1. Roller Coaster Design Calculations
Goal
Learn a method for calculating roller coaster velocities
Objectives:
Roller Coaster Calculations - At the end of the session, students should be able to:
Calculate velocities for all segments of their roller coaster
NOTE: There is a handout with this lecture.
It is very important that the students and subsequently the instructional staff put a lot of emphasis on
the initial paper design. It has two benefits. First it models good design practice and second it should help
Students provide designs which have a better chance of being successful in the limited lab time available

2. Initial Paper Design (8% of course grade)
IMPORTANT - Read project description document in your course package carefully.
Initial Paper Design:
Produce a sketch of your design with dimensions
Produce a comprehensive set of velocities for all segments of your design
Analysis of your calculations and design
Stress the importance of reading the project description document if the students haven’t already. In it is a section that describes
the specific requirements for the paper design.

3. Sample Initial Design Sketch
Φ 254
508
813
1219
914
457
203
Dimensions are in mm
Sample Initial Design Sketch
Top View
Front View
Sketch by
Amanda Zook, Nick Persico, Scott Stultz, Dante Henderson from ENG183 Spring ’04
(Modified for instructional purposes)

4. Excel Calculations
An Excel spreadsheet has been provided for you in the course website .
This spreadsheet is based on the Physics of conservation of energy as described in the labs:
The sum of kinetic, potential, and energy losses must be the same at all points on the roller coaster
Three types of energy loss coefficients are included:
Frictional losses on straight track sections
Losses associated with speed (i.e. air resistance)
Losses associated with “G” forces (centripetal acceleration – changed normal forces)
The spreadsheet is shown in the next slide.

5. Excel Spreadsheet for Calculations
Set the loss coefficients
to the values shown for
this lecture’s examples.
PE1=Potential Energy
TKE = Translational KE
RKE = Rotational KE
E = Total PE + KE
The values for the energy loss coefficients are highlighted. The arrow indicates where the loss calculations are used.

6. Calculations for each segment of the Roller Coaster (without curves/loops)
For the start of the segment identify the height and put this value in h1
For the end of the segment identify the height and put this value in h2
The difference between s1 and s2 is the track length of the segment
Enter the velocity coming into the segment as v1 (zero if this is the start of the track)
Adjust values of v2 until the two energy values in blue are equal
Two procedures are shown. One for segments without loops or curves, and one with loops and curves. Note that curves
include horizontal curves for changes in the direction of the roller coaster in addition to the horizontal loop required. Horizontal
curves create ‘G’ forces that increase losses.

7. For segments without curves/loops
Height of start
Height of finish
Track length
Initial velocity
Highlight the need to adjust v2 until blue E’s are equal. This allows for energy losses to be accounted for. The iteration
is required because one of the loss coefficients is a function of velocity.
Final velocity-
Adjust until blue E’s are equal

8. Let’s calculate some of the velocities for this design
Segment 1: Start to loop entry
No loops or curves in this segment so:
h1 = .762 m
h2 = .254 m
v1 = 0 m/sec
s1 = 0 m
s2 = .683 m (determined by trigonometry, or measured)

9. Plugging in the values h1,h2,s1,s2,v1
NOTE: These Energy’s are not equal

10. Adjust v2 until blue E’s are equal
Final v2 = m/sec
MUST BE CLOSE TO EQUAL

11. Segment calculations with curves/loops
In addition to the h1, h2, v1, s2-s1 values there are other entries needed when centripetal acceleration is involved
In the lower portion of the spreadsheet is a section for horizontal and vertical curves/loops
Enter the diameter, Dh(horizontal) or Dv(vertical) curve/loop
Adjust values of v2 until the two energy values in blue are equal
The only change in procedure for loops or curves is the specification of diameter (or radius of curvature *2), and segmenting
the features for calculations, where appropriate

12. Loops and curves
Step 3: Adjust final velocity until energies are equal
Step 1: Enter
h1,h2,s1,s2,v1
Step2: Enter
Dh or Dv
Highlight the sequence of steps.

13. Vertical loops
For vertical loops the calculation needs to be broken into two separate segments.
First perform a calculation for the velocity from the entry of the loop to the top.
If velocity on the loop top is less than , where r is the radius of vertical loop, the ball cannot go through the loop.
Then perform a subsequent calculation for the velocity from the top of the loop to the exit
NOTE: If the radius of curvature is small, the ball radius needs to be considered in the calculation. For instance, in a vertical loop, if we
consider the path of the center of mass of the ball, there is a smaller difference in height change

14. Bump Calculations
It is important to calculate the velocity of the ball when it reaches to top of the bump
If its velocity exceeds , where r is the radius of curvature of the bump, the ball will leave the track
To do this calculation break the bump into two ramps, one from the start to the top, and the other from the top to the end

15. In-class exercise: Calculate the velocity at the top of the loop
From drawing:
h1 = ?
h2 = ?
s1 = ?
s2 = ?
v1 = ?
Dv = ?
Plug into spreadsheet
and iterate to determine:
v2 final = ???
A slide follows that has the correct answer. After letting the students work for a while, you may want to display the answer.

16. In-class exercise : Answer
h1 taken from diagram
s2 calculated as pi*R = 3.14*.125 (half loop circumference)
v2 determined by varying v2 until blue E’s at bottom balance (note they are not exactly equal, but this is close enough)
Don’t forget Dv

17. Is the velocity high enough to stay on the top of the loop (with some extra for insurance)?
(gr)1/2 is m/s – so our 1.60 looks good
Now let’s walk through the next three segments of the roller coaster design.

18. Top of Loop to Bottom

19. Loop Summary The velocity into the loop was: 2.4665 m/s
The velocity out of the loop was: m/s
Some energy was lost.

20. Straightaway
NOTE: Small Loss

21. Horizontal Loop
2 ½ horizontal loops

22. Loss Coefficients
During the early roller coaster labs you will determine values for the loss coefficients that you can use in your initial paper design.
These do not account for all losses in a roller coaster design. Poor supports or steep drops can produce losses in addition to those calculated by this spreadsheet.
Initial values for your design are given in the spreadsheet.

23. Horizontal Loop Summary
Velocity going in: m/s
Velocity going out: m/s
What kind of bank angles will be needed? r
Almost all teams wind up having turn velocities much too high. This team could have done three things: Reduce their starting height (which would also
have required making the vertical loop smaller, add a rise after the vertical loop to slow the ball down before the horizontal loop, or put the horizontal
loop later in their design when the ball has lost more energy.
Φ in 76.5º, Φ out 72.4º
Do you think this will be stable?
What could this team have done differently?

24. Roller Coaster Design Considerations
One of the most difficult things in creating an interesting Roller Coaster design is controlling the velocity of the ball. If you think about the most fun roller coasters that you’ve ever been on, they’ve had changes in velocity rather than everything at one speed. Controlling the velocity of the ball makes performance less dependent on small changes between runs (and small defects in the track). This and a good support structure lead to a stable, reliable coaster design.

25. Initial Paper Design
The Excel spreadsheet can be used for most of the calculations required in the initial design. There are other calculations which will use the information you learned during the labs, i.e.
banking angle for horizontal curves
distance ball will land after leaving the end of the track
etc.
Read the project description document to understand all of the requirements!

26. Brainstorming
Use the rest of this session to brainstorm ideas for your coaster with your team. Remember to include all of the required features. Remember that you need to submit calculations using the spreadsheet shown today for your entire initial design.