Week 8 Update: Chameleon's Tongue, first Test

Over the course of this week, the tongue section of the design was built and tested. Rectangular pieces of polyethylene material were rolled and sealed using a hot glue gun. The tongue body was then sealed on one end and attached to the air blow gun using a pipe clamp on the other end. A 1 foot 3 inch tongue was first tested to see if the tongue design was feasible:

Design with a 1 foot 3 inch tongue

The tongue was then extended to 3 feet but failed because the air tore through the sealed bag:

Design with 3 foot tongue

Point of failure of the 3 foot tongue design

The tongue was then shortened to 2.5 feet, rubber bands were also added to retract the mechanism. The rubber bands were clamped down by the pipe clamp and attached to the tip of the tongue. The design was not operational as the rubber retracted the tongue before the compressed air managed to fully extend the tongue:

Design with 2.5 foot tongue and rubber band retraction mechanism

It was then concluded that the tongue needed to be shortened considerably for the design to be functional.

Week 7 Update: Nozzle replacement and pressure tank calculations

Over the course of this week, the nozzle of the air blow gun was replaced with a threaded 4 inch brass pipe, the tip of the pipe was cut with a pipe cutter. The following figure shows the current status of the design:

The shooting mechanism with four inch brass pipe

The height of the assembly is 19.6" and the width of the design 8.6". The length from the tip of the barrel to the tip of the air valve is 20.4".

Calculations were also made to estimate the amount of air that can be blown into the bag. Assuming the tank is approximately a cylinder with a base of radius 0.625” and length 10”, its volume is 12.3 in². Since atmospheric pressure is 14.7 psi, the air in the tank is 8.2 times more compressed than the surrounding air. The tank could therefore potentially release a volume of 8.2x12.3-12.3=87.9 in². Since the bag has a maximum diameter of 1”, the maximum length the air blow gun could extend the bag to is 87.9/(πx(0.5x1)²)=111.9 in=9.3 ft. Therefore, in theory, the air blow gun can release a sufficient amount of air to extend the 2.5 foot long bag.

Week 6 update (2 of 2) : Hard Drive Failure and Final Parts List

This past Sunday, the team member responsible for creating the CAD replication woke up to a hard drive failure. After spending the better part of their Sunday trying to recover his hard drive, the team determined that all of the virtual part and assembly files he worked on for 4 hours are completely irrecoverable. The only proof that these files ever existed are the two screen-shots posted in Week 6 Update (1 of 2). Plans have already been put into motion to recreate these files. 

Worse yet, the owner of the failed hard drive has lost all of his work from this term and has to spend another $70 to replace his failed hard drive.

On the subject of money, the team drafted and ordered supplies from the final supply list. Each of the components, their manufacturer, model number, and price can be viewed in the Table below.  Once the parts arrive on Wednesday, May 15, the tongue component of the device will be assembled.

Category	Component	Model No.	Manufacturer	Cost
Trigger Components	6” of ¼” Brass Pipe	-	Generic	$13.02
	Heavy Duty Blow Gun	D3281	Shop Fox	$8.74
	10” of 1-1/4” PVC Pipe & End Caps	-	Generic	$6.07
	Air Intake Valve (Schrader)	BAV ¼	Campbell Mfg Inc	$4.99
Tongue Components	39 Gallon Lawn Bags	E-86720	Hefty	$9.97
	Rubber Band Size #117A	26255	Alliance	$6.82
	Velcro Sticky Back 7/8” squares	90348	Velcro	$5.59
	Double Sided Duct Tape	1362929	Duck	$5.27
Construction	1/2” Thread Seal Tape	T-27730A	California Tools	$8.79
	½” Pipe Clamp	N/A	N/A	$5.00 (Projected)
	Hot Glue Gun	N/A	N/A	$10.00 (Projected)
Other	’70 PSI’ Deluxe Hand Pump	57773	Custom Accessories	$11.00
	TOTAL			$95.25 (Projected)

Week 6 Update (1 of 2): Final CAD Assembly

This week the final draft of the assembly was finished. As opposed to prior rough draft assemblies, each of the components in the final digital assembly were constructed to totally replicate the real-life components we have gathered. The dimensions, method of attatchment, and physical appearance of each of the parts were replicated as accurately as possible. Overall two assemblies have been produced, one with the tongue in the retracted position, the other with the tongue in the extended position.

Figure 1. Final CAD Assembly (Extended Tongue)

 

 

Figure 2. Final CAD Assembly (Extended Tongue: Expoded)

Week 5 Update: Shooting mechanism assembly

Over the course of this week, the shooting mechanism for the design was constructed. The following list details each part and provides links to where they were purchased:

-Air Pump: 70 PSI Deluxe Hand Pump, used to fill the design tank with compressed air. Available here.

-Air Blow Gun: Shop Fox Heavy Duty Blow Gun with removable 4 inch nozzle and 180 psi maximum pressure, used to shoot the tongue mechanism, the retraction mechanism will be latched on to this part. Available here.

-Air Intake (Shrader) Valve: attached to the bottom of the pipe/tank, the compressed air will be filled through this valve. Available here.

-Thread Sealing Tape: ½ Inch PTFE Seal Tape, used on the threads at the bottom of the gun and on the air intake valve to prevent air leakage. Available here.

-1 ¼ inch PVC Pipe: used for the body of the tank and available in any hardware store.

-1 ¼ inch PVC endcaps: connected at the extremities of the pipes. These endcaps will be connected to the threaded air gun on one side and air intake valve on the other. Available at any hardware store.

-PVC Primer and Cement: used to seal the endcaps to the pipe. Available at any hardware store.

Parts used for the shooting mechanism assembly

The tutorial section of this website provides a comprehensive guide to the assembly of these parts.

The holes on the endcaps accommodating the threads of the air gun and the air intake valve were drilled in the machine shop, the PVC pipe was also cut down to a length of 10 inches at the machine shop. The tank was assembled and tightly sealed using PVC Primer and Cement. Three to five layers of thread sealing tape were wrapped around the air intake and air blow gun threads before the whole mechanism was assembled with a wrench.

Assembled shooting mechanism 

The pressure of the tank was then measured with pressure gauge attached to a pump. The tank was shown to withstand a pressure of at least 120 psi, which will be abundantly adequate for the design. So as not to accidentally destroy the shooting mechanism, the tank pressure will not be raised above 140 psi.

Assembly connected to a pump with a pressure gauge

Reading on the pressure gauge