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The BeeSpi photogate measures the instantaneous velocity of an object as it passes through the probe. To facilitate student investigations about kinematics and acceleration, I put together kits to make marble ramps out of 2020 aluminum extrusions and some 3D printed brackets.
With the links below, everything to make 10 different set ups without the BeeSpi probes can be purchased for under $200 total (less than $20 per set up!) |
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BeeSpi v Self Contained Photogate TimerThis photogate timer removes one of the biggest barriers in teaching motion: accurately measuring instantaneous velocity without complex setup or expensive interfaces. By directly measuring instantaneous velocity, BeeSpi allows classroom experiments to align with the kinematics students learn on paper, strengthening conceptual understanding and experimental confidence. The speed, precision, and simplicity of the BeeSpi turn traditionally error-prone labs into reliable, repeatable investigations, making it a rare piece of equipment that genuinely improves both instruction and student outcomes.
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2020 Aluminum ExtrusionThese work the best if they are as long as possible but they can get pricey so I would recommend whatever length over 1000 mm (1 m) is the most cost effective. I have found that 1.5 meter rails work well and fit nicely on our lab tables
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M6 Mounting ScrewsThese screws are used to mount the BeeSpi brackets and ball stopper to the 2020 aluminum extrusion. You will need 4-6 screws per set up depending on if you have 1 or 2 BeeSpi probes.
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M6 T-Slot NutsThese nuts are used to mount the BeeSpi brackets and ball stopper to the 2020 aluminum extrusion. I like these ones over other options because they have a spring ball to keep them from sliding loosely in the extrusion. You will need 4-6 T-nuts per set up depending on if you have 1 or 2 BeeSpi probes.
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Steel BallsIt's important to have a ball that is large enough to break the photogate of the BeeSpi. I've found that these 22mm steel bearings work well. They have also demonstrated a very uniform acceleration down the ramp without many losses. You will need 1 steel bearing per set up but it's a good idea to have extra in case some roll away.
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3D Printed Brackets and Stopper
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To attach the BeeSpi v to the 2020 aluminum extrusion and keep the ball from flying off the end, I designed some 3D printed adapters that use the mounting hardware detailed above. The files are posted on Maker World for free and the preprinted parts can be purchased at the links shown.
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What I like about these brackets is that if you don't tighten the screws all the way, you can pretty easily slide the probes to a new location on the rail to collect new trials. The video below shows this in action (normally it's even easier because you don't typically record it with cell phone in your other hand at the same time)
Finishing TouchesWhile the ball stopper does a pretty good job on its own, it was pretty noisy and I found that it was pretty common for the ball to bounce back up the rail after hitting. An easy fix for this is to use a bit of mounting putty stuck to the inside of the ball stopper. You probably already have something like this lying around but
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While students could measure each position individually, I found it useful to mark a line every 10 cm with a chalk marker so that students could quickly get measurements without juggling meter sticks.
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At one end of the aluminum extrusion, I used a screw and t-nut to indicate a repeatable starting position and marked that as "position zero". From this starting point, I marked every 10 cm until I ran out of rail. It was also useful to mark a line at the center point of the brackets so that the center of the BeeSpi where the velocity measurement is accurate would line up with the intended distance.