Lynx7s XX153. First AAC AH1

[Lynx7]

Thanks Colin and Mish. Colin, not had chance to reply to your email but will do very soon mate!

So, I've been pondering for a few days. I wanted to do more on this model seeing how its quite an iconic aircraft. I was debating whether to open a cowling and build an engine as I did for one of my AH7 a while ago;

I decided against that.

And have decided to build both engines

As you may see, the engine cowlings and how they open on XX153 are quite different from production Lynx. Current Lynx have quite a clever complete fold down engine cowl with integral platform on each side. With the prototypes, they were more akin to doors with little regard for the practicalities of servicing in the field and good access. Luckily the contours of the engine bay on the kit are the same (with a few minor mods) and as you can see from the above pic, I've already chopped up the engine bay.

Another interesting point to note is the exhausts. As you'd expect with prototypes, quite a few things change on each prototype and also each individual aircraft goes through a metamorphosis through out a test programme. If you look at the original exhaust on the yellow XW835, you'll see the exhausts are quite small and protrude out and rewards quite a bit. Each of the initial prototypes had different exhausts too (again, depending on when it was fitted during the test programme). XX153 had a variety of exhausts fitted during its time so its a bit difficult to tie down a particular fit. As it sits in Middle Wallop museum, it has the later type of exhausts fitted and I'm not 100% sure that they are any of the original exhausts. They may have just scribed newer ones on during restoration. As you can see in the above pic, I've modified the exhaust to represent the earlier fit (using early 70s photos as a ref) and opened up the exhaust housing too. I've used alloy tube (as I tend to do on each of my Lynx models) because its easy to ream out to a nice thin exhaust like profile and using a small amount of heat from a lighter, it will lightly tarnish it to a more accurate finish.

So I've given myself an extra bit of a challenge by building two engines. I've done it before and luckily still have all my ref pics and build pics from the AH7. I may build the basic engine and resin cast it so I have templates for future engines. Also makes it easier to build the second motor.

I will admit at this point that there are some details on XX153 that I will not be replicating accurately. Its only when you look closely at something you notice differences. One of those is the forward sliding fairing above the cabin. The prototypes had a 'turret like' rim on the forward edge as opposed to fully faired and the roof widows were rounded at their corners as opposed to square as per the current Lynx. I wont tell anyone if you dont

[AnonymousDFB1]

Go for it

[Wafu]

Your bloody mental you are.

Two scratch built Donk's

Milliputs ok to lick but PRC is better with a dash of MEK

[Lynx7]

Engine bays started. I started by constructing the engine deck floor using .5mm plasticard and deconstucted the engine bay doors. Because XX153s engine doors open differently, I modified parts of the kit engine bay. I used the top section, removed the rear part of the DC gen intake and outlet and thinned the egdes to give the impression of panels. I also removed the rear engine bay vent grills as the early Gem engines didnt have these. You can also see where I've constructed the rear bay bulkhead in front of the exhaust area.

Centre firewall just placed (lopsided) in the middle of the bay.

The lower doors were constructed using thin plasticard and ribbed using square section styrene.

And the start of engine 1 construction. Initially using brass and alloy tubing with the forward section inserted in to the exit holes from the intake housing.

I'll add accessories such as the DC starter generator and oil cooler assy then once all the main modules are complete, I'll cast the main engine. From that, I can then add the other ancillaries such as oil system, fuel system, governor and then dress it with all the plumbing and wiring looms. I will cover the engine bay walls with thin alloy foil and rivet as required.

[AnonymousDFB1]

Wonderful work, I'm loving all these mods

[Caerbannog]

Wow - great!

Rene

[Lynx7]

A bit more progress on the engine. The front is where the brass ring is and the rear is where the green tweezers are. The brass ring will sit inside the back of the intake housing on the kit.

I've used a combination of alloy & brass tubing, styrene rod and random bits of PE

I've got all the main components on now (DC Gennie, accessories plate, oil cooler, fuel and oil pumps and the free power turbine governor). Once I've sealed up all the little holes and gaps, I'll stick it in a mould and see how it turns out to cast. It may be a slightly complex shape for a cast but time will tell. I have some very fine mould solution. and a very low viscosity resin so fingers crossed it'll pull as much detail as possible. The thing that makes this engine is once all the plumbing goes on so I'm looking forward to that. As with the real engines, they are a snug fit in the engine bays.

[RNoAF Aerobatic Team]

Wonderful, but insane sense of detail.

[Col.]

That engine is a model in its own right. Cracking work.

[heloman1]

Cracking work there Tony, are these pics from your new phone? I see what you mean re the hinge line of the early drop down portion of the engine cover where the lower portion with the fire door was fixed.

Colin

[Caerbannog]

Blimey - this is amazing!

René

[AnonymousDFB1]

[palacefan]

WOW!

[Lynx7]

Getting there with the engine.

I've filled all the little gaps and holes where the latex moulding solution will have difficulty working round and will give it a light dusting of Mr Hobby primer prior to setting in the mould.

I initially used alloy section to make the oil tank (I wanted to keep it bare metal as per the real one) but it didnt prove satisfactory so I constructed it out of bits of styrene. I'll prob cast these as separate parts and put a suitable coat of stainless steel paint on and buff.

