TT2

My Feedback: (13)

I'm trying like heck to model a cowling for a 28% 50cc Edge 540 using MicroStation /J. I've tried using series of degenerate Coons patches but can't seem to get the surfaces smooth enough near the patch joints. Can anyone help? I'm VERY experienced in 3D solid modeling using MicroStation but my experience is limited to non-organic shapes. When it comes to b-spline based surfaces / solids I'm a moron.

My goal is to have the cowling plug CNC'd out of polyurethane foam for subsequent glassing and post-finishing to produce molds from. The cowling will be used on a plane that I'm designing and going to scratch build (if the results are satisfactory I may kit it). The rest of the solid modeling is 98% done and ready to send off to the laser cutters...my only hang-up right now is the cowling.

PLEASE HELP! I'LL HOOK YOU UP, I PROMISE!

Thanks in advance,
-Tom

cltom

Don't know enough about the issues, or the cowl shape you're trying to achieve. I've used MicroStation 3D surface modeling before the Bentleys wrote it - when it was Intergraph IGDS CAD. My experience has been to stay away from the b-splines. They're convenient to get an odd shape, but they don't convert well - if at all. Maybe that means my experience is a lot less than yours, though.

Oh - by the way - my MicroStation is only SE, but I'm not sure the J version contained any additional functionality for 3D.

HO-229

It would take many pages to explain what it is you are asking, but in breif.

I'm not familiar with the software you are using but if it has a "LOFTING", & "SECTION" command you should be able to gather your points for a CAM program.
the lofting command will create a solid from two, 2D profiles (So, the more 2D sections you have, the more realistic your 3d model will look)
Not sure if you can extract sections from a surface model but give it a try

Good luck
HO-229

cltom

Microstation doesn't really have a "lofting" command, but your suggestion about sections is good, and is often the strategy I've used. There's no magic pill - it takes a lot of work:

DELETED TO REDUCE CONFUSION *

All of this can get very complicated by the fact that MicroStation will often not recognize an extruded surface - only the plane geometry used to generate the extrusion.

DELETED TO REDUCE CONFUSION *

Like I said, I stay away from the b-splines unless there's no other way it can be done.



* I had a very long description that was not much help after thinking about it. Please look at the method below, instead. It is quite possible in MiscroStation SE, and perhaps earlier versions. You should have no problem with Mstn/J.

cltom

OK, just had another thought here after thinking about it for awhile. I'm a good Engineer, and good Engineers are lazy - we want the easy way out.

Chances are, the back of the cowl is planar. The front of the cowl is too - at least after the rounded edges of the nose. Draw the planar outline of the cowl back edge and draw the planar outline of the cowl nose. For the planar outline of the back edge, imagine that you set the cowl down on a piece of paper (nose up), and trace around the edge - that's your bottom surface. For the nose surface, pick an imaginary cross section slice where the rounded edges from the plane of the nose stop - that's your second surface. I'm assuming you know how to take a mix of lines, arcs, and curves and define them as a contiguous surface (Create Complex Shape).

Use the "Construct Skin Surface" command in the "Create Surfaces" palette to connect the two surfaces. Then build up the nose with some extrusions - revolved and extruded arcs for the rounded edges, and use the "Punch Surface" command in the "Modify Surface" palette to do the intakes. Before you do the intakes, if you need a finite thickness, simply draw a fence around the whole model and do a Scale-Copy with the Active Scale set at a percentage to create the thickness you desire. Do this before punching the hole, and all the extrusions and surfaces for the intakes will be created automatically. If you need it, cap the thickness at the back edge with another complex shape by drawing a surface on the two outlines and declaring the center section a hole. You may need to delete (or move to another level) the original two surfaces of the nose and back to open up the model from the inside.

Does this help?

HO-229

Try generating your cowling in autocad using "edgesurfing" (autoCAD) (surface modeling YUCK!!!)
Explode your edgesurf & strip off the sections that you wish to use... (this is not quick)
Make sure you have good X,Y,Z reference coordinates for all sections removed from your model, so as to be able to loft the sections into a solid model (they MUST be kept in the correct XYZ in order to develop a good model.

Good luck,
HO-229

HO-229

edgesurf...

TT2

My Feedback: (13)

OK guys, thanks A TON for the help. I had to change my plan of attack...initially I was trying to construct the cowl using too few elements. I ended up using b-splines to achieve what I wanted and the results are OK. Not perfect, but good enough...I figure that anything that's not 100% done can be corrected much quicker with a piece of sandpaper than with my mouse and keyboard! This task was particularly challenging because I wanted to have the sides of the cowling transition from the fuselage side angle instead of just being flat...I've had a few flat-sided cowlings and always thought they looked horrible. I will probably forego the CNC operations just because I don't have the time to spend on modeling / translating for CNC code...it would simply take too long. I will use the model I have and cut sections through it to enable me to create templates sandwiched between layers of extruded foam for shaping. Shouldn't take too long.

Here's what I ended up with...

