Copyright: Copyright Lotus Engineering, 1998.


Program overview
BATS98  - Program Overview

Bats is a collection of individual bolted joint calculations, that are normally applied to critical fasteners. Some of the sections are specific to a particular joint, such as an automotive split cap connecting rod, whilst others are more generic and may be applied to any bolt.

The individual calculation modules are identified below:

1) BATS - Bolt Capability Analysis

Select from the data base of BS3643 thread details the required bolt size and class of fit, identify the material properties to determine the maximum and minimum bolt clamp loads, the associated required lengths of thread engagements for both plastic and elastic tightening.

2) JOINT - Specific Bolt Specification

Select from the data base of BS3643 thread details the required bolt size and class of fit, identify the material properties to determine the maximum and minimum bolt clamp loads, the associated required lengths of thread engagements, for the chosen tightening regime. Select from either yield tightened, torque + angle or torque tightened. The minimum torque capacity of a detailed 'friction' joint is also determined with the associated maximum contact stress.

3) BEES - Half Bearing Shell Interference

Calculates the variation in the clearance and interference characteristics of a thin shell bearing in a split housing, (i.e. connecting rods and main bearings). The inclusion of component tolerances and thermal properties allows the total population to be analysed through the operating temperature range. This identifies the variation in bearing clearance, stresses in bearings, bearing 'crush' loads and bearing contact pressures.

4) JOINT2 - Connecting Rod Bolt

Identifies the suitability of a particular bolt and tightening specification to the applied loads for the detailed connecting rod application. The user defines basic engine geometry and masses together with the proposed operating speed. Real world joint effects are included via a joint lever ratio, bearing shell interference and relative stiffness calculations.

5) JOINT3 - Main Bearing Bolt

Identifies the suitability of a particular bolt and tightening specification to the applied loads for the detailed main bearing application. The user defines basic engine geometry and peak bearing loads. Real world joint effects are included via a joint lever ratio, bearing shell interference and relative stiffness calculations.

6) JOINT4 - Cylinder Head Bolt

Identifies the suitability of a particular bolt and tightening specification to the applied loads for the detailed cylinder head application. The user defines basic engine geometry and peak gas loads. Real world joint effects are included via a gasket stiffness, gasket relaxation and relative stiffness calculations.

A number of the calculations share either common data or the results from one calculation form part of the input to another. The use of 'Import' functions allows these 'common' values to moved between the individual calculation data screens.

Each calculation has its own window that contain three discrete sections. The first is the identification section that contains time, date and description strings. The second is the data entry section, which through either spread sheet type format or individual value entry and selection boxes the required data is entered. The third section displays the calculation results in a scrollable spread sheet, with design targets identified where relevant.


Bats - Bolt Capability Analysis - Overview

Procedure

A metric thread size is selected from the available options within BS3643, this together with its material grade are used to establish the clamp capability of a particular thread size. Alternatively different thread sizes/grades/tightening procedures are reviewed to identify the required thread size for a particular minimum pre-load.

Results

The tensile stress area of the defined fastener. The maximum available clamp loads and associated range of clamp loads from either yield tightening or torque tightening the defined fastener. Estimates of torque a angle for yield tightening are identified as are the likely length of thread engagement that each load range will require.


Bats - bolt capability analysis - data
Bats - Bolt Capability Analysis - Data Requirements

Identification:

Project ID	Engine ID	Bolt ID	Date

Program Objectives:

1) 	To establish the available bolt preload alternatives for a given bolt.

         or   2)	Identify the required bolt size to achieve a target minimum clamp load.

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Bolt Diameter (mm)
b	Thread Pitch (mm)
c	External Thread Class
d	Internal Thread Class
e	Bolt Material Grade   1   Select from grades (ie 10.9)   2   User Defined
f	for 2 Bolt UTS (N/mm2)
g	for 2 Bolt Yield (N/mm2)
h	External Thread UTS range (N/mm2)
i	Shank Type   1           Plain   2     or  Waisted
j	for 2, Waisted Shank Dia (mm)
k	Internal Thread UTS (N/mm2)
l	Free Bolt Length (mm)
m	Thread Coefficient of Friction

Notes:

1) Typical external thread UTS range, (item h), is 200 N/mm2, i.e the difference from one grade to the next.