[AnonymousDFB1]

Impressive

[Lynx7]

Engine primed and ready for the mould

[heloman1]

Cracking work Tony, I do like your use of PE parts. Nice one with the Dzus fastener.

Colin

[PMC]

Looking fab! I am following this with great interest. The engine looks really good and I'm looking forward to see how the mould turns out.

My first every flight of any form was in a Lynx when I was a mere slip of a boy in the Army and for that reason the Lynx has always held a special place in my heart.

I have a 1:48 Airfix AH7 kit I was given for Christmas so this GB is giving plenty of inspiration!

Paul

[Lynx7]

Thanks Colin and Paul.

Engine now placed in mould casing and the solution poured (very slowly to prevent airbubbles)

I've drawn where the masters are and their orientation within the mould case. This assists when cutting the masters from the mould as it means I have a better idea where to cut and thus reducing damage to the master. As you can see, the master is at the bottom of the casing but once I de-pot it, I will cut along the bottom of the mould (and the bottom of the master) so any damage from the blade will be hidden. I will then use that cut as the injection port (now on top as the engine mould will now be upside down) to squirt the resin solution in with a syringe. This means that gravity as well as a bit of pressure from the syringe will allow the resin to penetrate in to the detailed upper area of the engine. The smaller object is the oil tank.

Straight after pour. Air bubbles are starting to push to the top. I leave the whole thing in a warm environment so it doesnt set too quickly and trap the bubbles. I leave it for about 24 hours. I've used Sylmasta 380 rubber solution on this occasion as its a medium viscosity solution. I sometimes use 370 or 390 which is more and less viscose. The higher the viscosity, the better it will run in to smaller detail but can tear easier. 380 is the better compromise of good viscosity but also fairly robust (important if you wish to reuse the mould over and over).

While I'm waiting for that to set, I decided to make some nose avionics detail. Its not going to be as detailed as my AH7 I did because you cant actually see a huge amount once the nose doors are fixed open. It just adds a bit more interest (plus I really enjoy making stuff )

Battery

I'll add a bit of wiring and some other random stuff later.

[heloman1]

Cracking on nicely Tony, love the battery bay and other bay.

Colin

[Caerbannog]

Looks great. Interesing idea with the drawn master location on the clear casting container.

Rene

[Lynx7]

Trial and error in the past, Rene!

Painted up the nose avionics area and placed in nose.

I'll add a bit more detail later but not really too sure the early aircraft would have had much kit in there anyway.

Dry fitted tail boom, skids and nose

The observant will notice I've cut the upper sliding fairing and placed it in to the forward position. Yep, I'm probably going to scratch the main rotor gearbox, hydraulics, control runs, AC gennies plus all the plumbing......Didn't I say right at the beginning I was going to keep this simple?

[AnonymousDFB1]

Wow, that's looking good

[Lynx7]

Thanks Mish.

More progress.

Cast the first engines this evening and am happy its a good mould and cast. There are a couple of bits of detail its not picked up but on the whole, it worked!

I've cast a couple more engines after tweaking the inside of the mould a bit (removing little bits of rogue latex) and they have turned out well too.

I'll prime them, spray a base bare metal/stainless coat then I can start dressing them with all the plumbing and wiring loom. A most satisfying activity as it transforms them so much.

As I eluded to before, I've decided to open up the forward housing too. Detail will include Main Rotor Gearbox, 2x hydraulic packs plus manifolds, reservoirs and plumbing, 2x AC generators on the forward face of the MGB, 3x hyd servos also on the front of the MGB and the control runs running along the top deck.

(Photo courtesy of Jens. Thanks mate)

Not quite as challenging as you may think because I will use my very detailed references of each sub system and build them up as modules.

The first thing I had to do was make up the MGB decking and upper roof area. On the kit, these are recessed but I needed to pad them out a bit. I used plasticard as bolsters underneath to get to the correct level then covered with appropriately sized thin styrene sheet.

Engine deck area dry placed too.

MGB mounting beams attached and the centre of the Z axis of where the main rotor will sit. This is very important as the top of the gearbox is usually attached to the sliding fairing on the kit but as you will see, I've chopped it off to furnish the top of the gearbox housing. I will need to ensure the gearbox sits at the correct height and the correct position so the blades sit in the correct place too.

Start of the gearbox. I cut thin styrene sheet to shape, did a bit or origami to make it look ok then filled it with milliput for strength.

This is the bit I chopped off from the sliding fairing and it will make up the top part of the gearbox. I need to blend it in to the top of the MGB.

You can see where I've modified the sliding fairing. The prototypes had a subtly different shape to the front (not pointy), no sight glasses for the hydraulics reservoirs and a different opening mechanism.

I need to attach the mounting legs to the gearbox and furnish it with oil pump, sight glasses and add the accessories gearbox to the front which will hold the 3 servos, hyd pumps and AC gennies.

Overall view of how its getting on.

Some of the early prototypes had extra struts fitted at certain parts of the test programme. This was due to excessive vibration at the tail (no change there then!). One of the photos I have of XX153 shows it with them fitted so thought I'd copy that too. I drilled .7mm holes in appropriate places then used .7mm brass rod with metal eyeball fittings I have in the parts box. Ironically, if you look at the non folding tail Lynx, these struts are still present but now under a fairing.

[crobinsonh]

Superb work - not that I would expect any less. You could certainly write and publish the definitive Lynx modellers guide