# How can I get my DeLorean to 88 miles per hour without a train?

I got pulled into 1885, just like Doc and Marty (Or I'm one of them, assuming I can get IP rights :)). I need to go back to the future, which means that I need to get my Ford Pinto time machine up to . . . well, you know, 88 miles per hour.

The thing is, I don't have a train handy, and the car can't propel itself.

Is there anything I can do to escape? What can I do?

Constraints: The car must be occupied by time travelers, who must survive the experience. There is no unobtainium nor anything else not available historically. Ideally, the location is constrained to wherever Hill Valley, CA is geographically, but presumably you can transport a Ford Pinto anywhere by horse/ship.

• Any particular reason for it being a Ford Pinto? Oct 23, 2015 at 1:44
• Why are you stuck, because you cut your fuel line? Is there a time constraint here? If not, why wouldn't you just spend the time to rebuild the engine to use another fuel source? Or actually buy crude and refine some gas? Or grow some corn and make ethanol fuel. Oct 23, 2015 at 18:13
• @Zoredache - Time constraint: no. Knowledge of cars lacking 100% - yes. I know how to drive them, not the parts or how to fix. Oct 23, 2015 at 18:21
• If I recall from the movie, the vehicle travels an arbitrary amount in time, but in space it only travels where it would have had no time travel been involved. This means that, when it arrives at its destination, you have to make sure it's moving along a safe surface. No "drop off a cliff and hit 88MPH on the way down"; you'd just die in the future. And, if you build a ramp, you won't have a ramp there when you arrive, so you have to plan accordingly. Oct 24, 2015 at 12:57
• @reirab The movie never mentions the movement(s) of Earth, so adding that criteria is inappropriate. (essentially pre-assuming that all that math has been sorted out such that it is no concern) That aside, using a "should be there" location or a construct with "leave it alone" directions is something that nature feels (rightfully) free to ignore. Oct 25, 2015 at 14:24

While the slope is quite obvious, I think you need something cooler, and more technological, to accelerate your Pinto.

You don't have a steam engine (and no fancy colored steam), but you have horses and oxen.

Those, though, are a bit on the slow side. But they are strong. Given enough horses or oxen, you will find yourself with plenty of power, but still not nearly enough speed.
Good thing you have the doc around, because he knows pretty well that there are nice technical ways of converting power to speed. One would be a gear box, the other would be a lever.

While I cannot think of a convenient and low-tech way of equipping an oxen with a gear box, I can think of levers, angular momentum, ropes.
And a spinning top.
So, we will build a centrifuge. In the center we have a drum with some length of rope wound about it, and on one conveniently long arm we have the pinto, and a counterweight on the opposite side.

Now, provided you can get a team of oxen to pull on the rope, you get the pinto spinning quite fast.
88mph tangential velocity should easily be achievable, and the moment you jump you are automatically released from the centrifuge (since it does not travel with you through time). You may want to choose a location where you will have enough space to brake, though.

The biggest advantage of this solution is that it is a lot more steampunk-hipster than just paving a slope!

Assuming a team of oxen will move at a speed of 2 km/h, and our Pinto is supposed to reach 141.6 km/h, the ratio of arm to drum is 70,8/1.
If we further assume the drum to have a diameter of half a meter, we get a radius of 25cm. Thus, the arm of the centrifuge needs to be 17.70 meters.
For a safety margin, make that 20 meters.

Or, you can reduce the drum diameter, or replace the oxen by horses. The much higher speed of the horses (assuming they should be able to reach 10 km/h) even when pulling this weight), we get the length for the arm at 5 meters when the drums radius is still 25cm.

All in all, I would say this is completely feasible.

