Project Lima: Assault Rifle

Project Date: Sep 2011

I haven't been making any Lego guns for a while now because I don't have enough of those studded beams. But a few months ago I found out that a shop called the Hidden Chamber in Thomson Plaza sells individual parts. That isn't very far from my home and I have been buying parts from there ever since.

Here's my assault rifle made primarily out of those beams found in RCX sets. Another source of those beams are Lego City sets and certain Technic sets, as well as Lego Star Wars sets.


Inspiration was from a few YouTube videos. I figured out the mechanism and incorporated it in this gun.

The mechanism is extremely simple. There is a rammer that is inserted into the magazine before loading. This rammer is connected to a spool at the top of the gun by dental floss. I chose dental floss because of its tensile strength. Once the rammer is inserted, we can begin loading the gun. Bullets (3-hole studless beams) are loaded into the magazine. Each  of the bullets have a rubber band tied to the middle hole. When loading, the rubber bands are stretched and hooked onto a beam at the front of the gun. The magazine can hold around 20 rounds, although I don't have 20 of those 3-hole beams.



The trigger is connected to a PF IR transmitter, tuned to the same channel as the IR Receiver behind the gun. Six PF M-motors serves to drive the spool. A lot of power is required to turn the spool and pull the rammer up due to the friction between the ammo and the magazine. When firing, the bullets are forced up the magazine and fired.

This is the strongest gun I've ever made. The bullets have awesome power and range. They can penetrate paper with ease as well as cause some nasty bruises. To be honest I'm scared of this gun. But also proud of my creation.

And just a note to anyone who want to try building this, you have to make the magazine really strong, or else it will bend and break under all the pressure exerted by the rubber bands. Also I would recommend using dental floss, because every other string that I tried had broke. Also I found out that 20 bullets is really all that Lego can handle, anything more and the Lego pieces can't take the stress, either that or the string will break. If you're thinking to use a rack-and-pinion method to pull the rammer, I would say that it's useless. I've tried and failed, the Lego components can't take the stress.

Here's the video of this gun firing. If you can't see the bullets because of quality issues, just listen to the noise (or watch the targets fall)

Project Kilo: Pen Centrifuge

Project Date: Aug 2011

The Pilot G-2 pen that I (and many others) use is extremely susceptible to ink flow problems if dropped. So I came up with this centrifuge to deal with low ink flow problems.

Depending on your luck, you either end up with a restored pen, or more often than not, a leaking pen. But it's worth a try.

A PF M-motor powers the centrifuge. Theoretically it should spin at 880 rpm, but I think the actual value is closer to 700. The damaged pen refill is placed in on of those small containers. In the other container is a counterweight. Then the centrifuge is turned on.

Centrifugal force pushes the ink out, but this is a gradual process so we'll have to estimate the time needed.

Other than functioning as a centrifuge, I have experimented by adding curved blades (taken from a Technic model) to make a fan. It works great but maybe I'll build a better Lego fan in the future. It doesn't move enough air.

Here's the short video:

Project Juliet: Clean-Up Bot

Project Date: July 2011

Very often I end up with a big pile of Lego on the floor after constructing something. Cleaning up takes a lot of effort so I made up this bot to clean up most of the mess for me. The entire project is made up of two modules.


The first module is the collector. I built it using my NXT set. Two NXT motors lift a scoop made out of paper pasted to a Lego frame, tipping its contents into a cardboard box behind. The NXT is placed in the cardboard box. I originally wanted it to be placed somewhere else, but the wires weren't long enough. The third NXT motor drives a telescopic linear actuator, which turns a PF battery module on or off. Once on, the battery module powers 2 PF M-Motors, which will push a bowling-style arm which pushes anything below the scoop away. This serves to clear the area before the scoop lands after tipping its contents out.

I programmed the NXT such that the scoop will tip its contents out every 9 seconds. At the same time, the arm will be activated. The timing is adjusted such that the arm will activate and retract when the scoop is raised to avoid collisions.


The second module is the tank, or rather, the bulldozer. The chassis I used was my old tank built in Project Delta. I added another battery pack and PF M-motor to power the blade. It is controlled using PF IR control unit, so I could sit on the sofa and let the bulldozer do all the work.

