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Where to Start?

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wishin4snow View Drop Down
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    Posted: Apr/21/2010 at 3:42pm
This is my first year of trying to complete design our car in solidworks. My big question is where to start drawing. We are planning on using a very similar suspension set-up so I am assuming that this should be my starting point. Any tips would be greatly appreciated.

Do you guys draw a person in solidworks and use that as a reference for some dimensions?
-Kevin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LongBeach_1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 3:55pm
At CSULB we always start with the firewall and either work towards the rear or the front of the car depending on the changes to the prior design.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CobraCommander Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 4:33pm
I'd suggest starting at the lower frame rails and firewall... I do have a custom template that simulates me (6' 3") with a helmet in a seated position to assist mocking the rest of the frame up.

When you get to you suspension I've found it easiest to start at the uprights and work your way in... we also have a set of our shocks modeled and i set two constraints to fully extended and fully compressed. Makes it easy.

Other than that get to it!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kenneth.mandeville Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 5:08pm
There is this guy named Todd.


he likes to go fast.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 5:25pm
Originally posted by CobraCommander CobraCommander wrote:

I'd suggest starting at the lower frame rails and firewall... I do have a custom template that simulates me (6' 3") with a helmet in a seated position to assist mocking the rest of the frame up.

When you get to you suspension I've found it easiest to start at the uprights and work your way in... we also have a set of our shocks modeled and i set two constraints to fully extended and fully compressed. Makes it easy.

Other than that get to it!


Under advanced mates you can make a distance mate with min and max values which works great for coming up with a suspension that you can cycle to it's extremes.

Like others have said I'd start from the RRH and work one way or the other.

As for a driver I've been using tweaked versions of this guys for a couple years now.  http://dpcars.net/dp1dsn/drvri.zip <- IGES
http://dpcars.net/dp1dsn/drvrs.zip <- Solidworks 2004


Edited by CLReedy21 - Apr/21/2010 at 5:26pm
-Chris Reedy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CobraCommander Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 10:06pm
Yeah, I have those set up too... But being his first year and having no knowledge of the poster's level of solidworks expertise I didn't want to complicate it.

Basically the frame I'm working on is for our 2011 car, although I am not a fan of the 3d sketches required for a single weldment or the joints produced by it. I created the entire frame as individual tubes (a naming system becomes important...) then a series of projected sketches to use for the tubing copes...

To me anyhow your result is much closer to the actual physical product even if it is slightly more complicated to set up originally.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/21/2010 at 11:08pm
I try to stick to 2D where I can, but I usually just create several sub sketches to represent parts of the car i.e. RRH, LFS, RHO, SIM each as a separate folder sometimes with more than one sketch each but compartmentalized by segments of the car.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/22/2010 at 12:45am
When I did the frame for the 2009 car, I made a big 3d sketch and did the whole thing with weldments. Its really not that bad using 3d sketch on plane. And weldments are the way to go. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote msctgb Quote  Post ReplyReply Direct Link To This Post Posted: Apr/22/2010 at 7:20pm
For me, the process is iterative enough that I end up going over everything at least a few times, usually more like a dozen+.

This year, we looked at where we could save weight, and tried to guess the final weight and distribution of the car.  After that we picked some arbitrary things (ride height, travel, firewall angle, etc.) and I immediately got to work on suspension kinematics.

I tried to design/build the frame around everything else as much as possible. After the suspension pickup points, engine and transaxle mount points, generic driver positioning, and all the rules; the frame was nearly done and only needed optimization.  That method allowed for minimal compromises in areas that we felt were more important (shock mount points, driver/engine placement for proper weight distribution, etc.)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2010 at 1:18am
FYI, it's an industry practice to keep everything in the positive frame, and to make +x pointing out the rear.  One way to do this is to put the firewall at +10 feet, which is arbitrary but keeps the furthest forward part of the car positive (so the front wheels would be around +6 ft and the rear wheels around +11 ft).  In this frame +z is up and +y is out the drivers left side.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2010 at 8:32am
If positive X is out the back, positive Y would be out the right. 

On aircraft the standard is +X (Buttline/WingStation) points out the left wing, +Y (Fuselage Station) points straight back, +Z (Waterline) is up. 0,0,0, is located on the ground, on the fuselage centerline, at some arbitrary point in space ahead of the aircraft. 

Note that the right side of the aircraft lies in the Negative X region. But always in positive Y and Z.


Edited by adrive7 - Apr/23/2010 at 8:34am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2010 at 12:07pm
Yep, Y would be right, my bad.

Depends on what you are doing.  Finite element models (that we use) are often  +x going from nose to tail.  Trajectory analysis often use +x going from tail to nose.  But regardless it's the same point to make, that [0,0,0] is an arbitrary point in space ahead of the craft so that all positions have the same sign in the axial direction.  It makes for less confusion and mistakes between designers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2010 at 1:02pm
Thanks everybody for the suggestions. I still have a few questions.
 
CobraCommander,
 I am not a fan of 3d sketches either but was wondering how you drew up your individual tubes. Is each tube its on file and they are assembled in one assembly? Or did you draw the main chassis in one drawing with sub sketches all in the same file?
 
All also wanted to know how you guys took measurements to verify that is passes the rules. I like the weldment feature but don't know how to measure from the outside of the tube like they would at tech.
 
One more thing. After watching some friends using NX, I noticed that it seemed like they had more constraint options. One especially centered the part between two different surfaces. Does Solidworks have something similiar cause I couldn't find it?
-Kevin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2010 at 1:16pm
Originally posted by wishin4snow wishin4snow wrote:

All also wanted to know how you guys took measurements to verify that is passes the rules. I like the weldment feature but don't know how to measure from the outside of the tube like they would at tech.


If you know the distance between the centerlines, and you know the OD of your tube, it should be pretty easy to figure out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2010 at 6:58pm
Thanks everyone for the help. A couple quick questions though.

I was wondering how everyone assembled their parts. Do you guys assemble all of the parts in one assembly or do you have one main assembly and multiple sub-assemblies. As of now, I was modeling the front end suspension in its own assembly.

My assemblies has been slowing my computer down as well. I have set most components to Lightweight but it is still pretty slow. Is there anything else I can do?

Also, I have been working with 3D content central's briggs model (the one with all surfaces) and it keeps giving me a build error every time I open it. There seems to be a problem with 2 of the surfaces. Any suggestions.

Thanks again


Edited by wishin4snow - Sep/27/2010 at 7:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2010 at 8:26pm
Sub-assemblies for sure. That way you can work on one system at a time. This scales to the real world, as well. Imagine trying to work on an entire airplane as one assembly. Break your vehicle down into assemblies for the various subsystems:

Chassis
Front Suspension
Front Wheel Assy
Rear Suspension
Rear Wheel Assy
Drivetrain

etc. 

It will make the model much more manageable, and it's how things are really done. 

As for that engine file, I'd suggest taking the model from 3dcontentcentral and making a solid from it. That is, use the important location info like the mounting bolts and output shaft, and the general size, and make yourself a space reservation model. A simple solid that has no real detail but contains the important pickups and is lightweight. You can leave the real model in there as well, but leave it suppressed. You can turn it on when you need it to look pretty, or check super close fits. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2010 at 1:17pm
Thanks for the help. That is how I was modeling but just wanted to see if this was right.

Now for the engine file. Do you mean make my own model with those important features or is there a way of converting the file to a solid? I know what your getting at but don't know how to go about it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2010 at 1:26pm
Yeah I mean make your own model. Throw down some planes and start modeling. 
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