Bog's Paddleduck Engine

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bogstandard:
Very nicely done Kvom, I had forgotten I had used the RT, but you soon cured it by finding the centre in the vice.
Doing it this way saves all the hassle of setting up in the 4 jaw.

Bogs

sbwhart:
Well done that Man :clap: :clap:

That six jaw chuck looks an andy beast :thumbup:

Stew

kvom:
Today I fabricated the other eccentric using the threaded rod. It went much faster, about an hour start to finish.

I then went through the book noting the dimensions, calculating the 1.5x dimensions and writing them on the pages, and comparing these to the brass material I have on hand. It seems I either have pieces that are too small, much too big, or else I need to make a part to fit another part that gets made first.

However I do have a number of pieces of 1/4" thick brass sheet that was originally 3" wide. Since I now had the eccentrics made it seemed logical to make the straps next. I found two pieces that were reasonably close to the top and bottom sections, squared the sides on the mill, measured each with the height gauge to calculate how much needed to be milled off, and then milled both to the calculated size.

The only point of interest to a reader might be this "technique" for clamping a part in the mill that is thinner than your parallels:

These hardened precise cylinders are also useful in ensuring proper clamping when the surface against the moveable jaw is not flat.

Once both pieces were sized and precisely squared, I drilled the holes for the screws. I am using 6-32 screws. Once the top piece was drilled and tapped, and the mounting surfaces deburred, I screwed the two tightly together and camped in the vise in order to bore the hole.

The diameter of the groove in the eccentrics is ~.830, so I wasn't going to be able to find a "lucky fit" drill bit as Bogs did. So after edge finding to locate the center of the bore, I center drilled and drilled through with the 1/2" drill bit. Then I remembered that I have a .75" end mill, and used this to enlarge the hole further. Then I had to resort to the boring head to reach the final dimension. I recently acquired a set of bore gauges, and these were immensely useful in measuring the bore with the piece still in the vise. I used Bogs' tolerance of .05mm, which is ~.002.

Next I used a 1/2" endmill to reduce the thickness of the strap (still screwed together) to fit the width of the groove in the eccentric, taking equal amounts on both sides. This also cleaned up the surface on the sides.

When assembled onto the eccentric it turned, albeit stiffly. Some lapping and run-in should take care of the fit (I hope).

Then I reclamped the top portion in the vise to drill the holes for the coupling. It seems that 3/16" rod would be a bit too big, so I drilled it 5/32. Then drilling the oil hole completed the day's shop activity. Here's the result of about 5 hour's work:

Brass_Machine:
On your way sir!

I want to do this one... hell, my list keeps getting longer and longer!

Eric

kvom:
I went through the book and made a list of all the parts, compiling them into a spreadsheet. Here's the results. Useful as a checklist:

   Parts List for Bogstandard Paddleduck Engine

Part   Qty   Dimensions   "Page #"

"Main Block"   1   54x32x18   3
Top Cap   2   18x2.5+   11
Packing Gland   2   18x8   11
Packing Gland Adjusting screw   2   8x8   11
Piston   2   10x5   12
Crosshead   2   27x22x16   12
Piston Rod   2   3x10   12
Top Plate   1   64x50   16
Crosshead Guide Bars   2   4x39   18
Bearing Block   4   20x15x10   19
Baseplate   1   110x50   22
Crankwebs   4   28x5   24
Flywheel   1   32x10   24
Eccentric   2   18x10   30
Support Columns   4   6x10.5   32
Support Pin (if needed)   6   4x12   32
Connecting Rod   2   35x6.5x6.5   32
Steam Chest   2   40x18x16   35
Steam Chest Blanking Plate   2   32x18x2   42
Spool Valve   2   6x45   48
Eccentric Strap Bottom   2   21x10   53
Eccentric Strap Top   2   21x15   53
Eccentric Coupling Block   2   10x6x4   53
Eccentric Coupling Fork   2   6x4x4   53
Piston Valve Packing Gland   2   12x9   55
Piston Valve Screw   2   8x8   55
Steam Flange   4   12x6   57
Steam Flange Base   4   12x4   58
Steam Control Block   1   25x25x10   65
Steam Control Spool   1   10x23   70
Steam Control Bottom Plate   1   22x7   70
Steam Control Top Plate   1   22x10   70
Steam Control Arm   1   26x7x5   70
Lubricator Body   1   15x30   73
Lubricator Top   1   15x14   73
Lubricator Screw Cap   1   8x8+   73

74 parts in all. I didn't include rods, tubing, or fasteners that don't require fabrication other than cutting to length.

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