Aerodynamics of world record HPV

That is a neet looking frame, bzh. What is the actual width? Also what is the camber angle of those front wheels. To have comfortable steering and braking you should have centerpoint steering or close to it. It looks intuitively like too much negative camber. Just mho.
otherDoc
 
SOO if these things are doing those speeds with 400 watts or less, HOW FAST WOULD IT GO WITH A BIG FAT CL MOTOR ON THE BACK!! Or better yet, a big R/C motor with only slight gearing! I bet you could get well over 100 or faster! Somebody needs to buy one of these guys old bikes and build the fastest E bike in the world!
 
docnjoj said:
LI-ghtcycle wrote:
"I like the concept of the Drymer, but not the looks. WOW!! 60 kilos?! (132 lbs?!) and that's before adding any electrics!"


I believe that weight is with electrics since the Drymer comes with them installed. It is still heavy but not unreasonable.
otherDoc
Click to expand...

Oh, oops! My mistake, I thought it looked beefy for what I thought was a pedal only machine! :mrgreen:
 
Yup, there is too much camber, and that produce high rolling resistance that I need to avoid!
i think that wheels outside will represent at least 50% of aero drag?
 
I don't know the exact percent of Cd that the wheels make but Steintrikes makes a Velo for my trike and they use separate wheel full fenders. It covers the wheel but leaves it outboard of the body. They think it makes a difference since they even tout those skinny European 16" (349mm) wheels for "Aero" purposes. I think they just got them cheep1 I replaced mine when the spokes broke!

http://www.steintrikes.com/index.php

Their Velo body is called the "Thunderstorm"
otherDoc
 
bzhwindtalker said:
Yup, there is too much camber, and that produce high rolling resistance that I need to avoid!
i think that wheels outside will represent at least 50% of aero drag?
Click to expand...

Wheel fairings will certainly help a lot (drag is proportional to velocity cubed, and the top of the wheel is moving twice as fast as the body, so 8 times the drag of the same geometry not spinning :shock:). Mind you, even with fairings, the multi-airfoil style configuration (as seen in a plan view cross-section) produced by external wheels will do very, very bad things to your drag profile as a result of aerodynamic interactions between them (I'll dig up some 2-D simulations I did) - there's a reason biplanes and triplanes died out in the 1930's, and that reason was drag - as soon as strong enough monoplane wings were demonstrated, planes ditched the multi-airfol approach and became hugely faster as a result...

Nice trike, by the way! Could use some light bracing in a couple of additional places to stiffen up the frame (will send pics), but looks solid.
 
Don't know if it's been mentioned but Cedric Lynch's streamliner is closer to something that you can actually imagine driving on the highway (and he does, I'e seen it!)

http://www.bikeweb.com/image/tid/57

I think it uses quite a few MTB components, including tyres.
 
If you guys really want to go fast, stop thinking in terms of power and think in terms of efficiency.

Those Varna speedbikes adhere to the two most basic aerodynamic principles: Smooth = fast and small = fast. They lower frontal aero to the bare minimum needed to enclose the pilot and smooth out even the smallest details. For instance, both Georgi and Sam both say that the wheel openings (which are the only openings) account for a significant amount of drag. And that is why they make the openings smaller than required when popping them out of the mold, and use sandpaper to remove just enough to get the pumped tire through the slot. It's a painstaking process, but it probably gives them another 5 mph. There are other little details, such as the tape they use to seal the top half to the tub just before the rider makes his run. That tape is a specific type of electrical tape (that they won't actually reveal) that must be put on in a single straight piece, starting at the back, going down one side to the front and back down the other side to the back. One mistake during the taping and Georgi starts over again.

Here's the thing. Sam has upped his record to 82.8 mph... but can barely fit inside the new Tempest. Barbara has run 75 mph in the same bike and Georgi believes he can build her a bike small enough to go 80 mph. Barbara is strong, but I doubt she has 75% of Sam's available peak power.

Power is less important than efficiency.

:)ensen.

PS: I haven't been in a Varna since 1992 when I road tested the Baby Trike for Georgi. And yet, nothing I've seen in the world of motorized vehicles even comes close to the aerodynamics of that 18 year old machine.
 
Purple guy,
Who really wants to ride around in a glorified lima bean, which are inherently very dangerous. Once you add a motor usefulness trumps absolute aerodynamics unless you're trying to make something to run at Bonneville. You do have a point though. With a quite aerodynamic design quite low power will be required for significant speeds.
John
 
Who said you had to ride a lima bean. Below is a Versatron Vector trike. First intro'ed in 1979, this is probably the 1982 model. Typically about 60 MPH with an elite non-pro cyclist at the helm.

