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1/10 Scale Nitro Rally/Touring Car:

Hobao GPX4 (Radio Controlled Model Review)


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History, Info (and How To Set-up Tips) for the Hyper GPX4:


  Manufactured by Hobao in 2005, the 4WD Hyper GPX4 Touring Car, is belt driven, on an alloy plate chassis, with gear type differentials, coil spring over oil filled dampers, anti roll bars, CVA universal joint drive-shafts and a full set of ball bearings.

  The model was marketed in the USA by Ofna Racing.

Hobao Hyper-GPX4
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  To race the Hobao Hyper GPX4, it must be fine tuned to improve handling, provide responsive steering and give you the grip to cruise around corners at high speed, without slipping off the track. Small adjustments can make a Big difference and our step by step procedure, will guide you to the best Set-up for your individual driving style.

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★ Hobao Hyper GPX4 ★
Hobao Hyper GPX4

★ Hobao Hyper GPX4 Chassis ★
Hobao Hyper GPX4 Chassis

★ Hobao Hyper GPX4 Chassis ★
Hobao Hyper GPX4 Chassis


Buying a Used Hobao Hyper GPX4
Touring Car (and What to look for)


   Buying a used Hobao Hyper GPX4 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 Hobao 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 Hobao 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 Hobao 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 Hobao Hyper GPX4 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 Hyper GPX4 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 Hyper GPX4 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 Hyper GPX4 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 Hobao Hyper GPX4 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 Hobao 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 Hyper GPX4 model and good racing.


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Or, check out our RC Model Car Setup Guide


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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.





















Hobao GPX4 Chassis
Hobao GPX4 Chassis


Hints and Tips

Ackerman

   So What is Ackerman?

   If you place your car on a table facing away from you and turn the steering to full lock to the left, you will notice the angle the left hand wheel has turned is more than that of the right hand wheel. That is the Ackerman effect.

   Moving your car to the edge of the table, with the wheels still on full lock, push it round a complete circle. What you will notice, is the diameter of the circle made by the inside wheel, is smaller than that of the outside wheel. This is a good thing.

   Consider what would happen if both wheels turned to the same angle. In this example, the inside wheel would have a tendency to drag sideways, making the car unstable and difficult to drive.

   The standard kit setting on the majority of RC Model cars, are generally pretty good for beginners, but when your experience increases, you will find out just what tuning your Ackerman can do for your driving style and why it can be helpful when setting up your car for any particular track.

   Some of the cheaper RC Models have fixed position steering links. Others have various methods to change Ackerman settings, like changing shims under the ball connector etc. These days, most modern cars allow you to adjust your Ackerman by lengthening or shortening the links by simply removing two screws and repositioning the links in relation to the front suspension arms.

   Lengthening the links, by adjusting the pivot points of the steering arms back towards the centre line of the rear axle, will give you Less Ackerman, providing you with more aggressive steering as you enter a corner. Useful on slippery tracks, to counter when the car tends to slide to the outside of the corner as you first turn into it.

   Shortening the links, by adjusting the pivot points of the steering arms more forward of the centre line of the rear axle, will give you More Ackerman, making cornering less aggressive, more predictable and improving car stability, better for high grip tracks, with smooth sweeping corners.

   How to implement these adjustments varies from model to model so you will have to refer to your manual for full instructions.

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







Hints and Tips

Toe Angle

   When you first build your RC model car, you will no doubt have made all the settings advised in the manufacturers' manual and will take it out on the back yard not thinking of things like camber, caster or toe-in I know I did. It's only when you get competitive that you start learning about these things and just what a big difference they can make to the handling of your car. One of the more effective of these adjustments is Toe-in.

   The term, toe-in, toe-out, or toe-angle, refers to the alignment of the front or rear wheels, when viewed from above and is easily adjusted via the track rods or turnbuckles that link to the steering mechanism or directly to the steering servo horn.

   Front toe-in reduces steering when entering a corner, but improves steering response on corner exit under acceleration. On the straights, toe-in will also improve the cars stability while accelerating.

   Front toe-out will improve steering on corner entry, but makes the car unstable under acceleration on the straights and on bumpy tracks. The usual recommendation is to have up to 1 degree of either toe-in or toe out.

   Rear toe-in is generally found as the standard setting on most on-road and off-road RC models.

   More rear toe-in provides the car with more power under-steer, as well as improved stability and rear end traction. This setting is recommended for low grip tracks.

   Less rear toe-in slightly reduces steering on corner entry, but improved steering under acceleration.

   To measure toe-angle, I used to use my trusty vernier callipers to measure the width at the front of the wheels and the rear of the wheels and using this information along with the diameter of the wheels simply calculate the angle. Or, you could alternatively use this data to draw a triangle on a sheet of paper and measure the angle with your trusty school protractor.

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










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