Gordon,
I thought your suggestion of using the entire Proto SD7/9 truck
assembly as substitute to correct the trucks on the new Proto
Burlington SD-45 was a great idea and one that uses the "good enough"
concept.
I pulled out one of my SD-7 mechanisms to examine the truck
assemblies in detail and found as you had mentioned that Proto has
redesigned their truck assemblies so that one can not simply
substirute sideframes. A couple of items that you may want to be
aware of when you start your conversion. The worm gear on the SD-45
is longer than that on the SD-7/9 so that it will not fit into the SD-
45 gearbox with out modification. Possibilities would be to would be
to either mill down the bearing thickness or remove the worm gear
from the shaft and mill down the ends of the worm gear. The easier
approach seemed to be to simply swap out the female ends of the
plastic drive shaft assembly. Unfortunately the SD-45 metal worm
gear shaft is about 0.0015 larger in diameter than the SD-7/9 shaft.
However the SD-45 female U-joint fits the SD-7/9 (at least on mine)
sufficiently well that I don't think it will wobble or vibrate if it
is squared up sufficiently and cemented or pined to the shaft. So
far so good.
The pivot point on the SD-45 is a part of the truck assembly while on
the SD-7/9 it is a part of the frame. This could easily be fixed by
pressing a piece of brass rod into the SD-7/9 truck assembly hole.
Next I noticed that the bearing surface between the truck assembly
and the frame is about 0.036 inch (~ 3 scale inches)higher on the SD-
7/9. I haven't yet reassembled the SD-45 to see how noticeable this
will be, but I suspect that it will have to be addressed by milling
down the top bearing surface of the SD-7/9 truck assembly. The
bearing plate is only about 0.063 in thick so after milling, it may
have to be reinforced to have adequate strength to support the engine
weight.
While you are at it, I think the sideframe axle bear journals need to
be changed to the sloped top style which both Detail Associates and
Details West make. Seems like nothing is ever easy.
Good luck with your conversion. Let me know how it turns out.
Dale DeWitt
----------------------------------------------------------
--- In CBQ@yahoogroups.com, Gordon Smith <kc2bw@o...> wrote:
> I'm going to swap out the trucks with the SD7/9 trucks. I already
have two
> sets. Although the sideframe casting is not 100 % correct, the brake
> cylinders will hide the difference. I purchased complete trucks
because the
> mountings are different for the sideframes. I also picked up the
worm gear
> set in case the housing is different. The universals and drive
shaft are. So
> we'll see what happens when I get some time to tear the trucks down.
>
> Gordon
> ----- Original Message -----
>
> > I recently purchased several of the new HO scale Proto2000 SD-45s
> > including one painted in the Burlington green transition colors.
It
> > is a nice model but requires a number of detail changes to make it
> > more accurate.
> >
> > Can any one suggest how to correct the trucks from the high mount
two
> > brake cylinder version (3 shoes per side) to the high mount 3
> > cylinder version with the 6 clasp type shoes and rigging. I am
not
> > sure if the mainsideframe is the same or if it need to be
completely
> > replaced with something else. And if so, what? The sideframes on
> > the SD-7 & 9s look similar but I don't know if they are the same.
> >
> > Thanks in advance for any help.
> >
> > Dale DeWitt
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