Weight reduction

M

mcfoo

Well-known member
This winter I'm hoping to reduce some of the 60 lbs of excess weight off my FP Miata.

We all know some of it should come off of me (and it will) but the car is also a candidate for a diet.

The subject of fiberglass panels and specifically doors is one of my focal points.

The rules indicate the OEM doors can be gutted and original hinges must be retained...but can you use a fiberglass door along with OEM hinges? I found some that can save me about 10-12 lbs total.

My gut instinct says no but it doesn't hurt to ask.

Thanks
Tom B.
 
Nope, you cannot.

Notice that "doors" is not included on this list:
"The hood, hatchback, deck lid and fenders can be replaced by components of an alternate material, provided their appearance remains stock."

This is the extent of how you can modify your OEM doors:
"Stock door hinges must be retained and mounted in their stock location. Door hinges must be functional but can be lightened. Doors must be securely fastened closed, provided they can be opened or removed quickly in an emergency situation. Door handles can be removed and any resultant holes must be covered. The cover must not change the stock exterior contour of the door. The stock side impact beams may be removed."
 
Perfect example of : "If it doesn't say you can, then you can't".

I was thinking that all along but thought I may have missed something.

Thanks Kevin.
 
kruck":2daomzpr said:
This is the extent of how you can modify your OEM doors:
"Stock door hinges must be retained and mounted in their stock location. Door hinges must be functional but can be lightened. Doors must be securely fastened closed, provided they can be opened or removed quickly in an emergency situation. Door handles can be removed and any resultant holes must be covered. The cover must not change the stock exterior contour of the door. The stock side impact beams may be removed."
Click to expand...

Also -
"The body, unibody, frame and their components can be lightened, provided that structural rigidity is not compromised to the point of requiring additional support."

The doors fall under the body and body panel definitions:
Body – All parts of the car licked by the air stream and situated above the belly / floor with exception of the roll bar or cage.
Body Panel – A replaceable section of the body.

You can lighten their inner structure, hence the "gutted door" on many prod cars, but as noted cannot change the material they are made of.
 
Remove all interior components of the doors, window mechanisms, including the factory side impact panels. The door has and exterior skin, a side skin and interior skin. Remove the interior skin side of the door structure, where the handles and interior panels mount. Remove too much of the interior panel, and your doors will be too "floppy". Leave about a 1/2" flange on the interior surface and finish off the sharp edges to prevent getting cut in the future. You can retain the stock door opening mechanism, unless you want to "pin" the door closed. You can spend a lot of time drilling large holes in the side skin of the door, and maybe save 2 - 4 ounces of weight.

Most beneficial weight reduction areas:
Replaced the stock hood and deck lid with a fiberglass hood and deck lid.
Replace the stock flywheel & clutch assembly with a proper race unit. Offered by Mazda Comp. that is worth more than 25 pounds removed.
Use the lightest road wheels possible.

Nothing else will yield significant weight reduction.
 
This is (was) Rick Harris's car, so he certainly took steps to lighten it with CF hood and windshield, etc.

The problem is Rick and I are separated by about 50#'s and that's about the amount I'm over the 2127 requirement.

You might be thinking, "lose some of your own weight fatass" but I'm really not.

Only about 15#s heavier than I was coming out of "basic" in 1971...so I'm kinda proud of that.

The battery might be a good place to look. Anyone have a suggestion for a lighter battery given a total loss system and Electromotive TEC 3r? It has a Optima Yellow top now.

Tom B.
 
Personally I would leave the yellow top alone. With a full loss system, I would want enough battery to be able to crank the car 2-3 times assuming a flooded engine on grid, and then if you spin during a race and flood the engine.. thus a full loss system *IMO* should have a full size battery. If you have an alternator, I'd be comfortable using a smaller battery. weight in the engine bay or weight in the cabin- which do you prefer?