• What would happen when the DeLorean leaves the contraption behind and suddenly there is no weight of the car to counter the counterbalance. The system becomes unstable and counterbalance (and possibly oxen) go flying.
– user13985
Oct 25, 2015 at 6:42
• @Stacey the question only required that the time travelers must survive. It didn't say anything about oxen or bystanders. Oct 26, 2015 at 9:36
• @Burki - you might want to rethink this. Centrifugal force on the Pinto just prior to release is 77 g's. mv^2/r, and all that. In turn, this implies a maximum tension on the arm of about 400 tons. Consider what this means in terms of both arm construction and bearing construction of the hub - in 1885. Oct 26, 2015 at 19:14
• The vehicle isn't moving at a consistent speed - there's a gradient. The outside of the vehicle will hit 88 before the inside of the vehicle. You'll need to account for this in the time equations, and my guess is that having the vehicle the same speed on all of its parts will change how it operates. Imagine, for instance, getting the right half up to 88, but falling just short on the left side when the oxen fail - does half the car time travel? In short, I don't think this method is something worth trying - all the existing footage shows the car going straight during the transition. Oct 26, 2015 at 19:23
• @WhatRoughBeast When do you do this? When the first parts of the car start going 88? When all the parts are going 88? We've not had a situation in the movie where the car is going 88 or faster than 88 when the time circuits are enabled, it's always the circuits first, then the speed. If you detach before 88, you need some extra force to get past 88. If you wait until some part of the car reaches 88 you have the same problem I described above. If you're releasing on a hill or something, then the rotary machine is redundant - use a hill for the whole thing. Oct 26, 2015 at 22:00

Its 1885.

Rockets. Black powder's pretty common, and I believe guncotton was a thing, if doc could find the materials. Stick a load of disposable, simple paper tubed rockets on the back of the car to give it a push. Could even use mr fusion moved sideways to stick the rockets in.

Rocket science isn't just for the 70s ;).

Not quite a delorean, and somewhat more modern rockets but...

Something like that would be pretty impressive. (Mythbusters Jato episode. That's what inspired this...)

• +1 This is what the U.S. Air Force does when they want something to go really fast on the ground. They have managed to get a bit faster than 88 mph. Oct 25, 2015 at 2:22
• ...and then it spun end over end and crashed. BUSTED! Time travelers have to survive. So, uhh... no ramp. Oct 25, 2015 at 23:07
• Mythbusters needed considerably more speed, and had a front heavy car. While I didn't consider the use of rails, it might work here. I also invoke the anchient and most honorable roman law of "narratvium handwavium" Oct 25, 2015 at 23:12
• @reirab Rocket sleds are rail vehicles though, the question explicitly mentions no train being available. This would be stretching it :-)
– Mast
Dec 23, 2015 at 9:16

Using information from the comments, updating my info.

Gravity. you need to get on slope that is very steep but has a gentle curve at the bottom. Terminal velocity is about 260mph for the car, so you will need to be on an almost vertical surface to reduce the ground friction enough. My math is rusty but I think about a 500 288 ft drop should get you pretty close. Of course you will have to worry about where you are ending when you jump back to the future.

Kind of like this water slide.

• It's a start of a good idea, but I don't thing 500ft water slides were a thing in 1885? Oct 23, 2015 at 1:32
• @DVK it was supposed to be more a visual of the path needed... Might need a little help on some cliff side... Oct 23, 2015 at 1:34
• They wouldn't need to be I imagine. A steep incline that has been smoothed down would be enough. I'm thinking somewhere icy in the mountains would work. You would just need to hire a few roughnecks to smooth the terrain down, and probally a few hunters who know the area who can help you find a suitable spot. Oct 23, 2015 at 1:34
• @BryanC.Winter But then you end up in 2015, hurtling down the icy slope of a mountain in a Ford Pinto. Oct 23, 2015 at 5:00
• FYI, terminal velocity for a 1970-ish Ford Pinto is about 262 mph. As noted in my comment to HDE 226868's answer, you don't need a crazy amount of incline to do it, although you would need a pretty smooth road. A 45° angle like shown would require about a 288 ft (87 m) height. Of course, you'd want enough room at the bottom to level out. You need about 7.238° at the end to keep a terminal velocity of 88 mph. Oct 23, 2015 at 6:50

Hill Valley is, apparently, somewhere in the Sierra Nevada range in Northern California. That fact, as well as its name, should make it clear that the region has an abundance of hills, which are handy little devices capable of converting potential energy into kinetic energy. All you have to do is bring the DeLorean to the top of a hill and give it a slight push. You'll be able to clear 88 miles per hour with no problem.

