Perhaps the easiest and most recognizable of US Army atomic weapons from the Pentomic Era is the Honest John tactical rocket system. Like the diminutive Davy Crockett atomic artillery round, the popular Honest John even made appearances in Godzilla movies. No 1:35 scale miniature of this impressive rocket system exists today, so, like the Davy Crockett, I resorted to scratchbuilding to render one for my expanding collection of 1950's era US atomic battlefield ordnance.

The basis for this miniature is the tactical truck itself. The M31 (basic) Honest John 276mm artillery rocket launcher was based on a M139D 6x6 5-ton cargo truck chassis. I would build this before setting out to construct the rest of the M31 Artillery Rocket System. I chose to utilize the basic components from Italeri's 5-ton truck model kits in this effort. Even though the Italeri models are of the modern-era BMY 5-tonner, the drive-train, axles, and frame components can be used with a little modification for rendering a M41 or M54 series 5-ton truck chassis. Many of the notes I have here are applicable if you want to render other M41 or M54 5-ton truck chassis - like for gun trucks - which is where I honed this idea!

(Note: I also use a 1:35 scale ruler (Armor Research Company) when I build miniatures - so I don't present measurements in full-sized millimeters or inches. If you don't - then you'll be converting the measurements I present here.)

The M139 5-ton chassis is a stretched version of the M54. Its 215 inch extra-long wheelbase is meant for transporting oversized bridge equipment. The M139C chassis was slightly modified to carry the tactical M289 276mm Rocket Launcher - hence the M139D designation. The M289 Launchers were all fitted to M139D chassis - there were no diesel or multi-fuel engine versions of the Launcher truck.

Respectively, the M41 and M54 5-ton chassis wheelbases are 179 inches, in comparison to the 215 inch M139. To make my 5-ton miniatures, I use Evergreen #267 .250" (1/4 inch) channel styrene stock for chassis frame rails. I also use Plastruct 1/4 inch channel too - it comes in longer lengths than the Evergreen product for the thrifty out there. Because the basic chassis frame rails in the Italeri kits are cast in different thickness (making proper frame alignment all but impossible) I substitute Evergreen channel stock in place of these parts, and then add all the detail myself. Laborious, perhaps, but it does result in a better miniature in the end. This option is far better than trying to buy two Italeri kits and then splicing additional lengths of frame channels to make a longer unit. It's considerably stronger and cheaper to use the Evergreen or Plastruct channel styrene stock.

I trimmed the two frame rails for my M139D to 30 feet 3 inches in scale - trimmed square on each end of course. This gave me about a scale inch on either end for tweaking and sanding for the final miniature's overall length. The first item I used to mate the two rails was Italeri part #4A - which I like to call "bowtie" - and I dubbed Crossmember F. The "bowtie" is used to center the rear dualie assembly, and the center of which is also one end of the wheelbase measurement. I centered the "bowtie" 6 feet 4 inches scale from the rear end of the frame rails, and glued it to the upper inside of the channel. All of the crossmembers will be glued to the top of the channel frame rails - except for Crossmember B (Radiator Mount - Italeri part #7A). I glued this to the bottom of the channel rails because I used the AFV Club Radiator. This parts hangs below the Cab and you'll need a few scale inches of clearance when mounting the Cab to the Frame Rails. The Italeri part is molded properly fit the AFV Club part fine. Take your time when adding the frame Crossmembers as you want everything to remain square and true when you flip it upside down and add wheels later on. A little patience will save headaches later.

The Italeri "bowtie" is fine to use as presented in any of their three 5-ton cargo truck kits. Consulting the Technical Manual on the M41 / M54 5-ton trucks, you'll notice the "bowtie" is somewhat more clipped on the ends in comparison. You can do so with your conversion, but I left mine as is in this effort because I wanted all the strength I could get in building the frame. I added .010" styrene sheet pieces to mimic the sections on the M139 - over top of the Italeri part. In retrospect, I could have gone ahead and clipped the ends off Italeri part #4A without a loss of strength or gluing surface after all.

After this step dried sufficiently, I proceed to add the front Crossmember. I modified Italeri part #8A by cutting away the extension and hinge detail for the modern BMY truck Cab before adding it to the frame rails. I dubbed this Crossmember A, and placed this part 4 scale inches from the front ends of the rails. Italeri part #7A (Radiator Mount - Crossmember B) was mounted 13 inches scale from the front ends of the frame rails. This one is important as it is the principal locator for your Cab Assembly coming later on in the project.

