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Old 12-02-2017, 01:09 PM   #51 (permalink)
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open wheel design

Years ago,at the International Human-Powered Vehicle Speed Trials,at Battle Mountain,Georgi,who'd designed the VARNA Diablo,fastest bike,told us that the 1/4-inch gap between the wheels and wheel fairings was responsible for half the drag of the bike; which has around Cd 0.11.
I' don't have much data on exposed-wheel rigs,so I'm not much help to you.

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Last edited by aerohead; 12-02-2017 at 01:10 PM.. Reason: clean up text
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Old 12-05-2017, 10:10 PM   #52 (permalink)
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I'm still working on the front and will need to have that fully installed before it is rid-able again. Maybe this weekend... It's getting there piece by piece... Testing will determine how much it needs to be redesigned. It's designed to allow cutting out of pieces to increase the number of sides, allowing me to turn the current square-shaped cross section into one with 6-sides or even 8-sides with better streamlining as the goal in terms of both drag and frontal area reduction, but this design will serve as a rudimentary shell to grant some drag reduction over nothing as it is initially.

When I get it to a shape that I am satisfied with, I could make a plug and mold off of it. It's designed to fit a KMX with installed suspension and the seat as far forward and almost as leaned back as possible, with access to the entire chainline/ider/rear wheel/gears/other maintenance items possible without the need to remove the body.

I might be able to make modular body kits to sell, but before I do that, I need to get the aerodynamics right, and before I do that, I need to get my prototype working and figure out what needs to be done to it to make it accommodate a larger size range of riders than just myself.

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Originally Posted by aerohead View Post
Years ago,at the International Human-Powered Vehicle Speed Trials,at Battle Mountain,Georgi,who'd designed the VARNA Diablo,fastest bike,told us that the 1/4-inch gap between the wheels and wheel fairings was responsible for half the drag of the bike; which has around Cd 0.11.
That doesn't surprise me at all. Wheel drag is one of the more significant sources of drag that cannot be fully addressed without somehow losing the wheels.

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I' don't have much data on exposed-wheel rigs,so I'm not much help to you.
I haven't come across much with regard to this. But there do exist examples of open-wheeled vehicles with Cd in the 0.2 range. It is not uncommon for open-wheeled designs to have Cd in the 0.8-1.0 range either... so getting to the 0.2-0.3 range is probably not easy.
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Old 01-12-2018, 10:31 PM   #53 (permalink)
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Here's some pics I took today attached to this post.

I still have a lot of work to do, but I've had a lot of fun riding it around like this.
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Old 01-13-2018, 02:53 AM   #54 (permalink)
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Have you weighed it?

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...and figure out what needs to be done to it to make it accommodate a larger size range of riders than just myself.
I don't think the open wheels are that much of a problem, mostly interference drag with the body sides. Half the time one or the other will be downwind. I do think the open cockpit is a bigger problem, and you want to accommodate your 90-percentile population.

What about something like a kayak spray skirt
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Old 01-13-2018, 07:38 AM   #55 (permalink)
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I haven't had a chance to weigh it yet with the shell, but I cannot tell a difference when picking it up and rotating it to fit through my doorway or when pedaling. The whole shell is easily less than 10 lbs.

The shell is way more than enough to accommodate my 140-ish lb frame that is just under 6 feet, but I need to make any successive iteration leave enough room to move the boom for taller riders while allowing shorter riders to see over the front while allowing adequare knee and toe clearance. Not an easy task.

The open cockpit is being remedied as we speak. I am in the process of building the middle piece to cut drag further. It will be set up once I finish the trunk area(which is still held together at the hinged trunk lid with gorilla tape since the rear bulkheads, rear wheel guard with removable panels, and lid rest, which all will be load-bearing, aren't yet installed). I will be using a polyethylene foam pool noodle around the head cutout on the midsection piece to keep it from cutting me up during the event of a wreck.

The center at the front where all of the black gorilla tape is, is an air intake with a vent. It focuses air toward my neck area and currently works very well. It was designed to speed the air up by concentrating it into a smaller area. I will be adding NACA ducts at the sides in the future as well for armpit cooling.

Other plans:

-spandex boots for where the front suspension sticks out
-slide-on rear wheel skirt to keep the airflow away from the wheel and rear derailleur
-rollbar/turtledeck behind the head rest
-slide-on windshield and roof for the removable mid-section currently in progress
-mirror mounts to go on the front sides integrated into the PVC pipe composing the front bulkhead(I don't want them on the midsection piece due to vibration and they must go on the sides to make clearance for my doorway. I realize this will add drag, but the mirrors are next to useless where they are currently at on the steering bars)

After all of that is done, I will turn the front cross section from a 4-sided shape to a 6-sided shape with the front cross section beveled at the top with 45 degree angles. The cuts will be made starting in the rear at the top of the tail, maintaining the same ground height in a straight all the way towards the front, where the exact same distance will be cut out when looking at it from a top cross section perspective.

This thing is going to look good when it's finished. Sort of like one of the lakester hot rods from the late 1940s. Once the shell is finished, I can work on some lights and signals, and then get the shell vinyl wrapped.

I may also need to modify the front to increase the ground clearance because there has been scrubbing on some of the more bumpy roads where I am at. Ground clearance is currently 4.5" at the lowest point.

After all of that is done to my liking, THEN comes the electric conversion. I'm going to put like 4 kW in it to start off, and later bump that up to 10 kW or so with modification of the motor. I plan to do lots of donuts, hooning, stop light drag racing, hooliganism, and other random acts of jackassery, with what will legally(at least in TX and about 6 other states) be an electric "bicycle" that legally requires no title, tags, registration, insurance, or license. Long-term goal is 0-30 mph in under 2.5 seconds and a top speed of 50+ mph. It will probably be the most efficient vehicle on the road in a 200 mile radius.

Then I will build a second one, probably a CFRP monocoque, with better aero, full suspension, 15+ kW Lynch motor, and sub 5-second 0-60 mph/100+ mph capability still set up as a sub 100-lb pedelec to maintain its status as a legal "bicycle" in TX and still able to be operated on purely human power faster than a normal bicycle with the motor turned off. I need to learn vacuum molding first though and get some CAD software that can run a stress analysis on it. I designed this first shell without CAD. Basically, think to yourself "what kind of electric velomobile would Hoonigans build?" and you might have an idea of what I'm trying to do... (I don't work for or have never been associated with Hoonigans, but they do awesome and inspiring work none the less, with committing random acts of jackassery in mind for everything they build)

Last edited by The Toecutter; 01-13-2018 at 07:48 AM..
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Old 01-13-2018, 12:10 PM   #56 (permalink)
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Quote:
...donuts, hooning, stop light drag racing, hooliganism, and other random acts of jackassery...
Those bicycle-width hubs may not stay in the center of the rim when you're driving sideways.
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Old 01-16-2018, 07:26 PM   #57 (permalink)
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Before I dare try it, I will be lacing some moped rims to it.

I came across the following piece of work though today:

Torus Prototype - Eternal Cycle Works

One can learn a lot studying these builds on that site.
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Old 01-17-2018, 03:42 AM   #58 (permalink)
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It must be nice having that big a garage.
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Old 01-17-2018, 09:04 PM   #59 (permalink)
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Yeah. I built(and am still building) mine in the kitchen of a duplex.
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Old 01-19-2018, 11:34 AM   #60 (permalink)
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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.

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