I've come to ES forums late because I've been out of the HPV game since '96. Most of the advanced stuff here on these forums have nearly perfect electric and electronic systems. Yet no advances in the aerodynamic department even though aircraft have been slowly improving. The Eco-modders have done some small amount of work, but so far, at speeds less than 100 mph, nothing I've seen is as refined aerodynamically as what the HPV guys have been doing for 30 years. Even the X-Prize stuff hasn't been that impressive, but I think they're really constrained by the rule set. The solar car people had some great advances for a while, but stagnated after the GM Sunraycer set the standard form that has been copied and copied (designed by Aerovironment, the corporate project of Paul MacCready, another HPV guy). If I had to lay blame, I'd say that cheap energy has made the power systems the easy fix for speed. Now that we have oil uncontrollably diluting the ocean and coal choking our skies, it's not only time, but a necessity to prioritize efficiency over power.

:)ensen.

As always, kudos to Jeff Wills for archiving the little information available on the Vector. His fan page on it is here: http://home.comcast.net/~jeff_wills/vector/vector.htm

apvector.jpg
 
Purplepeopleman! Those build films were truly inspirational! Very fine engineering. That tilt trike seems quite effective. Do you need a lockout or does the tire friction hold it in place while stopped? Really fine composite work on the tadpole too!
otherDoc
 
Thanks. Both my tilt trikes will fall over without a tilt lock. AFAICT, a tilter that self-rights (not including active tilt systems) cannot corner as well as a tilter that does not. IOW, for it to corner like a bike, it must also have the same balance as one.

I agree that the Kingsbury trike is brilliant, but well within reach. It's typical of HPV designers actually. That's not to say that there is more genius among HPV'ers, but rather, having the overriding constraint of very low available power forces creative solutions that incorporate many different disciplines and industries.

The other trike I've been search for pics of is the Allegro series from the '80s by Don Witte. It's also a 60mph HPV and was more like the Vector but with a flat bottom. Along the same vein, here's two photos of a new trike in the works over at WISIL that is based on a the Varna Baby Torso from 1992, which itself is being updated as a window-less camera trike.

:)ensen.

CIMG0651.jpg


CIMG0655.jpg


georgiev+copper+trike.JPG
 
Purple:

I couldn't agree more. Although the #1 problem IMO, with such efficient vehicles is safety, due to other dangerous vehicles on the road. We live in a world where it's not safe to be efficient. If you didn't have to share the road with drivers texting while driving their 3000lb vehicles 2 feet alongside you, these streamliners would make a lot more sense.

I wish I could invest in a streamliner, but being < 3 feet tall and shaped like a missle means I won't catch those 'distracted eyes' of all these cars out there.


I've come to the conclusion that the best combination of efficiency and safety is a bike/rider setup such as a UCI legal TT bike. Almost as good as a non-faired low racer recumbent, but with better visability and height to be seen in traffic. (you can also sit up easily when going slow in traffic). The problem is - comfort suffers, and you must wear spandex for the position to be effective.

I'd really like to see considerably more aerodynamic, faired motorcycles. The average motorcycle is a model of horrid aerodynamics, and IMO you're better off in an economy car for safety, capacity, weather protection, at the expense of 30% less mpg. I recently read about that 214mpg streamlined Honda...
 
veloman said:
I wish I could invest in a streamliner, but being < 3 feet tall and shaped like a missle means I won't catch those 'distracted eyes' of all these cars out there...

I'd really like to see considerably more aerodynamic, faired motorcycles.
Click to expand...

A good ebike compromise might be a faired "cruzbike": up higher and reduced frontal (wheels more exposed, but somethings gotta give).

For example of a better faired moto, google "vetter streamliner".
 
The height difference between the very common velomobiles, like the Mango and a high speed HPV is typically between 6" to 12". It's close enough that it would be reasonable that they should act and be reacted to the same by other road users. Moreover, just about all the velo pilots and other low-racer recumbent riders attest that they have no problems with people seeing them, provided they operate in a predictable "vehicular" manner.

Now, while none of the human powered options are safer in a collision than the typical metal cage automobile, I'm quite sure that people's fears re: low are as baseless as they are for a Lotus Elise. Drivers see the lines on the road, which have zero height. They manage to avoid dogs, which are not only small, but unpredictable compared to a well operated recumbent. The fact is that being low might only be an issue while shielded from view... a situation encountered nearly as often riding in the Civic as riding my tilting low-racer. In the many thousands of km's I've ridden (and driven), there is only situation where being low could be dangerous - when you reach an intersection at the same time as a larger vehicle in the next lane and you are shielded from the view of any cross traffic. If you have the right of way, you inch your nose slowly until you can see the cross traffic yourself, and if you can't do that while remaining out of the path of cross traffic the prudent move is to wait until the taller vehicle has cleared the intersection. And for some reason, it's strange for people to think that this is what they should do with a recumbent even though that is exactly what all the licensed drivers would do if they were driving a low-slung sports car.

Sadly, people typically see low and equate invisible just because they can't see them from their current vantage point instead of realizing that it is more important for the low vehicle to be visible to the traffic immediately surrounding it. It's a small difference in how HPV'ers see the world, but I think one that well illustrates their "no spoon" thinking and how this might result in HPVs being such a revelation to others.

