Light-rail for mass transit was brought to my city in 1985. At that time there was plenty of infrastructure in place already, so much of the track is either tunneled or on an elevated guideway. When the new transit system was introduced, it was so futuristic. Almost the entire system is computer-controlled, eliminating the ticket vendor, door men and even the conductor. Who knew the ultramodern future would be so impersonal?
They even thought up a neat way to automate the door closure safety by using a pressure-sensitive strip along the edge of the door, ensuring no one gets their arms caught in the doors and lopped of at the elbow at the first approaching tunnel. Bummer, some people ruin all the fun.
Luckily, the door safety mechanism can be overcome easily enough to allow for a camera to be located outside the train and take some unique footage.
This mount uses the doors to hold a camera outside of the train without interfering with the pressure-sensitive safety-strip on the doors. The mount is physically stuck when the doors are closed and requires the doors to open in order to be released.
Here's a video:
This instructable is for information purposes only and should not be replicated.
Tampering with private property is an offense.
Overcoming safety devices on public transit is an offense.
Projectiles or objects affixed to fast moving vehicles poses a potentially fatal hazard.
DO NOT ATTEMPT.
Enough talk...train camera!
Step 1: Tools + Materials
Step 2: A Word on Door Types
Most light-rail train doors have a rubberized strip along the closing face which prohibits the doors closing if something gets squished between. If the rubber is depressed while closing the doors are halted and reopened for a few seconds so that the obstruction can be removed, then the doors cycle the closing sequence again attempting to close without an object being caught.
To have something outside the doors will mean this mount will need to be thin enough not to be detected.
Also, the rubberized strip on one door side has a bend to it which corresponds to a bend on the opposite door. The bend maximizes the contact area of the rubberized surface and stops people from sticking things through the doors once closed. This is another safety feature deterring the urge to stick things through the doors while closing.
Since this assembly is outside, the mount design needs to be slender enough to fit through, but strong enough to support the weight of the camera and the forces acting upon it.
Step 3: Foil Imprint
Bending the putty knife on the train is too conspicuous, and taking a portion of the rubber home is impractical. Instead, take an imprint of the bend and replicate it at your leisure.
To do this, take aluminum foil and fold it over 3-4 times to create a strip, about the size and thickness of a piece of soft chewing gum. This piece should be weak enough to take an imprint of the door bend, but strong enough to retain the shape after the imprint so you can trace it out.
With your strip at the ready, wait for the doors to begin to close and stick the foil into the rubberized strip, ensure that the strip pokes out the other side for a complete imprint. Wait for the train to come to a stop at the next station and carefully remove the strip when the doors open, preserving the imprint.
Next, trace the curve of the door bend imprint to paper. To lessen the odds of distortion the imprint was traced twice on a sheet of paper. The foil was then flattened and a second imprint was taken and copied down again. This allows for any minor distortion to be found once traced and rectified when bending the putty knife.
Step 4: Bend
Meanwhile, back at the lab....
Using the trace from your imprint as a guide, bend the putty knife into the shape of the door bend. This bend can be achieved with two adjustable vice-grips. The putty knife is designed to take some abuse, bending may require some force. Use care when bending, as the knife metal can stress and begin to tear or snap.
Make sure to refer to your trace often to ensure the bend mimics the door.
This bending took about 30 minutes.
Step 5: Drill, Cut and Bend
Once the bend was complete it was time to drill an opening for the 1/4"-20 camera mount screw (I think camera mounting is universally Imperial, but are common enough in a metric country), and make a cut to allow for a final bend for the camera platform.
The location and platform size will vary depending on the type of camera intended for use in this rig. Remember the camera body will need to be clear of the closing doors, and the lens has to clear the knife blade after being bent.
The measurements below worked for the camera shown (casio EXILM EX-Z1080), but can easily be adapted to work with most digital cameras.
The camera will need to be mechanically fastened to the mount to ensure it's not lost during filming. Since the camera mount is Imperial, I used a 1/4" metal drill bit to bore through the putty knife. If you're using metric, look for a 6.35 mm bit.
You can step up to a slightly larger bit if desired, just use a washer to account for the additional bore when attaching your camera.
Drill the opening about 15mm x 15mm from the corner (5/8" x 5/8" is fine).
To make a platform for the camera to sit on there needs to be one more bend.
Measure back about 38mm (1.5") from the end of the knife, using a hacksaw cut through stop just after halfway. The cut should be parallel to the knife end.
Using the vice grips, bend a 90º angle in the portion just cut.
Be mindful to which way to bend the platform. The pressure-sensitive safety rubber on train doors are bent to fit together, making this device operable in one orientation only (i.e. if you want footage shot with the train going forward and your device only fits through the door with the camera facing backwards, your only option is to flip the camera mount upside down or try the door on the opposite side of the train).
Since most trains are bi-directional and have stations on both sides the option to use both doors is ample, it may not matter which direction you bend.
Step 6: Deburr and Mount
When satisfied with the shape, deburr the opening and edges. Then, take an emery cloth and smooth out the edges. Masking-tape bumpers were added to the corners after, just in case.
Test mount the camera, ensure the lens has an unobstructed view and the body is out of the way of where the doors close.
Remove camera and try the mount alone in the doors to see if you got the bend right. Usually the rubber sensor is forgiving and will allow for some variation in your bend.
It's best to be very familiar with the stations you are trying this between as consecutive stations may not open doors on same side as your mount.
Here's a compilation of some footage:
This simple camera mount allowed for some unique footage to be filmed, at an angle not achievable from shooting inside the train. This camera mount will work on most newer light-rail transit systems, as they commonly share a similar rubberized strip for the doors as described here.
Whether you ride the GO Train, BART, SkyTrain, or The Tube, you're on track to get some great shots to share with your friends.
Safety measures and devices in public transit are intended to keep you and others safe.
Augmenting, or defeating safety devices poses a serious life-safety risk.
This instructable is for informational purposes only. Do not attempt.