Bogus Missionary Puzzler?


#1

First, I think this puzzler is a rerun.



Second: “'All we could find, in addition to our suitcases, was the regular jack, the kind that can jack up one corner of the vehicle at a time; about 30 more feet of that rope that was used to tie all the suitcases onto the roof; and a quart of Philippo Barrio Extra Virgin Olive Oil.”



It’s clear where they’re going, but I’ve never had a jack that wasn’t capable of raising the entire end of the car, both front wheels or both back wheels. What is this “one corner” stuff?


#2

I’ve never had a vehicle whose jack was designed to lift the entire front or rear end of the vehicle. All the jack points I’ve ever seen are on the side of the vehicle, just fore or aft of the wheel in question, and designed to lift that wheel only.

Then again, I’ve never owned a Land Cruiser, or whatever it was.


#3

Maybe my memory is wrong. Wouldn’t be the first time.


#4

I think that one corner of the car could be raised. If the other wheel is blocked, the differential will only let the wheel that is raised spin. The vehicle is put in gear and the rope wrapped around the wheel that is off the ground. Pulling the rope would start the vehicle. I remember reading an old Popular Science magazine which had a monthly series called “Tales from the Model Garage”. The proprietor, Gus Wilson, was a master mechanic who seemed to get out of impossible jams. In one of the monthly stories. Gis was with one of his old customers when the car quit. The battery was completely dead. Gus rigged up the battery from a lantern type flashlight to the ignition system. He then raised one rear wheel off the ground and managed to start the car by turning the wheel. Maybe this is the source of the Click and Clack puzzler.


#5

Correct. That’s the answer Tom and Ray gave on air this morning.


#6

I would worry that pulling at the tire while the corner of the car was raised would just tip the car off the jack.

What I would do is first, find a sapling growing near the side of the car exactly in the plane of the flywheel. Secure one end of the rope to the tree at engine level. With the base of the jack braced against the inside of the fender nearest the sapling, position the jack?s lifting bracket at its bottom position on the jack. Expend just enough rope for it to be taut between tree and bracket, and attach the rope to the bracket with a slipknot.

Work the jack against the resistance of the sapling until the top of the sapling is bent over at about 45 degrees. Wrap most of the rope beyond the slipknot around the ring gear leaving about a foot of rope free at the end.

Take the remaining foot of rope, and let it fall across the front face of the flywheel along a diameter. Mark the rope where it crosses the circumference of the ring gear at both top and bottom. Midway between these marks is the centroid of the flywheel.

Finding the centroid is the key. Centroids are so technological, that the car will now start, even with a dead starter.

Remember that a Toyota LandCruiser isn’t like a truck, where you?d expect to find a truck schoolbag containing truck scissors and a truck ruler for finding the centroid of a half pizza. Besides, you?re now after the centroid of a whole pizza. The centroid should turn out to be at about the center of the flywheel, provided the rope and jack are approximately homogeneous (which they are).

How’s that for beating a dead horse?


#7

Great post! I printed out your answer and have put the copy in the glove compartment. If I ever get into the same fix as the missionaries, I’ll know exactly what to do.


#8

This puzzler may work, but the claim that it should be EASIER to start a car by just spinning a wheel with a rope versus push starting it on the road is definitely bogus. When you push start a car the momentum of the car helps you to turn the engine over, despite the compression of the pistons. If only one tire is spinning the engine is much more likely to just stop the driveshaft rather than turning over.


#9
...the claim that it should be EASIER to start a car by just spinning a wheel with a rope versus push starting it on the road is definitely bogus...
OK, but when was that claim made? I think the claim of the puzzler was that it's easier to start a car by spinning a wheel with a rope than by push starting it in sand THAT IT'S STUCK IN!!!

#10

In the later part of the discussion when Ray claimed it would be easier to start it by just spinning a wheel, it sounded like he was making a general statement about this method vs push starting, not just for this case where the car is stuck in the sand. In particular, he said it would be easy for four people to push start a car, so obviously he wasn’t talking about just this case. Tommy objected that it would be hard to get the wheel spinning fast enough. Ray countered, saying it’s easy to move just the wheel. Well of course it’s easier to spin just the wheel than to move the whole car (when it’s in neutral), but then that comes back to bite you when you don’t (as Will noted) have enough momentum to get through the resistance of the compression stroke when you pop the clutch.

So once again, Ray fails basic physics.


#11

My mistake; I had just gone back and reread the puzzler and answer, not listened to the entire exchange.


#12

I’m really looking forward to the day that a Puzzler gets presented where the solution actually does require the quart of Philippo Barrio Extra Virgin Olive Oil that always seems to be in the trunk.