Transfer Assemblies Writing Assignment 1

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Capella University *

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101

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Mechanical Engineering

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Feb 20, 2024

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rtf

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12

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TM 9-8000 Chapter 27 Transfer Assemblies WO1 McCummings, Derrick Warrant Officer Basic Course, TLC Writing Assignment 1 27 April 2022 1
This paper outline is intended as an introduction to transfer assemblies in general. There are several types of transfer assemblies, and their purpose, and how each operates in terms of allocation of engine torque during conventional and atypical usage within vehicles will be discussed. Transfer assemblies are found in every 4-wheel drive, all-wheel drive, and other multiple powered axle vehicles and is essential on vehicles that use both front and rear axles to drive. The Dana Spicer Corporation manufactured automotive powertrain and chassis components through the most of the twentieth century, and according to Steve Turchet, “Dana Spicer Model 18, produced in the 1940’s, can be found in most U.S. military jeeps, including the WWII Ford GPW and Willys MB, as well as the M38, M38A1, and M606. The Dana Spicer 18 was also fitted to Willy/Kaiser civilian jeeps, such as the CJ2, CJ3, CJ3B and CJ5, as well as used in four-wheel-drive Willys pickups, station wagons, and the FC-150 and FC-170 Forward Control vehicles (Turchet, 2019).” The 1940 designs were massively overbuilt, but durable, and torque was delivered to the front either through a set of gears or via a chain. Most modern transfer cases are chain-driven, lighter, and quieter than 2 Figure 1 THE DANA SPICER MODEL 18 “Transfer Case Basics”
earlier gear-driven cases. Because some military vehicles generally allow the driver to select all wheel, 4-wheel, and high or low gear ranges, management of maintenance in operation vehicles is essential for soldiers as there are some costly issues that are possible with transfer assemblies, and if not fixed on time, they can damage the vehicle terribly. Soldiers should be familiarized and/or knowledgeable of vehicle operation modes, the maintenance interval for the transfer case, and owner's manual for the vehicle. This paper will cover segments of transfer assemblies like; the purpose of transfer cases, high and low gear range, differential transfer assemblies, and positive traction transfer cases. Transfer Assemblies : The transfer case has an outer case that can be made of either cast iron or aluminum that is filled with a lubricant that reduces friction on the moving parts. Transfer cases are used in all wheel, 4-wheel, and high or low gear ranges vehicles to split engine torque between the front and rear driving axles. In the article, “Transfer case basics,” author Steve Turchet describes a conventional transfer case as one that “Transmits engine power to the rear axle only, while giving the driver a choice of gear ratios, usually three or four in forward and one in reverse. However, for an all-wheel drive vehicle such as a jeep or an M37, 3
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a transfer case is needed to also transmit engine power to the front axle. On many small vehicles (such as jeeps), the transfer case is bolted to the rear of the transmission. On most larger vehicles, the transfer case is a separate unit mounted behind the transmission and coupled to it by a short drive shaft (2019).” Figure 2 Conventional Transfer Case The transfer case in an all-wheel-drive system contains a device that allows for a speed difference between the front and rear wheels. In addition to the switching driving axles the transfer cases also allow the vehicle body to have appropriate ground clearance and remain at a practical height. High and Low-Gear Ranges are equally, if not more important to the difference between and when either should be employed. High-Gear drives all 4 wheels and should be engaged when the driving surface becomes slippery and the risk of losing traction increases; whereas, Low-Gear operates low-range gear ratios in the transfer box for optimum traction at lower speeds and/or when navigating off-road-like 4
conditions. In a situation where a vehicle utilizes a transfer case, the engine torque is always to the rear axles; however, to achieve torque disbursement to the front axles shifting of a floor-mounted lever or a chain is required. The Hummer: The Hummer vehicle is undoubtably the most used and known military vehicle of choice. The hummer components that can be employed to achieve or acquire greater off-road performance. In this transfer system, the hummer does not automatically lock the front and rear axles together; instead, it contains a set of open-differential gears that can be locked by the operator. In open mode (not locked), the front and rear axles can move at different speeds, so the vehicle 5 Figure 5 Hummer operates on 4-wheel drive "How Four- Wheel Drive Works" Figure 4 Operator instructions on engaging High and Low-Gears "Tranfer Case Basics" Figure 3 TM 9-8000 page 545: Typical Conventional Transfer Assembly Using Chain Drive for Front Axle
can drive on dry roads with no problem. When the differential is locked, the front and rear axles each have access to the engine's torque. Differential- Type Transfer Assemblies : The differential allows wheels mounted on the same axle to rotate independently of each other. The locked or locking differential is a modification found in some vehicles, but mainly in vehicles that go off road. It is essentially an open differential with 6 Figure 6 XXXR All-Wheel Drive Class
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the ability to be locked in place to create a fixed axle instead of an independent one. Unlike older military vehicles which had to be locked/unlocked manually with a clutch, technology in newer service vehicles allow for this to take place automatically via electronic system. According to Militarytrader.com, “Early M35 trucks had an automatic- engagement transfer case, and we’ll get to those later. But on most WWII and smaller M-series vehicles such as jeeps and MUTTs, the driver had a choice of manually selecting either rear wheel drive or all-wheel-drive (Turchet, 2019).” Positive Traction Transfer Case: The positive traction transfer case is very comparable to the conventional transfer case with the main difference being that a sprag unit has taken the place of for the manual sliding clutch. The positive traction transfer case is designed to drive the front axle slightly slower than the rear axle and results in both front and rear wheels of the vehicle are turning at the same speed. In a scenario where traction is being lost or begins to slip, the rear axles will then turn faster. 7
Sprag units will drive in one direction and when turning is reversed, or if the output rotated faster than the input, they will slip or overrun. In reverse, the single sprag unit and double sprag unit are different because the double sprag unit is equipped with a second sprag that only operates while in reverse. The reverse sprag unit is deployed only when the rear wheels lose traction and increase in speed faster than the front ones. 8 Figure 7TM 9-8000: Transfer Assembly Sprag Unit
9 Figure 8 TM 9-8000: Positive Traction Transfer Case Operation
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Similar to the double sprag unit, the air-operated shift control operates the same way with the difference being the air-operated shift control has an air valve which automatically shifts the unit forward or reverse. 10
References Nice, K. (2001, April 18). How Four-Wheel Drive Works . HowStuffWorks.com. Retrieved April 24, 2022, from https://auto.howstuffworks.com/four-wheel-drive.htm. Turchet, S. (2019, November 13). Transfer Case Basics . Militarytrader.com. Retrieved April 24, 2022, from militarytrader.com/mv-101/transfer-case-basics. Xxxr. (2007, January 3). All wheel drive class 101. IH8MUD Forum. Retrieved April 28, 2022, from https://forum.ih8mud.com/threads/all-wheel-drive-class-101.127586/ 11
Suggested Corrections: Section I: Section 27.2 : High-and Low-Gear Range. The hypen after high is not needed. Section III: Section III subtitle : Defferential-Type Transfer Assemblies. Differential is misspelled. Section 27.5: The differential action between…, without the component wear (should be were). Section 27.6 b: The possessive for of Operate’s is incorrect usage and should be operate as a unit. 12
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