# Stern Tech School: Jurassic Park T-Rex Removal **Source:** Stern Pinball **Type:** video **Published:** 2024-10-05 **Duration:** 11m 22s **Beat:** Pinball **URL:** https://www.youtube.com/watch?v=JbkVNcIRhj4 --- ## Analysis Stern Pinball's Tech School video provides a comprehensive technical walkthrough of the T-Rex animatronic assembly in Jurassic Park Premium, explaining the stepper motor horizontal movement system, geared DC motor vertical positioning, solenoid-operated jaw mechanism, and magnetic ball-catching functionality. The video demonstrates how these components integrate through a test fixture and explains adjustment procedures and diagnostic testing methodologies. ### Key Claims - [HIGH] T-Rex assembly uses a stepper motor for horizontal (left-right) movement and a geared DC motor for vertical (up-down) movement — _Direct technical explanation with demonstration of both motor systems and their controllers on test fixture_ - [HIGH] Horizontal positioning relies on a center reference point detected by a microswitch that the stepper motor homes to during operation — _Detailed explanation of stepper motor logic with cam mechanism and microswitch trigger point clearly demonstrated_ - [HIGH] T-Rex jaw opening/closing is controlled by a small solenoid inside the head that energizes a plunger-sled mechanism with lever action — _Physical demonstration and explanation of solenoid plunger mechanism with spring return and jaw mechanics_ - [HIGH] Ball capture uses an internal relay coil magnet that energizes when the T-Rex is lowered with jaw open, catching the ball when shot up the ramp — _Explicit explanation of magnet energization sequence and ball capture logic with animation sequence description_ - [HIGH] An opto sensor inside the T-Rex jaw detects whether the jaw is open/closed and whether a ball is present by sensing beam interruption — _Clear demonstration of opto transmitter/receiver beam and three distinct states: jaw open empty, jaw closed empty, jaw closed with ball_ ### Notable Quotes > "With the T-Rex assembly we have two coils and we have two motors. There is one motor that is responsible for horizontal movement and there is one motor that is responsible for vertical movement. The horizontal movement is a stepper motor and the vertical movement is a geared DC motor." > — **Stern Tech School presenter**, ~1:45 > _Establishes the foundational architecture of the T-Rex system with motor function allocation_ > "A stepper motor in software it knows, let's use an arbitrary number. We need to step 60 steps to the left and it's going to find that center switch and go 'Okay, 60 steps this way' and then in software it might be called to go right again." > — **Stern Tech School presenter**, ~4:30 > _Explains the software-hardware coordination for stepper motor positioning logic_ > "When the solenoid is energized it will attract this plunger here that is attached to this sled. There's two pins on either side of the sled that are attached to the jaw. When the coil energizes and the plunger for the sled is energized, it pushes the top of the jaw forward and levers it open." > — **Stern Tech School presenter**, ~13:30 > _Detailed mechanical explanation of jaw actuation via solenoid-plunger-lever system_ > "Spoiler alert: in Jurassic Park Premium, when you start some of the T-Rex events, the T-Rex will be lowered down with the jaw open. And when you shoot up the ramp this magnet inside will be energized, waiting for the ball." > — **Stern Tech School presenter**, ~14:30 > _Reveals gameplay sequence and magnet timing for ball capture mechanic_ > "If we have a ball inside and the jaw is closed, the beam is now broken. So the game knows that the T-Rex does have something in its mouth." > — **Stern Tech School presenter**, ~16:00 > _Explains opto sensor logic for detecting ball presence within T-Rex jaw_ ### Entities | Name | Type | Context | |------|------|---------| | Stern Pinball | company | Producer of Jurassic Park Premium pinball machine and Tech School educational video series | | Jurassic Park Premium | game | Pinball machine featuring the T-Rex animatronic assembly being documented in this technical walkthrough | | T-Rex Assembly | product | Complex animatronic mechanism in Jurassic Park Premium featuring dual motors, solenoid jaw actuation, magnetic ball capture, and three-position vertical indexing | | Spike 2 | product | Runtime environment and hardware platform referenced for diagnostic functions used in T-Rex testing | | Stern Tech School | organization | Educational content series from Stern Pinball demonstrating technical aspects of pinball machines and assemblies | ### Topics - **Primary:** T-Rex animatronic mechanics and engineering, Stepper motor control and positioning logic, DC motor vertical positioning with multi-position indexing, Solenoid-actuated jaw mechanism design, Magnetic ball capture system, Opto