Steam Engine and Pump - Noob's first project (Work In Progress)

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Cpl_Detritus
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby Cpl_Detritus » Wed May 08, 2019 10:28 pm

I think it is a bug, especially if you are modeling surfaces.

For example in the sweep below you would expect the program to produce four surfaces all equal. Instead it produces five surfaces. This is guaranteed to cause many problems in subsequent modeling. This is only a very basic example and the problem only gets more serious as your designs get more complicated.

Loft.png
Loft.png (56.58 KiB) Viewed 264 times
chrisb
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby chrisb » Thu May 09, 2019 12:01 am

I see what you mean, but that still doesn't qualify the current behaviour as a bug. It has five faces, so what? Beyond that: although it may be possible to hide the seams, I am very sure that removing them from the construction will be near to impossible, as I guess they come from the geometric OCC kernel.
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Cpl_Detritus
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby Cpl_Detritus » Thu May 09, 2019 12:45 am

I don't think this is a minor quirk, It is a major bug. What is worse is that it is a highly visible bug that causes many experienced users to stay away from the program. Believe me you want these people onboard. These are people who could potentially contribute code to this project. These are people who can get FreeCad adopted in the companies they work in. If companies start adopting FreeCad that could be a major revenue stream to the programmers here.

I have personally recommended this program to engineers and the simple response I get is "I am not investing 10000 engineer hours into this just to find out that my model is sick." It is literally giving engineers and educators cold feet and keeping them away from the program.

I understand that the problem might be fundamental and not easily fixable. This can only mean that fixing it early would be much easier than fixing it later.
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kkremitzki
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby kkremitzki » Thu May 09, 2019 1:13 am

Interestingly the 5 face behavior isn't there if you attach one of the sketches to a datum plane that's rotated 45 degrees so that the seam line from the circle lines up with a corner of the square. See attached example.
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bejant
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby bejant » Thu May 09, 2019 1:57 am

Cpl_Detritus wrote:
Wed May 08, 2019 8:49 pm
This is a steam engine driven water pump that I think was mainly intended as a student exercise.

There are several design inconsistencies and bad design decisions that would have made this an impractical engine even back in the steam era.

It should serve as a nice first project to learn different aspects of FreeCAD.

Hi Cpl_Detritus and welcome! Would you post a link or let me know where to where you got that book or the images? Looks like a nice model you've created and it seems you're off to a great start!
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Cpl_Detritus
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby Cpl_Detritus » Thu May 09, 2019 2:47 am

bejant wrote:
Thu May 09, 2019 1:57 am
Hi Cpl_Detritus and welcome! Would you post a link or let me know where to where you got that book or the images? Looks like a nice model you've created and it seems you're off to a great start!
Here is the original forum I found these on. https://www.model-engineer.co.uk/forums ... ?th=125576 No idea if there is an original book these come from or what else might be in it. I would certainly be most interested if anybody finds out anything more about them.

Here is a personal site with a few more similar plans http://www.replicaplans.com/MuncasterSt ... Plans.html
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bejant
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Re: Steam Engine and Pump - Noob's first project (Work In Progress)

Postby bejant » Thu May 09, 2019 9:47 pm

Thanks for the links (and for your model)!