1/10 Scale Electric Rally/Touring Car:

HPI Sprint 2 Flux - BMW M3 GTS - # 112862 (Radio Controlled Model Review)

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History and Info:

Introduced by HPI (Hobby Products International) in 2014, the BMW M3 GTS - # 112862 - based on the Sprint 2 chassis, came factory assembled with a pre-painted lexan polycarbonate Bodyshell, a Flux VEKTOR Brushless 5900Kv Motor, Waterproof Flux Vapour ESC and 2.4Ghz radio system. A number of other bodyshell options were available (Check out our HPI Archive).

The 4WD HPI Racing model is belt driven, on a double deck molded nylon chassis, with orange anodised alloy parts, gear type differentials, coil spring over oil filled dampers, dogbone drive-shafts and ball bearings.

HPI Sprint 2 Flux - BMW M3 GTS - # 112862

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To get the best from the HPI Sprint 2 Flux, it needs to be fine tuned, to provide precise steering response and improve grip when cornering, so you don't slide off the track. Small changes can make huge advancements and our easy to understand guide will help you to the optimum Set-up for your individual driving style.

Sprint 2 Flux
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Sprint 2
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Sprint 2
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★ HPI Sprint 2 Flux - BMW M3 GTS - # 112862 Chassis ★

★ HPI Sprint 2 Flux - BMW M3 GTS - # 112862 Chassis ★

Buying a Used HPI Sprint 2 Flux
Touring Car (and What to look for)

There are essentially three reasons you might want to buy a used HPI Sprint 2 Flux Electric Touring Car; you may be a collector, looking to restore and display it; restore and sell for a profit; or simply restore and race an iconic vintage model. Personally, I used to get a buzz out of restoring an old clapped-out model, installing modern day electrics and maybe a few hop-ups, then showing the gang at our local club, just how competitive those old models could still be.

Cheap, pre-loved bargain models, parts and spares are always coming up for sale, but once you have made your purchase, the one thing you will always need, is an instruction manual. If not supplied with your purchase, they can often be downloaded from the HPI website, or purchased separately on eBay. With an instruction manual, any problems with your model Touring Car you may discover, can easily be fixed.

Make a General Visual Inspection

Dampers
When you receive your used HPI 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 HPI 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.

Check the Body-Shell

If the body shell of your HPI Sprint 2 Flux 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 Sprint 2 Flux model, fit an under guard to stop dirt and gravel entering the chassis.

Drive Shafts and Turnbuckles

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 Sprint 2 Flux Touring Car model at a competitive level, I would also recommend you obtain and fit titanium pivot shafts, turnbuckles, tie rods and steering rods.

Examine the Drive System

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.

Pinions and 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.

Don't Neglect the Ball-Joints

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.

Steering Servo and Servo-Saver

Servo Gears
The Sprint 2 Flux 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.

Stabilizers

If body roll on your HPI Sprint 2 Flux 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.

Don't Forget those Bearings

If your used HPI 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 Sprint 2 Flux 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 Models and 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.

RC Information and Advice:

Information and Advice

Electronic Speed Controllers

History

   ESC were originally developed to be used in conjunction with brushed 27T stock and modified motors in the late 1970s, early 1980s. Compared to modern day Controllers, they were Bulky and heavy, constructed using basic resistors, rheostats, capacitors and transistors, crammed together on a simple circuit board, to provide stepped but smooth acceleration when compared to the old mechanical, servo operated sweeper Speed Controllers. An Electronic Switch to change the direction of current flow was used on some of these early ESC to give reverse operation. Although they were a vast improvement on the old mechanical speedos of the time, they were expensive, jerky to control, and prone to burn out if not carefully looked after.

   As new technology became available, improvements were slowly made, and with the introduction of the new FET (Field Effect Transistors) and some basic mass produced silicon chips, ESC were made smaller and their reliability gradually improved.

   By the mid 1990s, "regenerative breaking" was developed. This meant that energy that would have been lost slowing down the car by effectively turning the motor into a generator, was harvested and put back into the battery. This of course was long before F1 had KERS (Kinetic Energy Recovery System) and adjustable anti lock breaking was introduced.

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Hints, Tips and Information

Tire Compounds

Way back in the early 1990s when I first got into RC, most of the off-road models available came with chunky hard compound block tires that gave little or no grip on grass or dirt tracks. On-road didn't have this problem as they were still using sponge tires that with a coating of wintergreen based tire additive before each race to improve grip. There was even one guy who swore, before every race, he dipped his wheels in a glass of light ale.

Then things started to change. By the mid 1990s tire manufacturers such as Losi and Schumacher began developing smaller pin tires, in softer compounds. These mini pin versions were a revelation for grass racers, but were only a small improvement on dust tracks.

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