sensor detection and beam logic - **Secondary:** Field adjustment procedures for T-Rex assembly, Diagnostic testing methodology on Spike 2 platform ### Sentiment **Neutral** (0.5) — Content is educational and technical in tone with no evaluative or emotional language; presenter maintains neutral, informative delivery throughout ### Signals - **[community_signal]** Stern Pinball producing detailed technical education content (Tech School series) demonstrating commitment to operator and owner education regarding complex mechanical systems (confidence: high) — Full production video with multiple camera angles, test fixtures, demonstrations, and detailed explanations of T-Rex assembly internals and adjustment procedures --- ## Transcript have you ever wondered how the T-Rex and a Jurassic Park premium works well in this video let's take a look at the mechanics to see how the magic is made now that we are at the bench we are sitting with our T-Rex test fixture so this is essentially just a back panel from a Jurassic Park premium and we have some Electronics bolted to it like a node board we have another lamp board back here but other than that the rest of it is exactly how it would be in your game on the left we have a spike 2 like kind of runtime environment and this allows us to be able to use the diagnostic functions on the device with the T-Rex assembly we have two coils and we have two motors there is one motor that is responsible for horizontal movement and vertical movement the horizontal movement is a stepper motor and the vertical movement is a geared DC motor so I'll flip the unit around here and this is what the back of your Jurassic Park or anyone that you might play in an arcade looks like minus this lamp board here let's look at each part of the T-Rex assembly so starting at the top we have our stepper motor under this heat shield here directly to the right here is the stepper motor motor controller board uh this is what drives the stepper motor underneath that down here is our serial motor driver board which controls this uh geared motor right here uh this driver board is to allow the motor to spin clockwise and counterclockwise uh so the T-Rex can move up and down so now that we have a basic overview of the two major systems let's see how these function in the test menu our test bed here is just like your pinball game just compact and without a playfield so I've got menu buttons here like would be on your coin door so to get into the movement tests we are going to go into our diagnostic menu here and let us work the horizontal test first so the T-Rex she just raised herself to the upper position and then then went left came back found home went right came back found home and then swung left and right so now on the screen here we have a representation of switch number 68 which means about center um so when we move the T-Rex to the left to the right you'll see that that switch will be struck and that is kind of how the stepper motor knows once it's reached a center reference point a stepper motor in software it knows let's use an arbitrary number we need to step 60 steps to the left and it's going to find that center switch and go okay 60 steps this way and then in software it might be called to go right again so it needs it knows it needs to go 60 steps to find home and then another 60 steps to find its rightmost travel so now that we've seen what horizontal movement looks like from the front let's flip the back panel around so we can see what that mechanism looks like from behind when the cam turns there is a point on the cam that makes contact with this micro switch here and that is our uh home or our reference center point when the mechanism is called to move left and right I have a totally undressed T-Rex assembly here so this is the entire assembly without any of its stage dressing right the actual model and this is a good view of the linkage in the armature that actually turns the T-Rex left and right give you bottom view as well so as it moves the output shaft cam pushes on this drive arm which then articulates the entire neck all right now that we've seen the horizontal movement let's take a look at vertical movement so there's the T-Rex again centering itself it is bringing it into plane um as we see here on this LCD screen now that we're in this test we have representations of each uh vertical position that the T-Rex can be called into so you've got your uh lowest position this is the position the T-Rex will take when you're starting like T-Rex multiball or a T-Rex encounter where she'll come down and uh open her mouth and grab the ball but then it can come up to a middle position and a top position so this is all done using a geared DC motor and it is positioned with three micro switches as we see here let's flip it around and you can see how that is done so now that we've got the test fixture turned