At that point, Doc was fairly panicked about altering history. He thought they really needed to get out of 1885 before they could damage the timestream. He wasn’t very rational about it.
No, as MIcaelson and Morley proved, it was the velocity through the ether. :rolleyes:
It’d be very expensive and Doc Brown probally would’ve needed to place a special order for it.
I would cite my source of the Time Machine, but clearly thou ist the predecessor of a morlock and won’t understand it anyway.
Here’s my bit of fan-wankery:
The flux capacitor is electrical, but needs the 1.21 jiggawatts to sent the DeLorean throught time.
The 88 mph, while an unexplained plot device just to give the car a reason to speed and look cool, could actually provide a fictional, rational answer. That you need to be under a specific amount of acceleration as a necessity for the flux capacitor to work… Thus making time travel possible! You can picture it as an inertial calibration, that if you were to trigger the FP any slower or faster, you’d loose accuracy in time and space, ending up in the early Cretaceous, but somewhere on the other side of the galaxy in interstellar space.
So really, it does travel through space as well, but only as to keep their momentum and bearing over the years. What better way to do that than to lock into some universal/inertial constant the Doc discovered as a calibration? Or something.
So, in this scenario (which is a cooler justification than just a mere, arbitrary trigger for the FP, IMHO) the rotation of the wheels or axle doesn’t matter. You have to be undergoing acceleration at precisely 88 mph (luckily that speed is easily approachable for a sports car).
Perhaps they’d thought of that, but instead of going through all that trouble, they tried the moonshine first, not knowing it’d totally blow the manifold out. (at least, it’s a good enough excuse to spackle over that loop hole).
What about lard or vegetable oil as fuel? Or is that for diesel only?
Also, they have a Mr Fusion… Use some if that juice to separate hydrogen and oxygen from water, and… Well, there’s the problem of needing cryogenic temperatures and pressures to make liquid fuel. Although he did make that humongous ice cube maker.
If the Delorean doesn’t actually have to move, couldn’t they hook some gears to the axles to increase the number of rotations? A small motor strong enough to turn the axles (the axles rotate, right? I don’t know much about cars) hooked to a gearing system. The car doesn’t need to move at all. Put the set up in the area that would become Doc Brown’s back yard and poof there you’d be, safe and private, in 1985.
StG
I like cmyk’s fanwank that it has to be accelerated to 88 MPH for some reason to function.
I think the Delorean needs to move, it looks like the flux-capacitor opens a portal, and the car moves through it. It could be that the portal is only open long enough that the Delorean has to be moving at 88mph to avoid the portal collapsing on it.
Yeah. I don’t think it would work if you put the car up on jackstands.
[technobabble fanwank]
The temporal displacement system relies on being in an accelerated reference frame relative to Earth’s frame. Due to engineering limitations in the construction of the the time circuits, the maximum power that can be safely delivered to the flux capacitor during the field generation phase is slightly more than 1.21 gigawatts (allowing for a small safety factor). At this power level, the minimum velocity at which the capacitor must be moving in order to trigger the formation of the displacement field is 88 miles per hour.
[/fanwank]
I believe this explanation has several advantages.
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It accounts for the 88 mph requirement in a sci-fi-plausible sounding fashion.
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It accounts for the vehicle being displaced to 1885 without requiring extreme accelerations. With the full power of a lightning strike hitting the flux capacitor, it was able to trigger the field at a much lower speed–a speed reached as the flight circuits got zapped and send the car into a spin and fall. Doc even describes the effect as a “gigawatt overload”.
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It explains why the displacement to 1885 fried the time circuits, when the original return to 1985 didn’t–Doc’s rig on the clock tower obviously had multiple ground paths, so the time circuits didn’t take the full hit from the lightning strike.
Please refresh my memory. The time circuits were fried traveling to 1885?
I may misunderstand you, but they did not repair the Deloreon that was hit by lightning. They used the one that had a gas leak and blown…carburetor?
Yes–in its first displacement to 1885, that is, not when Marty took it back again.
Once 1955-Doc and Marty retrieved the stored DeLorean from the mine, Doc had to use the schematics 1885-Doc had provided to rebuild them from 1955-era components. That’s why the car had the clunky vacuum-tube contraption on the hood when Marty took it back to 1885. Remember 1955-Doc peering at a chip through a magnifying glass and disparaging its Japanese origins?
You’re just not thinking fourth-dimensionally. 
It’s the same car. It just happens to be in multiple places at once*. Following the DeLorean’s timeline:
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At the end of BttF II, the DeLorean is struck by lightning while Doc is flying it. This fries the time circuits and the flying circuits in the process of sending the car back to 1885.
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Once the timeline change propagates, the DeLorean with the blown circuits has been sitting in the mine since 1885.
