I have been sent an AutoCad file that is basically a wireframe of a complex part for the steering gear project I’m doing for the Battleship New Jersey. The curves on the wireframe have an enormouse amount of facets. I’ve been trying to use the Sandbox “From Contours” tool, but the resuilts are often a mess with hundreds of lines that are going the wrong places and is taking an enormous amount of time. The only alternative I’ve been able to conjure up is to fill each square individually with triangles. I’ve literally been doing to for days and have almost made myself crazy when I’m cleaning stuff up and inadvertly erase finished or wireframe areas that I need. There must be another way that I’m missing. Here’s the file.
Skinning Test.skp (525.2 KB)
Here’s the entire wireframe.
Here’s a typical response after using the Sandbox From Contours. (I already removed some of the errant lines).
The Sandbox wants to connect every point to every other point, which is not what the object actually is.
This is the rudder hub as drawn by John Miano. I believe he uses Rhino to make these drawings.
This part, along with the rudder bearing, are two of the most important in the project. I may still have to modify the part to make a successful 1:32 scale 3D resin print. I had to split the bearing part into two to get it to print successfully. I may have to do that here also.
I’ve had more communication with John Miano and he suggests that I don’t try to use his wireframe to create the SketchUp model. Instead, I should trace over it and build my own SU model on top of it. That’s the only way I can control the massive number of line contact points the .dxf translator created. I’m going to do that.
On another front. Primed and painted the parts that are complete.
Here’s the Rudder Hub. The last iteration of printing in three parts (plus some fixing) worked well. The upper portion is painted red primer since this is inside the ship’s framing. The exposed part is water line (hull) red (Tamiya Dull Red Spray).
I assembled the sliding parts, masked them and painted the exposed areas.
I then painted the ram parts sky gray and its foundation light gray. I then assembled one unit to see if it would work. Looks great… doesn’t it.
But it didn’t slide at all. There is a slight unparallel condition that binds it up tight. The bearing clearances are very tight and much more tight than the resin printing process can accommodate. Part of the problem was not getting the drilled hole through the ram perfectly in the center of the diameter. With a simple drill press and none of the precision alignment tools I would use if I had an actual machine shop, I got one hole eyeballed okay, but the other was slight off the axis and this forces the crosshead slightly askew and its bearings binding.
I also broke some of the parts in trying to get them together and these just got reprinted successfully.
At this point was I a bit dejected and was ready to throw in the towel regarding animating the model. I immediately came up with plan B… a static model with an animated video showing all the motion.
This afternoon, I tried the model without the crosshead bearing liners. The ram slld nicely. If I leave out the liners, the crosshead has a lot of room to accommodate the misalignment. I am worried about the wear of resin touching stainless steel. There’s a lot of room. I will see how this works further down the line. I was just about to take the servo back to the hobby shop, when I decided to try Plan C. It will build to a beautiful static model, so Plan B is a viable option.
Stay tuned.
Milestone day: got the ram system assembled. Leaving off the brass bushings on the crosshead slides did provide enough slack so the rams slide. That said, one of them is still binding a bit mid-travel. If I can exercise it and add some lube I can still go with Plan A (animated versio). If I can’t I will go with Plan B (static model with video).
I started assembly by using some thread lock on the center post on the connecting rod spindles. This cured pretty fast and did exactly what I wanted it to do; secure in the inner race to the spindle. The other joint; the outer race to the connecting rod bores, was quite as successful with one breaking loose. I had used thin CA to secure it. This time, I used a thin film of epoxy and that did the trick. I am still worried that if one of the those joints breaks loose on the bottom rod under the cross head, it would be impossible to fix.
I had to connect all the rods before installing the units. The lower one is unaccessible after assembly.
I first tried gluing the cylinders with thick CA, but it didn’t hold well. As it was I had to break those joints because I had the pairs reversed. With the epoxy, I clamped them until cured.
I’ve drawn the high pressure hydraulic lines, but will not print them. Instead, they’re going to be bent wire. I’m also going to fab the their pipe supports out of soldered brass so they’ll be more robust. The only thing I’ll print are a few large hex-couplings that lie in the middle of the their runs.
There’s no rudder stock yet below the crank. The connecting rods are supporting the crank in the image.
I also detail painted the lower crank support frame showing the manual worm gear system and I detailed the gear box for the position indicator drive (not shown)
I’m working hours and hours attempting to draw the rudder hinge hub. I will eventually get it right. Persistence is my forte.