How can you get the DeLorean up there, though, given that the car apparently can't propel itself? Well, horses are apparently allowed, so you might consider tying a few to the car and lugging it up a convenient mountain.

My inspiration here is from downhill skiing, where some skiers can hit 90+ miles per hour. Speed skiers can go even faster, on courses one kilometer long. If you can minimize friction, then you can go pretty darn fast with this car.

The conversion is $$mg\Delta h=\frac{1}{2}mv^2\to v=\sqrt{2g\Delta h}\to \Delta h=\frac{v^2}{2g}$$ This gives me a vertical drop of about 80 meters in order to reach 88 miles per hour, assuming that virtually no energy is lost to friction. Even assuming large frictional losses, it seems like this is doable.

• Would you please be able to expand on the physics side showing the "no problem" angle? Oct 23, 2015 at 1:48
• You need to take air resistance into account. I'm stealing data from a couple different years, but a 70-71 Ford Pinto is about 1000 kg, 0.5 coefficient of drag, 1.9 $m^2$ surface area. Using some spreadsheet integration, a 7.25° hill (12.7% grade U.S.) would get you to 88 mph in about 0.97 miles (1561 m), with a total of 646 feet (197 m) descended. Going a bit steeper, a 10° hill (17.6% grade U.S.) hits 88 mph in 0.46 mi (733 m) after descending 417 ft (127 m). A vertical drop would hit 88 mph after about 281 ft (86 m) of falling, assuming the nose kept pointing down. Oct 23, 2015 at 6:29
• Sources: Mass/Cd (have to click for more specs). Frontal area. Also, according to this site, there are several 30%+ grades between San Diego, CA and San Francisco, CA, so it stands to reason Hill Valley (presumably a bit east of San Francisco) could have 13-17% grades. Oct 23, 2015 at 6:40
• @MichaelS especially with a 19th century road surface you'd need to consider rolling resistance -- and whether the car would fall to bits going over a road bullt for <20mph wheeled, with all its ruts and bumps. Oct 23, 2015 at 10:34
• Well, there's just one problem with this solution: He has no DeLorean, but a Ford Pinto. So he'll not be able to get the DeLorean up a hill for lack of availability. Well, thinking again about it, the Doc's DeLorean should also be there (it being the same year and location), so maybe he could convince the Doc to exchange the DeLorean for the Pinto. Assuming he's in the correct timeline, of course. Oct 24, 2015 at 9:20

Einstein's theories state that motion is purely relative, so simply change your reference frame to something other than earth, like the moon or a speeding bullet for example. Now suddenly you're actually traveling much faster than 88 mph!

The only problem is that the static electricity produced by the fast moving air is required for the cool blue electricity of 1980's special effects. For this, simply find a bunch of wool blankets (very common in the 1800's) and rub them furiously on the car's body while the Doc redirects the flux capacitor's motion detector.

• Mind you, reentry is relative to your frame of reference. Use the moon, and if your reentry happens at the right time, you could find yourself breathing vacuum.
– user11864
Oct 23, 2015 at 14:48
• @Sobrique My point exactly. How do we trick the reference frame? Maybe the solution is to spin the wheels really fast, or build a fan to push the air around it, or maybe just set it out in a tornado. Bottom line is: speed isn't absolute, so this mechanism must be "trickable" somehow. Oct 23, 2015 at 14:53
• It pretty much is absolute, for all the reasons we still use cars to move around the planet. Oct 23, 2015 at 14:55
• @Sobrique - Think about it this way: if you are in a soundproof/shockproof room, how do you know how fast you are moving? You would be able to detect changes in this velocity, but it's impossible to know your speed. You could open the door and see the world passing by near the speed of light. Or maybe that's just a hologram. It's impossible to know for sure. Oct 23, 2015 at 15:29
• @JamesWatkins Not knowing the reason for the speed requirement nor the physics involved I don't think we can make an argument such as yours. After all, pre-Einstein everybody would have thought you insane to care about the location of your reference timepiece--a clock is a clock, moving it can't change it's speed! Oct 24, 2015 at 4:39

