Tag Archives: Gears

More remote control

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In my quest to build a reasonable remote controlled car in LEGO Technic, I tried rebuilding the 2015 off road set 42037. There is space to fit an L-Motor and a servo in the chassis (at the expense of the pistons mechanism for the engine). The battery box fits in the back of the roll-cage, and the IR receiver sits in the driver’s seat.

From a space perspective, this seemed a promising start. The motor shaft has an 8-tooth gear which drives another 8-tooth gear on the differential shaft. I tried various options for holding the drive shaft firmly in place so the gears wouldn’t cog.

This option is sturdy enough that the motor shaft remains in place. In the car, I used 2L and 3L technic liftarms. A stronger connection can be made using 2L (shown in blue) and 3L  (shown in grey) thin lift-arms which have cross-holes for a blue pin-axle.

In the above picture, the dark grey 8-tooth gear is on the motor shaft. (with the yellow half-bush). The light-grey 8-tooth gear is on the tan crown gear that meshes with the differential.

Unfortunately, after a few minutes of play, the L-motor is powerful enough to cause damage to an 8-tooth gear: the teeth are forces sideways (in an anti-clockwise direction in the photo below).

Unfortunately there isn’t space to move the L-motor up vertically without seriously changing the structure of the car. Back to the workbench.

Clock Number 3

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Since Christmas, I have addressed some of the problems that beset my previous clock, particularly the escapement mechanism. JKBrickworks made this fabulous sculpture, and it has a much better escapement in it. I asked if I could steal his idea and incorporated it into my clock.

The escapement mechanism is at the back. In front of that, on the black frame, is the power mechanism and winding mechanism. The clock is powered by weights (two Lego boat weights and an old electric motor) on the end of a piece of string (also a genuine Lego part).

There is also a winding mechanism that allows one to wind up the weight again whilst the clock is working. This took quite a lot of building and rebuilding to get the geometry right. It depends on a differential gear and a ratchet. It also took a few rebuilds to get it to work smoothly. One of the challenges with a Lego clock – in fact with any clock – is that the axles can bind if the frame isn’t rigid. Any axle that needs to go through three holes is especially problematic.

At the front, in the yellow frame, is the gearing mechanism that I used in my previous clock. The only addition is a few gears to make sure that the “ticking” of the escapement (which has 12 teeth, and hence rotates in 12 ticks) corresponds with one tick of the second-hand (which needs to rotate in 60 ticks).

With the gearing ratios correct (it’s not complicated – just multiplication) making the clock keep correct time is mostly about getting the length of the pendulum right. I could have looked up the physics on how to do this properly, but I chose the trial and error method instead. I found a round weight to go on the end (thanks Han Solo) and adjusted it up and down until the timing was about right. The clock keeps correct time for as long as it takes before it runs out of string … just 2 minutes at the moment. Not fantastically practical as a clock yet (and not as long as the previous version), but I’m much happier with the results.

A note about the clock tower: this is a simple construction made of 2×2 and 2×4 bricks using the parts from last year’s wedding cake.

I’m not the first to make a working clock in Lego. Nico71 made this clock with hour, minute and second hands. Someone called Gonkius made a clock which is weight powered, (but automatically winds itself, and uses a Lego Mindstorms robotics controller to adjust the pendulum length to keep correct time). For something really different, DrDudeNL made this Congreve clock in Lego.

 

Clock Number 2

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It’s been a while (too long really) since I blogged about the clock. In that time, I’ve spent much time building, but not much time blogging. So here’s Clock number 2, which I built over the summer of 2015:

A guy called Ben van de Waal has a Youtube channel full of LEGO escapement mechanisms. It appears he just does the escapement mechanisms, not the whole clock.

This clock uses one of Ben’s escapement mechanisms. I chose the mechanism that uses the 40-tooth gears, on the basis that it would give the least rotational motion, and thus the least travel of the string … which would result in a longer running time. That was the theory. This is what it looks like. In the working clock, this is all buried inside the frame.Clock1-escapement-detailIn practice, this mechanism is very difficult to adjust correctly. The blue bar with the pink “cheese” wedges on must be adjusted vertically on the axle by a tiny fraction of a millimetre – which is almost impossible to do in LEGO. The lesson I learned with this clock is that the teeth of LEGO gears are not the right shape for an escapement mechanism.

Nevertheless, the clock works, and it runs for about five minutes.

I also discovered a guy called KEvronista on Youtube and he has made some stunning clocks in LEGO too. Stand with me in awe at the amazing clock mechanisms he has made.