Freakynami's [Virtual] build...

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goochie
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Re: Freakynami's [Virtual] build...

Postby goochie » 22 Aug 2016, 16:04

Possibly a bit early to consider but have you looked at CFD for the model? I've recently started looking at some options and this seems like a viable free option:

http://www.openfoam.com/products/visualcfd.php

I'm particularly interested in ways to reduce wind disturbance in the cabin.

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freakynami
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Re: Freakynami's [Virtual] build...

Postby freakynami » 25 Aug 2016, 00:47

I have very limited experience with CFD.

I know enough about CAE in general to know that I will never get anything significant from spending any amount of time down that rabbit hole. From watching Dennis' experiences with it, if you spend the time to generate a really good model, and back it up with a tonne or real world testing, then you can get some real world benefit. Even at his "grass roots" level (compared to F1, no disrespect intended), he is still an order of magnitude further up the learning curve than myself.

I reckon with a real finished car and some cardboard I'll get better answers much faster. I also don't imagine much time will be spent off public roads, so don't imagine any reduced comfort to be too much of a problem to me. That may change, but hey, I can always reskin the chassis into a fully enclosed coupe if I want to later on :)

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Re: Freakynami's [Virtual] build...

Postby ShadowCat38 » 27 Sep 2016, 10:40

freakynami wrote:... I'm thinking white chassis with blue highlights...


Excellent choice! And I'm glad we're on different continents, because that is exactly the same color layup I've been planning for my build. It'd be completely embarrassing if we both showed up with the same looking completely custom car. :roll: *kidding*

Honestly, I love that color selection, and seeing yours modeled up in color will go a long way to helping me fine-tune the details I'm interested in.

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Re: Freakynami's [Virtual] build...

Postby dpkilty » 24 Jan 2017, 09:19

Andre, I know you've posted somewhere on this forum about how you did the assembly in Solidworks, but I can't for the life of me remember where that was. Did you do the main chassis as one weldment drawing or did you do sub assemblies? My work computer (Lenovo laptop that's 3+ years old) isn't the best for Solidworks anyway but its doing odd things when I try to edit the main chassis weldment. I have the entire chassis as one weldment file with a bunch of 3D sketches, and I'm wondering if its just too much and I need to break things down into sub assemblies. I am having the same kinds of issues as if I have a large assembly with lots of parts. Slow, jerky panning/scrolling/zooming and rebuild errors on mates for no reason.

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Re: Freakynami's [Virtual] build...

Postby Midlana1 » 24 Jan 2017, 09:46

dpkilty wrote:Andre, I know you've posted somewhere on this forum about how you did the assembly in Solidworks, but I can't for the life of me remember where that was...

It's at the start of this very thread.

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Re: Freakynami's [Virtual] build...

Postby freakynami » 24 Jan 2017, 19:03

I ended up not using weldments.

I found a thread from another Aussie builder (Phil) where we discussed it: http://www.midlana.com/forum/viewtopic.php?f=5&t=734

But yeah, long story short, I gave up on weldments, here is the structure of what worked for me:

- Start off with a single part file as a "skeleton". This has one sketch for the floor tubes (2D), one sketch for the roll bar (2D), then several 3D sketches for "Front end", "Rear end" etc.

- Then I made a bunch of separate part files for each individual tube, named in accordance with the tube numbers from the book. I made these a couple of inches longer in each case than the measurement from the sketch.

- Then I made a "chassis assembly" model. Into that I placed the skeleton sketch. Then I assembled each tube, mating it to it's sketch element. Finally, I made all of the cuts / notches as assembly cuts.

- Then I made a new assembly, placed the chassis assembly into it, and added all of the "brackets".

- Then I made a new assembly, placed the "chassis with brackets" assembly into it, and added the panelling.

- Then I made a new assembly, placed the "chassis with panels" assembly into it, and added everything else.
Each of the components added to this top level is in a tree folder such as "interior trim", "rear suspension" etc. so I can suppress most of the car and unsuppress just the system I'm working on at the time.

The way above means a lot of back and forth throughout the hierarchy - like adding the handbrake lever at the top level needs a bracket at the bracket level, but it means I can see the whole chassis at the different built states to observe when two brackets may be near each other, and come up with a way to make them into one bracket etc.

As to having the whole car open at once, it's not pretty, slow and jerky like you say. I also tend to make little "study" assemblies off to the side, for example the front suspension at full droop, full compression and nominal for both sides of the front of the car at one time ends up with a zillion components. But that assy is saved off to the side so I can later on check clearance to headlights etc. very quickly and easily.

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Re: Freakynami's [Virtual] build...

Postby dpkilty » 25 Jan 2017, 03:04

Thanks.

I'll likely have to switch up to something similar to what you are doing. I like the "auto updates" of using 3D sketches for weldments but that is one of the things that is killing me. I had planned on making a bunch of subassemblies similar to you for the suspension, brackets, and such so I'm glad to hear I was going down the right path there.

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Re: Freakynami's [Virtual] build...

Postby Midlana1 » 25 Jan 2017, 06:28

As much as I loth Google Sketchup, I did the same, using many layers of the design. Draw the part, that's one, use it in a subassembly, that's two, in the main subassembly, that's three, use it in the overall car assembly, that's four. It helps prevent things from getting complicated and confusing, and REALLY simplifies making changes.

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Re: Freakynami's [Virtual] build...

Postby dpkilty » 25 Jan 2017, 07:01

Layer control or subassemblies are always a good idea on complex assemblies.
In previous jobs, I've drawn progressive dies to punch holes and form metal parts. Doing them in Autocad they were 2d and usually had upwards of 45-50 layers. Each part was its own layer. You learn real quick how to manipulate layers or subassemblies and use them to your advantage.

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Re: Freakynami's [Virtual] build...

Postby freakynami » 28 Jan 2017, 00:31

A somewhat meaningless pretty picture:

FVB114_1.png


But what it does tell me if I believe it, is that from having the over engine diagonal and getting a number of "26,287Nmm/deg", then deleting the diagonal that number dropped to "26,053Nmm/deg", so a 0.9% reduction. I can live with that.

If I remember, when I do the torsion test (and get real honest answers rather than this mumbo jumbo), I'll add a clamped on brace across and see what the real-world change is.
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