The Bomb Diagram Message Board: Theories: The Bomb Diagram

By Lapumo (Lapumo) ( - on Sunday, December 03, 2000 - 05:04 am:

Specifically :- the one enclosed in the April 20th letter.
I wondering if anyone thinks Zodiac's drawings of the bus could be significant or maybe he was giving some clue.He seems to go out of his way almost,to give the direction the bus is travelling

Just to state the obvious:-He has "the sun light in early morning" with the road running
perpendicularly.He indicates the direction the bus is travelling by drawing an arrow. South.
I thought at first that the sketch with the "Bus
AND the car contradicted this by giving the direction as north(because of the way the windows on the bus are drawn) but this would put the bus on the wrong side of the road.So why did he feel it important to give us he direction ?
Then he also includes a car in the drawing,which I
suggest was unnecessary,unless he was telling us something.I wonder also,if there's any significance with the way he has the road drawn, a "Ditch" on one side with the road appearing to slope off at the other.He would also need a fair height (as drawn) to the west for his bomb to work
So overall,we appear to have a school bus travelling South to school,along a "Narrowish" road,possibly at some elevation.The further incline to the west.It also seems likely that this would be an isolated stretch,given he talked about shooting the kids as they got out of the bus
he would need some cover and I presume an escape route?.Would the school be in the Bay area?
Would any of this help narrow the search or make sense to the "Radianites"( I apologize for the use
of that awful categorization).

By Hurley (Hurley) ( - on Sunday, December 03, 2000 - 07:52 am:

Hi Lapumo! I have wondered that same thing. I believe somewhere he made a point of saying that the bomb would be elevated enough to affect the bus but not a car.

I had also wondered if the road was a one way direction by looking at the drawing but I don't have it with me right now.

By Ed N. (Edn) ( - on Sunday, December 03, 2000 - 08:06 am:

Lapumo: interesting observation. I had always thought it was just a generalized diagram to show how it works and would be set up, not that it was of the actual place where he intended to "bury the bomb." If it was of the location he had in mind, it should narrow down the possibilities, ie, it definitely had to be in the Bay Area, somewhere within the boundary of the map he provided, and it would have been on the west side of a road/freeway of some sort. Obviously, it was somwhere along a school bus route, and there were only so many back then (might be difficult to find out just where they were at this time, though).

Of course, 30 years later, the area might be unrecognizable, as there has been much development here since 1970. In any case, since I believe that the code actually does have something to do with the map, and that the hint does too, then there can only be so many possibilities. That is, as I pointed out in a previous post, with only 32 characters in the cipher, the directions must be brief and concise (see my post under CHASING THE RADIAN: X Marks the Spot (Continued)), so there can only be so many places one can "bury a bomb" along whole radian, half radian, or perhaps even quarter radian (for instance, say 3.5 or 4.25 radians), as measured from Mt. D.

By Kevinrm (Kevinrm) ( - on Sunday, December 03, 2000 - 09:05 pm:

Looking at the bomb: It's activated by both a clock and photoswitch together. This means that Z would know approximately when the bus would go by and then set it for perhaps a few minutes before. Then when the beam from the sun was broken, the bomb would go off. In theory, this would actually work. In reality, those photoswitches work better when in a situation where it's either totally dark or totally light. He probably did have a spot in mind for this, and I think you are right in that the bus would be heading south. If you look at the Nov 9th bomb plan, it appears that a flashlight or something similar was to be used instead of the sun. This guy didn't give up to easily on this idea, as it was 5 months between diagrams. I've always thought that his use of "jumpers" correctly on the schematic ( where the bombs are hooked up in parallel, Nov 9th ) shows some exposure to at least basic electronics.

By Lapumo (Lapumo) ( - on Monday, December 04, 2000 - 10:11 am:

Hi Hurley! Your referring to the November 9th "bomb sketch",which does explain the presence of the car and the same holds true with this sketch.

Ed,I have read your post reference your radian theory and it makes alot of sense.I do not see this as being something over elaborate on Zodiac's part.Which is probably why he wrote back with the clue -Radians and Inches!.I just see him placing his symbol on the map with Mt.Diablo at the centre.He gives an arrow on the "imaginary north"line to start with,and as you suggest,counts clockwise in radians.When this direction is established the amount of inches from the center "marks the spot"!.I would also agree that numbers are spelt out rather than recorded as digits.
Again,we have the bus heading south to school in the bay area possibly heading back from a round trip journey.Unless there was significant time difference I do not see the bus passing the same route out and back.We know the type of topography required,also it seems likely to be somewhat isolated stretch.Freeways might be excluded because of the amount of heavy traffic, although Kevinrm' post would suggest that this could not be discounted.I can't find it now but Didn't Zodiac mention somewhere something about hoping there wasn't a sunny day because the bomb might go off by accident,this might imply that he did not have alot of control over it once it was set up!It would be interesting to know how many schools and bus routes fit this theory?