It would have been better if everything is automated, rather than remote controlled, but I didn't have a second NXT set. Nevertheless, this RC bulldozer coupled with the automated collector works quite well at clearing most of my Lego pieces.

Project India: Physics Project

This one is my physics project so there's not much I can talk about. It's not really a Lego Project, although I constructed it out of Lego, since I did not come up with the project.

More Carnage with my Flamethrower

Seeing that my Lego Flamethrower had worked so nicely I couldn't resist burning some more stuff up. Hence I commenced my second round of carnage and among my list of victims are a used G-2 Refill, a plastic case, and some ice. The ice took way too long to melt to be shown on video, thus I didn't include the footage. Here's the video, and enjoy the beautiful flames!

Project Hotel: Flamethrower

Project Date: June 2011

I had created several Lego guns, but they weren't real guns, because there wasn't any explosions to propel the bullets. To make up for the lack of explosions and flames, I made this flamethrower.



The fuel I used was a can of Linx deodorant. A candle at the front ignites the spray, which then completely combusts in front of the Lego frame. The flame has a reach of around 30-60 cm, which is not very far, but considering the simplicity of this contraption, you can hardly complain. Its hot enough to light candles and incinerate ants. Very fun indeed (as long as you're at the right end of the gun).

Watch the video to see the flamethrower in action.

Tips for Lego Gearing

Here are 2 tips that I have for building Lego gear-trains.

Tip 1: Reinforcing Gears

Gears often crack when the gear-train is under stress. Cracking will severely reduce and limit the amount of power transferred and will potentially damage the gears. To overcome this problem, I recommend adding a second mounting beam to the gears, such that the gears are sandwiched between the two beams.

Common Construction:                                                      My Construction:
This method works for almost all types of straight gear trains, even compound ones. It completely eliminates cracking. This is very useful in high-stress applications, for example, sumo bots, cranes, lifting devices, etc.


Tip 2: Dealing with 8-tooth Spur Gears

A problem I observed when building gear trains with 8-tooth gears was their tendency to slip slightly out of alignment.

Perfect Alignment:                                                             Slightly out of Alignment:

As you can see, the gear slips out of alignment slightly, the edge of the gear digging into the mounting hole. This would increase the friction in the gear train and would also limit the amount of stress it can handle. A method I came up with was to use half-bearings as washers, to separate the gear from the mounting beam.

Common Construction:                                                     My Construction:
You could apply the method in Tip 1 to eliminate gear cracking.

Project Golf: Automated Toilet

Project Date: Apr 2011

I've seen how automated toilets work and wanted to turn my home's ordinary toilet into an automated toilet too. So I created a few contraptions using my NXT set to carry out some of the functions of an automated toilet.


The first contraption is the automatic toilet tissue dispenser. A motor drives two pairs of wheels, which act as rollers to pull the tissue through. The wheel has enough grip such that you can tear a piece of the tissue off without pulling the entire reel of paper out. There's also a light sensor mounted between the tissue outlet and a piece of black paper. I'll explain the programming later.


The second contraption is the flusher. The actual mechanism is the tall, tower-like structure; the partially-dismantled cases are just there to add some weight. I used a rack-and-pinion mechanism to drive a beam downwards, which flushes the toilet.

Everything is connected to the NXT, placed beside the flusher. A ultrasonic sensor is mounted to the NXT. The picture at the right shows the entire project. The wire hanging down from the toilet tank is the programming wire, which leads to my laptop (not in the picture).

Here's the programming. The NXT will wait for the ultrasonic sensor to sense a person approaching, by comparing the distance between itself and the nearest object. Assuming that every person entering the toilet will use the toilet, the NXT will then patiently wait for you to do your business. If you're a male, and just taking a piss, then eventually you will walk off without needing any help from the tissue dispenser. So if the ultrasonic sensor senses that you've walked away, then it will return to its original state - waiting for people to enter. But if you've sat down, then the ultrasonic sensor will sense that the distance between itself and you have decreased below a certain threshold, then the NXT will wait for the touch sensor to be pressed. Once you've down your business, and if you need toilet paper, then you press the touch sensor to notify the NXT.

