M911 & M747 on Civvie street

[BUCKY]

Nice going on the trailer deck! Things are looking great!!

[dogfish7 (R.I.P.)]

Fenominal details on the cab! Even the pull chain.

[BUCKY]

I hope ya don't accidentally hit that pull chain! You'll scare yerself away from the workbench!! LOL

[ogrejohn]

This is really shaping up nicely! 

[Beekster]

Bits and pieces: I reinforced the etched brass steps for the passenger side fuel tank with .005" sheet so that I could get a regular plastic join for the steps to the tank. Superglue wasn't going to hold for parts hanging out in the breeze like this. Also notice the sheet styrene shim on the fender:

I picked up some model magazine back issues from Squadron recently, and one of them has a build of Meng's version of this kit. I noticed that their kit parts have panels like this between the fender support arms, which naturally adds strength to the parts. So I added them to mine, and will soon put this fender back into place.

Here's the spare tire mount & crane; pretty simple assembly with one flaw: The small pulley is on top is molded as a solid lump, seen off to the side. I made a proper pulley with punched discs and mounted it between two sheet styrene side rails and an end plate.




Now for the bad news: The trailer has issues. Those inner frame rails seemed to be square and flat when initially assembled with the cross members, though the snatch block housing at the back didnt' fit well. But once the deck was on, things went awry and the right side of the deck bows upwards at the rear. Viewed side on, the whole deck also seems to bow slightly downward in the middle and up at the ends, the opposite of what a lowboy ought to do (they flex up in the middle when empty, flatten out with a load...by design).





I've cut out the snatch block housing and will keep trying to work with this, but there's something strange about the assembly sequence which allows this to happen and I'm not sure what it is. At least I have a spare trailer to work with if this one can't be wrestled back into a flat condition. The warp will affect how the wheels sit, since the trailer suspension mounts to the underside of the deck. The deck is kept flat by sprues bracing it on the inside, but of course those have to come off to assemble the thing and time sitting without the bracing might be a cause of the warpage. Worst case is I will have to scrap the trailer, salvaging what I can to scratchbuild a generic civilian lowboy. I really don't want to do that, since the suspension and wheels from the M747 are truly off-road units, and of a size not commonly seen on civilian trailers. Stay tuned...

[JCON]

Nice upgrades!!

[BUCKY]

Hopefully, you'll be able to overcome the problem with the trailer. It almost sounds like the deck was molded upside down.

[JCON]

Any way to glue weights to the underside to pull it down?

[Beekster]

Apr 15, 2019 0:04:23 GMT -6 JCON said:

Any way to glue weights to the underside to pull it down?

Afraid not.  The warp is most prominent at the rear, where the wheel stations are supposed to go.  There's no available real estate.  Based on sprue images, Meng arranges the trailer parts differently, with the bottom seemingly being a foundation piece on which everything is constructed.  Hobby Boss, on the other hand, has you start with building an inner frame then adding this to the deck, working upside down.  I'm sure the warp happened somewhere in there; perhaps the inner side rails need to be glued to the underside of the deck first with the deck held on a flat surface.  I don't really know.  For the moment, I'm going to ponder the problem, concentrate on the tractor, and do some math and planning for this:






Trail-Eze TE100RG, and I've got a .pdf file of the brochure with dimensions.  It's pretty simple structurally and a current design.  It also hasn't changed much over the last 25 years or so, judging by images of older trailers for sale.  The basic design can be had with two or three axles and capacities from 35 to 50 tons.  The M747 is rated for over 60, and that fourth axle is undoubtedly part of the reason.  The only real difficulty with building from scratch is the wheels; I would have to make some and have castings made.  The Trail-Eze uses 8.25 x 22.5" wheels and 225/70R22.5 tires; the M747 uses 15-19.5 high-flotation tires.  I've got some resin wheels I had cast for an eventual IDF trailer that should work, but the master patterns are missing so getting more cast might be a challenge.  The wheel design is old-school, not a modern style but ought to work if I can get more cast up:

The centers are from a MAZ-537G and the tires from a 1/32 snap-fit truck kit.

[JCON]

They look good!!!

[BUCKY]

Could you "heat treat" the trailer parts with a hair dryer, or hot water to get 'em straight? Just a thought.

