Thunderbird 3 Build

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Aquaman33
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Thunderbird 3 Build

Postby Aquaman33 » Mon Jan 06, 2020 4:49 pm

I have been planning this build in my head for several years and I have decided 2020 is the year I'll finally get it built.

I have collected a stack of reference material, but much of it is contradictory, so building a faithful scale replica is tricky. But I hope that mine will at least be instantly recognisable. I will exaggerate the length of the body tubes a little to make it more stable.

There are dozens of different versions of Thunderbird 3, but they basically fall into 3 categories.

The classic versions which first appeared in 1964 in the original TV series and remained largely unchanged until the 1990s.
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The finned versions that appeared in the 2004 live action Thunderbirds film.
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The rectangular booster versions that appeared in the 2015 remake of the TV series.
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I have great childhood memories of the original TV series, so I am going to build the classic version.

But having decided to build a classic version there are still loads of decisions to be made about the details. I could write a book about the various anomalies, but I'll just give you a few examples:

The location of the black stripe on the nose:

Does it go through the T?
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Through the H?
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Or above the lettering?
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And the white docking ring:

Does it have horizontal markings?
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Or vertical markings?
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And what colour is the paint between to cooling fins?

Blue?
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Or red?
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So far my favourite reference materials are these photos of a 1991 Martin Bower model that was built to appear in a Thunderbirds comic. This model is currently for sale on the Prop Gallery's website, where there are lots of great photos. http://www.thepropgallery.com/martin-bower-thunderbird-miniature

I think I will use this model as my main inspiration.

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But even this model has some anomalies. For example the top of the docking ring changes from white in some photos.
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To red when it appears on the cover of the 1991 comic.
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Finally I really like this photo of the simple Corgi model as its a good clear reference for taking measurements.
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Time to start building.

Thunderbirds are go!
Last edited by Aquaman33 on Mon Jan 06, 2020 5:00 pm, edited 1 time in total.

joeman
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Re: Thunderbird 3 Build

Postby joeman » Mon Jan 06, 2020 4:53 pm

My son likes the look of your project. So do I

Looking forward to seeing it progress.

Joe


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OverTheTop
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Re: Thunderbird 3 Build

Postby OverTheTop » Mon Jan 06, 2020 6:58 pm

Definitely looking forward to seeing this build :)
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Aquaman33
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Re: Thunderbird 3 Build

Postby Aquaman33 » Mon Jan 06, 2020 10:23 pm

Thanks Joeman, Joeman's son and OTT.

I appreciate your enthusiasm.

Hoping I can meet expectations.

:D

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Re: Thunderbird 3 Build

Postby Aquaman33 » Thu Jan 09, 2020 4:25 pm

It wasn't easy deciding how big to build this, but in the end it came down to availability of body tubes.

The rocket can be broken down into 3 body tubes:
- Aft BT is the largest and has the boosters attached.
- Mid BT has the cooling fins attached.
- Fore BT has the docking ring and the booster arms attached.

This cutaway diagram clearly illustrates the 3 body tubes:
Image

After taking measurements from various photos and drawings I established some average dimensions.

The Mid BT needs to be 70% of the diameter of the Aft BT and the Fore BT needs to be 49% of the diameter of the AFT BT.

Thanks to a happy coincidence Officeworks sell mailing tubes in 3 sizes: 90mm, 60mm and 40mm.

The actual external dimensions of these tubes are:
90mm = 93mm
60mm = 62mm
40mm = 43mm

So if we take the Aft BT (93mm) as our reference point then the Mid BT needs to be approx 65mm and the Fore BT needs to be approx 45mm. I plan to use 3d printed cylinders over the tubes to add details (hatches, pipework, panel lines etc.) which will bring them up to almost exactly the right diameter.

Total cost of all 3 body tubes $10.12 and I will have loads left over. You gotta love the flexibility of custom 3d printed nose cones and transitions.
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These tubes are slightly heavier than "proper" rocket body tubes, but they feel really strong and the finish is excellent.

Once I had established the body tube diameters I was able to work out all the other dimensions:
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I have rounded up the length of all the tubes and transitions to add a bit of stability. I may add more length after running some simulations.

565mm long is a little shorter than I hoped, but hopefully it will be small enough and light enough to fly at our club's low/mid power launches.

I haven't decided on the motor mount yet, but it will be either 29mm or 38mm.

My biggest concern with these dimensions is making space for the parachute. The fore BT has an internal diameter of just 40.2mm and I will probably need to attach the booster arms "through the wall". So the parachute may need to be at least partly housed inside the nose cone.

