University of North Dakota Industrial Tech Build

[logan.tong]

Greetings, All

My build started several weeks ago, but I've been documenting it the whole way. You can read about the origins of this particular TD project in my intro post.

I bought the HF 4x8 trailer in September, and it's been slow-going to get it prepped and assembled, but this week we finally go the deck completed. Next week we cut the sides on our ShopBot CNC table. More detailed descriptions of the images below are included in my gallery.

[Ron Dickey]

how is the build coming?

Cal poly san Luis Obispo school of architecture offers an event where schools come from all over with designs that can be built on the spot and taken down or moved quickly. emergency shelter ideas. many are quite teardrop like.
go to google images and enter
"cal poly poly canyon competition event"

Hope you learn a lot on your build

Ron

[logan.tong]

This build's progress has been dictated by so many different factors. Because I want students to have hands-on experience, I've needed to try to divide tasks on the trailer into small, relatively easy to understand steps that students can do in hour-two hour increments. I also prefer to be there to oversee the progress and answer questions. Since I have job responsibilities in the department, and they have normal college student schedules, it can be pretty hectic finding times I can be there when they are. The students also had other responsibilities in their wood products class, including a great community engagement project that was featured on our university's home page. http://und.edu/features/2014/12/toys-for-tots.cfm

If you watch the video, you'll catch a few glimpses of my project in the background. Since my last post we have completed the floor assembly. I also learned to use a machine I hadn't tried before. We have a ShopBot CNC that is well used, and abused. I wanted to use it to cut the wall profiles, cutouts for insulation, dados for cabinets & roof spars, and a channel to run the ceiling panel through. My first real use of the ShopBot was on the top floor panel. If I squared it properly to the table, I could get both sides very cleanly cut to the proper width. Unfortunately I made a mistake on the first go, and routed a 1/4" dado in a 12" section of the floor.

Before I cut the floor, we spent a lot of time deciding how to frame the floor sandwich. The bottom was 5/8" ground-contact-grade green-treaded plywood, which I had planned to coat the underside of with elastomeric roof coating. Someone, at some point, thought my bucket of coating looked like a good door stop, or perhaps belonged outside because it featured illustrations of a snow-covered roof. Well it was quite cold by the time we found it. Frozen solid from the overnight temp of 0°F. I'll get under the trailer at a later date and seal it with fresh coating once my anger over losing the first bucket subsides.

Anyway, we drilled and countersunk the 2x4s through the treated ply where the frame cross-rails already had holes. We finger-tightened bolts and cut the foam panelling to do a dry-fit. Once all the pieces were ready, we labeled every piece, took it apart, and applied liquid nails to every mating surface before tightening down the 3/8" bolts with lock washers. I wanted to make sure it was perfectly flat while the adhesive set, so we took it off the bench and laid it face down on the flat shop floor for a few days with a few hundred pounds of shop materials.

Here's a student marking bolt locations on the sides of the 2x4s so I knew where not to screw when we got the top on.


Dr. Johnson securing the floor down after we spread two tubes of liquid nails over the subframe. Notice the "feature" dado I mentioned earlier.


This is a test cut with a piece of scrap MDF. After the troubles cutting the floor on the CNC, I needed to make sure I could get it to do all the complex cuts without deciding to suddenly slice the panel down the middle. You can see the dados for the galley cabinetry, and part of the channel for the ceiling panel. In doing those cuts, I found them not to be uniform depth across the piece, which tells me I need to run a leveling program on our CNC to plane down the surface of our sacrificial board. With so many dados, it's really important that I get everything as close to zero as possible.


Another angle. You can see we used this panel to catch overspray when painting the trailer parts.


Its now winter break at the University, so I plan to go in while it's quiet and become more familiar with our ShopBot, and hopefully cut the walls soon!

[KCStudly]

Can't hardly see that dado from my house. Easy fix to glue a piece of fir in there and shave it back flush again.

I think it is a good thing you are doing there.

One area that I encourage you to rethink is the thin groove concept for the ceiling panel. How do you picture the assembly going? It will be really hard to get both walls and the ceiling to go together all at the same time, with glue squeezing out and running down the walls, juggling.

It is a much more common method to have a rabbet or ledge notched on top of the wall so that the ceiling panel cab be laid down after the walls are fixed in place. This also provides more of a margin for slight variations in the edges of the ply, especially after splicing sheets together when the edges aren't perfectly straight or by bending the ply it wants to walk to one side or the other. Unless you attach your spars to the ceiling skin first, you may find that it will sag in the middle and not stay in the groove. How do you intend to fasten it?

If you are concerned that you do not have enough wall thickness for this, you could always add an arc of blocking, like corner trim along the top inner edge just below your existing groove, then scarf away the face of the wall ply above the groove so that the panel can drop down on top of the trim. The trim would give you a nice wide surface for glue and to take screws or staples.

