Blakbird's 56336 King Hauler Build 2 years 3 months ago #54305

Note: The King Hauler was the first R/C kit I ever built (I was not smart enough to know to start small). The following excerpt from my web site records the build and my observations at the time. I've made a few updates to the language since then as I've learned what I'm talking about.

2017 saw a resurgence in my interest in the Radio Control Hobby. I got a couple of Traxxas Ready-to-Run models for the kids and then decided to go full blown into kit building. Although being interested in R/C as a kid and intermittently as an adult, I had never built a Tamiya model before. Never one to start small, I decided on a 1/14 scale tractor trailer combo with all the options and upgrades I could find. The pages below chronicle the journey of my build.

The 56301 King Hauler was Tamiya's first ever 1/14 scale tractor truck and was released in 1993. They would then go on to progressively release another new truck approximately every 1.5 years until by 2019 there were a total of 18 different models. The early models were unlicensed generic cabs, but it wasn't long until Mercedes Benz, Ford, Volvo, Scania, MAN, and Freightliner were added to the mix. Of those 18 trucks, a few are derivative such as 4x2 and 6x4 versions of the same cab or box and tractor truck variants of the same cab, but most of them are unique cabs sharing a mostly common chassis. The King Hauler and all the other 6x4's have dual rear differentials with tandem dually axles and a three speed gearbox. The gearbox is essentially unchanged in all that time, and for the most part the chassis is as well. There are some servo mounting differences between longnose and cabover varieties. It is quite amazing that, as of 2019, virtually all of these varieties are still available in at least one form or another so it is a pretty simple matter to collect them all (if you can come up with the money). Apart from their extreme realism in appearance, one of the best things about the tractor trucks is the ability to add the MFC (Multi-Function Control Unit) which adds dozens of lights, engine sounds, and vibration features to the model. Once the MFC is installed, these are insanely fun to drive because they look and sound truly magnificent.

I used the "Euro-Style" MFC-03 because it was the most current. I didn't realize at the time that it has different sounds than the old MFC-01 which sounds more "American" so I'll probably go back and it swap it out later when I build another tractor truck. The 56511 MFC-01 came out in 2003. The 53957 MFC-02 is for the Highlift series of 1/10 trucks, and the 56523 MFC-03 came out in 2014 (without a whole lot in the way of changes). This means that there was no MFC available when the King Hauler came out in the dark ages (electronically speaking) of 1993. Instead there was the 56501 Tractor Truck Electrical Unit Set which contained lights and a backup beeper (full of incandescent lights, switches, ribbon cables, terminal blocks, and circuit boards) and the separately available 56510 Tractor Truck Sound Unit.

To be honest, I didn't know any of what I wrote above when I bought this model. I just chose the King Hauler because it looked cool and was available. As it turns out, the 56336 metallic black version had been released in 2013 and was still easy to find. I didn't know the King Hauler was the oldest and, in some ways, the simplest. The MFC didn't exist when the King Hauler was first released which made installation a little tricky, but that was part of the fun.