(click on pictures for full size)
[link=http://home.centurytel.net/rcstuff/Edge540_50cc_cowl_top.jpg][/link]

[link=http://home.centurytel.net/rcstuff/Edge540_50cc_cowl_left.jpg][/link]

[link=http://home.centurytel.net/rcstuff/Edge540_50cc_cowl_front.jpg][/link]

[link=http://home.centurytel.net/rcstuff/Edge540_50cc_cowl_fuse.jpg][/link]


Here's what can be done easily with Microstation J. This is the forward fuselage area of my project...had to leave room for a cannister muffler so it looks overly complex, but should be very easy to assemble with laser cut parts. My criteria for this project was 50cc gasser (ZDZ or DA), in-fuse cannister muffler or tuned pipe, SUPER light (shooting for 15 lbs.), quick construction, removable tail, sized to fit into the back of my Tundra with a tonneau cover closed. I think it's going to all work out nicely.

[link=http://home.centurytel.net/rcstuff/Edge540_50cc_engbox.jpg][/link]

cltom, I can't remember whether or not SE had 'smart solids'...been a long time since I used SE. The 'smart solids' was a quantum leap in 3D modeling. It makes most 'normal' tasks childs' play.

HO-229, surface modeling...YUCK! I'd probably substitute the 'Y' for another letter. I started using Microstation over ten years ago and this is the most tedious thing I've ever had to do. A little background...I used to design piping systems for large projects...locks and dams, aircraft refueling, etc. Did that and project mgmt. for years before moving on to be a software developer (business mgmt. systems). Here's a screen shot of one of my last hydraulic projects...there were eight of these rooms on the job...all different in certain aspects. The equipment is for feeding huge hydraulic cylinders that operate the gates / culvert valves on a waterway lock (among other things). Nearly impossible to design without 3D capability...especially since most of the piping was pre-fabricated to save time and money.

[link=http://home.centurytel.net/rcstuff/manifold rack and power unit.jpg][/link]
Virtual

[link=http://home.centurytel.net/rcstuff/reality.jpg][/link]
Reality (work in progress)

Designed stuff like that for YEARS and seldom had to do any surface modeling...ah, the good old days!

Thanks again,
-Tom

cltom

Nice work - I'm a facilities engineer myself - lots of piping and ductwork. Unfortunately, I did all of it as surface modeling. No, I do not think Mstn SE has any solids capability. That was back when "MicroStation Modeler" was still an add-on package.

I'm jealous.

HO-229

It looks as if you have a handle on the modeling situation.
I know nothing of the software that you are using, but most 3D modeling software is about the same.
Most of the modeling I do is for the Navy, mostly aircraft systems Integration drawings. We do allot of electrical/mechanical design.
I’m very impressed with your work; do you send your cad files to a laser cutter?
I typically cut my own stuff out; I typically will print it out at scale & transfer the data to wood.
I’m in the process of converting to AutoDesk Inventor.
It’s not an easy move, as I have been using AutoCAD for a lond time & love it

Take care,
HO-229

TT2

My Feedback: (13)

cltom, I sent you a PM.

HO-229, laser cutting is much more affordable than it used to be. Unparalleled accuracy and the time saved justifies the money spent. For this design I plan on having the following laser cut: lite ply fuselage formers, engine box parts, wing tube / locator pin fuse side doublers (for wing and horz stab), hatch ends, root ribs (for wing and horz stab), rudder plate, tailgear plate, outer wing tube supports, AND the balsa fuselage sides since they have slots for the tabs on the formers. There will be a large amount of sheeted foam in the plane (wings, tail, hatch, rear turtledeck, belly pan) for super fast building and strength. I don't like built-up wings and ALWAYS prefer sheeted foam provided that the airframe is kept comparably light (there ARE ways)! The belly pan idea came from the Carden and Aerotech planes. The belly pans give the fuselage a MUCH better shape at the bottom than the faceted appearance that sticks yield (like the AeroWorks and Columbo Anderson planes). I can't believe that I haven't broken the sticks on the bottom of my 31% CA Extra...darned near splintered them when I was shrinking the covering...but that's about the only thing I don't like about that plane...phenominal flyer!

Transitioning to a different design platform can be a pain. I did it several times! I evaluated several high-end CAD packages and found Microstation to be the best suited for our needs. The solids modeling functions seemed much more intuitive and 'faster' than AutoCad (I think I was looking at 11 or 12...the demo seemed buggy, not laid out well, and rather difficult to use). I decided upon Microstation but the company owners kept telling me 'everyone else in the free world uses AutoCad'. True, but after the Corps of Engineers required that files on one particular job be submitted in Microstation .dgn format, I was overjoyed! In a short time I was kicking out some very 'real' 3D models of our piping projects. Saved mucho dinero on installations due to greater prefabrication and 'interference checking'. The guys in the field loved my work...saved them hours of head-scratching! Granted the MicroStation vs. AutoCad thing is all personal preference...and the opinions I give come from a dyed-in-the-wool non-conformist. ...even though I'm designing a 'me-too' Edge 540.

