No…its not a gut affliction. Or a gardening discussion. A recent project got me thinking about the utility of worm gears. And then my experiences with this set got me thinking a little harder about their utility… but lets not get ahead of ourselves…

Time to take a glance at a little Technic… This year I am starting simple. I typically only build a couple of Technic sets per year, and this year I am starting small, with the 42163 LEGO® Technic Heavy Duty Bulldozer. This small set, part of the January 2024 releases has just 195 pieces, and is priced at $14.99AUD/€9.99/$USD12.99/£8.99. It was sent over by the LEGO Group for review purposes, but it might also serve to teach me something more.

“But what? “I hear you cry…let’s us see.

The Elements

Here are the elements: A couple of things struck me about the collection: there were 4 clutch gears, and otherwise one 8 tooth gear, a dual bevel 12 tooth gear, and a worm gear. Everything else was beams, lift arms, axels, connectors and chain-tread. There are NO elements that are unique to this set. The yellow 2×3 ‘shell with cross’ is a new element to me: while it first appeared in 2021, andhas appeared in around 50 sets during that time, I would seem to have built none of them!

The Build

One of the things that strikes me with small technic builds like this is the symmetry around a line: the build is 11 studs wide, with a column of beams filling this axis, not something I am accustomed to with system based builds.

We build up the cabin, and a few system bricks contribute to the front grille of the vehicle.

As we build the model outwards, we have a few half module thick beams, which seem to be a little more common that I remember. At this point, we add in the clutch wheels, on low friction pins. These pins are able to spin inside their connection to the beam, as well as within hub of the wheel

We build up the blade for the front of the bulldozer, using layered beams.

We attach the blade to the axle passing throught the gear that engages with the worm, and add the treads to the wheels.

I have not had much experience with these treads on gears smaller than the 20 tooth gears, and I was impressed by how easily they flowed as the bulldozer rolled along: using the clutch gear, in conjunction with the low friction connector was – providing motion on both sides of the pin. I tested the movement out using the regular, axle-linked 16 tooth gear and found it did not run as smoothly as the clutch gears. Those gears appear to me slightly smaller than the clutch gears, too.

The Completed Build

By rotating the gear on the roof of the cab, we twist the worm gear, and raise the blade. One revolution of the worm turns the gear by one tooth – in the setting of the 8 gear tooth, this gives us a rotation of that gear, and therefore the armature supporting the blade, of 45º. Once the blade is returned to the neutral position, it is possible to drive it downward, until the supports hit the 1/2 width bushes, which limit this moement. This lifts the front wheels very slightly off the ground, and mimics a manoeuvre occaisionally seen in real life. A nice touch that could have easily been prevented by the use of full width bushes.

The completed model glides nicely across the table, and is perfectly suited to tidy up the elements we have left lying on the table.

And this brings us to our completed model.

Things I learned…

So, there are a couple of things I learned with this set. Or was reminded of, at any rate.

1. The utility of the clutch gear with a low friction connector to allow freer rotation compared to the standard gear. Also, the fact that chain/treads can run around 16 tooth gears with little bother. (long known to many, I am sure, it was just new to me. )
2. More importantly, I was reminded about the utility of the worm gear and how effective it can be in gearing down – reducing the speed of rotation and increasing power, all while tranferring the direction of rotation 90º.

Words on the Worm

The worm gear was likely invented by Archimedes at the time of the first Punic war, in the 3rd century AD. The worm screw serves to drive the worm wheel (in less…hobby based settings, the teeth on the worm wheel may well be angled.) While the screw can be used to drive the wheel, it cannot work the other way round.

The larger the worm wheel, the greater the reduction in rotational speed, and increase in torque produced. As mentioned earlier, one revolution of the screw rotates the wheel one tooth. So, with an 8 tooth gear, the rotation is reduced to an eighth of the screw’s rotation. Using the larger 40 tooth gear, you reduce the speed to 1/40th (to 2.5%) of the original speed)

This video demonstrates some of these principles

When I add in the 40 tooth gear on the other side of the build, you can see the difference in speeds of rotation of the two wormwheels.

In conclusion

I don’t expect to learn much, or be surprised by much in a set that costs $AUD15. much from a set. But every LEGO Technic set is going to be someone’s first. And, as well as getting the builder used to the beam, axle and pin construction, this set introduces a valuable gearing technique, while, at the same time, incorporating a couple of regular system elements to help the migrating system builder keep their toes on the ground.

While I have not been in the loop for a lot of these sets in recent years, the majority of sets in this price bracket, until now, have had a ‘B’ Model on the box – often with online instruction – while this set has no alternative build included.

This set is now widely available, and can be purchased at LEGO.com for $14.99AUD/€9.99/$USD12.99/£8.99.

I have a project entering the revision phase which currently incorporates a LEGO Motor spinning at approximately 280rpm. This is a little fast for a ferris wheel, and a worm gear is an ideal first step for slowing it down and turning the direction of the axles’ rotation towards the right direction.

This article has been a slight change of pace, compared to other things I have done lately. Let me know what you think.

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Until Next Time,

Play Well!