MR2-FA: Additional Project Considerations

I've done plenty of analysis so far but I've got a lot more on my mind that doesn't fit neatly into a single topic so this is my post with random things I'm either thinking about or need to take into consideration when designing the exterior of the MR2. 

Polar Moiment of Inertia
The technical definition of this is the resistance of an object to rotational acceleration.  The practical application is putting more weight past the wheel base on either end of the car affects weight transfer and therefore how the car corners.   You want as little mass past the wheelbase as possible ideally which creates a low polar moment of inertia.  The textbook example of this is the McLaren F1: there's almost nothing past the wheels. Despite being only 4.6 inches longer than the SW20 MR2 the wheelbase is 12.5 inches longer. In people terms that's the difference between having nice long sprinters legs or a torso the size of someone six inches taller than you. 

On the MR2 there's a lot of mass past the wheelbase on either side of the car.  In the back you've got the exhaust system, trunk, wing, tail lights, and bumper and in the front you've got the radiator, headlights, windshield washer tank, and front bumper.  I need to pull as much weight inwards, and low, as possible. 

Facilities
I obviously spend a lot of my free time working on making things. I also spend an inordinate amount of time cleaning up. Part of it is that I should work neater but a good chunk of it is purely based on the ameneties of my workspace or lack thereof. There's two locations in my house, other than my home office, that are my domain where I'm free to do as I wish: an unfinished room in my basement that we call "the junk room", and; the garage. There's a stipulation on the garage though, which is that at the end of my nightly activities my wife would really like her car parked inside.

A hobby like mine almost requires a house with a three car garage or at least a lot more space than I've got avaliable. I just don't have a lot of space to hold things that are in-process. I made some adjustments this week (I'm on vacation) to my workspace that I think will save some grief in the future.

After thinking through what was wrong with my previous garage setups it's that I didn't take into account the various states that a specific piece or part can be found in.   As a result I've setup my work areas like a factory; you have raw materials inventory, a WIP inventory, an assembly/construction floor, and a design studio.  This new level of organization should also speed up the process since I won't have to go rummaging around to find a specific material. 

Construction Order
If I gave you a pencil and a piece of paper and told you to draw a car where would you start?  How would you draw the rest?  In what order could you realistically figure out the proportions of things?  If you haven't done it before, you'd probably need a little bit of time to sort that out.  Given that I'm building and not drawing a car, I need to have this all thought through to some extent before I dive in or I'm going to end up with mismatched shapes and locations. 

I've thought about it quite a bit, and here's the order that I think makes sense with regards to builing each individual piece. 

1. Doors: This is going to be the most devilishly hard part of this entire exercise because it employs all the skills I have the least experience with.  Since the doors are the only OEM body piece that needs to remain essentially intact for safety, and also needs to be completely redesigned for asthetics, it makes sense to start there.

2. Mounting Brackets for Headlights:  All pieces on the front of the car need to fit around these so they need to be mounted good and sturdy or everything else will be off. 

3. Front Fenders: I want to get experience with the foam and molding before I go crazy building out a front bumper.  I can't make a mold for the fenders and get all the mounting tabs if the Bumper is in the way.  These and the doors sort of need to be designed together so there will probably be some overlap.

4. Front Bumper: The final line of the hood will need to be based on where the bumper terminates.  I'll need to relocate the radiator and build the ducting as part of this piece.

5. Hood:  The hood is the last piece on the front of the car and till the bumper and radiator relocation are done I won't know how it needs to be setup. 

6. Side Intake Vents: If you look at the LFA these flow into the side skirts.  Till I have them completed I won't know what the skirts need to be shaped like.

7. Side Skirts: Last piece on the side of the car and the one most independent of everything else in terms of when I would need to construct it.  Makes sense to do it last then move on to the rear. 

8. Fastback Engine Lid:  To me the entire rear of the car starts here.  Can I put hinges on?  Will I make it and the trunk lid all one piece?  I'll probably decide that as I go but regardless the design of the rear of the vehicle needs to start with this. 

9. Trunk Lid.  I won't know if the rear quarter panels need to be reshaped to match the lid and fastback until I get all those and the trunk lid finished.  

10. Rear Quarter Panels: Much like the doors, this needs to stay relatively intact for safety.  However, unlike the doors if I screw up I can't just go to a junk yard and find another to replace it.  By the time I'm ready to play with this area I should be pretty good at tack welding and metal shaping which will help minimize the possibility of my screwing up. 

11. Rear Bumper:  The rest of the car will be done by this point and it's the last thing left besides the part I must finish absolutely last.

12. Mirrors:  In order to put mirros in the right position, you need to make sure you can see around the rear of the car.  Till I know how wide the car is going to be it's pointless to finish the mirrors.

Tooling
I've seen a lot of automotive exterior projects while surfing over on Fiberglass Forums.  There's a couple of gaps that I see in most of the projects that I want to address for my own.  The biggest recurring problems that I see are: 1) wasted materials 2)inconsistencies between two sides of the vehicle 3) lack of consistent lines across complex parts.  There are plenty of good reasons why all of these occur but I think the solutions all boil down to the same thing: lack of tools. 

If you're just globbing on some foam and shaping things from there of course you're going to waste a ton of foam.  If all you've got is a basic ruler to check your measurements of course things are going to be off between two sides of the car.  I have some ideas about what it would take in terms of tools to fix all this stuff - the problem is I have to make them myself because as near as I can tell they don't actually exist.

Gauging Success

Aerodynamics and vehicle dynamics are black arts to your average car guy. Things don't work like exactly like you think they should and you'll have no idea unless you've actually tested it. The forces at play are just too complex for equations and assumptions to be your entire basis for decision making. For aero that means a wind tunnel and for vehicle dynamics that means a chassis jig, shock jig, and a lot of seat time. Any of those are way beyond the means of any normal person. I don't know the first thing about applying fluid dynamics, or about chassis tuning and the blance between regidity and crash worthiness, nor adjusting the valving on a shock to achieve certain ride frequencies. I'm stuck with common sense, books, and buying someone elses coilover system.

The good news and bad news is that since I'm making a road car and not a race car I can get away with pretty much anything. It's good because if I make a mistake it's unlikely it'll kill me. It's bad because it'll be hard for me to ever know if I did it right. I'm going to do my best to figure out ways to test things but I'm probably going to have to ask for some help to figure out how well I did.