# Super Easy

Get a counterweight and a rope; attach the weight to the vehicle and have your beasts of burden push it off the edge. There are plenty of "edges" in San Francisco.

• Why not just push the car over the edge? Extra weight won't help it fall faster. Oct 24, 2015 at 18:58
• @JamesWatkins because all these gravity-based answers assume the slope will still be there, and clear of obstructions, when the delorean arrives. Likewise, the answers that throw the car off a ramp and hit crossover speed airborne forget that the car can't yet fly. Oct 24, 2015 at 21:43
• Sorry, I misunderstood. It would have to be a very long rope to overcome friction, but otherwise it's a pretty good, creative answer. Oct 24, 2015 at 23:36
• They can even use Shonash Ravine and the uncompleted railroad track. Doc says it's straight and level and will be a very smooth ride. Oct 26, 2015 at 2:40

Gears!

Similar to Burki's answer but simpler:

You just need gears and two really long ropes. One to tow the Pinto and one for your team of horses to pull.

With the gearbox, wind one rope around a cylinder attached to the large cog and yoke/couple to your team of horses. Tie the other rope to the cylinder attached to the small cog and tie to the towing eye of your car.

According to the Internet, the average horse galloping speed is 25-30 mph, granted they'd be slowed by having to pull a car, but enough horses could presumably minimise that work. So I suppose a gear-tooth ratio of 4 or 5 to 1 would do the trick.

Screw steam-punk, it's clock-punk all the way!

• Possible, yes. But it wouldn't look enarly as cool! :-) Oct 23, 2015 at 10:54
• Big, strong gears might be hard to manufacture. I'd use a pulley. Same logic, though. Oct 23, 2015 at 17:42

Well, earlier through my experiments with time travel (or later?) relative to the accident, I had received a letter, that's been sitting for over a century at the mail office, awaiting the right time.

Dear past me,

I got myself in a pickle.

Could you please get a canister of fuel and a new fuel line for DeLorean, go 6 miles due north from the town hall of Hill Valley, drop in to September, 8th, 1885; locate a three-pronged cactus and leave the items under it, please. You'll be very grateful once you're me.

Faithfully,

Future you.

I had insightfully followed the instructions to the dot, then nearby forgot the event until the unfortunate arrow-in-fuel-line accident, when retrieving the items from the appointed location was trivial.

• VERY nice solution! :-) Oct 26, 2015 at 15:46
• that would create an alternative timeline Oct 26, 2015 at 17:34
• @njzk2: Possibly so, but not paradoxical. As long as I don't create any weird loops E.g. I don't just drop the note along with the canister, to be sent, and I actually go survey the site instead of the idea of three-pronged cactus being there spawning in my head, nor try to modify the sequence of events, e.g. changing the wording of the letter, it's all fine. If all elements of the puzzle have a clear origin and end outside the loop, there's nothing wrong with it. And discovering time travel I'd definitely spend some time solving "future me's" problems.
– SF.
Oct 26, 2015 at 17:49

I hate to be a cold blanket, but the selected answer (centrifuge) requires a fairly monumental effort.

To begin with, the choice of arm/hub measurements is marginal. At speed (88 mph = ~40 m/sec), the centrifugal force per unit mass will be $$F = \frac{v^2}{R} = \frac{40^2}{20} = 80\text{ N/kg} = 8 \text{ gs}$$ and this will be extremely difficult for the driver to accommodate. Furthermore, the tension on the arm produced by a roughly 1,000 kg Pinto will be on the order of 8,000 kg, or 8 tons.