2) Free bolt length, (item l), is the length of the fastener under tension, i.e. first engaged thread to bolt underhead.


Joint - Specific Bolt Specification - Overview

Procedure

A metric thread size is selected from the available options within BS3643, this together with its material grade are used to establish the clamp capability of a particular thread size at a defined tightening condition.

Results

The tensile stress area of the defined fastener. The maximum available clamp loads and associated range of clamp loads from the specified tightening procedure. Estimates of a service torque and angle are identified for yield tightening as are the likely length of required thread engagement.


Joint - specific bolt specification - data
Joint - Specific Bolt Specification - Data Requirements

Identification:

Project ID	Engine ID	Joint ID	Date

Program Objectives:

1) 	To establish the bolt preload variation.

2)	To set the length of required thread engagement.

Actual engagement  (mm)

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Bolt Diameter (mm)
b	Thread Pitch (mm)
c	External Thread Class
d	Internal Thread Class
e	Bolt Material Grade   1   Select from grades (ie 10.9)   2   User Defined
f	for 2 Bolt UTS (N/mm2)
g	for 2 Bolt Yield (N/mm2)
h	External Thread UTS range (N/mm2)
i	Shank Type   1           Plain   2     or  Waisted
j	for 2, Waisted Shank Dia (mm)
k	Internal Thread UTS (N/mm2)
l	Free Bolt Length (mm)
m	Thread Coefficient of Friction
n	Tightening Technique   1         Yield Tightened   2    or  Maximum Torque    3    or  Specify Torque   4    or  Specify Torque and Angle
o	for 3 and 4, Tightening Torgue (N/m)
p	for 4, Angle (deg)
q	No of Bolts
r	Contact Area OD (mm)
s	Contact Area ID (mm)
t	Joint Friction Coeff

Notes:

1) Items q to t are only relevant for friction drive joints, i.e. flywheel palm.

2) Typical external thread UTS range, (item h), is 200 N/mm2, i.e the difference from one grade to the next.

3) Free bolt length, (item l), is the length of the fastener under tension, i.e. first engaged thread to bolt underhead.


Bees - half shell bearing interference - overview
Bees - Half Bearing Shell Interference - Overview

Procedure

A connecting rod bolt is required to provide sufficient clamp load under all assembly and operating conditions to maintain contact between the connecting rod and the cap.  In addition the alternating load ‘felt’ by the bolt must not lead to fatigue failure of the bolt.  Bolt under head stresses at the maximum clamp load must be less than the compressive yield strength of the connecting rod cap, and the minimum length of thread engagement must be greater than that required to carry the maximum bolt load.

Bolt loads and stresses are based on the joint diagram, derived from the relative stiffness of bolt, shell, and rod.  The bolt ‘felt’ load can then be determined for any given applied load.

Due to the eccentric nature of the joint, applied loads are factored by an assumed lever ratio, this lever ratio being derived from the joint moment arms

The joint diagram can also be used to determine the theoretical separation point, by including the leverage ratio of the eccentrically applied load, and comparing to the minimum clamp load, which is based on the condition of minimum bolt load and the maximum bearing overstand.

Thick shell theory and the bearing and housing dimensions are used to derive the maximum bearing shell overstand, stiffness, and crush load under assembly conditions.

Results

The variation of the bearing clearance throughout the defined tolerance and temperature ranges. The maximum bearing overstand, and hence crush load are identified. Contact pressures between the shell and the housing are compared to design targets for adequate protection against fretting. The stresses in the bearing shells should be compared to the yield strength of the bearing backing material.