The King Hauler is a classic American long nose tractor truck which is not a licensed scale model of any particular brand. I got the pre-painted black edition. Also on the table you can see a 4 channel transmitter, MFC-03 (more on that later), a fuel tank trailer, trailer lights, motorized trailer legs, oil shocks, and a battery. Although I have lots of Li-Po batteries, I didn't have any 6-cell NiMH stick packs needed for Tamiya models so I picked up a 5000 MaH model from Venom. Everything you see here was ordered through Tower Hobbies. It was insane to choose all of this as a first project, but I had done my research and was confident I had the right stuff on the table to make an amazing model. If I didn't screw it up.
Here's the large, impressive box. Don't let the red color fool you, there's a "Black Edition" sticker on the upper right. Being new to Tamiya and this model, I had no idea whether the chrome in the picture was really chrome or how much of the model was plastic versus metal. To my regret, I threw away the box when I was done but now I wish I had kept it for posterity since the classic Tamiya box art is so excellent.
Here are some images from the sides of the box. The first shows a cutaway internal view of all the mechanical and electrical details. The second shows the 3-speed transmission, a detail I was excited to build so I could learn how it works. I had no idea that this one of the most complex mechanical systems in classic R/C, though the original Bruiser transmission is much trickier. Keep an eye on those gear ratios listed. I'll be trying to derive and match them later.
A side view and top view of the internals. There is a lot going on here, too much to absorb from just a couple of images. It gives a clear impression that there are going to be many interesting details to build though. This is not just a static plastic model even though it looks as good as one. The combination of scale accuracy and technical function is what attracted me to this model. That left hand image makes it look like there is a lot of open space inside the cab shell, but once the MFC is added it will be stuffed full.
So what's inside the box? Quite a lot, and very nicely packaged. You can see a blister pack for many of the main chassis parts, a special slot for the tires, some plastic trees, and the frame rails in the middle. Next come the metal parts. The C-channel frame rails have a protective film over them, probably to protect the finish during drilling and tapping. The holes are all pre-drilled, and there is no drilling required anywhere in the model. Behind the rails is a blister box revealing metal shocks, leaf springs, differentials, exhaust stacks, and other parts.

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54306

Now the molded parts. You can see a lot of plated trees as well as the pre-painted one piece body. The second image shows some of the smaller parts including the wheels and a bag of gears. I immediately noticed that, unlike most plastic models, there are many different kinds of plastic here. Gears seem to be nylon, some parts are styrene, tough parts are ABS, and I think some may even have chopped glass fibers in them for strength. I like the engineering that went into making each material right for the part.
This box contains the tires. There are 10 tires in the model, but only 8 here on the top level. The others are inside the box. Finally comes the hardware. Pretty much everything you see bagged here is metal. The screws, nuts, and other fasteners are inside labelled bags to make it easier to find what you are looking for. Each step in the manual begins with a hardware parts list showing what is needed for that step. After collecting the hardware, you can start finding the required plastic and metal parts. Having the parts list per step helps ensure that you don't miss anything.

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54307

Step 1 starts nice and easy with the installation of some servo horns. I chose cheap and simple HiTec HS-311 standard servos with 49 in-oz of torque for both steering and shifting. Arguably these are a little too cheap, but I've had no problems so far. This model is only going to be driven on pavement so the torque requirements are low. I suppose the gears will wear out and there are no bearings in the servo so I'll have to replace them eventually. The model comes with three sets of control horns accommodating servos with 23 or 25 tooth splines. HiTec is an oddball and uses 24 which I didn't know when I bought the servos. Luckily, the 25 tooth Futaba horns seem to work OK at these low torque levels. There's a servo saver and a ball connector installed on each. Notice that the neutral orientation is different. In hindsight I'm amazed that such a crappy servo actually worked for this heavy model, especially using a servo horn that didn't even have the right number of teeth.
Step 2 connects the servos to a couple of cross members. Although the model can accommodate installation of slightly longer or shorter servos in the frame, it is important they both be the same size. Also notice that the rubber mounting grommets are not used. The servos are mounted directly to the cross members.
Step 3 builds a couple of cross members for the frame from high strength plastic.
Step 4 introduces the first metal parts, the frame rails. These are straight C-channels and seemed to be formed sheet metal rather than extrusion. They are pre-drilled, tapped, and powder coated. The coating is durable but will scratch if you nick it with your X-Acto knife. This steps installs the rails, the cross members, the suspension mounts, and some brackets.