around let's familiarize ourself with the vertical movement equipment we have our serial motor driver board down here we've got the motor that it drives here we've got our output cam and then three micro switches here and then the uh driving rod that rotates the T-Rex up and down so when we call the T-Rex to move the motor uh will spin until it stops each of these limit switches one being down one being the middle position and one being the upper position so as I mentioned in the beginning where we familiarized ourself with the equipment uh we're using a serial motor driver board to run the T-Rex motor clockwise and counterclockwise this allows the motor to be reversed so it can reach each of those three positions if you weren't using a driver board that allowed for clockwise or counterclockwise rotation you would be forced to have a motor that only spins in one of those directions so this allows it to reach or change those positions a lot more elegantly uh than a single direction motor here we have a uh some action of the motor output here so we've got the T-Rex in her lowest position the center position and the upper position so if you notice each time the motor stops it is um resting on the micro switch that correlates with that stopping position and this is how the game knows once the T-Rex has reached each of those positions you can see here is that driving rod uh this is what is attached to the cam on the motor so when the motor changes position the T-Rex will raise up and down in some cases it might be necessary to adjust the height of the T-Rex when the T-Rex needs to catch the ball the jaw needs to be just above the ramp so how might you do that there's a small amount of adjustability here on this motor plate if we were to loosen these nuts there is a u channel cut into this plate which allows us to be able to to grab the motor and position that higher or lower uh since the T-Rex pivot is fixed a slight amount of movement up or down here will change the maximum up and down position vertical position of the T-Rex's head so if you ever needed to adjust the jaw of the T-Rex a little closer or maybe a little bit further up from the ramp those adjustments would be done using these nuts here so now that we've looked at at the vertical and horizontal movement we can look at the opening and closing of the jaw and the catching of the ball so let's talk about the opening and closing of the jaw that is done by a small solenoid inside the head when the solenoid is energized it will attract this plunger here that is attached to this sled there's two pins on either side of the sled that are attached to the jaw when the coil energizes and the plunger for the sled is energized it pushes the top of the jaw forward and levers it open and then the spring on the plunger against the solenoid will force it back to a closed state when the solenoid is no longer energized so I'm can simulate the solenoid being energized here when we look inside the jaw we can see that there's a relay coil that acts as a magnet spoiler alert in Jurassic Park premium when you start some of the T-Rex events the T-Rex will be lowered down with the jaw open and when you shoot up the ramp this magnet inside will be energized waiting for the ball you shoot the ball up the ramp into the mouth and the magnet will catch the ball then the T-Rex assembly can close the jaw when the jaw is closed the ball's actually captured when you get some of the fun chomping animations the magnet will energize which will allow the jaw to open and close to make it look like the T-Rex is chomping on the ball the last thing we have inside the T-Rex's jaw is an opto sensor the optos allow the game to know when there is something in the T-Rex's mouth with the jaw closed the beam from the transmitter mates up with the receiver uh the game knows that the jaw is now closed with nothing in it when the jaw opens it will actually break that beam but the game you know does know that the jaw is open at that point if we have a ball inside and the jaw is closed the beam is now broken so the game knows that the T-Rex does have something in its mouth so now let's take a look at the T-Rex assembly when the playfield is in its forward service position or how you would most likely service your T-Rex assembly I have the lockdown bar and the glass removed from the pinball game so to access we will lift up the playfield pull it forward and rest it on the service rails and from this angle here while a bit cramped you have access to every portion of what we were looking at on our test fixture I hope you've enjoyed taking a look at one of the most intricate assemblies we've put into a pinball game and thank you for watching another video from Stern tech school _(Acquisition: youtube_auto_sub, Enrichment: v3)_ --- *Exported from Journalist Tool on 2026-04-13 | Item ID: f9d5f7f6-e85f-4dda-af13-65e77949ea72*