This is more of a.... "mechanical" discussion than anything else but it concerns a Sci-Fi inspired movie so...
Anyway, I'm not sure what made me think of this but it's a long drive home from work and it just sort of came to me as the Back to the Future theme started playing over my car stereo (streamed from my phone.)
Let's set the stage!
Back to the Future: Part 3
Marty has traveled back in time in a repaired DeLorean with the hopes of saving Doc from being killed by contemporary Biff Tannen and bringing him back to the future of 1985. Upon arrival in 1885 Marty encounters a band of Native Americans on horseback fleeing the Calvary, he turns the DeLorean around and begins driving away from them along the rough terrain eventually going down a smallish hill and backing the car into a small cave.
He exits the cave and smells the fuel of the car leaking out from an area in the undercarriage, he's scared out of the cave by a bear, falls down a hill, and knocks himself out and doesn't wake up for several hours. (So no opportunity to go to the car to attempt to patch the hole somehow or at least find a way to collect some fuel.) This leads to one of the obstacles in the movie, he and Doc have to find a way to power the DeLorean in order to be able to drive it back to the future since sufficient fuel isn't available. (They attempt to use spirituous beverages which end up blowing out an engine component, and any fuel that'd be around in 1885 would be unavailable to them in the small town of Hill Valley (gasoline did exist in this time as did internal combustion engines), there's also something of a time crunch having to do with Buford Tannen.)
But I was thinking about it... Would the DeLorean really have completely drained of fuel?
(Let's get one tangent out of the way, they could not go to the DeLorean Doc had come to 1885 in himself and take fuel from it. Storing a vehicle for even as short as a few months requires you to drain it of fuel since as the fuel ages it becomes a thick varnish that'd clog all of the engine and fuel line components. Any fuel in it Doc would have drained before storing the DeLorean and used up in any experiments if he didn't just completely dispose of it to prevent contaminating the timeline with it. Or, in the story-telling context, tampering with the stored DeLorean risks damaging it further making it unavailable to Doc and Marty in 1955.)
Let's allow a couple of things.... I'm not entirely sure any of the driving Marty did with the car over the rough terrain would have damaged the fuel line enough for it to leak, nor do I think where we see the fuel coming from is where it'd even be on the actual car. Even on a DeLorean I'd think the fuel line would be heartier and located somewhere higher up and not directly under the driver's door on the chassis.
So anyway:
The thoughts I have are:
That there's a fuel-pump between the tank and the engine and usually this pump is in the fuel tank itself and at the top of it even, so it seems to me that this alone would be the fuel is fine because it can't flow UP through the pump and then through the lines.
What's pushing the fuel through the lines and out the hole? Before leaving 1955 Doc says there's "gas in the tank" and let's assume he filled it up to give Marty and "himself" plenty of opportunity to use the DeLorean as needed to get back home. So this means the tank is filled with gas and then there's a little bit of air between the top of the tank and the filler door. A hole is formed in the fuel lines. That little bit of air is going to try and push the gas out but... What's going in the new void? Seems to me this would create something of a vacuum that would prevent the fuel from flowing out. I tried a small experiment where I took a full water bottle, opened it, took a small sip, and closed it. Full bottle, small bit of air at the top. Poked a hole near the bottom of the bottle.
The water sort of trickles out... Kind of. Granted it's not a hole-hole I just cut the side of the bottle with the knife to simulate maybe a torn fuel line. Now, I open the cap of the bottle and water flows out, atmospheric pressure pushes it out. Put the cap on, water trickles again. Nothing to fill the void. (Of course this means that when a car is running it has to work against creating a vacuum to get the fuel, but the pump is likely injecting air as it pulls the gasoline though the lines. No operating pump, nothing to push air in.)
The fuel line isn't at the exact bottom of the tank. There's something of a "water line" there and even when the tank is "empty" there's likely something still there that could be gotten to the pump if the car was at the right angle. They only need enough fuel to get the car up to 88, once.
A DeLorean got 18-20 miles to the gallon and had a 0-60 time of around 9 seconds. and 1/4 mile in 14 seconds. So even if they had a 10th of a gallon, like 12 ounces, the car could travel somewhere around 2 miles they only need to travel just over a third of a mile to get to 88. There wasn't 12 ounces of gasoline at the bottom of the tank, in the rest of the lines and even sitting in the engine/injectors (the DeLorean had a mechanical fuel injection, I don't know if that makes it more or less likely for there to be fuel just sitting in the injectors or a nearby reservoir)? Certainly if Doc can build a refrigerator in his lab/barn he could've made a tiny fuel tank to hold the few ounces of remaining fuel they had, calculated an efficient way to accelerate the car and gotten them home.
I dunno, just rambling. Thoughts?
