1/160 1920 Macdonald 5 ton low bed truck

[mecklm]

Here is truck #2 in my project of creating 1910's - 1930's vintage trucks in 1/160 (N scale). There is a distinct lack of era correct trucks for those early years. 

This truck, the 1920 Macdonald low bed, ranks right up there as one of my favorite trucks of all time. It is a purpose built vehicle designed to carry heavy loads and provide an extremely low bed height. The way this was accomplished was by eliminating the drive train to the rear wheels and instead, powering the front wheels. 

As such, the main frame consists of heavy timbers laid side by side that ride mere inches off the ground. There is a complete lack of rear suspension, replaced  with stub axles on short timber uprights to fasten the wheels. 

As simple as the rear is, that's how complex the front is, which gives this truck the character I love. 

Two of the main timbers extend forward under the cab and serve as the mount for a secondary frame that supports the engine/cab unit. This secondary frame is suspended from quarter elliptic leaf springs, affording the driver at least some sort of suspension. 

The front of the cab is fairly conventional with radiator followed by engine then firewall and driver's cab. Where it deviates from the norm is the "rear" axle, which is the type used on chain drive trucks but, in this case,  is located right under the driver's seat. 

The cool part is the chains run forward to the front wheels. This is accomplished by using a planetary hub at the wheel. Dead center is the normal kingpin for steering but since the hub is planetary, the stub shaft of the front sprocket is mounted eccentrically, directly above the kingpin. A u-joint in line with the kingpin allows the front wheels to steer without introducing any weird motion to the chain. 

From what I understand,  these trucks saw duty on west coast harbors, no doubt handling the heaviest loads coming off the ships. 

In order to create my model in 1/160 scale, I once again designed a 3d CAD file in Solidworks. Given the small size, many features had to be made oversized in order to just barely exceed the minimum print capabilities that Shapeways can provide. Here is the finished assembly file, an exploded view showing the part breakdown and the STL configuration where the parts are joined together with a sprue. 

Nine of the parts are printed with the remainder being the shift levers, parking brake handle and the front window glazing. 

Next update will present the printed file and the prep work leading up to detail painting. 

Mike 

[Chariots of Fire]

I can't imagine doing this one in 1/160 scale!  A friend of mine did this one in 1/25 scale a number of years ago from drawings that he obtained.  It took a lot of study just to figure out where everything needed to go.  It is scratch built.

[Modeltruckbuilder]

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Edited December 27, 2017 by Modeltruckbuilder

[mecklm]

Yes, same truck. I came across another scratch built one in white. I think that one was 1:12 or 1:16 scale. I'll have more pics up soon. I did not,  however, model all of the individual stakes, just so you know. Just doing the two behind the cab and the four that hold the rear fenders was enough. 

Mike 

[mecklm]

So, clean up was the same as the International,  starting with a 24hr soak in diluted Dawn dish detergent. 

This was followed with gray primer. 

Next, I sprayed everything but the main frame in what Vallejo calls Azure - just a nice light blue in my semi-color blind eye. This happened to be the same day my Molotow pen showed up so I chromed the radiator cap, steering wheel spokes and the acetylene tank on top of the dashboard. 

Here the grill is detailed with dark gray. I also sprayed the main frame the same shade of gray. 

The wire dangling from the main frame is three strands of wire that I pulled from some super small gauge wire I have laying around. I drilled a hole in the side of the winch drum, inserted these three strands, twisted them and then wrapped a few turns around the drum just to add a little character to that area of the truck. 

Here the detail painting of the cab is complete. 

Next installment covers the washes and dry brushing. 

Mike 

[mecklm]

Here two different washes were applied, since I wanted to portray a heavily used but well maintained truck. The first was an overall wash of a medium/light gray. The second was a black wash focused on the cracks, crevices and corners. I did include the windshield with the gray wash. 

The washes were followed by two dry brushing sessions, the first hitting the main panels with a lightened shade of the base blue color. The second session involved pure white applied to the high points and all outside corners.

A light dry brushing of flat earth added a bit of a dirty tone to the truck. These techniques were then applied to the rest of the blue parts. 

Next installment I'll detail the main frame, including putting a wood finish on the top side of the planks. 

Mike 

[mecklm]

Here is the first step in creating a natural wood finish on the top side of the main frame timbers. I use the Vallejo wood and leather paint set which includes easy to follow instructions to create a pretty realistic finish. Unfortunately I only have photos of the first step of the painting process and ultimately the final finish.

Here's a close up of the winch area of the main frame giving an indication of the coarse nature of the wood painting techniques. The winch and cable have been detailed with plain silver paint and a black wash. 

The underside of the main frame timbers got a sepia wash, which gives a nice indication of greasy, oily stains. To finish off the main frame, I brush painted the outer edges dark gray and picked out some steel reinforcing strips near the rear of the frame with a silver paint darkened with some black.

The front bumper got the simulated wood finish also and the overall frame was dry brushed with pure white, again with the focus being on the edges and corners. 

Next up is a minor detail followed by the final assembly. 

Mike 

Edited November 12, 2017 by mecklm

[mecklm]

The plans I worked from indicated three separate shift levers. I wasn't able to discern if one of them was actually a parking brake so I just made all three the same. I used 0.006" brass rod with a tiny ball of white glue on ends to simulate the knobs. Here they are stuck in a bit of silly putty to facilitate painting. I just used plain silver for the rods and dark gray for the knobs. There are three holes formed in the cab floor that measure roughly 0.010" in diameter.

Next, and last, is the final assembly of all the parts. I should also mention that I didn't acknowledge the baking soda blasting in my post above. The blasting comes after the 24hr soak and prior to the application of the gray primer. 

Mike 

[mecklm]

I only have these photos of the final assembly stage, basically everything attached to the main frame except the cab. I use super glue at all the joints to hold the truck together. My preference is to dry fit each part and then apply super glue to the joint to finish it off. I'm sure lots of folks here use the same applicator that I do - a small sewing needle that has exactly half of the eye cut or ground away. This leaves a miniature two pronged fork that holds a very precise and repeatable amount of super glue. I stick the pointy end of the needle into a small scrap of wood to serve as a handle. 

And here are a few final shots, at least until I get my photo booth set up again for "under glass" pictures. 

Mike 

[mecklm]

Hey Charles, thanks for posting the photo of your friend's rendition of this truck. I couldn't help but join these two photos together for a comparison shot, given the general size, position, perspective and even the angle that the front wheels are steered to are remarkably similar between the two. The cool thing is the top one is roughly 11-1/2" long while the bottom one is just under 1-3/4" long.

Mike 

[Chariots of Fire]

That's a neat comparison.  Here's another one that Jeff did.  An early Federal that was used by the Cape Cod Shipbuilding Co.  The company is still around building fiberglas boats.  During WWII they built boats for the Navy.

1/25 scale Federal from photos found on line and one early Cape Cod Ship photo that showed some of their detail.