Photokographer asked, "how much has changed about the PD?"
In some ways not much... the question about tube size is easy. We have always used 1/2" diameter #5 polypropylene rod (made in Germany) sold through US Plastics in Lima, Ohio. Pronounced: Lima Beans style, BTW. We did use a few other tube materials during personal prototyping, 1/2" PP was best IMO.
The vapor tip length was increased in very early production from about 8mm to 10mm but the tubing diameter and supplier has remained the same since Day 1. SS Screens too.
My original, all stainless steel heat exchanger design, with the crossbar and heat sinks and radiating fins has had some minor tweaks. We moved from 5 heat sinks and 60 fins, to 5 heat sinks and 72 fins, adding an additional set of fins at the bottom where the air makes it's turn upward. We also moved to a black oxide stainless steel for our fin material... Both of these changes were to maximize the heat transfer, to the airstream, from a fixed heat source, the intent of a complex heat exchanger air path in the first place.
The heat source, an Ohmite 25J20RE has been at the heart of
every vaporizer we have made. The E designates the RoHS version of the resistor. The only version we have ever purchased. Every vape we have ever made, uses 100% RoHS compliant parts. No need to change.
The body has been through a couple of cosmetic changes. Early units had a small, recessed, purple LED at the bottom front of the unit. Nearly ultra-violet it cast a cool light... but miniature recessed LEDS + heat conducting copper wire, well... LEDs don't like heat. LEDs were discontinued in early production. Pammy started doing a wood burned version of our Purple Sunshine Logo instead. A shop in Port Orford had a nice laser and woodshop and we started having the laser etched version of our logo applied. We later found another woodshop, who was able to do a bit deeper laser etch, with a better laser machine...
Today, in Rockazona, we have no source for laser logos and as bodies with laser logos are used up the newest design is a stealthy No Logo . As folks seem to like No Logo, as well or better, that will remain the design at least for now.
We have used hardwoods from the start. Dimensions have not changed. They are based on the standard American cola can. Though, each unit is unique, as it is turned by hand. I do not use a duplicator lathe. Nor a router to round over the end of a dowel . . .
Still using our all natural Buzz-Butter
finish. Still using the same chemical free apiary 's bees wax. I got 50 pounds of it last time, I don't plan on changing and bee's wax never goes bad... Still using Organic Flax oil. Still using the all natural Rosemary Extract as an ant-oxidant just like quality soap makers do. But we have made a couple changes. Adding an amount of Organic Coconut Oil to the mix seems to give it a better feel. And adding Organic Hemp Oil, well . . .
Hope that helps explain some of our changes over the years. In some ways things have changed very little.