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Meg Chen |
University of British Columbia |
PHYS 420C (2024) |
Design + Construction
The complete design of the ballistic cart can be
accessed from this Onshape Design Link.
Cart body
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1)
Gather
the materials. (base, sides, wheels,
rods for the wheels, spacers,
hook, #8 x 3/4" wood screw x 12, flange) 2)
The result should look somewhat like this. Please
keep this image in mind while you proceed.
3)
Take the base, note how there are 12 holes on the
bottom.
4)
Align the side panels as they would appear in the
final assembly. We will be drilling 4mm holes into these side panels using
both a drill press and an electric drill. 1.
For each side, start by drilling a hole with an
electric drill Note: Please be very careful and try your best to drill
vertically in. 2.
Screw the screw in the hole drilled, then align the
side and the base as what the final product look like (This screw will keep the side and the base in place
while you drill with the drill press) 3.
Secure the base and the side
with a drill press vise 4.
Using the drill press,
carefully drill the remaining 5 holes on the side, using the holes on the
base as guide Note: It might be easier to screw the
base and the side together after drilling more holes, just to keep them more
aligned. Note: When using the drill press, gently
move the bit up and down as you drill to help clear debris and make the
process smoother. 5. After drilling all 6 holes on one side, remove all the screws and repeat
the process for the other side. Note: you can use a bigger drill bit to
manually clean the edges of the holes. 6. After all the holes are drilled, screw the base and the side together. 5)
Turn over the cart, note
that there is a hole in the middle. We want to make the hole like a cone
shaped, with bigger drills, by carefully drilling it bit by bit with an
electric drill. The result should look something like this (without the holes
around it yet):
6)
We
will now move on to the wheels. Note: Be cautious during assembly. The wheels may
become loose and wobbly if you remove and reinsert them, so try to assemble
them correctly on the first try. Note: Refer to the result image when working on it. 1.
Hammer
one side of the wheel into the rod carefully. Note: Make
sure that the wheel and the rod are perpendicular to each other. 2.
Put
in one spacer. Then put the rod through the holes on the side of the cart
body. 3.
Put
in another spacer and carefully hammer the wheel on the other side into the
rod. (put the cart sideways) 4.
Repeat
the process for the other two wheels. 5.
Check
that the result looks like the expected image above. 7)
Use
hot glue to attach the hook on to the cart body. 8)
Complete!
Now let's move on to the cannon. 😊
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Cannon
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2)
The result should look somewhat like this. Please
keep this image in mind while you proceed.
3)
Note that from the image in
the previous section, there are holes around the middle hole for holding the
flange in place. 1. Keep the cart upside down, use the flange and a marker to decide where to
place the flange so that the middle hole is in the center of the circle. 2. Mark where the flange will be touching the base with a marker 3. Turn the cart right side up and put the flange on top of it at the marked
place. Use masking tape to secure the flange 4. Mark where to drill the holes on the flange. Remember to leave one spot
undrilled as shown in the images above. It is done to leave space for the
metal plate in a later step. Note: The spot left undrilled must be on one of the short sides, as shown
above. 5. Secure the cart body with a bench vise and carefully drill the holes marked
with a 4mm drill bit through the flange and through the cart. Note: It would be helpful to keep the cart body and the flange together
by putting in the bolt and nut after drilling one hole. 6. Unscrew all the nuts and bolts used to secure the flange 7. Check that your base now has 20 holes (12 on the sides, 1 in the middle,
7 around) 4)
Now
we want to connect the flange and the cannon, as shown here:
(The area with the blue masking tape is the area
without the hole) 1.
Mark
on the flange where you want to drill the holes Note: Use washable markers if you don't want the marks to be
visible later. 2.
Use
masking tape to connect the cannon and the flange from the bottom. Note: attach the cannon such that the sides with the slots cut
are both equally away from the area without the hole.
3.
Secure
the cannon + flange with the drill press vise Note: Insert the piston into the cannon and clamp the vise around
the piston area, so that the cannon does not deform during the drilling
process. 4.
Carefully,
using the drill press, drill the holes with a 4mm drill bit. Note: it is important to make sure that the bottom of the flange
and cannon are aligned perfectly, or the cannon will be slanted, and the
demonstration will not work! 5.
Secure
the cannon and the flange with the bolts and nuts 6.
Check
that it looks like this so far:
5)
For
the spring, use hot glue to attach the spring to the spring holder. Note: make sure to not have any glue in the middle for the rod
used to trigger the system to go through.
6)
For
the piston, the result should look like this:
Note: there is a separate acrylic part on top of the piston in
the picture above. In the updated version, I have modified the Onshape design
so that the two parts are combined :) 1.
Using
a hacksaw and a flat steel file, make the rod used to lock and trigger the
launch like the following:
Note: It looks like a right triangle with a base of around 2mm,
make sure that the base of the triangle is horizontal. 2.
Use a
hammer to insert the rod used to trigger the launch into the center of the
piston, as shown.
Note: Make sure that the rod is inserted straight in, not at an
angle. 3.
Make
the hole in the middle of the piston's edge a bit wider (5mm) using an
electric drill. Make sure that the rod for holding the piston can go in
easily. The rubber tubes are used to keep the rod in the piston.
7)
We
are now ready to put everything together!
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Putting Everything Together
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1) Using hot glue, attach the spring part to the base
of the cart. (around where the circle is drawn) Make sure that the hole in
the middle is in the middle of the spring.
2) Put the piston in the cannon, make sure that the
"triangle" indent of the rod is facing the side where the flange
doesn't have the hole. Secure with the rubber tubes.
3) Using the bolts and nuts, connect the cannon part to
the cart body (might be tricky with the spring inside) 4) Make sure that the triggering rod can be pushed
through the hole in the middle of the cart easily and that it bounces back. 5) Turn the cart upside down, use hot glue to glue the
metal plate on to the cart, at the space we purposely didn't drill the hole
at. The metal plate should cover around 1mm of the hole. When the triggering
rod is pushed down, it should be able to catch onto the metal plate, stay
locked, until it is released by being gently pushed upon. Reattach the metal
plate accordingly so that the trigger system works. Note: spraying alcohol on top the glue can help greatly with
cleaning it.
Note: I recommend first using a tape to check and confirm the
place you want to put the plate, then, while keeping the tape on, use hot
glue to attach it more firmly. 6) Turn the cart back, make sure that the triggering
system still works. 7) After constructing the train and the track and
reading the instruction page, check that the cart works in all 4 situations. Debugging Tips: -
If the ball
launches higher than expected, use pipe clamps to restrict the movement of
the piston. -
Use your phone's
level tool or a bubble level to make sure that the surface is perfectly
horizontal. (If the surface is tilted the demonstration will not work) -
Note that the
metal plate will wear out over time. When that happens, the rod will not be
able to lock to it. Take the metal plate out, rotate it, and glue it back on
when that happens. -
Make sure that the
cannon is perpendicular to the surface when it is placed on the track -
Adjust the speed
of the train by turning the screw of the DC-DC buck converter module to reach
the speed you want. Tip: after making
sure that all the parts work properly, you can add some hot glue to the area
connecting the triggering rod and the piston to make it more secure. |
