Another Pennsylvania A3 Switcher

After paging through Kozo's excellent book for more than a year now, and inspired by Kim https://www.modelenginemaker.com/index.php/topic,8552.0.html and Blondihacks on Youtube https://www.youtube.com/playlist?list=PLY67-4BrEae-xhrvZX33gPk4Q87S1ttae, I finally decided to take the plunge. Who knows, if I can get past the boiler, I may just finish this project one day.

I will try to follow the build sequence suggested by Kozo, and will buy materials as needed along the way. Specific materials and sizes are not always readily available, so I will have to adapt and improvise as I go along. For instance, brass will be replaced by mild steel where possible.

I do not intend to post every step of the way, but will try to make notes where I think it may perhaps benefit others (and/or myself) in future.

Every journey begins with the fist step - in this case cutting the first mild steel disk for a tender wheel:



A few days later - eight tender wheels ready to be painted:



Notes:

1. The 30 deg pointed cutting tool used to machine the wheel plate, must have sufficient side rake to clear the rim of the wheel.

2. Turn the mandrel in the sequence suggested by Kozo. First cut the thread before turning it to final size.

Great  start!  Will be watching along... 

Eight beautiful tender wheels!  What better start to the A3 Switcher project could you ask for? 

Good luck on this extended project.  I wish you all the enjoyment that I have had in tackling this project.  Have fun! 

Looking forward to reading as many updates as you care to post!
Kim

Chris and Kim, thanks for the encouragement! I may be finished before the switcher! Let's see.

Axles, bearings and journal boxes complete.





I found the use of a go/no-go plug gauge for the holes in the journal boxes, as suggested by Kozo, very helpful. Also the use of a mandrel to turn the outside of the bearing, as suggested by Blondihacks.

The journal boxes saw my first use of a 10mm carbide end-mill on mild steel on my RF-45 clone. So far I have only used HSS cutters. The higher feeds and speeds of carbide resulted in much less vibration, and hence better surface finish, compared to HSS. Not to mention the much faster progress, and hopefully significantly longer tool life. Very happy with the result.

Next in line the truck columns. This will be my first venture into the world of silver soldering...

Those look ready for assembly on the chassis   

Per           

Great start!!  And the silver soldering is a very useful skill, comes in handy on so many parts, worth doing some practice pieces to get the process down at first. 

Sorry to be late to the party here, I've been out of town for a while.

You've made good progress here. Those journal boxes look great!

I agree - the carbide end mills work great on steel.  I've mostly switched to carbide on my mill, at least for all the standard sizes. Though I still have a lot of HSS end mills and they work fine. But the carbide is much faster and better, especially on steel!

Which brings me to my next thought - looks like you're using steel instead of brass for a lot of the parts?  That's what I did, and I'm not sorry.  It has worked quite well for me.

Kim

Thanks for the comments Kim. I decided to use steel where possible, as brass in small quantities and with more or less the right dimensions are very hard to come by (and expensive!) around here. It is assuring to hear that steel worked for you.

Chris I followed your advice and practised quite a bit of silver soldering until I could get more or less repeatable results using Kozo's guidelines. After settling on a process, silver soldering the truck columns was straight forward and quite satisfying!

The process (for future reference):

1. Heat the drilled and tapped parts to remove any residual cutting fluid trapped inside the holes that will form part of the joint.
2. Clean the surfaces to be soldered with sanding paper.
3. Add punch marks to one side of the joint to ensure a sufficient (50 micron) gap.
3. Pickle the cleaned surfaces.
4. Apply flux. If the flux does not readily adhere to the metal surface, it is not clean, so pickle again. Apply flux to the screws as well.
5. Screw the parts together. Use screws of the same material as the parts to be joined. Harder screws will complicate subsequent drilling operations...
6. Do not wipe off excess flux where the silver solder will be placed. Push a piece of solder into the flux next to the joint.
7. Apply heat to the bulkier side of the joint, opposite to the solder. Keep applying heat until solder flows and fills the joint. Heat must be sufficient to complete operation within 5 minutes, to prevent flux from disappearing.
6. Allow piece to cool completely before removing any other jig screws, to avoid breaking off screws that are stuck while hot.
7. Pickle to clean the soldered joint.

