Bay State DL-109 Restoration Project

[SWrailroader]

Jim, Thank you for continuing to post. I have learned a lot from this thread.
Rob

[R.K. Maroon]

I am going to install ball bearings in the journals of the DL-109s in an effort to reduce running friction and thus gear load. I might not be so inclined, but the first unit had gone through at least two axle worm gears before it came to me, so I am hoping that ball bearings will help reduce the friction load on the gears (and thus buy some margin on gear tooth loading). It's a bit of an experiment, but if it doesn't work, I can remove the ball bearings, plug the holes, and re-drill for friction journals.

The sideframes are rigid. There is a way to assemble the truck so that they will equalize when set on the rail. This means that the two sideframes do not have to be perfect aligned to each other as-assembled. Further, if the trucks were two-axle, then alignment of the bearing bores on each sideframe would not be much to worry about either. As it is, the DL-109 has three-axle trucks, so it is very important to line up all three bearings in a straight line. To do that, I have made a support jig as follows:

Step one was to bolt a suitable piece of wood to the mill table:



Step two: drill a shallow hole the exact size of the sideframe-to-bolster mounting hole. Put that size drill in the hole and run the mill table in the x-direction only, adjusting the swing angle of the sideframe until the drill bit in the mill aligns with the second sideframe mounting hole. Drill a hole into the wood at that location:



The idea is to align the sideframe so that the bearing bores, once milled, are on the same alignment as the mounting holes.

Step three: Mark the wood in the places where relief is needed for the journal boxes, springs, and brake cylinders:



Step four: Mill these pockets out:



When done, the sideframe will sit flush to the wood:



The holes for the drill bits were made shallow to leave material for hold-down screws to bite. If I have been sufficiently careful, and if the original journals were similarly located, then the existing journal holes should be aligned with the x-axis of the mill. I will report back.

Jim

[up148]

That is some great work and lots of thought and common sense went into your jig. You make it look easy, but like so many jobs you need to think it through to eliminates as many gothcas as you can before the work commenced. I've done very few jobs (so far) with the drill press Bob told me about, but stabilizing the material seems to be just about the most important consideration......your jig does that in aces.

[R.K. Maroon]

The main purpose of the jig discussed in my last post was to provide a solid base to hold the sideframes while boring out the journals for ball bearings. As a bonus, I was hoping by carefully aligning it on the mill table that the existing journal holes would line up with the x-axis of the mill. This would allow me to bore the new holes in a straight line by just moving the x-axis table. I was please to report that this worked, at least on the first sideframe, as this composite image shows:



So I was thinking I had smooth sailing from this point: Just insert my new pilot counterbore into the mill and cut metal. To my surprise, the bronze sideframe proved to be a worthy opponent to the high-speed steel counterbore. I was able to get the holes bored, but it was slow go. Here is another composite photo, showing the holes as bored on top and with the bearings inserted below:



I have twenty-one more holes to bore. I'm going to acquire a carbide end-mill to (hopefully) speed things up.

For those not familiar with a pilot counterbore, it's a nifty device that picks up the existing hole, ensuring concentricity with the counter bore. Here is a generic photo:



The item I have has a sliding pilot. That is convenient for this application, as I can let the pilot drop all the way to the bottom of the existing journal hole (as that gives best alignment) and then cut the counterbore without having to remove or shorten the pilot.

[up148]

Interesting tool/bit that I never knew existed, but certainly makes a lot of sense for this task.

[R.K. Maroon]

A question came in regarding the source for the pilot counterbore. I bought mine from drillsandcutters.com. It is listed as a pilot hole counterbore, I guess to differentiate it from a counterbore with a fixed pilot. Here is the photo from the listing:



The pilot shaft is not shown in the photo, which I am guessing is generic. Also not shown is the set screw in the shank that can be used to fix the pilot if desired. The particular tool I bought is at the link below:

https://drillsandcutters.com/3-16-x-3-32-pilot-hole-hss-straight-shank-counterbore/

I did a little research into machining bronze. It turns out that there are several common grades of bronze, one of which (aluminum bronze) is very hard. This bronze is tricky to mill and very abrasive. A coated carbide end mill is recommended. I will acquire one and give that a try. As an aside, the notion that some bronzes are very abrasive jives with this situation (posted many years ago) in which a steel axle is found worn down by the bronze bearing it rode in:



The things one learns when fooling with doorstops...

[bob turner]

I have seen steel worn down in good porous bronze bearings. We routinely replaced both bearings and axles on the club MTH Diesels. Funny thing - the bronze bearings were the same size as the control hinge bearings on a Piper Cub.

[up148]

I've seen bronze bearing but had no idea they were so hard. Obvioulsy bronze swords and weapons from the Bronze age were a lot tougher than I ever knew or gave them credit for.