0 Members and 1 Guest are viewing this topic. Read 36687 times.
Steidl and steve1580,The failure photo I posted was from a project by Steve Manning who frequents the htguide.com Mission Possible DIY forum.Here is one of Steve Manning’s builds in partnership with JonMarsh. These are laminated bamboo plywood picture from page 24 of the long detailed build thread. http://www.htguide.com/forum/showthread.php?43049-Minerva-Monitor-quot-Patience-my-ass-I-m-going-to-go-build-something-quotSteve wrote about the failure he suffered in a previous project:“Hey Ryan ..... after I had mine crack I did a lot of research online into the issue. First, I was rather surprised by how much the BB actually moves over time, I thought it was a lot more stable. That being said, sealing it helps but will not stop it it completely. I think the biggest part is learning to work with it and not constrain the layers from moving. What I found in most cases where these projects crack and what I did myself, is we glue the baffles, backs, sides, what ever, in place across the lamination's. This "try's" to prevent the wood from moving ....... not. If you look at say what Magico did when they used BB with the aluminum baffles and backs for their cabinets ..... they had o-rings in the baffles and backs and the two were bolted together as a unit. That way they floated independent to the wood portion of the cabinet. That way the BB could breath as needed without cracking.This is of course all conjecture on my part, but I don't think I'm too far off.Steve”So restating what I read Steve saying and the opinion I have is yes “a glued joint is much stronger than the wood plys themselves” and that is exactly the issue. The baffle glued at a right angle to the laminated buildup moves most along its length and when solidly glued to the plywood or MDF stackup that movement can cause a failure. HT cOz gets it and now has in his design an air tight interface between the horizontal laminated sections and vertical baffle.Here are a couple of pics of my last translam design, the baffle is glued using RTV with ~1/16” ~2mm clearance space all around between horizontal laminated plywood layers and vertical baffle.Another hint/encouragement to HT cOz is I see in the renders holes I presume are for alignment. Good! Aligning the layers during the glue-up is vital unless you enjoy descending into sanding purgatory where time stands still as innumerable sanding sheets clog and sanders’ motors expire. I have tried the following alignment methods:All-thread metal rods. The idea was to get both alignment and clamping. Big fail, if the alignment holes are large enough to get the plywood down the all-thread the layers do not align with sufficient tolerance. Also a builder on DIYaudio.com who did a six foot tall translam line array and left the metal rods in suffered cracks when the differences in the thermal expansion characteristics of wood vs metal happened.While gluing manually align each layer and pin with brad nails. Better but makes gluing (even more) slow and tedious and is still prone to misalignment.Use wood dowels in holes as in your render. Best solution I have used, my speaker shown above used ¼” dowels in ¼” holes and the layers were very well aligned after glueup. I used the short dowels one can buy precut for making doweled wood joints. I would not use long dowels, they will bind up as you try and slide the layers down them. I had extra alignment holes so when layers 1 & 2 filled a hole I moved over to the adjacent hole for layer 2 & 3. Then the original hole is available again. Or you could custom cut dowels long enough to align but short enough not to fill the hole so it remains available for the next layer. In your renders I see 8 alignment holes. In my experience 4 is plenty so you could alternate which four you use as the layers are added. Final doweling hint is if like me you only drill the alignment holes partly through the top and bottom layers check the dowel length protruding to align that top plate. I almost cracked one when the alignment dowel bottomed in its hole.
What's the projected cost of this build?
Are you planning on selling these? If not, mind sharing the cost of the CNC and finishing?
I like the cabinets, quite beautiful actually. Didn’t know you were in Chennai, my family’s hometown.Best,Anand.
Wow it's a small world. I'm working here on a three year assignment with about seven months left. My family stayed two years, so in the last year I've been occupying my time with speakers and amps etc. Chennai is amazing for building and doing work in general. Inside and outside of the office I'm very impressed with the people. It does take a little time to see through hustle and bustle of India. A few more renderings... \ \ \Ivica thinks of everything... lol