The completed truck columns:

Success is always a great feeling   

Per

Excellent!  Sounds like the practice was well worth it - its a fairly easy process once you go through it a few times. One big thing I learned the hard way was that larger mass parts, and especially large copper parts, need a bigger torch to get the pieces hot enough quick enough to not burn off the flux.

Thanks Per and Chris for checking in. Silver soldering the boiler still looms somewhere in the distant future...

The truck side bars were cut from mild steel sheet using an angle grinder, and then milled to size on the mill. The mill vice was too small to hold the pieces, so a temporary vice was devised using a few lengths of cold rolled flat bar that were on hand.



The bending jigs suggested by Kozo made bending the side bars straight forward. The sharp edges of the v-slot in the jig were rounded on the belt grinder to prevent marks on the side bars.



The jig to cut the sloped slots in the bolsters was made from mild steel. To mill the 3 degree slope on one side of the jig blocks, a wooden jig was first made on the table saw with the blade set at a 3 degree angle.



Stainless steel coil spring wire was sourced from a local spring manufacturer. The coil springs were then turned on a mandrel in the lathe as described by Kozo. It took longer to select the correct gearing for the required pitch, than it took to actually make the springs.

And finally the two trucks were assembled, with all parts numbered, as suggested by Kozo!





Next step is painting, before starting with the frame. I am unsure about this. The side bars fit tight in the bearing block slots and will most likely not fit if painted first. Inserting the bolsters will however require disassembly after painting, which may also be problematic. Any advice will be appreciated.

Sorry, I seemed to have missed one of your posts in August!  You've made a lot of great progress and have some fine looking trucks there!

As for painting, I masked off the notches in the journal boxes where the arch bars fit, and of course, all of the sliding portions of the columns and bolsters.  But I painted all of the arch bars.  I didn't seem to have any problem making things fit after painting, though I may have had to sand down a little on the edges of the bars to make them fit if the paint was too thick.  I don't remember for sure, but that is certainly something I've done on this build.  I am using powder coat rather than spray paint though, and powder coating adds a bit extra thickness. If you're spray painting, I can't think that it will add enough thickness to cause you too much issue.  If so, just sand a bit off so it will fit  :embarrassed:

Wonderful looking trucks for sure!
Kim

Another great step forward - looks good 

Per         

Thanks Kim for your painting suggestions, and Per for checking in. Two months later and the trucks are finally painted! During this time I also replaced the spindle and gearbox bearings of my RF-45 clone milling machine, but the main reason why painting took so long, is procrastination - I do not particularly like painting.

I first experimented with rattle can paint, hoping for a straightforward and simple process, but could not achieve satisfactory results. In the past, I had good results with 2K automative spray paint, but this is quite a tedious process, as curing time may be 24 hours or more.

To make things a bit more attractive for myself, I first made a counter top spray booth which takes care of over spray and noxious fumes. It consists of an extractor fan from a domestic oven, some filter material and a few pieces of styrofoam taped together.





I then made an oven that reduces curing time to around 30 minutes. The oven consists of a temperature controller, two 125 W lamps and a styrofoam box.





The spray booth and oven make life much easier, especially the short curing time. Progress can now be made quickly. Suddenly painting is not so bad!

The final result:



As suggested by Kim, the edges of the bars had to be sanded down to fit into the slots of the journal boxes. This was then re-sprayed after partial assembly. The sliding interfaces between the bolsters and columns were also sanded down, and is now covered with oil. This will hopefully prevent rust. The wheel rims were sprayed with 2K clear coat.

The screws will be replaced by scale bolts to be ordered from Knupfer in Germany.

The trucks are beautiful!  Great job on the painting. 

And the paint booth & drying oven are great additions.  Love the foam construction too! Very nice!

Kim