Once the touch sensor is bumped, the motor in the dispenser rotates a certain amount to pull a portion of the reel of tissue out of the outlet. You can then tear the tissue out and use it. Once the light sensor in the dispenser senses that you've torn out that portion, the motor then releases another portion. Once you're done, you will then walk off to wash your hands (assuming that you do, but the robot really doesn't care), then the ultrasonic sensor will sense that the distance has increased a lot. The motor in the dispenser will then retrieve the unused portion of the tissue. At the same time, the flusher will activate, flushing the toilet bowl. Then the NXT will return to its original state, waiting for people to approach, at which the cycle will repeat.

Like any other project, I've recorded a video of it functioning, but due to the complexity of the program, it's hard to show every aspect, so the video is rather unclear.

Project Foxtrot: Lego Minigun

Project Date: Mar 2011

I wanted a Lego gun with a high rate of fire. Miniguns are easy to construct and offer extremely high rates of fire. It was the perfect choice here.

My minigun was a 4-barrel version. An 8-barrel version would have a higher ROF, but I didn't have enough parts. The barrels are connected to a central axle by two 40-tooth gears. The central axle is supported by the handle at the back and a beam at the front. A PF XL-Motor provides the power to rotate the barrels and launch the rubber bands. The battery pack serves as the handle and also supports the central axle. Everything is mounted on a rectangular platform, which also serves as the second handle of the gun (for my left hand).

The string I used was a 3m long Lego string I salvaged from one of my dismantled Technic models. Any other string would hypothetically work, as long as they can fit in the gaps between the pegs.

The rate of fire averaged at 11.2 rubber bands per second, which translates to 672 rounds per min.

Project Echo: Upgrade Pack

Project Date: Mar 2011

I find the rate of fire of the Single-Shot pistol, which I nicknamed Hunter, a bit too low, so I made this make-shift, detachable "magazine" for the gun.

It is attached to the top of the pistol. This makeshift "magazine" holds several rounds and enables the user to continuously fire without having to manually load the bullets. Assembly is done in three steps: attach the outer shell, load the bullets and place the rammer on top of the bullets.


Pardon the ugly outer appearance, I didn't bother to make it look good. It works very well, despite its makeshift appearance. Watch the video for a comparison. The upgrade is nicknamed "auto-mag".

The video:

Project Echo: Single-Shot Pistol

Project Date: Mar 2011

I saw the single-shot gun design from LK Machines and wanted to create a Lego gun for myself. I'm far too lazy to come up with a gun design so just followed LK Machine's. I modified it a bit, though.

The original gun used 4 rubber bands, 2 for the trigger and 2 for launching. By adding 6 more launching rubber bands and strengthening my gun to take the extra load, the force of the bullet is increased dramatically.

As the name implies, this gun has no magazine. Each bullet has to be fed into the launching chamber from the top. This results in low rate of fire. To compensate for this, I increased the number of launching rubber bands  so that each round will hit harder. Using a 2x3 brick as ammo, each round can penetrate a sheet of paper with ease. The gun can accept 2x2, 2x3 and 2x4 bricks for ammo.

Here's the video:

Project Delta: RC Tank Rover

Project Date: Jan 2011

I saw some kids playing with RC toys and decided that I would build a RC toy for myself. A tank was perfect, its treads would mean it's more or less an all-terrain vehicle.

It is entirely based on Power Function components. 4 M-Motors power the treads, 2 on each side. A 2:1 gear reduction provides more torque. A battery pack mounted at the top for easy access provides power. The IR receiver is mounted behind the battery pack.

The frame is constructed using studless construction. It's a very simple design, but very rigid and stable. The treads have limited suspension, allowing the tank to transverse over obstacles without getting stuck. The CG is shifted behind by placing the battery pack at the back, to counter any weight that might be placed in front.

It is true that torque can be improved by exchanging the 4 M-Motors for 2 XL-Motors, but I don't have 2 of them, so I had to stick with this. At full battery, the torque produced is already more than enough, more than what the treads can handle.

