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Adding the Center Rail to my MSA
After adding some extra pulls to pedals 1&2 in order to raise the low B to C# on the 12th and
the G# to A on the 11th string, I noticed that the flex of the cross shafts was far too much!
Even without these extra pulls the cross shaft's flexing should have been less to my opinion.
With the center rail added, I measured a pitch increment of more than 40 cents when raising
the B's to C# with pedal 1. (I checked this before adding the extra pull and adjusting anything)
In fact this proves that on a double neck body there should be a center support for the cross shafts.
With a center support rail, the needed pedal travel will be less and it saves the cross shaft bearings
from wearing down faster.
So I decided it was about time to add a center rail. But how to get the exact position for the holes
where the cross shafts should run through. I did not want to disassemble the instrument completely.
Also having only a professional drilling machine available, this would mean that even with the most
accurate measuring of the hole positions from the rear support rail and copying them onto the new
center rail, it would be very hard or almost impossible to get it within acceptable tolerances.
All bearing holes should be in line with the ones on the front and rear rails in order to have the
cross shafts rotate freely.
The solution is to drill the holes to a little larger diameter then the outer diameter of the bearings.
Before assembling of new rail to the guitar, having the rear rail and every part on the shafts between
the rear and center removed, the center bearings should be added first with the collars towards the
front of the instrument. Otherwise they will not fit into the holes, because the part of the rail that will
be fixed to the body with the screws, has a thickness of 5 mm. Too big to fit between the collars
and body. Then the new center rail can be slid onto the cros shafts and fixed to the body as shown
on the pictures. Then put all removed parts back onto the shafts and finally the rear rail back into place.
With the cross shafts being supported by the front and rear rail, the center bearings can be moved
into the slightly too large holes. With a sufficient amount of epoxy resin to fill up the gap between
the bearing and the hole carefully applicated to the outside, the bearing can be moved into place
meanwhile turning it around the cross shaft.
This way the resin will spread easier and more equally into the gap.
While holding the bearing into place, any excessive resin must be carefully removed.
After the epoxy resin has been cured completely, the bearing will be fixed very precise and
the cross shafts will rotate perfectly. Flexing will now be reduced to a minimum.
Other advantages of the center rail are slightly reduced cabinet drop because of the added strength
of the instrument and the option to hold the extra knee lever which I also added.
The rail has been made of an aluminum L-shape of 50x30x5 millimeter