Recumbent Bicycle Design by Charles Meredith Brown - January 2016
Putting It All Together "If I have seen farther than others, it is because I have copied off the test papers of giants."
   
Sections:
The bikes we'll be comparing here
Dimensions of These Bikes
Ride Roughness
Hill Climbing Ability
Rolling Resistance
Cornering Ability
Air Drag Again
Final Results


This article is an attempt to put together what we've discussed in my previous articles on Recumbents.com, so hopefully you will have read them first. They are: Bicycle frame design, Steering and ride, and Air Drag Formula

The goal is to use all this as a tool to help predict how a vehicle will behave.  Everyone who gets into bicycle design soon learns that developing a well-balanced vehicle is far more complicated than they first thought.   We are literally re-inventing the bicycle.  Recumbent design sometimes seems to be based more on intuition and guesswork than on engineering and science.  Mechanical creations that work so intimately with us need to spring from the heart and soul first, but knowledge is also a critical component, and its proper use can prevent many missteps.

The math included herein is only a rough guide for comparing different designs.  Don't be saying, "Charlie says Bicycle X will go 2.7 percent faster than...".  If this were a legal document, you'd be wading through scads of fine print and disclaimers by now.  When we make a change and see what happens, we assume other things stay the same, which is often not the case.

Let me give you an example of how interrelated things can be.  Let's say you're building a lowracer with a monotube frame and rear wheel drive, which you will be using to race.  Since speed is a high priority, you want to know which design will be faster, one with a 700c rear wheel, or to use a 20" rear wheel.

Bigger wheels give lower rolling resistance.  A low racer typically has only about 1/3 of its weight on the rear wheel.  Assuming tires of equivalent quality, the larger wheel lowers the bike's overall rolling drag by 10%.

Ah, but there's something we missed here!  The bigger drive wheel puts 46% higher forces from pedaling loads on the frame  (See 'Frame Design').   All bicycle frames bend a bit when you press on the pedals, and lowracer frames, despite their aerodynamic prowess, are among the worst in this regard.  So if you have a very flexible frame, maybe it will be slower with the bigger back wheel.  Although, of course, you could compensate for this by installing larger chainrings and freewheel cogs to reduce forces on the frame...

I sometimes think that I learned about bicycles by making every mistake it is possible to make.  Surely there can be no more!  Then I come up with a new way to foul up.  Let me share some of my own experiences over the years to illustrate how many things can go wrong:

  • The only carbon fiber bike I've built so far was an amazingly light, stiff recumbent that I thought would just rocket up the hills.  Turns out the only thing that bike would let me do with hills was look at them.  What gives?  Much, much later I found the problem:  The back of the seat I pressed against was too flexible.  The problem had nothing to do with the frame at all.
  • One bike I built had horrid steering.  Now many things can cause this, which I was checking on one by one to no avail.  After considerable duress, the seat mounting turned out to be a little bit flexible side to side.  I made a new seat to frame mounting, and it steered beautifully.
  • Another bike was going unusually slow.  Turns out the bottoms of my shoes were shot, so I wasn't pressing the pedals so hard.  New shoes made me about 10% faster!

Any number of little things happen.  Numbers are great tools, but use them intelligently.

We're going to be comparing a number of different recumbents.  If you want, make diagrams of any recumbents you want to compare, and follow along with the math.  The bikes will be a variety of standard designs, trying to give an example of bicycles that are for sale on the market, and some 'what if' designs, where I'm curious what would happen if we made a few changes.

We will be standardizing some things on these bikes, in order to make them easier to compare.   For example, all have a total bike + rider weight of 90 kilograms (198 lb), and the riders are all 178 cm tall (5'10") (three cubits and a span).  All wheels are non-aero ones with 28 mm wide tires of equivalent quality, the rolling resistance goes up as the wheel diameter goes down.   Several have the same 'semi-aero' seating position, of a 35° seat back angle, and a bottom bracket (WE call it a front bracket)  25 cm higher than the seat.  This way you can get an idea what will happen when you put a rider in the same position on different bicycle configurations.   Almost all the bikes have narrow handlebars behind the knees.   Even the high racers have temporarily given up their beloved 'tweener handlebars in the quest to make our comparisons easier.

