RCScrapyard ► Gearing to Win, + Gear Mesh Setting Tips
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Gearing to Win (For Radio Controlled Model Top Level Racing)

How things used to be (Once upon a time ...)


   Just because you have the latest model, the best available batteries, the most powerful electric motor or nitro engine, doesn't mean you will go out and win everything in sight. The fastest car on the track is rarely the one that wins, it's the one that can accelerate out of corners under control, and remains consistent and efficient from the start to the end of a race.

   In days gone bye, all you had to consider was the number of mili amp hours (Mah) in your battery, and the current draw of your high powered motor. Gearing for a five minute race was a balancing act. But with the development of the new high capacity batteries, brushless motors and smart ESC, all that changed. Now, gearing is more of a matter of what suits your driving style and how quick your reflexes are on the sticks, the trigger and steer wheel of your transmitter. So, where do you start?

   At your local club track, you quickly find the right combination and set-up for your car by talking to the more experienced members. After a while, as your knowledge grows, tweaking a few things here and there can give you that small edge to keep you competitive. So, it follows that on tracks you don't know, you should talk to the locals there, who may be racing a similar model to your own, and adjust your set-up to suit.

How to find the Right Gearing (Best Practice)


   Gearing correctly for any given track is absolutely crucial if your car is to be competitive.

   Too high a gearing may get you in front at the start of a race, but as your motor begins to overheat and lose efficiency, that initial advantage will soon be lost.

   Too low a gearing, and although it may get you past your opposition accelerating out of the corners, you will loose that place again on the fast straights. Gearing low will always get you to the end of the race, but it will hardly ever get you on the winner's rostrum.

   Having said that, on tracks you don't know, initially it's always best to err on the side of low gearing. For your first practice laps on a new track, choose a motor that has a reasonable current draw, and with a fully charged battery, try a race length run, learn the corners what line to enter and exit, where you can accelerate to overtake, and how fast you need to be on the straights to keep up (not overtake) the opposition. After your practice race, check the remaining capacity in your batteries and the temperature of your motor, (keep records of each motor and discover at what temperature a specific motor loses efficiency all this helps when selecting the right gearing.)

Use what you Learn


   Armed with this knowledge you can then consider how to alter your gearing.

   If the motor is cool (in comparison) and your battery has ample remaining charge, try a larger pinion perhaps one or two teeth more. Don't overdo it.

   An overly hot motor, and low remaining capacity battery speaks for itself. The race timed practice run should have given you an insight to this problem. Obviously, in this instance you must use a smaller, less teeth pinion, or start again with a milder, less powerful motor.

   If the motor is hot, but not too hot, the battery has ample remaining charge, and you did not notice any drop in efficiency towards the end of your practice run, then you are close to the optimum set up for that particular motor.

   Depending on how competitive that set-up is, you can stick with it, maybe tweak a tooth up or down, or repeat the process with a different motor to get you where you want to be.







RC Model Gears


   In RC there are a number of different gear teeth sizes we tend to use, based on two systems. Imperial and metric. The imperial system has sizes 24dp, 32dp, 48dp and 64dp. DP stands for Diametral Pitch and the number refers to the number of teeth per inch. The metric system has sizes 0.4m, 0.5m, 0.6m, 0.7m, 0.8m and 1m. M stands for Module and is the ratio of the reference diameter of the gear divided by the number of teeth.

Pinions    The different sizes are used basically for strength. 32dp gear teeth are larger than 64dp gear teeth, therefore the 32dp gears are by design stronger and for this reason are more commonly used on a number of entry level buggys, to help them withstand the knocks and crashes by drivers new to RC and nitro models because of the higher torque levels involved. Also, the bigger the scale of the model, the stronger the teeth need to be.

Spur Gears    64dp and its metric equivalents are generally the choice of 1:10 electric on-road racers, because of its higher range of ratio options and smoother action in comparison to other sizes. On-road models are not as hard on the gears as off-road, so the weaker, small tooth size is not a problem.

   48dp and its metric equivalents tend to be preferred by 1:10 off-road racers, mainly because of their strength in comparison to the 64dp and smoother operation than 32dp. Off-road models need gears that can handle all the knocks and bangs, as well as heavy landings off high jumps.

How to set Backlash between Gear Teeth


   Setting your gears is the most important part of looking after your gears.

Backlash    Backlash is basically the gap between the teeth in mesh. The perfect gear setting must have a small amount of backlash. To achieve the best setting use a very thin sheet of plastic between the pinion and spur gear teeth as you press them into mesh. After tightening the motor mount screws, use your fingers to spin the spur gear and roll out the plastic sheet.

Setting Spur Gear and Pinion clearance    If the setting is correct, there will be a small amount of movement (backlash) between the gear teeth before they catch. If the mesh is too deep, there will be no movement between the teeth, this will create friction and if you run them like this, they will grind together, wear and break. If the mesh is not deep enough and only the tips of the teeth are touching, the excessive backlash will soon damage and strip the tops off the teeth rendering the gears useless.

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













24dp Pinion Gears
32dp Pinion Gears
48dp Pinion Gears
64dp Pinion Gears
0.4 Module Pinion Gears
0.5 Module Pinion Gears
0.6 Module Pinion Gears
0.7 Module Pinion Gears
0.8 Module Pinion Gears
1.0 Module Pinion Gears












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