Because of the subtle and often difficult to see, the salient engineering innovations are best documented on a feature-by- feature basis - rather than on a car-by-car description.
I found the most comprehensive resource to be The Artifacts of R. Buckminster Fuller, which contains the most pages, 96-184; good, high resolution photos and photographic reproductions of engineering drawings and blueprints not found in other works.
Many of the engineering drawings are identified with labels which indicate which Car (1,2,3,4,5,) they refer to although, the drawings are not always immediately adjacent to the Car Version they go with.
Buckminster Fuller's Dymaxion Car was a combination of visionary genius saddled with the restrictions of metallurgy, powerplant evolution and the realities of the "off the shelf" automotive components available to him in the early 1930's.
Fullers vision was to design a "Flying Car" powered by turbo-jet engine(s) which would lift vehicle and passengers into the air - jump jet fashion. Since British inventor Frank Whittle would not complete a working gas turbine engine until 1936 - some three years after the Dymaxion Patent submission.
Several drawings of a "customized" 177.5 LB, Continental, straight four cyl. 1226cc, flathead engine with 12.10 HP is shown dated 7-22-30 which places it in the early stages of design. Clearly, this engine was too small for the Dymaxion and Fuller simply "made do" with a Ford flathead, V-8 engine, transmission and rear axle.
I will segment or arrange this critique into the following sub- divisions which were the primary focus of Fuller's design and experimentation: (1.) The "A" frame supporting the rear wheel, (2.) the Steering mechanism itself, (3.) the suspension (springing) adaptations, (4.) the engine supporting sub-frame, (5.) the various power plants and (6.) Various features attributed to the cars - some real and some visionary.
Because the references will relate to various publications the following "Code" will be used.
[] The Artifacts of R. Buckminster Fuller. Page numbers in square brackets []. {} Inventions: The Patented Works of R. Buckminster Fuller and the actual Patent Drawings. References with "curley brackets.{} <> The Dymaxion World of Buckminster Fuller Page numbers and illustrations with "arrows" <>
<> E29, E30, E31 p. 102-103 Shows two versions of the "A" frame, both are mislabeled as Car#1. It would appear that the E31 photo which shows a straight girder-like "A" frame with the front pivot points at the front axle goes along with E14 Scale Drawing top of p. 100. Because of the bulky and rather crude construction this may be the earliest version of a "rolling chassis."
This same set of drawings appears on [] p.129- 130. An engineering drawing at the bottom of [] p. 125 - "Car #1, Drawing 13 - shows the sub-frame to be 127" long and 45" wide at the front axle attachment points. 4-29-33. This drawing is marked "SUPERCEEDED"
[] p. 118 shows a photo of a car, labeled as "Car #1" which has an "A" frame pivoting amid-ships, not at the front axle. This "driving Chassis" has a dark colored, CT license plate FV 453. This same photo appears on <> p. 102 as E30. Engineering Drawings [] p. 123 show an "A" frame some 66" long by 34" wide dated 4-10- 33. Apparently these two cars were under design and construction almost simultaneously.
[] p. 135 shows a photo of a completed car with FV 453 CT license plate with Ralph DePalma standing beside it. The CAR #2 - 1933 legend also appears in <> as E39 on p. 103.
Photo E40, p. 104<> compares two approaches to the "A" sub-frame. One is very heavy and pivots at the front axle. This seems to correspond the "127" long" version described above. The second frame treatment in E40 is lighter in construction and is, apparently not hinged at the front axle but, rather at the mid- point of the engine bearing sub-frame. This seems to correspond to the "66" long" frame mentioned above.
The greatest design differences appear in the photo <> E42 p. 104 and the Engineering Drawing []153 & 155 which show an asymmetrical placement of the steering post. In this scheme, the post (rudder axis) is tilted 10 degrees to one side of the vertical which results in a simpler, straight line "Rudder Post." This variation is shown on the "shorter length" "A" arm - 52" long by 36" wide.
This configuration requires tilting or canting of the steering sprocket from the horizontal plane of the others.
This "tilted steering post" version and a "straight frame" are shown on p. 160 & 163 on a car labeled Car #5, 1934[]. This car seems to be the last one ever constructed and is shown on [] p. 158. It has two tone paint, air cooling louvers and a tail fin.
Could this be the car at Harrah's Auto Museum in Reno, NV? If so, which type of "A" frame was used?
Steering Wheels and Cable/Chain Variations: The earlier version of the car and the Patent Drawings indicate a simple chain sprocket wheel with attached cables running over strategically placed pulleys to the rear where they were again attached to a chain passing over the horizontally mounted steering sprocket. With a 30:1 ratio between the small diameter driving sprocket and the large rudderpost sprocket, there would be a great deal of effort in driving the car.