One of the design flaws is that the exposed gears may get jammed with foreign objects. I solved this by attaching a cover built much later than this tank to shield the gears. In the video the cover is not shown as at that time, the cover is not built yet.

This tank is very good, considering that I spent just two days designing and building it. I plan to add attachments to make it more useful next time.

Here's the video:

Project Charlie: High-Speed Centrifuge

Project Date: Nov 2010 (Terminated)

I wanted to apply my gearboxes in some structure. I decided on a centrifuge in the end, a high-speed one. Maybe I could have some fun with it spinning stuff around.

But...I was having a tough time designing it on LDD (LDD sucks at aligning gears) and gave up in the end. I was in the midst of construction when I suddenly found interest in building a tank so I decided to abandon this project and go on to build a tank. So that's it, project terminated.

Project Bravo: 4-Speed Linear Gearbox

Project Date: June 2010

As mentioned in Project Alpha, I wanted to create a linear gearbox for comparison. Since my only Power Function motor is used in Project Alpha, I had to use my NXT set for this one.

A linear gearbox is different from the usual one in the way it functions. Instead of having multiple movable "clutches" to engage/disengage gears, in the linear gearbox, the shaft that the gears are mounted on moves such that different sets of gears engage/disengage. "Clutches" are absent, so there is no need to hunt for such exotic Lego parts. A linear gearbox relies on the fact that different gears, when mounted in certain sets, have equal distances between their mounting axles. When constructing such a gearbox, it is important to keep in mind the spacings between each gear on each axle.

Mine have four forward gears, achieved by pairing four sets of gears:

• 24-tooth spur with 8-tooth spur
• 20-tooth dual-bevel with 12-tooth dual-bevel
• 16-tooth spur with 16-tooth spur
• 12-tooth dual-bevel with 20-tooth dual-bevel

Input is by a NXT Motor, output is made more visible using a Lego piece. I programmed my NXT such that the motor would turn five rotations then stop and wait for a bump on the touch sensor, after which the loop repeats and the motor turns. After each set of rotations I would switch gear, then press the touch sensor, because if the input is continuous I am afraid that my gears would grind too much and get damaged. Although, the gear grinding is not an actual issue, as shown at the end of the video when I switched through all four gears while the motor is still running. 

Oh, and, for decoration, I added a useless NXT motor beside the NXT. It's absolutely extra and I don't know why I put it there (probably because I'm more used to a NXT running with two motors, like in a robot).

In the pictures, wires have been mostly removed for clarity.

Please pardon the color randomness, I don't have much bricks to spare.

The results are good; this gearbox is much better than the first one. It can handle stresses very well and the gears hardly crack or grind. Friction is not a problem in this one. The only disadvantage is it's size, despite having fewer gears, it is larger than the first gearbox.

Here's the video:

Project Alpha: 6-speed Gearbox

Project Date: June 2010

My parents bought me a Lego Technic set that has some Power Functions components in it. Since it's my first time playing with Power Functions, I reckoned I would build a gearbox to experiment with the XL-Motor.

It is a basic 6-speed gearbox (1 reverse and 5 forward) that functions using mechanisms very similar to what you would find on a car. Basically movable 'clutches' engage and disengage gears on various axles to generate different gear ratios. I didn't bother to calculate the gear ratios of my gearbox.

I built everything on a 48 x 48 base plate. The motor is placed near a corner and connected to the gearbox by a long axle. I used bevel gears to channel the output from the gearbox to the edge of the base plate where it is more noticeable. I also added a V8 for decoration, looks more complete that way.

The results of the gearbox are not very satisfying. The more serious problems are listed below:

• High energy loss due to friction. Sadly this means that the output is useless for most applications unless you have a powerful motor.
• Gears crack a lot if stress is present. Not serious at lower gears, but at 3rd gear or higher, trying to stop the output with your fingers results in continuous gear cracking (which means the gearbox is effectively rendered useless)

I could solve the problems by rebuilding the gearbox, but I decided to build a linear gearbox to test out the design and compare it to this gearbox. You could watch the video for the operation of this gearbox.