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1/10 Scale Nitro Rally/Touring Car:

Hobao Hyper GPX4 Pro (Radio Controlled Model Review)


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


  Manufactured by Hobao in 2005, the 4WD Hyper GPX4 Pro 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 GPX4 Pro - 1:10 Nitro On Road Car
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  To race the Hobao GPX4 Pro, 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.

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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 GPX4 Pro
Touring Car (and What to look for)


   Buying a used Hobao GPX4 Pro 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 GPX4 Pro 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 GPX4 Pro 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 GPX4 Pro 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 GPX4 Pro 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 GPX4 Pro 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 GPX4 Pro 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

Bearing Seals

   If you were to ask anyone with a modicum of experience in RC, they will tell you that the best modification you can make to a basic RC model, is to add a set of ball bearings.

   Quite a few of the entrance level models at the time this article was written, come with plastic and sintered brass bushings (ring type bearings). If these bearings are installed in the model and coated with grease as advised in the car manual, dust and grit can be caught in that grease and be dragged into the bearing where it can abrade the shaft that spins in it and it won't be long before it becomes a very sloppy fit, causing all kinds of problems.

   But what should you look for when buying bearings? There are a number of types of seal used on ball bearings and there is much debate concerning which is the best for RC.

   Rubber and Cork bearing shields are two of the more common types available, but although they are very effective when it comes to preventing dust and grit entering the bearing, they also create more drag in the bearing due them rubbing against the bearing to create friction. For this reason, if I wanted to race my model at any level and that model was fitted out with rubber or cork shielded bearings, I would change them ASAP.

   Steel and Teflon bearing shields may not be as effective as the rubber shielded versions, but they don't rub on the bearing, so little or no friction is created. The problem with this kind of bearing of course is that they need much more maintenance and are often more expensive.

   Basic shop bought bearings generally come packed with grease for their lubrication. However, if you want to have your bearings spin freely; grease is not the best thing to use. So, before you install your new bearings in your car, the first thing you need to do is clean out the grease with something like isopropanol and replace with thin oil.

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







Hints and Tips

Weight

   If you ever step up and enter a regional, national or international event in RC, you will find one specific rule concerning the weight of your car.

   At the time this article was written, the Minimum weight restrictions for 1:10 electric Touring Cars at different events, was between 1350g and 1500g. This includes your Motor, ESC, Receiver, Battery, Body Shell and the transponder.

   Out of the box you will find the majority of 1:10 Touring Cars, with everything onboard, are way over this Minimum weight and unless you are good enough to attract sponsors, getting your car down to anything approaching that minimum weight will be very expensive.

   There are things you can buy like micro ESC and Receivers. But Batteries and Motors are what they are and you have to work around them.

   To reduce the weight of your chassis, there are a number of things you can do. If the car you have is generally considered competitive enough, there are often carbon fibre main chassis, shock mounts and other alternative parts available, but they are expensive. And when the new version of your model comes out all the money you have spent is lost.

   The most cost effective weight reduction is the metal parts of your chassis. UJs, Drive and Pivot shafts and the like tend to vary from model to model, but turnbuckles can often be transferred and lengthened or shortened by using plastic ball connectors, so titanium is a consideration.

   Screw sets can also be transferred from car to car. Titanium screws and wheel nuts are always available, but there is a cheaper alternative Aluminium screws and nuts can reduce your cars weight cheaply, but be careful not to over-tighten them, aluminum is not as strong as titanium and can easily shear off if you are over zealous.

   Another weight reduction option is to drill holes along the base of the chassis. However, I do not recommend this. For one thing you are reducing the strength and making the chassis less rigid, but you are also raising the centre of gravity of your car, which can affect stability.

   If you do manage to get your car weight below the minimum allowed, this will give you an opportunity to add weight where you want it and lower the cars centre of gravity.

   One last tip: Knitting needles. When I first started in RC, money was tight and my dad came up with all kinds of ideas to reduce weight. He obtained a 3mm dye and found some of my mums old aluminum knitting needles that were just the right diameter. Having determined the length of the turnbuckles needed for my setup, he cut them to those lengths and threaded each end, so he could put plastic ball sockets on them. Adjusting them was a bit of a pain and they could be a bit fragile in crash situations, but they saved us lots of money over those early years.

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










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