Having ridden a lot of bikes, along the way I will be adding my own opinions of the various designs.  These are just my opinions, I've met a lot of people with very different preferences.  In general, I prefer the long and low, but I think lowracers are too low for our oblivious motorists to see them (though they seem to have no trouble seeing curbs and lines painted on the road).  If you are new to recumbents, best to ride a few and get some idea what you like.

Several designs will look very similar to each other in diagram form.  On bikes, small changes make a noticeable difference!

The bikes we'll be comparing here:

A conventional, upright road bicycle will be making an appearance later on, for comparison purposes.  The rider on this bike wants to go fast, too, so they're hunkered down in a semi-crouch position, keeping hands on the drops to reduce air drag.

Traditional long wheelbase bikes, such as the Tour Easy and Rans Stratus probably have more air drag than any recumbent here, but they'll keep up with the upright race bike, in more comfort and safety than any upright bike can match. There are faster recumbents, but its hard to find one more enjoyable on long rides.
Future - like the LWB above, but with the seat lowered 10 cm (4"). It makes the frame structure a little more efficient, with slight benefits in aerodynamics and ride comfort. Needs a grease guard for the chain. Described further in “Bicycle Frame Design”.
Palomino - my attempt at designing a long and low bike. Something like the touring Velocar of long ago, Steve Delaire’s Rotator, Robert Riley’s Ground Hugger, etc. Described further in “Bicycle Frame Design”.
Raised long wheelbase bikes - the Rans Velocity Squared, the Easy Racers Tomahawk and Javelin had almost identical dimensions. I think they place the rider a little too high up but that’s just a personal opinion. I don’t think any are manufactured any more, but, Hey! (Us homebuilders can resurrect any design we please!
Moonlight - sort of a mid to long wheelbase design. One of the few here that combines a good ride with good cornering. Described further in “Bicycle Frame Design”.
Compact long wheelbase - Such as the BikeE and Easy Racers / Sun EZ-1. I think the design goals were to make it small and inexpensive. Later on I’ll be rating this bike’s cornering in last place, but that’s not so bad for this bike because they don’t go very fast. I think they’re more toy than bike.
Hígh racer with rider placed flat on back - hypothetical design, intended to be compared with the next one to see the differences. Laid back seats seem to be the way things are going these days. I have no idea how you’d get a foot on the ground at stops as I’ve sketched it.
 
700c wheel híghracer, straight frame - the current trend In highracers is to fit them with larger wheels, which are claimed to give a smoother ride. Would be true if other things were equal, but they’re not - they raise the rider 5 cm (2”), which counteracts this. They do give lower rolling resistance, and wheels/tires are easier to get.
650c wheel highracer, straight frame - this is to compare with the next bike below. The straight frame helps create a lighter, stiffer, better hill climber, while the curved frame makes for better aerodynamics and ride.
650c wheel highracer, curved frame - I personally don’t like highracers with big wheels, the rider position is higher than I like, the pedals are ‘way high, and there’s a lot of foot/front wheel interference. The last two make these bikes harder to get started from a stop, if there’s a graceful way of doing this uphill, I haven’t found it yet.
24” wheel híghracer - I like this design, these seem to be thr right size wheels for a highracer. I seem to have the minority opinion - bikes like this don’t sell well. Sigh. I guess the lesson here is don't let me tell you what to think.
20” wheels, straight frame - rather like a Rans Rocket. Included here because I thought it might be a good design for a commuting bike or a folding bike. Wider tires might be
a good idea to smooth out the ride.
20 inch curved frame - of the bikes I’ve built, the ones I’d rate as having the best steering ‘feel’ were all SWB’s with two equal size wheels. perhaps due to having more weight on the front wheel? Enjoyable to ride arid easy to store.
 
Typical short wheelbase - the ride is too harsh for me, might be okay with fatter tires.
Midracer - something like the Catbike Musashi. Like the above, but with attitude. The lower seat improves air drag and ride, but increases chain bend. If I ever get front suspension working as desired, this is the bike I’ll be putting it on.
Moving bottom bracket front wheel drive - sort of like the Cruzbike Vendetta. because you can fit a big front wheel, this is one SWB with the ride of a LWB. Fast too! It took me a long time to learn to ride them. Steering seems best to me with a fairly upright steering axis and
short-ish (5 cm or less) trail.
 