-Tom

HO-229

TT2,
FYI
I have recently signed up in a new forum that you may find of some interest in your modeling quest...
http://www.eng-tips.com

I have received answers to my own questions concerning the move to inventor from AutoCAD
Do a search for the software you are using, & I'll bet, someone will be able to point you in the right direction on your questions

The key I find is asking the question in the area/forum that will most likely get the correct answer

Take care,
HO-229

cltom

Yes, TT2 - I got the message. I want to respond in detail, but Thanksgiving is getting in the way.

I'm in the opposite situation - I love MicroStation, but find myself in a place where AutoCAD is the standard. Too often, the best technical solution and the more elegant implementation is not the most successful. I followed Intergraph, Jim Meadlock, and the Bentleys for years. It was an interesting family history, but both lost in the long run.

Intergraph started way before AutoCAD - back when everything had to be based on a mainframe. To save time and effort under the "terminal mode" and graphics refresh speed of the day, they developed these twin-screen behemoths for terminals. That made Intergraph famous and the "cadillac" choice in the early days. The Bentleys eventually developed a PC version of Intergraph's IGDS, and started to compete with AutoCAD, and called it MicroStation. Unfortunately, Jim Meadlock (Intergraph's founder) saw Mstn as an opportunity to sell all sorts of add-on applications (PDS?) with mainframe heritage. The Bentleys correctly saw it as an opportunity to compete directly with AutoCAD, but had little venture capital. Meadlock bought 50% ownership in MicroStation, and a love-hate relationship lasted for a few years. Meanwhile, AutoCAD got copied from the office to everyone's home PC, which created a huge user base that was never overcome. As for MicroStation, the Bentleys resented the partial ownership, and chose to compete with Intergraph instead. They started offering their own application add-ons to compete with everything Intergraph had. By this time, Intergraph ahd fashioned themselves as a mini-IBM, offering total software/hardware solutions. Unfortunately, like IBM, they became an expensive, slow moving corporation that began to lack inovation. The Bentleys finally sued Intergraph to dissolve the ownership, but it was too late to make much impact on AutoCAD's PC establishment.

TT2 - you stand as minority example of a new customer to MicroStation. Ordinarily, the Mstn customer base was made up of organizations rich enough to have invested early in the Intergraph mainframe solution. Then they progressed to Mstn to preserve the investment. Most new CAD users overwhelmingly choose AutoCAD, for the reasons described above.

Some of my old work (or at least some that I commissioned) was even on a cover of MicroStation Manager Magazine: [link=http://MicroStation Mgr - Nov 96]http://archive.msmonline.com/1996/11/index.html[/link] . There was no article, but the inside flap had this to say,

"This month's image is a view of a modern-day dogfight from a pilot's perspective. The model in the foreground is an F22. ModelVision created the model in MicroStation 95, under the supervision of Tom Blanchard, using data supplied by Lockheed Martin, the company responsible for the design and manufacture of the fighter. The model is constructed with B-spline surfaces, which allow the highest level of dimensional and visual accuracy. Apologies are due to the U.K., as the plane being targeted in the Heads-Up-Display (HUD) and "bugging out" is a British Tornado. The HUD effect was accomplished by adding a translucent layer in front of the rendering. The rendering was done by ModelVision's Bill Sabados, using MasterPiece 5.6. The processing of the high-resolution raytraced image took only six minutes using the MasterPiece raytracer on an Intergraph TD-30 workstation."

I'm the "Tom" in the paragraph. * Sigh * - those were the good old days when rendering was a big deal. If I remember correctly, I think the TD-30 used a 486 chip. I got into a little bit of trouble because of the published picture. As a CAD exercise and visual effects achievement, using the HUD display effect was neat - and ModelVision (the 3D services company) just happened to have some Tornado models they could use. Unfortunately, that was right at the time we were trying to sell the UK to become the launch customer for the C-130J. Senior management didn't take kindly to the playful reference of putting the British in the crosshairs.

Anyway, I'm in the Federal Government now, but not the Corps of Engineers, which does use USTN.

TT2

My Feedback: (13)

<<Too often, the best technical solution and the more elegant implementation is not the most successful.>>

Sad but true. Too often things become the 'standard' due to slightly different marketing techniques while the superior products fade into obscurity. Thank you for the history lesson...I never quite understood the Intergraph / Bentley relationship. I wasn't able to find any decent quality screenshots of what you had done...why don't you link some up for us?

The cover shoot certainly rattles a memory and your name certainly looks familiar. I kept all of my copies of Microstation manager...up until I left the job.

-Tom

cltom

Kind've took off for awhile during Thanksgiving. Here's some rudimentary stuff I do. I have a lot better examples - with materials, and proper lighting, etc. This is pretty representative of what I do on a normal basis, though. I also have no add-on packages, this is from scratch with the out-of-the-box program: