I added 16 pictures of the new version to the end of the original post. The finished Cab Forward runs much better than a new Rivarossi Cab Forward. Even without adding additional weight the drawbar almost doubled.
The shell fits much better too, with the new brass frame it only needs the top center screw to secure the shell because of the better alignment from the new frame.
I plan on making brass frames for all of my Cab Forwards and AC-9s. This project took a total of 10 hours and $4 for the brass to make a perfect running Cab Forward, not including the dual Canon EN22 motors. I found 20 EN22 motors at $1.19 each about 8 years ago, should have bought 40 at that price.
I updated my CAD drawing to lower the front drive wheels to the correct position. My original drawing has the drive wheels .053" closer to the bottom of the boiler than the original Rivarossi. The corrected drawing is at the bottom of this post with a link to my Google Drive full size PDF.
Over the years I have remotored over a dozen Rivarossi Cab Forwards and created several posts on remotoring them. This post is a new angle on remotoring. After thinking about the dual Canon EN22 motor Cab Forward modification I had an idea bonk me on the head, "Why not make a new frame to fit the two Canon motors?" I decided to do my thing on my CAD to see if it was easily doable.
I began by making a drawing of a Rivarossi Cab Forward "out of the box".
After about three days of dinking around off and on drawing several versions I came up with a scheme that I thought should be rather easy to do.
The picture above is a preliminary concept to see if it was a doable project.
After three or four days playing around with several versions the drawing above is the one I liked the best. The inline shaft alignment should result in better efficiently with less mechanical problems. After I drew up all the components to scale it was simple to move things around on the drawing.
By using K&S Brass Strips there is very little cutting. The motor shaft alignment recess is easily accomplished by using .062" thick brass strips, three layers equal .186" and the shaft recess needed for alignment is .184". Because of the curvature of the boiler in the Rivarossi shell the bottom brass strip works out to ½" wide by 4 7/16" long. The second layer also needs to be ½" wide by only 1½" long, the top two strips are ¾" wide by 1½" long. The wider top sections will give a larger working area for the Rivarossi gearbox.
After cutting the brass strips to size I used vice-grip pliers to hold the various pieces together to drill and tap holes so that I could keep them inline for soldering. I used a 150 watt soldering iron to solder the brass then a sharp metal file to trim it up into a nice looking frame.
I have finished the brass frame and installed it in the Cab Forward shell and test run it with it's tender and both run terrific, very smooth with no wobble.
The picture above shows the brass frame in the shell wired to DCC specs. In this version I'm going to install the 1.4 volt regulator in the tender with the sound decoder. I'm going to use the green wire on pin 3 of the NMRA connector for the Marker lights to turn them on and off with DCC Function 3.
I will add more to this post after I complete the wiring and add 8 ounces of lead bird shot to the boiler for added traction.
Added August 10, 2014
This dual motor conversion of a Rivarossi Cab Forward works so much better than the original that I'm going to make a second brass frame to experiment with. The locomotive runs so unbelievably good I'm going to replace the frame in one of my kitbashed AC-9s also.
Added August 15, 2014
After several hours of testing both a Cab Forward and a AC-9 using my home brew dual Canon EN22 motor brass frames I have come to the conclusion that dual motors with inline motor to gearbox alignment does away with all of the "Rivarossi Wobble". Both run extremely smooth without any wobble. I'm currently installing my third dual motor brass frame in a Rivarossi Cab Forward.
Updated CAD drawing January 14, 2018
This is a more accurate drawing of the Brass Frame. The front Rivarossi trunnion mount on the original drawing was .053" higher than with the original Rivarossi frame. The detent corrects the error to +.01".
A actual scale size PDF is available on my Google Drive, click here.
Updated Brass Frame January 23, 2018
The following pictures are the new version of the brass frame with the modification to lower the front driver assembly mounting bracket. My original brass frame was off by .053".
A few pictures of other things I did to complete the Cab Forward.
The Rivarossi Cab Forward ladders are part of the headlight mounting bracket. I used Athearn Caboose ladders to make the Cab Forward ladders. I attached the ladders to the Rivarossi shell so that the grab irons don't have to be removed to remove the shell. Now the shell can easily be removed with one boiler screw.