This page documents the final assembly of the upstream end of the horn. Here you will find proof that we actually did install the water seals at the upstream end, and we did torque the threaded rods that hold the horn together. Things went well.

Click on any of the thumbnails to get an enlarged view. You are welcome to download any of the images. If they are used for other than private viewing, credit to Bartoszek Engineering would be appreciated.

Making the measurements needed to cut the upstream flange

The weld shrinkage of the inner conductor causes the length of the inner conductor to be unknown until it is measured at installation into the outer conductor. For this reason, the upstream flange has several features left off in its initial fabrication. We need to measure the correct depth to cut the upstream flange. One of the main reasons for assembling the horn on a rotating fixture is to allow measurements to be made with the inner conductor in both tension and compression from the weight of the upstream end. Both of these measurements are then averaged, and that value is used to cut the flange. This way, when everything is bolted tight the inner conductor should be very close to a zero axial stress state.

When the horn is rotated 180 degrees, we found that the inner conductor is about .010 inches longer in tension than it is in compression.

We had originally intended to use surveying to determine the angle of the bolt pattern on the IC with respect to the OC at the upstream end, but Danny suggested the simpler method of using transfer points screwed into the tapped holes on the IC to mark the upstream flange. This method worked like a charm.

Machining the Upstream Flange

These pictures show the upstream flange being machined. The last picture shows the water seal between the upstream flange and the IC being polished.

Cleaning the parts one last time

Installing the first aluminum water seal

It's a little tricky to see here, but it's there.

The last flight of the ceramic ring

Installing the remaining aluminum water seals

They're there too.

Installing the ceramics around the threaded rods and torqueing them up

We tightened all the .500-13 threaded rods and socket cap screws to 30 ft-lbs, per breaking tests and previous experience on the G0 collimators for UIUC.

The upstream end without and with corona balls

We changed the design of the part to lock the corona balls on the threaded rods. The design used to be roll pins but they proved too hard to install safely. Instead, we now have 8-32 cone point set screws installed in new tapped holes in the corona balls backed by 8-32 knurl point set screws to lock them. This experience has been incorporated into the target support system where there are more corona balls.

Back to the MiniBooNE Horn Main Menu

Back to the Bartoszek Engineering Home Page