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54314

Step 5 builds the rear leaf springs. Each semi-elliptical spring contains 3 leaves which are cross bolted and then clamped with U-bolts.
Step 6 installs the rear springs to the chassis. The spring needs to be able to pivot because it is going to be supporting both rear axles. It is installed with a shoulder bolt which prevents the possibility of over-tightening which would prevent free rotation.
Step 7 builds the rear differentials. All of the internal gears, the housing, the ring gear, and the carrier are metal. The kit comes with ceramic grease to lubricate the gears and make them run smooth. This a true open diff with almost no resistance, so you will lose traction quickly if any wheels come off the ground. The fact that both rear axles are powered helps. It is possible to use Tamiya anti-wear grease instead of ceramic grease to increase resistance so the gears don't slip so easily, but I didn't find out about this until after my build. On pavement it doesn't really matter, but if you want to drive some scale logging roads you may want to do the mod.
Now it is time to start building axles. I had read that this model comes with bushings rather than ball bearings, which is correct. You can see the bronze bushings in the bag. I went ahead and ordered a full set of rubber sealed ball bearings from Advantage Racing and installed them right away. It is unfortunate that I never even tried but the stock setup, but I don't regret the upgrade.
Step 8 builds 3 sides of the axle housings. Why 3? The front side of both axles is the same, containing a pinion gear and a bearing. However, the front axle also has a pinion coming out the back to go the rear axle, while the rear axle has nothing on the back. Keeping the parts straight was actually a bit tricky because they are so similar.

Step 9 builds the live axles. Each axle consists of a metal splined shaft with snap ring grooves. The splines are inserted into the sockets in the differentials, and E-clips secure the bearings.

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Last edit: by blakbird.

Blakbird's 56336 King Hauler Build 2 years 3 months ago #54315

Step 10 installs the axles into the housings. Here you can clearly see the difference between the 2nd and 3rd axles.
Step 11 installs the axles by bolting them to the ends of the leaf springs. This is a good time to mention the importance of thread lock. All these metal parts are subject to vibration and the screws will back out if they are not locked.
Step 12 installs the plastic radius arms and the rear drive shaft.
At this point I ran into a problem: the axles did not attach properly. Something was misaligned and the suspension would not articulate smoothly. I did not want to continue building without resolving the problem. It took me a while to discover the cause, but the first image shows it. The leaf springs were not parallel to the clamps. In the first image the clamp is flat on table but the spring has a significant slope to it (gapped on the right). The second image shows how much I had to tear apart to fix the problem. Thankfully, since everything is screwed together it can be disassembled and reassembled easily.
Now everything is straight and true and works much better.
Step 13 builds the "dampers". The dampers that come with the kit don't really damp at all. They are just spring cartridges and are mostly for show. I ordered 3 sets of the hopup oil dampers from Tamiya to use instead. I was a bit worried when I saw that the stock dampers were sprung, because I feared the unsprung oil dampers would effect the ride height. However, the spring force in the dampers is very small so it doesn't really matter. The first image shows the parts needed to build the stock dampers which include aluminum housings. The oil dampers must be built up from plastic and aluminum parts, filled, and bled.

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54316

This image compares the completed oil dampers with the stock dampers. Other than the color, they look no different from the outside. Having now built and driven the model, I can say that this upgrade is probably unnecessary. The oil dampers are quite expensive and given that this model will only be driven on pavement anyway I doubt the handling will be noticeably different. With that being said, I never actually tried it with the stock dampers so I can't be sure.
Step 14 installs the dampers. Bushings and/or shoulder bolts are used to prevent clamping down on the shock ends. I have to say, I love the way this suspension moves and sounds with the weight of the metal.
Step 15 builds the tie rods which must be very specific lengths. You can see that two of them have open ball connector ends while the 3rd has closed ends for smaller balls. Looking back on this later, I am amazed at the tiny diameter of these rods for such a big, heavy model. I've never had the slightest problem with them though.
Step 16 installs the steering and shift rods along with the front dampers.
Step 17 connects the solid (plastic) front axle to the leaf springs and also builds the steering arms.
Step 18 installs the front axle to the chassis using the leaf springs and some shackles.
Step 19 installs the steering arms using simple vertical kingpins. The long steering rod connecting the left and right arms is also installed. It is important to get this length right so the axles are parallel unless you want some toe in your alignment. It is nice to see that the steering link is behind the axle so it won't hang up on anything when driving off road.