Bees - half bearing shell interference - data
Bees - Half Bearing Shell Interference - Data Requirements

Identification:

Project ID	Engine ID	Bearing ID	Date

Program Objectives:

1) 	To predict the bearing shell stiffness.

2)	To calculate the maximum bearing shell crush load.

3) 	To calculate the operating clearance range.

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Maximum Housing Diameter (mm)
b	Housing Tolerance (mm)
c	Maximum Journal Diameter (mm)
d	Journal Tolerance (mm)
e	Max Wall Thickness (mm)
f	Wall Thickness Tolerance (mm)
g	Maximum Steel Thickness (mm)
h	Bearing Material Type   2   Bronze   3   Aluminium
I	Bearing Length (mm)
j	Checking Load (N)
k	Checking Diameter (mm)
l	Minimum Checking Overstand (mm)
m	Maximum Checking Overstand (mm)
n	Outer Diameter Multiplier
o	Young’s Modulus - Bearing (N/mm2)
p	Young’s Modulus - Housing (N/mm2)
q	Poisson’s Ratio - Bearing
r	Poisson’s Ratio - Housing
s	Housing Linear Coeff of Expansion (oC)
t	Bearing Linear Coeff of Expansion (oC)
u	Journal Linear Coeff of Expansion (oC)
v	Minimum Operating Temperature (C)
x	Maximum Operating Temperature (C)

Notes:

1) Typical ranges for tolerances are as follows,

Housing Tolerance (item b)	0.012 - 0.019 mm

Journal Tolerance (item d)	0.012 - 0.016 mm

Wall Thickness Tolerance (item f)	0.006 - 0.008 mm

2) The Outer Multiplier, (item n), is the ratio, relative to the maximum housing diameter, that is used to calculate the effective outer diameter of the housing.

3) The wall thickness, (item e), is the overall bearing shell thickness value, whilst the maximum steel thickness, (item g), is the thickness of the backing shell only.

4) Typical values for the linear coefficient of thermal expansion, (items s,t and u) are,

Steel 	12.0 x10-6/oC

Cast Iron	11.0 x10-6/oC

Aluminium	22.0 x10-6/oC


Joint 2 - Connecting Rod Bolt - Overview

Procedure

A connecting rod bolt is required to provide sufficient clamp load under all assembly and operating conditions to maintain contact between the connecting rod and the cap.  In addition the alternating load ‘felt’ by the bolt must not lead to fatigue failure of the bolt.  Bolt under head stresses at the maximum clamp load must be less than the compressive yield strength of the connecting rod cap, and the minimum length of thread engagement must be greater than that required to carry the maximum bolt load.

Bolt loads and stresses are based on the joint diagram, derived from the relative stiffness of bolt, shell, and rod.  The bolt ‘felt’ load can then be determined for any given applied load.

Due to the eccentric nature of the joint, applied loads are factored by an assumed lever ratio, this lever ratio being derived from the joint moment arms

The joint diagram can also be used to determine the theoretical separation point, by including the leverage ratio of the eccentrically applied load, and comparing to the minimum clamp load, which is based on the condition of minimum bolt load and the maximum bearing overstand.

Thick shell theory and the bearing and housing dimensions are used to derive the maximum bearing shell overstand, stiffness, and crush load under assembly conditions.

Results

The suitability of the connecting rod bolt joint in terms of assembly, thread engagement, under head stress and clamp load for the proposed load cases, or the required fastener specification.


Joint 2 - connecting rod bolt - data
Joint 2 - Connecting Rod Bolt - Data Requirements

Identification:

Project ID	Engine ID	Date

Program Objectives:

1) 	To confirm clamping reserve factor acceptable. (>1.2)

2)	To establish bolt fatigue reserve factor. (>1.2)

3)	To establish underhead contact reserve factor. (>1.0)

