Week 9 Update: Tongue Improvements and Completed Budget

This week the group worked to bring the project into it's concluding stages. In terms of construction, the group unanimously decided not to include the retraction mechanism (rubber band) in the final presentation device. After extensive testing, it was determined that any sort of retraction mechanism would simply inhibit the extension mechanism from working properly. While successful tongue retraction would have been a convenient feature, the device is fully viable using only the extension. The two video's below (one including the retraction rubber band, the other without) demonstrate how the retraction mechanism inhibited the successful firing of the device. 

 

Video 1. Test-firing the device (with retraction mechanism)

 Video 2. Test-firing the device (without retraction mechanism)

Work will continue next week (week 9) to make sure any minor improvements are made to the final design. Accuracy and reliability remain an issue. Upon firing, the device has a ~25% catastrophic failure rate (see Video 1) and a ~75% chance of working, but missing it's target (see Video 3).

Video 3. Test-firing the device. Accuracy is not optimized.

Based on the testing results, a small number of minor changes have been made already:

Issue	Tested Solution	Effect
The tongue bursts when fired.	Increased the layers of plastic on the tongue from 1 to 3/Added another layer of hot Glue	The tongue remained intact more often. The tongue is much thicker and more difficult to scrunch up on the barrel.
	Lengthened the tongue from the test length of 1.5’ to 2.5’ to accommodate	The tongue does not fit on the barrel properly and does not extend when fired. It is too heavy.
The tongue does not slide off the barrel when fired.	Increased the PSI in the tank prior to firing from 50 to 70 PSI	The tongue bursts more often.
	Removed the retraction mechanism	The tongue slides off the tongue more easily, but has no chance of retracting
	Decreased the layers of plastic on the tongue from 3 to 2	The tongue slides off the tongue more easily and is slightly thinner/lighter.
The tongue is inaccurate.	Instead of scrunching the entire tongue onto the barrel before firing, the last 6” of the tongue hang freely off the end	The tongue extends more rapidly and with slightly better accuracy
	Aiming slightly above the target	Increased the accuracy slightly, but is more difficult to predict

Table 1. Minor changes made to the device during week 8. 

Additionally, the final project budget was completed and has been posted below. This updated project budget removed any projected costs listed in the Week 7 Update and recalculated the total cost accordingly. 

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
	1/4” to 5/8” Pipe Clamp	92897	American Valve	$0.49
Other	’70 PSI’ Deluxe Hand Pump	57773	Custom Accessories	$11.00
	TOTAL			$80.74

Figure 2. The Final Project Budget and Components