Next might be a snag for some, but you can work around it with a little intrepidity. The Italeri model kits only come with one Crossmember (part #6A) - which is fine for their BMY 5-ton truck chassis - but you'll need four more for the M139D chassis. I had four kits stashed away on the shelf meant for future gun truck projects that sacrificed these parts to this endeavor. All the Crossmembers are centered on the measurements given below too.

(You can make substitutes if you don't relish the prospect of spending some $100 dollars on Italeri model kits that you're gonna cannibalize in this effort. The Crossmember is 2' 6" scale length, and any piece of styrene stock that suits your fancy will do. Just be sure to cut all crossmembers to to same length - else you'll have a frame out of alignment.)

Crossmember E (Italeri part #6A or your own substitute) was mounted 3 inches scale ahead of the wings of the "bowtie" (Crossmember F) - towards what would be the front of the truck. Crossmember G was mounted 6 scale inches behind the wings of the "bowtie" (Crossmember F) - towards what would be the rear of the truck. Next, Crossmember D is mounted 2 scale feet ahead of Crossmember E.

At the rear of the chassis frame rails I added another modified Italeri part #8A - trimmed the same way as above for the front end - to cap off the rear (Crossmember H). The M139D in this role doesn't use the frame end Crossmember that carries the tow hitch (Italeri part #3A). For a standard 5-ton chassis, I would have used it, the clevices, and the bumperettes. Positioned just like in the Italeri instructions, I added the Brace (part #2A) in front of the Crossmember H inside the frame rails.

I didn't forget Crossmember C - this one comes later on in the frame subassembly.

Lastly, I trimmed the detail and braces off the Front Bumper (Italeri part #55A). I attached it to the front of the frame rails and made sure it was square. The thickness of the Evergreen and Plastruct channel doesn't allow you to just slip the Italeri part on, and you'll be adding the triangular-shaped braces and lifting clevices later on. The M139D in this role doesn't mount the Winch assembly - but in it's place are mounts for the Traveling A Frame assembly. This comes later on in the project.

At this point, I set the chassis frame rails aside to set properly while I cleaned up the axles and leaf springs. All Italeri kits call for some dedicated cleanup - and their 5-ton trucks aren't an exception to this rule. This took a little while. When done, I turned back to the Italeri frame rails (parts #1A and 14A) and trimmed away the mounting points for the front axle leaf springs and the rear dualies. Since I had several spare kits I wasn't concerned about destroying a set of frame rails for this purpose. However, I held on to a complete set of frame rails for frame rails to make measurements for adding equipment and fixtures.

I centered the leading front axle leaf spring mounts 1 foot 6 inches scale, and the trailing front axle mounts 5 scale feet, from the front end of the chassis frame rails. I didn't glue the trailing mounts in place to allow me to press fit the Leaf Springs (Italeri parts #25B and 26B) in place to get the distance correct. The rear dualie mounts are centered on the "bowtie" (Crossmember F) - some 9 feet 3 inches scale from the rear ends of the chassis frame rails. Attach the spanner (Italeri part #5A) per their instruction sheet. Set the chassis aside to dry with proper alignment and strength.

I then took the Front Axle (Italeri part #14B) and trimmed away all the detail for the U-brackets. A battery-powered Dremel tool is invaluable in this process. I flipped the chassis upside down and trimmed away the little locator tab on the bottom of one Leaf Spring (Italeri part #26B). Using the Evergreen channel as substitute for the Italeri parts this locator tab no longer serves its purpose. Complete Italeri's suggested Subassembly D (Front Axle) minus parts 19B, 20B, and 21A. I would fit these later on as they aren't critical to ensuring proper chassis alignment at this stage.

I attached the cleaned up Front Axle subassembly (Italeri Subassembly D) and checked alignment by setting the chassis upright and measuring the distance from the surface of the cutting mat to the top corners of the front bumper, tips of the axles, etc, to make sure it was all in the right place. This is a simple technique that comes from judging aircraft - by measuring the anhedral or dihedral of a model aircraft's wing tips and tail plane sitting on the table. A sagging tail plane looks as bad as a sagging front bumper.

Behind the front bumper, I mounted the Fender Braces that extend from the frame rails underneath the leading edges of the Cab Fenders. I used AFV Club M35A2 Deuce parts (AFV Club parts #A51) and centered them 10 scale inches from the ends of the frame rails. These Fender Braces mark the forward position of the Cab, and you could hold off on attaching them to later on in the project to ensure they meet the Fender positions properly.

