CNC Build: The Bed and Breakfast at 4 years and 40,000 miles

[tony.latham]

Holly Buckets! You're really thinking outside the Teardrop shaped box. I'll be curious to sit back and watch how you seal the upper edge. Something tells me you've got a plan.

Tony

[RandyG]

I love this idea and how you did it, even just your test piece looks good. I may change my plans of a piano hinge.
You have it pretty close so far, I bet you have the solution in your head now. But if comparing it to a car trunk, the trunk is flat,your hatch is at an angle so adjusting the angle may get you closer. Are you just going with two hinges or will you opt for more? A good gust of wind can put a lot of stress on a hatch.

[KCStudly]

So long as the hinge center line is ahead of the forward edge of the hatch skin, and the plane of the bottom of the hatch skin is above the hinge center line, won't the skin lift up off of the seal and roof skin, rather than pivot into it? Additional separation between the surface of the skin and the hinge point may be needed to account for degree of opening and curvature.

That's an interesting detail to noodle out. Hope you are using some sort of 2 or 3D modeling.

+1. Be careful not to under estimate the forces at work on a hatch hinge. Between the weight of the hatch cantilevered on the lift struts and the leverage back to the hinge point, a lot of force can be generated.

[aggie79]

Cap'n Brad,

That is a very interesting and ambitious plan. I'm pullling for you to get it to work.

Take care,
Tom

[KCStudly]

Cap'n Brad,

That is a very interesting and ambitious plan. I'm pullling for you to get it to work.

Take care,
Tom

(In jest) If I may translate:
"What are you crazy? Boy if you get that work I sure will be surprised. This ought to be good for a laugh."

But seriously, it is always interesting to watch (dare I say participate?) when someone is breaking new ground, and there is a chance of creating a new fad, craze or "better mouse trap" way of doing something. This will be interesting, and like we say, "somethun's gonna happen". Let's hope it works well!

[capnTelescope]

Something tells me you've got a plan.

You bet your bippy I've got a plan! Doesn't mean it's gonna work, but I've got a plan. Don't try this at home, kiddies, unless you've got a CNC machine. Basically what I'm doing is laying out the strut in CAD, over the back end profile, and making the g-code directly from that. It's all about accurately locating the hinge and correctly taking account for the skinning of the hatch and the Tear. We need a smiley for "sweating bullets."

I may change my plans of a piano hinge.

... then

Don't try this at home, kiddies, unless you've got a CNC machine.

I wouldn't have tried it, otherwise.

comparing it to a car trunk, the trunk is flat,your hatch is at an angle

Even a car trunk has a slope, just not as much as a tear. They rely on water's propensity for flowing downhill. What I see as the big potential fly in the ointment is that most car trunks don't bend back toward the front, like my profile does..

Are you just going with two hinges or will you opt for more?

I haven't decided yet, but keeping the hatch true to form is important, so 3 or 4 might be called for. Not to mention wind gusts.

Additional separation between the surface of the skin and the hinge point may be needed to account for degree of opening and curvature.

You are correct, sir. I'll probably move it back fairly near where the point on the strut is. It gives a larger radius from the hinge point, so the edge goes up faster than it goes forward.

That's an interesting detail to noodle out. Hope you are using some sort of 2 or 3D modeling.

Yes, and yes. The planning was done in 2D, but I needed the mock-up for 3D modeling. I can't seem to get my brain around either 3D CAD or how this was going to look.

+1. Be careful not to under estimate the forces at work on a hatch hinge.

Amen. +1 more. The final design might have double-thick parts and/or other strength-increasing features, including joinery to the bulkhead.

I'm pullling for you to get it to work.

Meee too. Squeeze!

"... Boy if you get that work I sure will be surprised. This ought to be good for a laugh."

+1. that's two of us. I'll bring it by for you to look at.

This will be interesting, and like we say, "somethun's gonna happen". Let's hope it works well!

If worse comes to worst, there's enough meat on the walls to do a hurricane hinge. Boring.

Thanks everyone, for the comments. Read on for the day's developments!

[capnTelescope]

More R&D today. rolled out hinge 2.0:

Reeeeal close, but still cigar-less.

Then I said to myself, "Self, did you account for the thickness of that 1/4 ply you mounted the hinge on?" Then I said to myself, "Self, no I didn't. Quickly! To the table saw!" Shortly therafter hinge 2.1 was up:



Pictures don't really do it justice. Maybe this:

I'm going to try a full length one tomorrow.

Thanks for stopping by!

[capnTelescope]

For the idly curious, here's a couple of printscreens from the CAD.

Hatch shut:


Hatch open:


Notes: The zigzag in the hinge end of the spar is clearance for the 1/4 ply it's mounted on. Also ignore the little fishhook thingy. What do you expect for <$100 CAD? (DesignCad 3DMax)

This all brings up another question. The bottom of the hatch when open is barely taller than I am. How high is your hatch bottom when open?

Thanks for stopping by.

[AlgoDan]

Absolutely brilliant Brad, you come up with some interesting and challenging ideas. I sit here and watch and read your build in amazement. Your hatch will work and seal and you will be smell the camp fire soon.

[RandyG]

I guess a main point of all of this is to get the hinge point tucked under the end of the roof huh? The further forward you can get the hinge point makes for less of a pinch point and gives you a little more clearance. Or you can just extend your roof, is that the plan?

[capnTelescope]

Absolutely brilliant Brad, you come up with some interesting and challenging ideas. I sit here and watch and read your build in amazement.

Awww, shucks Dan. It all came to me during my third and final career (auto mech), when I was working on someone else's car. I looked at the trunk and it hit me, "That's a galley hatch!" I've been wondering ever since if I could do that on a tear.

Your hatch will work and seal and you will be smell the camp fire soon.

I sure do hope so.

I guess a main point of all of this is to get the hinge point tucked under the end of the roof huh? The further forward you can get the hinge point makes for less of a pinch point and gives you a little more clearance. Or you can just extend your roof, is that the plan?

While I was figuring this out, I discovered that up high is what makes this work by giving you the highest opening. That's why the H-Hinge works so good.
Just gave myself an idea! Stay tuned...

Or you can just extend your roof, is that the plan?

Yes, I'll do that too. Unless that sudden inspiration works out.

[capnTelescope]

Quick video of hinge animations, including a first look at Hinge 3.0!

[capnTelescope]

Did a quick mockup of Hinge 3.0. Results are very promising.



I'm now getting a much better open angle. I may not have to worry about bumping my head, now.

This design works because the hinge has a deeper throat. BTW, Deeper Throat is now a serious finalist in the Name This Teardrop contest. I wonder if I can get that on a license plate? DPRTHRT?

Thanks for stopping by!

[RandyG]

Why not try a search online for "deeper throat" just to make sure that name hasn't been taken.

Looks much closer, nice work!

[capnTelescope]

Why not try a search online for "deeper throat" just to make sure that name hasn't been taken.

Because I have yet to think a completely original thought and surely someone else has thunk of this before, given the fame of mere "deep". Someone probably even named a movie that. Go figure.

OTOH, now curiosity has got me. Who knows what I'll find?

OK, I couldn't resist taking a quick look before I posted. They actually made a Tow Vehicle series by that name! I wonder if there's any Teardrops in it?

back atchya.

Oh, and thanks for the good words.