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1955-Doc rebuilds the time circuits with vacuum tubes and other period components, but can’t fix the flying circuits.
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Marty takes the DeLorean with the repaired circuits back to 1885, where he damages the fuel line. They try running the car on whiskey, which ruins the fuel injection system.
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They push the DeLorean up to speed with the train, and it returns to 1985 with Marty, where it is destroyed.
*Technically, during the events of BttF II, the DeLorean was in four places at once: hidden in the mine, hidden at 1955-Doc’s house, hidden under brush behind the billboard, and wherever 2015-Biff hid it. We never actually see Marty experience a period when this is the case, however, because 1985-Doc and 2015-Biff are both gone in the DeLorean before 1885-Doc’s changes propagate along the timeline to cause the DeLorean to have been in the mine all along.
My head hurts now.
Guys, 88 mph is a speed, not an acceleration. Clearly it doesn’t require that much acceleration to get going since in pretty much every instance of time travel, the Delorean very gradually creeps its way up to 88 (the one exception is when it’s struck by lightning in mid-air). Since I could drive by a stationary Delorean at 88 mph and have it appear in my frame of reference to be going 88 mph, it must have to be calibrated to the frame of the Earth’s surface for some reason. I guess that’s what keeps it grounded in the same spot on Earth while going to different times.
Ah, thanks.
Was the Delorean in two places at once when Marty went back to get Doc?
Yes, it was in the mine (with still-fried time circuits) when Marty showed up and hid it in the cave with the bear. It remained in the mine the whole time it was in Doc’s smithy and so forth.
That’s a cute idea. The locomotive surely has the horsepower to do it, although it depends a little on how much wire rope they can come up with. If the loco needs, say, a quarter mile to get up to 22 m.p.h., the DeLorean will be a full mile away from the start point when it hits 88, meaning that there’s a full mile and a quarter between the two, and since the wire rope has to stretch that distance four times to get four times the mechanical advantage, we’re talking about a minimum of five miles of wire rope, either in one piece or welded, spliced, or otherwise attached smoothly enough to feed through the pulleys. You’d also need some pretty ridiculously strong pulleys and pulley anchors, but that should be doable.
It’s worse than that. When Marty goes back into 1985 on the train trestle, he makes it because the tracks are in the same place. However, if he’s falling when he transits, he’ll wind up in 1985 under the trestle, falling at 88 mph through the wooden supports! He won’t survive that! Even if he ejects, he’ll be ejecting directly into the support structure of the trestle.
Think about this. Obviously anything within the car goes with it into the past or future.
Parts attached to the outside also go with it. The bumper, or the tires, for example. Perhaps because they are physically attached to it.
Things inside - people, dogs - aren’t welded or bolted yet still go along. Why? Is this simply because they’re touching the car? Then why doesn’t the ground that the car is touching come along. Hell, why not the whole planet, since it is touching the car?
Maybe this is where the 88 MPH becomes important.
Maybe the machine brings along anything that is physically touching the flux capacitor (or touching something that is touching the flux capacitor, or touching something that is touching something that is touching something that is touching the flux capacitor, ad infinitum).
If the car is sitting still with the FC on, the entire planet is part of the physically contiguous time machine, since it is touching the tires. The problem (the saving grace, actually) is that the time machine doesn’t have enough power to move this much mass through time, so nothing happens.
The movement through time, when it can occur, happens very rapidly, in nanoseconds or less (I’m not about to attempt the math). So the machine has to consist of a small enough mass for at least that amount of time.
Now as it’s rolling along below 88 MPH, it’s always that case that some of the molecules in the tires are in contact with some of the molecules in the ground for longer than the time required so the “machine” is never light enough for a long enough period to be moved through the fourth dimension.
88 MPH is just fast enough that no part of the Earth is contiguous with the car long enough to stop the move through the fourth dimension.
When the car was in the air, it, plus the air molecules against it, weren’t too much mass for the FC so, when the FC was activated by the lightning it was able to move the car through the fourth dimension.
In the first movie, Doc mentions that the stainless steel construction of the DeLorean helps with the flux dispersal. The definition of “flux” that appears most relevant refers to the strength of a field of force in an area. To me, this implies that the flux capacitor establishes a temporal displacement field that is defined by the shape of the car body. The external wiring harness and other paraphernalia are positioned in such a way that they could plausibly be used to extend the field away from the body in certain areas, such as to cover the tires. We might even posit that it doesn’t cover the tires entirely, shaving off a small part of the tread and leaving it behind as fire trails each time, to avoid accidentally impinging on the ground.
appleciders, that’s an excellent point, and one I should have considered. Looks like I wasn’t thinking fourth-dimensionally enough, either.