I found an extensive read from “sundowner” on another forum that might shed some light on the truth of a DDB. The thread refers to the infomercial put out on DDB by synergy. It’s long but a good read if you’re interested!
“I've seen the video; actually, the video was the first thing I saw...and although it tells us a number or two and bit about what's going on inside (the graphics in the video are how I knew that the outer layer of material had a narrowed, tapered-in design before seeing the picture you posted) it really doesn't do a lot to explain the rationale behind the design and workings of the joint...nor would I expect it to do so. Most people don't care about the how and why of things; they want to know if any given product will make their rig "better" and they want to know how much it will cost...so most product videos are designed with those goals in mind. I actually have to give this video a lot of credit, though, because even though it didn't answer my personal questions it also 1) made no comparisons to other products and 2) gave no assessments as to performance...both of which would be exceptionally hard to prove or back up with valid data. The video is a simplistic overview that basically says "We build good stuff, and here's a new dingus that we've built; it misaligns pretty well and rotates freely, so check it out"...and while I appreciate them not making a product-comparison video I'd also like to know why they've designed the joint as they have. In no particular order of importance, here's what I've gleaned from watching the video a couple of times:
- As always, the joint housing determines the misalignment capacity; here, the joint sleeve doesn't look to have been trimmed down very much (or at all) in width, so the full size/strength of the housing can be utilized. Because this joint has a sleeve around its bushing material and because that sleeve fits into a joint housing, however, the overall diameter of the bushing material has to be somewhat reduced to take the thickness of the outer sleeve into account.
- They're splitting the two necessary directions of movement in the joint - rotation and misalignment - between two different materials, each of which is designed to handle only one of those forces. This isn't a necessarily a bad idea, but since the available real-estate inside a joint is finite it does mean that there's physically less of each material present...so the question becomes one of how much work each material is supposed to do, and whether or not that amount of work can be handled by each individual material over time. I think this question will be basically impossible to answer without knowing some numbers on the composition of the material, and there's no way we're going to get those.
- The inner layer is a bearing surface for the central sleeve, and the outer layer is said to provide "cushion and flex" which means that in addition to handling the misalignment this layer is supposed to be a vibration damper. Since the inner layer doesn't provide much in the way of flexibility, all of the joint's misalignment and/or damping (which isn't really very important at all) comes from the outer layer. The "relief cuts" in the outer layer - those being the tapered sections that form the narrowed center of the material - are there to facilitate or allow compression and/or extension of the material...and this tells us that although the material might move or flex easily, it still needs a specific shape in order to accomplish the amount of flexing that they're designing into the joint. More specifically, the material is not so soft as to not need the relieved areas at the sides of its cross-section.
- Although I haven't found any likely-very-easy-to-find-if-I'd-just-look-in-the-right-place installation instructions, it's clear that these joints are designed to be pressed into place; the steel or nylon sleeves have no provision for retention and the housings that they're designed to work with have no provisions for retention either...so that tells us (duh...) that these are not rebuildable in any way, shape or form. If you f*** one up you replace it, just like you would a Clevite bushing. To that end, the bushing in question cannot be designed to compete with the rebuildable options from a host of other manufacturers...and as it says in the description on Synergy's website, these are a replacement for Clevite bushings. Thus, if we're going to make any comparisons we're going to have to compare them to a Clevite.”
