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BrendaEM · 02-18-23, 01:45 AM

(Updated)

For Haha's, I made a piston model (1st photo) in Rhino 3D. It's based on the U-Boat U-505 sub museum (3rd photo).
The German engine museum from the video above, wrote me back : ) They stated that the piston was a whopping 260mm in diameter, which makes the piston roughly a meter in length.

* Piston top is unclear in the drawings, done was added to top of piston.
* The flange/washer thing that holds the wrist-pin (gudgeon-pin) in is polygon-hungry, because the flatter of the areas is actually bend to match the piston radius. The original part appears stamped steel.
* Unlike a real-piston there is no gap on top/bottom of the rings in the model. This could save mesh complexity.

A U-Boat engine blueprint, with my piston drawing over it (rings would be compressed in cylinder):

A rendering 3D modeled piston. Boards are about 4" wide, like you would have on a deck. Piston is huge!:

The piston is pretty strange, in that the wrist-pin has a bolt and nuts holding it together--instead of C-Clips. I am unsure if they had distorted thread locknuts back then, such as Stover Nuts. It would be bad if the thing loosened up in the cylinder.
The piston is still huge. They must have had a special place for a spare.

I did a test in CAD. If the piston could have been removed from the bottom, then perhaps the notches on the piston crown would help the piston clear the lower part of the cylinder liner. The access panels on the side of the motor are pretty big. I had read that they could do a piston replacement at sea, but I have not yet read whether or not the head would have to have been removed or not. If they head had to be removed, that would be a major undertaking. But if the piston could be unbolted with a spanner, and sneaked out through the access port, then it wouldn't be so bad. Most pistons have their bolts on the bottom of the connecting rod, and perhaps the spanner nut would have allowed the connecting rod to be removed from the panel. The blueprint does not give a good indication of the stroke, which would let the position of the crank big-end be known. So it looks like the piston could be removed--if the connecting-rod would clear the crank.

02-18-23, 01:45 AM	#9
BrendaEM Mate Join Date: Aug 2022 Posts: 56 Downloads: 0 Uploads: 0	(Updated) For Haha's, I made a piston model (1st photo) in Rhino 3D. It's based on the U-Boat U-505 sub museum (3rd photo). The German engine museum from the video above, wrote me back : ) They stated that the piston was a whopping 260mm in diameter, which makes the piston roughly a meter in length. * Piston top is unclear in the drawings, done was added to top of piston. * The flange/washer thing that holds the wrist-pin (gudgeon-pin) in is polygon-hungry, because the flatter of the areas is actually bend to match the piston radius. The original part appears stamped steel. * Unlike a real-piston there is no gap on top/bottom of the rings in the model. This could save mesh complexity. A U-Boat engine blueprint, with my piston drawing over it (rings would be compressed in cylinder): A rendering 3D modeled piston. Boards are about 4" wide, like you would have on a deck. Piston is huge!: The piston is pretty strange, in that the wrist-pin has a bolt and nuts holding it together--instead of C-Clips. I am unsure if they had distorted thread locknuts back then, such as Stover Nuts. It would be bad if the thing loosened up in the cylinder. The piston is still huge. They must have had a special place for a spare. I did a test in CAD. If the piston could have been removed from the bottom, then perhaps the notches on the piston crown would help the piston clear the lower part of the cylinder liner. The access panels on the side of the motor are pretty big. I had read that they could do a piston replacement at sea, but I have not yet read whether or not the head would have to have been removed or not. If they head had to be removed, that would be a major undertaking. But if the piston could be unbolted with a spanner, and sneaked out through the access port, then it wouldn't be so bad. Most pistons have their bolts on the bottom of the connecting rod, and perhaps the spanner nut would have allowed the connecting rod to be removed from the panel. The blueprint does not give a good indication of the stroke, which would let the position of the crank big-end be known. So it looks like the piston could be removed--if the connecting-rod would clear the crank. Last edited by BrendaEM; 02-19-23 at 01:38 AM.