Space Shuttle Launch Pad 39A with Challenger STS-6

[roma847]

Hello everybody,

 

it continues with the construction of the small Astrovan for the Diorama, and since it is really tiny, extreme caution was required in all further steps.

 

After I've cut out the roof, I've carefully pre-scored the fold edges and cut out a cardboard insert for stabilization so that I ever had a chance to glue the tricky roof together.

 

 

For the same reason, I did without the paper wheel mounts and instead glued in small Balsa blocks to make it easier for me to glue the wheels in place. 

Then I glued the wheel disks to the punched cardboard disks, the edges of which I blackened beforehand. 

 

 

Following I've glued in the roof reinforcement, which was a pretty stressful and tricky action, especially on the side edges, and took some time.

 

 

Before gluing the wheels in place, I thought about the best and, most importantly, the safest way to realize it, since the unstable and extremely sensitive bodywork should be handled as little as possible. And that's where I still came across my scissor tweezers, with whose help I could grab the Balsa blocks and put the bodywork on its side, 

 

 

which was a great help when carefully gluing the wheels and lastingly protected the bodywork.

 

 

Before gluing the roof on, I wanted to glue the tiny fans together and then glue them on. But since that could end in a fiasco,  

 

 

I've cut out small cardboard cores around which I could just imagine gluing the bizarre structures ...

 

 

But maybe I have to do without the adhesive folds and cut them off ...

 

I didn't think it was possible before that the construction of this tiny paper Astrovan would become so complicated,  

 

so let's take a look ...

[roma847]

Hello everybody,
just good that the message in my fortune cookie has bolstered me up appropriate courage.

 

 

The small fans on the roof were a stressful undertaking already, whose gluing around the cardboard cores I still succeeded after a few unsuccessful attempts, after having removed all glue folds. I first glued the cardboard cores to the underside of the roof and let it dry briefly. 

 

Then I've laid each fan on the roof, held it from above with the tweezers, and then dabbed the side walls one after the other with a mini droplet of glue at the acupuncture needle and and glued, which was quite cumbersome and also sweaty under the Headset magnifying glass ...

 

Then I worked on the front bumper, for which I used Styrene (0,25 mm), which could have been a bit thinner, but this goes through now!

 

 

Before gluing the roof on, I glued a Balsa strip at the upper edge of the bodywork to stabilize the walls. And nevertheless I had to treat this fragile paper structure like a raw egg when gluing the roof on.  

 

After the glue had dried, the small rear bumper stubs were glued, which of course could not be missing. And after the front headlights and the side mirrors had also been glued, the final inspection could finally take place, which was actually positive and can be seen.

 

 

And the comparison with the large Van model (1:48) shows in an impressive way how small this Mini Astrovan (1:160) really is, which now also fits with its NASA Worm logo with my STS-6 Diorama.

 

 

All in all, the construction was an attractive, but at the same time demanding task, a real Challenge, so to speak!

 

And since I've meanwhile found pleasure in the Pad vehicles, I also still got the idea to include the Payload Canister Transporter into my fleet, which can at least partially be seen on this STS-6 reference photo when loading the RSS Payload Bay, a thought that has been going through my head for some time, cause this transporter is an extremely interesting and extraordinary special vehicle ...

 

Source: retrospaceimages.com (STS-6)

 

And on this picture one can see the transporter leaving the Vertical Processing Facility, in which the respective payload is installed into the upright standing Payload Canister.  

 

Source: retrospaceimages.com (STS-6)

 

For this sub-project, however, I still have to do some research in order to gain more clarity about the construction and nature of both components.

[roma847]

Hello everybody,

 

unfortunately I've remembered these two original photos from the STS-6 on my Reference CD (J. L. Pickering - retrospaceimages.com) far too late, after chasing other photos for a long time, which one can definitely find on the web, like this very nice photo here from the NASA Media Archive, on which you can also study the details of the transporter very well in the XXL zoom, which you need for scratching, as long as one takes it a little more exactly, like me.  

 

 
Source: mediaarchive.ksc.nasa.gov

 

However, with this you still don't have the main dimensions (LxWxH), which you absolutely need to be able to estimate the size of the transporter and of interesting details, at least as long as you don't have drawings ...

 

But then you also still have to know that this is a picture of the two transporters from the manufacturer, the KAMAG Transporttechnik GmbH in Ulm, which were delivered to NASA in early 2000 as the successors to the 20-year-old Payload Canister Transporter System.  

