Ideas for design of passive and semi-active drum pedals

3. DRUM PEDAL PROJECT
• Nowadays, most drummers use a double pedal. Both beaters are attached to the kick-drum. The right beater is
connected to the right pedal by a short linkage and the left beater is connected to the left pedal by a short
linkage and a long shaft including 2 U-joints. Both beaters are connected to the frame by a return spring. The
system pedal/shaft/linkage/beater/spring forms is equivalent to a torsional harmonic oscillator with a natural
frequency:
• 𝒇 =
𝟏
𝟐𝝅
𝒌
𝑰
where K is the equivalent torsion coefficient and I the equivalent moment of inertia.
• Because of the added mass of the long shaft and linkage of the left pedal (higher moment of inertia) do not
respond as well as the right pedal. It is slower and increasing the torsion coefficient makes it more difficult to
operate.

4. DRUM PEDAL PROJECT
• There are basically 2 types of double pedal. The cheap ones, light but suffering from serious rigidity issues and
questionable durability and the expensive ones, with all ball-bearing construction and (sadly) built like a tank as,
it appears, that the more massive they are and the more appealing they are to the customer. (A drummer
joke?...) The moment of inertia increases resulting in a slower pedal.
• The ideal pedal would have a pedal/shaft/linkages/beater’s shaft of zero mass with the total mass of the moving
assembly concentrated into the beater head.
• In addition, the geometry of the linkage is very important in the way the pedal feels.
• The goal of the project was to design, fabricate and assemble a left pedal of minimum mass with adjustable
geometric linkage.

5. SOME OLD SKETCHES
One way to reduce the mass of the long shaft of the left pedal is to eliminate
the shaft completely by building a single-foot double pedal. One beater is
actuated by the heel and the second beater by the ball of the foot. This
would be very useful for a LEG AMPUTEE drummer. Interestingly, someone
beat me to it last year and a small company began to commercialize such a
pedal.
Sketches for unusual
linkages with poor man
kinematics (i.e. paper
and pencil)

6. DRUM PEDAL
This left drum pedal is
built from scratch. It
includes a single arm
ultra rigid frame of T-
6061 aluminum alloy, a
pedal of carbon fiber on
an ultra-light aluminum
frame, a light weight,
fully adjustable, all ball
bearing linkage and a
shaft of large diameter of
thin wall perforated
aluminum tubing.
This was my first project using a milling machine (non CNC alas, and all in inches!)

7. Bonded carbon, carbon ribs, aluminum pedal
Shaft details
Fully adjustable
linkage, machined
T6061 alloy. Note
the Aluminum
fasteners

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10. PEDAL PROJECT-2
• The pedal described earlier functioned very well and my son used it for several years until I
purchased for him, last Christmas, a double pedal from Axis ($780, Ouch!), the only properly
designed pedal on the market in my opinion.
• The shaft connecting the left pedal to the beater is a large part of the problem. So, why not
eliminate the shaft completely? With this in mind, I decided to investigate the possibility of
an electric pedal. The left pedal becomes a sensor capturing the motion of the foot and the
signal is used to propel the beater.

11. PEDAL PROJECT-2Gain
Offset
Pot
The signal from
the left pedal is
transmitted to
the servo
actuating the
beater
The prototype worked well. However, the
servo is not powerful enough, limiting the
intensity and speed of the drummer.
The motion of
the left pedal is
captured by a
potentiometer
connected to a
modified servo
tester wit
adjustable gain
and offset

12. PEDAL PROJECT-2A
• The servo used in the proof of concept did not have the required
torque/speed capabilities required for “spirited” play, even though this servo
was one of the most powerful analog servo available from the RC Hobby
community.
• Larger servomotors exist (CNC milling or routing application for example) but
such expensive components were beyond the scope of this project. We
experimented instead with a combination of servo and solenoids.