Lowracer - Is your pulse beating faster already? Real lowracers are even faster than the one described here, as designers go all out to reduce drag. I’m keeping the rider position the same as several bikes above for comparison purposes. I ride on public roads and am concerned about of these vehicles in this use.
Long wheelbase Iowracer - If you keep enough weight on the front wheel that the rear wheel still skids first, it occurs to me that a long wheelbase lowracer might be just a bit quicker. Fewer bends in the frame means more power gets to the back wheel, better ride, less energy lost to vibration, less rolling resistance.
Lowracer wíth ríder placed flat on back - Lowracer with the seat cranked way back, which seems to be the trend. Bikes like this usually suffer a power loss because the rider kas so little to press back against, I will assume you have solved this problem.
700c wheel MBB lowracer - to reduce rolling resistance, this is possible with the moving bottom bracket design and a rider with long legs. 5ean Costin built one of these many years
ago and was untouchable on it.
 
Flat on back, 700c lowracer - the bike for very courteous bike racers, who wish to save other riders the trouble of passing them. Very low drag - puts the ‘Veloce’ in ‘Velocípede’

 You will notice a few attempts at designing a faster lowracer.  Let's see what happens when you lay the rider down flatter, and use big wheels to reduce rolling resistance.  The last bike here is the same one shown in the section on measuring air drag.  In that diagram I drew in handlebars that placed the pilot's arms straight forwards.  I did this to give the rider something to hang onto to help keep the torso from sliding back with each pedal stroke; in this position they need all the aid they can get.  Also it starts to clear out a path ahead of the rider's face in case they want to see where they're going.  I have no idea whether this gives lower air drag than narrow handlebars behind the rider's knees or not. 

The version in this section has a little higher drag because it has non-aero wheels and heavier touring tires, the same as all the other bikes in this section to make things easier to compare.

Do you have some bikes you'd like to compare?  I think it would be great if you prepared some diagrams of the designs you're interested in, brought along a pocket calculator, preferably one with a square root key, and come along and join me in the math.  It's fun if you're into this sort of stuff.

Dimensions of These Bikes:

Author's favorites for street use marked with star  Rear wheel nominal & actual outside dia. (m)  Front wheel nominal & actual outside dia.  (m)  Percent weight on front wheel Wheel- base
cm(in)
Center of gravity height cm Seat height cm(in) Bottom (front) bracket height cm(in)
Traditional LWB 700 0.683 406 0.467 36% 168(66) 76 53(21) 33(13)
Future 700 0.683 406 0.467 36% 178(70) 66 43(17) 33(13)
Palomino 700 0.683 406 0.467 40% 188(74) 60 36(14) 48(19)
Raised Long Wheelb.   700 0.683 406 0.467 36% 170(67) 78 53(21) 58(23)
Moonlight 700 0.683 406 0.467 45% 170(67) 66 41(16) 66(26)
Compact Long WB   406 0.467 305 0.366 30% 132(52) 85 63(25) 38(15)
Flat on back High R   700 0.683 700 0.683 50% 147(58) 86 68(27) 84(33)
700 wheel High Racer   700 0.683 700 0.683 50% 119(47) 86 61(24) 86(34)
650 wheel straight HR   650 0.632 650 0.632 50% 119(47) 81 56(22) 81(32)
650 wheel curved HR   650 0.632 650 0.632 50% 112(44) 73 48(19) 73(29)
24" wheel High Racer 24" 0.582 24" 0.582 50% 114(45) 68 43(17) 68(27)
20" wheel straight frame   406 0.467 406 0.467 50% 122(48)   76 51(20) 61(24)
20" curved frame 406 0.467 406 0.467 50% 127(50) 66 41(16) 66(26)
Typical Short WB   700 0.683 406 0.467 43% 120(47) 78 53(21) 63(25)
Mid Racer SWB           700 0.683 406 0.467 48% 132(52) 66 41(16) 66(26)
700 Mid Racer 700 0.683 700 0.683 51% 130(51) 66 41(16) 66(26)
Low Racer   700 0.683 406 0.467 64% 130(51) 48 23(9) 48(19)
Long WB Low Racer   700 0.683 406 0.467 45% 196(77) 48 23(9) 48(19)
Flat on back Low Racer   700 0.683 406 0.467 68% 145(57) 41 23(9) 38(15)
700 wheel Low Racer   700 0.683 700 0.683 63% 132(52) 48 23(9) 48(19)
Flat on back 700 LR   700 0.683 700 0.683 64% 155(61) 51 33(13) 48(19)

