Honey, I shrunk the T28 Super Heavy Tank

[Possibly Apocryphal]

 

Building an accurate T28 Heavy Tank / T95 105mm GMC

Dragon's T28 Super Heavy Tank ranks as perhaps the most disappointing AFV kit from a major manufacturer in recent years.  In order to make use of existing Sherman HVSS suspension components Dragon seriously compromised the kit's accuracy.  It's a fair bit too long and much too wide.  The length discrepancy depends on exactly what you're measuring, but for example, the side skirts should measure 207mm from the front tip to the vertical straight edge at the rear; the kit part measures 219.5mm.  The overall width of the real vehicle (with the outer track in place) is 14 ft 5 in, which in 1:35 is 125.5mm, but the Dragon kit is 139.5 mm - an error of about 11%.  I've wanted to build a T28 for more years than I can remember, but I strive for accuracy in my models.  So, what to do?  Well, there's the resin kit from Accurate Armour, which is a massive expense, especially when added to the price of the Dragon it, which I had already bought before I knew about the inaccuracies.  Or you could wait for Meng or Trumpeter or Takom or Hobby Boss to release a better one, but who knows if or when that might happen.  Or you could just accept that despite the inaccuracy, it still looks like a T28/T95 and build it as is.  Nope, not me.  I tried to figure out a way to try and correct, as far as possible, the Dragon kit, but in the end I concluded that it wasn't really feasible.  So it's going to be a semi-scratchbuild project, using as much of the Dragon kit as I can, but only what I can use while maintaining the goal of building an accurate model.  This is going to take a while, and I get distracted easily, so don't be surprised when there are long gaps between updates!

Edited August 17, 2017 by Possibly Apocryphal

[Possibly Apocryphal]

Before I could start, I needed scale drawings.  The ones I used are from the R.P Hunnicut book on U.S. Heavy Tanks, scanned, scaled to 1:35, laser printed and then dimension checked.  I actually found a nicer set on the internet, but unfortunately, they were a little distorted so I couldn't use them.  Not to worry, the Hunnicut plans (which I think were drawn by Phil Dyer) are quite sound.  I also used the cross-section view from the Tech Manual, which was reproduced in the Hunnicut book. 

Since it was the decision to use off the shelf HVSS suspension comonents that drove the error in the kit's width, I decided the first job was to determine whether anything here was going to be useable.  The Dragon tracks are 2mm too wide (because they are the same width as Sherman HVSS tracks, whereas the T28's were narrower).  Multiplied by four, that accounts for 8mm of the width error by itself.  By thinning the wheels a little, and reducing the length of the axle between them, I managed to shave a little more than 2mm from the width of the assembled bogies, which meant they would fit inside the correct track width and I wouldn't have to cast resin replacements as I was expecting.  That calls for cake!!  In fact, it now looks as though the only parts I will have to cast are the tracks temselves.

 

 

You can see from this Tech Manual photo that the track block is only just a wee bit wider than the width of the wheels, so the margin I've got here is entirely adequate.

 

So, 32 of those then.

[Possibly Apocryphal]

But there's still more work needed on the bogies.  I needed to reduce the distance between the mounting surface and the road wheels by about 2.5 to 3mm.  This involved sanding down the mounting plate and extension arm where they join together, which gained me about 1.5mm, and then reducing the pivot of the road wheel mounting arm by another 1.25mm.

 

Unfortinately, this reduced the amount of room for the HVSS springs, so I sanded down the spring sleeve on the mounting side and also Dremeled out the mounting point to create the necessary clearance.  I left this as a fairly rough job, since it's all going to be completely hidden anyway.

 

These three photos show the unmodified kit bogies (on the left), and the reduced with bogies on the right.

 

And here is the reduction on the pivot arm.

 

So, 16 complete slim-line HVSS bogies.

