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1/8 Scale Nitro Rally/Touring Car:

Mugen MRX-4 - H0070 (Radio Controlled Model)


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History, Info (and How To Set-up Tips) for the Mugen MRX-4:


  Introduced by Mugen Seiki circa 2005, the 4WD MRX-4 Racing Car - H0070 - was belt driven, on an alloy plate chassis, coil spring over oil filled dampers, rear dogbones, with front universal joint drive-shafts, 2-speed transmission and a full set of ball bearings.

Mugen MRX-4
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  To race the Mugen MRX-4, it needs to be tuned to perfection for better stability, precise steering and provide enough grip to keep you on the track when going around tight bends at high speed. Even the smallest adjustment can change the feel of a car and our simple to follow instructions will guide you to the best Set-up to get you to the front and keep you there.

  Our basic instructions will help you set-up and fine tune the Nitro Engine for your MRX-4.

  With a few simple tips, we will show you how to easily avert Radio interference, and Servo problems, by simply repositioning the receiver or using some of the latest developments. Learn how to combat friction and get more from your Mugen MRX-4 Bearings with a few common sense hints and tips.









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Items For Sale:






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★ Mugen MRX4 Chassis ★
Mugen MRX4 Chassis

★ Mugen MRX4 Chassis ★
Mugen MRX4 Chassis


Buying a Used Mugen MRX-4
Touring Car (and What to look for)


   Buying a used Mugen MRX-4 Nitro Touring Car, 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 road.

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

Dampers
   When you receive your used Mugen Touring Car, 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 Mugen 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 Mugen MRX-4 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 MRX-4 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 MRX-4 Touring Car model at a competitive level, I would also recommend you obtain and fit titanium pivot shafts, turnbuckles, tie rods and steering rods.

   Drive Belts need checking at regular intervals for wear, tension and damage. If deemed necessary, adjust the tensioning pulley until the belt can be depressed in the centre by no more than around 5mm. If the belt was slack, also examine the drive pulleys for wear. The teeth should provide a well seated fit for the belt teeth and not be rounded on the corners. If the belt teeth do not fit snugly, change the pulleys as soon as possible. For top level racing it may be prudent to replace all belts and pulleys after each race meeting.

Spur Gears
   Gears are a weakness on all Touring Car 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 Nitro Engine 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 Nitro Engine mount and remember to check them for security after every two or three runs.

   Ball joints always cause problems. For top level Nitro Touring Car 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 MRX-4 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 Mugen MRX-4 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 Mugen Touring Car 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 MRX-4 model and good racing.


For More on how to Setup your Touring Car, 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

Dampers

   Dampers, Shock Absorbers, Shocks call them what you will, they are one of the least understood, but most important tools you have for adjusting the handling characteristics of your RC model.

   In this article, I will endeavour to explain just what you can achieve by making simple tweaks to your shocks and how these tweaks can keep you ahead of your opposition on the track.

   In dictionary terms "Damper" is described as "A mechanical device to absorb the energy of sudden impulses." In plain language, they stop your car from bouncing all over the track.


So how do Dampers work?

   Basically what you have is a small amount of silicone oil contained in a sealed cylinder. Through the centre of that cylinder is a metal rod and on the end of that rod, a piston with a number of small holes in it. Pulling, or pushing the rod in and out of the cylinder, your will notice a certain amount of resistance as the oil is forced through the holes in the piston. To manipulate that resistance you have two options. You could use thicker or thinner oil, or change the size of the holes in the piston. So if you have thicker oil, or smaller holes, you have more resistance. Less viscous oil or larger holes, less resistance. This simple physical relationship, coupled with a good set of tuning springs, is all you need to set-up your car to beat the rest.

   Out on the race track, the main thing you want to avoid is your car bouncing around all over the place, sliding, or even rolling over when you negotiate a tight corner. To prevent this you need to make changes, but before you make those changes you need to consider what your problem is for that particular track. How your model reacts when cornering does it Under-steer? (Slide towards the outside of the corner) or Over-steer (Turns towards the inside of the corner). Does it react differently when you exit the corner to how it did when you entered it?

   Once you have decided what your problem is, go to our "Set-Up" page linked below and follow the step by step instructions. But remember to only make ONE change at a time. If the first suggestion isn't enough to cure the problem, add the second and so on, until you find that perfect setting. Good luck and good racing.

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







Hints and Tips

Wheel Balancing

   At the tender age of 17 I passed my driving test. Of course, the first thing I did was to dash over to my girlfriends house and take her out to a long straight stretch of road close by where the boy racers would often congregate. No one was around that day, so the road was relatively quiet. I slowly went through the gears and we reached 65 with no problems, but as we got closer to 70, my hands sensed a small vibration on the steering wheel. By the time we reached 75, the steering wheel and the whole car was vibrating hard. I remember my girlfriend screaming for me to "slow down," Which I did of course and tried to laugh it off.

   Back home I told my dad what had happened and he reminded me, that just the week before we had put on a new set of front tires and it must be the balance that is out. Sure enough, after the wheels were balanced, 85, 90, was not a problem, the car drove perfectly.

   So, when I got deeper into RC, that memory returned and now I balance all my wheels.

   These days, wheel balancing equipment for RC cars is available from most RC model shops, but back then I had to make my own using the rear end of an old Tamiya F1 car. Here's how I did it.

   With the tire and insert mounted and glued, the wheel was fitted onto my home made balancer and allowed to settle. I would then gently turn the wheel through 90 degrees and again allow it to settle. Obviously the heavy side of the wheel would drop to the bottom due to gravity. Once I was satisfied, I would then make a mark on the rim with a felt tip pen at the top of the wheel where it came to rest. Removing the wheel I would mix a small amount of plastic resin and press a tiny amount of this into a recess on the wheel on the side where I made the mark. The whole process was then repeated until I was totally satisfied.

   I was amazed just how out of balance some of those wheels were and how much a small thing like that can make a difference on the track.

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










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