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RCScrapyard Radio Controlled Models
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1/10 Scale Electric Rally/Touring Car:

Ofna OB4 - # 34901 / OB4 Pro - # 34903 (Radio Controlled Model Review)


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History, Info (and How To Set-up Tips) for the Ofna OB4:


  Manufactured by Hong-Nor and marketed by Ofna circa 1997, the 4WD OB4 - # 34901 - and OB4 Pro - # 34903 - came with a mid positioned motor, providing good balance for drift car racing.

  The model is belt driven on a double deck chassis, with ball differentials, coil spring over oil filled dampers, universal joint drive-shafts and came with a full set of ball bearings.

  The OB4 was renamed and re-released by Ofna in 2010, as the JL10e Drift.

Ofna OB4 Pro
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  To race the Ofna OB4, it requires a high level of tuning for improved stability when cornering, to keep it on the track and give you more grip under acceleration. Even the smallest change in your cars settings can make a Big difference. Our simple to follow instruction chart will show how to attain the best Set-up for your personal requirements.

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★ Ofna OB4 Chassis ★
Ofna OB4 Chassis

★ Ofna OB4 Chassis ★
Ofna OB4 Chassis

★ Ofna OB4 Pro Chassis ★
Ofna OB4 Pro Chassis


Buying a Used Ofna OB4
Touring Car (and What to look for)


   Buying a used Ofna OB4 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 Ofna 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 Ofna 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 Ofna 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 Ofna OB4 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 OB4 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 OB4 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 OB4 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 Ofna OB4 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 Ofna 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 OB4 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.


















Hints and Tips


Electric Motors for RC Models

Winds and Turns

Q/  What does 15x2 or 17x3 mean?
A/  The first number relates to the number of times the wires are wound round each of the 3 armature segments, the second number relates to the number of wires side by side. So a 15x2 would have 2 wires laid side by side and wrapped around each segment 15 times.

Q/  What is the difference in performance between a Low Turn motor (eg 11x1) and a High Turn motor (eg 27x1)?
A/  A Motor with Less Turns like an 11x1 means high current draw from the batteries which corresponds to less runtime, but More Power (Torque or Punch) Best for tracks with lots of corners and short straights where fast acceleration is needed. (use a small pinion)
Motors with More Turns like a 27x1 give you More runtime, but Less Power. So you get a smoother response and are therefore easier to drive. Better for less experienced drivers and Long straight, sweeping corner tracks. (with a large pinion) This is correct for Brushed, Modified and Stock Motors as well as Brushless Motors.

Q/  How do the number of winds effect a motor?
A/  A Motor with More Winds (number of wires eg 13x5) is less demanding on the battery and smoother in acceleration. Best for low grip, slippery tracks.
A Low Wind Motor (eg 11x1) is more punchy and can be difficult to handle. Best on high grip, hot weather Tarmac, or indoor carpet, high acceleration, low speed tracks.

Advance and Retard

Q/  What is Advance and Retard?
A/  On the Endbell of a Modified Motor (where the brushes fit) you will find two screws that hold the Endbell to the Can. If these screws are slackened off slightly the Endbell can then be twisted either Clockwise (Advance) or Anticlockwise (Retard). On Sensorless Brushless Motors this adjustment can generally be made in a similar way (although there are some Brushless Motors that have fixed timing for Spec level racing). Sensored Motors can be adjusted via the ESC.

Q/  What does "Advancing" the Endbell position do?
A/  Advancing the Endbell Reduces runtime, increases Punch (acceleration) and RPM to give a higher top speed.
On the down side, for Brushed Motors, the brushes wear faster and the increased current draw creates more arcing thus increased heat and Commutator (Comm) wear. Brushless Motors can lose some efficiency at the end of a race because of overheating due to increased current draw.

Q/  What does "Retarding" the Endbell position do?
A/  On both Brushed and Brushless Motors, Retarding the Endbell Increases runtime, decreases Punch (acceleration) and RPM to give a lower top speed and for Brushed Motors, brush wear and Commutator (Comm) wear is reduced.

Brushed Motor Basics

Q/  What is the effect of hard and soft Brushes?
A/  Basically, Hard brushes give a lower current draw, so consequently give longer run times and lower torque so less punch (acceleration)
Soft Brushes on the other hand increase current draw thus give higher torque and increased acceleration. Of course the down side of this is that Soft brushes wear much faster and must be changed more often. (I change mine when they get to around 5mm)

Q/  How does changing the brush spring change the motor?
A/  If you fit Stiffer Brush Springs your motor will have More power at low revs and also a lower top speed. I only ever fit stiff springs on bumpy tracks to reduce brush bounce.
Weaker springs reduce power but increase RPM so give less acceleration but a higher top speed. Good for long, sweeping, smooth tracks, where you can carry good speed through the corners.

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







Hints and Tips

Keeping Notes

   If all you will ever do is go racing at your local track every week, then this article is not for you. However, if you ever look towards travelling around to different tracks around the country, or even the world, the value of keeping notes is all too obvious.

   Every time I raced in a regional or national competition meeting, I would make detailed notes, aided by a little local knowledge initially and later fine tuned to suit my own driving style.

   My experience now means there are few, if any outdoor tarmac tracks within a 300 mile radius I haven been to and my notes on motor, gearing, camber angles, shock settings, tire choice and what inserts work best for that particular track, amongst others, allow me to save valuable time on the finer points of car setup, that can be done in the warmth of my own home on the kitchen table days before the meeting, instead of the often crippling heat, or the arduous conditions inside a wind blown tent.

   There are lots of methods for making notes on setup. The easiest perhaps is to download the blank pages often supplied by your cars manufacturer with a line drawing of your car and spaces for you to fill in as to the setting you prefer. Great if each time you go to a particular track the conditions are always constant. Notes made on a cold windy day will be little use on a hot sunny days racing on the same track.

   Manufacturers setup pages for their top drivers can also be useful as a starting point, but you should never take that setup as being the best there could ever be.

   So, the first note you should make is of the weather conditions. The wind and its direction isn't really what I am talking about, although it can have an effect on your cars handling, it is not something you can change your setup to handle. Track temperature and humidity are the main things to note. Not the average for the day, but for each round of racing. And note what tires you used and how the car handled in each race. Detail everything that might be useful in the future, no matter how trivial.

   Note the motor used and the gearing. Check the temperature of the motor after the race, how much charge is left in the batteries. You may have won the race, but there is always room for improvement your competitors will be doing just that.

   Every bit of information you compile will be useful for the next time you visit that particular venue. Weather forecasts these days are far more accurate than they used to be, so the adage "fore warned is fore armed" fits the bill. Simply search through your notes and find a day you raced with similar conditions to those forecast and set up your car to suit. But don't stop there.

   The conditions may be the same as they were when you made your notes, but that doesn't mean you can't improve your setup. Your practice laps will soon prove if your previous setup was correct, or give you a basis for more fine tuning.

   If you want to be the best, you have to work at it. Success doesn't come easy. You can be the best driver around, but if your setup isn't perfect you will never step up onto the winners rostrum. My motto if you never try anything, you never do anything. And if you never do anything wrong, you aren't trying hard enough.

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










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