1/10 Scale Electric Rally/Touring Car:

HPI Sprint 2 Flux - BMW M3 - # 106168 (Radio Controlled Model Review)

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History and Info:

Introduced by HPI (Hobby Products International) in 2013, the BMW M3 - # 106168 - based on the Sprint 2 Touring Car chassis, came factory assembled with a pre-painted lexan polycarbonate Bodyshell, a Flux Vektor 5900kv Brushless Motor (later changed to a Flux 4000KV), Flux Vapor Waterproof ESC (later changed to a EMH-80A) 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 - # 106168

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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.

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Radio Controlled Model Accessories:

★ HPI Sprint 2 Flux - BMW M3 - # 106168 Chassis ★

★ HPI Sprint 2 Flux - BMW M3 - # 106168 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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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:

Hints, Tips and Information

Bumpsteer

   In plain language, Bumpsteer is exactly what it sounds like. If your car goes over a bump, it will affect the toe-in setting and can on some tracks make handling of the car in a straight line difficult.

   To check if your car might have any problems with bumpsteer, have it in race mode, with the motor and battery etc in position. Place the car on a flat surface and push down your car at the front. Looking down from above, keep a close eye on the wheels and watch for any angular movement to the side. If there is then you have bumpsteer.

   For off road cars, because of them having longer dampers in comparison to on road, a small amount of toe out is considered by many as acceptable in the lower position and can sometimes be used as a tuning option because of its aggressive effect on turning ability when entering corners. On road cars, because of the shorter damper movement and the greater need for precise steering and stability in a straight line, generally have less of a problem. However if bumpsteer is detected, drivers generally try to eliminate this as much as possible.

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Hints, Tips and Information

The Importance of Suspension Droop

   When you pick up your RC model car, the suspension arms naturally drop, this is termed as Droop and should be equal from side to side, but can vary from front to rear.

   Setting the amount of droop, or suspension movement, can dramatically change the handling of your car by limiting the transfer of weight from one side of the car to the other.

   Basically, increasing the droop at the rear of the car can improve cornering grip at the front and increasing droop at the front of the car, improve cornering grip at the rear. The amount of effectiveness of this setting does in general depend on a number of other setting factors your car may have to suit your personal driving style.

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