SLC weight - heavy?

[HCF - John]

Hello all,
Hoping to learn a little about weight and the SLC. I've had interest in having a car built or buying a completed car for a little while now.

One of the things that's always surprised me is the ~2,500lb weight of the LS3-powered "basic build" SLC. When I compare to the Beck 904 at ~1,700lbs and some of the crazy Porsche-based V-8 track cars (ex - Porsche 912 912 | eBay) that weigh just under 2,000lbs, the SLC's extra weight doesn't make sense.

In both comparisons it's the SLC's aluminum chassis vs steel tube chassis and steel unibody - I'd expect the SLC to be lighter. I'd expect the aluminum DART motor in that 912 to weigh similar to the LS3, and an old air cooled 6 to be of similar weight to the LS3. I suppose there might be a 100lb weight difference in favor of the other two from the lighter transaxle, and perhaps 30-40lbs from the A/C system - but the rest is a mystery to me!

Anyone help me with ideas on where the extra 500-800lbs is coming from vs those other two cars?
Best,
John

 

[Dave Nugent]

http://www.gt40s.com/forum/rcr-forum-rcr40-slc-p4-mkiv/29839-how-light-superlite-coupe.html

 

[Mike]

The 1st things that come to mind is the big Z06 sized tires with large Camaro calipers & rotors, full steel roll cage, longer wheelbase-size, if it's a Ricardo trans - they are heavy 200lbs +-, HVAC system (compressor, evaporator, & associated parts with fluid), larger gas tank, larger full glass windshield, radiator with coolant & long runs to back, full cab with associated panels and..... ran out of quick thoughts.

 

[Jack]

It's light! Quick stats:
Bugatti Veron - 4162 pounds
Mclaren F-1 - 2513
Saleen S7 - 2749

 

[Bill]

Steel is about 2.5 times heavier than aluminum. However, aluminium is not as strong as steel either. Consequently, the chassis uses large square aluminum tubes (2x2", 2x6", etc) and the front tub is constructed with quite a bit of 1/8" aluminum plate. The result is a super stiff chassis.

BTW, a Porsche air cooled 6 is heavier than a LS3. A quick Google search says:

• ~500lbs: Porsche air cooled 6 turbo
• ~350lbs: GM LS3

Considering the weight, power, cost and reliability of a LS3, the choice is a simple one.

 

[HCF - John]

Thanks for the replies, guys!

Dave & Mike - much appreciate the datapoints. Sub 2,000lbs with the full car, wheels, LS3 motor, tranny, suspension, brakes, fuel tank, etc. What I take away from that is all the little bits that let it be a road car really add up!

Jack - other cars' weights noted, but they're more production-based consumer cars. The GTM, 904 and some other component / kit cars are a better comparison.

Bill - fully dressed, the air cooled 6's used in the 904 are in the same general neighborhood as the LS3; with the Turbo motors definitely being heavier. No doubt, with the 20+ years of advancement that the Chevy motor is the better pick for a SLC all around.

Regarding the comparison I was trying to make between 904 and SL-C... much of that weight difference must come from the frame (which doesn't need to be as robust, only designed to handle 275-350hp... vs the SLC designed to holding 700+ (?)), smaller wheels and the lack of a full cage. It makes sense!
Best,
John

 

[Eric McClellan]

I weighed mine and it was 2,450lbs with about 8-10 gallons of gas.

Mine was pretty standard, nothing fancy tacked on or extras bolted on. Some carpet and interior bits were the only 'extras' I had.

Had a 43-57 weight distro.

 

[Dave Nugent]

Eric,

You didn't have any sound deadening material installed at all? That in itself can add a lot of weight.

 

[Eric McClellan]

Eric,

You didn't have any sound deadening material installed at all? That in itself can add a lot of weight.

Oh, yes I did have a total of about 50lbs of material. 2 of the big boxes of sound/heat material.

So, let's call it 2,400lbs with no heat/sound mat.

 

[Chris Kouba]

John,

Have you ever seen a 904 in person? They are miniscule. It'd be entertaining to see a 904 and SLC side-by-side. Similarly, someone here once posted a photo of a GT40 being trailed by a 2nd gen MR2. Seen together, it made the MR2 look enormous.

The 904 and SLC are massively different in their footprints.

Chris

 

[James]

The body is also a bit heavy in the world of fiberglass

Front Piece - 60lbs
Rear Clam Shell - 90lbs

If you had madd fiberglass skills you would make a mold and do it in fiberglass (S2-glass) cloth with epoxy resin and use a nomex honeycomb sandwich. You would probably cut that weight of both of them in half. (about a 70 lb savings)

You would make the rear cross-member out of chromoly and take it from 25lbs to about 15 (you could use thinner walled and have the same strength)

If you were more daring you could make the roll-cage of chromoly too and save about 20lbs, but I heard it's a bit dangerous to do a chromoly roll-cage, as they done bend, they just break, and if you roll over or crash in a serious accident, the last thing you want is to get impaled onto a piece of roll-cage

Two piece rotors all around could save about 30 lbs


So with the above only, w/o the cage mod,, you could save about 120 lbs

 

[Jack]

Lets not forget the premise of the SL-C.
A great Supercar at an affordable price.
Fran has not raised the base price in years.
To accomplish this the materials cost are considered
seriously. The chassis is elegant simplicity and is like jewelry.
The body is hand laid fiberglass for a reason. Easily repairable
without the great expense of fixing more exotic materials.
Key word is affordable.