But let's go with it for a while. Now, in 1885 the obvious choice for arm material would be sections of railroad track, which came in standard 11 meter lengths Since the thermite welding process was well-known, welding 2 rails together to form an arm 20 meters long seems reasonable. Rail standards were established in 1893, so the use of railroad rail in the range of about 50 lb/yd seem reasonable. This will set arm weight at about 3000 lb or 1400 kg, or just about 1.4 times the weight of the Pinto. 50 lb/yd (25 kg/m) implies a cross-sectional area of about 32 cm2, or .0032 m2. Yield strength for mild steel is about 250 MPa, so the yield strength S of a rail is $$S = {250 \times {10^6}} \times .0032 = 8\times{10}^5\text{ N}$$ or about 10 times the required load. While it might be tempting to consider using something like wood instead of steel, making a structured beam of the length necessary would be something of a challenge.

The moment of inertia of the Pinto is $$I_P = mr^2 = 1000\times {20}^2 = 400000 \text{ kg m}^2$$ and the moment of inertia of the arm is $$I_A = \frac{mr^2}{3} = \frac{1400\times {20}^2}{3} = 180,000 \text{ kg m}^2$$ Total moment of inertia is then about 580,000 kg-$m^2$. Assuming the counterweight is substantially similar to the load arm, the total moment of inertia becomes 1,200,000.

The question now becomes, how fast does the centrifuge have to accelerate? Angular velocity is obviously $$\omega = \frac{v}{2\pi} = 6.3 \text{ rad/sec}$$ Assuming 100 feet of rope wound on the hub (about 20 turns or 120 radians), and that a heavy ox (900 kg) can produce a pull of 2/3 its body weight over short distances and low speeds, this provides a torque of 150 kg$\cdot$m per ox. Then the angular acceleration per ox will be $$\alpha = \frac{T}{I} = \frac{150}{1,200,000} = 1.25\times{10}^{-4}\text{ rad/sec}^2$$ Ignoring air friction, $$\theta = \frac{\alpha \times{t^2}}{2}$$ and $$t = \frac{2 \theta }{\omega } = \frac{2\times120}{6.3} = 38\text{ seconds}$$ To reach 6.3 rad/sec in 38 seconds will obviously require an angular acceleration of about .17 radian/sec2. And now we get to real problem - torque. With an angular acceleration of .17 rad/sec2, and a moment of inertia of 1,200,000, the torque required is about 204,000 kg$\cdot$m, or about 136 oxen. The actual force provided to the hub is $$F = \frac{204,000}{.25} = 816,000 \text{ kg f} = 1.8 \text{ million pounds}$$ Another problem arises simply with attaching the oxen to the hub. As established, each ox is pulling with a nominal 600 kg of force, or 1320 pounds of force. This site establishes a working load limit for 1 inch manila rope of 1160 pounds, with a breaking point of about 8,000 pounds. Attaching 100+ 1-inch ropes to a 1/2-meter diameter cylinder is going to be challenging.

• Since you didn't offer a solution, I can't accept. But definitely +1 Oct 27, 2015 at 2:22
• Interesting. I guess we can take the feasibility of the mechanical construction as a given. Now for the torque: if i am not mistaken, a longer rope will give the oxen more time to accelerate, thus reducing the torque? Would that be about right? I will provide a new answer within the next days, but i need to understand that correctly. Oct 27, 2015 at 20:14
• @Burki - Please reread and start thinking practically. Consider that winding 100 1-inch ropes on a cylinder will require the cylinder to be at least 8 feet long, and the individual lines will tend to interfere and jam as load is applied. Plus the cylinder has to rotate freely with a million pounds of force applied to it. That sort of bearing is not exactly off-the-shelf today, let alone in 1885. The feasibility is not only not given, I suspect it is not possible. Oct 27, 2015 at 20:19
• I re-read your post. There is something substantially wrong i think: the load on the rope depends on the force with which the oxen pull. when they pull with less force, the acceleration is slower, and the tensile force in the rope is lower. They will still reach the desired speed, it will simply take some more time. But anyway: i will create a better solutiona s soon as i find some time. Oct 28, 2015 at 8:11

