Basic setup for the 15mm rail skater dolly
The whole idea behind this project is not to build the cheapest or the most versatile skater dolly, these projects are already refined by many filmmaking community members around the internet. My intention is to use the parts of a rig that many already have in their bag to add the skater dolly functionality and also, by keeping things small, provide a solution for travel.
- A baseplate set.Â For this setup I used a DSLR baseplate from ebay. The series name is FOTGA DP500 but anyone will do I suppose.
- Â A pair of DIY Rail Mounts. These where bought from D Focus (http://dfocussystem.com/diy.php) for another project but they were left in the box. The main thing is to use a rain mount that offers a straight surface on one side and the tightening screw in the middle, this way the screw will act an axis for the wheel base.
- Â An ALU hinge profile. I bought mine from a large DIY store and cut it to 6cm long pieces (2 of them) with a hole drilled in the middle of the flat part. This hole should be close enough to the cylinder part of the profile so the head of the polygonal screw that passes through will stop rotating.
- Â Some spacers. I used those in order to stop the Rail Mount bending and transfer the force of the screw to tightening the wheelbase.
- An M8 long screw. I cut the rod in two 18cm pieces to act as axles for the skate wheels.
- M8 safety nuts. I used safety nuts, the ones with the plastic bit at the ends that prevents unscrewing from the rotating skate wheels.
- 4 cheap skate wheels with bearings. I got a set from amazon.
The assembly is quite simple you use the camera baseplate in the middle to hold the two rods and the two DIY rail mounts at the ends to hold the wheelbase.
I found that it is better to add some kind of anti-skid material (like rubber) between the bottom of the rail mounts and the aluminum profile to keep the wheels pointing to the desired direction. This is especially important if you add the stepper motor since the torque makes the wheelbase shift a bit. The whole construction is not always level by that I mean that the 4 wheels do not always form a single plane. You can correct this by loosening the mount of the baseplate to allow the rods to slide, then you apply a little torsion to the ends of the dolly to make the wheels level and then re-tighten the baseplate mount. This is the setup for adding the skate wheels to a 15mm rig.
Â Adding the stepper motor and the motion controller.
- Arduino based Mini E motion controller
- Nema 17 sized 12V stepper motor
- 12V Rechargeable Li-po Battery 6800mAh
- Flat rail mount
- MXL Pulley, 48 T, 8mm Bore
- MXL Pulley, 20 T, 6mm Bore
- Bore Reducer, 5mm bore, 6mm OD x 20mm long
- MXL Rubber Timing Belt, 110 T
The second part of the project is how to add a motion controlled timelapse capability to the skater dolly. The heart of the system is an arduino based controller called Mini E.
It is a very well thought out controller, simple to build and with a lot of community support. All instructions for the controller part can be found at http://openmoco.org/user-interface/minie-2×16-ui-and-minimal-engineÂ unfortunately the thread is full of spam at this time, I hope an administrator clears it at some point. You can also find the whole Mini E project at sourceforge http://openmoco.svn.sourceforge.net/viewvc/openmoco/miniE/trunk/miniE/ with full instructions and diagrams. I used a shutter cable for Nikon D5100 from an older timer remote control. The only thing I added was the various connections and the enclosure that is basically an electrical cable box from a DIY store. The power for the controller unit comes from a 12V Rechargeable Li-po Battery 6800mAh from ebay that is attached with Velcro outside the box. The whole controller unit is screwed on the tripod mount part of the baseplate and is attached to the dolly.
The stepper motor is a NEM 17 form factor 12V like this http://www.sparkfun.com/products/9238. The rail mount comes from the infamous mattebox/shade that was called the fisher-price mattebox . I bought that following the advice of Darren Levine, since the whole thing was cheaper that a rail block alone. The good thing with this mount is the large flat surface and the way it tightens. I attached a small plastic bit (cut from a plastic box) on the motor with two M3 screws and made a cutout where the mount screw is.
I positioned the plastic bit inside the gap of the mount and used a bare allen screw instead of the thumb screw of the mount. This makes room for the timing belt from the motor to the wheel. In the tests I also used a tie to secure the motor on the rail mount I suppose that there is a more elegant way but I wanted to carry on rather than wait for the perfect solution.
The timing belt and pulleys were bought from https://www.motionco.co.uk/ and they are MXL size category. The pulley attached to the skate wheel must have an 8mm bore in order to fit well over the wheel axis, the size of it is relative to the skater wheel you use. For the motor you need a bore reducer from 6mm to 5mm and then a 6mm bore pulley. For my dolly the timing belt size was 110 teeth but this is relative to the whole construction.
Finally I used a ball head to rise the camera and I think that is all…
Thank you for reading, and thanks to the community for all the inspiration.
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