Chris's Diesbar Engine Build

[crueby]

I dug around in the tool chest and found a jig for the rotary table that will work out perfectly. It has a post on the bottom that fits in the center hole in the rotary table to align it, and a pair of T-slot clamps to hold it to the table. The hole for the center post extends up through the top of the plate, so another screw can go down in to hold the part centered. I made a pair of brass bushings to fit the holes in the crank webs, each with a close fit hole on a 10-32 screw. Clamped the parts on with one end in the jig center hole, and used the other end hole as a drill guide to drill/tap that end. That holds the part securely with one end centered, reversing the part lets me do the other end too. Those two smaller screws off on the left end are there from holding some other part on aother project.

So, used that setup to mill the ends of the pump webs round - the crank pin end is smaller than the main crankshaft end, and the sides are tangent to the two arcs.

Here it is with the first one done

Did the same cuts on the other web, then moved on to milling the longer cylinder webs the same way.

Once all the ends are done, I'll set up with a ball end mill to trim around the raised sections at the ends, then with a corner rounding end mill to ease the corners where needed. Also, the center section of one pair gets taken in farther to match the webs at one end of the real crankshaft. Lots more to go on these...

[cnr6400]

 

[Michael S.]

Hi Paul,

There isn't a special connection like that on this engine.
My understanding is that the crank is guided through a bronze bushing, which allows for a bit of play. Chris is going to mount a flange on the crankshaft—on both the starboard and port sides—of his model. However, the *Diesbar* engine didn't have anything like that.

Michael

[crueby]

Hi Michael, actually the crankshaft does have what appears to be the flange I am using, its on the outside of the bearing at either end. I had just seen it in some of the videos online, and its here in your video as well. I think that instead of a flange, its where they thin the shaft down on its way out to the paddlewheel, but I am using it as a stop flange! It will keep the shaft in proper alignment for the model. Without taking the real engine apart. In one of the pictures you sent me taken during maintenance, with the bearing cap removed, it shows a slot turned into the crankshaft that the bearing surrounds, which will accomplish the same thing, holding the shaft side to side.
Here is where the shaft thins down outside the bearing:

and here is how the real engine did it. This picture was taken with the bearing cap removed, showing the slot in the shaft:

I could have done the same thing on the model, but turning such a long shaft on my little Sherline is not easy, especially since I would need to do it with the webs installed to get the alignment just right.

Also, your explanation of the connection in the web with a bushing explains something else that I had not understood: why there is an oil cup on the end of the crank pin at that connection. That would oil the bushing. Learning a LOT during this build!
 

[crueby]

And, just AFTER making the cuts on the crank webs (pictures later), where I included how the web at the one end has a slightly different shape, I was looking back at your video of the real engine. Saw that it is JUST the outer web on that end that has a different shape. I cut both webs for that end the same...      

Elf-Pucky!   Too late to remake just the one web, would need to remake both webs for that end to get the alignment proper, and I don't think I will bother with that. I'll leave that as a puzzle for future curators to figure out!   

[Sanjay F]

You've left a mystery for the future, no one will ever know and we won't tell anyone ..........honestly the whole thing looks stunning I think most observers will appreciate the workmanship overall and not even notice! 

[crueby]

You've left a mystery for the future, no one will ever know and we won't tell anyone ..........honestly the whole thing looks stunning I think most observers will appreciate the workmanship overall and not even notice! 

Thanks  Sanjay!   

[crueby]

I was doing some more shaping on the webs, and was about to cut the radius on the corners of the pump crank webs, when I went back to the pictures to double-check at which points the radius stops/starts. Thats when I realized that the original does not have a radius, its a flat bevel!

Have to use a different cutter for that! Also noted the raised lip around the crank pin. Need to think on that one - might be best done by adding a thin disc there rather than trying to shap it in the existing webs...       
One thing that WILL be slightly different on the model is that I will have a slightly raised hub around the main crank shaft, where on the original it is flush with the shaft. Doing that on the model would require making the main shaft in two pieces, which I don't want to do. So, that will be another slight variation from the original.   Shhhh... don't tell anyone...   

[cnr6400]

  I think your engine is modeled as it was on the day before that outer web mod...  

[crueby]

I think your engine is modeled as it was on the day before that outer web mod...

Well, nope. I have one pair of outer webs with the extra shape, one pair without, there SHOULD have only been one web of the four...   

[crueby]

And as I mentioned in the last couple posts, here is the next couple steps in the shaping of the webs. In this picture, the sides have been taken in:

and then went around the outer edges of the two extensions around the holes with a ball end mill to form the fillet:

One other thing I had mentioned was to do some experiments to get the guarantee lettering into the pump crank webs. Its too fine to mill in, I don't think electro-etching would work well on the 303 stainless to etch in the letters, but I did an experiment with the masking film that would be used to electro-etch parts. I've done that on a number of tiny nameplates to make raised letters. I got out some of the leftover pieces of the PNP-Blue masking film that were used on previous models, and picked a partial page of nameplates from the steering engine (another project with help from Michael). The PNP-Blue is meant to do PCB board masking, you print a reverse image on one side (better get the proper side!) of the sheet with a toner-based printer, then use a clothes iron to transfer the toner onto the PCB board (or a sheet of thin brass or copper for the models). The iron has to heat up the metal and the masking film, so it takes several minutes on high for this test on a 1" square piece of 303 stainless. After ironing, you run the piece under cold water to quench it and harden the transfered toner/blue mask, then peel off the masking film, leaving the image behind. Here is what I got from that experiment:

Not too bad, considering the surface was a raw piece of steel with no cleaning or polishing. The toner is black, but the letters come up blue since it takes that layer from the masking film. The smaller letters on the nameplate were 9 point font, which is pretty close to what I would need for the guarantee letters - I am thinking either 6, 7 or 8 point font would be needed, will experiment with printing that on plain paper to get it sized properly. I am thinking that doing the letters this way would work, and spraying over them with some clear lacquer would keep them from rubbing off - will experiment with that on this test block to be sure. Not quite the same as engraving them in, but darn close!   

[crueby]

Oh, and if a transfer does not come out well with the masking film, it can be rubbed off with steel wool and another attempt made. And since the transfer paper should only go through the printer once, it makes sense to put a lot of replicas on the page when printing in case that is needed!

[Kim]

That's going to be quite the cool detail! 

Kim

[crueby]

Thanks  Kim!  Early  this evening I  gave the test piece a spray with some clear lacquer  to see how well it protects and if there was any bad reaction  with the transfer. Just took a look, and was pleased to see that for some reason the blue from the masking material is  gone, now just the black of the toner! I'll  wait till tomorrow so its fully cured to test rubbing on it, but it holds up great on nameplates so should be fine for that. Since it now shows the toner color, I want to try it with red lettering like on the real one.  Think I'll  figure out what font size and font matches the real one, and make up a page of pnp-blue, half black and half red, for further tests.

[Michael S.]

Chris, that’s a great idea to handle the crankshaft lettering this way.
I’ve jotted down the exact wording again because the "K" and "H" aren't stamped very clearly. The spelling of the word *Gussstahl* is interesting; around 1853, it was written with three "s"s. Later, we used the *eszett* ("ß")—*Gußstahl*—but nowadays, following spelling reforms, using three "s"s is perfectly acceptable again.
The phrase "Krupp bei Essen"—meaning "Krupp near the city of Essen"—is also interesting. Back then, Friedrich Krupp’s factory was located just outside the city. Today, the entire area and all its cities have merged together; the whole Ruhr region, as it’s known, feels to me like one vast industrial city.

Michael