09/07/2008
| ATLAS SD35 BOLSTER CONVERSION |
Atlas teased Southern Railway modelers when they released their SD35 model. It was an SD35, but
not prototype for the Southern Railway. It was missing the appropriate truck side frames. It was
highly unlikely that Atlas would tool these side frames either. Now I am not a Southern modeler at
all, but my very good friend Bob Harpe is. Bob emailed me not to long ago and asked if I would help
him. He explained his desire to mount Kato SD40 trucks under an Atlas SD35 in order to properly
build a Southern unit. I had no idea what it might take, so I told Bob to send me the parts and I
would see what I could do. I received the parts on a Friday and by Sunday I had everything done. It
was actually a pretty easy task. Well, easy if you have the right tools. This is a short article on how I
built new bolsters.
The first thing I needed to do was figure out the height differences between the two bolsters.
Luckily for me, I had a few Kato SD40's on hand. After measuring and remeasuring and doing some
fit up tests, I came up with the magic number of 0.149". The measurement is from the bottom of the
existing Atlas bolster pad to the bottom of where the new bolster pad would have to be. This will
give about a 0.006" to 0.007" clearance of the frame to the top of the truck bolster detail. Once I
knew how tall I needed to make the new bolster pad, I started the design.
Looking at the two trucks, the designs are very different. The Atlas truck sets the bolster up high
and the Kato truck sets the bolster low. It was apparent that the existing bolster had to go, but I
could not just go ahead and cut it out. I had to be smart about this design. I left it in to help me keep
the new bolster properly positioned and to also give me a guide for the bolster pin. The photo will
do most of the explaining for me.
not prototype for the Southern Railway. It was missing the appropriate truck side frames. It was
highly unlikely that Atlas would tool these side frames either. Now I am not a Southern modeler at
all, but my very good friend Bob Harpe is. Bob emailed me not to long ago and asked if I would help
him. He explained his desire to mount Kato SD40 trucks under an Atlas SD35 in order to properly
build a Southern unit. I had no idea what it might take, so I told Bob to send me the parts and I
would see what I could do. I received the parts on a Friday and by Sunday I had everything done. It
was actually a pretty easy task. Well, easy if you have the right tools. This is a short article on how I
built new bolsters.
The first thing I needed to do was figure out the height differences between the two bolsters.
Luckily for me, I had a few Kato SD40's on hand. After measuring and remeasuring and doing some
fit up tests, I came up with the magic number of 0.149". The measurement is from the bottom of the
existing Atlas bolster pad to the bottom of where the new bolster pad would have to be. This will
give about a 0.006" to 0.007" clearance of the frame to the top of the truck bolster detail. Once I
knew how tall I needed to make the new bolster pad, I started the design.
Looking at the two trucks, the designs are very different. The Atlas truck sets the bolster up high
and the Kato truck sets the bolster low. It was apparent that the existing bolster had to go, but I
could not just go ahead and cut it out. I had to be smart about this design. I left it in to help me keep
the new bolster properly positioned and to also give me a guide for the bolster pin. The photo will
do most of the explaining for me.
What you see here is the completed new bolster pad. The part is cut from aluminum and the bolster
pin is turned brass and press fit into the bolster pad. It sticks up the same height as the bolster pin
on the Kato frame. The thickness of the pad is the same as that on the Kato frame as well. The
extensions on each end will abut the bottom of the existing Atlas bolster pad and the entire part will
fit between the Atlas frame rails.
pin is turned brass and press fit into the bolster pad. It sticks up the same height as the bolster pin
on the Kato frame. The thickness of the pad is the same as that on the Kato frame as well. The
extensions on each end will abut the bottom of the existing Atlas bolster pad and the entire part will
fit between the Atlas frame rails.
Here you can see the new bolster is installed in the frame. Note how the angle meets the Atlas
frame even across the bottom. I wanted to blend the new bolster pad to the frame. I measured the
bolster contact width on the Kato truck and made the new bolster the same. You can also see the
Atlas bolster is still there.
frame even across the bottom. I wanted to blend the new bolster pad to the frame. I measured the
bolster contact width on the Kato truck and made the new bolster the same. You can also see the
Atlas bolster is still there.
The new bolster is still not yet permanently attached to the frame. What I am showing here is how I
cut the Atlas bolster just back to the new bolster pad tabs on each side. I then removed the new
bolster and grit blast the frame to remove the paint. Paint removal can also be done by scraping it
with a knife or chisel. Removing the paint is important to give a good clean gluing surface.
cut the Atlas bolster just back to the new bolster pad tabs on each side. I then removed the new
bolster and grit blast the frame to remove the paint. Paint removal can also be done by scraping it
with a knife or chisel. Removing the paint is important to give a good clean gluing surface.
Now the new bolster is glued in place. I simply used some ZAP-A-GAP. Everything is done and ready
for paint.
for paint.
Now we al know that a normal setup is to have the drive shaft in line with the motor. This
conversion does not allow that. Here you can see the installation of the Kato truck and how it
affects the drive line.
The truck is not the correct style. This one uses high mounted brake cylinders. That is what I had on
hand at the time. Bob does have the correct trucks. Notice the drive shaft, it is not the Kato drive
shaft. The worm gear and drive shaft are from the Atlas SD35. The worm gear fits just fine in the
Kato gear tower. The worm gear clip IS the Kato clip. The Atlas clip will not fit the Kato gear tower.
The trucks swivel without any obstructions. Also there is a slight bit of play in the truck just like the
original. Side to side and up and down. Just enough movement to allow it to track properly.
conversion does not allow that. Here you can see the installation of the Kato truck and how it
affects the drive line.
The truck is not the correct style. This one uses high mounted brake cylinders. That is what I had on
hand at the time. Bob does have the correct trucks. Notice the drive shaft, it is not the Kato drive
shaft. The worm gear and drive shaft are from the Atlas SD35. The worm gear fits just fine in the
Kato gear tower. The worm gear clip IS the Kato clip. The Atlas clip will not fit the Kato gear tower.
The trucks swivel without any obstructions. Also there is a slight bit of play in the truck just like the
original. Side to side and up and down. Just enough movement to allow it to track properly.
And her is the final view just showing how it all looks assembled. There is no interference problems
with the step wells. Everything fits and operates as it should.
Just a small note. This part may become available in very limited quantities. I'll post on my FOR SALE
page if they do.
with the step wells. Everything fits and operates as it should.
Just a small note. This part may become available in very limited quantities. I'll post on my FOR SALE
page if they do.
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