The only reason a speedbike like the Varna Tempest is impractical for road use has more to do with it having two wheels and a design that requires crew members to seal the canopy only after the rider has shoehorned themselves in. I hope what I've shown is that while you cannot achieve 80 mph with a small wattage motor, it should be possible to get 60 mph while retaining the practicality required for everyday usage.

:)ensen.
 
Now we're getting somewhere with good aerodynamics on this thread :D. The Allegro looks brilliant, and while 'Bubble and squeak' has a few sharp edges, it's not too bad, and the build is an example of monocoque done right.

Unfortunately neither would be raceable here in Australia - cameras are not yet an accepted means of navigation (a mandated viewing angle and physical rear-view mirrors are required), and the competition regs call for rollbars and anti-intrusion bars by the dozen - we even need 'top' anti-intrusion bars, as it was observed by a concerned parent that vehicles commonly fell sideways, leaving the possibility of getting T-boned in the cockpit... being events that are trying to encourage primary school kids to get interested in the technical and sporting sides of HPV racing (on the same track as fast university and other 'open' teams), it's fair enough, of course.

My solution to the visibility problem will be to paint the vehicle in an eye-searing flouro colour scheme - I'm thinking yellow with some 'tribal' patterns (ala need for speed) in flouro orange, blue and green. With electric assist allowing me to occupy a lane at traffic speeds, it should be ridiculously visible compared to your average black Ferrari. The law here is that you must ride 'as close to the left as safe' or something of similar wording (which unfortunately doesn't allow 1000W at the rear wheel :wink: ), and trying to ride a velo in a bike lane or occupying the left just-over-half of a car lane fits my definition of 'dangerous'. One of the interesting effects I've noticed riding roadies is that anything in a bike lane is invisible to most cagers most of the time, but anything in a 'car' lane has their attention - I think it's about where people habitually look more than anything, the brain is very good at setting it's self up to recognize a pattern and then apply it on auto-pilot (as on a drive home from work), and in non-biking countries like Australia, "something in a bike lane" simply doesn't fit the pattern.
 
I don't have any plans to make a velo for street use, but I have pondered some of the questions that have arisen over visibility in traffic.

I am open to odd ideas if they might serve a useful function. I've considered some type of "shark fin" above an electric-assist velo. Vetter has real world experience, and has said that the effect of side winds of fully faired 2-wheelers presents a serious consideration. If the outer edge of the fin is a fixed shape, and the body of the fin is made of several flaps that swing side-to-side, that might be a reasonable compromise between the safety of higher visibility, and low-weight/low-drag.

Like these signs that are intended to swing with the wind instead of being knocked over...

ss3.jpg
 
spinningmagnets said:
I am open to odd ideas if they might serve a useful function.
Click to expand...
...with most of the concerns expressed about recumbents being safety from other traffic, my experience dragging stuff other traffic can't see in front of them (as race catamarans with really tall masts) was to add a "rag"/warning flag at the trailing end of the mast (per the law) `cept it wasn't a "flag" at all but instead a 25ft. thin plastic tube - technically the drogues made for Peter Powell Sky-Stunter kites as a kite "tail"...

These long drogues flew in the air behind the trailer in a gentle snaking motion left/right and were a source of amusement for traffic coming up behind us...
guess all I'm sayin' is, if I were riding recumbent I would be flying a flag *behind* me for attention rather than *above* me... OK, probably both...

Will take this opportunity to state the obvious where efficiency rules... the simpliest trade-off to achieve low Wh/km is to slow down...
Tks
loCk
 
purplepeopledesign said:
If it flutters, it's turbulent. If it's turbulent, it adds drag.
:)ensen.
Click to expand...
Understand... it's just that in practical terms safety may require efficiency trade-offs.
loCk
 
Lock said:
purplepeopledesign said:
If it flutters, it's turbulent. If it's turbulent, it adds drag.
:)ensen.
Click to expand...
Understand... it's just that in practical terms safety may require efficiency trade-offs.
loCk
Click to expand...

I like the idea of a rigid or semi-rigid F.S.O. (Flag Shaped Object) - this could be made quite aerodynamic (like a little reverse-delta symmetric airfoil). Likewise, a streamer wouldn't be too bad if it had more weight and spring than flop... and the thinner the better... anyone up for doing some streamer drag testing?

If someone were to hang a stick out a window with a spring balance to measure force and a computer fan with a tacho attached to measure air speed, quantifying the drag of a few alternatives wouldn't be too hard. Don't currently have a (workable) car, but I'm doing one up - I might volunteer to test some community suggestions for low-drag flags myself... in any case, give me some ideas and I might get to trying 'em in a month or so, or someone else might step up to the plate. It would be a useful thing for both the safety concious and people nervous about riding velomobiles (and possibly some who are both :wink:)
 
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