Aerodynamic expectations

First – let’s set the stage with an unscientific example “me”. I prefer to use the “comfort zone” as a honest measurement of speed the rider can hold comfortably all day. I have found this to be a more than satisfactory method of performance evaluation. Why ? A rider can be a having a soft day once in awhile and still ride with in a comfort zone there fore adding sufficient data to baseline results. If the rider was racing on a off day – his bench mark would be significantly off because of his motor – not the machine.

Why is the comfort zone more reliable? – The rider is on the bike with more regularity compared to occasional race meets. The seat of the pants performance with Heart Monitor is 2nd best only to the more dead on accuracy of a Power Meter. But lets get real – regular riding returns plenty of feedback under more consistent weather conditions. For instance the figures below is a result of long term familiarization of the many bike platforms noted. Anyone that rides regularly knows what their expected average speed is under normal conditions on what ever bike they are riding. One doesn’t have to pull out a slide rule to know his own performance level in given terrain “if“ they are in their comfort zone.

It is interesting to see the average speeds move up the mph scale significantly when aerodynamics is applied.

MTB bike – – 14 mph

Upright Cannondale bike – – 15 mph

Un-faired Tour Easy “TE” – – 16 mph

Bacchetta Corsa – – 17 mph

Front faired TE – – 18 mph

Body Socked TE – – 20 mph

Body Socked Gold Rush – – 21 mph (stiffer BB)

Body Socked ti-Rush – – The ti- Rush responds quicker than the GRR. With it’s livelier performance, it is easier to hold a cruising speed @ 22 mph

Rotator w/aero package – – 19 mph

ZOX clone FWD lowracer – – 18 mph

ZOX inside Varna Fairing – – 35 mph

Zephyr lowracer – – 19 mph

Zephyr inside Varna fairing – – 38 mph

Angletech Quadraped trike – – 15 mph (sits high)

Terra Trike Tour – – 16 mph (lowracer height)

Cat Trike ROAD – – 17 mph results later in season

ICE Sprint X 26″ – – 18 mph 

Milan SL – – Known expectations is it will cruise an estimated (26/28 (mph) with canopy open and 30/32 mph with canopy closed. Mph estimate based upon observation and talking with the Euro riders who ride both upright bikes as well as their Velomobiles while working support for Roll Over America “ROAM”.

Note: – – I have changed my mind – I will not be using the Terra Trike as a chassis for a Varna shell Velomobile build. I will instead build it as a sport trike configured somewhere between a ICE Vortex/CAT Expedition. Nine days on ROAM gave me perspective of velomobile design. I made the decision to order a Milan SL. Why? I no longer want to endure the longer custom build process. I would much rather prefer the accelerated Milan build and get on enjoying it quicker.

Once again – keep in mind – these examples are “Comfort Zone” speeds for me – not racing speeds.

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Streamliners vs Velomobiles

Single track Streamliners “Liners” are usually a fantasy for most recumbent riders. Why? – these bikes are all hand crafted custom builds for a specific rider with purpose. With exception of the very few – most “liners” are used for racing only. Example – the current world record for Human Power is held by Sam Whittingham @ 82.3 mph. The reason one does not see these liner’s out on the open road for daily use is that the hard sided streamliner shell is unforgiving in cross wind turbulence of any kind. The vehicle becomes terrifying to handle until the handling skills have been learned. Think of a sail boat “with out” a keel – got the picture “wink”. This is the reason most liners are used in low wind situations or for the track. I have found there is a whole lot of distraction just keeping the single track Liner upright let alone navigating it through traffic. On the other hand three-wheeled Velomobiles “Velo’s” are safer user-friendly streamlined platforms that are at home on the open road. They use a recumbent trike chassis configuration that adds lateral stability for cross winds and climbing. However, beware – there still can be serious lateral cross wind push as velo speeds get faster.  Logically, the trike configuration for a streamliner shape is a desirable safer vehicle to use over the single track Streamliner.  The best part of this comparison is Velo’s are manufactured for sale to JonQ public – Streamliners are not. Comparatively – technology has improved the Velomobile into a more user-friendly streamliner for open road use. It has been discovered that most Velo’s have an impressive performance window regardless of the third wheel resistance. This link talks of how a single track Streamliner racer improved his time with a third wheel.  The challenge most riders have – is to mentally over come the vehicle weight and the perceived third wheel resistance factor vs the aerodynamic benefits. One needs to carefully analyze its intended use for the trade off to be substantial. Unfortunately many riders never get past this hurdle. My explanation to this dilemma is recognizing the three fundamental factors of recumbent bicycling.

There are three categories of riding a bike.

