Owning a Cruzbike Sofrider (a type of front wheel drive recumbent - see www.cruzbike.com) for 18 months until I sold it last year has got me thinking about some of the fundamentals of cycle design, and what is essentially the 'holy grail' of bike/HPV design - how to deliver:
1: The maximum power available from any given rider together with....
2: The least drag or wind resistance whilst providing......
3: Comfort, and...
4: Everyday usability.

The traditional diamond frame (DF) bike is pretty poor in respect of the first two, and is really only still with us as a result of the famous 1930's ruling by competitive cycling's governing body that banned recumbents from competition. I guess this has over the years, greatly limited the cycle R&D process. Does anyone really believe that the DF is the most efficient design layout for a bike, except for possibly downhill/mountain bikes?

However, I got to wondering, what proper scientific research has ever been done into the fundamentals of bike layout. It seems to me that it wouldn't be difficult to fit the the pedals/cranks of different bikes (or for that matter stationary exercise bikes) with strain gauges to measure the force being exerted (by the same rider) with different realtionships between the riders position relative to the seat, bars, and pedals/bottom bracket. Similarly, drag effect is not difficult to measure either in a wind tunnel, or even out on an airfield somewhere cycling into a steady wind.

To my simplistic and untrained mind the theory must go something like this:
DF: you can only exert a little more downforce on the pedals that the riders weight. Drag is pretty much at a maximum for any type of bike with an upright riding position, and much reduced in the crouch (as per your roadie/competitive cyclist), but then serious (dis) comfort and visibility issues come into play.

Semi-recumbent/crank forward designs: Additional pedal force is available from the leg muscles when the rider is ether braced against a seatback, or pulling on the handle bars. In the case of the Cruzbike both are used, in addition, the force required to conteract the effect that pushing on the pedals has on the steering, pretty much forces you to use the power of your arms together with your legs. I guess having the seatback too reclined - certainly by more than 45 degrees - is counter productive, as the force of the push from your legs would tend to move you backwards and upwards off the seat. So some trade off with aerodynamic drag effects here. Some designs - like the RANS (Fusion range) crank forwards - have no seatback as such to push against, but they apparently climb very well as you just pull on the bars. Obviously, the big aerodynamic benefit of the reclined riding position over the DF is a reduction in drag, but I wonder how significant the differences in drag really are between the various degrees of recumbency i.e. between 'full' and semi-recumbent designs. Having ones legs more horizontal must result in the biggest reduction in frontal area, with the angle of recline of the torso having less impact?

'Full' recumbent (high and low racer designs): Lower drag, but there must surely be some trade off between this and the push from your legs trying to dislodge you from your seat? The biggest problem with (very) recumbent bikes is the difficulty in balancing - at low speeds and starting off especially, and poor visibility, both from the point of view of seeing, and for low racer types being seen.

So which layout offers the best compromise for an everyday leisure/light touring bike - the type that the majority of people would want? Is there much documented research out there?

I'd be very interested to hear the views of those readers with much greater engineering knowledge, and experience or riding many different types of bike than myself. Personally, I've only ever had various DF bikes, a small wheel folder, and my Cruzbike Sofrider. I'm after comfort and usability especially for longer leisure/touring use. All bikes are comprmises, and the 'ideal' bike does not exist. As far as I'm concerned a small wheel folder (Dahon/Brompton) is ideal for short rides and around urban areas. My principal driver is the discomfort I find sitting on a conventional DF bike saddle, and this is what made me look into recumbents in the first instance rather than the performance aspect.

If you are wanting technical facts you probably won't get them here. But an assumption you made is up for challenge.

Practical experience of riding an AZUB recumbent bike 20" front wheel and 26" back wheel, my QNT with seat less than 8" from the ground and my Kettwiesel seat 18" from the ground tells me people see me far better than they ever did in my DF days. I ride in town and out of town and in the days when I rode the AZUB, QNT and lots of DFs (I had 9 bikes at the time.) The scariest days were always the DF days when drivers seemed to compete in seeing how close they could get to my elbows. On the other hand drivers cross the white line in the middle of the road when they pass me on a trike and people even stop and wave me out at junctions! I am certainly visible to the driver behind and in front of me. I use a flag on my QNT so the driver following the car following me can see I'm there, although on the odd occasion when I've forgotten to fit the flag I can't say I've noticed any different driver behaviour.



Seeing

"I thought of that while riding my bike." --Albert Einstein, on the Theory of Relativity

2007 ICE QNT
2008 Hase Kettwiesel AL27
2011 Catrike Trail.
1951 Engine in need of partial rebuild.

I'm certain that Leonardo da Vinci would be backing the recumbent trike as the most
suitable and civilized hpv.

It makes no sense to sit on a saddle, grip handlebars and have your centre of gravity so high that the incidents of falling off/over are high.
For normal relaxed recumbent riding there is very little need to put your back into it , or pull with your arms.
Although climbing is accomplished by spinning low gears, this is more efficient than standing up on the pedals.

I've cycled 122 miles in one day and got up to 62mph on my trike.Something I'd never do on a df.It can be fulled loaded with camping gear and still tow a trailer.
It would be interesting to compare power output from a df and a bent.
Better still look for grins or grimaces.
(I have volunteer, but we have other plans for him at York.)
The results should reflect not only comfort, but practicality under all conditions.