 

Here are two photos of the arrival of the transporters, on which one can already see many important details,

 

Source: mediaarchive.ksc.nasa.gov

 

Source: mediaarchive.ksc.nasa.gov

 

so inter alia, that the transporter has 24 wheels, which makes it clear that I will have something to do when scratching, which, as is well known, excites me all the more.

 

However, one must not be dazzled by these great photos, since it is not yet clear how small or tiny some details in 1:160 might be again, see Astrovan.

 

But since I'm only interested in the 1983 transporter, used at the STS-6, I had to keep looking first and then have found at my friend James MacLaren, what I was looking for, who describes the Payload Canister Transporter of the time on his Website in words and pictures, when he worked from 1980 to 1985 during building the second pad, Launch Pad 39-B.

 

 

Source: 16streets.com/MacLaren

 

And as you can see, the transporter at that time looked a bit different, 

 

Source: 16streets.com/MacLaren

 

so I had to do some more research first.

[roma847]

Hello everybody,

 

in order to get usable dimensions for the scratch-building of the Payload Canister Transporter, I had to open up other sources, which took some time. For this I researched the Proceedings of various NASA conferences in which I actually found what I was looking for.

 

Among other things, I came across this old photo of the transporter, which initially caused quite a bit of confusion for me,

 

Source: Space Congress Proceedings 2. - 1980 (17th) A New Era In Technology (W. H. Rock)

 

because one can see that the transporter has 24 twin wheel sets and therefore had not only 24 but a total of 48 wheels.

 

Of course I had to get to the bottom of this and asked my friend James MacLaren about it, who also confirmed it to me, especially since he also wondered about it when he first saw this vehicle.

 

Another open question was whether the transporter only had a driver's cabin on one side, as initially shown in the pictures, or perhaps on both sides, as is also was the case with the Crawler.

 

And he also answered this question right away by saying that the transporter of the time had a cabin both on the front and on the back, although he was actually of the opinion (original sound):  In truth, the thing did not have a front side or a back side. Didn't matter which way it was pointed. Driver gets in and "go". Real simple that way. Wherewith this detail was clarified too. 

 

The confirmation for this I finally got in a contribution by M. E. Donahue: Payload Transportation at KSC, held at the Space Shuttle Technical Conference (1983). 

 

Source: NASA Conference Publication 2342 Part 2 (M. E. Donahue)

 

On it one can also read that the electrical, environmental, fluid and gas, and instrumentation services required by the payload during transportation are supplied by separate Subsystems, which one can see in the drawing above (Figure 3), 

 

- the Electrical Power Subsystem (EPS Modules), 

 

- the Environmental Control System (ECS Module), 

 

- the Instrumentation and Communication Subsystem (I&CS Module) and

 

- the Fluid and Gas Subsystem (F&GS) (F&GS Module).

 

This transporter is a true masterpiece of transport technology. Its elevating flat bed has a height of 1,8 m (6') but can be lowered to 1,6 m (5'-3'') depending on the terrain or raised to 2,1 m (7'±3'').  

 

Its 24 twin wheel sets can be steered independently of one another and enable the transporter to move forwards, backwards and sideways or diagonally, or to rotate around its own axis like a merry-go-round. All each have separate brake and stabilization lifting systems, if you will a Jack of all trades device.

 

Because payload handling will require precise movements, the transporter has a "creep mode" that permits it to move as slowly as 0,64 cm/s (0,25 in/s) or 0,023 km/h (0,014 mph).

 

From this drawing I determined the dimensions of the Payload Canister for my scale (1:160), 

 

Source: NASA Conference Publication 2342 Part 2 (M. E. Donahue)

 

L = 65' = 124 mm (1:160) x B = 18' = 34 mm (1:160) x H = 18'-7'' = 35 mm (1:160),

 

and in the text one can also find the dimensions of the Transporter, so now I know what's in store for me.

 

L = 65' = 124 mm (1:160) x B = 23' = 44 mm (1:160) x H = 6' = 11,5 mm (1:160)

 

And that's enough for me to scratch-building, since I now know what the side view looked like, as well as the 'front/back side', as in this photo from the STS-6 CD-ROM can be seen here. 

 

Source: retrospaceimages.com (STS-6)

 

Now I can think about whether I should start building the Transporter right away or postpone it for the time being ...