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Re: Thunderbird 3 Build

Postby Jim-K » Fri Jan 10, 2020 1:13 am

I’d be careful of the forum rules. I’m pretty sure that “combination chemical and ion propulsion” powered by “fusion reactors” will count as experimental rocketry. :shock:

Aquaman33
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Re: Thunderbird 3 Build

Postby Aquaman33 » Fri Jan 10, 2020 9:01 am

Jim-K wrote:I’d be careful of the forum rules. I’m pretty sure that “combination chemical and ion propulsion” powered by “fusion reactors” will count as experimental rocketry. :shock:


Thanks Jim. Good point.

I should have pointed out that i will be using a more traditional method of propulsion.

:D

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Re: Thunderbird 3 Build

Postby Aquaman33 » Fri Jan 10, 2020 11:30 pm

The middle section of the rocket needs a lot of cooling fins and I didn't want to glue these on individually. So I decided to design a 3d printed sleeve, with the fins already attached. This sleeve will be glued over the body tube. The idea being that the cardboard tube provides most of the strength and the sleeve provides the surface details. This is the same concept as the Estes Saturn V kits.

Having decided to make a sleeve for the middle section I thought I may as well make them for the fore and aft body tubes as well.

I am only just learning Fusion 360, so these designs have taken me a while and required a lot of trial and error.

Each sleeve has an internal diameter 0.5mm larger than its corresponding cardboard tube. This will allow for a little shrinkage and room for some epoxy.

It seems that every model of Thunderbird 3 has slightly different surface details. The versions in Comics, publicity posters, TV and film all have different details. So I decided to just go with some simple details that are influenced by various different versions.

While my details are somewhat random, I repeated them all 3 times around the body. So it will look similar from all sides (unlike the model in the TV show).

Aft sleeve with recessed and raised hatches and panel lines:
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The white number 3 will go in the middle of the center panel.


Another angle of the aft sleeve showing the fin cut outs.
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My plan is to attach the fins through the wall and to fillet them to both the cardboard tube and the 3d printed sleeve. So the cutouts are slightly oversized.


The mid section with cooling fins.
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I think most models have 18 fins, but I decided to go for 15 to reduce weight and drag, and to make it less crowded. Had to be a number divisible by 3 so they align with the booster fins.


The cooling fins normally have a straight connection to the body, but I added fillets for strength.
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Top down view.
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I made my cooling fins slightly smaller than scale so that they don't protrude beyond the diameter of the aft body tube. This will give me the option of using rail buttons without the cooling fins clashing with the rail.


The fore body tube with cut outs for the booster arms.
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The flange near the top of this image is where the docking ring will sit. I decided to design and print the docking ring as a separate piece, for ease of printing.
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Now its time to warm up the printer.

Aquaman33
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Re: Thunderbird 3 Build

Postby Aquaman33 » Wed Jan 22, 2020 8:26 am

I printed the aft sleeve. This was my first time printing PETG filament, so I am very pleased with the result.

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The definition and detail is excellent and the layers are barely visible. After a light sand and a little filler primer it should be fine.

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Re: Thunderbird 3 Build

Postby SpaceManMat » Thu Jan 23, 2020 9:52 pm

Looks real nice, any tips for post processing 3D printed material?
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Aquaman33
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Re: Thunderbird 3 Build

Postby Aquaman33 » Fri Jan 24, 2020 3:11 pm

SpaceManMat wrote:Looks real nice, any tips for post processing 3D printed material?


No tips unfortunately. I wish I had some clever ideas, but I think it will just be good old fashioned sanding and then a few coats of filler primer.

I like this stuff from Super Cheap Auto:

Image

Aquaman33
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Re: Thunderbird 3 Build

Postby Aquaman33 » Fri Jan 24, 2020 3:22 pm

A nice snug fit on the body tube. Fin alignment should be a piece of cake with these cut outs.
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Because the sleeve was a 16 hour print I first printed this test piece to check the fit.
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I am unable to break this ring with my bare hands. So PETG seems to be very strong and quite flexible (according to my very unscientific test).

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Re: Thunderbird 3 Build

Postby Aquaman33 » Thu Feb 06, 2020 6:44 pm

I made a little progress this week.

This photo of the mid section was taken about 10 hours into a 16 hour print.
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The heat sink fins were printed with just 20% infill to keep the weight down.

All 3 body tube cylinders. Over 40 hours of printing.
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A close up of the forward body tube. The details came out really nice.
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And all three tubes weighed in at a respectable 205g.
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My original plan was to build an internal frame from cardboard tubes, but the 3d printed tubes have come out a lot stronger than I anticipated. So I am considering reducing the amount are cardboard inside to bring the weight down. I will still use cardboard where extra strength is required (eg. where the through-the-wall fins mount to the body tubes).

I think I will go for a 29mm motor mount. I don't think 24mm motors will get it off the rail fast enough and 38mm would be too big and heavy. It feels like an E, F or G motor rocket, so 29mm makes sense.

Next job is transitions.


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