Well said n-ick. Grins wins!

"I thought of that while riding my bike." --Albert Einstein, on the Theory of Relativity

2007 ICE QNT
2008 Hase Kettwiesel AL27
2011 Catrike Trail.
1951 Engine in need of partial rebuild.

Whilst I'm a keen advocate of 'bents for the reasons above and more, I feel I should say some words in defence of the DF. I don't agree entirely that the 1930s ruling is responsible for their preponderance - they manage a bunch of compromises fairly well and produce a "best fit" result. No, DFs are not the most comfortable, the fastest, the best load carriers; but one bike can do all of these things passably well. I was off on my upright touring bike earlier in the week on a mix of country roads, A roads, steep hills, and for some 10 miles old drove roads and sheep tracks. The same bike can carry home a week's shopping and I can stick it on my shoulder and carry it up flights of stairs or across the trackless wilds (which I have done). Whilst I love my 'bent trikes, they do some things very well but don't have the versatility of the upright bike, which is probably why it remains the predominant design across the world. Recumbents (and other variants) are often finely tuned tools that do their job often better than the generic design; the DF is more of a Swiss Army knife that does lots of things at least passably well.

A DF bike can be very light and rigid. The transmission can be direct and efficient. It can accommodate large wheels for lower rolling resistance and a smoother ride. The problem is that it's not very aero when you sit upright, and it's not very comfortable when you lean forward. And it's a long way to fall if you come off.

go to Belgiam or Holland and like at the bikes there that they ride and day.

The question of "best" bike layout is analagous to "best" car layout.
Depends on what you use it for .

Certainly in Belgium and Holland, where there are falt expanses and cyle tracks are ideal for Dutch style bikism.

Thanks for all the replies gents. Sorry I forgot to mention trikes in my OP, I have ridden some briefly at D-Tek, and although I can see many of the benefits, being so low down is the killer for me. I still think there is more risk of you not being seen (by drivers) and for me one of the pleasures of cycling is the view of the countryside which is usually more restricted on a trike or low racer bent. I'm very drawn (in theory) to the RANS Fusion crank forwards which I intend to try out soon. They seem to promise much of the comfort of a bent with the advantages of a DF. Alternatively, they may just incorporate all the disadvantages of both types. The proof will be in the riding. Incidentally, as a last ditch attempt to make my DF more 'butt friendly' I have tried a couple of 'comfort' saddles. The Rido saddle - as recommended by Peter in VV - I have found to be uncomfortable as it seems to be too resilient and causes pressure on the sit bones. I am currently trying the Comfort Saddle; made in the UK by an outfit based in Norfolk. This is a 'noseless' design and the jury is still out on it's comfort - it's not all that comfortable whilst on the bike, but when you get off you feel as if you have never been on - if you see what I mean. Interestingly, the lack of a nose doesn't in any way make me feel less in control or at one with the bike as I feared it may.

BobT.
I understand your concerns re being low down. It's the reason why I won't drive my Ferrari on the road! ;-)

Seriously, while your perception is understandable, practical experience says being lower makes you more visible due to the well known WTF? factor.

"I thought of that while riding my bike." --Albert Einstein, on the Theory of Relativity

2007 ICE QNT
2008 Hase Kettwiesel AL27
2011 Catrike Trail.
1951 Engine in need of partial rebuild.

Some good points have been made here and I don’t think there is an answer for the perfect position or layout , DF, Recumbent, Semi-Recumbent & Trike, that will suit all riding occasions, all will be compromised in one situation or other. I am lucky to have more than one bike depending on where I am going to ride and what mood I am in.

Genesis Day 02 FlatBar Road
Great for long rides in the Wolds and hills are not a problem

Marin Full Sus Mountain Bike
For raking round Dalby and the local bridal ways

Slyway Explorer (sort of high racer in the right hands)
My Sunday bike , rides on the flatter parts away from the curious onlookers

From my own experience, I loved my Catrike road it was a hoot to ride but the thing that made me sell it was the lack of visibility. When riding in the country side (East Yorkshire Wolds) with the high hedges it became like riding in a green tunnel. And the main point of getting out for me, apart from the exercise was the view. This was reason I swapped it for the Slyway with the increase in view and still keep the fun of a recumbent.

My stable of bikes are a brompton, a DF tourer, a folding recumbent trike and a crank forward.
The brompton is a superbly versatile bike for commuting and where the bike is needed for compact storage. Not so comfortable for extended tours though.
The DF tourer is a great bike for loaded touring, more comfortable for extended riding than the brompton but less comfortable than the recumbent.
The folding trike is a different kettle of fish than all the bikes. Its very comfortable, carries a large load but less versatile than the other bikes. Its also very difficult to transport using public transport. Its not so sociable to ride with other upright cyclists as the trike can be slower or faster than the uprights and the rider's faces are at a different height. The seat on a bent-trike has to be very comfortable as there is very little position adjustment other than reclining the seat.
The crank forward is my favourite at the moment as uses the best of both the bent and the upright. It has a seat rather than a saddle and I find I have less discomfort on the wrists than the DF bike.
Its really horses for courses, different bikes for different purposes. If I was allowed only one bike it would be a close call between the DF tourer and the crank forward.

Blair, out of interest what type of crank forward do you have. As I said I am going to try the RANS soon.