct alignment, what was underneath it didn't matter, so I went back to the gearbox arrangement again and had another look. I decided that the mounting plate had to be aligned so that the drive shaft from the gearbox went directly to the intermediate gearbox and the input to the intermediate gearbox had to be exactly aligned so that it went through the center of the mounting hole in the bulkhead flange.

I mounted the tail rotor gearbox with a shaft on it and the intermediate gearbox with another shaft on it and lined everything up.

This the gearbox mounted up to the baseplate.

It still doesn't look right until you look directly down at it.

Now you can see the tail rotor is parallel to the fuse and at right angles to the fin, even though it is all tipped over by 20 degrees.

I fixed the tail rotor gearbox in place with a couple of metal brackets and made up a 6mm stainless drive shaft to the intermediate gearbox. This was fixed in place with another pair of brackets and some JB weld.

The last job in this area will be to put some PFM on the other side of the center bearing, on the back of the gearbox and over the aluminum brackets, and around the wooden plate supporting the tail rotor gearbox. If there is any vibration in these areas and the JB weld breaks away, the PFM will absorb the vibes and keep everything in place.

I spent a week looking at this thing, and it just didn't look right. More and more I was coming to the conclusion that the input shaft to the final gearbox had to be vertical and if it wasn't the 110 degree angle would tip the output shaft one way or another. Although the previous photos make it look as if its ok, this one shows my dilemma.

So, I tore the mounting plate out and refitted it so it was horizontal, which was quite a difficult thing to do as there are no straight edges to reference to on this model. Except one that is and that's the piece under the angle portion of the fin. So, I fixed up a laser level and started laying out masking tape strips so I could gauge when everything was level. Now I had 2 choices. Back to the cable drive or try and figure out a way of doing a shaft drive. I was pretty sure the full size machine didn't use a cable so I tried to figure out how they did it. I came to the conclusion that universal joints were the answer. I found some on the Smallparts website. They had a torque rating of 20 in lbs which I figured would be enough so I bought some to play with.

The problem soon became apparent that the angles were too great and although there was a no speed rating on the UJ's, I was sure they weren't going to do 5000 rpm around any sharp corners. I thought of daisy chaining them, but quickly discarded that idea when it became obvious that each one would need to be supported in 2 bearings. Then I tried the spare 110 degree gearbox I had with the kit, but it was too big, but it did give me an idea and I found a Robbe 135 degree gearbox in the bottomless junk box. One of the input shafts was soon replaced with an off the shelf Vario coupler which coupled it to the tail rotor gearbox and a brass shaft was made up which had 4mm at one end to go into the Robbe gearbox, and the other end was left at 1/4" but with a big flat on it. This slid nicely into the first UJ. The other end was coupled to a piece of 1/4" stainless tubing which was cut to length and fitted into the bottom UJ

An adaptor was made up to reduce the 1/4" tubing to the 5mm input of the original 135 degree gearbox. I had weighed all of the parts thinking I was going to have a really heavy tail, but in fact the weight was halved to 200gms from the cable which weighed 400gms

Watch this space

Running the system up was a success! I got the tail rotor up to 6000 rpm with no mega vibrations and left it there until the battery went flat. It ran much smoother afterwards so the gearboxes have had a little "run in" session and I am much more confident this will work now. The next job is the tail rotor pitch control and again I immediately ran into a problem. The Robbe gearbox was in the way so the push rod couldn't get to it. I flipped the pushrod mount over and mounted it on the other side of the gearbox and that put the pushrod at the front of the fin where I have plenty of room

The pushrod from the servo goes to a piece of fiberglass mounted on bearings and fitted into the tail boom.

The kit comes with a mounting plate for the two servos to be fitted into the tail boom so this was made up and the two servos mounted with their push rods. The second on is for the horizontal stabilizer which can move up and down.

When it came to fitting the tail to the fuselage, the servo was hitting the fuselage flange so I pulled it out and swapped it for a 9550 which is a low profile wing servo with the same footprint as a normal servo. Its the only one like that, all others seem to be 6mm wider and wont fit in the holder

Now I have to mount the rear wheel support formers and then make sure everything is solid with liberal amounts of PFM and JB weld

Having got the rear end done, a quick check showed the tail drive shaft was not going to line up with the turbine and a universal joint was going to be needed and so the excess was cut off and a new coupling fitted to the drive shaft

Now its time to look at the main tub, and the kit is supplied with a ton of woodwork all of which is interlocking. I decided to dry assemble it all on the bench before even trying to get it into the tub.

The front 2 panels are floors with a rim around them which fit under the main chassis to make it easily removable. Isn't that a nice touch? The areas of real interest right now are the main wheel suspension points, which are the wood piece to the left with the blind nuts and the metal piece in between the two vertical formers on the right

The oval hole and the square hole in the tub show where the suspension arms come out of.

These are the two parts in question

The suspension arms have these large couplers mounted on them which will need to have a hole cut into the bottom of the fuse to clear them, and they are nothing like on the full size. They may have something to do with the Firehawk and the belly tank, but I'm not using that so I need to change them

These offending parts have been epoxied in place and an application of heat soon releases them

A lot of time on the lathe and mill made up these simple couplers which are more in line with the real ones. The reason they took a long time was that I spent all day making one major part and then ruined it on the last operation. This time, I did the last operation first

This is the fully assembled suspension leg

The next problem is the top mount inside the tub. This is how it is supposed to be.

The wooden shape lies nicely up the side of the fuse but that means that the metal piece will need to have a hole cut through the fuse and the vertical suspension unit will all be outside the tub. That's not right and a slot would need to be cut into the fuse to clear it severely weakening it. I am going to move the top mount so it is inside the fuse and realign the leg so it comes out of the correct hole in the lower part of the tub.

This is it loosely assembled and roughly in the right place.

Now she is up on her wheels I can see how everything lines up. The woodwork is very tight and will need trimming to get right and have everything properly in alignment

Boy, this thing is big

The next thing to do is to fix the landing gear in place. This requires a bit of juggling as the fore/aft location is defined by the parts which come through the wheel sponsons and the uprights define the position of the mainmast! The woodwork is a jigsaw puzzle in which all of the pieces interlock and need trimming to fit. The panel which holds the turbine is located by the maingear uprights

The uprights are held in place by copious quantities of PFM which will have a little "give" to it and get have enormous strength where needed.

Next comes the interior deck which is the last ditch support for the mechanics to the fuse. It is glued over the chassis and will be epoxied to the side of the fuse. 2 panels are also fixed to the top of the fuse to take the top support for the mechanics

The yellow wires are pull throughs for the servos and lights to get to the back of the model. Next comes the supports for the front of the landing gear and the cockpit floor. I have decided not to use the fuel tank supplied with the kit, it wont hold much and will be a pain to fit. 2 Vario tanks on either side of the main mast will do for starters until I can see how this bird sucks up fuel and then I'll decided exactly how the tanks are going to be done.

Just a few more wood parts to fit. Firstly the supports for the landing gear

And the support for the cockpit floor. Lots of PFM to fix it in place and then its a whip round everything else with PFM to make certain everything is rock solid.

Finally the cockpit floor base fixed with CA with PFM underneath

And the cockpit floor fitted loosely