Author: Mike Baer
Lens Cover Selection
It was not necessary to perform any prototyping for the lens covers before purchasing. Instead, a PUGH
diagram was used to evaluate which material would be best for our application. Three options were
considered. Of these, the acrylic sheet becomes the clear winner. This option has the highest light
transmissivity of all three options, 92% for a clear sheet. The only disadvantage of acrylic is that it is
more brittle than polycarbonate; however, it is more scratch resistant, which is ideal for light
transmission.
Lens Cover
Criteria
Light Transmission
Cost/ Area
Complexity (+ is less complex)
Colored Options
Weight
Impact Resistance
Sum +'s
Sum 0's
Sum -'s
Net Score
Rank
Continue?
Option 1
Acrylic Rod
(reference)
0
0
0
0
0
0
0
6
0
0
3
No
Option 3
Option 2
Polycarbonate
Acrylic Sheet
Sheet
+
+
+
+
+
+
0
0
0
0
+
4
3
2
2
0
1
4
2
0
2
Yes
No
TABLE 1: LENS COVER PUGH DIAGRAM
Table 2 shows the calculations performed to determine how much material should be purchased for the
lens cover. A margin of 20% was allowed in order to have room to cut out each section. Although only
11” x 11” is needed, two 12” x 12” sheets will be ordered to allow for mistakes when cutting because
the lens covers will be completely fabricated by hand.
Light Cover
Large Turn Lens
Small Turn Lens
Diamond Lens
L (in)
4.93
2.87
10.07
H (in)
4.31
2.77
4.5
Quantity
Total Area (in^2) Margin (in^2)
2
42.5
51.0
2
15.9
19.1
1
45.3
54.4
Total Area (in^2)
124.5
Total Dimensions (in)
11.2
11.2
TABLE 2: TOTAL AREA REQUIRED FOR LENS COVER
Author: Mike Baer
NOTES
Material






Two different materials: Polycarbonate vs. Acrylic
o Both flexible in thermoforming
o Acrylic:
 Shiner, weaker
 Use: fish tank, hockey rink glass
o Polycarbonate:
 More impact resistant, easier to scratch
 Use: Race car windows, Transparent visors for hockey players
o http://www.coloradoplastics.com/blog-0/bid/42625/Polycarbonate-Lexan-vs-AcrylicPlexiglas
Both used in vehicle application
Suppliers:
o http://lambdares.com/software_products/tracepro/
o http://forums.nasioc.com/forums/showthread.php?t=1194653
o http://www.ledtronics.com/Products/ProductsDetails.aspx?WP=106
o http://www.acrylite-shop.com/US/us/category.htm?$category=l7rnu1b0sroz
o http://www.usplastic.com/catalog/default.aspx?catid=442
o http://www.superbrightleds.com/moreinfo/bar-strip-accessories/luxbar-diffused-lenscover/1099/
How to Cut Sheets
o http://www.rcgroups.com/forums/showthread.php?t=1199027
Acrycast
o http://www.calsakplastics.com/cutting.shtm
o http://www.calsakplastics.com/PDF/SpecSheets/ACRYCAST%20HOMEPAGE%20INFO.pd
f
Acrylic light transmission specs
o http://www.atoglas.com/literature/pdf/81.pdf
o http://www.byk.com/fileadmin/BYK/downloads/supportdownloads/instruments/theory/appearance/en/Intro_Transparency.pdf
Lens Color vs. LED Color
Possible Options
1. White LED/ Colored Lens
2. Colored LED/ Colored Lens
3. Colored LED/ Clear Lens
Author: Mike Baer


http://boards.straightdope.com/sdmb/showthread.php?t=561417
VLEDs, LED light distributor says “For the most vivid color and best results the LED color should be the
same as the lens color. If a white LED is used behind a red lens some of the useable light is filtered out. If a
white LED is used behind an amber lens the color will be bright yellow.”

o http://www.vleds.com/faq#1
The Infiniti G35, which comes stock with LED tail lights uses RED leds with a RED lense cover
o Disassembled Tail light pictures:
 http://g35driver.com/forums/media-share-g35-coupe-v35/277236-taillightdual-ring-led-mod-prelim-work-3.html
o Picture:
 http://www.fototime.com/6468C8FB013E0B9/orig.jpg
o Video:
 http://www.youtube.com/watch?v=Ce3K-qWpjYM