This mounting system attaches the twin flash heads of the Canon MT-24EX macro flash to your lens' tripod collar using 1/2" Loc-Line tubing to form the arms.
This allows a connection that is rigid enough that it'll stay exactly where you put it, but is also easy to adjust to put your flash exactly where you need it.
One of the main goals of this design is to limit the degrees of freedom of the system. I got fed up with third-party flash arms which would twist and loosen on their mount just when you didn't want them to, and allowed the flash heads to spin on their ballhead mounts too. This design uses anti-twist mounts on both the lens and the flash ends of the connection, so that the only thing that can move is the arms themselves and the adjustment built-in to the MT-24EX. Perfect!
I've designed an anti-twist mount to suit the Sigma TS-21 lens collar. That Sigma collar is found on the following Sigma lenses:
- APO 70-200 / 2.8 EX DG OS HSM
- APO 70-200 / 2.8 EX DG MACRO HSM
- APO 70-200 / 2.8 II EX DG MACRO HSM
- APO 50-150 / 2.8 EX DC OS HSM
- APO 100-300 / 4 EX DG HSM
- APO 300 / 2.8 EX DG HSM
- MACRO APO 150 / 2.8 EX DG HSM
- MACRO APO 150 / 2.8 EX DG OS HSM
- MACRO APO 180 / 3.5 EX DG HSM
- MACRO APO 180 / 2.8 EX DG OS HSM
I've also designed a mount which fits an aftermarket replacement for the TS-21, the iShoot SM720, and this is the collar shown in most of the photos above. Because this collar has more than one screwhole on its foot, a much sturdier and more compact anti-twist design is possible.
A version of this mount with no anti-twist features could be produced that would fit on any lens foot, but trust me, this is a miserable experience. Without anti-twist features, the torque produced on the mount screw by adjusting the arms is basically guaranteed to unscrew the whole mount, which results in you having to retighten the screw over and over again while shooting in the field. Not fun at all!
The super long extension tube shown in the photos above can be seen here: https://www.thingiverse.com/thing:3761957
Extra parts required
All versions require:
- Loc-Line #51895 (1/2" Fixed Mount, pack of 2) - Loc-line, Amazon.com
- Loc-Line #51801 (5.5" length Loc-Line pack of 2) - get 2 packs - Loc-line, Amazon.com. If you need this in black you can also buy it as the Wimblerly Plamp II extension PP-222
- 1/4"-20 x 1.5" length screw (1 piece) to join the Loc-Line mounts
- 1/4"-20 hex nut (1 piece) to join the Loc-Line mounts
- 1/4"-20 x 0.5, 0.75 or 1 inch length screws (2 pieces) to attach your MT-24EX flashes to their mounts. 0.75" length preferred.
For the Sigma TS-21 you also need:
- 1/4"-20 x 1" length screw to attach the printed mount to the foot of your lens
For the iShoot SM720 you also need:
- 3/8"-16 x 1" length screw to attach the printed mount to the foot of your lens
- 1/4"-20 x 0.75" length (grub) screw for anti-twist
Imperial fasteners are a bit hard to come by here in New Zealand, so I ordered mine from Albany County Fasteners. They have a huge catalog and most of the screws are available in black oxide coating, which looks legit! Their international shipping to NZ is crazy high (USPS Flat Rate International - US$80), so I had them deliver it to a freight-forwarder instead.
Print the adapter that'll attach to your lens' foot with the following settings:
- Material: Anything, I chose Prusament Mystic Brown PLA
- Layer height: 0.2mm
- Perimeters: 2
- Supports: none
- Infill: 20% Grid
The spikes on the sides that look like the Aperture Science logo lock into the fins in the base of the Loc-Line mount to prevent it from spinning on its mount.
For the Sigma TS-21 version you may need to add a brim for proper bed adhesion (I went with 2mm). At the bottom of this print is one big bridge. I had the most success when printing the model at 75% of regular speed.
Print two cups to attach to the foot of your MT-24EX flashes with the following settings:
- Material: PLA
- Layer height: 0.1mm
- Perimeters: 2
- Supports: none
- Infill: 20% Grid
Note that the exact diameter of this print is critical: too small and there won't be enough friction to hold the mount in place, too large and the cup will be shattered during mating with the Loc-Line.
The diameter of the sphere that makes up the cup is modelled at 21.30mm, and changing this by 0.05mm is enough to make a noticeable difference. That's a scale change of around 0.2%.
Clear out the sacrificial bridge that covers the screwholes of the flash head mounts. Attach a flash head to each mount using the corresponding 1/4"-20 screw. Now snap that together with the Loc-Line arms.
For the Sigma TS-21 you also need to clear the sacrificial bridge out of the 1/4"-20 screwhole in the printed lens foot mount.
Attach the mount to your lens' tripod collar using the screws specified above. Slot the two Loc-Line fixed mounts onto it, and join them together using the 1/4"-20 1.5" screw and 1/4"-20 nut. Now snap the two Loc-Line arms onto those cups.
Note that a large amount of force is required to join Loc-Line segments together. They do sell special pliers to aid in this task if you get stuck.