TOPPER PROGRESS UPDATE! Prettier, lighter, stronger.
I ended up rebuilding this model completely today. This is 100% NURBS surfaces, and is about 80% of what I want it to be... which is just about right, considering where the product is at, lifecycle wise.
In all of the mini-galleries below, the new part is shown in blue-silver; the old model is gold.
The most noticeable change is in the bottom/rear of the lofted middle portion. I added a few rails to guide the outer surface, and worked to blend the loft more with the clamp body - and the barrel.
The front of the part looks pretty similar, but the bulge in the back is now gone, and a number of the transitional surfaces are more fully blended.
I also optimized the window shape a bit in order to reduce stress in the corners.
But the bigger changes are on the interior surfaces. There, I created fully tapered faces, which distribute material just where it's needed. The resulting structure is lighter and less prone to failure. It's a bit hard to see, but the new part has an arc-shaped inner wall on the top right, and the bottom left wall of the lofted transitional portion has a completely different - and much improved, I think - shape.
You'll also notice that I removed the little ledge around the perimeter of the inner diameter of the part. It was originally intended to be a hard stop for the seatmast to bottom out on, but I was able to eliminate it - while retaining the core function - but moving the window's bottom edge to the same plane.
The result is much more organic, and distributes strain more evenly around the part. I'm not totally done fine-tuning it, but the initial FEA results are promising.
As you can see, the corners of the lower section are stronger now, and strain there is more evenly distributed. And because of the way I rebuilt the model, it shouldn't be too hard to beef up the necessary portions a bit.
Although I'd like to take another shot at some of the loft geometry, I've been thinking ahead a little too. I suspect that the clamp portion can be relieved a bit, and have been playing with some shapes... I rather like the result :)