Translam Subwoofers with 18" Passive Radiators - The Jedi Mind Tricks

[KEtheredge87]

Hi Everyone,

Today I finally got started on the top curve cutting jig! I took a lot of inspiration from Jamie Yocono's blog post and youtube video and made an 80" router trammel to help me cut my top radius. From there I made a matching side with the router table, and then lined everything up and secured it with pocket screws. The top of the subwoofer to be cut, is held in place on the particle board table piece below by accepting the dowel pin nubs that are sticking out from the bottom of the part. The curved jig itself is also screwed down to the particle board, so the only way this subwoofer top should be able to exit the jig is by coming straight up vertical. I do not expect that's going to happen given the substantial weight of this thing.

The challenge of the moment is to shore up the long runners that will glide over the radius guide. Right now, it's just two side by side layers of 3/4" baltic birch ply scraps. This needs some extra reinforcement so that the router can't deflect up and down, which would give me a wavy, inconsistent depth of cut across the top. I'm heading to the hardware store to pick up some 1/8" square aluminum tubing. I'll be screwing this tubing to the top of the runners to provide additional stiffness. My hope is this does the trick, as I'm excited to try this cutting setup. I've got a 1" straight cutter from Whiteside all chucked up and ready to rock and roll!

More updates as I progress. Thanks for checking in!

[tomzarbo]

It's getting interesting! I was thinking a 4-5" tall piece of 1/2" ply glued on and oriented vertically on each would keep the strips of plywood from flexing. Kind of like a 'T-Beam' if there is such a thing. You'll know if the aluminum will reduce flex sufficiently soon enough though at the rate you're going. You're really making progress quickly.

I'm curious if you plan to make two passes... The second one with a finer bit for less tear-out? That bit looks AGGRESSIVE!

TomZ

[KEtheredge87]

...I'm curious if you plan to make two passes... The second one with a finer bit for less tear-out? That bit looks AGGRESSIVE!

Hey Tom! Yeah... I debated for a while about which bit to use. Thinking of this cut like I'm mowing the lawn... going with a smaller diameter mower means I'd have to increase the number of back and forth passes to finish the lawn. True to form with my actual lawn... this lawn is overgrown, and will need a few complete mowings with incrementally lower blade heights to achieve the right look. May even take 3 or 4 passes to reach the right depth without being too aggressive.

As for a finer bit... I spoke with Kevin K. about this a little. I had considered using a bowl or round nose bit instead of a straight bit so that the tip of the cutter wasn't digging away so aggressively, but then Kevin reminded me that I would need to make my left-to-right steps in small fractions of an inch to avoid getting an obvious stripe pattern that would require more finish sanding to remove. I may be in for a sanding challenge anyway!

I need to shore up the runners before I'll find out, so I think this little guy kinda sums up my state (or at least makes me laugh)!

[Kevin K.]

Man you are flying through this project! Really wish I could have got back with you on the design changes for the fixture, one of my concerns was the long runners and they would have to span. The change I had in mind is similar to what Tom suggested and it would have had some 3-4" vertical pieces to act like a truss and prevent the weight of the router from flexing them. You'll figure something out, I'm sure. Best of luck and stay alert when you start using that cutter, keep both hands on the router firmly in case you get a kickback for some reason, last thing you want is that router flying around out of control.

[KEtheredge87]

...one of my concerns was the long runners and [the distance] they would have to span.

... Best of luck and stay alert when you start using that cutter, keep both hands on the router firmly in case you get a kickback for some reason, last thing you want is that router flying around out of control.

Thanks Kevin! You're absolutely right. I want that router staying firmly planted on the runners. I'm going to take my time and let the router do the work here by taking very shallow passes. It will take more time, but I think the result will be better than trying to hog material out at rapid pace.

Instead of using more plywood to treat this like a T-beam, I went back to my college days at the UK solar car team and used some square aluminum tubing. I drilled through holes for #8 sheet metal screws, and added a washer for good measure. The holes look bigger on top because I needed to drill those out and make room for the nut-driver to fit through. With those aluminum tubes fastened down, that sucker is NOT moving.
Mission Accomplished

The only other things I plan to do before starting a cut are to give the rails and runners a quick buff of paste wax to reduce unnecessary friction, and add a little rail guide with c-clamps to keep me from drifting around too much. One of the pictures below is a YouTube screenshot from the video I linked a few posts up that shows what I'm talking about. Tomorrow night I may have some good cutting updates to share! Stay tuned.

[KEtheredge87]

Well Guys... the moment has arrived. I finally started to cut the curved top!

