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Old 01-20-2018, 05:45 PM   #61 (permalink)
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Quote:
Originally Posted by samwichse View Post
I wonder...

If you're leaving the top unenclosed, a nose design that directs the air around the side more, instead of over the top might be more efficient.
I'm enclosing the top. I just don't have the piece to do so ready to use yet. It will also have a windshield and roof.

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Old 03-23-2018, 01:27 PM   #62 (permalink)
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I got some more pics last night with a friend's phone:

Rear view:



Angle view:




I'm going to source material for a windshield today. The roof piece and turtle deck piece are finished but not yet installed. I'm also going to install the sealing tabs on the mid-section piece so that there are no gaps for the air to penetrate on the sides, reducing drag further.

It's much faster than I thought it would be, but I don't yet have a torque sensor or objective way of measuring power requirements to figure out CdA, Crr, and drivetrain losses. The goal is a CdA of 0.15 m^2 or less. I don't think it's there yet, but it will probably get there.

Note the new rims. The KMX rims kept breaking spokes. On Monday I had a local bikeshop lace some Velocity rims to the proprietary KMX hubs. It brakes much more straight now since hard braking kept destroying spokes on the stock KMX rims resulting in me having to make frequent adjustments.

The wheel discs will go back on the rims after I have them checked out and adjusted by the bike shop next week.
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Old 03-23-2018, 01:51 PM   #63 (permalink)
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I got a consultation with Prof. Chet Kyle regarding my proposed velomobiles, and just about the first thing he said was to avoid even longitudinal ridges. Even if they are intended to align with the streamlines, those are always being upset.
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Old 03-23-2018, 02:16 PM   #64 (permalink)
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Quote:
Originally Posted by Bicycle Bob View Post
I got a consultation with Prof. Chet Kyle regarding my proposed velomobiles, and just about the first thing he said was to avoid even longitudinal ridges. Even if they are intended to align with the streamlines, those are always being upset.
I've read this as well. I find it's really hard to avoid ridges when working with coroplast. My compromise was to have several facets on mine, but it definitely has ridges.



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Old 03-23-2018, 02:29 PM   #65 (permalink)
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I was going to suggest wind-splits for the tail lights, but I defer to Bicycle Bob.

Stand them off from the body on pedestals and they're further apart.

For the faceting:


This is an octahedral based asymmetrical sphere with a frequency of six. If it had a frequency of one it would have one points on the top, front, back and sides. A frequency of 2-3 would give a reasonable compromise at your scale between flatness and edge [seaming] length. It can be created from a peel pattern on a large sheet.

The geometry makes picking edge lengths trivial.
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Old 03-23-2018, 02:44 PM   #66 (permalink)
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Coroplast can take a gentle bend along the grain, or be slit on the inside for a tight curve the other way. Would folks like to see a re-print of an article on advanced techniques here?
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Old 03-23-2018, 04:16 PM   #67 (permalink)
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What else would we need to know? Lots of edges. Break it up into hexagons and a single slit forms a shallow cone. With the geometry suggested the sharp angles are on the sharp ends and the flat angles are around the middle. I need to do a 2v version.


I mentioned peel patterns. http://www.tamasoft.co.jp/pepakura-e...nfo/index.html for arbitrary shapes.
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Old 03-23-2018, 04:26 PM   #68 (permalink)
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Quote:
Originally Posted by Bicycle Bob View Post
I got a consultation with Prof. Chet Kyle regarding my proposed velomobiles, and just about the first thing he said was to avoid even longitudinal ridges. Even if they are intended to align with the streamlines, those are always being upset.
I was actually aware of this but decided that my first prototype should emphasize ease of construction over drag reduction. I don't imagine its drag is comparable to commercial velomobiles, but it still provided a more than minor improvement in cruising speed over the naked trike.

I have plans for the next iteration of the design now that I know what dimensions it needs to conform to in order to fit my measurements and function the way I intend for it to(must be able to go over potholes, speedbumps, rough roads, ect without damage).

I don't have a CAD software to use at moment, either. If I installed WinE on my Linux machine I may be able to use Pepakura.

Quote:
Originally Posted by Bicycle Bob View Post
Coroplast can take a gentle bend along the grain, or be slit on the inside for a tight curve the other way. Would folks like to see a re-print of an article on advanced techniques here?
Was this it?

https://microship.com/bob-stuart/
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Old 03-23-2018, 04:33 PM   #69 (permalink)
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At the bottom of a very long page at https://microship.com/bob-stuart/ there are details on combining coroplast with a bit of fiberglass, and on laminating it for serious structural details. We don't need aluminum frames with it. The best tip, though, is to use 3M #190 tape on the seams. It goes on like electrical tape, but then it stays put.
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Old 03-23-2018, 04:49 PM   #70 (permalink)
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None of the hardware stores in my area had the #190 tape.

I used an over-built carbon steel frame so that at a later date I could add an electric drive system that makes 100+ lb-ft of torque in it. It's going to require a stout set of torque arms at the rear of the frame and dropouts.

When I move back to St. Louis in April, I plan to get started on the next body. Its shape will look a lot more like that of the LeMans velomobile. If I put in a rack and pinion steering system, I could possibly get frontal area in the 0.4-.5 m^2 range because I will no longer need to make room for the steering bars. A butterfly steering wheel with trigger shifters would work nicely in this machine if I put in a rack and pinion. I could keep the right brake lever for the front wheels and the left one for regen on the electric hub motor that will be going in the rear.

Right now it's about 0.65 m^2, and will be reduced to 0.6 m^2 if I turn the 4-sided front cross section into a 6-sided one.

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