Ride Roughness:

This was discussed more fully in the section on steering and ride.  To go over it quickly, you measure the distance from the center of gravity (usually around your belly button) to the bottom of each wheel and divide this by the wheelbase.

To find out how much vibration you'll get from the front wheel, measure from the center of gravity to the bottom of the back wheel; divide this by the wheelbase, square it, and divide the result by the actual outside diameter of the front wheel, in meters.  For the back wheel, repeat this, except you reverse what you need to reverse. To get a ride rating for the vehicle as a whole, multiply the rear ride rating by 0.9 (only an approximate value) and use whichever number is bigger.

Let me show you how this works with the bikes we're discussing in this section. The 'letter grade', based on the public school system, is an attempt to express the results in a way that's easily grasped, "A" being best and "E" worst.  (Finally, I get to see what an "A" on a report card looks like!) If you see slight discrepancies, I did the math to more decimal places then rounded things off.

Bike Distance
from CG
to bottom
of back
wheel
Distance
from CG
to bottom
of front
wheel
Rear
ride
roughness
Front
ride
roughness
Overall
ride
roughness
rating
Letter
grade
Traditional LWB 0.578 0.784 0.9 0.72 0.81 B
Future 0.517 0.74 0.8 0.57 0.72 B+
Palomino 0.512 0.68 0.68 0.56 0.61 A-
Raised LWB 0.583 0.787 0.91 0.73 0.82 B
Moonlight 0.594 0.673 0.66 0.76 0.76 B
Compact LWB 0.71 0.951 1.94 1.38 1.74 E-
Flat on back HR 0.77 0.77 0.87 0.87 .87 B-
700 wheel HR 0.879 0.879 1.13 1.13 1.13 C
650 HR straight 0.845 0.845 1.13 1.13 1.13 C
650 HR curved 0.821 0.821 1.07 1.07 1.07 C
24" wheel HR 0.778 0.778 1.04 1.04 1.04 C+
20" straight frame 0.799 0.799 1.37 1.37 1.37 D
20" curved frame 0.721 0.721 1.11 1.11 1.11 C
Typical SWB 0.779 0.865 1.09 1.3 1.3 D
Mid Racer SWB 0.693 0.721 .76 1.03 1.03 C+
700  Mid Racer 0.72 0.706 0.73 0.76 0.76 B
Low Racer 0.739 .516 0.39 1.17 1.17 C-
LWB Low Racer 0.513 0.602 0.53 0.56 0.56 A
Flat on back LR 0.736 0.427 0.27 1.16 1.16 C-
700 wheel LR 0.727 0.519 0.39 0.77 0.77 B
Flat on back 700 LR 0.57 0.487 0.35 0.48 0.48 A+

Remember it's taking your energy to shake the bike, so ride roughness = energy lost.  Other things being equal, the smoother riding bike goes faster, not to mention it's probably easier to pedal when you're not being rattled about.  This does not show in the speed calculations we're coming to later.

Hill Climbing Ability:

By this I mean up a steep hill, where air resistance barely matters.  Low racers generally do poorly in this, but their air drag is so low it often compensates for this on gentler hills.  In the section on frame design, we learned how the force on the idler is proportional to the length of a line drawn on the force diagram.  We also learned drivetrain length is a factor.  My own experience is mostly with monotube frames with the frames ovalized in the vertical direction.  As a very rough rule of thumb, in my experience with these frames, multiplying the length of that line by 3 then adding it to the length of the tensioned part of the chain agrees reasonably well with the bike's abilities on the hills.  It would be difficult to give a more precise rating to each bike design without knowing the type of frame you intend to build.  If you're building a monotube frame with round tubes, you would multiply the idler force by even more.  With a triangulated frame the effect of forces on the idler pulley can be much less.   Intelligent frame design makes quite a difference. Using bigger chainrings and cassette cogs helps too.