 

Edited August 17, 2017 by Possibly Apocryphal
typo

[Possibly Apocryphal]

"But isn't this this a scratchbuilding project" I hear you say.  So it is, time to cut some plastic card.  The first bit is the lower hull, build mostly from 60 thou card.  I like using thick card, because it makes for a nice robust structure that won't warp over time.  It does make the joints more difficult to do neatly, especially were they're not at right angles, but I think it's worth the effort.  The lower hull sides are 60 thou too, but in this case a laminate of 40 and 20.  I cut slots in the 20 piece for mounting the suspension before gluing it to the main 40 thou part.  You can also see that I use plenty of internal bracing pieces.  Its important to ensure that everything is square and true.  If it's out of whack at this stage it's impossible to correct later.

 

The scratchbuilt lower hull fits comfortably inside the Dragon kit part!

[Possibly Apocryphal]

On to the superstructure.  This is all 60 thou as well.  My method of making large cast structures is to build the underlying shape from plastic card, and then use epoxy putty to make the curvy bits.  This approach is especially applicable to the T28, because although the upper hull is a massive casting, it is mostly smooth flat surfaces.  First I made the vertical plates at the rear, and attached them with the aid of square braces.  Then I cut out the roof and mounted it on two supports to set the correct height.

 

The next step was to make the sloping upper side pieces, and the angled parts at the front.  This involved a certain amount of trial and error and gap-filling.  In some areas, its still a bit rough and gappy, but that will be sorted out when I do the curvy bits.  At this point I also added the rear plate from 40 thou card.

[Possibly Apocryphal]

Next, I tackled the unusual recessed engine deck.  I was expecting this to be quite tricky, but in the end it was pretty straightforward when it's done in a logical sequence.  I confirmed from this photo that the walls of the recess are smooth, with no overhanging lip, and at right angles.

 

First I made the triangular fillets at the rear of the hull from 40 thou card, and then the floor of the recessed area from 60 thou.  It goes the full distance from the rear hull plate to the bulkhead at the rear of the fighting compartment.  Because it's parallel to the slope of the rear of the hull rather than horizontal, the length would be slightly greater than the dimension of the plan view.  The width wasn't critical, it just needed to be wide enough, with any excess being hidden by the side walls.  I glued strips of card horizontally to the bulkhead and rear plate for the floor to rest on.  By carefully measuring the depth I set these at, I would ensure the correct depth for the recess as a whole.  I then made the side walls and the raised ridge around the edge from 60 thou card.  Finally, I added the vertical dividing plate half way along, also from 60 thou card.

 

And that's where it stands right now.  The next step is to break out the epoxy putty and do the curved bits of the upper hull casting.

Edited August 17, 2017 by Possibly Apocryphal

[SimonT]

Fantastic skills, you're nuts, but great skills

[Possibly Apocryphal]

36 minutes ago, SimonT said:

Fantastic skills, you're nuts, but great skills

Well, we're all a bit nuts aren't we?  Admittedly, some of us more so than others, but I wouldn't do it this way if I didn't enjoy it!  Anyone who hasn't ever tried scratchbuilding needs to understand there's a level of satisfaction in it that you just can't get from assembling kits.

[spitfire1677]

Superb modelling skills on show here, very impressive

[Kingsman]

The one surviving T28 might be a couple of inches narrower now after the Patton Museum managed to throw it off the back of a HET on the way to the paint shop!!  Downhill, bend, too fast, no chain gonna hold it.  Got away with just bogie damage, fortunately, or they might have been faced with their own (1:1) scratchbuild...........

[Possibly Apocryphal]

On 8/18/2017 at 9:03 AM, Das Abteilung said:

The one surviving T28 might be a couple of inches narrower now after the Patton Museum managed to throw it off the back of a HET on the way to the paint shop!!  Downhill, bend, too fast, no chain gonna hold it.  Got away with just bogie damage, fortunately, or they might have been faced with their own (1:1) scratchbuild...........

I hadn't herd about that!  But with its armour thickness, I suspect they could have dropped it out of a C-141 from 30,000 feet and not done much damage...

