PowerPoint Presentation

Linda HuntApplied PhysicsKettering UniversityCo-op: Warrior SportsGoalie Stick Vibrations

Jimmy Howard, Detroit Red WingsMy name is Linda Hunt and Im a Senior I Applied Physics Major here at Kettering and co-op with Warrior Sports. My talk will be on the vibrational characteristics of goaltender hockey sticks.

FIX: better intro/conclusion1Introduction to Goalie SticksEMA ProcessComparison of results:Wood vs CFEffect of knob on the end capFurther ResearchQuestionsGoalie Stick Vibrations

Cam Ward, Carolina HuricanesA brief overview of the talk I will be doing a quick introduction to goalie sticks with important terms for those who are not familiar with hockey, going over some of the key points about experimental modal analysis, doing a comparison of wood vs carbon fiber, the effect of the knob endo, where I would like to take this project in the future and take questions at the end.2

Types of Hockey sticksButt/EndPaddleShaft/handleBladeToeHeelButt/EndShaftBladeToeHeelFor those unfamiliar with the game of hockey, the top stick is a goalie stick and the bottom is a player stick. I will only be focusing on the goalie stick in this presentation.

Parts to cover:-handle/shaft: the skinny part of the stick where the player holds-paddle: the thicker part of the shaft. This is only on goalie sticks and is used to stop the puck-blade: the curved part that rests on the ice-toe: The tip of the blade-heel: the area where the paddle and blade meet at the bottom of the stick-butt/end: The top of the stick.3Wood SticksFoam-core Carbon Fiber SticksLayers of uni-directional CF ply are stacked on top of each otherOuter layer of entire stick is e-glassHandle part is hollowLight-weight foam in the blade and paddleMore bad vibration than woodThin layers of birch are glued togetherMany sticks have e-glass over the paddle and blade for strengthEntire stick is solid woodHeavier than CF, but less vibrationStill more common in the NHLWood vs Carbon Fiber

Wood sticks are constructed using thin layers of birch that are glued together and many sticks have e-glass over the blades. They are solid, making them heavier than CF, but they vibrate less. Wood sticks are still the dominate stick for goalies in the NHL. A majority of players use composite sticks.

Carbon (CF) sticks are made from uni-directional ply that is stacked on top of each other. Changing direction of ply layers to obtain the desired flex/stiffness. The outer layer is e-glass to provide the toughness. Goalie sticks have a light-weight foam in the blade and paddle, while the handles are hollow. There are more bad vibrations in CF than in wood.4Introduction to Goalie SticksEMA ProcessComparison of results:Wood vs CFEffect of knob on the end capFurther ResearchQuestionsGoalie Stick Vibrations

Ryan Miller, Team USA Vancouver 10Now that we have established a background on hockey sticks, we can go into little theory about experimental modal analysis, the method I use to test sticks.5

ProcessBefore getting to the theory of modal analysis, it may be helpful to show the test setup. The mesh on top is of one goalie stick that I tested. The mesh is created my marking points spaced evenly 1 apart. This tells the computer where the data will be located. The stick is suspended on rubber bands to allow for a free-free condition.

To collect the data, I use a 0.5-g uni-axial accelerometer and a PCB impact hammer connected to a Stanford Research Systems SR-785 frequency analyzer. The data I collect is usually for the frequency range from 0-1.6kHz. The accelerometer is placed at the point at the top of the toe and I do a roving hammer test, meaning that the accelerometer stays in 1 location and the hammer hits all of the other points.

Each test takes about 6 hours to complete as there are between 200 and 300 data points.6Some basic theory: FRF PlotExperimental modal analysis is the study of how points on a structure vibrate with respect to all of the other points on it.

The objective is to get a clean Frequency response function, or FRF. The FRF shows the ratio of output responses of the structure due to an applied force. For this system, the FRF is the accelerometer response of a point on the stick when impacted with a force hammer.

