Canadian, Larry of the VeloRydr blog, has produced the following nice, “Benefits of a Velomobile,” graphic. The original graphic, featuring a Mango, has been supplemented by a number of variations featuring other velomobile models, including a quest and a WAW.
If your machine is not there, Larry may well do a variant for you, if you ask him nicely.
The Twike is one of those vehicles that really pushes the definition of velomobile to it’s limits. A two seater sociable delta trike it relies heavily (pun not intended) on a large lithium battery pack to augment the mechanical power provided by the two riders. First displayed at the World Expo in Vancouver in 1986. In production since 1992 the 1000th machine recently left the factory in Germany.
Christine Lepisto visited the manufacturer and has written an article on Treehugger, covering the history and giving an overview of the technology used in the Twike. In this article she attempts to ask the questions:
Christine writes from a “Green Motorist’s” perspective, comparing the Twike favourably to the Tesla electic car. However she concludes pessimistically that the Twike will remain a niche product while the rest of the world will turn to vehicles that reflect what they have always used.
While the perspective and the product are not fully aligned with the machines we usually look at, the article is none-the-less well worth reading. The writing is somewhat terse and there are areas where one would like to know more detail but as an overview it is helpful.
Christine concludes with a reference to the TW4XP (TWIKE 4 the X-Prize) which took 3rd place in the Progressive Automotive X Prize and asks if this is a preview of the next generation.
The ELF is a relatively large electric assist velomobile currently being developed by Organic Transit in the US. Australian Tech Blog Gizmag recently posted an article highlighting the combined human and solar power sources utilised by the ELF, and also the proposed price of $4,000, which they compared favourably to two other North American produced velombiles, the Hornet ($5,700) and the Tripod ($7,450).
Organic Transit (OT) have adopted a somewhat different design approach to their velomobile, and that, combined with a Kickstarter campaign, is the secret to the relatively low cost. The campaign has been very successful so far, and, with more than 3 weeks still remaining, they have raised more than 125% of the original $100,000 goal. They have already produced several prototypes which have been used to refine the design and build process. Their plan is to release the first 100 production units through Kickstarter.
As is customary on Kickstarter a promotional video has been produced highlighting the proposed product. This can be viewed below. There is also a fairly extensive write up of the development process that OT has gone through to reach this stage on their Kickstarter page. It is particularly interesting that they plan to replace a hand-laid GRP process, that takes two hours to build a body panel, with a vacuum moulded ABS process that takes a mere 12 minutes!
From the above sources and the OT FAQ several interesting facts can be gleaned.
Orgainc Transit are primarily based in Durham, North Carolina but have team members in several states. The team behind the ELF are professional with strong connections to the US Human Powered Vehicle movement. Perhaps the most well known is C. Michael Lewis, who will be known to some as the artist behind numerous velomobile and HPV posters, such as those for Battle Mountain and ROAM.
While currently operating out of a former furniture store in downtown Durham, they have ambitions not only to sell the ELF, and it’s stable-mate the TruckIt, but more globally, to set up micro-factories producing the ELF in “every downtown.” To-date they have had enquiries from many places, including Europe, and they are seriously looking into ways to supply markets further afield than the US.
OT have followed the “Keep it simple” philosophy and are quite clear that they are not intending to compete with the more established, and more aerodynamic, velomobiles such as the Quest and the Mango. Their target is the thoroughly practical user who wants a highly visible vehicle with a large carrying capability and to whom speed is not a significant consideration. Hence the ELF is large – 8′ x 43″ x 5′ (2.4 x 1 x 1.5 m) and heavy – 100 lbs (45 kg).
To avoid the cost and complexity of suspension, OT have opted to use the standard MTB size of 26″ on all wheels, with large diameter tyres to smooth the ride. While simpler this does pose a concern as the front wheels will have to resist lateral forces not normally experienced by bicycle wheels and these forces are a function of the vehicle weight. The consensus so far on successful trikes and velomobiles has been to restrict the size of these wheels to not more than 20″.
The purist will reject the reliance on electric assist and there has been some perhaps unfair criticism of the ELF’s weight, but this should not be an undue problem for the intended user. However, as there is reference to options to add: doors, floor and other extras; one can see the weight rising as the design begins to bloat. One nice feature is the integrated solar panels which allow the batteries to be trickle charged during the day, assuming access to adequate sunlight. Otherwise the standard battery pack takes two hours to charge.
To conform to regulations, allowing the ELF to be classified as a bike, assisted top-speed is limited to 20 mph (32 km/h), but there is no reason why the rider can’t push the vehicle faster if they have the strength or gravity on their side. The following video is taken from an ELF driver’s eye view, about mid way through you hear a conversation between the ELF’s rider and a truck-driver about the potential speeds.
While the debate about “fast cycles” continues to rumble on, the current regulations, particularly those in Europe, that govern e-bikes and their classification impose relatively onerous requirements on vehicles that are classed as “more than a bike”. This makes it challenging to successfully develop and market a vehicle of this type. A recent article on the Low Tech Magazine blog, albeit featuring the highly aerodynamic WAW velomobile, argues the virtues of electric assisted velomobiles, much of which applies to the ELF, the second part of the article also goes into some of the issues with the current legislation.
