This is only my second Ace kit, the first being an as yet unfinished Wespe self-propelled gun. On the box of this RSO/01 with 2cm FLAK38 it says it's 'a plastic kit made under short run technology'.
I bought this kit 'cause it's one of the only ways to get hold of an RSO kit at present, in1/72. Rather annoyingly, for me at least, the RSO 1 kit, also by Ace, is out of production (damn that short run technology!), and very hard to come by unassembled. So, my choice was limited to variants. I chose this one because it has the right type of cab, and the most basic and standard body-type. Other variants, mostly from Ace, have different cabs, flotation devices, and so on. I think I'll probably buy the Dragon 1/35 RSO model at some point. But for now this Ace kit is to be my intro to modelling this interesting vehicle.
The RSO was, as the Ace box helpfully informs us, designed especially for the conditions of the Ostfront, using designs based on Russian tractors that were equipped with tracks. Many variants on the basic design were made, and this kit depicts a version equipped with the ... [?] flak antiaircraft gun. I have toyed with the idea of converting this kit to the standard RSO 1 type, with a P&O,e framework and canvas covering for the rear-stowage area. Whichever way I go though, I'll assemble all the parts of the kit as supplied.
I started the build on January 3rd, 2015, but having very limited time I was only able to build the running-gear and chassis. I also managed to put together one of the four sections of photo-etched tracks. I'll return to the subject of these tracks in due course. My previous Ace kit was a Wespe self-propelled gun, which was quite a nice kit, albeit it suffered from more flash than many other kits I'm building, and there were several parts that didn't fit very snugly.
Chassis & wheels, etc:
On this occasion lack of clarity in the instructions, poor fit of numerous parts, and my own stupidity, combined to almost render the first few stages completely disastrous! The four pieces that make up the body of the chassis were fine, fitting nicely together. But one part (I forget exactly which) which I missed out at first, and then hastily stuck in - which required prising the chassis apart - rather upset the fine fit thus far enjoyed.
After this it was the turn of the suspension and the wheels. I find that, when assembling this part of many military vehicle type kits, there's often a rather large scope for multiplication of errors. In this instance the first part of the suspension fit very nicely to the chassis body. But after that everything was rather haphazard. Many parts needed quite a bit of fiddling with before they would fit properly. Some of which is referred to in the instructions, such as filing down parts of the drive-sprockets and idler wheels. 
It was also at this stage that the instructions and the shape of some of the parts supplied almost conspire to put a complete kibosh on this build. The eight road wheels all needed their 'female' holes widening and deepening, to make them ready to mount on the suspension. But a far bigger problem arose when I slightly misunderstood the instructions, referred to above, which ask one to sand or file back some of the drive wheel components. Fortunately some spare sprue allowed me to bulk out an area I'd mistakenly sanded down, and all the wheels were eventually mounted, albeit not as nicely aligned as I'd hoped.
The photo-etched tracks:
Amongst the several reasons I was drawn to this kit, and beside the most fundamental - it being an RSO - one was that I wanted to have a go at using photo-etched tracks. The whole photo-etched malarkey is a new area for me, something the Airfix and Tamiya kits of my youths certainly never had. In this kit each track comes as two parts, and each of the total four parts (plus there are three individual spare links) comes as a flat section of two parallel tracks, which need bending over on themselves, to give a double thickness track with detail on both sides.
In addition to this, already more labour intensive than rubber-band tracks, if not yet quite as demanding as link'n'length, every single individual tooth - 82 per track length, giving a total 328 - needs bending through 90° into its proper position! So ultimately they're by far the most demanding track I've yet modelled, and this is before even attempting to fit them!
Actually this construction stage is quite enjoyable. Or at least I found it to be so! But right form the moment of bending the two layers of the track back upon themselves I was worrying about fitting them to the model itself. The inner and outer layers are the same length when flat, yet the outer layer will of necessity have to stretch more/further when attempting to fit the tracks around the wheels. What will result? Well, as I'd anticipated... trouble!
First of all bending the metal is tricky. Much trickier than any rubber-band or styrene tracks I've encountered. The metal, especially as two-layers super-glued together, whilst flexible, is hardly what I'd call supple. There are also additional issues arising from the imperfect alignment of the wheels themselves. And even with teeth cut off the drive-wheels, as directed in the instructions, issues of fit, alignment, and the photo-etched track teeth, all conspired to make this stage extremely fiddly, time-consuming and, sad to say, not exactly a heap of fun.
Fixing the tracks in place also required more superglue. After 15 minutes of holding the track to the wheels manually failed to result in a lasting bond, I resorted to a jerry-rigged arrangement (no pun intended) with a pair of elastic-band bound pliers holding the parts in place.
This looked to be doing the job, but actually ended disastrously,because, when I tried to remove the pliers I accidentally squeezed them together. I knew full well I ought not do so, and intended instead to simply release the rubber bands. But something sub-conscious took over, and in order to give the rubber bands some slack, I gently but firmly squeezed the plier-handles, crunching one of the plastic road wheels horribly, and bending the metal track.
Oh dear! Oh dear oh dear.!! Oh dear oh dear oh dear!!! And language a lot worse...
But, since I had no desire to bin the kit and abandon the project, I decided to act quickly and see if I could save the situation. I wish I'd taken before and after pictures. It really looked irredeemable. But, thanks be to who or whatever (myself, I guess!?), perseverance and ingenuity paid off. And I feel that, whilst looking perhaps a little ugly under close scrutiny, most people casually glancing at the result wouldn't guess at what had actually occurred.
Box on't back:
Constructing the box on the rear of the vehicle was one of the easier stages in the making of this kit. Altho' even here some scratch-build skills came in handy, as the inset below shows: to mount the jack properly I felt I needed to add a little disc of sprue behind it.
The Flak. 38 was a fiddly thing to construct. But it does look nice once assembled. The smaller of the two shield type elements had a hole that required the barrel to be cut and then re-glued, in order for it to be mounted in its proper place without recourse to any widening of said hole. Not the best designed element of the kit!
Almost all of the 'male / female' elements o this kit needed working on, as did, for example, these mounting blocks, pictured below. Once mounted on the blocks, I set the Flak 38 in place on the rear of the truck-bed. I've decided to have my gun face rearwards though, rather than over the cab, as it is on the box.
The cabin was another part of the construction which was troubled by ill-fitting parts, as some of the following pictures show. After painting failed to hide these yawning openings, I had to use white Superfine Milliput to fill in the larger gaps.
The kit comes with templates on the instruction sheet for the windows, but no plastic is supplied for the windows themselves. Initially this galled me a bit, but I quickly changed my tune. And once I found an appropriate bit of clear plastic, the DIY spirit kicked in; I ended up loving this part of the build!
The whole model got a black undercoat, and then a spray with the Tamiya 'dark yellow' acrylic aerosol. The Tamiya colour has a decidedly green cast (although the extent of this appears to vary, as a comparison with the pics immediately above and below makes clear), which I'm not altogether sure I like. Also, it doesn't lend itself so well to the hairspray paint chipping effect wither, as it dries with a harder more shell like finish than other paints I've used.
 Rather oddly the box artwork has toothless rear idlers, whereas the corresponding parts of the kit itself are toothed!
 If you look closely at these tracks, it can be seen that the super-glue I used to join the upper and lower layers of each track also, rather annoyingly, gets into all the little gaps where the teeth of the drive wheels are supposed to poke through. I did try poking the holes back into being, with pins and scalpel blades, etc., but the end result was that the segment of track I was working on came apart and had to be reglued. So I gave up on that!