Now that I've finished my review of the new WL Toys 104001 4wd 1/10 scale RC buggy it's clear that this is nowhere near as fast as the earlier 124018/124019 and 144001 models which uses essentially the same electronics. In this article I look at how easier it is to close this speed gap and the theory around it.
When the 144001 was released, the speed they got by using an oversized brushed 550 motor was impressive - around 50km/h flat out. This was due to an oversized motor and tall gearing in a fairly small car. Obviously we've seen smaller brushless setups like even this budget one go much faster but the brushed electronics keeps the price down. Moving on to the new 104001, we have essentially the same electronics but the motor is no longer oversized, rather it is more appropriate for this size of car.
Many people have said that the 104001 is slow because it uses the same running gear with more weight. That is only *slightly* true - acceleration is inversely proportional to weight (F=m.a) which gives the sense of speed but top speed is only tenuously linked to weight. The main reason the 104001 is slower is actually due to shorter effective gearing. As much as I did moan about the gearing in the 144001/124019/124018 being to tall, this really did bring out the performance which feels lacking in the 104001. The good news is that with a more common gear pitch and an adjustable motor mount this is an easy fix. If you don't want to go into the theory below then skip the next section and go to the solution
Gear ratio theory and comparison
RC cars and indeed real cars use reduction gearboxes that not only transfer the rotational energy from the motor to the wheels but also reduce the speed in order to take advantage of the motor's power band. This means the for every revolution for the motor, there is less than 1 revolution for the wheels. This gear ratio is a result of the differing gear sizes in the car namely the motor pinion to spur gear and then the differential pinion to differential ring gear. Lastly the diameter (or rather circumference) of the wheels then has the final say as mentioned in my article on wheels here. So let's cut to the chase and do a direct comparison,
This is pretty astonishing information - assuming the motor is reaching it's maximum speed this would mean the small 144001 should be roughly double the speed of the 104001, even taking the smaller wheels into account. Clearly this is not true as the top speed of the motor is being limited by friction and other real world conditions.
Regardless, this is a massive opportunity to increase the speed of the car through gearing. At this stage in the absence of other spur options we need to change the pinion. The good news is that mod 0.6 pinions that fit this car are readily available in a wide range of sizes and are super cheap - like $2 cheap when you buy in a 5 pack as below:
The largest pinion that is presently available and fit without modifying the motor mount is 31t. Without going back through the maths this will give over 40% more to speed from gearing at around 41mm travelled for each turn of the motor. Alright, lets get some real world results and test our hypothesis that a 31t pinion will net us a 50% increase in top speed. We can ignore friction for now 😅. You'll note below that I had to remove the gear shroud to fit the 31t pinion - 29t is about the largest that will fit with the shroud.
Job done - the shroud is not needed to secure the spur gear assembly but take care with wire routing as more moving parts are now exposed
Does the new gearing give us more speed?
Another 8km/h represents a 20% increase in top speed for just $2: this is a noticeable difference in anyone's book and it definitely does look faster too. No, it's not *quite* as fast as the 124019 but it's a darn sight better than stock.
It is worth noting that the car does take a while to wind up to top speed on this gearing. If you are doing straight line runs the ESC and motor will get only just warm but as soon as you start cornering, accelerating, decelerating, skidding etc the motor and ESC get hot quickly and battery life takes a hit. This is a sure sign that the gearing is too tall for the weight of this car on day to day bashing and the like. Good thing you have lots of spare pinions in the pack then to experiment which gives you the best balance of speed, acceleration, heat control and battery life for the way you drive on the surface that are unique to you. Personally I've settled on a 28t for now.
Thanks for reading and if nothing else you've found a way to get a little more speed out of your stock car for not a lot of money but more importantly you have more of an appreciation for gearing - an option we never really had for the earlier WL Toys models. Enjoy!
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