Adjust valve bridges (crossheads)

Lesson Plan for

DIT 110-111Introduction to Diesel Engines

Course HS Title: / INTRO TO DIESEL ENGINE / Program:
KCTCS Courses included in HS Title: (Lesson is prepared for course highlighted.)
KCTCS Course No. / KCTCS Course Title
DIT 110 / Introduction To Diesel Engines
Introduction/Context / This lesson will instruct students on how to adjust valve bridges (crossheads). Knowledge of this technique, and the skills required to correct problems associated with this task are necessary for a student to learn if they wish to compete for high paying, high skilled jobs in a Diesel/Medium-Heavy Truck repair facility. Students need to be able to perform this task with 100% accuracy. Incorrectly performing these tasks can lead to engine concerns, safety problems, or create customer satisfaction issues.
Prepared By / School / Date:
Grade Level / No. Students / No.IEP's: / Lesson Length:
Task
Adjust valve bridges (crossheads); adjust valve clearances and injector settings.
Objective
Given the proper tools and instructions, students will be able to adjust valve bridges (crossheads), and pass a written exam on the task with 100% by the end of the course.

Connections:

Skills Standards:
OH 001
OH 002
OH 003
OD 002
OD 003
OD 005
New Common Core Standards:
RST 11-12 3
A-CED-4
N-Q.1
Common Core Technical Standards:
TD-OPS 2
TD-SYS 2
New Generation Science Standards:
HS-PS2-1

INSTRUCTIONAL MATERIALS/TECHNOLOGY
Textbooks and Workbooks

Author / Title/ISBN No. / Edition / Publisher / Pages
Don Knowles / Medium/Heavy Truck Technician Certification Test Prep / Second / Delmar / 110-111
Kershaw/Bennett / Medium/Heavy Duty Truck Diesel Engines / 2001 / Delmar / 139-140


Equipment

Quantity / Item / Source
As Needed / Feeler Gauges / Various
As Needed / Torque Wrench (ft.lbs.) / Various


Content/Presentation/Demonstration Outline

Instruct students that four-valve heads used on four-stroke cycle engines have two intake and two exhaust valves per cylinder. Valve bridges/crossheads are used on some types of diesel engines that use “four valve heads.” Valve bridges push down on two valves at a time.
Explain that two-stroke cycle engines, such as Detroit Diesel, use four exhaust valves in each cylinder. Inform students that the crosshead is a bracket or bridge-like device that allows a single rocker arm to open two valves at the same time. Tell students that they will check the crossheads/bridges for wear by doing the following:
* Instruct students to visually check crosshead for cracks with magnetic crack detector if available, and check crosshead inside diameter for out of roundness and excessive diameter. * Tell students to visually check for wear at the point of contact between the rocker lever and the crosshead, check the adjusting screw threads for broken or worn threads, check the crosshead guide pin for diameter with a micrometer, and check the crosshead guide pin to ensure that it is at right angles to the head-milled surface.
Instruct students on how to Adjust Valve Bridges: Tell students that the following procedure is typically performed on two-stroke Detroit Diesel engines. It is generally required when a cylinder head is removed, overhauled, or replaced. Instruct students to remove the bridge assembly from the cylinder head and mount it in a soft-jawed vice. Let them know that if they attempt to adjust the valve bridges with the bridge assembly on the engine, the bridge guide/valve stem can bend.
Tell them to hold with lock nut finger tight, remove bridge and install once again in a soft jaw vice; hold adjusting screw stationary and torque lock nut to specification, then reinstall the bridge saddle on the bridge guide.
Instruct students that to check the adjustment, they should cut two pieces of 0.0015 in. shimstock (or thickness gauges) so they fit under the bridge saddle. Tell them to load the bridge onto the guide with finger pressure and check for even drag as the two pieces of shimstock are simultaneously withdrawn from either side of the bridge. Let them know to be sure that all the valve bridges are all properly positioned when the rocker assembly is reinstalled.


Applications/Practice

1 / Refer to Content


Evaluation and feedback Prior to Testing or Lab Work

1 / Objective 1/ Formative assessment / Instructor will observe students as they practice the procedure to assure correct procedure and safety practices are being followed. A checklist should be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.


STUDENT ASSESSMENT:(Assess student progress with performance criteria.)

1 / Objective 1/ Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required.
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)