By Ed N. (Edn) ( - on Monday, December 04, 2000 - 11:24 pm:

I don't know about Z being concerned about the bomb going off by accident, but he did mention a "cloudy day disconnect" at one point in one of his diagrams, as I recall (my book is put away at the moment).

Z might have indicated the "bomb" was buried in an isolated area (once the cipher was solved and the directions followed, that is), perhaps out in the country somewhere right by a road or freeway, because of the obvious difficulty of trying to bury one in a city. However, it's possible that the whole thing might have been a ruse, because as Tom pointed out, Z said they had until next fall to dig it up (fall 1970), and there were no bombs that went off by a roadway anywhere at that time.

By Lapumo (Lapumo) ( - on Tuesday, December 05, 2000 - 01:16 pm:

In looking back over the references re-the bomb going off by accident,I think,Ed,your quote was the one I mistook for this.I did though find interesting references which answered some of my own questions and may add to the discussion. on page 106 of Graysmith's book we have the this quote:-"Ten thousand school children twenty-eight schools rode Napa County's sixty-five yellow
striped buses.The buses travelled four thousand miles,round trip,in a day,much of it around dangerous curves and through blind intersections.
In some places the country roads are completely deserted,with as much as two miles separating houses.On page 126 we have the following,Ed,"you sly auld Fox":)-"At the bottom of the page Zodiac had drawn a large crossed-circle,five X's moving clockwise on the left hemisphere.This is an extract from the 7 page letter that came with the first bomb diagram,months before we had the Phillips' map.Is this a clue that could have been taken with reference to the map before there was any talk of radians or inches? Does this refer to 5 radians?.I would need to hear a pretty good argument to the contrary that Glen's assumptions on how this should be approached is right.I also think at this stage that your attempts at solving this can't be far from the mark.Rightly or wrongly
I am one of these "poor sods" that believes that there are clues in almost all of what Zodiac has written. Even the lay out of the cipher in this case with what appears to be "north" and the end of the first line followed by the X at the beginning of the second suggests to me it's something like -So many radians from north and then "x" or by so many inches.I really do not believe at this stage it's anything more complicated than that.As far as whether there was ever a bomb or not,I have always believed there was not.Having looked at it closer all I can say is I believe it was seriously considered and that there is a "SPOT" to be found.I think it's likely since he obviously monitored the place that he would leave something there!,

By Ed N. (Edn) ( - on Tuesday, December 05, 2000 - 05:17 pm:

I don't think there was really a bomb either. I think that, if it was a ruse, its purpose was to remove cops from the case and have them ride shotgun in school buses (therefore less people looking for him), and have those left waste time trying to look for the "bomb" by decoding the cipher instead of looking for him.

By Douglas Oswell (Dowland) ( - on Tuesday, December 05, 2000 - 06:55 pm:

I think Zodiac was having a bit of fun with the police, just as Ted Kaczynski was when he jokingly sent a letter to the SF Chronicle threatening to blow up an airplane out of Los Angeles. By that time, Kaczynski had shown the authorities that he was fully capable of carrying out the threat, and the panic that ensued was probably quite stimulating to him.

By Hurley (Hurley) ( - on Saturday, December 16, 2000 - 01:06 pm:

Let's say that the Zodiac was Allen. He was at one time a school teacher. I wonder how all this relates to the school where he taught. Was his own school the target in his mind?

By Esau (Esau) ( - on Sunday, January 07, 2001 - 11:31 am:

It is my opinion that the bomb diagram doesn't necessarily show that the Zodiac had any advanced knowledge of electronics or any schematic specific to any teletype machine. Anyone that had a basic understanding of electronics from perhaps a high school course or researching in a library would have enough knowledge of photo electric circuitry to be able to draw the bomb diagram. Building it on the other hand would be a very dangerous endeavor because the photoelectric switches using the sun and moving vehicles as the light and shade sources would be very undependable at best making it a very unstable device. That might be why it was never built. The use of fertilizer and stove oil as an explosive mixture would be common knowledge to anyone that has demolition experience possibly from the military or from reading underground magazines that use rogue military extremism as a subject.

By Michael Mc (Michaelmc) ( - on Wednesday, January 10, 2001 - 03:14 pm:

Or even haveing lived on a farm. Anfro is a common explosive for stumps ditching ect. Cheaper that dynamite. You would still need dynamite to set off the charge however.