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Piston Assembly Mass (kg)
b	Small End Mass (kg)
c	Big End Mass (kg)
d	Big End Cap Mass (kg)
e	Engine Speed (rpm)
f	Rod Centre Length (mm)
g	Crankshaft Stroke (mm)
h	Shell Stiffness (N/mm2)
I	Bolt Nominal Diameter (mm)
j	Bolt Tensile Stress Area (mm2)
k	Bolt Thread Core Diameter (mm)
l	Bolt Thread Pitch (mm)
m	Bolt Head Thickness (mm)
n	Bolt Young’s Modulus (N/mm2)
o	Free Thread Length (mm)
p	No of Bolt Sections
       	   For Each Bolt Section

	Diameter (mm)	Length (mm)
1
2
3
4
5
	Variable	Value
q	Foot Diameter (mm)
r	Head Face Diameter (mm)
s	Foot Young’s Modulus (N/mm2)
t	Foot Comp Yield Strength (N/mm2)
u	Minimum Bolt Preload (N)
v	Maximum Bolt Preload (N)
w	Maximum Shell Crush Load (N)
x	Joint Lever Ratio
y	Bolt Endurance Limit (N/mm2)

Notes:

1) Items j,k, u and v can be obtained from program ‘Joint’ output.

2) Typical bolt endurance limit, (item y), is 75 N/mm2, this assumes a rolled thread and high strength grade base material.

3) Free thread length, (item o), is the length of the threaded portion under tension, i.e. first engaged thread to start of plain shank portion.

4) Foot diameter, (item q), is the equivalent diameter of the assumed effective column of material within the joint.

5) Items .h and w can be obtained from program ‘Bees’ output.

6) Typical values for joint lever ratio vary between 1.4 and 1.6.


Joint 3 - Main Bearing Bolt - Overview

Procedure

The correct clamping of the main bearing is essential to provide consistent bearing support under the applied loads.  These loads are derived from the bearing analysis program.

Normally due to the eccentric nature of the joint, applied loads are factored by an assumed lever ratio, this lever ratio being derived from the joint moment arms.

 The working load in the bolt is determined by considering the relative stiffness of the bearing cap, bolt, and bearing shell.

Thick shell theory and the bearing and housing dimensions are used to derive the maximum bearing shell overstand, stiffness and crush load under assembly conditions.

Given the strengths of the mating components and bolt the required length of thread engagement is calculated, and under head contact stresses compared to the component compressive strength.

Results

The suitability of the main bearing bolt joint in terms of assembly, thread engagement, under head stress and clamp load for the proposed load cases, or the required fastener specification.


Joint 3 - main bearing bolt - data
Joint 3 - Main Bearing Bolt - Data Requirements

Identification:

Project ID	Engine ID	Date

Program Objectives:

1) 	To confirm vertical clamping reserve factor acceptable. (>1.2)

2) 	To confirm horizontal clamping reserve factor acceptable. (>1.2)

3)	To establish bolt fatigue reserve factor. (>1.2)

4)	To establish underhead contact reserve factor. (>1.0)

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Horizontal Bearing Load (N)
b	Vertical Bearing Load (N)
c	Coefficient of Friction
d	Shell Stiffness (N/mm2)
e	Bolt Nominal Diameter (mm)
f	Bolt Tensile Stress Area (mm2)
g	Bolt Thread Core Diameter (mm)
h	Bolt Thread Pitch (mm)
i	Bolt Head Thickness (mm)
j	Bolt Young’s Modulus (N/mm2)
k	Free Thread Length (mm)
l	Washer Length (mm)
m	Washer Diameter (mm)
n	Washer Young’s Modulus (N/mm2)
o	No of Bolt Sections
       	   For Each Bolt Section

	Diameter (mm)	Length (mm)
1
2
3
4
5
	Variable	Value
p	Foot Diameter (mm)
q	Head Face Diameter (mm)
r	Foot Young’s Modulus (N/mm2)
s	Foot Comp Yield Strength (N/mm2)
t	Minimum Bolt Preload (N)
u	Maximum Bolt Preload (N)
v	Maximum Shell Crush Load (N)
w	Joint Lever Ratio
x	Bolt Endurance Limit (N/mm2)

Notes:

1) Items f,g, t and u can be obtained from program ‘Joint’ output.

