Reducing weight

[cRiPpLe_rOoStEr]

Reducing unsprung mass has been often praised as a low-hanging fruit when it comes to a more spirited driving, and it also may increase fuel-efficiency, yet a weight reduction on other parts of the vehicle may not become so negligible at all. Finding the amount of places to get rid of a few ounces at each may take longer than choosing one single place to take some pounds away at once. Well, maybe you were more concerned while hauling an unusual load, so it might've been more a matter of driving style than relying on the load as some sort of an "innertial battery". Just consider the example of a big-rig going a long stretch downhill, with Jake Brakes on and some low gear in order to avoid overheating the brakes, I'm sure such conditions would prevent much of the innertia to be recovered in order to increase fuel savings...

[Nathan jones]

Thanks Ecky, the fuel tank will be 25ltr aluminum, if I ever get time to change it. Early next year likely. It's position will be right at the very rear inside the cabin, rear to where I replaced the wheel well. As long as it's fuel tight upside down and vents outside I'm allowed. It will help with weight distribution too. Thanks also for replies, I may have to cast my own al brake bells at some future point and yes drilling helps with heat dissipation and reduces weight and wear however it takes time and effort, rarely see it these days except on motorbikes. The Prius calipers do have ceramic pistons on the front but small aluminum units may be an improvement when it's time

Plus stuff in this car is becoming so old replacing a tank with a new one fitted with a new pump is no problem, and will likely be cheaper than just a OE pump

Thanks again for thoughts. I have two Prius and the lighter one consistently brings back a 22-24mpg improvement driven with identical variables

[ps2fixer]

When I'm hauling a 2nd car on a dolly with my truck going similar speeds, sometimes I see an increase in MPG. I think it's more of the boat tail effect than the weight. I've hauled scrap and all kind of misc stuff in my truck, weighted down it coasts farther, adjusting the driving style for that and I normally don't see much of an MPG effect unless I have unpredictable stops like driving through the city with stop lights.

There's a saying I heard that sprung weight reduction is like 10x that of unsprung, but I'm pretty sure the context of the saying is for racing and probably relates to handling + acceleration + braking. Spinning weight has a larger effect than non spinning effectively when you're trying to change speed.

There's "batteries" designed as a spinning mass in a vacuum on magnet bearings to have as little friction as possible. Google says those flywheel batteries can be up to 90% efficient. Clearly the longer the time between charge and discharge (self discharge rate) will hurt that figure.

Either case, with more weight, just pumping up the tires to max sidewall helps offset the rolling resistance added by the weight. There's clearly an advantage with going lighter but for steady state speeds weight doesn't have much of an effect.

Most extreme example I can think of is a semi truck, fully loaded it looks like they loose around 30-35% fuel econ due to weight, but they are running around with and extra 24 tons using the figured posted. My Prius is just under 1.5 tons to give context. I'd say the areo effect is much much larger lol.

Depends on the truck engine/trans/rear gearing and the type of trailer. Our Volvo that pulls a flatbed gets 12 mpg bobtail(no trailer), 10mpg with trailer(deadhead) and around 6.5–7 loaded(48,000lbs payload grossing around 79,000lbs). Our Kenworth that pulls the same trailer type and weight gets around 7.5–8 loaded. And around the same deadhead.

https://www.quora.com/What-s-the-mil...l-trailer-load

[cRiPpLe_rOoStEr]

Originally Posted by ps2fixer

There's "batteries" designed as a spinning mass in a vacuum on magnet bearings to have as little friction as possible.

IIRC the only production car resorting to it was a Porsche. I don't remember its name, but I remember seeing one roaming around in my hometown.

[freebeard]

Formula One Kinetic Energy Recovery System (KERS):

https://www.racecar-engineering.com › articles › the-basics-of-f1-kers
The basics of F1 KERS - Racecar Engineering - Racing
Let's start with a definition: KERS stands for Kinetic Energy Recovery System and was introduced by the FIA to direct the Formula 1 engineering community towards developing greener technologies. Kinetic energy is energy stored in motion and can be thought of as the energy that is required to stop that motion.

[ps2fixer]

The flywheel has been used as a battery a bit in history. This is pretty old tech, check out the gyrobus.

https://en.wikipedia.org/wiki/Gyrobus

Disadvantages

Weight: a bus which can carry 20 persons and has a range of 2 km (1.2 mi) requires a flywheel weighing about 3 tons.
The flywheel, which turns at 3000 revolutions per minute, requires special attachment and security—because the external speed of the disk is 900 km/h (560 mph).
Driving a gyrobus has the added complexity that the flywheel acts as a gyroscope that will resist changes in orientation, for example when a bus tilts while making a turn, assuming that the flywheel has a horizontal rotation axis. This effect can be counteracted by using two coaxial contra-rotating flywheels.

It's interesting to hear a flywheel based energy storage was developed, the negatives are really bad for racing, resistance of changing direction, and added weight. I'm sure their efforts were focused on a small weight that spins at very high rpm. The one in the bus only spun at 3000 rpm, but it was around 3 tons too.

I was looking for a vid I saw before on these, and this one came up, seems to cover a little bit of everything. One I was thinking of was the power grid flywheel based energy storage where a guy tours the place and talks about the weight, rpm etc. Pretty crazy setup really. There's even a mention of the F1 system near the end, 6500 rpm seems quite low, but probably a lot safer than something half the weight spinning twice the speed.

https://www.youtube.com/watch?v=_QLEERYS5C8

[65whitelion]

One of the great quotes I love;
Drum brakes would be great, if they worked!

[Ecky]

Originally Posted by 65whitelion

One of the great quotes I love;
Drum brakes would be great, if they worked!

I was able to do handbrake slides with my Insight's 180mm rear drums. They were only ~5lbs (2.2kg) each.

[ps2fixer]

Originally Posted by 65whitelion

One of the great quotes I love;
Drum brakes would be great, if they worked!

I don't understand the big hype behind disc brakes, drum brakes have always worked great for me. It's easier to make "big" brakes in the disc config by using 4 or 6 piston calipers and such. Disc front drum rear is my fav brake layout. Bonus is the drum setup shields the brake parts from the weather some, so generally speaking there's less rust related issues up here in Michigan for drum brakes. Slides are always rusting up and freezing up, caliper pin issues, etc. It's quite common to have the brake pads not slide correctly and wear at an angle. If a vehicle sits, the drum brakes do have more issues with the shoes rusting to the drum, but popping the tire off and hitting the drum with a hammer generally frees them up pretty easily.

For a race car, I could see the desire for disc all around as they can be over sized easier and such, but for a consumer grade vehicle, I don't mind rear drum.

[65whitelion]

Originally Posted by Ecky

I was able to do handbrake slides with my Insight's 180mm rear drums. They were only ~5lbs (2.2kg) each.

Fun, but....
My old Australian Falcon wagon (1971) used to do the same.....but not always when you wanted it to :-o

In the "old days" driving around Aus, creek crossings were common, and drying out your drum brakes was a necessary task.....usually just with judicious use of the brakes, but many an unwary traveler ended up red-faced (or worse) with brake failure.