1st – the “uphill” – – A four man team in 2009 RAAM illustrated a High Racer recumbent can be as strong at climbing as an upright bike.  On the other hand, the heavier Velo can attack roller hills with massive amounts of momentum that gives amazing results – but – when the momentum wears off and uphill grind starts, at least a Velo won’t wobble and fall over at slow climb speeds. It was pointed out to me by a velo driver that he can climb easier in his velo. Don’t confuse the ease of climbing with the speed of climbing. He explained that he can be in a slow easy spin and arrive at the top without the pain of trying to keep a upright bike stable when climbing slow. So, there is another dynamic for which one has to think about. Unless time is of an essence in racing – who cares if you arrive a couple of minutes later at the top with a grin on your face.

2nd – “level ground” – most “not all” recumbents have an advantage of aerodynamics.

3rd – the “down hill” – is where most recumbents become cruise missiles.

So – out of these three categories – the average recumbent platform dominates “two” out of the three.

Healthy competition: There will always be the “upright vs recumbent” challenge. Streamlining just puts a whole new spin into the scenario.  Annually non-faired recumbent race teams compete in Race Across America “RAAM”. The RANS recumbent team actually gained time over the leading upright team in the Rocky Mountain climbing stages in 2009.  My feeling are the “recumbents can’t climb” argument will eventually fall to the way side of the uninformed over time. Every year it has been observed that a modest number of upright racers are going recumbent for Ultra endurance events.

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Tail Frame – Tail box

Purpose’s of Tail Frames/Tail Box is for assisting the displaced air mass back to itself reducing power robbing turbulence.

Notice the riders shoulder snug inside the composite Tail Box

If possible, the tail box should be positioned close to the rear/outside portion of the riders shoulders for best results.

Aero Wing tail frame forming a “tail box” on a Gold Rush

Many riders do not prefer the inconvenience of getting into a Body Socked bike – so – the tail box only concept is a great option.

Aero Wing tail frames are commonly used for Body Sock applications because of enhanced aero design and ventilation.

The same Aero Wing tail frame is used for Semi Streamlining this Gold Rush.  A stretchy fabric “Lycra/Spandex” is used to cover the rider for aerodynamic streamlining. The tail frame simply finishes what the front fairing started. The shape and size of the Tail frame/box is important so to minimize turbulent drag.

Riders that have a “need for speed” usually end up using a lowracer inside a semi faired streamliner shape.

Note: – Keep in mind anytime cloth is used for streamlining, it is used for compromises of comfort and convenience. Smooth composite surfaces are known to be the fastest.

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Lonnie Morse – Aero Wing components

Aero Wing components take the aerodynamics of recumbent riding to the next level of performance. Though body position is enough for many riders – more and more riders are taking the next step with the aid of fairings – front, rear or both. A fairing is the most influential “bang for the buck” component a rider can install on any human-powered vehicle. Yes – fairings are expensive but so are carbon fiber disc wheels that cost more but give back less in performance comparitively.

We cyclist have been cultured into the “graming game” way of thinking. We believe removing weight seems to be the only way for improvement in quest of performance. That may be true for the up-right bike community. The United Cycling Union unfortunately boxed the upright rider into specific dimensions years ago.

They also banned the recumbent bicycle in 1934 because of  winning most races. So – why does a recumbent have the aerodynamic edge? Notice the recumbent rider body is more horizonal compared to the upright rider. Remember – the smaller the hole that is punched out of the atmosphere – lesser the drag of aerodynamic friction.

Picture at the top and on right says it all.

The flip side is the Recumbent bike “bent” has no restrictions to have to abide by regarding continuous on going design improvements.  Yes, bents are classed by category but by aero dynamics, not bike chassis construction.

Note: – I’m not saying weight isn’t an important factor for any human-powered vehicle – however, many times the added weight of a fairing generally returns dividends big-time to off set the added weight.

  • Notice how cars are changing shape, especially the Hybrid cars.
  • Could a bird fly efficiently if it wasn’t shaped the way it is?
  • Is the human body considered aerodynamic?
  • Why are modern semi trucks faired?

While you are pondering these four questions – think about the “aero efficiency” of the questions.  Yes – Engineers have proven they can make a brick fly – only at a huge loss of efficiency.  Put a fairing on that brick – the coefficient drag aero “Cda” changes dramatically IE. modern faired trucks.

The intent of this blog is to help with the understanding of beneficial  aero dynamics when used with human-power vehicles. The standard upright bicycle has been noted as a platform of efficiency from scientist – however – the usually more aerodynamic recumbent bicycle is rapidly becoming the fastest growing category for the bicycle industry. Examples like touring, comfort, commuting, and Human Powered World Speed Record Racing hold an edge compared to the antiquated up-right bike.  It is unfortunate that most civic bike infrastructures are designed for “just” the up-right bike.

A new category is taking hold – I am speaking of the recumbent sport trike and faired velomobile.  Why? Interviews have discovered that it is the “high fun factor” these vehicles provide that is cause for the sudden public interest. One has to acknowledge there is a great deal of practicality with the added “trike” stability.