This is an example of an FRF plot for an impact at a point and the accelerometer fixed at the top of the toe. Each peak represents a mode shape. But having only 1 FRF plot is not useful for telling shapes. I need plots for all 300 points to get the mode shapes. As I switch the slides back and forth, there are places where the peak goes away which represent the nodea and the heights show what parts are doing what. The weight and stiffness of the stick determine these peaks. The damping comes from the widths of the peaks.

To obtain the most shapes, the accelerometer is placed on the outside of the structure. Because of reciprocity (Acoustic reciprocity says that if you measure a sound pressure at point 1 of a sound source at point 2 and measure the pressure at point 2 of a source at point 1, they will be the same), I can leave the accelerometer fixed at 1 location and just move the hammer.

**put in a couple plots for different locations to show different positions and how they change narrow frequency range7Some basic theory: FRF PlotExperimental modal analysis is the study of how points on a structure vibrate with respect to all of the other points on it.

The objective is to get a clean Frequency response function, or FRF. The FRF shows the ratio of output responses of the structure due to an applied force. For this system, the FRF is the accelerometer response of a point on the stick when impacted with a force hammer.

This is an example of an FRF plot for an impact at a point and the accelerometer fixed at the top of the toe. Each peak represents a mode shape. But having only 1 FRF plot is not useful for telling shapes. I need plots for all 300 points to get the mode shapes. As I switch the slides back and forth, there are places where the peak goes away which represent the nodea and the heights show what parts are doing what. The weight and stiffness of the stick determine these peaks. The damping comes from the widths of the peaks.

To obtain the most shapes, the accelerometer is placed on the outside of the structure. Because of reciprocity (Acoustic reciprocity says that if you measure a sound pressure at point 1 of a sound source at point 2 and measure the pressure at point 2 of a source at point 1, they will be the same), I can leave the accelerometer fixed at 1 location and just move the hammer.

**put in a couple plots for different locations to show different positions and how they change narrow frequency range8

What are mode shapes?Bending ModeTorsional ModeThe last bit of background required for EMA is what mode shapes tell us. To get these animations, I put the data from the FRF plots into a computer program called StarMODAL and it processes these movies. These are some sample mode shapes for one stick. The places where the stick do not move are called nodes and the maximum deflection places are anti-nodes. A bending mode is just as it sounds there is bending along the stick. The number of nodes corresponds to the mode number it is so for the 3rd bending mode, there are 4 nodes. The other type of mode that we see is the torsional mode, which is a twisting along the stick.9

Goalie Hand Location

Jon Quick, LA KingsMarty Turco, Dallas StarsI want to focus on bending modes that have an anti-node in the area where a goalie holds his stick. When in a defensive (USE DIFFERENT WORD?) stance, the blocker hand is at the point where the shaft and paddle intersect. It is only when playing the puck that the goalie may move his hand up the stick. Since the primary position of the hand is at the top of the paddle, I am also focusing on any anti-nodes that appear in that area.10

200-300 Hz Is considered most sensitive to the human hand

Source:D. D. Reynolds, K. G. Standlee, and E. N. Angevine, Hand-Arm Vibration, Part III: Subjective Response Characteristics of Individuals to Hand-Induced Vibration, J. Sound Vib., 51 (2), 267-282 (1977).Hand sensitivity rangeAs stated earlier, I collect data for a range from 0-1.6kHz, but in terms of a goalie, some of that seems to be less useful than others. My focus for this project is to find out what vibrations goalies are feeling when they use the CF sticks and try and eliminate them. This plot relates amplitude of displacement and frequency to how sensitive a persons hands are and shows that at lower and higher frequencies the amplitude of the vibration needs to be a lot higher than the range between 200-300 Hz. So for this reason, I am focusing my data on the range from 200 to 300 Hz.11Introduction to Goalie SticksEMA ProcessComparison of results:Wood vs CFEffect of knob on the end capFurther ResearchQuestionsGoalie Stick Vibrations

Manny Legace, St. Louis BluesNow that I have set a basis for what I did and why, we can move into the results section to see the outcome of this testing and determine what the results mean.12WoodComposite 1Composite 2FreqDampFreqDampFreqDamp1192153.11912122415.623813.72813.531115.13135.32923.634122.03876.3Wood vs Carbon FiberFirst, I wanted to take a high-end wood stick and compare with a high-end composite stick with a foam core to better understand the differences in frequencies and mode shapes. Basically, scientifically determine why guys prefer wood over composite.

