Armored Medical Research Laboratory Fort Knox, Kentucky indexed PROJECT NO. 6 - VISION IN TANKS Fourth Partial Report On Sub-Project No. 6-2, Study of Characteristics and Limitations of Present Visual Devices in Tanks. DRIVER |S VISION IN LANDING VEHICLE TRACTOR Project No. 6-2 9 March 1944 ARMY GROUND FORCES MEDICAL RESEARCH LABORATORY Fort Knox, Kentucky Project No. 6-2 413o74-3 GNOML 9 March 1944 Driver's Vision in Landing Vehicle Tractor 1. PROJECT: No, 6 - Vision in Tanks: Fourth Partial Report on Sub- Project Noo 6-2 - Study of Characteristics and Limitations of Present Visual Devices in Tankso a. Authority: Letter Commanding General, Headquarters Armored Force, Fort Knox, Kentucky, 400,112/6 GNOHD, dated September 24, 1942, b. Purpose? To determine characteristics and limitations in subject vehicles and indicate steps for improvement. - . 1 2O DISCUSSION: a. Most crucial need is for improved driver's vision. It is now necessary for him to make three distinct changes as to means of vision during the most crucial moments in landing the craft as follows: (1) At the outset, he drives with hatch open, seat up and head out, (2) He then lowers seat and opens forward hatch, closes over- head hatch, tilting periscope out of the way so that he can get the maximum of the remaining unobstructed visiono (3) He closes forward hatch and adjusts the periscope so that he retains that small field of view during the remainder and most crucial steps of the operation. It is exactly (hiring this time that the craft is in the greatest danger of broaching or being turned end over end as a result of momentary loss of power or steering. It is believed that a large proportion of the losses, which in battle have amounted to as much as 50% of the landing craft, occur as a result of the distraction caused by the effort to retain adequate vision and from lack of vision, 3, CONCLUSIONS: a0 A wide field of vision should be provided batten-down and with hatch open. b. The necessity of lowering and raising the seat should be eliminated. Co Devices subject to internal condensation and easy obstruction by water must be avoided. 1 H F I-B-B N T-L-A L RECOMMENDATIONS: a. Vision blocks be employed for driver-vision instead of periscope. bo Three units be installed providing more than 180° of overlapping visions Co That the hatch be extended down below the driver's line of vision including the vision blocks so that when opened the driver will be furnished more than ISO0 of unobstructed vision without raising the seat. do Means be provided for partially opening the hatch sufficient for good vision while retaining a large portion of protection both from water and fire0 See Appendix for detailed discussion and drawing. Submitted by: Major Fo S. Brackett, Sn C 7 • • APPROVED WILLARD MACHLE Colonel, Medical Corps Commanding 1 Incl. Appendix w/drawing 2 C A„.tf im I AL APPENDIX lo The standard vision blocks now employed in the tank cupola are well suited to the requirements of this task for the following reasons: a. They provide good horizontal and upward vision, together with all the downward vision possible. The peculiarity of the LVT is that because of its large flat forward deck and low position in the water relatively small down- ward vision is available. As now employed in the tank, good vision from the b block only extends downward 5° - 10°. By lifting the vision block 7° 5°, i®e. front surface 37® 5° from the horizontal as against 30° in the tank, good down- ward vision is increased to 12.5° or 17®5°, quite adequate for the purpose in hand, While there is a corresponding loss in ballistic protection, that which remains is comparable to the general armor protection provided in the LVT. bo Because of the lack of internal air space, no difficulties as to condensation will be encountered. By means of a single windshield wiper motor, three wipers can be simultaneously actuated, thus keeping the outer surfaces free from water obstruction. ? 2. The arrangement of the surrounding vision blocks shown in the plan view provides the full 180° needed, together with the 30° or 40° aft of the beam on the left or port side. With this range of vision, the driver will have far less difficulty in maintaining his course at right angles to the wave frontso 3® While the hatch containing the vision blocks as indicated will be heavier than the present hatch, it will not be greater than the common practice in tanks0 Hence the spring loading compensation can be readily attained. 4, When the hatch is opened a few inches, unobstructed vision is obtained over an even greater angle than that provided by the vision blocks0 Since the line of sight for the vision blocks is provided for a somewhat slumped position, the driver need only straighten up to attain good downward vision with the hatch partly open. A mechanical device is provided for secur- ing the hatch in this partly open position. 5® The shape of the armor below the vision units is such as to provide an effective combing by which the water sweeping up the deck will be turned back rather than immediately entering the hatch opening as is now the case with the front hatch. 60 It is the intent in the present plan to secure approximately 1£ inches ballistic protection uniformly through-out the hatch and surrounding casting. This should be adequate for 50 calibre AP fire at greater distances. 7o The assistant driver is provided with two vision blocks with which he can supplement the driver's vision, especially on the right beam and some- what aft of the beam. 1 CONFIDENTIAL 80 Because of the requirement that the driver's hatch provide more than 180° unobstructed vision when partly open, it is necessary that the machining of the driver's hatch seat be accomplished in two planes. This has been avoided in the assistant driver's hatch by keeping the entire seat in one plane with some consequent sacrifice of unobstructed vision when the assistant driver's hatch is partially openo 2 Sw V/er/ SCM'/W C ■ \/^/o^, L.V. 7 To p '//£ w