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Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #55992

The body of the Mammoth, while massive, is very simple to assemble. There are only a handful of parts, the largest by far being the bed. A couple of metal rails are attached laterally followed by another pair with slots longitudinally. The slots clip over the bar on the lift actuator as shown. The whole thing hinges around the rear of the chassis. Although everything is already molded in yellow, I used two cans of Camel Yellow paint to make it look more real. I top coated with Semi-Gloss Clear.
The left hand picture shows the assembly of the front and rear light buckets. Each tail lights has slots for two 5mm LEDs, and there are room for seven up front. The right hand picture shows the front light bucket installation from behind the grill, and you can also see the mesh I installed to add some contrast to the otherwise monochrome front grille.
These pictures show the front grille before and after I installed the mesh. The change is subtle but I like it much better with that black layer behind. I also painted all the little rivets black for a bit of extra visual detail. It is interesting to note that the headlights are not in the places you would normally expect. Those 2 big yellow cans on either side are not headlights, they are intake air filters for the huge turbos which feed the generator.
There are a couple of large parts which make up the upper deck. The box furthest to the right is the operator cabin. There isn't any kind of interior in it. The instructions call the box on the left a generator, but it can't possibly the primary generator that powers the truck. I don't know about the middle box. If there's one complaint I have about this body it is the general lack of detail. There is a lot of open flat slabs of space with no texture. Perhaps this is an accurate representation of the real thing though.
The last details to add to the body are a set of plastic and metal hand rails. These do a lot to break up the large open areas. Finally, the whole thing can be installed to the chassis with just four screws. I considered omitting the front bumper, but it leaves the overhanging body too susceptible to damage.
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Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #55993

There wasn't much of anything I wanted to upgrade on this truck, but I did feel like it needed a lighting system. There was an original Tamiya lighting system using incandescent bulbs made especially for the Mammoth, but it is nearly impossible to find now. I figured I would use the old standby TLU-01 system instead. I used halogen colored lights in front. The lights come in pairs, but there are only 7 light buckets so I had one spare. On the right you can see that installed it into the bottom of the cabin for a little interior light. Now it needs an interior!
Now I need to find a place to install the lighting controller. This box on the left of the chassis has plenty of room and was originally intended to hold the radio battery box for the Juggernaut. With some creative Dremel work, there is plenty of room for the controller. With the cover on, you can't even tell that it is in there.
Here you can see the installed location of the lighting box without the cover. There is an amazingly large amount of wiring on this model.
Here are a couple of photos of the completed lighting. 7 lights in front and 4 in back. Looks much better this way.
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Last edit: by blakbird.

Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #55994

I have to retract something I said earlier. I said that the hex support in the gearbox was the only difference between the Juggernaut and the Juggernaut 2. That is not correct; there is also a change in the axles that I didn't notice. I'll be adding the text below when I do my formal review.

For one last diversion, let's look at the other change between the Juggernaut and the Juggernaut 2 which impacts the axles.  Looking at the below image, you can see that the original model used small bevel gears on the axle which had bearings on only one side.  This is a really bad design for high torque.  The newer axle greatly enlarged the size of the gears as well as adding a small bearing to the opposite side of each gear.
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Last edit: by blakbird.

Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #55999

No other model has quite the visual impact of this truck. Yes, there was a wheelie dump truck later, but it was not a true scale model, was not 4WD, and was nowhere near this size. This model stands alone as its own thing. It is slow, heavy, accurate, massive, and awesome.
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Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #56000

Now let's compare this massive model to another large Tamiya dump truck. Although they are totally different scales (1/20 vs. 1/14), they are similar in overall size.





Although this kit is not identified as a model of any specific truck, it appears to most closely resemble the Liebherr T282.
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Last edit: by blakbird.

Blakbird's 58268 Mammoth Dump Truck Build 4 years 8 months ago #56001

I started this topic before I had written my usual introduction paragraph for the model, so I'll append it here at the end.

The Mammoth Dump Truck came out in 2000 and isn't really like anything else before or since. It is based on the huge 4WD monster truck chassis from the 58232 Juggernaut, which is itself an evolution of the original 58065 Clod Buster chassis. This model throws out the Juggernaut's four wheel steering and balloon tires and instead uses flat tread haul truck tires. Haul trucks are massive, slow mining dump trucks, the largest of which are capable of carrying in the range of 400 tons of payload. The Caterpillar 797 uses an actual mechanical drivetrain, but all of the others are electrically powered from a diesel generator. It is not clear exactly which real world truck this model represents, but it is an electric model like most of the real trucks. The proportions are fairly accurate, but a real haul truck would have dual wheels on the rear axles. The model features an unusual combination of 4-link suspension with leaf springs. This is nothing like the gas cylinders used on a real haul truck, but it does provide a very stiff suspension capable of supporting a considerable payload. The model is officially rated to carry 4kg, probably based on a reasonable limit of the lift system for the dumping bed. I have put much, much more in it.

The design of this model presented some challenges to Tamiya. Prior to the 1990's, pretty much every model used a mechanical speed controller. By about 1993, most models were designed to use Tamiya's C.P.R. (which probably stands for something) electronic speed controller. This couldn't handle the power demands of this big truck though, which is why the Juggernaut still used an old mechanical speed controller. The problem with MSC's is that they convert excess voltage to heat any time you are driving at less than full throttle. A mining truck is hardly ever going to be at full throttle which means the poor resistor would probably burst into flames. As a compromise, this model contains the "Mechatronic" speed controller, a bit of a hybrid which is unique to this model. It still uses a servo for throttle like an old MSC, but that servo turns a crank on an electronic board holding a FET resulting in real proportional control without a resistor. The system is crude my modern standards but actually works well enough that I decided not to replace it. The next challenge was the need for an extra channel. Most radios of the time were limited to 2 channels, but a 3rd channel is required to control the lifting bed. This is easily solved with a 3 channel system today, but Tamiya worked around that by including a "Plus 1ch" control unit which allows the steering (channel 1) to control the lift under certain conditions. Finally, although the Juggernaut was not exactly fast, it was geared too high for a haul truck. To solve this, Tamiya engineers removed the twin motor mount and replaced it with a single motor and extra stage of gear reduction. Taken together, these three innovations made for a very capable and unique truck.

With four wheel drive, open differentials, and limited articulation, this thing can handle mild off-roading (grass) but not much more. While there is ample ground clearance between the axles, the front bumper and grille are very close to the ground so obstacles are a problem. This thing is really just for driving around the mine site. The lift system for the bed is quite powerful. I stacked it to the brim with rocks from my garden. The suspension was able to handle it and the bed dumped without complaint. There are no foams in the tires, but the sidewalls appear stiff enough to support the weight even when loaded.

So who bought this thing? Apparently no one. The first problem is that the Juggernaut chassis had earned a bad reputation due to failing gears. This was fixed with the Juggernaut 2 (on which the Mammoth is technically based), but the damage to the reputation was done. Beyond that, this doesn't have the same kind of appeal as a monster truck or buggy. It is big and slow and lumbering. You can't race it or jump it or even off-road it. You have to drive it like a dump truck. For all of these reasons the Mammoth is hard to find and costs a fortune. I searched for a long time to find this one, but I am just the kind of strange customer who actually appreciates it. I left it stock except for the addition of a lighting kit and a modern radio.

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