2) Typical bolt endurance limit, (item x), is 75 N/mm2, this assumes a rolled thread and high strength grade base material.

3) Free thread length, (item k), is the length of the threaded portion under tension, i.e. first engaged thread to start of plain shank portion.

4) Foot diameter, (item p), is the equivalent diameter of the assumed effective column of material within the joint.

5) Items .d and v can be obtained from program ‘Bees’ output.

6) Typical values for joint lever ratio vary between 1.0 for a ladder frame or four bolt fix, to 1.7 for a conventional two bolt separate cap.

7) With a four bolt fix bearing cap the vertical bearing load, (item a), the shell stiffness (item d), and the maximum shell crush load, (item v) should all be halved for the correct calculation of reserve factors.


Joint 4 - Cylinder Head Bolt - Overview

Procedure

Cylinder head clamp loads are required to maintain adequate gasket security under all starting and running conditions.

Clamping loads are considered for a single bore acting in isolation with shared bolts containing the cylinder of interest.  Clamp loads must cover the scatter in bolt material properties, friction, gasket relaxation, and applied gas loads.  Working loads in the bolts are controlled by the relative stiffness of joint, bolt and gasket.

Results

The suitability of the cylinder head bolt joint in terms of assembly, thread engagement, under head stress and clamp load for the proposed load cases, or the required fastener specification.


Joint 4 - cylinder head bolt - data
Joint 4 - Cylinder Head Bolt - Data Requirements

Identification:

Project ID	Engine ID	Date

Program Objectives:

1) 	To confirm clamping reserve factor acceptable. (>3.0)

2)	To establish bolt fatigue reserve factor. (>1.2)

3)	To establish underhead contact reserve factor. (>1.0)

Drawing Numbers:

Component	Number

Data Requirements:

	Variable	Value
a	Cylinder Bore (mm)
b	Peak Cylinder Pressure (N/mm2)
c	No of Bolts in Group
d	Gasket Stiffness (N/mm2)
e	Gasket Relaxation (mm)
f	Bolt Nominal Diameter (mm)
g	Bolt Tensile Stress Area (mm2)
h	Bolt Thread Core Diameter (mm)
i	Bolt Thread Pitch (mm)
j	Bolt Head Thickness (mm)
k	Bolt Young’s Modulus (N/mm2)
l	Free Thread Length (mm)
m	Washer Length (mm)
n	Washer Diameter (mm)
o	Washer Young’s Modulus (N/mm2)
p	No of Bolt Sections
       	   For Each Bolt Section

	Diameter (mm)	Length (mm)
1
2
3
4
5
	Variable	Value
q	Foot Diameter (mm)
r	Head Face Diameter (mm)
s	Foot Young’s Modulus (N/mm2)
t	Foot Comp Yield Strength (N/mm2)
u	Minimum Bolt Preload (N)
v	Maximum Bolt Preload (N)
w	Bolt Endurance Limit (N/mm2)

Notes:

1) Items g,h, u and v can be obtained from program ‘Joint’ output.

2) Typical bolt endurance limit, (item w), is 75 N/mm2, this assumes a rolled thread and high strength grade base material.

3) Free thread length, (item l), is the length of the threaded portion under tension, i.e. first engaged thread to start of plain shank portion.

4) Foot diameter, (item q), is the equivalent diameter of the assumed effective column of material within the joint.

5) Typical values for gasket stiffness, (item d), vary between 200000 N/mm2 and 600000 N/mm2 depending on construction. (i.e. three layer metal gasket would be towards the top end of this range, whilst a ‘conventional’ fibre gasket would be towards the low end).

6) Typical values for gasket relaxation, (item e), vary between 0.09 mm and 0.15 mm again depending on construction. (i.e. three layer metal gasket would be towards the low end of this range, whilst a ‘conventional’ fibre gasket would be towards the top end).