The use of aerodynamics can suddenly change a docile trike into a speedy cruise missle called a Velomobile “Velo”.  This recent addition to the newest catagories of human-powered vehicles “HPV” is probably the most practicle utilitarian HPV to date.

I urge one to use practicality as a guide when determining expected aerodynamic benefits.  Don’t know? ? ? Then this Blog should provide quidelines to help with the process of making your Human Powered Vehicle as efficient as possible. We will not be getting techie here. The examples provided within will be understandable fundamentals for the layman. The reviewed users have already tested the concepts. Be assured, riders certainly would not endure the weight penalty of the aero components if there were not a significant pay back in performance.

Lastly – we are going to assume that every one is of equal physical fitness regarding claims in this Blog. In laymen terms – everybody has the same motor/wattage out put etc.  Yes – everybody is a Tour de’France rider – “yea rite” LOL.

It has been pointed out to me by an engineer/builder of a Bonneville Land Speed Racer that aero dynamics work at any speed – it is just not noticed at slow speeds.

Here is link for comparitive data of aerodynamics concerning human powered land vehicles. Well written so the layman can easily understand.

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Touring Streamlined

In May of 2005 there were Six Warriors who ventured across America riding Easy Racers recumbent bikes. All had front fairings and four of the six had body socks.  The amount of streamlining these heavy tour’ers had was each riders choice.  Even though we were not in a hurry, streamlining the bikes made for a free’er rolling more aero efficient bike on an already comfortable touring platform.

Heavy Touring streamlined doesn’t mean you have to go fast. It just means you can pedal easier with less resistance.

We had three months to stop and smell the roses along the way hence we called this a “Luxo Tour”. You can read about our tour on the crazyguyonabike blog.



Tacking in cross winds.

Many times the cross winds work in favor by giving surprising push caused from wind sail tacking. Notice the difference of me leaning into the wind where as the rider in front is not getting the push. When it happens, I smile to myself and enjoy the free ride.

I might point out another design benefit of the Aero Wing tail frame. Notice the rider in front is wearing the sock on his shoulders “no air circulation”  Whereas the Aero Wing tail frame design keeps the sock off my shoulders therefore allowing plenty of air circulation – much like driving your car with the windows down. The picture at the top of this page gives another view of the “no shoulder” touch design.

Notice the Kansas corn blowing near horizontal in the gusty 25-30 mph headwinds. Once a rider gets accustom to the buffering of the winds – it’s much like driving a light car – you get used to auto correction. However – when the wind becomes too strong to deal with – just tuck the sock up under the fairing. The fairing will still give an amazing aero advantage.

note: – We would pass a upright rider every morning between Hutchinson KS and Pueblo CO. He estimated we were going 1.5 mph faster than he was.

More streamlined touring recumbents “bents”

Terry on “Bent Tour 08”

Oregon Human Powered Vehichiles “OHPV”

I had noticed after returning from our “Six Warriors” Trans American tour, there were several friends that had shown interest in self-supported touring. I felt it would be a good idea to conduct a seminar to present the  – good – bad – and ugly of cycle touring. After all – our OHPV organization had a multitude of experience with in our ranks.  After talking with few fellow Trans American riders, we tapped our own resources to present a informative  seminar. The “Bent Tour08”  seminar – In order to really get a taste of Trans American long distance – a week-long tour was scheduled to ride across the Oregon coastal mountains  – down the Pacific Coast – back across the coastal mts. once again – across the Willamette Valley then up 3000 ft into the Cascade mountains, then home to Portland OR self-supported. This would be a week-long tour for most, a few days  more for others from Washington state, as all riders rode their bikes from home. No one used a car for the whole tour.  However –  there was a catch – everyone would have to do a self-contained over nighter “before” being accepted on this tour. This was to give the rider time and exposure with their equipment choice/weight, physical fitness, and bike condition. Most riders chose to tour to the Recumbent Retreat to qualify as it cross’es the coastal mountain range of Oregon for a real-time experience of what a heavy tourer is all about. Several veteran riders were along also for the enjoyable tour. The Extra Bonus was the Recumbent Retreat is always a fun event highlight for the year.

 The Seminar- – Bent Tour 08

The result of the “Bent Tour 08” has given the newbie cycle tourist the confidence to follow their dreams of  long distance touring.

This is a special couple –

Kirke and Kathi travel several weeks each year on their streamlined Fold Rushes.    Kirke happens to be a 10,000 mile annual rider.

 Dave “Slug” Vangundy is a Bent Tour 08 graduate – he has done the Southern Tier from San Diego to St. Augustine FL. In 2011 he continued his trip starting St Augustine connecting to the “Nazz Trace” to St. Louis where he got weathered out by Tornadoes. His plans are to complete his tour from St Louis to connect on to the KATY trail heading west to parts yet to be decided in the future.

TransAmerica rider Dave Vangundy on his Streamlined Gold Rush. Read his Southern tier journey on crazyguyonabike. More to come !

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