Transcript No Slide Title

Team 07F
Airgun Ammunition Project
Team Members
Bryan LaMora
Joe Ouellette
Zach Rohlfs
Project Definition
Task:
Provide an economical
material to replace the current
lead pellet.
Reason:
Due to health concerns
lead pellets will eventually
be discontinued.
Specifications
Pellet Size:
-.177 cal.
-.176 +.003/-.0005
-.4 to 10.5 grain
-.195” to .260” (ASTM F 590)
-Any Shape
Specifications
Requirements:
-minimum 24 lb shot force
-Non-Toxic
-100 ft/s to 1200 ft/s velocity range
--30 to 100 deg F operating temp.
-Immune to black oxide oils
-Remain intact after impact
-$.10 to $.80 per 100 pellet cost
-.835” @ 25yd Shot Group
Ideas & Evaluation
- All steel pellet
- Composite pellet
- BB encased in plastic
- Steel cylinder encased in plastic
- Plastic and Iron filings mix
Design Obstacles
-Metal and plastic composite
-Steel core
-Plastic exterior
Design Obstacles
•Sacrificed aerodynamics to increase weight
•Keeping the manufacturing process as simple as possible
Plastics Research
Requirements:
-Dense
-Impact resistant
-Fairly high melting point
-Inexpensive
-Easily molded or thermoformed
Plastic Body Material
- Criteria
- Impact resistant at low
temperature
- High density
- Low cost
- Easily injection molded
- Material
- Polypropylene
- Polystyrene
- PVC
- ABS
- Acrylic
- Polyester
- Nylon
- Polyethylene
- Fluoropolymers
- Polycarbonate
Inner Material
- Criteria
- Coefficient of restitution
- Density
- Cost
- Materials
-
Aluminum
Nickel
Tin
Steel
Brass
Copper
Bounce Back Effect
-
Lead:
Copper:
Brass:
Steel:
55 Feet
77 Feet
105 Feet
314 Feet
Bounce Back Results
Worst Case scenario coefficient of restitution: .22
Coefficient of restitution from tested : .106
Coefficient of restitution of lead: .16
Pellet Flight Characteristics
 Will the velocities be approximately equal?
 Is the Cd, coefficient of drag constant?
 How do we determine the coefficient of drag?
 What does this all mean?
Calculating Drag
Cd 
Fd
1
V 2 A
2
Fd  m  ad
dv
ad  V
dx
dV
ad 
dt
 Cd is the coefficient of
drag
 Fd is the force of drag
  is the density of the
fluid
 A is the cross-sectional
area.
 m is the mass of the
pellet
 ad is the acceleration of
drag
 V is the velocity of the
pellet at a given time, t
Fluent and approximations
 Experimental data is not needed.
 Small geometries need to be scaled by Reynolds
numbers.
 Two dimensional approximations differ from three
dimensional.
Results and Their meaning
 Cd~0.4 for hand calculations on the old pellet.
 Cd~0.47 for the old pellet by Fluent using a two
dimensional model.
 Cd~0.56 for the new pellet by Fluent using a two
dimensional model.
 The velocity of the new pellet will degrade faster.
Calculation Assumptions
A) Pressure is constant through barrel.
B) Temperature decrease due to
pressure change of gas is
neglected.
C) Temperature is constant.
D) Force of gravity is negligible on pellet.
Pellet and Barrel
Flow
.177”
24 psi
19.5”
Barrel:
Brass 330
Rifling: 1 Twist in 14” Right Hand Lead
6 Lands .045” wide
Force due to Pressure
C  .045in(6)
L
C  .277in
L
A C W
L
C
A  .277in(.02in)
C
A  .00553in2
C
F  PA
P
C
F  24 lb (.00553in2)
P
in2
F  .133lb
P
AC = Contact Area
CL = Contact Length
w
= Width of Contact Area
FP = Force due to Pressure
P
= Air Pressure in chamber
Heat Generated by Friction
F  F
f
k P
F  (.4)(.133lb)
f
F  .0531lb
f
W
f
F L
f B
 (.0531lb)(19.5in)( 1 ft )
f
12in
W  .0863ft  lb
f
W
W  
f
ΔΗ  .0863ft  lb
LB = Barrel Length
Wf = Work Due to Friction
FP = Force due to Pressure
DH = Change in Heat
Temperature Change
  C ()
P
Mwt = Material Weight
DH = Change in Heat
  C ()(M wt )
P
CP = Heat Capacity
DT = Change of Temp
  
C (M wt )
P
Pellet Weight
TLead Pellet = 1.77 C
Lead
= .512g
TPlastic Pellet = 1.49 C
Plastic
= .0418g
TBarrel
Barrel weight
Brass 330 = 185.07g
= .0017 C
Prototyping & Testing Schedule
Wk
March1
2
3
April 4
5
6
7
May 8
9
10
Mon
10-14
17-21
24-28
31-04
07-11
14-18
21-25
28-02
05-09
12-16
Tues
Wed
Thur
Fri
First Day Back
Quarter Time Line update
Empire update
<-------------------------Tooling Setup--------------------------->
Crosman Update Meeting
<---------------------------------------------Machining of first 7 pellets------------------------------------------------------->
<--------Testing #1--------->
<---------------------------------------------Machining of 40 new prototypes------------------------------------------------>
<--------Testing #2--------->
<----------------------------------Technical paper edit------------------------------------------>
Tech paper to Advisor for review .
<-----------Technical paper final edit--------------> Technical paper Turn in.
<------------------------------Creation: poster/presentation----------------------------->
Set up test firing
Pellet Firing Demonstration
Deliverables w rap up
Final Presentation
Conclusions
The new Pellet met the following criteria:
Functions in a .177 cal Air Rifle.
Between 4 and 10 grains in weight.
.255 in length
Operates in a velocity range of 100 to 1200 ft/sec.
Nontoxic and resistant to black oxide.
Low Bounce back.
Conclusions
The new Pellet fell short in the following areas:
Utilize rifling in barrel:
Plastic did not conform to the rifling of the barrel.
Under-sizing of pellet “skirt” will help pellet follow rifling.
Accuracy:
The lack of spin of the pellet out of the barrel.
Intact after impact:
Prototype was hand machined, plastic did not “lock” core
into pellet.
Questions?