Drawing #3 for Car #1 []p. 122 shows such a mechanism. p. 149 [] shows a Worm And Gear version for Car #3, dated 10-6-33. This type of device would not permit "Self Centering" upon release. The nature of such a mechanical advantage is "many turns of the worm" for one turn of the gear AND the gear cannot "unwind" upon release so as to allow the steering to "neutralize" or return to the straight ahead condition. You would have to crank both ways.
A variation Bevel Gear set for Car #3 [] p. 153 (SUPERCEEDED) and a similar design for Car #5 with a 3:1 ratio is shown. This device would both reduce steering effort and return to neutral when released.
The first versions of the rear steering showed an ability of the rear wheel to turn through 360 degrees with at least 180 degrees usable. While this feature would be advantageous in parallel parking regular over the road travel would need to be limited in some fashion for safety. Reference is made to a "warning buzzer or light" which would alert the driver to a possible sideswipe condition.
Page 141 [] shows a rather elaborate mechanism designed for Car #2, 10-8-33 which has a Restricted Steering mode, and, by pulling a restraining pin from a hole in a locating plate, the Free Steering Mode with greater rotation is permitted.
The earlier version of the Dymaxion Car employed the large, soft automobile tires as the primary suspension elements. Also utilized were transverse leaf springs front and rear - a common 1930's automotive application. Rotary hydraulic shock absorbers were used to control "sway" and to load the rear "A" arm travel which supported the engine/transmission more heavily than the front which supported the passengers.
This springing arrangement was shown in the Patent Drawings{} and was common to Car# 1 and #2. Another evolution shows a pair of front mounted parallel leaf springs (Car #2.5???) perhaps to deal with the increasing weight of the vehicle.
The design of Car #5, p163 [] 4-18-34 shows a second set of parallel leaf springs at mid-ships to help hold up the heavy engine/transmission sub-frame. By this time, the sub-frame no longer pivoted at the front axle - the side rails appear to be clamped solidly to the axle housing on each side. Perhaps the "spring wrap-up" allowed sufficient flexibility to eliminate the articulated, double-jointed configuration. This last version retains the rear mounted, transverse leaf spring with turnbuckle adjustable hangers from behind the engine to control "A" frame travel.
In the earliest versions and in the Patent Drawings, the "A" frame was pivoted either behind or above the front axle housing. By attaching this load bearing point on the axle, a good deal of the vehicle weight was "un-sprung" ie. not carried as supported load with the body.
The engine sub-frame was perched atop the front leaf spring and hung from the "A" frame - which in turn was attached to the rear transverse leaf spring.
With the introduction of the 66" long "A" arm configuration and the increased weight anticipated for the vehicle (4450 lbs. loaded) the engine sub-frame received additional springs amid- ships. Page 163. [] shows the location of these springs.
The most Unusual Layout: Page 127 [] shows a very difficult to read Blueprint (white lines on a black background) and a lower drawing of a most unsual drive line design. The motor is mounted in the rear with a shortened driveshaft running to the Ford axle which is mounted beneath the pivot points for the 66" "A" arm. This places it at about the middle of the car with twin chains - one for each wheel on each side running forward to the drivewheels. Because the differential is between the driving sprockets at the rear, there is no need for such at the front of the vehicle. The tires are independently mounted on either end of a live axle where they drive but do not steer the car.
As mentioned earlier, Buckminster Fuller envisioned a Flying Car, powered by gas turbine engines. He planned to use a Continental four cylinder engine, did use a Ford V-8 and in the proposed D-45 Kaiser design indicated several engine adaptations:
Pages 176 - 177 [], shows what appears to be three, five cylinder, air cooled, rotary engines - one at each wheel. At road speed, only the rear wheel was to be powered - the others shut down to conserve fuel. An alternative, two cylinder, 10 HP engine is shown on p. 181 [].
One drawing of the D45 shows placement of three, gas turbine engines - one at each wheel. These cars were never built.
1. "It held up to 10 people, not including the driver." (www.swifty.com/apase/charlotte/@U104car.html) No place can I find any drawing which has more than two seats out front and two additional at the rear bulkhead. There is no drawing in any of the references which shows any additional "jump seats" or bench seats similar to a modern mini-van.
2. First production car to incorporate air-conditioning. Page<> 105 E44, " Headlights are recessed in the body, providing "nostrils" which were intakes for air. Dry ice cooled the incoming air."
3. Contrary to various descriptions of the Dymaxion Car as, "... not much heavier than a VW Beetle." ...(http://www.thirteen.org/bucky/car.html) the Drawing on page 163 of this publication, [], Labeled DISTRIBUTION of WEIGHT (loaded) shows 4850 lbs with 3450 lbs (71%) on the front wheels and 1400 lbs on the rear wheel. Unfortunately, the photo quality of this Engineering Drawing is poor and, therefore, the EMPTY weight is almost unreadable. (Perhaps 3100 lbs OR 3400 lbs total with 2300 lbs front and 1100 lbs rear???)