Adding Air Brake Lines to AMT's 1/25 scale Van Trailer

Air brake lines on model trucks are similar to brake rigging on model railroad rolling stock: A subtle detail but one that helps a model look "complete".

Compared to trucks, trailers are much less complicated and are a good "first project" for adding air brake lines and related detail.

I am using AMT's Fruehauf 40' van trailer in this example, assembling the kit mostly stock with the exception of changing wheels to 5 hole steel disk and hubs to a different style of oil hub. The basic "foundation brake" parts provided in the kit are well done and consist of air tank, brake valve, slack adjuster/pushrod assembly and brake chamber.

Reference photos of the 1:1 subject being modelled are a great guide, and I remember photographing a trailer years ago (back in 2014) which was pretty much a dead ringer for the kit, shown at 0:30.

0:45 even that oddly shaped piece AMT calls "air hose bracket" is is present.

0:57 Adding two .020" brass wire pins provides a better attachment point than the plastic projections molded onto the part. Short pieces of 1/16" dia. aluminum tube, cut approx. 040" long, are glued in place to represent metal fittings on the brake hoses.

Kit's air tank is accurate and brake valve is reasonably well done but missing a couple items as seen at 1:12 - port for two air lines coming onto the valve, and a rounded contour on top instead of the hollow kit part. At 1:35 a similar valve on a different trailer is shown with rounded top visible. AMT's four lines out the bottom is accurate, one goes to each brake chamber.

2:00 kit part with chrome removed and modified with 1/8" styrene rod domes top (drilled out hollow area with 1/8" drill) and .060" x .060" styrene strip for two air lines into valve. This is not 100% accurate but looks convincing enough when assembled. All air line locations receive .020" brass wire pins and 1/16" aluminum tube "fittings".

Installed on air tank. Kit brake chambers also get brass wire pins and aluminum tube "fittings". Two short pieces of .030" styrene rod were added on either side of brake chamber to simulate the bolts which clamp two halves of chamber together. At 2:40 one of these clamp bolts is visible on brake chamber, as well as air hose coming into the top of chamber. Some brake chambers have the hose going to centre of chamber and this trailer actually has two of each style on it as seen at 3:04.

Note that this single hose brake chamber has no provision for parking brake, and starting around 1975 trailers were required to be fitted with the "piggyback" style brake chamber with spring parking brake, visibly different by being longer and with two hoses going into it as shown at 3:32. Most of AMT's trailers were tooled in the early 1970's when the single hose style brake chamber was in use however their 40' flatbed trailer kit does have spring brake style chambers.

At 3:47 kit supplied air hose material is installed. You can also create hoses by stripping insulation off suitable gauge black electrical wire.

At 4:04 a bolt head casting and small piece of .010" x .020" styrene strip simulate drain valve on bottom of air tank.

Underside view of suspension at 4:20 shows routing of air hoses. These can be installed now and painted with rest of suspension, or removed and reinstalled after painting. Using the brass wire pins makes this option easier.

4:42 shows how the hoses connect to trailer air lines that run along floor at centre of trailer. Clamp that attaches hoses to tension spring was made using 3/32" styrene tube and .030" rod as shown at 5:07. Tension spring is coiled from 32 gauge craft wire and air lines along floor are represented by sections of .032" dia solder cut to fit between crossmembers. These, along with pieces of wire to represent electrical cable, are glued in place and provide a visual representation of lines running along trailer floor.

A last item to create, if desired, is the connections at front of trailer. 6:49 shows real trailer's air and electrical connections and 7:02 is a view of the molded in detail - accurate in every respect, just very shallow in relief. This was scraped off 7:16 and trailer plug receptacle drilled out. 7:35 a plug cover is made from .010" styrene sheet disk with one side filled flat, bent plate at bottom of trailer replicated with .016" sheet aluminum, and .032" solder "wire" runs from plug down to bottom of trailer. .020" brass wire pins will receive air hoses. 8:02 swiveling glad hands were the most work, and are aftermarket resin "air glad hands connected" (Plaskit) on elbows soldered from 3/64" brass tube. These mount to channels made by cutting down 1/8" styrene square tube. 8:30 hoses are the easiest part, kit air hose material with .032" craft wire springs.

Give these air brake related details a try on your next model!

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