M31 Bridgelayer conversion

[Beekster]

OK, I admit it...I really shouldn't have started this one in earnest.  True, the Takom M31 lower hull and suspension has been done for a while, altered to get that raked-forward hot rod (or grossly overloaded) look that is necessary for this thing.  But when I got the Resicast conversion in my hands (see the Recent Acquisitions thread)  I couldn't help myself.  All I wanted to do was see how the main elements were going to fit...

Sure, like that's even possible without substantially building the model.  So this is where it stands:






You will notice that there are only a few pieces of grey/tan Resicast resin here.  I didn't use the side doors with their very prominent weld seams; I can still remove the kit doors if upcoming reference (David Doyle's huge Lee book due in a few months) indicates otherwise.  Or I'll add my own seams.  I didn't use the main bridge mount, but only because the Belgian resin is a bit bendy and believe it or not laminated styrene is a bit stiffer.  So I largely copied it.  As you see it, everything is pinned together and several glue joints are drying so it now gets left alone for a while.  I have 3D printed sections of M2 Treadway bridge for this, seen here in primer:


That mount in the background is for an M32, and I originally though I would modify it; that was before the Resicast item was available.  The scratchbuilt cross supports under the bridge will remain, but be altered to adjust the spacing between the bridge sections to fit my custom mounting frame.

No, I haven't forgotten about the Ram...but the headlights and mounts are giving me headaches, so work proceeds very slowly on that one.

The Takom Lee/Grant hull actually fits together quite well.  The seams require little cleanup afterwards, and the engineering is clever:  The joins aren't actually where the real plates joined, so that you don't obliterate rivet heads when trying to finesse a seam.  There are some little niggles I've discovered, however.  The tubular braces which support the crane boom lack the holes & pins which held the thing together when the boom supports were extended.  After all this is dry, I will have to remove all the locating pins, remove the support, remove the turret, and figure out how to drill the required holes in the boom supports.  The brackets on the differential housings fit fine, but their shape needs to be altered a bit if you want the boom supports to be mounted there, as I have done.  There is no interior, not that it really needs one, but I've cobbled together a crude winch drum so that when I rig this I can adjust the string tension before locking it down by gluing the drum in place.

This image has been published in several places, and shows what this thing will eventually look like.  It's from the Roer River crossing in November 1944, operated by 17th Armored Engineer Battalion of 2nd Armored division.  The rear porch is included in the Resicast set.  The mud caking everything I will have to make myself.

[JCON]

I like it!!!

[BUCKY]

Nifty project! I'm in for this one!

[dogfish7 (R.I.P.)]

Old enough to know better, but ........ I'll definitely grab a front row seat to any of your builds Beekster.

[Beekster]

Mar 13, 2020 10:10:58 GMT -6 dogfish7 (R.I.P.) said:

Old enough to know better, but ........ I'll definitely grab a front row seat to any of your builds Beekster.

Are you implying that I'm old enough to know better? Pffft!!  In the immortal words of Jimmy Buffett, "I'm growing older, but not up", with all the indiscipline that implies.

I mentioned some niggles with the Takom kit.  Here's more:  The sprocket rings that sit atop the crane boom are wonderfully rendered, and the sprue attachments are positioned so that there's no risk of marring the shape of the teeth during cleanup.  Nice!  But here's the thing:  They don't just sit there by gravity.  There are lugs on the crane boom so that long bolts can be used to firmly keep the rings where they belong.  Yeah, I know they didn't bother because leaving them off means all three sprockets are identical.  Adding bolts would make for three different parts and a more complicated call-out on the instruction sheet regarding which one goes where and in what orientation.  Not a big deal, but leaving them off would be noticeable so close examination of reference photos is in order.  Takom also wants you to loop the winch cable around the large fairlead roller at the base of the crane.  While that may help hold the string in place, that isn't how the cable was routed...it ran across the top of the roller.

I'm sure I'll find/remember more as time goes on...

[dogfish7 (R.I.P.)]

NOOOOOOOO!! Not implying anything.

[JCON]

[RLFoster]

Outstanding!

[rustybaer]

I'm with Kitty up above, watching with intent to copy. I have store credit at my local hobby shop after attempting to divest myself of previous impulse buys, and it looks as if I may have some spare time soon.....

[dogfish7 (R.I.P.)]

I'm hoping Beekster gets more time also. I want to see more of his build.

[Beekster]

Some more bits and bobs have been added, though much of this is still mocked up and not glued in place.

Surprisingly, the three spare road wheels fit just fine on their stand-offs without fouling the bridge mount support beams. The fit is wobbly; I need to snip the tops of the spindles for any of these three where I intend to have a wheel mounted. I'll probably leave one or two empty; it seems to me that working with the bridge supports would be easier without those spare wheels in the way. Note the tan blackout lamp on the left fender; the second gray one from this kit was eaten by the carpet monster so an Academy Grant kit gave up a lamp. This is a place where Takom could have done as Academy did and mold the headlight, blackout light, and mounting bracket as a single piece without losing detail. Instead, the blackout lamps are a real PITA to work with and the headlight joint is fragile.



The antenna post's end is molded solid, and didn't like being drilled out for an eventual antenna. I measured it, cut it off, and drilled out the antenna base for some stainless steel tubing. With that superglued in place, the part is ready for an antenna.