Complete Italeri Subassembly A (Engine - Transmission Bell) and Subassembly B (Transfer Case) per instructions. Center Subassembly A's Engine Mounts 6 feet scale from the front ends of the frame rails. Clean up and attach Drive Shaft (Italeri part #13A) to the Transfer Case first - then when semi-set, attach this to the Transmission Bell and glue the mounts inside the frame rails. Crossmember C is attached inside the frame rails behind the Transfer Case - in this instance I mounted it 2 scale feet ahead of Crossmember D - 1 scale foot behind the Transfer Case. Normally, this Crossmember would be mounted closer to the rear of the Transfer Case, but I increased the distance backwards to make room for the Power Take-Off from the Transfer Case that connects to the Traverse Platform for the 276mm Launcher to come later in the project. This detail is not mounted in this stage of assembly.

The Front Axle Drive Shaft (Italeri part #27B) attaches per their instructions between the Transfer Case and the Front Axle, as does part #30A to the Transfer Case. Sand off all that detail on the Rear Axles like the front parts and complete Italeri Subassembly C, Subassembly E, and Subassembly F per instructions - minus parts #98C. Italeri Drive Shaft (part #31A) won't work in this conversion, naturally, because of the stretched chassis. I lopped off the joints on either end of part #31A and replaced the shaft detail with brass and aluminum tubing. This is an excellent time to stop and let everything setup properly. On my cutting mat, I attached two lengths of 1/4 inch thick styrene stock to the grid on my cutting mat with double-sided tape. These serve as alignment rails on which to set the chassis up. Siting on the axle plugs, i checked critical measurements for alignment all around the chassis subassembly. Leave the whole thing on the alignment rails overnight to set properly when any slop is adjusted and corrected. This will ensure all of your wheels will set properly on the surface of your base in the completed model, as well as all other alignment points coming in correctly.

An Alignment Jig is one of the easiest things you can do during building your truck miniature - it's cheap but pays huge dividends in the final product.

If you haven't given up on me this far - your chassis at this stage should look like the pictures below:

If yours does - take a break! I did. Go grab a beer, say hello to the wife or kids, something to prevent you from fiddling around with the model until it sets overnight.

The only piece missing from this photo is Crossmember C - which goes behind the Transfer Case. The 1/4 inch alignment rails ensure all the axle centers are at the same height and in line when observed from the top of the chassis and are of uniform height from the surface of the mat. Also shown in the photos is the in-progress Cab Subassembly - to be described on it's own page further on here. No - I didn't bother to clean up my workspace for the photos either - it ain't natural! In my little "office" I have three other such stations where I build my projects. I love the clutter - a true modeler's workspace. Behind the in-progress Cab are wheels, hubs, brake drums, fuel tanks, and a bunch of other stuff crying out for attention...

After the tedium of cleaning up the axles and leaf springs, things move along rather smoothly. For this miniature, I used a set of excellent resin tires produced by Joe Wallace. I bought these several years ago, and I don't think he produced them for wide release. His set of standard 5-ton tires (which are the 14.00 x 11 in size) are essential for any M41, M54, or modern BMY truck miniature - the woefully inadequate tires in the Italeri model kits pale in comparison. Real Model out of Europe also produces a more readily available set of standard 14.00 x 20 tires for the Italeri 5-ton truck chassis (#RMA 35023). Their set is equally as nice as the one produced by Joe Wallace, and comes with separate hubs and brake drums too. A slight improvement here it their set is that the brake drums are slotted to provide a stronger attachment point with the Italeri hubs. The tires themselves are remarkably similar in appearance.

In this next sequence, I added the small details and fixtures to the chassis frame, and cleaned up the hubs & tires for test fitting to the miniature. For the electrical, fuel, and air lines snaking through the frame I opted to go with Verlinden Flexible Tubing. I love this stuff. It is doubly nice for this application because of its weathered gray appearance. The M139D truck's chassis is exposed in places as the 279mm Rocket Launcher wasn't designed to cover the entire frame like the M4 LaCrosse Guided Missile Launcher was. Instead of going into deep detail, I'll include photos and brief notes on the fixtures I added.

I did mount the hubs permanently to the axles, but not the tires. These would be painted separately from the frame, and mated later on in the assembly of my miniature truck. The only detail I added to the hubs were brake lines, and air valve stems to the tires made from lengths of .010" brass wire. To wrap up building the chassis, I permanently attached the finished and weathered wheels. The Cab and Launcher sections would be built and painted separately - all joined together in the end assembly.