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George is correct about the weight bias depending on the use and HP. As I kept producing more horsepower with my Top Fuel bike, I had to keep extending the wheelbase at the back end to push the weight more forward. As power went up, it would hit the wheelie bar so hard it would unload the rear tire. I ended up with a 90" wheelbase and 7 foot long wheelie bars. I could run 1.10 60 foots, but if I tried to hit it harder it would still hit the bars too hard and unload the tire.
Through that transition period I ended up adding 8" of wheelbase at the rear axle and a foot of wheelie bar. I could have probably used a couple more inches at the rear axle and then maybe run 1.0 60 foots, but I got really angry at the sanctions and sold my bike while it was still the fastest Harley in the world.
So yes, there is no perfect bias for all applications, only perfect for your combination.
Hi.
My 68 Coupe weigh 2976 (1350kg) with half tank of fuel.
My mods is alu cylinder heads- alu wather pump- alu inntake- alu master brake pump- wilwood dynalite brake calipers - composite rear spring.
My future plans is: Alu radiator - ligth starter - dry cell battery
Where is the cheapeast/easiest place to go to get your car weighed? I would be curious what mine is at. 79 4-speed car with front and rear low speed impact bumpers removed (roughly 100 pounds total), aluminum heads, aluminum intake, composite rear spring, no rear tire or carrier, c5 seats.
Hoping for around 3200 without me in it. Dang 79 was like 3500 pounds from the factory.
You can do aluminum this and aluminum that and you are just taking baby steps
if you are really serious about getting down to a light weight c3 you have to think about the whole front end
the heavy stock fiber glass nose and hood along with all the extra metal and opening headlights. I with friends took a sawsall and cut the front end off right in front of the fire wall. I had been to the 24 hours of daytona race in the early 80s and the factory backed corvette racing team had a pair of twin turbo 1981 entries. I was examining what they had done. I later saw one of them in California in a personal car collection and I decided that I needed to go on a weight loss and build one. I ordered the front end and hood from ecklers which was thinner fiber glass. That alone was 150 pounds of pork off the front end. Then you remove all that extra metal and vacuum headlight tank. Everything was gone from the frame in front of the fire wall I kept the radiator hoop mounts and the inner fenders so it was not open to the tires.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by mobird
Love seeing these low numbers for our cars!
Where is the cheapeast/easiest place to go to get your car weighed? I would be curious what mine is at. 79 4-speed car with front and rear low speed impact bumpers removed (roughly 100 pounds total), aluminum heads, aluminum intake, composite rear spring, no rear tire or carrier, c5 seats.
Hoping for around 3200 without me in it. Dang 79 was like 3500 pounds from the factory.
I went to a nearby truck stop on the interstate and got my car weighed there ($10). The nice thing about the truck scale is that it is segmented, so you can put the front wheels on one part and the rear wheels on another to get a f/r weight readout.
I went to our local landfill and got it weighed for free. If I wanted a printout it would have cost me $5. I just wrote it down on a gas receipt I had in my console.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by gkull
Rotating weight has some dynamics like the distance from the centerline. So a lighter weight larger diameter is worse than a heavy small diameter. The dodge R/T also has a drive shaft 3 times as long as a c3 vette.
So you really want a small 6.125 light weight damper, light weight crank with knife edge or pendulum cut, 154 tooth light weight flywheel and PP, or in the case of an automatic a smaller diameter light weight TC, and light weight wheels and tires.
When I had an automatic and my 427 Motown SBC. I used the 9.5 inch 3800 stall with anti ballooning plate. very light in comparison to 10 & 11 inch. When I first installed the 5 speed I used a billet steel 22 pound SFI and later switched to a 11.5 pound aluminum. Weld drag racing 10X15's with goodyear 10X28 slicks
That's not an accurate blanket statement. Ya gotta do the math (for each flywheel or driveshaft) to see which combo (lighter weight but bigger diameter or heavier weight but smaller diameter) comes out ahead.
Edit: Anyone know the wall thickness of a stock 2" driveshaft? I'm trying to do some rotating inertia and strength calculations for the stock driveshaft in my car to see what aluminum shaft sizing (OD and wall thickness) would work out for a weight reduction replacement.
Last edited by 69427; Jun 1, 2018 at 12:56 PM.
Reason: Adding content.
You can do aluminum this and aluminum that and you are just taking baby steps
if you are really serious about getting down to a light weight c3 you have to think about the whole front end
the heavy stock fiber glass nose and hood along with all the extra metal and opening headlights. I with friends took a sawsall and cut the front end off right in front of the fire wall. I had been to the 24 hours of daytona race in the early 80s and the factory backed corvette racing team had a pair of twin turbo 1981 entries. I was examining what they had done. I later saw one of them in California in a personal car collection and I decided that I needed to go on a weight loss and build one. I ordered the front end and hood from ecklers which was thinner fiber glass. That alone was 150 pounds of pork off the front end. Then you remove all that extra metal and vacuum headlight tank. Everything was gone from the frame in front of the fire wall I kept the radiator hoop mounts and the inner fenders so it was not open to the tires.
While I agree with what you're saying, I think that is way beyond what most people are willing to do, especially when most of these cars will not be used as track cars. I mean where do you stop? Chromoly tube frame, all aluminum engine and differential, titanium fasteners, carbon fiber body?
Any weight taken off will help and there are a lot of easy places to do it.
Edit: Anyone know the wall thickness of a stock 2" driveshaft? I'm trying to do some rotating inertia and strength calculations for the stock driveshaft in my car to see what aluminum shaft sizing (OD and wall thickness) would work out for a weight reduction replacement.
I was going to question the aluminum driveshaft HP reasoning, etc. reasoning myself but then thought better of it. The aluminum driveshaft weight and diameter differences should mostly matter with regard to different moments of inertia, and that has to do with acceleration. There's a trade-off there. F=m x a vs. T=I x alpha
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by ignatz
I was going to question the aluminum driveshaft HP reasoning, etc. reasoning myself but then thought better of it. The aluminum driveshaft weight and diameter differences should mostly matter with regard to different moments of inertia, and that has to do with acceleration. There's a trade-off there. F=m x a vs. T=I x alpha
Will be interested to see what you have to say!
While I'm looking around for info on the wall thickness of a stock 2" steel driveshaft I've been dusting off the cobwebs that have formed since freshman mechanics/dynamics class. I'm starting with the 2" steel and 3" aluminum shafts, and using a common wall thickness of .100" (it also makes the math easier ). So far it looks like a 3" aluminum shaft would have about 8% less rotating inertia, and despite the reduced material strength of aluminum it should still be slightly stronger in torsion than the steel shaft.
Once I get some real numbers for the stock driveshaft and a comparable aluminum shaft calculated out, I might try to talk you into checking my math.
While this does not address the question of whether a lighter but larger diameter aluminum driveshaft is a net win or net loss, it does address how torque and moment-of-inertia are related to acceleration
BTW, wheels are a consideration as well - not addressed here
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). So far it looks like a 3" aluminum shaft would have about 8% less rotating inertia, and despite the reduced material strength of aluminum it should still be slightly stronger in torsion than the steel shaft.