Weight Reduction Mods-240z

[Calico]

very interesting thread

[Dan Baldwin]

I am not sure what you mean about mounting the calipers `low on the spindles'. Are you just talking about the 5/7 o'clock mounting position?

Some random thoughts: while you are correct in that this lowers the centre of gravity of the strut assembly, as this is sprung, it does not affect the centre of gravity of the car at all;

The unsprung part of the car is indeed *part of the car*! Having them clocked at 6:00 does lower the c.g. Optimal placement would be a bit off the 6:00 position (aft of 6:00 for the fronts, forward of 6:00 for the rears) in the interests of minimizing polar moment.

For my perfectly optimized car, I have the front left caliper at 4:30, front right at 7:30, left rear at 6:45, right rear at 5:15.

[thehelix112]

[standard thread resurrection comment here]

 

Fair point Dan.

 

Dave

[redneck1545]

The unsprung part of the car is indeed *part of the car*! Having them clocked at 6:00 does lower the c.g. Optimal placement would be a bit off the 6:00 position (aft of 6:00 for the fronts, forward of 6:00 for the rears) in the interests of minimizing polar moment.

For my perfectly optimized car, I have the front left caliper at 4:30, front right at 7:30, left rear at 6:45, right rear at 5:15.

 

 

I got to thinking about this very subject the other day. I think the biggest thing people forget about is a little thing called gyroscopic precession. If you clock the calipers perfectly at the 6 o'clock position, yes you are putting the weight as low as it can go, but when you stomp on the brakes you will actually get an increase in forward momentum due to gyroscopic precession. Mounting them at 3 o'clock will give you the most added traction when stomping on the brakes because of the increase in "weight" on the tires when precession takes affect. As dan pointed out earlier the optimum placement would be 4:30 and that would take into account precession on CG and would be a comprimise of the two.

 

I understand the intrest in minimizing polar movement as to why you would clock each caliper differently.

 

Nice to know im not the only one who, instead of singing in the shower, pictures moving parts.

[Dan Baldwin]

I got to thinking about this very subject the other day. I think the biggest thing people forget about is a little thing called gyroscopic precession.

There isn't any gyroscopic precession because the braking torque is on the same axis that the wheel is spinning on.

 

If you clock the calipers perfectly at the 6 o'clock position, yes you are putting the weight as low as it can go, but when you stomp on the brakes you will actually get an increase in forward momentum due to gyroscopic precession.

No, you won't. For one thing, "momentum" is mass multiplied by velocity. When you hit the brakes, "momentum" will decrease as speed decreases. It won't INcrease.

Mounting them at 3 o'clock will give you the most added traction when stomping on the brakes because of the increase in "weight" on the tires when precession takes affect.

 

It may seem like where you locate the caliper will affect how the wheel is loaded/unloaded, but in reality it doesn't matter where the caliper is clocked, the load on the tire will be the same for a given level of deceleration. If you locate the caliper such that when you hit the brakes, the caliper is pulling DOWN on the rotor, it might seem like you should get more load on that tire, but if you do a free body diagram of the individual wheels/tires and for the car, you'll see that this isn't so. The caliper may be pushing DOWN on the rotor, but the rotor's pushing UP on the caliper with exactly the same force. Net effect on "downforce" at the tire contact patch is zero.

 

The additional load on the front tires under 1-g of braking, for a 2500 lb. car with a 20" high center of gravity and 92" wheelbase is going to be 2500 lb. * 20"/92" = 543 lb. Which is the amount that the rears will be UNloaded. Regardless of where any of the brake calipers is clocked.

 

Nice to know im not the only one who, instead of singing in the shower, pictures moving parts.

It's a kind of sickness...

[crazyoctopus]

i thought that i posted this awhile ago, but i guess that i didnt.

 

 

40 pounds $40, gutting the doors by crazyoctopus, on Flickr

 

20lbs per door

[rturbo 930]

Do you have windows installed? If not, why not remove the window frame?

[BluDestiny]

He has lexan sliders. check his Build thread

[crazyoctopus]

it is going to be a daily so i have to have some sort of outside protection.

[Racer Z]

I have read this entire thread and found interesting as well as empty. (no pun intended) By empty, I mean you guys have not listed any facts. You talk about things like removing the steel fenders and replacing them with fiberglass, in order to save weight. But, you have not told me how much the old fenders weighs, how much the new fenders weighs, how much weight you actually saved nor how light your wallet is now. Yes, one of you did mention that a stock steel fender weighs 11 Lbs each with no mention of the fiberglass replacement weight. Fiberglass is not as light as we are lead to believe. It's a big expense, especially if it only saves 1 Lbs per fender.

 

We are in the process of gutting our 240Z. We saved all the stuff we pulled out and weighed it, in an itemized fashion. We effectively removed 120 Lbs. The big ticket items were the heater unit and the wiper mechanism. The tar on the floor was not nearly as heavy as I had been expecting.

 

We weighed our Dash at about 25 Lbs. I mention this because I had seen an add for a fiberglass dash claiming I can save 30++ pounds. How can I save 30 pounds when the stock dash is already less than 30 pounds?