You will notice my beloved designs, Moonlight and Palomino, do poorly here.  They really aren't practical without a triangulated frame.  Low racers could use structural triangles, too, but they usually don't have enough vertical space for it.  A vertically ovalized frame would be a good idea here, as well as making the frame out of aluminum or carbon fiber to increase stiffness without adding weight.

Bikes that climb better also accelerate better, feel 'zippier' and feel like the bikes are lighter than they really are.

Rolling Resistance:

Here is the coefficient of rolling resistance for each bike, worked out from the chart for equivalent tires in the section on steering and ride.  It's also converted into drag force for a total bicycle + rider weight of 90 kg. (198 lb).

  HILL CLIMBING ROLLING  RESISTANCE
Bike "a"
Length of
chain in
tension
"b"
Force
on idler
Climbing
ability
 "b"x3+"a" 
Letter
grade
Coefficient
of rolling
resistance
Drag
force
in
newtons
Upright bicycle 41 0 41 A 0.00422 3.72
Traditional LWB 127 0 127 B 0.00492 4.34
Future 136 0 136 B 0.00492 4.34
Palomino 154 38 268 D+ 0.005 4.41
Raised LWB 138 0 138 B 0.00492 4.34
Moonlight 160 46 298 D 0.0051 4.5
Compact LWB 102 0 102 B+ 0.00668 5.9
Flat on back HR 167 6 185 C+ 0.00422 3.72
700 wheel HR 146 25 221 C 0.00422 3.72
650 straight HR 145 25 220 C 0.00456 4.02
650 curved HR 150 25 216 C 0.00456 4.02
24" curved HR 144 26 222 C 0.00495 4.37
20" straight frame 146 0 146 B- 0.00617 5.45
20" curved frame 150 31 243 C- 0.00617 5.45
Typical SWB 135 5 150 B- 0.00506 4.46
Mid Racer  SWB 146 40 266 D+ 0.00516 4.55
700 wheel mid racer 38 0 38 A 0.00422 3.72
Low Racer 172 66 370 E 0.00547 4.83
LWB Low Racer 172 66 370 E 0.0051 4.5
Flat on back LR 190 63 380 E 0.00555 4.89
700 wheel MBB LR 38 0 38 A 0.00422 3.72
Flat on back 700 MBB LR 38 38 A 0.00422 3.72

 

Cornering Ability:

This is not how the steering feels, but how hard you can corner before the wheels start to slip out from under you.  This is discussed further in the section on steering and ride.  If you’re not a racer, this is still important as it is a safety feature on wet roads, steep downhills, running on dirt and gravel, etc..

Here we’re giving the percent of weight on the front wheel divided by the percent of total wheel diameter on that wheel.  Numbers under 1.00, showing a ‘light’ front end, indicate a tendency for the front wheel to start to slide before the back one does.  This is characteristic of long wheelbase recumbents, the old air-cooled Beetle, and the Corvair. 

Numbers over 1.00 suggest the back wheel will let go first, like with lowracers or '60's musclecars.  This latter characteristic is easier to control and safer than the first.

Numbers around 1.00 mean you can jigger the locations of parts around when designing to get the properties you want.  I notice many uprights and highracers are designed to emphasize ride over steering, with a little less weight on their front wheel than the back.  Things can be refined further by using different tires.

In assigning a letter grade, I'm going a little easy because many people seem less picky.

