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3D Printed Frame Isolators for Bachmann DDA40X ---
The
two Bachmann DDA40X's that I put axle gears in on the preceding page
also had missing and broken frame isolators. There are four of these
used in these locos. I designed some with Fusion 360 and printed them
with an AnyCubic Photo M3 resin printer using Siraya Tech 'Build'
Sonic Grey resin. They seem to work well but you have to modify how
they are screwed to the frame. The stock ones use self-tapping
screws. There isn't much material in these between the inner bore and
the outer circumference. If I made those dimensions the same as the
stock ones the screw would crack the resin print. I tried to make the
inner bore larger but that didn't really help the situation.
The
solution and it works as well as the stock method is to drill and tap
the inner bore for a 2-56 screw. With this method the screw is not
trying to expand the inner bore resulting in cracking and the screw
holds just as good. It takes a little bit longer to do this but there
are only four that need to be done or less if you still have some
good stock ones. I decided to not use any of the stock ones myself
and converted to these so they would all be identical.
.
First
step is to use a #50 bit and drill to about the center from one side.
Turn the piece around and drill all the way through from the other
side.
.
Take
a 2-56 tap (same as used for some coupler installs) in one hand and
hold it still. Twist the pieced in with you other hand, cutting
threads. We want to be sure we are cutting them. As the tap gets past
the tapered part of the tap it will become tight. Back it up a half
turn and go forward 3/4's of a turn repeat this and don't force the
tap. I found I had to take the tap back out a couple times and blow
the cuttings off of it. When you take it out run a screw in and see
if it will screw in to where it is hitting the end of the frame
Isolator. When it does you are finished with that side. Move to the
other end and repeat.
.
On
my prints one side of the rectangular area was bulged up a bit. You
want these surfaces flat against the frame. I took a small file and
filed that side flat. I used the file to touch up a few other small
areas of the print also. This is easy to do with the print in the tap
as you can use the tap as a handle to hold onto the print.
.
Above
are the items you need. I use the 2-56 screws, bit and tap in decoder
installs. I'll use the screws to hold solder lugs to the frame halves
at times when I need to pickup track current from the frame half to
go to the decoder.
.
You
can run the screws in tight and the frame halves are held every bit
as tight as with the stock isolators and screws.
.
.
.
Hope
these help someone as I don't think you can buy them any longer.
You
can find the print file on my thingiverse.com account (
HERE ).
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