 

The wheel sets remind me a lot of the 14 wheel sets of the main landing gears of my Antonov An-225, which is also waiting for me in my cupboard ...

 

 

Source: flugzeug-lexikon.de (ILA_2010)

 

In terms of structure, they should look similar to these one, only that the Transporter has twin wheel sets.

 

Source: wikimedia.org

 

That's just in order to get attuned a bit.

[roma847]

Hello everybody,

 

and here is a small addendum to the Astrovan (1:160), to which of course also Astronauts belong to.

 

 

[roma847]

Hello everybody,

 

and since I now know how big the Payload Canister and its Transporter are, I wanted to get an overview of the proportions right away,  

 

 

and have drawn the side view of the canister into the transporter's photo. And this silhouette I used as a stand-up display for the Astrovan with the astronaut. And this combo doesn't look bad, I think.

 

 

Of course, the KAMAG logos will later be replaced by the appropriate NASA Worm logos, naturally.

[Adm Lord De Univers]

The detail you proceed to go into still amazes me even after all these posts, specifically the first photo above. I don't know why, it's not surprise at this point, but definitely admiration. My only surprise will be if it cannot actually lift off into low earth orbit!

 

David

[Mustermark]

Great to see more progress! The Astrovan looks fantastic. And yet more amazing research 👍

[roma847]

Thanks David and Mark for your nice comments. 

 

The Payload Canister Transporter is a masterpiece of hi-tech transport technology and an extraordinary vehicle, that shouldn't be missing on my diorama, just a little like the Astrovan. 

[roma847]

Hello everybody,

 

now I've got started modeling a prototype of  the Payload Canister.  

 

With the the known main dimensions (LxWxH) I first tried to construct a simple Paper kit (1:160) of the canister on graph paper, for which you need not only the base area (124 mm x 34 mm), but also the exact shape of the front sides and the dimensions of the canister shell. 

 

The prerequisite for this was a suitable photo of the front side of the canister, but if possible without perspective distortion, for which I chose this photo of the STS-104, whereby it only depends on the canister. Although this modified transporter in 2001 looked slightly different than it was used during STS-6, the dimensions of the Payload Canisters remained unchanged throughout the shuttle program. 

 

Source: mediaarchive.ksc.nasa.gov

 

To determine the dimensions of the canister shell, I first reduced a section of this photo to 1:160 in order to be able to determine the length of the border outline. This shrinked the  canister's width from 18' to 34 mm. 

 

 

For doing this I then bent a thin copper wire (Ø 0,25 mm) around the contour of the front side and fixed it,

 

 

 

which resulted in a contour's length of 94 mm.

 

 

And with that I could now draw the paper kit of the canister. 

 

 

 

This can now be used to produce a prototype of the canister,

 

 

whereby the Payload Canister for the Diorama is to be scratched out of Styrene as well as the Transporter. 

 

Let's wait and see how this stunning transport vehicle will look like ... 

 

[roma847]

My friends,

 

we will never forget this day when yesterday 36 years ago the Challenger disaster happened on the newly built launch pad 39B and the STS-51L crew of seven became everlasting legends.

 

 
Back row: Ellison S. Onizuka, S. Christa McAuliffe, Gregory B. Jarvis, Judith A. Resnik
Front row: Michael J. Smith, Francis R. "Dick" Scobee, Ronald E. McNair
Source: wikipedia.org

 

That's why my STS-6 project should be a little tribute to these heroes of American spaceflight history.

 

May they rest in peace. 

[roma847]

Hello everybody,

 

then I want to continue, so as not to get completely out of practice.  

However, I've first turned to the Transporter, which still gave me a few puzzles that I still had to solve.  

 

In the beginning I've used this beautiful image of the transporter as a guide, 

 

Source: mediaarchive.ksc.nasa.gov

 

and I first started the experimental assembly, for which I glued both side fronts onto a Balsa board (2 mm), whereby I was so busy that I made a few mistakes, which I've only gradually recognized.

 

Since the photo shows one of the 2000 transporters delivered by KAMAG, I've first replaced the front KAMAG Logo with the NASA Worm Logo and pasted over the back logo, which later turned out to be a mistake. That had to do with the fact that I was initially guided by James MacLaren's words that the first transporters had driver's cabs on both sides, which is why one had not need to distinguish between front and back side, but what is simply thought too short ...

