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1/12 Scale Electric Monster Truck:

Marui Big Bear Datsun (Radio Controlled Model)


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History, Info (and How To Set-up Tips) for the Marui Big Bear Datsun:


  Introduced by Tokyo Marui circa 1984, the 2WD Big Bear Datsun Monster Truck, was their 4th RC model and came with an M480RS motor, mechanical speed controller and detailed ABS plastic bodyshell.

  Based on a molded plastic tub type chassis, the model employs a gear type differential, with undamped coil spring suspension, fixed half-shafts and bushings, ring type bearings.

  The same chassis design was also used by Marui for the Super Wheelie Toyota Land Cruiser, Super Wheelie CJ-7 Golden Eagle, re-released CJ-7 Golden Eagle, re-released Toyota Land Cruiser and Mitsubishi Jeep.

Marui Big Bear Datsun - 1:12 Electric Monster Truck
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  To race the Marui Big Bear Datsun, you need to tweak and adjust all you can to give your car improved handling, stability and grip to ease around the curves and keep you on the track. One little setting change can transform your car into a world beater. Just follow our chart to attain the most favourable Set-up to suit your particular needs on any track.

  Learn what to look for when you search for the right Electric Motor for your Big Bear Datsun and achieve the best Gearing, for the best performance and put you on the winners rostrum.

  See how the highest level racers optimise and halve the friction of their Bearings with some easy to implement tips. Discover what you can do to avert Radio interference, and the optimum conditions to Charge your Batteries, to help keep them in good condition and give you excellent performance.









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★ Marui Big Bear Datsun ★
Marui Big Bear Datsun

★ Marui Big Bear Datsun Chassis ★
Marui Big Bear Datsun Chassis


Buying a Used Marui Big Bear
Monster Truck (and What to look for)


   Buying a used Marui Big Bear Electric Monster Truck, or any used RC Model, has a number of advantages. It is generally cheaper than new, ready built and may come with a variety of expensive hop-ups already installed. Cheap, pre-loved bargains are always becoming available. However, depending on the age of your purchase, it may need a little tender loving care before you can take it out on the back yard.

   The one thing you will always need is an instruction manual. If not supplied with your purchase, they can often be downloaded from the Competitionx website, or purchased separately on eBay. With an instruction manual, any problems with your model Monster Truck you may discover can easily be fixed.

Dampers
   When you receive your used Marui Monster Truck, make a general visual inspection of the chassis, front and rear wishbones, suspension shock towers etc, for any broken parts that may need to be replaced. Then, take a screwdriver and box spanner and check each self tapping screw and nut for security, taking care not to over tighten.

   Next, for those Marui models with oil filled shock absorbers, remove them from the chassis and dismantle the coil springs. The damper shafts should push in and pull out with a smooth action. If you feel a jolt as you change direction, this means the oil has leaked out and must be topped up. At the same time, change the O-Ring seals to prevent more leakage. Also check the damper shafts for damage. If they are scratched, change them as soon as possible.

   If the body shell of your Marui Big Bear is broken, ripped or damaged in any way, this can be easily repaired with rubber solution glue. Also, for added protection and if available for your Big Bear model, fit an under guard to stop dirt and gravel entering the chassis.

Titanium Turnbuckles
   Examine the drive shafts for wear and replace as required. If possible, change them for titanium. The steel shafts wear and bend too easily.

   If you intend to race your Big Bear Monster Truck model at a competitive level, I would also recommend you obtain and fit titanium pivot shafts, turnbuckles, tie rods and steering rods.

   The gearbox of your used Monster Truck should be opened up to check for gear wear and lubrication. A thin coat of grease is often used on internal gears and although this is fine for basic running around on the back yard, if you intend to race your Monster Truck at a higher level, this should be removed and replaced with racing oil (ZX1 or Teflon Oil). Of course, this should be reapplied after each race meeting.

Spur Gears
   Gears are a weakness on all Monster Truck RC models. Head on collisions can easily damage the gear teeth on nylon and plastic spur gears. Heavy impacts can also loosen the nuts or self tapping screws that hold the Electric Motor in Position, allowing the pinion gear to pull out of mesh slightly and rip the tops off the teeth on your spur gear. To minimise this possibility, fit bolts with locking nuts to the Electric Motor mount and remember to check them for security after every two or three runs.

   Ball joints always cause problems. For top level Electric Monster Truck racing, the plastic ball connectors should be checked and if deemed necessary changed after every meeting. A simple thing like a loose fitting connector popping off could easily end your race, so better safe than sorry.

Servo Gears
   The Big Bear steering servo is also prone to damage. In high speed crash situations, the fragile gear teeth of the servo can be broken off, rendering your expensive servo useless, so be sure to obtain a good quality "Servo Saver". Check out my Servo Information article.

   If body roll on your Marui Big Bear is a problem, handling can be improved with the use of stabilizers, anti roll or sway bars, stiffer tuning springs and, or, thicker silicone oil in the dampers.

Ball Bearings
   If your used Marui Monster Truck comes with plastic and sintered brass bushings (ring type bearings), check the shafts that run in them for wear. Dust and grit can get into these bearings and abrade the shafts. Therefore, you should replace them all with shielded ball bearings. If the model has been run with ring type bearings, you may have to change all the axles and driveshafts. For more information, take a look at my article, How to get the best from your Bearings.

   Finally, good luck with your Big Bear model and good racing.


For More on how to Setup your Monster Truck, check out my Hints and Tips page.


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Manufacturers and Brands Catalogued and Listed by RC-Scrapyard.


