Absolutely awesome work Ken. What a fantastic idea! Loved the last build and really enjoying this one too. Your fabrication skills are astounding.

Keep up the good work,
Wij.

Originally Posted by heli_madken

Hi All,

Before I start this post I need to point out that what I have built DOES NOT FIRE ANY PROJECTILES!! it is designed to make noise and smoke only and I have given all due attention to safety.

Basicall, in my opinion, you cant build a large scale model of the HS129 B3 without at least trying to make a cannon that works

This is the result of 5 weeks obsession, I still have a way to go yet to perfect it but I am pretty pleased with how its come along. Basically I wanted the cannon to fire 5 shots so the first problem was how to achieve ignition. I had an idea to use the small charge found in party poppers, the type that you pull a string to explode.

I figured that I use could a strong servo for this, I went with HS5585 MH's which are rated at 17kg on 2S Lipo. I figured I could also use a servo to open and close the breach then gave some thought as to how it would all work together. I have had experience using a Picaxe 08m AXE024 Servo driver which I new would control the sequence of the two servos so went down this route.

So I set about the design which will all fit within the scale sized nacelle of the B3. I have designed it to be balance neutral, the magazine itself is right on the CG point, the 2S battery will be at the rear together with the electronics which counterweights the huge but lightweight alloy cannon.

The whole thing is self contained running its own RX and power supply form a seperate transmitter. Power is via 2S Lipo for the servos with a Ubec supplying 5V to the Picaxe. Safety is given by a RX controlled switch that only supplies power to the servos once the system is armed via the transmitter which will only be done during flight.

Couple of videos showing a few shots been fired in 'party popper' mode -

http://youtu.be/EKkx09dwqe8

And the action -

http://youtu.be/cJrmFEUIXDc

The idea is to make noise and shoot black powder paint from the front of the cannon to give the impression of smoke, I have a couple of issues to fix but will post another video once I have sorted showing the full action

Take it easy on me I know some will give me a hard time over this but I just had to make it!

Wow so awesome, well done, I doubt I could make something like that.

Mate that's absolutely fing awesome! I can't wait for you to build an A10 Warthog!

Looking back at the shots of the structure before any sheeting went on I have to say that your estimate of AUW ought to be right on the nail Ken... although now you've shown us the cannon that's going under the centre line I do wonder if you have enough strength between the carbon tubes through the wing centre section. I would be worried that the pressure on the upper wing spar would buckle it and lead to failure.
Do you have plans for that which we have not seen yet?

The underside ought to be no problem if the wing sheeting goes across the centre line continuous. That ought to withstand the tension just fine (so long as you don't fly her inverted!)

I normally am a bit reactionary about adopting the Metric System, but have done a rough conversion of my Stirling's vital statistics so as to compare with your Henschel... and it comes out pretty comparable. Just under 3m span and 9kg - and having now flown it for the first time all my anxieties about it having got too heavy are dispelled! Slow and majestic, it looks and flies just right - so I'm sure yours will too.

I am assuming you will be carrying all the power train for each engine in the nacelles to reduce the bending stress on the centre line as far as possible.

On the subject of the gun I have been having a chuckle at imagining the changing complexion of the bystanders if you fired the cannon in damp weather! I wouldn't want to be standing down-wind of a cloud of wet paint... but it would be an excellent way of weathering the underside of the model!

This is a stunning build Ken! You're clearly a man well-equipped and master of the technology!

Hi Thanks for the comments, it has been fun designing and building the cannon.

Dont worry I have already thought about the weight issue, I am adding doublers to the spars and the underside of the region where the nacelle joins the fuselage is clad with 1.5mm ply. In addition I have designed a box structure that both adds strength and acts as a firewall.

Batteries are in the engine nacelles, my main concern though is still with ground loops causing damage to the cannon so I am building in a point of failure for the nacelle that will be easily repaired.

In all the cannon is not that heavy so I think I am still on target to have a low wing loading.

I plan to design and build the rest of the nacelle structure over the next few days and do some more experimentation on the firing mechanism but I have run out of party poppers and I think the local supermarket are getting suspicious

German newsreel footage from back in the days...

Luftwaffe´s Henschel HS129 Anti-Tank aircraft (Sep 1944) (1 min 29 sec)

forgot to congratulate you on this build.
awesome !

following with envy...
Frank

So after my cannon folly its back to building the plane itself, wife was out yesterday so had a full day Lot of work to get the combined motor mount, battery and retract frame cut out and assembled, was actually a sod to put together but got there in the end.

Cannon is mounted in its frame just waiting on some bits then will wire everyting permanently and do some testing

Next up is to finish the sheeting on the engine nacelle then repeat the other side

Very nice Ken!

Fabulous build!
subscribed

Thanks for the encouragement it is really appreciated

Just a quick update finished the sheeting and rough sanding on the top surfaces of the left wing including the flat topped area of the engine nacelle, I will add details to this during the last stages of the build.

Moving on to the right wing now

Looking real nice!

Just wondering out loud... do you think the pilot could hear the guns when fired?

James

I would imagine so, the cockpit was incredibly cramped, many of the flight instruments were outside of the cockpit on the engine nacelle and the gunsight was on the nose so I dont think they thought about creature comfort!

Originally Posted by Deuce

Looking real nice!

Just wondering out loud... do you think the pilot could hear the guns when fired?

James

Lol ye think

I just ran across your new build here tonite. WOW!! I'm almost speechless (it will never really happen)-hehe.
Incredible build skills here, way beyond anything I'll ever accomplish. The cannon is just too much!! \Love it.. She will be a beauty for sure.
I'll be watching this come together, its like a watch, stunning.
Watch for unique concept, three of us are building 81" Mosquitos to fly in formation next summer. All electric. 5.9kgs auw (hoping), custom LG etc.
Thread should start very soon. Doug Bartley