By Esau (Esau) ( - on Wednesday, January 10, 2001 - 05:42 pm:

I hope I'm not encouraging any Mac Veigh types but all you need to ignite an amonium nitrate/diesel bomb is intense heat (fuse), electrical pulse (battery), or another explosive (det cord or blasting cap). I almost got killed with the stuff when I was involved in a demolition project in the Cleveland National forest with the USMC.

By Oscar (Oscar) ( - on Wednesday, January 10, 2001 - 11:21 pm:

Thank you for this valuable information...I will put it to good use. HEE HEE HEE HAWW HAWW MWEEEEAA!!
"Be afraid, be very afraid"

By Michael Mc (Michaelmc) ( - on Thursday, January 11, 2001 - 02:49 pm:

I have used it many times down on the farm. The standard method of detionation is with low grade ammonia based ditching powder. ANFRO is really not that easy to fire.


By Howard (Howard) ( - on Friday, January 12, 2001 - 01:27 am:

Lapumo-I thought the car was in the illustration to show that the height of the average car would not trigger the bomb's photoelectric beam, but it would be triggered by a bus because of it's height-that's the way Z supposedly set his imaginary "bomb"(my guess).Books in the 60s had bomb diagrams of all kinds.It looks like the bus is on a road that's near a mountainside and since he mentioned Mt. Diablo,etc. ,could this be the area? The roads in that area fit the narrow road/ditch/mountainside that you see.I've been there several times and it could fit(?).

By Lapumo (Lapumo) ( - on Friday, January 12, 2001 - 06:22 am:

I do not know if there ever was a bomb,however I do believe Zodiac considered it and had an area in mind.Regardless of whether the diagram was an illustration or not it would have to fit a certain
Topographical area.I think Edn's theory on the Map/cipher is pretty close,which is why I brought this up first day,in a hope it may help narrow down the possibilities.Zodiac wrote back with a hint-"radians and inches along radians"which makes me think he was aware that the area in question had not been discovered.
To my mind you have a bus travelling due south to school along an isolated mountainside road.Peter,I see is also looking at this in another thread;he may have something of interest.

By Peterh (Peterh) ( - on Friday, January 12, 2001 - 10:23 am:

Yes, I think I do, too. See Theories: the Unit Circle I have a spot that fits with one reasonable interpretation of the Mt. Diablo letter, the diagram and Little List Letter clue. It is on the Diablo/SF ray of the Penn radian exactly 10 miles (1 inch on the Phillips 66 map)from Mt. Diablo, on a north/south road in a rural, hilly area. What I don't know is whether the west side of the road at that point is an embankment or hillside sufficient to raise the photoelectric device to the level shown in the diagram (which I also interpret as necessary to clear a car but not the bus).


By Peterh (Peterh) ( - on Friday, January 12, 2001 - 10:43 am:

32 characters:

By Ed N. (Edn) ( - on Friday, January 12, 2001 - 10:14 pm:

Good idea, however, three characters (the triangle, and the letters "C" and "O") each occur twice and it is probably a safe assumption that they have the same value. The triangle is character #'s 2 and 32, C is 1 and 26, and O is 6 and 14. Thus, in

One inch west of Mt diablo on the radian
characters 2 and 32 should match (they do), 1 and 26 should (they don't), as should 6 and 14 (they don't).

It's a good effort, Peterh, and I think that Z meant something along those lines or the line I suggested some time back. The question I have is, what radian, and what leg of the radian does one measure one inch from?

Don't give up, just bear in mind that Z may have provided a form of check-off system with those three repeating characters.

By Peterh (Peterh) ( - on Saturday, January 13, 2001 - 11:57 am:

Thanks for the comment. I'll basically leave it to the cryptographers, as this was pretty much a random shot at the cipher. If I take this any further, it will be to play around with the mathematical suggestions of the Mt. Diablo letter and map, and the John's letter clue. In fact, I'm a little disappointed that no one has commented on my application of the Unit Circle in that thread. Geez, I even came up with at least one stretch of road that fits at least three of the four essential elements of the diagram: north/south orientation, rural location, and it's on the radian. The only thing left to determine is whether the west side is elevated. Of course, if there were 30 year old excavations, a few rusty clock parts and some wing-walker footprints in the area, that could mean something, too. And no one even wants to comment, much less take a look? I'd be out there with a metal detector this weekend if I could . . .

As for the cipher itself, I would note that in any 32 character string of the English language, its pretty rare to have so few repeats as in the Mt. Diablo cipher. I think its much more likely -- if it really is a consistent code at all -- that there are multiple representations of several letters. Otherwise, we have a message of 32 letters with no more than two e's or s's. How likely is that?