On the previous image and this one, you'll notice some white material at the back. While the fit on the hull parts is really very good, slight mis-alignments can creep in and they have done so here at the back. A little strip stock and putty solves the problems, and most of this will be obscured by other fittings or mud or both.



The engine deck has a nice deep opening for the intake screen, which isn't yet fitted. But since there's nothing like an interior or firewall in here, I blanked off the opening. It will be painted black in there and the lack of an engine and other stuff won't be noticed.

I suppose that an Academy kit could provide a lot of interior stuff for this kit if one was so inclined. It could all be used as-is for a standard gun tank. For the tank retriever, there would be a lot of work to do to add the things specific to that variant, like an accurate winch. The Asuka online shop could probably help out with that, though the availability of M32 sprues to pilfer parts from is rather spotty. Doing an interior and a bridgelayer conversion together? That way lies madness, I'm sure...and I don't need any more of that.

[JCON]

One at a time!!!

[dogfish7 (R.I.P.)]

Looking amazingly good Beekster.

[JED]

I just can't keep up,great work

[ogrejohn]

Looking mighty fine Beeks! 

[Beekster]

Well, now...this will be a problem:





On the left is the big angle part which sits on the rear deck of the M31. There's stuff yet to be added, but the outer lugs for the crane legs are in place like they should be. These are used to pin the legs when the crane is trained to the rear and raised for a lift. On the right is the Resicast resin porch, which is supposed to be attached through those lugs. This is an issue with the resin engineering. It won't fit if you try to mount it with the porch mounting tabs inside the lugs; the resin flexes and will eventually break. Making new mounting tabs and putting them on the other side of the I-beams won't get them to line up either. The I-beams need to come off and be re-positioned, and they probably won't survive that. At least the thing was mastered using standard Evergreen stock, so fabricating new I-beam supports won't be difficult. So I will do that, then cut off the resin ones. Before the new ones get superglued to the underside of the porch, I will have to get the angle support finished and glued to the deck and pin the new beams to the crane lugs so that I can test whether they line up properly with the long supports which come up from the tow lugs at the bottom rear of the hull. I just knew things were going a bit too smoothly...

[JCON]

Oh boy!!!

[dogfish7 (R.I.P.)]

I have the utmost confidence in your abilities Beekster. You can do it.

[Beekster]

The challenges continue with the back porch. Making the new support beams from styrene and attaching them to the porch was pretty straightforward. And now that the angle support on the engine deck is in place it can be mocked up:

Not bad, but not great, either. Not seen here are elements of the angle bracket that aren't installed, and those are three pairs of supports for spare track support rollers. One will face forward, and that will fit just fine. The two which face aft, between the crane leg lugs supporting the porch, may foul the porch. I can either sand down the base of the V-shaped supports and keep the rollers, or modify the supports to show them empty. Not decided yet on that. The porch isn't really sitting anywhere close to level, either, even accounting for the slight forward rake of the tank.

Viewed from the back, things get interesting:

The support arms need to have their angles tweaked a bit where they attach to the underside of the porch; this will help it sit more level. But there's something else going on here. The Resicast kit depicts these elements as being bolted together, which makes a lot of sense from an engineering and assembly standpoint. The clearly visible issue here is that with the uprights pinned into the tow lugs, the uprights don't end up anywhere close to flush against the porch support beams. At a bare minimum, a visible and very long threaded rod would be visible here if the uprights are bolted through the porch support beams as Resicast depicts. And that strikes me as not very workable. The photo of a real unit seen earlier in this thread is taken from too far away to show how it was really put together, though it looks much like what Resicast intends. The parts just don't fit that way. So I have to figure that out, and I think I have worked out a method. First, I have to tack this rickety mess together with Elmer's glue on all four pin points so that I can take some measurements with the calipers. One it is stable, I can measure to make a hollow structure which will be glued to the under-porch supports and able to butt up against the sides of uprights. These would in theory be welded to the under-porch supports, and be drilled to accept a bolt through the upright.

Either that, or the way the uprights attach to the tow lugs has to change. I'll look at that too, but the first hurdle there is ensuring that the supports clear the idler mounts and that means an offset somewhere. If that's what is required, I might as well build entirely new uprights. More staring and thinking is in order...

[Beekster]

And something of an epiphany already! I understand why I have the gap I do on the left side. Why? The tank is asymmetric; the uprights are symmetric...and the instructions aren't clear. Looking at the rear shot above, we see that the tow lugs are positioned symmetrically, spaced out from the tank centerline just as the Ordnance drawings (and the kit instructions) specify. The crane leg lugs on the big angle, however are not symmetric with the tank centerline. And that too is as it should be, because the turret is off center. Well, of course! The crane leg lugs are located where they are so that the crane, when secured in them, faces dead aft parallel to the tank centerline. If the porch is built so that it lines up across the width of the rear hull and is attached to the crane lugs, there's no way the left upright can attach to the tow lug.

Some additional fiddling and adding some styrene strip to the right side upright will get the fit on that side flush with the porch support, and I might even be able to engineer a standard plastic glue joint there. Once I'm happy with that, I can do a mirror image of that work on the left upright and have the joints with the porch supports worked out. The resolution of the asymmetry with the left tow lug will be accomplished at the bottom end, by adding material to make it fit correctly.