I don't mean to sound critical, just trying to help share what I have learned from my own efforts and those of others that have gone before.

[logan.tong]

Can't hardly see that dado from my house. Easy fix to glue a piece of fir in there and shave it back flush again.
....
One area that I encourage you to rethink is the thin groove concept for the ceiling panel. How do you picture the assembly going? It will be really hard to get both walls and the ceiling to go together all at the same time, with glue squeezing out and running down the walls, juggling.
.....
I don't mean to sound critical, just trying to help share what I have learned from my own efforts and those of others that have gone before.

Thanks for the advice! I can see your point about the trouble getting everything together with little hassle. In my overly-optimistic minds eye I had pictured several hands helping fit the walls and cabinet pieces into their respective dados, and lagging the wall at the base, and putting a few spars across the top, then smoothly sliding the ceiling panel in from the galley. I'm sure it won't be as smooth as I want. After that I will finish-nail the ceiling panel to the spars above it. I'll certainly consider your suggestions before we start cutting, thanks!



You can see the working version of my CAD drawing for the wall. Red is outer cut. Yellow is through-cut for door ad insulation. Green are the dados for ceiling, spars, and cabinets.

[Gold5one]

Ah, the fond memories of my shop class come trickling back. The skills I learned in shop class 50 years ago have served me well. I'm glad to see some schools still value the manual shop arts.

[capnTelescope]

Great project, Logan. This will be a big learning experience for you and the students. This is very similar to my CNC build. Let me throw out a few quick nuggets for you to consider.

Unforgiving Rule No. 1
Always check your Shopbot gantry for squareness before you cut any dimension that requires squareness. Your shopbot is probably much more robust than my kit built CNC, but still... Any squareness error on the sides will be doubled when you cut the mirrored wall.

Unforgiving Rule No. 2
Program critical fit dimensions, especially dadoes, using the actual cutter diameter. Router bits are often undersize to nominal. An undersize bit will cut an undersize dado.

I considered dadoes for my bulkheads and shelves, but went to lumber framing to be able to screw into at assembly. The CNC cuts the reference edge of the lumber to true. I foresee a real challenge getting all the walls and counters assembled and glued up. Probably OK if you glue up one side complete, then the other.

The slide-in technique for the ceiling should be OK if you do 2 things: Don't go for a tight fit in the ceiling groove. Leave some room for the for the ceiling to bend and slide in easily. Also, consider using 1/8 ply for the ceiling. It will be more bendy in one direction. The bendyness will make things much easier to slide the ceiling piece in.

Your "feature" dado on the floor won't be the last. Don't sweat the goofs and feature cuts. You can always glue on more wood and try again. How do I know this?

You and your students are off to a good start. This is fun. go with it.

[logan.tong]

Quick update on a big step. Finally CNC cut the wall panels. Took 90 minutes for each wall.

[capnTelescope]

WTG, Logan

How about a picture of a completed wall?

[logan.tong]

Had to check the fit!

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[Gold5one]

I like what you have done!
Now, if I could just find a senior living apartment in about 10 years that had a full wood shop with this eqiuipment, I would be happy. But, alas, I am not a golfer or a doodler or a thumb twiddler and I doubt that any senior center has a CNC cutter.

[capnTelescope]

Looking good! Before you apply even 1 drop of glue, you need to cut out your vertical and horizontal panels and face frames. Make sure you know how to put this together. For one thing, I'm not sure how you will get your ceiling panels into place. I'm sure all will be revealed in time, and you have many more hands available than I did. The whole thing should able to dry fit together with maybe a dozen screws before you go to glue. I spent quite a bit of time in dry fit when I reached this stage, just to be sure I found the unforeseens and had a good assembly plan. As it is now, the walls can still go back on the CNC router to take care of any necessary revisions. It's too late after glue sets up.

Keep up the good work!

(Maybe I shouldn't do "beers." College kids mostly aren't legal drinking age, and wouldn't drink beer, would they? I don't remember. )

[capnTelescope]

I doubt that any senior center has a CNC cutter.

Dell Webb's Sun (sin?) City here has a nice woodshop, but I don't think they have a CNC. Bring your own.

[logan.tong]

Thanks guys. I plan on having a few students on hand, and every part of the cabinets and roof spars ready to go for a dry fit. I'm sure I'll need to make some adjustments. I'm just glad they match! Making sure the 4x8 plywood was square to the CNC both times was the worst part. Our shopbot likes to lose coordinates on a regular basis.

For anyone wondering, this was 3/4" birch, and I used a 1/4" double-fluted up-cut end mill bit running at 18000 RPMs, cutting 60"/minute at .20" step-down. that was a mouthful!

[logan.tong]

I doubt that any senior center has a CNC cutter.

You could see if there is a maker space near you http://spaces.makerspace.com/makerspace-directory