I can’t believe it’s been almost TWO months since I posted an update here! What’s worse, it’s been about that long since I’ve done anything on my Pennsy build! Oh my! What IS the world coming to?
I did, however, have a grand time getting to know my new 3D printer (I posted a short update on that over in the Additive Machining sub-forum if you’re interested in that sort of thing).
But it’s HIGH time I got back to my main project. So today, I did.
Chapter 23.3 – Formers and Backing PlatesAnd today, we start on the formidable boiler. I’m pretty excited about this, contrary to how it might seem with how long it has taken me to get to it! But I’m here now.
We start the boiler by making a bunch of wood formers. As is often the case when hardwood is required, I used maple from my old stock of wood that I originally purchased to make a cradle for our first child. I never quite got to that project, however. And my first child is now grown and on her own and probably wouldn’t fit in the cradle even if I made it. So I’m putting the wood to a different use.
I cut a bunch of blanks on the table saw to about the right size. There are four sets of formers needed, one set for each of the following:
1) Front Tube Sheet
2) Backhead
3) Firebox Sheet
4) Throat Sheet
Each set consists of a former and a backing plate.
Starting with the Front Tube Sheet former set, I drilled a 1/4” center hole in them and, using a 1/4" bolt as a mandrel, turned them round on the lathe. Then, using a 1/16” radius router bit, I rounded the sharp edge on the former. If I were to do this again I think I'd use something besides a 1/4" bolt. The 1/4" bolt didn't really provide a very straight mandrel. I'd either turn a mandrel specific for this or possibly use a larger bolt? Whatever. This worked OK. but if I actually wanted it centers on the hole I'd need to do it differently. But in this case, round is good enough - concentricity would just be for the OCD part of me. Oh yeah, and it would have helped with the 1/16" round-over. Since there was some wobble to the circle my radius wasn't very even. I ended up using a file to get it more 'even'. But that's plenty good. It just needs to be a bit of a radius there. I don't think the 1/16 has to be too exact.
At this point, I realized I should have taken a picture of the former blanks before I started working on them. Oops. But as you can probably imagine, the two on the left started off as square blanks. From left to right, they are: Front Sheet Former, Firebox Sheet Former, Backhead Former, Throat Sheet Former.
Actually, after marking them all up so nicely like that, I realized that the best way to do these would be to double-sticky-tape the pairs together so that I could form them at the same time.
So, after stick-taping them together I put them in the mill to trim to final size. This is the Firebox Sheet Former set.
Once to size I used the DRO to find the right spot for the center of the arc and drilled a hole. This will be used to center things on the rotary table in a bit.
After doing the same thing to the Backhead Former set, I moved to the Throat Sheet Former set. This set is different in that the center for the arc on this former is off the edge of the former itself. So I attached this set to a larger backing board to help center it. This was also attached with double-sticky tape. Looking at it now, I could have just made the lower former blank a half inch longer and I’d have been set. Ah well. This works too!
Now, back to the Firebox Sheet formers. After centering up the rotary table with my ever-so-cool coaxial indicator, I used a 1/4" gauge pin to center the former set over the RT. Then rounded off the end.
With that done I moved to the 1/16” round-over bit to put the radius on the former. BTW, the backing plates don’t need the rounded edges, just the former part of the set.
But I only did the rounded end on the RT. I moved back to the vise to round off the straight edges.
And that completed the Firebox Sheet Former set. I’ve still got the Backhead and the Throat Former sets to go.
But that’s all I could handle for today. So in I came to write up my exciting new update.
Thanks for checking in and sticking with me after this LONG gap in progress!
Kim
