As mentioned in a previous post, we uncovered a mounting issue during a recent maintenance session of our 3m parabolic dish. The Spid BIG-RAS rotor mounts to a piece of metal tubing at the top of the tiltable mast. At some point this tubing became deformed, causing the rotor to attach improperly. Fortunately we discovered this in time, re-tightened the bolts and made a plan to make a more permanent fix.
We decided to weld together a square flange bracket with the circular flange on the bottom part of the rotor. With this modification the square flange mounts directly to the mast via four heavy duty bolts. We believe that this attachment method is much more robust to vibrations, and is also simpler to mount.
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- LA2QUA (left) and LB7IG (right) preparing the parabole for deattachment.
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- After removing the parabole. LB5DH is seen to the right.
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- LB7IG and LA2QUA inspecting the unit for modification.
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- Removing the electronics box from the rotor.
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- The metallic tubing shows deformation from the force of the rotor bolt clamps.
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- More details on the dents seen from above.
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- Paint is sanded away to prepare for welding.
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- The circular bottom flange is spot welded from the factory.
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- The dented tubing is cut to fit inside the rotor base.
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- The circular flange rides a little on the weld that attaches the dented tubing to the square flange.
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- Some of the welding that attaches the circular tube is removed to ensure that the rotor lies flush to the square flange.
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- Since the square flange is a lot wider than the circular flange, the position of the electronics box must be changed.
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- Fortunately it is very simple to cut one side of the attachment in half, and turn it around.
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- Beautiful sparks ensue.
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- LB7IG performing the welding. The circular flange welds are reinforced with additional welding points. Then the circular flange is welded to the larger square flange.
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- The welding and angle grinding is performed at Omega Verksteds mechanical workshop.
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- The finished modification.
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- The new position of the electronics box is tilted away from the rotor by bending the metal plate.
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- Close-up of the welds.
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- Another weld glamour shot.
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- Reattaching the rotor to the mast. The flat flanges align flawlessly.
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- While we worked on the welding, the parabole managed to gather quite a lot of snow.
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- We performed the modification on the day before the storm Cora. We decided to place the parabole in a sheltered location to weather the storm.
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- On monday we set the parabole back.
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- A lot of hands were helpful, since working in the dark meant that the bolts were hard to align.
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- The welds were also painted later that night. This is done in order to prevent rust.
Thanks to Omega Verksted for lending us the use of their metal workshop, and thanks to everyone that for helping out with the heavy lifting.
With a more sturdy attachment, we are more confident that the dish will move about as expected. Now we can start attempting to receive transmissions in the 23 cm band, which we will come back to this in a later post.
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