While reading and watching movies on the tablet is super-nifty, holding it for two hours while reading or watching a movie is most definitely not.... and since I tend to do those things while lying in bed, I figured I needed to make a really cool bed mount. (This is really nothing new for me - about 10 years ago, I built a "bed mount" for a portable DVD player that works like a charm - but this one had to be a step up - See Step 14).
Since I tend to use smaller projects as introductions to new materials, I figured this would be a great opportunity to introduce myself to carbon fiber and epoxy on a smaller scale in preparation for some much larger upcoming projects.
Cost: is up there - I almost don't want to know - but I'd guess it's in the $300-$400 range with some of that being acquired tooling. If building a bed mount was my only goal here, I would have chosen a different method, but since I tend to look at projects like this as a vehicle for learning a particular skill set and acquiring specific tools and materials, I'm OK with the extra expense (how much would a college course cost you?). A mount of the same design could be built for less than half by choosing different materials (fiberglass) and tweaking the techniques - for example, choosing a wet-layup over foam technique over vacuum bagging in negative molds (but would require more cleanup).
General Materials List:
RAM mount - Model RAP-B-138U (sometimes, it makes more sense to buy something if it will work)
Kipp (brand) Lever Clamps
Hard Maple - or some suitable hardwood not prone to splitting under focused pressure
Carbon Fiber Fabric (8K Twill in this case)
Vacuum Bagging Material (plastic)
Mastic Tape (For sealing vacuum bags)
Polyester Resin and MEKP
Polyester Tooling Gel Coat and MEKP
Epoxy Resin and Hardener
Epoxy Glue - 5 and 30 minute versions
Spray Adhesive (3M Super 77)
Fumed or Colloidal Silica (Smooth-On's Cabosil) (thickener for epoxy)
PVA (Polyvinyl Alcohol - not to be confused with Polyvinyl Acetate) - Mold Release
High-Quality Carauba Wax
Urethane primer - or a good sandable primer
Catalyzed Urethane Clearcoat
Sulfur-Free Modeling Clay
Tempered Masonite (hardboard)
Melamine and assorted sheet stock
Smooth-On Plasti-Paste II (not required - just convenient)
Plastic wedges (SUPER helpful - worth every penny)
Chip (disposable) brushes, disposable graduated mixing tubs
Plastic squeegees (a couple will do - if you keep them cleaned off)
Gloves.... lots and lots of gloves.... A tyvek suit would be a good investment, too.
A **quality** Organic Vapor Mask and goggles
Vacuum Pump (some way of generating a vacuum)
Various fittings and tubing to run vacuum lines to your vacuum bag setup
Vacuum gauge - so you can see what's happening (probably not 100% required).
Sandpaper - Wet/Dry 320 and 400 - carbon fiber laminates eat this stuff quickly
Plus a bunch of smaller items like drywall screws, tape, hot glue, wood glue, carpet tape,
Miscellaneous tools: Drill press, table saw, bandsaw, router, dremel, files, wrenches, hand drills, saws, etc.
Safety: As you can see from the above list, you'll be working with some pretty nasty stuff. Since it would take me 30 pages to reiterate what already exists, I'll hit the high points of what goes through my mind when working with nasty/unknown materials:
- READ the MSDS (Materials Data Safety Sheets) that come with chemicals and know what they can do to you. This way, when you sprout that third arm because you were too manly to wear a vapor mask, you'll know why.
- Don't overestimate your capabilities - always bet on the conservative side of what you can handle until you're in familiar territory. It's far more embarrassing to lie on your garage floor crying for help than it is to approach things thoughtfully and progressively.
- Think through your process - what safety gear and props (paper towels, solvent, etc) will you need? What could go wrong? What will you do if something does go wrong? When you have a good idea, make sure all the things you need are readily at hand. Having a helper would be a really good strategy as well - but you should plan as if they're not there.
- When working with resins and epoxy, be *very* aware of what temperatures can do to your pot life and cure times. Most pot life estimates are given at around 72 degrees F - and you can figure that for every 18 degree increase in ambient temperature your pot life will be cut in HALF. Nothing sucks quite like being half-way through a layup or surface coat and have things start to gel - that's a mess with a capital "M".
- Carbon fiber - once trimmed can be ninja sharp. Watch out for those edges - and knock them down ASAP. I ended up with a littany of little cuts because I'd read about how sharp CF could be, but didn't realize that they meant SHARP-sharp as opposed to worrisome-mother-sharp.
- I can't stress enough the value of protecting your lungs, skin, and eyes at every opportunity - a $45 vapor mask is far cheaper than glass fibers in your lungs or being sick for a few days from polyester vapor exposure. You have to live in your body for the rest of your life - don't screw it up if you can help it.
- NEVER clean resin off of your skin with solvents. Solvents will carry the resin molecules through your skin - directly into your bloodstream (especially acetone and reducer). If you get resin on your skin, use waterless hand cleaner like Gojo Orange or similar.