[Possibly Apocryphal]

The nest stage is to do the not straight bits of the cast superstructure.  At this point, scratchbilding becomes more of an art than a science.  Photos are a lot more important than plans at this stage.  Basically, the process is to build up an approximation of the desired shape with epoxy putty (the one I use is Magic Sculpt), and then smooth it and refine the shape with coarse wet & dry paper, or careful use of the Dremel.  This is the tool kit for the job:

 

Usually my first application of putty only results in an approximation of the correct shape.  It usually takes two or three attempts to get the shape right, so it's a bit of a slow process when you factor in the curing time for the putty.  After about four hours, it sets to the point that you can't make much of an impression in it with a finger nail, but its still difficult to sand at that point, so I like to give it about twelve hours to harden sufficiently.  This is the right hand side of the hull after the first application:
 

 

And the shape refined after the second attempt:

 

 

And the left side:

 

So that's just about done now, I just need to do more intricate indentations around the front top edge.

[Kingsman]

This really is most excellent work.  You must really love the T28.  It is a shame that 2 manufacturers have got it so wrong with a surviving reference vehicle, although I understand the AA faults are more about parts quality and fit.  I'm working on the companion Tortoise, but as a what-if MkIICS 4.5" assault gun: infinitely less challenging.

 

Regarding the accident .........

Before.  Outer tracks and skirts removed.  

 

After.

 

The road is just off to the left, bending to the left and this is on the outside of the bend. The road comes down a hill at about 10 o'clock and crosses the railroad before the bend. The driver claimed brake failure, but the real cause was brain failure.  The poor T28 flew bodily several yards off the HET, it didn't just fall off!  So just how fast was he travelling?

 

This is the UK entry in the Chucking A Tank Off The Back Of A Transporter competition.  CRAARV fell off a HET taking a roundabout near Poole too fast.  Just off to the right is a drop down onto the A35.....

 

Sorry for stealing the thread with tank transporter accidents ...............   Keep up the excellent work.  Looking forward to the outcome.

[depressed lemur]

You could save yourself a lot of track work by doing a post crash diorama 

[Steve_farrier]

Wow nice build so far. Interestingly there has just been a release of the this model in 1:16 full RC 

[Bullbasket]

Every so often, a build comes along that is absolutely jaw dropping and this rates along with them. I've scratch built welded Sherman hulls before now, but never attempted anything with a cast hull. So far, this is a master class. Watching 'till the end.

 

John. 

[Possibly Apocryphal]

On 8/19/2017 at 7:53 PM, Das Abteilung said:

This really is most excellent work.  You must really love the T28.  It is a shame that 2 manufacturers have got it so wrong with a surviving reference vehicle, although I understand the AA faults are more about parts quality and fit.  I'm working on the companion Tortoise, but as a what-if MkIICS 4.5" assault gun: infinitely less challenging.

 

The poor T28 flew bodily several yards off the HET, it didn't just fall off!  So just how fast was he travelling?

 

Sorry for stealing the thread with tank transporter accidents ...............   Keep up the excellent work.  Looking forward to the outcome.

As I mentioned in the intro, I've wanted to build a T28 for a LONG time!  Yeah, I do really love it!  Not suprised by what you say about the AA kit, I've not been impressed with their quality in the past.  One of the reasons I ignore resin kits when I'm considering scratchbuild subjects.

 

How fast was he traveling?  Probably more than the 8mph the T28 could manage under its own power!

 

Tank transporter accidents are a valid reason to hijack any thread!

[Possibly Apocryphal]

On 8/20/2017 at 5:35 PM, Bullbasket said:

Every so often, a build comes along that is absolutely jaw dropping and this rates along with them. I've scratch built welded Sherman hulls before now, but never attempted anything with a cast hull. So far, this is a master class. Watching 'till the end.

 

John. 

You're too kind, sir!