 

This also resulted in the error in my reasoning that I mirrored the other side, which was not necessary respectively wrong.

 

 

So I created a copy of the first side and thus had two opposite sides and thus a driver's cabin on both front sides. So far so good.

 

 

With that I could now continue the construction, for which I've fixed the two side parts on a steel sheet with magnets over the floor plan of the transporter (124 mm x 44 mm) in order to then be able to glue the front and back side between them.

 

 

To do this, I looked again at the few photos of the transporter from the STS-6 and from the STS-9, which followed six months later, and have compared them with James MacLaren's photos, which were from the same period.

 

And in doing so, I noticed some serious differences regarding the front and rear of the transporters of that time, which I had not known or overlooked before, but which are decisive for their construction. And they are clearly related to the direction of travel of the transporter when transporting the Payload Canister to the launch pad, which ultimately should turn out to be the solution to the riddle.

 

But since I've made good resolutions and don't want to work a night shift again, I'll stop at this point and continue tomorrow.

[roma847]

Hello everybody,

 

as should have already become clear in my last post, I struggled with some inconsistencies and ambiguities for a while, the clarification of which was actually a rather tough nut to crack, which, on the one hand, kept me busy longer than expected and was quite stressful, but on the other hand, was essential in order to can scratch the transporter used that time possibly close true to the original at STS-6.

 

As already indicated, I've tried to get things straight concerning the driving direction of the Transporter when transporting the Payload canister to the Launch pad, during the canister was always standing upright (Vertical Transportation Mode).

 

Source: Space Shuttle News Reference (NTR Server, 1981)

 

In this upright position, the transporter leaves the preparation building (Vertical Processing Facility), as can be seen in this image of the STS-6. And now it gets interesting.

 

Source: retrospaceimages.com (STS-6)

 

In this position with the flat side of the canister forward, however, the transporter does not drive to the launch pad but in the opposite direction, wherefore it's controlled from the driver's cab on the rear side, what is a small but subtle difference that one have to take into account, what can be seen in the following image.

 

Here, in the mid-1980s, the transporter was almost at its destination on the way to the pad and is already on the slanted access road, with the hillslope being compensated by the lifting technology of the chassis, as one can clearly see.  

 

Because of the driving direction, this is for me as from now the front side of the transporter.

 

Source: 16streets.com/MacLaren

 

Arrived on the pad, the transporter finally maneuvers in a left turn so far under the RSS until it comes up with the Payload Canister directly under the Payload Bay of the RSS and there to standstill. 

 

Consequently in this image by James MacLaren one has a look at the back side of the transporter with the rear driver's cab and at the F&GS Module and I&CS Module, located on this side, whose tasks have already been briefly described in Posted January 18

 

Source: 16streets.com/MacLaren

 

In this position directly under the Payload Bay of the RSS, the transporter turns into a special Hoisting Mode, in which it gets on its knees, which means that the front side is tilted down and the back side tilted up, so that the canister can then be hoisted up by the RSS crane.

 

Source: capcomespace.net

 

On this photo of the STS-6 one can see the canister already hoisted in front of the RSS Payload Bay and the discharged transporter below, looking onto the rear of the Transporter with its back side. 

 

Source: retrospaceimages.com (STS-6)

 

In the zoom one nicely can see the arrangement of the I&CS and F&GS modules. 

 

Source: retrospaceimages.com (STS-6)

 

And now all I needed was a similarly good shot of the front side of the transporter, which one can see in this cropped photo from the STS-6. A typical feature on the front side are the red hoses, via which the air conditioning of the Environmental Control System (ECS module) is connected to the canister, whereby constantly clean room conditions were ensured inside. 

 

Source: retrospaceimages.com (STS-6)

 

Here is another image of the front side of the transporter in Horizontal Transportation Mode of the canister at STS-9 in late 1983 showing the side connections of the hoses at the canister. 

 

Source: forum.nasaspaceflight.com (Ares67)

 

With this the structure of the Payload Canister Transporter of that time as the basis for scratching has now been fundamentally clarified, from which it is clearly evident that the KAMAG Transporter delivered in 2000 differed from the early transporters by having a clearly different structure especially at its back side. 

 

Source: mediaarchive.ksc.nasa.gov

 

Besides the fact that there was only one driver's cab at the front side, one can see this large cavity at the back side that I had noticed all along. In addition, the rear end is stretched far too long due to the perspective distortion of the photo, which has surprised me and initially irritated me.

