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Old 11-01-2013, 01:25 PM   #181 (permalink)
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Quote:
You have good ideas, though in this case I happen to favor my idea (or maybe it was a coworker's idea, sort of):

This is pretty much what I was suggesting, held at four points instead of two, but with front bars of 0 length. It even over-centers.

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Old 11-01-2013, 08:10 PM   #182 (permalink)
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Quote:
Originally Posted by freebeard View Post
This is pretty much what I was suggesting, held at four points instead of two, but with front bars of 0 length. It even over-centers.
*Rereads Four-bar linkage - Wikipedia, the free encyclopedia*. Now I get it, I did make a 4-bar linkage. Cool. (Mechanical engineering isn't my native language, I must confess.) But you lost me again on '0 length'. If a bar has 0 length, then 2 hinge axes must coincide, which is not the case here.
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Old 11-01-2013, 11:33 PM   #183 (permalink)
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Great Job!

I also live in Utah. I drive a 2006 Civic Hybrid and always wanted to try something along this line.

Do you have an issue getting the Utah inspection? Or do you disassemble for that process.
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Old 11-02-2013, 10:30 PM   #184 (permalink)
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christofoo -- That's because I was wrong. I wasn't looking at it right. Normally you have four linkage bars that constrain the moving item (your classic street rod front end). In this case the two bars swap function with the other items.

For the sake of the lurkers [behold the magic]:


a related concept is the three-hinged arch
https://en.wikipedia.org/wiki/Arch#F...vs_hinged_arch
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Old 11-03-2013, 01:51 AM   #185 (permalink)
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Quote:
Originally Posted by MorphDaCivic View Post
Great Job!

I also live in Utah. I drive a 2006 Civic Hybrid and always wanted to try something along this line.

Do you have an issue getting the Utah inspection? Or do you disassemble for that process.
In my reading of the Utah inspection manual, I'm not sure whether or not the Kammback may be viewed as a "hazard" beyond the bumper. I may eventually do some more engineering to the sharp edges and try getting it inspected with the Kamm on.

Optically I expect it's fine (I could be wrong). I should probably go back and check the manual for verbiage on frost lines, which I need to think about anyway, and while I'm at it see if I missed anything I might need to worry about on obscuration or distortion. (Year after year my Corolla gets passed, and it has bubbling tint in the rear window which is at least as bad as the Kammback's little imperfections.) You do get blocked for removing the passenger side mirror with any tint on the rear-window, however. Now that I'm doing a Kamm with a shady section I wish I hadn't tinted the rear.

I must have done my inspection a little late this year (June instead of May) because I remember taking the hitch box off. My belief is that being hitch mounted, it's in the same class as other hitch-cargo-carriers, and as such it's not to be inspected, and I presume would just be a nuisance.

It'll be May again before a definitive word, but I'll keep you posted.
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Old 11-16-2013, 05:31 PM   #186 (permalink)
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Full boat-tail

The gap-filler window is on the road, although I might need to remove it for the road-trip at the end of this month, not sure yet. However, here's the car in full boat-tail-configuration:




I forgot to mention; I also painted the hitch box lid black, since that is the component that sits in the reflection in the boat-tail windows. The darker and more matte the lid, the less interference you see in the windows.

An idea how it's built and attached:

The screws go through the hinges into jack-nuts installed in the acrylic. (I have to look up on Mcmaster to see if I'm remembering the right name: also called screwdriver-installed-rivet-nuts.)

The cut you see was needed to 'shrink' just a bit, as an adjustment to get the piece to mate with the Kammback.

I decided the gap-filler-window needed to be totally transparent. So then how do you heat the acrylic (PMMA) to bend it? Last time I tried a heat gun, and it took forever. This time I used a little propane plumbing torch. Easy!

An idea what the view looks like, from the point of view of the driver (turned to the left, like if you were backing up):


There is potential trouble with cold precipitation, which I'm expecting on this road-trip, so unless I'm really on it and get a 12V defroster contraption wired up, the gap filler will probably sit this one out. Also, being acrylic, it can't be scraped for ice (I checked with a piece of scrap - it got scratched up).

Apparently I didn't shoot these so you can tell, but I'm pulled just off the frontage road not far from the Salt Lake, there's a rather flat segment of a couple miles with newish pavement - a rather good place to coast-down when the wind is down (which happens here and there).

Unfortunately the GPS did something bizarre and the data is more-or-less garbage:

You might think this is something I could process my way out of, add some smoothing, or cut the weird points, or better yet if I could find evidence of the phone's clock skipping around. I looked at the raw data closely and couldn't see any neutral way to reprocess. I think this is the first time I've captured GPS with the music player running, maybe that's at fault. There may be ways to get better GPS data with a different app (this was MyTracks). I've also got a low-end bluetooth OBDII dongle and the Android Torque app, so I've tinkered a bit with the OBD speed sensor, which outputs an integer km/h. Unfortunately I haven't got the too-cheap knock-off ELM device to delivering reliable short polling intervals - in other words, rounding would be fine if the polling interval could be minimized so I could get an accurate time stamps on the km/h splits, but otherwise it's a mess.

Thinking it's about time to go to the robust DIY solution: a bicycle computer.

But I'm probably just going to focus on the wheel skirts, grille block, maybe air dam for now. Back to testing and fine tuning my boat-tail later.

Last edited by christofoo; 11-16-2013 at 09:07 PM..
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Old 11-16-2013, 05:56 PM   #187 (permalink)
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Wow, this has come a long way!
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Old 11-16-2013, 08:58 PM   #188 (permalink)
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OMG. I get excited about this everytime I look at this thread. Great work!! I can't wait to follow suite and do something like this for my car. Thank you for your awesome design!
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Old 11-16-2013, 09:36 PM   #189 (permalink)
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I love going through these big build threads to see what can be done to show that aerodynamics = better fuel mileage. I cant wait to see what kind of mpg you will be getting with all the hard work you do!
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Old 11-23-2013, 12:18 PM   #190 (permalink)
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Added " / Boat Tail" to the thread title.This sure has come a long way.

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