Here is a link to a very thorough DIY project where you can build them for yourself. The guy really took time w/photos and sources for parts. It's a 36 page .pdf so it takes a while to load. It's on Alan Mahers site. Check it out!
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http://alanmaherdesigns.com/Documents/HRSCF_Project_rev-1.pdf
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http://alanmaherdesigns.com/Documents/HRSCF_Project_rev-1.pdf