On my RX7, the doors are gutted to ONLY the outer skin, the door hinges, and about a 1/2" lip around the edge of the door skin. It's pinned shut and the door handle has been removed. essentially, that's the absolute maximum per the rules. The door is pretty floppy, but don't put any weight on it and it's all good.
 
mcfoo":9eit8af1 said:
The battery might be a good place to look. Anyone have a suggestion for a lighter battery given a total loss system and Electromotive TEC 3r? It has a Optima Yellow top now.

Tom B.
Click to expand...

In an effort to drop some extra weight from my new Spridget, I found that the battery in the car was huge. It weighed 60+ pounds. I also have a total loss system and an Electromotive XDi. I went to a store called Batteries Plus to chat about my options. They pointed me to a mobility scooter battery that weighed 16 pounds. It's about 6" on a side and has 28Amp hours of power. More than enough to run it for an hour or two. I wired in a jump adapter gizmo like the formula cars do just in case I need to jump her on the false grid. So far it's worked very well. The best part? It was $75.

Dayle
 
Dayle Frame":fm6l0dwk said:
mcfoo":fm6l0dwk said:
The battery might be a good place to look. Anyone have a suggestion for a lighter battery given a total loss system and Electromotive TEC 3r? It has a Optima Yellow top now.

Tom B.
Click to expand...

In an effort to drop some extra weight from my new Spridget, I found that the battery in the car was huge. It weighed 60+ pounds. I also have a total loss system and an Electromotive XDi. I went to a store called Batteries Plus to chat about my options. They pointed me to a mobility scooter battery that weighed 16 pounds. It's about 6" on a side and has 28Amp hours of power. More than enough to run it for an hour or two. I wired in a jump adapter gizmo like the formula cars do just in case I need to jump her on the false grid. So far it's worked very well. The best part? It was $75.

Dayle
Click to expand...

Jeez, that's less than $2.00 a pound for a 44lb savings. Nice
Isn't the XDi system for carbureted cars? My fuel injection may require a little more juice but certainly worth looking into.

Thanks.
Tom B.
 
mcfoo":17otior9 said:
Dayle Frame":17otior9 said:
mcfoo":17otior9 said:
The battery might be a good place to look. Anyone have a suggestion for a lighter battery given a total loss system and Electromotive TEC 3r? It has a Optima Yellow top now.

Tom B.
Click to expand...

In an effort to drop some extra weight from my new Spridget, I found that the battery in the car was huge. It weighed 60+ pounds. I also have a total loss system and an Electromotive XDi. I went to a store called Batteries Plus to chat about my options. They pointed me to a mobility scooter battery that weighed 16 pounds. It's about 6" on a side and has 28Amp hours of power. More than enough to run it for an hour or two. I wired in a jump adapter gizmo like the formula cars do just in case I need to jump her on the false grid. So far it's worked very well. The best part? It was $75.

Dayle
Click to expand...



Jeez, that's less than $2.00 a pound for a 44lb savings. Nice
Isn't the XDi system for carbureted cars? My fuel injection may require a little more juice but certainly worth looking into.

Thanks.
Tom B.
Click to expand...

Yes, my Sprite is carbed but I'm not sure what a FI system needs. There was a variety of scooter batteries....I picked one in the middle of the weight range. Contact the folks at Elecromotive and see why juice it draws. I added up the draw for brake lights, fuel pumps, etc. and it came no where close to the 28Ahr so I've got some room to add I extra electrical hardware should I decide to do so.

Dayle
 
Tom,

I am not exactly sure what Jesse did for you when the car was at his shop. What you will need to do is completely re-design the fuel cell cage. There is a ton of weight I put in that area during the build. I would suggest taking the fuel cell out and use some aluminum mounts for the re-design. What I did is attach two stock engine hooks to the sides of the cell shell (holes are already there) and used an engine hoist to pull it all out at one time. Obviously disconnect all of the fuel lines. There are four bolts going through a 3/16" steel plate through the body for attachment. There is a 3/4" steel tubing cage welded to that 3/16" steel plate.

Email me if you ever have any questions at all about the car.
 
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