As you look over these numbers, they are laid out based on mode shapes that are similar. Based on the damping results for the composite sticks and wood stick, there is a lot more damping (around 3-5 x) in the wood stick than in a composite stick, which goalies want because they dont need to feel the puck as a player does, and they do not like the ringing sensation when blocking a shot. The frequency content is also different there are more higher frequency vibrations in composite sticks than wood sticks and the same mode shapes have higher frequencies in CF than in the wood.13WoodCF 1CF2Wood vs CF: Mode Shapes

Bending 215 HzBending 191 HzBending 238 HzTors 212 HzTors 241 HzBending 313 HzBending 281 HzTors 311HzTors 292 HzThese are the mode shapes of interest for the 3 goalie sticks discussed on the previous slide. This shows a side-by-side comparison of the same mode shapes, but the frequencies are different. The sticks with the red boxes around them are ones that I see as being potentially problematic for goalie feel as they have strong anti-nodes in the area where a goalie holds the stick.14Introduction to Goalie SticksEMA ProcessComparison of results:Wood vs CFEffect of knob on the end capFurther ResearchQuestionsGoalie Stick Vibrations

Martin Brodeur, NJ DevilsAnother thing that needs to be taken into account for testing on goalie sticks is the tape that guys put on the stick.15

Effect of Stick Tape NHL Rule: tape knob on endMost NHL goaltenders tape the stick on the blade as shown in the picture on the left. The tape is a cloth material and usually only 1 layer is applied there. A substantial amount of tape is applied to the butt end of the stick to allow the goalie to pick up the stick when it is dropped, give him better grip when poke checking and also to give players protection when jabbed in the ribs or back with the end. The NHL mandates that this knob be no smaller than and inch thick but many guys use more tape than that. Because of the substantial amount of tape used on the stick, I also studied the effects of a naked stick vs one with a taped blade and knob.16No tapeWith tapeFreqDampFreqDamp1912415.62137.52813.52614.82923.6Tape vs No TapeAgain, these tables line up the mode shapes to show the differences in frequencies. Tape adds a significant amount of damping to the system and lowers the frequencies a bit, something we expected with the mass loading. Also, something that isnt shown in this table is that there were less mode shapes for the taped stick and the higher frequencies did not show up.

17Without TapeWith TapeMode Shapes

Tors 213 HzTors 241 HzBending 281 HzBending 261HzIn addition to the frequencies changing for the sticks, the node locations moved toward end when the stick was taped. Also, there were less shapes at higher frequencies and also less shapes in the range we were targeting.

With the significant differences between the taped and un-taped cases, I think that any future work needs to be done with the knob on the butt of the stick.18Introduction to Goalie SticksEMA ProcessComparison of resultsWood vs CFEffect of knob on the end capFurther ResearchQuestionsGoalie Stick Vibrations

Scott Hooper, Kettering University(Class of 2009)With that, we head into the future angles of this project19Without TapeWith TapeMode Shapes

Tors 213 HzTors 241 HzBending 281 HzBending 261HzFor future research, Id like to experiment with a mass-spring damper for composite stick to dampen sting felt. Going back to the slide of the sticks with tape and no tape, the two shapes with the red boxes around them are the two modes that I would like to target with this vibration absorber. These have frequencies of 281 Hz and 261 Hz. The reason I chose these is because they are within the hand sensitivity range and they also have the most dominant anti-nodes in the range of human feeling.20Questions?

Jimmy Howard, Detroit Red WingsI hope that you now better understand why goalies currently prefer wood sticks over CF sticks. It is due to the damping being greater in wood sticks, and also less mode shapes in the range where human feeling occurs. This concludes my talk on goalie sticks and I would like to thank Sherwood, Vaughn and Warrior for donating sticks to this project. Are there any questions? 21