 

Consequently I have to revise the design of my side walls again and adapt some details to the outfit of the STS-6 transporter.

[roma847]

Hello everybody,

 

at least this inconsistency I have now been able to clarify.

 

As one can see in this photo of the transporters 2000 delivered to NASA for replacing their 20-year-old predecessors, the space next to the driver's cab for the Environmental Control System (ECS) was still empty, which is why I assume that the transporters were subsequently equipped at the KSC with some of the previously described subsystems for monitoring the environment inside the canister: the Electrical Power System (EPS), the Environmental Control System (ECS), the Instrumentation and Communications System (I&CS) and the Fluids and Gas System (F&GS). 

 

Source: mediaarchive.ksc.nasa.gov

 

This image before STS-125 shows the ECS Module at the front side of the transporter as it enters the clean room environment of the Payload Hazardous Servicing Facility to load Hubble hardware/equipment to service the Hubble Space Telescope during this mission. 

 

Source: NASA (Kim Shiflett)

 

Next, I tried to adapt the previous side walls of the transporter to the STS-6 outfit of that time. 

 

 

To do this, I have carried out extensive analyzes of my reference photos from that time, through which I have recognized some typical differences in detail, especially on the front and back side.

 

 

These two photos by James MacLaren were very helpful, 

 

Source: 16streets.com/MacLaren

 

 

where one can see, among other things, that the driver's cabin had a different shape at that time and the driver's door had a larger rectangular window. There were also added some instruments on the side panels as well as the modules on the back that I tried to replicate. 

 

 

As a result, the NASA Worm logo of that time also moved to the right place further back. I've then scaled these details down to my scale (1:160) and photo-mounted them on the previous side walls and added the front and back sides from that time, which I then liked much better. 

 

 

 

These modified side walls I've then first glued again onto a Balsa board (2 mm), but then quickly realized that this two-dimensional representation of the walls with textures similar to David Maier's Paper Kits looks a bit too unrealistic, since some of the details have to be behind the 2 mm thick side walls, such as in particular the double twin wheel sets, about the modeling of which I was uncertain for a long time ...

After careful consideration, I then discarded my previous Scratch concept and thought about a more realistic construction of the transporter, whereto I carefully separated the driver's cabins and modules at the end of the side walls.

 

 

Some more information on that will come next time.  

[roma847]

Hello everybody,

 

let's continue, and with that to the Twin wheel sets, the structure of which, starting from this old photo, I only gradually got to understand.

 

Source: Space Congress Proceedings 2. - 1980 (17th) A New Era In Technology (W. H. Rock)

 

A bit of luck is part of it!

 

While browsing the KAMAG websites, I came across these principle sketches in an image brochure some time ago, wherewith I have a good chance for scratching the chassis of the transporter.

 

Source: tii-group.com

 

 

I first divided a wheel row in the middle, mirrored one of the halves, 

 

       

 

and then scaled to my scale (1:160) and printed out in shades of grey, which therefore match the side walls very well.

 

 

Using this template, I can now produce the 48 wheels (Ø 6 mm, 2 mm thick) of the early transporter, which are then glued together with spacers, and hint at the 12 pendulum axles with two twin wheel sets each. The only things missing then are the hydraulic push rods, which I'll do without because you're unlikely to see them under the finished transporter.

 

 

In reality, this hydraulically supported Pendulum axle looks like this, whose construction principle was created by SCHEUERLE in 1956, which meanwhile, like KAMAG, belongs to the TII Group, which facilitated the arrangement of several axes in a row, wherewith the production of multiple-axle heavy-duty vehicles began. The hydraulic pendulum axle is still the main principle of modern heavy-duty transport worldwide.

 

Source: tii-group.com

 

 

In my modified Scratch concept, I planned to design the driver's cabs and the modules on the front and back as individual components, for which I rescaled all detailed views again based on the reduced width (40 mm) between the side walls. 

 

These are the designs for the modules on the front (top) and back covered with the corresponding detailed views, 

 

 

 

and these are the prepared parts for the modules, which can be glued under the ceiling between the side walls of the transporter after building. 

 

 

 

And I will now still design a similar part for the two Driver's cabins.

[Adm Lord De Univers]

I think most of us, maybe just me, use extraneous vehicles as part of the diorama and omit some of the detail from them - actually I'd use them to hide flaws somewhere too. But you're creating these as highly detailed models in their own right. Truly impressive.