[ogrejohn]

Apr 15, 2019 13:22:07 GMT -6 BUCKY said:

Could you "heat treat" the trailer parts with a hair dryer, or hot water to get 'em straight? Just a thought.

I was kind of thinking the same thing. Maybe clamp the warped part to a 1 2 3 block and heat with a blow dryer. 

[Beekster]

Well, I don't have the tools mentioned to deal with the warp so I'll put the military trailer aside for now. I think I understand how it happened, and it is likely a result of the kit engineering and assembly sequence. Those inner side rails I spent time on are part of the problem. This is that shot of the underside once again:

Those inner side rails are visible, as are the slotted rails molded on the bottom of the deck. The slots are for triangular braces to support the deck. That gap between the two rails is something like .050" wide, and there's no need for it to be there since this whole area eventually gets covered with a bottom plate. If the deck piece had been engineered with a thicker rail so that the inner rail was secured with a butt joint along the entire length, the longitudinal rigidity of the deck would be greatly increased. That would fix the fore-and-aft bow in the deck. The twist in the side might be tougher to deal with, and that's where the assembly sequence comes in. The triangular braces probably need to go in sooner, and the deck held flat with considerable weight while it dries. I've got another one to experiment with later on. Meanwhile, there's another lowboy taking shape...

[dogfish7 (R.I.P.)]

Who knew???

[Beekster]

Gentlemen, I am a rather happy boy this morning. I can't believe how well this is working out so far. Yesterday I started cutting plastic for the trailer deck frame, being quite careful to ensure that it is square and flat.  It is by no means finished, but it is far enough along to be rigid enough to start playing with other bits. I knew that a challenge would be the suspension, axles, and wheels. The latter I can crib from an unfinished IDF trailer project; I can eventually have more wheels cast. This morning I rummaged through my 1/32 scale snap-fit truck bits and found identical two-axle leaf spring assemblies from a couple of box trailers purchased ages ago for just this purpose:



This is a mock-up of these parts, spaced out for three axles. Obviously there is some transplant surgery to do to join these together properly, but that is pretty straightforward work. What floored me when I cobbled this up is that the white parts, which I found pre-assembled (but not glued) fit almost perfectly to my frame rails! The air bottles and cross members do foul my frame cross members, but that is of no consequence. I can easily chop Evergreen I-Beam stock to the proper width and replace them. See how the wheels fit, lined up on the axle locations:



This is darn good for a quick and dirty fit test; the whole assembly will be moved a bit aft eventually. The wheels will use .125" diameter tubing for the axles, and I have resin air boosters aplenty cast up for projects like this (the Madill needed them too, which is why I had them cast up).



This shot from above shows that the wheels will tuck in nicely. The trailer will scale out to 102" wide, and what you see here is .040" short of that. Side panels of .020" sheet will be cut and trimmed to form the wheel arches, and fitted with D-rings and discs for reflectors.

Ride height can eventually be adjusted by tweaking the frame where the suspension assembly will fit. That is a long way off, and will be determined by how things look when the gooseneck is built and attached and the M911 is finished enough to sit on its tires so that the trailer can be hooked up and the load deck leveled up. There's many miles to go yet, but this is a most promising start.

[BUCKY]

This is cool! I love to watch a major scratch building effort under way!

[Robbo]

Very nice work

[JCON]

That is looking nice and flat!!! Good job Brother!!!

[ogrejohn]

Nice scratch work! 

[Beekster]

The suspension patients are out of surgery now. Cobbling together a three-axle part was pretty straightforward, though some .020" strip was required on the back side to keep things stable. That won't adversely affect how far out the wheels sit, since there were square pads on the back faces about .025" thick which were mounting pads for the cross members. Those are now gone, along with the brackets that would have attached the suspension assembly to the box trailer. I'll add some plates and bolt heads for that later on. There's still cleanup to do, and the epoxy putty filling the back side of the bogies frames needs to cure until tomorrow afternoon. But I'm happy with how it is coming together.



Speaking of epoxy putty, there's more of that and thick styrene stock filling the cavernous holes in the air bottles. I don't know if I will actually use these, but while I had the materials out it seemed sensible to prepare these parts too.




Other work not seen here: Trailer deck frame progressing and set aside for glue to cure on the next phase; rattle-can flat black sprayed on the instrument panel, and primer on the cab interior parts otherwise.