  Percentage of wheel diameter Cornering score
Bike on front on rear Front
weight /
diameter
Letter
grade
Traditional LWB 41 36 0.89 B
Future 41 36 0.89 B
Palomino 41 40 0.98 A-
Raised LWB 41 36 0.89 B
Moonlight 41 45 1.11 A
Compact LWB 44 30 0.68 C
Flat on back HR 50 50 1 A
700 wheel HR 50 50 1 A
650 straight HR 50 50 1 A
650 curved HR 50 50 1 A
24" curved HR 50 50 1 A
20" straight frame 50 50 1 A
20" wheels curved 50 50 1 A
Typical SWB 41 43 1.06 A
Mid Racer SWB 41 48 1.18 A
700 wheel Mid Racer 50 51 1.02 A
Low Racer 41 64 1.58 B-
Long Wheelbase LR 41 45 1.11 A
Flat on back LR 41 68 1.67 B-
700 wheel LR 50 63 1.26 A-
Flat on back 700 LR 50 67 1.34 B+
 

Air Drag Again:

In the section on air drag, I explained that measurements other people have taken show that the air drag of a recumbent rider, without the rest of the bike, falls pretty close to a line described as:  the sine of the seat back angle, times 0.13, plus 0.12.   

I was thinking it might make life easier if I made up a little chart.  We're assuming a fairly normal size rider in tight clothes.  Air drag is given as Coefficient of Drag x Area, in square meters.

Approximate rider air drag for seat back angle.
Bike Seat back
angle from
horizontal
Rider air
drag
CdA / M2
Compact LWB 70° 0.242
Flat on back HR 65° 0.238
700 wheel HR 60° 0.233
650 straight HR 55° 0.226
650 curved HR 50° 0.22
24" curved HR 45° 0.212
20" straight frame 40° 0.203
20" wheels curved 35° 0.194
Typical SWB 30° 0.185
Mid Racer SWB 25° 0.175
700 wheel Mid Racer 20° 0.164
Low Racer 15° 0.154
Long Wheelbase LR 10° 0.143
Flat on back LR 0.131
700 wheel LR 0.12

To the rider's air drag, we add the air drag for each wheel, as described earlier.  Your best guess on the air drag is all we can do, it's not very precise.  Luckily with recumbents this isn't a big part of the total air drag.

I've carried things out to the third significant digit, which is useful if you're comparing different designs.  The whole air drag formula isn't accurate enough, though, to give a result of more than two significant figures.

Bike Seat back
angle from
horizontal
Rider air
drag CdA
Rear
wheel
air drag
Front
wheel
air drag
Total
air drag
in m2
Power
drag in
newtons
Power in
watts to
go 30 kph
(18.6 mph)
Power in
watts to
go 40 kph
(24.9 mph)
Cruise
at 150
watts
(kph)
Speed
letter
grade
Upright road bike - - - - 0.32 3.72 152 327 29.8 D
Traditional LWB 72° 0.244 0.029 0.034 0.31 4.34 153 322 29.8 D
Future 64° 0.237 0.021 0.023 0.28 4.34 143 299 30.6 D+
Palomino 49° 0.218 0.016 0.017 0.25 4.41 132 274 31.6 C
Raised LWB 51° 0.221 0.029 0.034 0.28 4.34 144 302 30.5 D+
Moonlight 35° 0.194 0.021 0.021 0.24 4.50 128 262 32.1 C+
Compact LWB 76° 0.246 0.055? .045? 0.35 5.90 181 375 27.7 E-
Flat on back HR 0.12 0.049 0.043 0.21 3.72 112 231 33.8 B
700 wheel HR 35° 0.194 0.039 0.035 0.27 3.72 133 281 31.5 C
650 straight HR 35° 0.194 0.037 0.032 0.26 4.02 134 280 31.4 C
650 curved HR 35° 0.194 0.029 0.025 0.25 4.02 128 267 32 C+
24" curved HR 35° 0.194 0.027 0.022 0.24 4.37 129 267 31.9 C+
20" straight frame 47° 0.215 0.038 0.034 0.29 5.45 155 318 29.6 D
20" curved frame 35° 0.194 0.027 0.021 0.24 5.45 138 278 31.1 C-
Typical SWB 47° 0.215 0.029 0.034 0.28 4.46 143 298 30.6 D+
Mid Racer SWB 35° 0.194 0.021 0.021 0.24 4.55 128 262 32 C+
700 Mid Racer 35° 0.194 0.021 0.019 0.23 3.72 120 251 32.8 B-
Low Racer 35° 0.194 0.009 0.008 0.21 4.83 121 244 32.8 B-
Long WB Low R 35° 0.194 0.009 0.008 0.21 4.50 118 240 33.1 B-
Flat on back LR 0.12 0.009 0.008 0.14 4.89 94 178 37.1 A+
700 wheel Low R 35° 0.194 0.009 0.009 0.21 3.72 112 232 33.8 B
Flat 700 wheel LR 0.12 0.014 0.013 0.15 3.72 88 174 37.7 A+

The chart above is probably my favorite in this whole section!  There are several interesting things in it.