 

I think I've learnt more about shuttle operations from this thread (and our v helpful conversation) than I ever did from all other sources combined. Can't wait to see all these parts together - though I am interested in how big this build is going to be.

 

David

[roma847]

Thanks David for your appreciative words,  which show me that it is obviously interesting and worthwhile to find out information about technical details in addition to pure model building, which was my guiding idea of this project from the start. 

 

As I have posted in September 2020 my Diorama (1/160) could look something like this Mini-Diorama (1/700) by Tomytec (sold out), whose base plate is only 35 cm x 29 cm "big". 

 

Source: Andromeda24.de

 

My planned Diorama should be a little bit bigger with 160 cm x 90 cm. 

 

 

And of course that includes a few typical vehicles ... 

[Adm Lord De Univers]

Oh yes. On all of the above.

 

David

[John_W]

This popped up in my Facebook feed.

 

 

[roma847]

A very impressive Launch Pad model, appears to be 1/72, a great scale to do nice details with. 

[Adm Lord De Univers]

Ye gods, I could barely countenance what my partner would say if I turned up with a 160x90cm model!

 

David

[roma847]

Hello everybody,

 

here is a small video addendum for all interested guys who want to see such a Heavy-duty Transport in action, which would be unthinkable without these ingenious Hydraulically supported Pendulum axles.

 

 

Such heavy-duty transports are really incredible, especially since you not only have to use powerful Trucks but also Self-propelled platform vehicles in combination with Transport swivel bolsters, so that you can get around tight corners with those overly long colossuses.  

 

Source: SCHEUERLE

 

But for the Payload Canister the "small" Transporter is enough, that the NASA at KAMAG had commissioned in 1979.  

[roma847]

Hello everybody,

 

and this is now the layout for the Driver's cabins. 

Then all edges and adhesive folds of the parts were carefully pre-scored,  

 

 

folded, 

 

 

and finally glued the parts together, like here the I&CS/F&GS Modules for the back side (left), as well as the ECS Module for the front side, 

 

 

and here with the associated Driver's cabins.

 

 

And so the parts are then arranged under the ceiling panel and between the side walls of the transporter. 

 

 

 

The next thing to do is to continue with the Pendulum axles and Twin wheel sets.  
 

[roma847]

Have a look at this monster transport of an Aluminum melting plant module on SCHEUERLE "SPMTs"!

 

Source: SCHEUERLE

 

The SCHEUERLE SPMT is a modular, self-propelled transporter that can be combined to form any size transport group and has completely changed the transport industry since its market launch in 1983.

[roma847]

Hello friends,

 

and so now to the Pendulum axles of this 48-wheeled monster transporter, which inspire me with quite a bit of respect.

 

Source: Space Congress Proceedings 2. - 1980 (17th) A New Era In Technology (W. H. Rock)

 

On this image of a similar transporter one can see the arrangement of the axles with the twin wheel sets more clearly. 

 

Source: tii-group.com

 

In principle, the structure is meanwhile clear to me, but now it's about the practical implementation by scratching, which I've been fiddling around for a long time ...

 

Finally I came up with the following simplified solution.

First of all, I need the 48 wheels, which I then have to conjure up somehow on the Pendulum axles.

 

For this I have the cut out wheel discs in a 1st Variant glued to balsa wood (2 mm) and laboriously cut off all around with a razor blade, 

 

 

which is not exactly a cakewalk, which is why I have to think of another technique for this.

 

 

For the continuous holding of the twin wheel sets, I also transferred the wheel set contour under the side wall onto Balsa wood (2 mm), 

 

 

 

 

and roughly sawed them out just as laboriously with a mini saw.

 

 

 

After that I have as a 2nd Wheel variant punched out small round blanks (Ø 7 mm) from cardboard (1 mm) with a hole punch and glued them together, which is easier to do than the Balsa carving.  

 

For a more accurate prototype, I also punched round blanks out of Styrene (2 mm), which was quite an ordeal and therefore cannot be used for series production.  

 

 

These twin wheel sets are provisionally placed on the holder, which looks too unrealistic to me, since this holder should already have a certain ground clearance.

 

 

So I shortened the lower part of the holder a bit so that the wheel sets protrude a little bit, 

 

 

which I like already better.

 

 

And so I would try it now with twin wheel sets on both sides of the holder to see how it looks then.