I've included a few drawings - don't take them as set in stone - but they give something of an idea what I was thinking of ;)
I'd also recommend John Wanberg's Composite Materials Fabrication Handbooks
Note that there are SO many photos in this Instructable that I won't be doing a lot of writing - I'm going to let this be a "picture story" (my favorite kind!) :)
FINALLY: If you like this Instructable, please take a moment to vote for it in the UP! 3D Printer competition :) Thanks!
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Step 1: Making the Arm Template
I came up with two basic shapes for the arm.... and settled on the one that was harder to produce - lol. I wanted to get an organic look with a nice sweep to it - kind of "bone-like" in Steam-Punk kind of way ;)
Step 2: Making the Plug - Part 1
Once the template is established, it's time use it to make the stack for the "plug" which will be used to make the molds. Essentially, you're making the final shape that you want your part to take once it's transformed to a composite.
Step 3: Making the Plug - Part 2
Step 4: Making the "Tool" (Molds)
How to apply PVA: In a nutshell, not the way they tell you to (my first attempts sucked).
- Use a small-orifice gun (1.0 or so)
- Use around 100PSI at the gun
- Dillute your PVA 50% with water
- Turn the needle on your gun all the way closed
- Back the needle out about 1/2 to 3/4 turn
- If you can see the PVA on the mold as you spray, you're spraying too much. You should only be able to see the SHEEN from a glancing light. Use several coats - putting it on this thin makes it dry almost instantly.
Step 5: Carbon Fiber Tips
A few simple tricks with Carbon Fiber material....
If I had to describe working with CF material, I'd have to say it's darn close to herding cats - it's awesome stuff, but you really have to develop a feel for it as it likes to act like it has a mind of it's own...
Step 6: Layup, Vacuum Bagging, and First Pulls
Vacuum bagging is a slightly frantic operation - so you want to have everything laid out before you move ahead: Cloth, resin, breather, peel-ply, bagging material, mastic tape, hoses, etc, etc. You'll also want to cut everything to size ahead of time - the more prep work you do, the quicker and smoother the operation will go for you, and the less chance of messing up some rather expensive fabric and resin.
Step 7: Tablet Holder Plugs and Layup and Demold
The tablet holder, I decided, would be built using "sacrificial" plugs - both to try a new method and for expediency. In this case, the PLAN is to destroy the plugs upon removing them. Obviously, this is a suitable technique for a prototype, but probably not the best for production since it will create a lot of work on the back-end with cleaning up the layups (as you will soon see).
Step 8: Tablet Holder Construction
To improve the surface quality of the tablet holder parts, I decided to try a "float coat" of epoxy. Overall, it gave me enough thickness to level the surface. Epoxy is a great way to coat a surface - one layer of epoxy is equal to about 4 coats of urethane clear - BUT- epoxy that will be exposed to sunlight has to be UV protected either with an additive, or, with a UV resistant topcoat.
Step 9: Phenolic Hubs
Since the overall mechanism that locks the arm in postion is friction (via compression) - I wanted a "hub" that I could both glue and screw to the carbon fiber for maximum strength. I thought about metal, but decided that I wanted to stay with something that I could work more easily - and materials on hand.
"Phenolic" is a material class unto itself - there are dozens of varieties with a range of substrates. For the most part, it's a fiber substrate (cotton canvas, paper, etc) and a resin binder usually cured under heat and pressure. It's a really tough plastic - and I had some on hand - so it became my "hubs" ;)
Step 10: Arm Alignment and End Block Installation
Aligning the arms took a little thought. I needed to build a jig that would hold the arms in their final orientation and spacing so that they would not be under bending or twisting stresses (due to misalignment) upon final assembly. I made a jig out of MDF - and cut the "hole" for the main shaft instead of drilling it to make sure it was straight and parallel.
Step 11: Building the Base
The woodworking part of this project went surprisingly fast. I guess I was used to having to slog through 10 steps to get 1 final object - it was refreshing to work on the final raw material from the get-go :) Building the mount assembly took less than a day, and is made from hard maple.
Step 12: Finishing
Ah, yes, spraying finish: a time of alternating euphoria and terror. Moments of glossy goodness punctuated by orange peely and runny terror. I've always heard the saying, "Nobody notices a perfect finish" ...... which means that all my finishes are doomed to be noticed - LOL.
Maple - like Pine and Cherry - is very difficult to stain without blotching. For this reason, I chose to spray NGR dye (Non-Grain Raising) - which is nice because you can "shade" the piece if you wish. I mixed up a darker version of the base color to add a patina around the edges of the main mount body.
For the clear finish on this project I used a catalyzed urethane - very tough stuff.
Step 13: Assembly and Final Details
Final assembly is always fun - it's like Christmas - as long as everything goes together the way you thought it would :) All the pre-assembly and fittings pay off when the parts go together without drama - no last minute cussing and grinding....
Step 14: Beauty Shots
I'm pretty happy with this overall and I learned a TON in the process. Funny thing is: as soon as I was finished, I was making modifications to the design in my head - lol. Watch out for Tablet Mount 2.0! :)
I hope you enjoyed reading through this Instructable :) If you enjoyed it, I hope you'll vote for me in the UP Printer Contest
Thanks for reading!
PS: Be sure to check out the OM (Original Mount) in the next step...
Step 15: Origins
First Prize in the