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54333

The transmission is usually my favorite part. I love to see how different manufacturers handle the design, even in the case of a transmission with only one speed. In this case, the 3-speed transmission is advertised as shift on the fly, so I want to see how they do it.

Step 20 builds gear shaft A. All 4 of the gears on this shaft are locked to the shaft with splines. From left to right, the gears are 27, 20, 13, and 36 teeth. The two smaller gears are metal (apparently aluminum) and the larger gears are nylon. All have wide faces. Shaft A, specifically the 36 tooth spur gear, is driven directly by the motor so this is the input.
Shaft B is the output and is built in Step 21. There's a lot more going on here. From left to right, the gears are 30, 38, and 44 teeth. All 3 of these gears ride on bearings so none of them are locked to the shaft. Instead, the 3 driving rings are splined to the shaft. The shift forks will translate the driving rings and cause them to mesh with one, and only one, gear at a time. The driving rings mesh with the gears through 3 driving dogs which allows them to be engaged and disengaged while in motion, though obviously there will be greater dynamic forces on the gears if shifted while moving.
Step 22 builds the shift rod. The three forks will engage the driving rings and must be able to translate them along shaft B. It is important that the friction be low in the jaws. This rod will be driven by the shift servo.
Step 23 begins the assembly of the gearbox supports. The 3 rods shown are just structural spacers. The end plates will house bearings to support the shafts.
Step 24 installs shaft A, shaft B, and the shift rod and closes out the gearbox. Everything needs to be aligned and smooth running at this point. I installed full ball bearings at this point. Some later tractor truck instructions specifically recommend not installing ball bearings on the sliding driving rings, presumably because the hard steel bearing races can gall to the shaft. The King Hauler instructions do not have this warning and I've had no problems.
Now the Mabuchi 27 turn 540 brushed motor is installed in Step 25, completing the gearbox. Looking at the 3 gear meshes, the reduction ratios are:
  • 1st - 44:13 = 3.38:1
  • 2nd - 38:20 = 1.9:1
  • 3rd - 30:27 = 1.11:1
So there is a substantial difference between gears. Of course these are only the transmission ratios. The motor uses a 10 tooth pinion so the motor ratio is 36:10 = 3.6:1. The final drive ratio in the differential is 40:15 = 2.67:1 (if I'm counting the teeth right). So the final ratios are:
  • 1st - 3.38 * 3.6 * 2.67 = 32.49:1
  • 2nd - 1.9 * 3.6 * 2.67 = 18.24:1
  • 3rd - 1.11 * 3.6 * 2.67 = 10.67:1
This almost matches what's on the box, but for some reason 2nd gear is off by 3%. I suspect they used 37 teeth instead of 38 for their math because then you get their number. After some further investigation, the middle gear actually has 37 teeth even though the manual says 38. So the box has the right ratios but the manual has the wrong description of the gear.
Step 26 puts a protective housing around the transmission to enclose it after everything has been well greased. I must have used too much grease in my axles because mine was already gone when I got to this point so I used some Traxxas grease. It is shame that all this mechanical goodness is hidden. I almost wish the housing was transparent but I suppose then you would just see grease.
Step 27 installs the transmission into the chassis along with the main drive shaft. At this point, all the main running gear is installed and it is possible to fire up the motor and watch the chassis run.
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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54341

I build one also myself a few years back.
To be honest. I enjoyed the build more than running it :-)
I'm gonna follow this thread cause ot really brings back good memories :y:
Here are a few pics of mine.
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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54342

My dad has the king hauler with the shell trailer and me the aeromax with the classic trailer. A pure pleasure to build.
I owned official protos photos of the king hauler some years ago. ;)

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Blakbird's 56336 King Hauler Build 2 years 3 months ago #54343

I build one also myself a few years back.

Love the trailer and the air deflector. Are you using aftermarket wheels?

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