The number 88 was chosen merely because it fills the digital display. So build a digital display that can only show 0 or 1 and only two characters. Surely you could get the car to 11 mph by horse power.

When in doubt, redefine the problem :)

• Later I realised - make it a single digit display and you only have to push the car up to 1 mph. Oct 24, 2015 at 10:09
• Then wouldn't zero fill the display? Oct 24, 2015 at 13:48
• @JamesWatkins yes, but Doc may not have sanity checked his inputs, resulting in potential divide-by-zero errors. Oct 24, 2015 at 21:40
• @JamesWatkins Also, if the delorian can "shift" at a speed of zero, what's to stop it continuously going? Plus there'd be no flaming tyre/tire tracks if the forward velocity is 0 Oct 24, 2015 at 21:41
• Mightn't be too easy to build a digital display in 1885... Oct 27, 2015 at 9:49

The Pinto could simply be run on gasoline. Since whisky exists in 1885, so does the technology for distillation. All that is required is a suitable feedstock. There are tar pits in California. Given enough time, one could:

1. Collect a useful quantity of source material
2. Build a small cracker and fractional distillation rig
3. Operate it long enough to produce a tank full of gas

Alternatively, the Pinto could be run on ethanol (use pure alcohol not whisky i.e. ethanol + water). E85 cars are a reality today - the only issue is chemistry between ethanol and the fuel system surfaces it contacts. Mostly, the processes involved would be slow and not relevant to making a quick escape. The primary reason E85 exists as ethanol + gasoline is to render it unpalatable for human consumption. This is the same reason washer fluid contains additives. Although the gasoline in E85 helps starting/drivability, 100% ethanol works, and adequately high-proof alcohol could easily be produced with 1885 resources and technology.

BTTF2 imposed a time constraint - just a day or two - and a bit of license - blowing up the engine (needed to introduce all the drama with the train and rescued damsel in distress). Unless you plan to blow up your Pinto engine for the sake of added drama, no reason you couldn't run it on ethanol.

• The question states that the car can't propel itself. Oct 25, 2015 at 22:14
• Ah yes... so how did it get to 88 MPH in order to arrive in 1885? Oct 25, 2015 at 22:20
• Possibly in the same way that it will get to 88 miles per hour in 1885. Oct 25, 2015 at 22:31

Drop it off a cliff

There's no need for the time-travelers to devise any complex mechanism to get themselves up to speed using 1885 technology. Throwing it off a cliff will work.

Math-wise, it takes an object about 4.1 seconds of freefall to reach 88mph if air resistance is ignored. So let's say we're talking about 6 seconds (or less) of freefall with air resistance. That means any cliff with a vertical drop of 200m or more should be sufficient.

So it's just a question of finding the closest 200m+ cliff and shoving the car over it. Possibly with the addition of a small ramp to ensure it has enough forward momentum to avoid impacting the side of the cliff as it falls.

You could probably get away with closer to half that height, but I'm allowing a large safety buffer (50%) for frictional losses. I assume the safety of the time-travelers is the top priority. And a taller cliff gives them a better margin of safety.

With one caveat

The trick, of course, is that the time-travelers need to write a letter to their trusted near-present-day contact, and leave strict instructions with someone in 1885 to see that it's delivered to the correct person at the correct time. The letter should of course instruct the modern-day contact to waste no time in devising a deploying a device that can safely catch the falling time machine when it arrives.

It's important to think fourth-dimensionally. Because then it's the future's problem to worry about.