Anyway, I'm not sure what made me think of this but it's a long drive home from work and it just sort of came to me as the Back to the Future theme started playing over my car stereo (streamed from my phone.)
Let's set the stage!
Back to the Future: Part 3
Marty has traveled back in time in a repaired DeLorean with the hopes of saving Doc from being killed by contemporary Biff Tannen and bringing him back to the future of 1985. Upon arrival in 1885 Marty encounters a band of Native Americans on horseback fleeing the Calvary, he turns the DeLorean around and begins driving away from them along the rough terrain eventually going down a smallish hill and backing the car into a small cave.
He exits the cave and smells the fuel of the car leaking out from an area in the undercarriage, he's scared out of the cave by a bear, falls down a hill, and knocks himself out and doesn't wake up for several hours. (So no opportunity to go to the car to attempt to patch the hole somehow or at least find a way to collect some fuel.) This leads to one of the obstacles in the movie, he and Doc have to find a way to power the DeLorean in order to be able to drive it back to the future since sufficient fuel isn't available. (They attempt to use spirituous beverages which end up blowing out an engine component, and any fuel that'd be around in 1885 would be unavailable to them in the small town of Hill Valley (gasoline did exist in this time as did internal combustion engines), there's also something of a time crunch having to do with Buford Tannen.)
But I was thinking about it... Would the DeLorean really have completely drained of fuel?
(Let's get one tangent out of the way, they could not go to the DeLorean Doc had come to 1885 in himself and take fuel from it. Storing a vehicle for even as short as a few months requires you to drain it of fuel since as the fuel ages it becomes a thick varnish that'd clog all of the engine and fuel line components. Any fuel in it Doc would have drained before storing the DeLorean and used up in any experiments if he didn't just completely dispose of it to prevent contaminating the timeline with it. Or, in the story-telling context, tampering with the stored DeLorean risks damaging it further making it unavailable to Doc and Marty in 1955.)
Let's allow a couple of things.... I'm not entirely sure any of the driving Marty did with the car over the rough terrain would have damaged the fuel line enough for it to leak, nor do I think where we see the fuel coming from is where it'd even be on the actual car. Even on a DeLorean I'd think the fuel line would be heartier and located somewhere higher up and not directly under the driver's door on the chassis.
So anyway:
The thoughts I have are:
That there's a fuel-pump between the tank and the engine and usually this pump is in the fuel tank itself and at the top of it even, so it seems to me that this alone would be the fuel is fine because it can't flow UP through the pump and then through the lines.
What's pushing the fuel through the lines and out the hole? Before leaving 1955 Doc says there's "gas in the tank" and let's assume he filled it up to give Marty and "himself" plenty of opportunity to use the DeLorean as needed to get back home. So this means the tank is filled with gas and then there's a little bit of air between the top of the tank and the filler door. A hole is formed in the fuel lines. That little bit of air is going to try and push the gas out but... What's going in the new void? Seems to me this would create something of a vacuum that would prevent the fuel from flowing out. I tried a small experiment where I took a full water bottle, opened it, took a small sip, and closed it. Full bottle, small bit of air at the top. Poked a hole near the bottom of the bottle.
The water sort of trickles out... Kind of. Granted it's not a hole-hole I just cut the side of the bottle with the knife to simulate maybe a torn fuel line. Now, I open the cap of the bottle and water flows out, atmospheric pressure pushes it out. Put the cap on, water trickles again. Nothing to fill the void. (Of course this means that when a car is running it has to work against creating a vacuum to get the fuel, but the pump is likely injecting air as it pulls the gasoline though the lines. No operating pump, nothing to push air in.)
The fuel line isn't at the exact bottom of the tank. There's something of a "water line" there and even when the tank is "empty" there's likely something still there that could be gotten to the pump if the car was at the right angle. They only need enough fuel to get the car up to 88, once.
A DeLorean got 18-20 miles to the gallon and had a 0-60 time of around 9 seconds. and 1/4 mile in 14 seconds. So even if they had a 10th of a gallon, like 12 ounces, the car could travel somewhere around 2 miles they only need to travel just over a third of a mile to get to 88. There wasn't 12 ounces of gasoline at the bottom of the tank, in the rest of the lines and even sitting in the engine/injectors (the DeLorean had a mechanical fuel injection, I don't know if that makes it more or less likely for there to be fuel just sitting in the injectors or a nearby reservoir)? Certainly if Doc can build a refrigerator in his lab/barn he could've made a tiny fuel tank to hold the few ounces of remaining fuel they had, calculated an efficient way to accelerate the car and gotten them home.
I dunno, just rambling. Thoughts?
But the vehicle itself always ran on gasoline, how else would Marty have been able to operate it at the end of the first movie?
