Mammoth Dump Truck
Model Number: 58268

miramar

Can a slow 1/20 scale model be fun? Yes! IF the subject chosen is an enormous dumper you end up with one mighty model even in this small scale. As most of you probably know, the Mammoth is based on the Juggernaut 2, but it's a very different experience building it. I have built almost all Tamiya RC-models, but very few have been so much fun to build as the Mammoth. The model is not authentic or even realistic in all aspects, but as usual for Tamiya, it's very well made, and the model feels much larger and more impressive than the "Jug" or even the TXT-1, especially during assembly.

Assembly is very straightforward, and I simply can't think of a single thing to improve in the assembly process itself. However, I find "bright" screws and nuts inappropriate for a dump truck, so I replaced all visible screws and nuts with black (but otherwise identical) screws and nuts from Tamiya where available, and the rest from Kyosho. It's a small detail, but it gives the Mammoth a more serious look, and is absolutely worth it.

Being a scale model, I think the Mammoth deserves lights, and Tamiya obviously agrees as they have provided for 7 (yes SEVEN!) front lights and 4 rear lights. I used the (53370) Tamiya Monster Truck Light Set and the (53114) R/C Brake Light Set, but replaced the ridiculous greenish LEDs with white LEDs, and if you're on a tight budget, you can actually achieve almost the same results by buying 7 white 5mm LEDs and 4 red 5mm LEDs and the necessary resistors.

Ball bearings is always my first (and mandatory) priority when assembling a model, so I replaced all bushings (including those in the tipping mechanism) with ball bearings. This is especially important if you intend to run your Mammoth with the maximal load of 4kg (or more!), as this makes for a total weight higher than any other Tamiya model (except for a truck with trailer, but they have 4-5 axles to distribute the weight), and with this weight the reduction in friction and wear is evident.

Being based on the Juggernaut 2 (and not the Juggernaut "1"), it doesn't have the drivetrain problems that made the Juggernaut's career so short.

Is there anything I don't like about the Mammoth? Not much. When I mounted the extra included bumper I was amazed to realize that its attachment lock the front suspension. I couldn't in my wildest dreams believe it was meant to be like that, and started to flip the pages of the instruction manual to find out what I had done wrong. Nothing! It's difficult to describe, but I will try. The front part of the "body" (all yellow parts other than the bed) is first attached with two 3x6mm screws. The suspension is still functioning. If you then attach the extra black bumper (two screws too) the front axle and the chassis are BOTH attached rigid to the body, and the mentioned 3x6mm bear the whole load on the front axle, and the suspension is blocked. The plastic is rather thin around the screws, so if you drive on a rough undulating surface (especially with load in the bed) the body will be severly stressed around the mounting holes. I'm still trying to figure out a good solution which will allow for both suspension movement and still have the bumper mounted. An alternative solution is to drive the model without the bumper, which I personally would never do, as parts availability probably isn't too good for the body parts, and if you should get them, they will surely be expensive. So the only remaining solution is to block the movement of the front suspension with spacers inside the dampers. The tires are rather soft and the need for a suspension a minor concern.

Som of the hop-up parts for the Juggernaut will also fit the Mammoth, but I can't think of a single rational reason for mounting any of them except for the light set. Gold/orange anodised aluminum dampers (53369) and suspension arms (53383) just don't look right, and the stock friction dampers and plastic suspension arms can easily cope with their rather light duty in the Mammoth. If I can get the dampers and suspension arm (and th frame) anodised black or maybe dark grey, I will mount them, as I have them lying around after abandoning my Juggernaut project. Talking about changing colours, Tamiya should have molded the wheels in yellow plastic too, rather than chroming them. If I ever paint the body, I will dechrome (with window washing liquid) and paint the wheels as well. Keeping the model unpainted is sensible if you want to run it though, as any paint would be scraped from the bed in minutes.

I've been thinking of locking the rear differential to improve traction. Doing this will also make the model look more realistic when driving as spinning wheels don't really look authentic! As the wheelbase is relatively short and the track narrow (proportion wise) I don't think the steering will suffer noticeably. If the drivetrain can stand it is another question. Talking about traction, though the Mammoth is based on a monster truck and has 4WD, it's NOT an off-roader. Ground clearance is much too low for that, and the tires have a relatively shallow and realistic pattern. Also, the center of gravity is quite high. Just like the Juggernaut, the suspension travel is also very short, and like mentioned above, if built according to the instructions, the front suspension is actually locked up.

The Mammoth has just one motor, whereas the Juggernaut and Juggernaut 2 have two. The Mammoth has the same gearbox as the Juggernaut 2, but where the motors are mounted in the "Jug", the Mammoth has an adapter with an extra spur gear. With the additional spur gear arrangement, torque is immensely improved and speed lowered, so one motor supplies more than enough power. For those of you who think of mounting two motors anyway, I have bad news. The adapter doesn't provide for it, and even without the adapter it's not possible without major surgery.

The tipping mechanism is very sturdy and well made, and actually has a lot in commom with the (56505) Motorized Support Legs for the tractor truck series. It's powerful to unload much more than the maximum 4kg from the bed without even slowing down the motor, and with (optional) ball bearings, should last forever.

As the Mammoth includes a servo operated "half ESC" mechatronic speed control, just a 2-channel radio is needed for steering, throttle and tipping mechanism.

What about realism? Basing the Mammoth on "Jug" parts, Tamiya had to make a compromise on realism, but I think the model still looks great. A friend of mine pointed out that single wheels on the rear axle isn't very realistic, but there is no way Tamiya could have managed to put double wheels on the Mammoth without developing many new parts or making the model unrealistically wide.

OK, so the Mammoth is not perfect, but should you want one? Definately yes! If you like me love Tamiya models (otherwise you wouldn't be reading this! ), this is a "must have". It's slow (and should be), it handles rather badly both on- and off-road (I've driven a friend's Mammoth), and it's not really much fun driving with it, whatever load you choose to carry. However, it's such a great pleasure to build it, and the resulting model is very impressive with its size and all the exposed metal and mechanicals.

Some testers in different RC-magazines have criticized the Mammoth for being 1/20 scale, have suggested 1/14 or even 1/10 to be a better choice. I agree that would be very nice, but it's still a ridiculous suggestion. If Tamiya had chosen 1/14 or 1/10 scale, Tamiya would have had to construct an all new chassis for it (increasing price) and in 1/10 scale, the model would have had 8 times! more volume, which would increase weight (not 8 times surely, maybe "just" 4-6 times!) and use of material beyond sense. Also it would require a large steering servo and battery. You don't have to be a rocket scientist to figure out this would be a very costly model, but obviously most testers in RC-magazines haven't thought of it. Also, the box is huge as it is, and the price is reasonable, but not cheap, but in 1/10 scale.....need I say more?

Accordingly, 1/20 scale is OK. Now I just need a 1/20 scale RC-car or -truck to go with it. I could of course make an RC-car of any of Tamiya's motorized sportscar or racecar 1/20 scale plastic kits, but it wouldn't look right. Nichimo made som motorized 1/20 scale Jeeps back in the eighties. Any of these would be perfect to demonstrate how big the Mammoth really is!