[Possibly Apocryphal]

A few additional Dremel bits needed for the last casting contours:

 

To achieve this:

 

Note the depression in front of the position of the gunner's periscope.  Dragon completely missed, so their gunner can't see what the gun's pointing at when it's depressed below horizontal.  In fact, most of their details about the finer curvature are vague and inaccurate.  You can see that, even with the thick card the hull is built from, I've gone through it.  No problem, though, it just needs some more putty to fill the holes.

 

This is the former for the big gimball mount for the gun.  It's not a complete hemisphere, but deceptively close.

 

Without the former, all you're working with is a big blob of epoxy putty. 

 

Sanded smooth and in place we get this:

[Possibly Apocryphal]

Then I moved on to the final drive housings at the rear of the hull.  Like the gimbal, I used plastic card formers and filled the gap with epoxy putty, then sanded it to shape.

[Possibly Apocryphal]

And with that, I reckon the hull is structurally complete.  That's always a big milestone in a scratchbbuild project.

 

[Possibly Apocryphal]

So now we get to the clever bit.  Like just about everything else, the Dragon mantlet is too big.  But its too big by exactly the right amount.  By that I mean, a mantlet of the correct size will fit just about exactly inside the kit mantlet, and that means I can use the kit part as a mold to make a smaller one from epoxy putty!  Here it is stuffed with putty.

 

Once the putty was hard enough, I separated it from the kit plastic by using the highly sophisticated technique of dropping it repeatedly on the floor, and then prizing it out with a finger nail.

 

You can see I didn't get the putty all the way into the bottom of the mold, but that's easily fixed.  Also, it needs some trimming...

 

...and some gouging out at the back...

 

...but the size is just about perfect.

 

And of course, the turned 105mm barrel is one kit part I certainly will be using.

 

So, the next step will be building the side skirts and outer track housings.

 

Edited August 23, 2017 by Possibly Apocryphal
typo

[Possibly Apocryphal]

Because of the detail on the side skirts, I looked at the possibility of correcting rather than replacing the Dragon parts.  I figured out that if I removed some sections, I could get it down to the correct length without damaging the detail.  Basically the plan was this:

 

Which resulted in this:

 

But after I joined a few sections back together, I decided that it wasn't going to be worth the effort (and the detail isn't that great anyway).  In order to get all the holes to be a consistent depth, I decided that I would drill them is a sheet of 20 thou card, and then laminate that to the thicker plates. 

 

In fact, the skirts are really thick.  There's a step in the skirt ahead of the superstructure where is thins down, but even here it needs to be 2mm thick.  Aft of the step it's 3mm.  40 thousandths of an inch = 1mm, so the total I needed is 80 thou at the front and 120 thou at the rear.  I got this by making the skirts from five pieces of card:

 

 

First, I glued the rear sheet of 20 thou to the 40 thou piece, and when that was set beveled the edge were the step is.  Then I glued this and the forward piece of 20 thou to the full length 60 thou piece.  Here are the completed skirts

[Possibly Apocryphal]

I made the remainder of the outer track units from 40 thou card.  That's a bit thinner than I'd used for the main hull structure, but I needed these joints to be really precise, and that's easier to achieve with thinner card.  The plates under the track guards, and the 1mm brass rod pins are to ensure precise alignment with the main hull unit, which I could see would be important both at this stage and later.  The first piece was the vertical piece that goes against the hull, then the large sloping piece, and finally the smaller angled piece at the front.  The measurements for all these pieces have to be taken from the model rather than the plans at this point.  Unfortunately, I was so involved in the process I for got to take step by step photos, but here is the end result:

[Possibly Apocryphal]

So at this point the structural work is complete!  I have to say, when I joined up the first outer unit with the main hull and it all fit together perfectly with a continuous straight slope from the hull roof to the top of the side skirt, well...you couldn't have knocked the smile off my face with a sledgehammer!  This is what a 1:35 scale T28 hull looks like, Dragon!  It's quite wide enough to be really impressive without being bloated by another 14mm.

 

 

So that's it for now.  You remember all those suspension bogies I modified right at the beginning?  They get attached to this lot next.