RCScrapyard ► Iconic Vintage Radio Controlled (RC) Model Car Archive ► Xpress MRR2 Pro. (Mini Road Runner II)
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1/10 Scale Electric Rally/Touring Car:

Xpress Mini Road Runner II Pro - MRR2-PRO (Radio Controlled Model)


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History, Info (and How To Set-up Tips) for the Xpress MRR2 Pro:


  Introduced by Xpress circa 2007, the Xpress Mini Road Runner II Pro Touring Car chassis - # MRR2-PRO - was the top of the range version.

  The model was belt driven, on a carbon double deck chassis, with ball differentials, coil spring over oil filled dampers, universal joint drive-shafts, sway-bars and ball bearings.

Xpress MRR2 Pro
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  To race the Xpress MRR2 Pro, 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 MRR2 Pro 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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Items For Sale:






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★ Xpress Mini Road Runner II Pro - MRR2-PRO ★
Xpress Mini Road Runner II Pro - MRR2-PRO

★ Xpress Mini Road Runner II Pro - MRR2-PRO Chassis ★
Xpress Mini Road Runner II Pro - MRR2-PRO Chassis

★ Xpress Mini Road Runner II Pro - MRR2-PRO Chassis ★
Xpress Mini Road Runner II Pro - MRR2-PRO Chassis

★ Xpress Mini Road Runner II Pro - MRR2-PRO Chassis ★
Xpress Mini Road Runner II Pro - MRR2-PRO Chassis

★ Xpress Mini Road Runner II Pro - MRR2-PRO Chassis ★
Xpress Mini Road Runner II Pro - MRR2-PRO Chassis


Buying a Used Xpress MRR2
Touring Car (and What to look for)


   Buying a used Xpress MRR2 Electric 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 Xpress 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 Xpress 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 Xpress 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 Xpress MRR2 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 MRR2 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 MRR2 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 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 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 MRR2 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 Xpress MRR2 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 Xpress 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 MRR2 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

Slipper Clutch and Hydra-Drive

   More often installed on off road RC Models, the Slipper Clutch has been around since the late 1990s. Basically the idea is to prevent wheel spin and increase traction under acceleration, to improve the cars stability from a standing start, when landing from jumps or on corner exits. It also protects the spur gear and drivetrain, to some degree, when using a high torque motor.

   The design is quite simple, employing two independent metal plates, one generally fixed to the spur gear and the other to the drive mechanism, clamping onto a fibre or rubber ring or pad. Adjustment is commonly achieved by slackening or tightening a spring loaded nut on the end of the spur gear mount.

   Setting up the slipper clutch can take some time and is a matter of individual preference, but normally the way to do this is from a standing start, jamming on the throttle and simply getting the feel of the car for that particular surface, being grass, gravel or dust. Personally I adjust it to give me around a metre and a half slip, before it achieves full drive. Wear on the slipper clutch is natural and often has to be readjusted after each race.

   The Hydra-Drive, or Fluid Coupling design has actually been around since the 1950s, but only came to RC a couple of years after the introduction of the slipper clutch. In principle, the Hydra-Drive is supposed to give similar results to the slipper clutch but need less continuous adjustment. In practice, for me anyway, it was not easy to live with.

   Hydra-Drives employ two independent impellers, immersed in silicone oil and enclosed in a sealed housing. Again, like the slipper clutch, one impeller is fixed to the spur gear, the other the drive. As power is applied, the spur gear will spin its impeller, until through the oil, drive is picked up by the drive impellor. The only real way to adjust the drive was to change the oil viscosity, or in some, the gap between the impellers could be adjusted by shims. All this took time and as far as I am aware, the Hydra-Drive is no longer used in RC.

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







Hints and Tips

Caster

   Caster is basically the angle the steering kingpins or steering pivot points, leans back in relation to the horizontal when viewed from the side of the chassis.

   To test the effectiveness of your cars caster, place your model on a flat surface, point the front wheels straight ahead and push the chassis over to one side to simulate body roll when cornering. You will notice that as the car leans over, all four wheels also lean over in the same direction. Tires provide the most grip when the wheels are perfectly vertical and the full width of each tire is flat on the ground. Body roll pushes the wheels past the vertical and reduces the amount of tire contact. Now, if you turn the front wheels as if cornering and again push the chassis over, you will see that in this position, the front wheels are now more vertical, giving you better ground contact and therefore improved grip.

   Another effect of caster can be seen by disconnecting your steering servo and pushing your car along the floor. Because of caster and the kingpins leaning back, your car will naturally roll straight ahead.

   Obviously, the more body roll your car induces, the more positive caster you need to counter it. Buggys, Trucks and Truggys, because of their high ride height and long dampers have more body roll and therefore require more positive caster than on road cars, with their low ride height and shorter dampers.

   If you consider a corner as having three parts: An entrance, middle and an exit. Caster influences each of them.

   With a high degree of positive caster, as you enter the corner and body roll is at its greatest, steering is better. In the middle section, as body roll reduces, steering is less effective and some under-steer is induced, that will continue as you accelerate on corner exit.

   With a low amount of caster, steering response is improved in the middle section of low speed turns and will be more likely to over-steer on corner exit because of increased front end grip from the tires.

   Too little caster can result in difficult handling on corners and poor stability on the straights.

   Most modern RC model kits come with a standard caster setting that has been set for the best handling by the manufacturers. If you are new to the sport I would recommend you stick with this setting until you get a little more experience.

   Methods to adjust caster can vary from model to model. Sometimes it is as simple as moving the position of a plastic washer from one side of the top wishbone pivot bar to the other, or simply using a small clip. Models from some manufacturers often have specific caster blocks to change the angle and must be purchased separately.

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










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