If you skip the lowracers and that CLWB glorified boat anchor, there's only about a 10% difference in speed between the practical road bikes!  It certainly feels like more than that!

The raised bottom bracket LWB bikes were a bit disappointing.  When they were introduced, the Rans Velocity² and the Tomahawk/Javelin were promoted as ’performance’ long wheelbase bikes.  A Tour Easy with a Super Zipper fairing would be faster.

Laid back seats are showing their virtues!  Kent Polk of Synthetic Transport will retrofit your high racer with his very flat ‘rail gun’ seat, I expect some bikes will come like this standard before long.

The 24” wheel design is keeping right up there with the highracers!  Easier to live with, too.  Now if you could only get parts...

Real lowracers are faster than the one here.  This one is given the same rider position and wheels as used on several other bikes here, to make it easier to compare the different designs.

The long wheelbase lowracer seems a definite improvement over the regular short wheelbase variety.  The lower rolling resistance makes for the small speed increase that the chart shows, the reduction of vibration and more efficient power transfer would make other tiny speed increases the chart doesn’t show.  Further, they are more pleasant to ride- not that the hardcore lowracer racer cares much about that!

We should be seeing more ultra- laidback lowracers in the future.  John Morciglio of Thundervolt in Colorado already sells them.

 

Final Results:

We have now rated several of the more important characteristics of recumbent bikes.  While not perfect, it is a vast improvement over guesswork, and gives us some means of comparing things in meaningful, objective numbers.  It could all be improved, of course, with more careful measurements, but there is only so much this sort of analysis can do.  Bicycles interact with us more closely than just about any other form of transportation; in some ways it's hard to tell where the machine ends and rider begins.  In the end, deciding which bicycle to buy or build comes down to passion, and bicycles are more an art form than any other mode of transportation can ever hope to be.  These numbers are nothing more than a guide to help, hardly a set of rules, and there is so much more than this.  How difficult or expensive will it be to acquire this vehicle?  Will you be able to get parts if it breaks down in Podunk, IA?  Do you like it's looks?  Does it feel right?

I've been designing my next bicycle while writing this, alas, when finished, here will be nowhere to enter races with it.  I like fast bikes that can be used on real roads, and in recumbent races I'll just get stomped by the lowracers.

The British have solved this by creating a 'sport' class- just like the unfaired class, but with the additional requirement of a minimum eye height of 1.05 m. (42") off the ground.  This gives the rest of us, not just the lowracers, a real race we can participate in.  This means almost all the recumbents in use would have a class we can participate in.  Has anyone else noticed participation in HPV races going down?  Why not let useful bikes race?

Allowing the practical vehicles to race would also allow the rocket scientists among us a design challenge worthy of their talents- developing a well-rounded vehicle is more complicated than a speed vehicle, good at only one thing.  Such innovation would have a beneficial effect on production recumbents - has anyone else noticed recumbent design stagnating?  There's an old saying from the motor industry - win on Sunday, sell on Monday.

In hopes this may someday happen, all the bikes in the list except the five lowracers could race in this class.

Earlier I mentioned my homemade front suspension systems were absorbing some of the rider's power, so I developed bikes without.   Aarn Tate of New Zealand reports he has had good results with 'Pro shock' forks.

Next I'd like to develop partial fairings, and linear drives to cut down side area at the front of a fairing, to reduce the effect of crosswinds.  I'd also like to build a velomobile whose framework doubles as a roll cage to provide some protection to the rider.

Enjoy your journey.      Have fun!         Charles Brown-  CharlesMeredithBrown@gmail.com

 
One of the series of bikes that evolved into Palomino, 1990.  Photo by Mike Eliasohn
 

Back to the recumbent design page