 

[Eric McClellan]

PLUS!!

Keep this in mind... 2,400lbs in the car world is DAMN light. It's the lightest vehicle I've ever owned outside of a motorcycle.

 

[Frank Clark]

If you were more daring you could make the roll-cage of chromoly too and save about 20lbs, but I heard it's a bit dangerous to do a chromoly roll-cage, as they done bend, they just break

Chrome Moly does not "break". It is less forgiving when being welded by a hack, needs the proper filler and in many cases should be stressed relieved after welding.

We have built chassis using 4130 in the garage and have never had a crack, much less a "break". We have had it bend, but that has always taken a multi-flip accident with a spectacular landing. Even then the bending has been inches.

In our garage, ALL of the DOM tubing is 4130.

This link pretty much covers the issues with using welding it: TIG Welding Chrome-Moly Tubing

For a price, I am sure Fran's guys will do your steel parts in thinner 4130 if you are looking to save a few pounds. But realistically, if you are pushing things hard enough that 50lbs makes a difference, you probably need a full cage. That will add quite a bit of weight and with that much tubing 4130 will make a noticeable difference.

For me personally, I'd eat a few less burgers if I really wanted to trim a bit of weight off the car.

 

[Howard Jones]

2000 pounds is only 500 pounds more that a Indy car and nearly exactly the same weight as a Rolex Daytona prototype. Both of these cars are more than 5 times the cost of a SLC, much more.

I think the question would be. What would it cost to have Fran make you the parts to save 400 pounds.....................Sit down.........have a coupe of drinks and...............hang on to the chair...............I think you will be shocked.

Assume a LS3, Porsche G50, track car build with R6's and a full cage. Little or no creature comforts. Forget AC, sound deadening, and very limited heat shielding. Single seat, Lexan windshield, no wipers.

The 120 pounds you saved above would cost thousands to have made. The first 100 pounds or so is doable for a price but the last 100 pounds is going to be really big bucks.

My guess would be to nearly double the cost to cut 400 pounds from the standard track build.

These cars are so fast already that I really don't see the point. It is a interesting exercise however. One that I have done more than once in the last 5 years and came to the same conclusion each time. I can't afford it.

I agree with Frank............go on a diet or hire a little bitty real race car driver.

 

[HCF - John]

Chris,
Yes, I have several times and agree they're small! Beck gave me a ride in his car a few years ago... hit 150mph before he grabbed the shift lever to go from 4th to 5th. Told him I still had some years left and was thoroughly impressed. Definitely left an impression!

Got to see a real one about a year ago at a PCA meet. Really neat cars.
https://www.youtube.com/watch?v=7TXYSBoup4w

I think Beck has 904 dimensions on his website, so pretty easy to compare to SLC dimensions.

I'll see my first SLC this Sunday - looking forward to being able to compare them and make a call on what I want to have in my garage.
Best,
John

John,

Have you ever seen a 904 in person? They are miniscule. It'd be entertaining to see a 904 and SLC side-by-side. Similarly, someone here once posted a photo of a GT40 being trailed by a 2nd gen MR2. Seen together, it made the MR2 look enormous.

The 904 and SLC are massively different in their footprints.

Chris

 

[Fran Hall RCR]

John,
remember that the Beck car has a longer wheelbase and wider track/body than an original 904..
Having had originals and our replica 904s (original body) at RCR the difference is huge to an SLC...

 

[Frank Clark]

And just to put the weight into perspective...

On our Sprint Cars, without wings and without driver, we are about 1300lbs.

This is:

SBC Steel block, aluminum heads, wet sump
About 30lbs of body work
One aluminum seat
One steel or Ti brake rotor on rear axle
One aluminum brake rotor and motorcycle size caliper on Left Front
Power Steering
Aluminum rear axle
Plastic fuel tank (with bladder)
NO SPEEDO
NO TACH
NO A/C
NO MUFFLERS
NO COOLING FAN
NO FLYWHEEL
NO TRANSMISSION
NO DIFFERENTIAL
NO CLUTCH
NO BATTERY
NO STARTER

These are bare minimum cars. Tires and wheels considerably less than half the weight of a road car. Bare minimum of bolts. Most rod ends are aluminum. All of the suspension bars are aluminum. Heck, there is only 1 u-joint in the whole car.

While granted this is 1000lbs less than an SLC, there is a WHOLE LOT more to an SLC. We can build a Sprint Car in a week of evenings - comfortably. And half of that time is getting the rear end geometry correct and the seat mounted. Could do it in one day if we rushed. Compare that to what it takes to assemble an SLC even if you had all of the parts laid out in the shop.

 

[HCF - John]

Fran,
I didn't know you ever made a 904 replica. Did you discontinue it?
Best,
John

John,
remember that the Beck car has a longer wheelbase and wider track/body than an original 904..
Having had originals and our replica 904s (original body) at RCR the difference is huge to an SLC...

 

[Fran Hall RCR]

Yes we did discontinue them...in fact I sold our last inventory of windscreens to my buddies Kevin Hines and Chuck Beck

We built this car with a Boxster drivetrain and did our own Carrera 6 body panels, 917 style wheels too but maintained the original wheelbase

We build lots of custom cars and parts that we don't advertise as most owners like the one off exclusivity from time to time.