13. PEDAL PROJECT-2
Rotary Solenoids
Servo
Solenoid and servo
combination
This prototype uses 2 solenoids to
improve the acceleration of the beater.
Bench Test Stand

14. PEDAL PROJECT-2
PEDAL PROJECT-2
DETAILS
Solenoids
Servo

15. PEDAL PROJECT-2
PEDAL PROJECT-2
DETAILS
Servo
Power
6VDC
Servo
Servo PWM
Signal

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18. PEDAL PROJECT - 3
SEMI-ACTIVE PEDAL – CONCEPTUAL DESIGN

19. PEDAL PROJECT-3
In rock music, the drummer
applies pressure on the
pedal using his thigh and
calf muscles aided by the
weight of the lower leg.
1

20. PEDAL PROJECT-3
The pressure on the pedal
propels the beater forward,
stretching the return spring.
2
A WEAK springs allows the
drummer to hit the drum
head QUICKLY with sufficient
force and minimal effort.

21. PEDAL PROJECT-3
As the drummer releases the
pressure on the pedal, the
spring returns the beater to its
original position and provides
lift to the pedal assisting the
drummer in lifting his lower leg.
The drummer must
lift the entire weight
of his lower leg using
his thigh muscles. This
is the most limiting
factor in term of
playing speed.
3
A STIFFER spring allows a QUICK
return of the beater and provide
more force to the pedal, helping
the drummer lifting his leg
QUICKER with less efforts.

22. PEDAL PROJECT-3
The STIFFER the spring, the
BETTER. The best solution is using
a very stiff spring and provide
assistance to the drummer
through external power for the
forward motion.
The drummer must
lift the entire
weight of his lower
leg using his thigh
muscles. A very stiff
spring will help the
drummer lift his leg
quicker.
4
FORWARD action requires a WEAK
spring and RETURN action requires
a STIFF spring.
HOUSTON WE HAVE A PROBLEM!

23. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The entire assembly
moves down when
the pedal is
depressed
The heavy orange
wheel is continuously
powered by a high
speed motor
StiffReturnSpring
STEP-1

24. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The entire assembly
moves down when the
pedal is depressed
The yellow wheel
connected to the
beater shaft
contacts the orange
wheel powered by
the motor
Slight
Pressure
StiffReturnSpring
STEP-2

25. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The inertia of the
orange wheel and
the torque of the
motor propel the
beater forward
despite the stiff
return spring
StiffReturnSpring
STEP-3
Slight
Pressure

26. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The beater has
reached maximum
extension
Slight
Pressure
StiffReturnSpring
STEP-4

27. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The entire assembly
moves up as the
pressure is released
As the drummer
releases pressure
on pedal, the yellow
and orange wheels
are decoupled
Pressure
Release
StiffReturnSpring
STEP-5

28. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
The stiff springs
returns the beater
to its original
position and assist
the drummer lifting
his lower leg
StiffReturnSpring
STEP-6
The entire assembly
moves up as the
pressure is released

29. Thin Flexible
Carbon Fiber
Plate
PEDAL PROJECT-3
In an instant, the drummer
is ready for the next hit on
the kick drum. The cycle is
complete.
StiffReturnSpring
STEP-7
The entire assembly
remains in the up
position until pressure
is applied to the pedal

30. PEDAL PROJECT-3
CONCLUSION
1. This design is simple. It does not requires complex electronics
such as servomotors, sensors, microcontrollers, etc.
2. For professional drummers kick-drum speed is critical especially
for rock/hard-rock/metal types of music.
3. It takes years of hard work to master this skill.
4. Drum pedal technology has not changed for the last 60 years. It
has only evolved with better materials and tweaking the
geometry. The biggest advance was the introduction of the
double pedal in the 70’. BIG DEAL!
5. No active drum pedal have ever been developed.
6. The biggest and only challenge in the design is the clutch. The
force for clutch engagement must be user adjustable and the
clutch must disengage when the beater hits the drumhead.
Not that easy to do well but not that difficult either.
7. THIS WILL BE A REVOLUTION. THIS WILL BE THE NEW
PARADIGM

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