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  • It uses a hand-operating speed regulator to change te output from the motor
  • Optional bumper arms to add control to your runs


To understand the operation of CYCLONE and its difference with common motorized vehicles, it is necessary to identify two events: i) the cart moves in relation to the wheel and ii) the wheel moves in relation to the ground. In a car, the wheels move in relation to the ground, but the main frame never changes its position with respect to the wheels. A motor fixed to the frame (and hence the wheels’ axis) imparts torque directly on to the wheels which, when in friction with the ground, push the vehicle forward. In CYCLONE it is the vehicle that pushes itself forward and, in doing so, it imparts torque onto the wheel by a change in the position of the Centre of Mass (CM) of the system (see LEARN section). In the absence of a net torque applied to the wheel, the system will NOT move with respect to the ground, but that will not keep the cart from spinning inside the wheel! (some rather whacky dynamics that you’ll get to check once you build yours!).

A four-wheeled cart containing the motor sits on top of the wheel track. Traction of the cart with respect to the wheel is achieved through the meshing of a gear on to the teeth of the tracks that form the wheel. The gear is actioned by the motor and the meshing of a pinion and a gear (increase the torque output of the motor and reduce the rotational speed). Even with this reduction, you may find that the speed of CYCLONE is still too fast for a controlled run, and a mechanical speed reducer (05-CYCLONE) is provided. When threaded in, the screw at the top of the reducer exerts friction on the motor rotor making it more difficult to spin, but be careful… this control is too coarse and you can completely lock the motor in a very few turns.

To keep the cart attached to the track and prevent it from “pronating” with respect to it, two screws are used on the panel (gear side) and the cart wheels are provided with a “land” to contact the tracks sideways like the wheels on a train track. A small running clearance exists between wheels and the tracks. These wheels’ axles are locked in place by the attachment of two panels to each side of the cart.

The problem of guaranteeing that the gear remains meshed to the track teeth despite inaccuracies in 3D-Printing is solved by means of a clamp with two rollers on the flat panel side. The clamp action can be adjusted through a screw on top of the battery holder that pushes the rollers into contact with the track wheel.

Because the rotation of the wheel can be quite unstable, bumper arms (13-CYCLONE) can be optionally used. These can be set at different angles if, for example, CYCLONE is to be set to move following a tight or loose curve. The really cool feature about these, is that they make use of a spherical roller which is can be made by the printing of a single part.

Finally a much needed on/off switch is used to power the motor. This diagram shows the electrical connection of batteries and motor. The switch has been designed to withstand heavy-duty vibration. When you first start testing your CYCLONE, you will need to rely on the fact that, if the motor is not turning, it is most likely because of a mechanical reason and not because of a flimsy switch! Also, you will need a quick way of turning it off.



Print all parts in either ABS or PLA except for part 13-CYCLONE (bumper) which needs PLA for accuracy. Other advantages for printing in PLA is that you will get a nicer looking panel at the front shield , but it won’t alter the operation.

FITS: Start post-processing in the following order by checking that the post processed part fits where supposed to (see Drawing BOM). Use a metal file to work on dovetail cavities/etc to achieve each fit.

1. ARC: 09-CYCLONE (fits on both panels 06,07-CYCLONE front side dovetail)
2. SWITCH STATOR: 11-CYCLONE (fits on both panels 06,07-CYCLONE rear side dovetail)
3. BATTERY HOLDER: 10-CYCLONE x2 (fits on both panels 06,07-CYCLONE side dovetails)
4. SHAFT LOCK: 08-CYCLONE (fits panel 06 CYCLONE)


1. Make the 4 wires shown . Note you can use wire 1 and 2 from TRAIN3D If you have made this project. Also note that Wire 3 and 4 do not require a terminal at one extreme.

2. Using scissors, cut all the contacts from K1-AS to the dimensions shown in the Drawing (Sheet 3). Make sure that for contact 2 you carefully produce the middle tab . NOTE: you must exercise EXTREME CAUTION when cutting these. You are responsible for the safe making of these.

3. Using long-nosed pliers, fold contact 1 and 2 tabs to roughly follow these shapes .

4. Screw 2x K1-F8 into the switch stator 11-CYCLONE and then insert these contacts into their respective slots making sure both fit between their respective screw and wall. HINT: you can cut little chamfers at each bottom corner to make the insertion easier.

5. Fold further the tabs, making sure they keep a visible distance from each other.

6. Unscrew K1-F8. Insert nuts K1-NT and washers K1-WSR. Screw K1-F8 again this time using the bare terminal of wires 3 & 4 and a washer in between. NOTE that the order in which everything must be tied in is: NUT-WASHER-CONTACT-WIRE-WASHER. See the Drawing (Sheet 3) for a clear picture. Screw until nothing remains loose.

7. Insert contact 3 onto the switch button slot (12-CYCLONE) until it can’t go in any further. Open up the slot using a knife if it appears closed from the first layer of 3D-Printing. Then measure 4mm and cut as shown .

8. Insert the button onto the stator through a snap fit (make sure the “on” marks “I” coincide.

9. Insert contact 4 (x4) on each battery holder slot. NOTE: you can use the same contacts from TRAIN3D if you made this project.

10. TEST: perform a dry run by connecting batteries, switch and motor according to the diagram. Perform quick on/off cycles and verify that the switch always operates and that no major part is loose.


1. Attach one track on to another by using a nut (K1-NT) and a screw K1-F8 in the respective cavities . You will need a long allen key or hex screw-driver to reach. Clean the cavities from any excess of plastic if the nut/screw does not sit in position. Screw but do NOT tighten yet.

2. When the wheel is assembled, check for a smooth continuity of teeth at the track joints. Do this by laying the wheel flat and by running a screw head around, checking for bumps.

