Trains also get to roll on steel wheels on steel rails. I imaging there is a good bit less friction with that setup than with a rubber tire on a road.
Trains also get to roll on steel wheels on steel rails. I imaging there is a good bit less friction with that setup than with a rubber tire on a road.
Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.
Who do you know? I worked for Volvo Truck for most of the 90's.
pinchvalve wrote:
Rick Dobberton. I never really figured out if he was a genius or a kook.
Too bad the Navette motorhomes never took off.
bravenrace wrote:pinchvalve wrote:Rick Dobberton. I never really figured out if he was a genius or a kook.
yes.
In reply to Sky_Render:
I have to see what's on the computer at home. There is no connection between the Diesel engine and the wheels. They are good around town but I think on the highway you start to lose mileage. Someone was testing it in an over the road and it wasn't worth the added expense and complexity.
I'll just leave this here.
I would give up a lot of fuel mileage to be able to do that.
Big Rig Arrow
Sky_Render wrote:Leafy wrote:A "supercapacitor" for "30 seconds worth of full power"? Seriously?! Let's do some math. A *conservative* figure for full power on a diesel big rig is 600 horsepower, or 400 kW. That's 400,000 J/s. Over 30 seconds, that's 12,000,000 Joules, or 12MJ, of energy. The *best* supercapacitors have an energy density of 15 watt-hours (Wh) per kilogram. One Watt-hour is 3600 joules. 12,000,000 J = 3,333 Wh At 15 Wh/kg, you're looking at **222 kg** of "supercapacitors." And most commercially-available supercaps have a *tenth* that capacity. Then you're looking at *two metric tons of supercapacitors.*Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.Guess they didnt think far enough out of the box, even if they just had a super cap with 30 seconds worth of full power stored on it that would be enough to cover most transient situations.
Even then 30 seconds is useless for climbing mountains even on the freeway. In many places you will need high torque for tens of minutes on end.
Adrian_Thompson wrote:Sky_Render wrote:Even then 30 seconds is useless for climbing mountains even on the freeway. In many places you will need high torque for tens of minutes on end.Leafy wrote:A "supercapacitor" for "30 seconds worth of full power"? Seriously?! Let's do some math. A *conservative* figure for full power on a diesel big rig is 600 horsepower, or 400 kW. That's 400,000 J/s. Over 30 seconds, that's 12,000,000 Joules, or 12MJ, of energy. The *best* supercapacitors have an energy density of 15 watt-hours (Wh) per kilogram. One Watt-hour is 3600 joules. 12,000,000 J = 3,333 Wh At 15 Wh/kg, you're looking at **222 kg** of "supercapacitors." And most commercially-available supercaps have a *tenth* that capacity. Then you're looking at *two metric tons of supercapacitors.*Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.Guess they didnt think far enough out of the box, even if they just had a super cap with 30 seconds worth of full power stored on it that would be enough to cover most transient situations.
Sure, but by then they hybrid electric system will have responded to the load. 30 seconds was some arbitrary number I made up. Doing real engineering could probably point you to the real amount of time you need for the system to respond, which is hopefully some amount of time closer to 3 seconds than 30 seconds.
Backup UPS power systems have employed a number of technologies and strategies to address demands of instant delivery vs long term delivery.
Old school diesel-generators take a while to come online, so inverters driven by lead-acid batteries were the norm.
Nowdays they use supercaps, along with Li batteries, that bridge to whatever prime source is present.
One approach uses a bank of stock Diving tanks, connected by a common distribution manifold, spinning up a turbo driven alternator.
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