I went through the pre-flight checklist, paid some guy to say "GO!" into a walkie talkie after every line was read off, checked and double checked the final router plunge depth, spun the depth turrets all the way around, lined up the first cut, and prayed... "Oh Lord, please don't let me mess this up!"

Turns out the jig I built is working well, and the router cuts are nice and easy! I'm working from left to right, and pulling the router toward me from the back to front (always doing conventional milling). I'm nibbling through the top one turret turn at a time to make sure I'm staying in control of the router, and to be nice to the bit. So far it kinda looks like a hammered pattern where I am moving the router from left to right. I'd imagine some part of that is my choice of moving the bit over slightly more than 1/2 the diameter each time. When I do the final router pass I'll use a smaller increment there.

Ultimately, I think I'll get down to about 1/16" from my final depth and switch over to a large sanding block. This way I can smooth out any remaining router lines and leave the surface prepped for finishing. At this rate, I think I've got about two to three more days of routing to finish this part, as well as the second one.

Tonight was fun! Love it when a plan comes together.

[Kevin K.]

Looking good Keith! I wouldn't shy away from that final cut, 1/16" is a lot to sand off end grain of plywood. The cutter looks like it's doing a pretty good job (no tear outs from what I can see), let it do the work. You should just have some light sanding left for the final clean up. Best of luck!

[scottvalentin]

Wow that is really looking good!

[jhollander]

Looks cooler than I thought it would!

[KEtheredge87]

Thanks Gents! I'm excited to see what this looks like once I get a smooth curve into all the layers!

Kevin, I will see how much courage I can bolster and put my faith in the cutter. The cuts do come out smooth, I just wonder if things will literally get chippy when the depth of material I remove gets smaller and smaller toward the front of the boxes!

[Kevin K.]

Thanks Gents! I'm excited to see what this looks like once I get a smooth curve into all the layers!

Kevin, I will see how much courage I can bolster and put my faith in the cutter. The cuts do come out smooth, I just wonder if things will literally get chippy when the depth of material I remove gets smaller and smaller toward the front of the boxes!

Only one way to find out!

If it starts chipping, you probably have some lead way in your design and could afford to remove a little more from the top by hand. I would suggest a belt sander if it comes to that.

https://www.amazon.com/Decker-DS321-Dragster-3-Inch-21-Inch/dp/B0002ZU73I/ref=sr_1_3?ie=UTF8&qid=1497452895&sr=8-3&keywords=hand+belt+sander

Warning, if you end up having to use this Keith, practice on a scrap board. It's super important you keep the belt sander flat or you can end up with gouges where the edges of the sandpaper dig in. Just the slightest tilt to the left or right and you'll see what I mean. One method that can help prevent the gouges is to sand front to rear but hold the sander at a 30 or 45 degree angle. Sorry for the lousy explanation, don't know how else to say it.

[badman]

That sled method is something I've been meaning to try, I'd like to do some radial horns and a curved track, pivoted on the throat point would be the best way to do them it seems, but the jig would be complicated, rather than pivoting the jig, seems like rotating the horn itself would be the trick.

Enough of that, nice work!

[tomzarbo]

Looks great.
The look is complimentary to the sides. I had a tough time seeing it in my mind previously; now I see what you envisioned. I suspect getting the final little bit smoothed out won't be too hard. Must see TV!

TomZ

[KEtheredge87]

One top down... one top to go!

Tonight I finished the router cuts on the top piece of the first cabinet. I went all-in as Kevin suggested and it turned out great! I appreciate the encouragement there... even though the project kinda forced my hand into going all the way. Stopping short of that last cut would have left a small ridge where one of my glue-ups occurred (would have left that spot un-radiused). I even got treated to uncovering a cool knot in the frontmost ply up on the left hand corner. I think it's really cool peeling back the layers like this a little at a time. Risky, but sometimes also rewarding like this little subwoofer birthmark!

A few comments overall... First the Whiteside bit did a fantastic job. I only had one tiny instance of tearout (I think... kinda hard to tell), but that should easily be blended in with some Timbermate wood filler. Also I found out that I didn't drill deep enough when installing those walnut dowels, as I actually cut all the dowel away leaving a small open hole on the back two dowel pins. I'll clean those out a bit and re-install some dowel pieces. Nothing the flush trim saw can't fix!

Also...I got to actually sit the top on the rest of the cabinet! It was so satisfying to see this whole cabinet actually LOOK like what I had modeled up in CAD over the last few months!

I'll have to work late-ish tomorrow, so between Friday night and entertaining folks this weekend I'll try to carve out time for more routing... oh geeze... unintentional pun!

Thanks again for all the support you guys continue to provide! Helps keep me going!

[scottvalentin]

Outstanding!!