 

The stock seats are about 30-35 Lbs each with adjuster rails. That's light compared to some cars that have 50 Lbs seats. Our racing seats weighed in at 12 pounds each, before adding the Datsun adjuster rail. With the rail we only saved 10 pounds per seat. But we gained something even more important, proper belt placement and lateral support.

 

Swiss cheesing the car might look cool on a show car, but it looks mighty weak on a track car. The repeated forces will find a place to flex and crack.

 

My itemized list of weights. Some will items will be going back in or on. This is from a 73 240z.

 

Weight - Item name or description

7.5 - Wiper motor, linkage and blades

23.5 - Heater system, blower, core, plenums, ducts

2.0 - Parking brake lever, pivot pin, rod (cabin half)

20.25 - Dash with defrost trim, no meters, wires or switches

4.5 - Center console with choke lever and cables

35.0 - Original seat with adjuster (each, 70 pair)

16.25 - Momo Corsa racing seat with Datsun adjuster (each, 32.5 pair)

8.75 - Interior parts - plastic covers, rear sides, taillight cores, dome light, kick panels, boomerang panels, ect.

1.75 - Carpet under seats. Most of the carpet was missing or got sucked up in the vacuum prior to this, so I can't weight all of it.

5.125 - Interior vinyl from strut towers, door sills, trans-tunnel (headliner still in car)

16.5 - Front bumper w/override bar

1.5 - Wiring removed from rear harness (we removed the unused wires and put the rest back)

2.5 - Whole rear harness before mod

13.25 - Tool kit, jack chalks, jack handle, lug wrench, bag

2.25 - Door seals (both sides) this is just the rubber outer seal

0.25 - Shifter boot and flange

12.875 - Tar paper

4.625 - Insulation/padding (incomplete when we bought the car)

4.25 - Stock steering wheel w/horn pad

3.0 - "Racing" steering wheel - "Personal" is stamped in the aluminum finger, took it off an old truck haha

 

120 - Effective weight loss. Some of this will be going back in. Most went straight into the garbage.

[blue72]

I'm with Racer Z, I'd like to see the weights of some aftermarket parts. Then we'd have a better idea just how much weight we would be saving by switching to them.

 

When I had my Z completely torn apart for the bodywork and paint, I took the opportunity to weight a few items on my nice digital scale. Here's what I came up with for some of the parts on my '72 Z.

 

37.10 lbs

Hood

4.40 lbs

Cowl with styrofoam pad intact

2.40 lbs

Center valence piece

1.10 lbs

Right and left valence pieces, each

13.0 lbs

Right and left fenders, each

23.30 lbs

Left door, bare. No glass, window frame, door latch, mechanisms, hinges, nothing except the bare shell

9.70 lbs

Left door glass with the metal brace that bolts to the bottom of it, nothing more

2.60 lbs

Left door window regulator

3.50 lbs

Left door window frame w/ felt strips

19.20 lbs

Rear hatch, bare. No glass, weatherstripping, rubber, latch, lock or emblems

2.50 lbs

Right and left headlight buckets, metal, each

3.00 lbs

Right headlight bucket, original FRP style. Yes, they are heavier than the metal ones.

0.60 lbs

Gas filler flap, metal

1.00 lbs

Engine bay inspection covers, each

2.40 lbs

Grille, 240Z style

1.10 lbs

Taillight finishers, each

[blue72]

More to add:

 

7.30 lbs

'72 240Z Front bumper, completely bare

1.10 lbs

'72 240Z Bumper mount brackets, each

0.50 lbs

Bumper overriders, each

0.45 lbs

Bumper rubber strips, each

4.0 lbs

Interior vinyl kit (from MSA) includes center console, luggage riser, wheel housings and shock towers with cardboard shock tower pieces. Does not include door sills, headliner or a-pillar trim.

[Racer Z]

From 73 240z:

 

4.5 pounds

Headliner & foam, sun visors and rear view mirror mount (no mirror). This includes the vinyl on the A-Pillars.

[thehelix112]

Maybe your guys' last few posts could be stickied as a new thread or something, coz thats great info. My small contribution:

 

From 78 280z:

 

~65 pounds (bathroom scale)

Entire RHS door

 

Dave

Edited March 3, 2011 by thehelix112

[Racer Z]

Maybe your guys' last few posts could be stickied as a new thread or something, coz thats great info. My small contribution:

 

From 78 280z:

 

~65 pounds (bathroom scale)

Entire RHS door

 

Dave

 

I was thinking the same thing. Don't know how to sticky it. I guess a moderator would need to do that.

[mxgsfmdpx]

Yay. Some actual useful information in this thread. Thanks gents!!!

[Racer Z]

Door panels: 9 Lbs (pair)

Door pulls and related hardware: 2 Lbs (both doors)

Edited March 7, 2011 by Racer Z

[Racer Z]

I started a new thread dedicated to the itemized list of weights and other methods of weight reductions for your S30.

 

http://forums.hybridz.org/index.php/topic/98733-itemized-list-of-weights-for-the-purpose-of-weight-reduction/

[Gollum]

2 hours ago, smokehouse_83 said:

This thing is a toy to begin with. I’ll probably only drive it a few times a month. Im wondering how light you guys think it would be. 

 

A bare chassis is less than 500lbs iirc. Start adding require parts weight from there. Sub 2k WITH all the body panels is possible, but requires diligence.

[LLave]