3/4-inch scale B&O P7d Cincinnatian

[Bill Shields]

I made a rectangular punch to make the holes for mine...drivers, leading and trailing trucks. Biggest pita is that if you unload the suspension, the keepers fall out. I eventually crimped all in place so that they will not fall out. Maybe not prototypical. .but practical.

The top leaves are curved so that even if you lift the chassis up in the air there will still be a load on the linkage to keep all in place.

Punch did not hold up well -> But managed to make the number of holes I needed...and not much more. Still have it 40+ years later

[Andy R]

Hi Bill,

I made a rectangular punch for the springs on my big-boiler Virginia, but split about 90% of the holes punched.
For this loco, the only rectangular holes needed were for the hangers on the lead truck; all the others are round holes.
For those rectangular holes I made long ovals by drilling (carbide bit) a pair of holes then milled between the holes.

I cut the springs to length with this tool, borrowed from a friend:

It is "The Handnib" by National Machine Tool Co. of Racine, Wisc.
It has a base that can be either bolted to the desktop or held in a vise (as I did.)
My friend made a table extension and a threaded stop that made cutting the leaves to length easy.

After I drilled the leaves for the remaining holes another friend gave me a Whitney-Jensen Punch No.5 Jr., made in Rockford, Ill. I have been using it to punch the Delrin AF spacers, and a few 0.015-in. spring leaves that i have had to re-make when discovered on assembly.

Yes, spacers. I did as you suggested and recalculated the springs, and the difference between using the original design and doubling the thickness is significant. I finished the spring assemblies for the trailing truck and have some more work still to do to finish the driver springs.

Regards,
Andy

[Bill Shields]

the trick that I used to get the punch to work without splitting was to angle the face of the punch like a guillotine....one end punches through the rectangular hole before is slices through to the other end...I do not try to punch the entire hole at once.

pretty low tech but it worked....

I cut my leaves by:

scribe with a scratch awl to see where they need to be cut
zip through them with a cut-off wheel (like in a dremel)
put in a block and sand the end to position on a belt sander

again...very black smith but got me to the finish line...

[Andy R]

The spring assemblies have been completed, as discussed in the previous posts.
Some work was still needed to finish the trailing truck frame:

The trailing truck is equalized to the main frame, so it makes sense to complete it before rigging the springs on the main frame.

This week the axle-boxes are being completed.
After that assembly should be relatively easy because I made the brake hangers last year.

[Andy R]

While I was busy working on the springs a good friend visited, and he wanted to help. He explicitly offered to trim the 5-in. boiler tube.
Considering that (a) he has a lot larger equipment than me and (b) he is a superb machinist, he went home with my carefully preserved 5.125-in OD copper pipe.
He not only trimmed the tube to length within 0.001 inch of the plans, but asked enough questions that i changed the design of mounting of the three safety valves from a very complicated bronze fabrication, to three holes into which eventually will be silver-soldered round bronze bushes. This is the lovely result:

Comparing with the drawing below, that decision saved both of us a lot of work - no rectangular opening in the tube.
There is a rectangular(ish) slot for the throat plate.
I even now have some nice fixtures for holding the boiler tube.
It is so nice to have friends!

[Bill Shields]

I tend to solder the bushing into place with nothing more than a center pop.

After soldering, the entire boiler goes into the mill to have the holes drilled and tapped.

Nothing worse looking than a wonky safety..

[Andy R]

Bill,
You wrote that you "...tend to solder the bushing into place with nothing more than a center pop."
That is a very good point.
I do too (now) after realizing that also saves on making plugs for the initial hydrotest.
On my last boiler i drilled and tapped all the bushes before completing silver-soldering and found that the threads oxidized so much that i eventually needed to increase the size of all of them. Never again.
Regards,
Andy

[Andy R]

In a previous post from today I indicated that my good friend cut the boiler tube, so of course the remainder was accurately trimmed for the smokebox. More questions followed.

On Coventry’s drawing 700-120, there is a note: “For Boiler See Drg No 153C – 716 revised.” I have Ted McJannett's boiler drawings, 705, 706, and 706A, but not Mr. Coventry's 716. I asked Dave Dalton, who sent copies of the actual B&O smokebox drawings, and an accurate description of the dimensions. Dave noted that McJannett's 705 is an update to Coventry's 716. THANKS DAVE !

There is a hole dimensioned on the port side that was not clear, and it was not used on Doug Alkire’s 1-inchscale model. Dave sent the attached photo:

image_2022-02-09_082506.png (191.07 KiB) Viewed 5893 times

That mystery hole on the port side is for the roundhouse blower quick attachment (Barco) - Dave added the arrow pointing it out. The hole on Drawing 168B appears to be at smoke box center level and the "real McCoy" was farther down. So I re-drew the smokebox with additional dimensions derived from the McJanett-Coventry drawings, and the following is the result:

You may notice that there are a lot of holes drilled for rivets. Neither the McJanett nor Coventry drawings were clear, but the info Dave sent was invaluable.
He asked “Since for a streamlined version you will be covering the smoke box and cover with sheet metal, why would it matter?"
I figured that as long as the tooling was made and the smokebox held in the rotary table for the other holes, "Why Not?" It will be a simple task to add brass escutcheon pins for the rivets.

Having more fun than usually allowed!
Regards,
Andy

[Bill Shields]

Hold the stack on with the screw on petticoat from the inside.

This way it is easy to get off and get inside to clean.
.rivets or bolts are all fakes...if you want to even bother.

[Berkman]

interesting the prototype pic doesnt appear to have drifting valves

[Bill Shields]

they are there...just not see in the pictures.

[Berkman]

are they there?