3. If bumps are found align the tracks until flatness is achieved. Tighten screws to the limit.


1. Assemble the gears (K1-G30 & K1-G60) on to the shaft at the distances indicated in the drawing (Sheet 1). Repeat for the pinion (K1-G10) and Motor K1-M2 (note: make sure you’re using the correct motor from KIT K1).

2. Post process the cart- wheels (03-CYCLONE) to fit shaft K1-S3 through by a “snug fit”. The shaft MUST be tight around the wheel bores, so do not file excessively.

3. Open up slightly the cart (02-CYCLONE) bores where the axles are to fit. The shaft must run smoothly through these but at a tight clearance: do not allow the shaft to be too wobbly.

4. Pass both axles and assemble the four wheels. Your cart must be able to roll smoothly. Assemble motor (K1-M2), speed reducer and speed controller. Tighten the screw to lock the motor in position.

5. Position the cart in the wheel.

6.Assemble the geared shaft on to the panel 06-CYCLONE by snapping it first to the top support and with the aid of plyers a slight bent on at the bottom support. Once in position, lock the shaft by inserting the shaft lock . Make sure it spins freely.

7. Screw K1-F12 x 2 to both locations on panel 06-CYCLONE, leaving the heads standing out 2 mm from flushing.

8. Mount panel 06-CYCLONE on to the cart by attaching it with K1-F12. IMPORTANT: CHECK THAT THE GEAR IS MESHING with the track and that the two screws from the previous step are NOT dragging against the wheel.

9.Form the clamp system on panel 07-CYCLONE by following the instructions on page 2 of the drawing and screwing a K1-F12 screw on the battery holder. Assemble the 07-CYCLONE panel on to the cart by means of a screw. Use the screw on the battery holder above mentioned to increase the level of clamping ( .i.e. if gear repeatedly un-meshes from track).

10. Insert the arc, switch assembly and the battery holders on to their respective locations and, without connecting anything, manually run the cart through a full loop. The gear must be meshing with the track and turning the motor without disengaging from the track. If this is the case, adjust the screws on steps 8 and 9 until no disengagement occurs. The cart MUST NOT get stuck anywhere either.

11. Assemble the bumper arms (optional).

12. Connect all cables and you are good to GO! NOTE: if the cart travels in the opposite direction, simply swap the wires from the motor terminals.


The operation of a vehicle with a single wheel like CYCLONE is possible thanks the behaviour of a special point in the system known as the Centre of Mass (CM). The Centre of Mass of a multi-object system is that point inside the system that moves under the Newton laws of motion as if all the mass of the system was concentrated exactly there.

Under the absence of any other force, Gravity would pull a collection of connected objects through its CM. In reality Gravity pulls each object separately, but it is possible to reduce this action to a single location if the location of the CM within the system is known. You can now see how in order to put a system under equilibrium, knowing the location of the CM is a must! If we know it, all there is left to do is to apply a force in the opposite direction to gravity and the system will be in balance.

Take the example of a system formed by a hammer and a ruler simply connected through a piece of rod as shown in the picture . It seems amazing that the hammer hangs from the ruler without it falling down (no glue…). It so happens that the location of the CM of the hammer-ruler system is aligned with the location of the shelf, where a normal force is applied to the system, thus equilibrating it. This is equivalent to having the hammer rest on top of the shelf.

Knowing how to locate the CM of any system has many applications, including the balancing of ships in the water, putting airplanes in the sky and accelerating space vehicles through orbital trajectories. Below we show you how to compute such  location.


The location of the CM depends on the amount of mass of the different objects comprising the system and their distance to the frame of reference from which the location of the CM is being computed. This means that it is expected for the CM to be located closest to where the largest mass in the system is located. In the example of the hammer-ruler, it comes at no surprise that the CM is close to the hammer head. It also means that the CM of an object with homogeneous mass distribution and symmetric shape will always lie in the centre of symmetry.

The formula to compute the coordinate of the CM is:

 D_{CM} = \dfrac{\sum_{1}^{n} d_{n}m_{n}}{M_{tot}}=\dfrac{d1m1+\dotsb+d1m3\dotsb}{m1+m2+m3\dotsb}

DCM = distance in X,Y or Z axis from reference frame to CM [mm], d = distance to individual object (x,y,z) [mm], m = mass of individual objects [g or kg], Mtot = total mass of the system

To compute the coordinates of a simple system:

1) Establish a frame of reference from where the coordinates of the CM would like to be known. This frame can be chosen to be anywhere. The CM will always lie in the same spatial location. In the case of the hammer-ruler system above, we choose the tip of the ruler for the frame location as shown .
2) Break the system into smaller/symmetric objects of homogeneous mass: 1) Head, 2) Handle-I, 3) Handle-II, 4) Ruler.
3) Measure or know the mass of each of these objects.
4) Measure the coordinates (x,y) from the reference frame to the centre of symmetry of each of these objects.
5) Multiply each distance times its mass and add everything up according to the formula. Compute first the X coordinate of the CM and then the Y coordinate.

We perform this exercise for the X coordinate of the CM of the hammer-ruler. The computation is summarized in the table below, with the resulting location being 206 mm. Is the result matching reality ?

  Mass (g)d (mm)M x d (g-mm)(M x d)/TOT/MTOT
2HANDLE I40067.627,040
3HANDLE II150180.227,030
DCM (mm)206


In CYCLONE, when the cart moves forward through the wheel, the CM of it misaligns from the location in which the wheel touches the ground, and from where a normal force is applied to it. The wheel is no longer in equilibrium and must rotate to align back. In doing so, CYCLONE advances forward and an equilibrated motion is established.

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