   At present, the RC Model Manufacturers, Brands and Distributors covered by us are: ABC Hobby, Academy, Acme Racing, Agama Racing, Amewi, Ansmann Racing, ARRMA, Team Associated, Atomic RC, Axial, AYK, Bolink, BSD Racing, Capricorn, Carisma, Carson, Caster Racing, Cen, Corally, Custom Works, Durango, Duratrax, ECX - Electrix, Exceed RC, FG Modellsport, FS-Racing, FTX, Fujimi, Gmade, GS-Racing, Harm, HBX, Helion, Heng Long, Himoto Racing, Hirobo, Hitari, Hobao, Hong-Nor, Hot Bodies, HPI, HSP, Intech, Integy, Jamara, JQ Products, Kawada, Kyosho, Losi, LRP, Maisto, Mardave, Marui, Maverick, MCD Racing, Megatech, Mugen, New Bright, Nichimo, Nikko, Nkok, Ofna, Pro-Pulse, Protech, PTI, RC4WD, Redcat Racing, RJ-Speed, Robitronic, Schumacher, Seben, Serpent, Smartech, Sportwerks, Step-Up, Tamiya, Team-C Racing, Team Magic, Thunder Tiger, Tomy, Top Racing, Traxxas, Trinity, Tyco, Vaterra RC, Venom, VRX Racing, WLToys, X-Factory, Xmods, Xpress, Xray, XTM, Yankee RC, Yokomo, ZD Racing and Zipzaps.

   This is an ongoing project, with new and "lost in time" RC Model Brands being added as they are found and although most of those listed above have been covered in relative detail, some are still being researched and will be completed in the near future.


















Hints and Tips

Roll Center

   One of the least understood settings on RC model cars is concept of roll center. The simple definition of roll center is a point in space that the chassis rolls from side to side as the car maneuvers around a corner.

   To calculate roll center you have to consider things like the height of the axles, the inside and outside camber link positioning, the length of the suspension arms and the location of their inside pivot point. Sounds complicated doesn't it and in truth it is.

   On all RC model cars, most of the cars weight is above the chassis and the center of gravity of the car is not only from front to rear, but also from top to bottom. This point is called the "true" center of gravity and is the point around which the weight of the car will want to roll from side to side, but it is the roll center of the chassis that the chassis will actually roll around, not the center of gravity.

   Once you have determined the positions of roll center and center of gravity, you can calculate the "roll moment". It is this that determines how easily the chassis will roll from side to side.

   But what does all this mean? I hear you ask. Well, it gives you some insight to what changing the position of your camber links can do to the way your car handles.

   Lowering the outside camber links, lowers the roll center, so conversely, raising the outside link position raises the roll center.

   Lowering the inside camber link position raises roll center and raising the inside camber link position, lowers the roll center.

   Any of these adjustments will affect the "roll moment" and therefore you have some control of body roll.

   The length of the camber link bars affects the speed of roll center change as the car driver around corners. Longer links increase the rate of change. Shorter links decreases the rate of change.

   Adjustments to the roll center will change the way the car reacts in a number of ways.

   Lowering the front roll center gives more steering under acceleration, but the car is less responsive. Ideal for smooth high grip tracks, with long sweeping corners.

   Raising the front roll center provides less steering when accelerating out of the corner, but the car feels more responsive and is less prone to traction roll. Best for high grip twisty tracks.

   Lower rear roll center improves grip under acceleration, but reduced grip when breaking. Helpful to avoid traction roll as you enter the corner and tracks with low grip to increase traction.

   Higher rear roll center gives you less under acceleration, but the car is more responsive. Works for high grip twisty tracks to reduce traction roll.

For More Setup Information check out my Hints and Tips page.







Hints and Tips

Sway Bars

   On most forms of RC model cars, Sway Bars, also referred to as Stabilizers, Torsion Bars, or more commonly in some parts as Anti Roll Bars, are often nothing more than a short length of spring steel, clamped to the chassis or sometimes the gearbox of the car, extending out to the lower wishbones direct or connected to the wishbones using short adjustable or fixed length links and ball joints, depending on their position.

   The principal behind the Sway Bar is simple. As the car enters a corner, weight is transferred to the outside wheels, the chassis rolls due to inertia and the suspension dips and grip on the inside wheels is reduced. In an effort to counter this dipping effect and transfer some grip back to the inside wheels to improve traction as you exit the corner, the sway bars transfer the dip of the outside, to pull down the inside wishbones, improving grip on the outside wheels and improving overall stability.

   Sounds complicated I know, but for some tracks sway bars can be a useful tool when you have exhausted all other options to correct your handling problems.

   Tuning your Sway Bars is quite easy. Some manufacturers do offer colour coded tuning sets with varying thicknesses of spring steel wire, but the best way is to change the position the bar is attached to the wishbone, or on some variations you have the option of positioning the link on the Sway Bar itself. By simply moving a small collet clamped along the short length of the bar. Closer to the central pivot point reduces the leverage of the bar and effectively increasing its resistance, further away from the pivot point reducing resistance. More fine tuning can be achieved by adjusting the length of the turnbuckle link (if available) to pre load the bar.

   Personally, before I ever installed any sway bars I would always try changing damper tuning springs and oil viscosity settings, especially if the track was uneven and bumpy, in which case the effectiveness of the bars was minimal if at all.

   For those more into Drifting, Sway Bars can be an easy way to fine tune your car. A single turn on the turnbuckle links can be a way to simply increase or decrease wheel traction that minute amount you need to get the perfect balance.

   For more on how to use Sway Bars check out our Set-up tips page linked below.

For More Setup Information check out my Hints and Tips page.










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