One velomobile mentioned by the Low Tech article is the 55 kg Aerorider, developed in the mid 2000s. This vehicle with many similar attributes to the ELF failed to be commercially successful due to a combination of high cost, weight and the limitations imposed by regulation. It would be reasonable to say that if regulation had been favourable for a class of “fast bikes” the Aerorider would have done much better. As it stands the Aerorider was redesigned as the Sunrider which has now passed into the hands of Alligt, and Alligt are doing their part to lobby for a fast-bike class (snelfiets). As Alligt now have access to the moulds and tooling for the original Aerorider, should regulations change, one never knows, the Aerorider may ride again. Hopefully the ELF will continue to progress and, though lower cost, a different market and simplicity, be more successful than the Aerorider proved to be.
On interesting detail from the description of the Zampano, mentioned yesterday, was the use of fabric in the weather-proof body. Fabrics have been used before and various “socks” can be made or obtained, to extend the covering provided by a partial fairing which you might see mounted on a recumbent. Modern materials developed for out-door clothing find a ready application here, and the functionality is no doubt much appreciated by the recumbent rider, as they make their way through the end of year weather. One negative that immediately impresses when you look at such coverings, is the lack of style, due in a large part to the rather limited aerodynamic form which has been achieved.
This criticism however, need not be. Recumbent Gallery recently profiled a velomobile concept which as appeared on a number of design blogs by a Czech designer Martin Miklica. I have been unable to locate a website for Martin or his work but he evidently has other interests beside human powered transport. His concept for a four wheel, two seat, socialble basicly involves a light-weight rigid frame covered by a Softshell “stretchy” fabric. For all the criticisms one thing this vehicle does not lack is form and style.
Like so many concepts, once you look past the slick photo-real renderings, the engineer sees numerous technical shortcomings. Recumbent Gallery (RG) rightly observe that there appears to be no space in this design for the usual envelope needed to mount and use a normal crank drive. RG suggests this could be overcome by fitting some kind of linear drive. But once you have grasped the idea of using fixed structural elements to define the edge of the fabric form what is to stop you from adding some similar constraint to further define the shape in the middle, as this design already does toward the rear?
The possibilities from this approach have a lot of potential both to help reduce weight and cost, and also thereby to help reduce the cost of delivery of the product to the end user. It seems to be an ideal way to take Carl-Georg Rassmusen’s concept in the Leitra further, by surrounding the rider(s) in a protective cadge, sealed with an even lighter covering. My only misgiving would be concern over material durability in the real world, where the fabric cover would have to face up, not only to scuffs and rubs, but to sharps and cuts from both the natural and man made environments.
The constrained fabric cover, is already available in a primitive form, with Hase’s Klimax trike, a review of which is expected in the next issue of Velovision Magazine. But there are other prospects in the offing. RG also hints on a new fabric covered velomobile in development, from Czech recumbent makers AZUB, which will be the subject of the next post.
The criticism of the rigid tricycle format, which most velomobiles are based on, comes from the limited stability when cornering sharply at speed. The trike usually has the advantage of a mechanically elegant and simple steering or drive, comparable to a bicycle, with additional stability provided by the third wheel. On snow, ice and loose ground the trike is very stable when compared to a bike, as it will slide rather than fall. On hard ground however the bike has the advantage, being able to lean into curves. As a result the industry is beginning serious exploration of alternative designs with the potential to overcome this limitation.
Some designs and ideas were presented at the recent Velomobile Seminar. One solution is to take the mechanically simple trike layout and “improve” it by adding some kind of tilting function to counter the overturning force. For example the new VeloTilt design. There are arguments for and against, and challenges to over come but development work is moving ahead. Another alternative is to add an extra wheel to gain the stability of a quadricycle as illustrated by the Quatro.
Four wheel velomobiles are not new. Indeed many of the early “pedal cars” were four-wheelers. Mochet’s Velocar was originally designed on the behest of his wife so that his son would have a stable machine, and therefore safe in her view, on which to go out riding with his friends. The recumbent advantage was only discovered by accident as it were, once the Velocar was being used alongside other cycles.
An increasing number of modern quadricycles are starting to make an appearance some with velomobile features. One-such is the Zampano by Designwerks from Germany. At least one prototype has been produced and is illustrated here. Designwerks website is professionally produced in German, but there is little information on the present status of the project, or what if any plans there are for manufacture and sale.
Based on Google Translate the Zampano website states:
This innovative vehicle combines the benefits of the bicycle, car and public transport in one product without being unnecessarily burdened by their disadvantages. It consists of aluminum and high-tech materials such as carbon fiber, Makrolon and Goretex, is powered completely emission-free, has no parking spaces, is all-weather-resistant and also encloses its users. … Depending on the version an option for an electric motor will be available this fall. The time is ripe for a solution like this.
The German text also makes reference to a Manfred Klauda and Tretauto GmbH Munchen. If anyone can add more information please do so in the comments below.
The Valentina is an impressively styled velomobile from South America.
I first became aware of the design several months ago but I was reminded by a comment from a reader in Argentina. Both Velomobile production and use is concentrated in Europe with rapid growth starting to appear in the US but what about other parts of the world? Australia & New Zealand have an established industry but what about other countries and particularly South America? Brazil is no longer an emerging economy – it has emerged – so it is perhaps little surprise to see the beginnings of a velomobile industry there, but what of other neighbouring countries? If you know of any others please let us know in the comments below.
The Valentina is produced by David Bevilacqua in Florianópolis Brazil. There is a website in Portuguese (not Spanish) but there appears to be little technical information at present. The Valentina appears to be mounted on a regular recumbent trike and features a sophisticated lighting system and electric assist.
If anyone can offer more information please comment below.
Ben Cooper of Kinetics in Glasgow is advertising the sale of a velomobile, a green Rotovelo. Those who were at SPEZI in 2011 will recognise this as the velomobile Trisled brought over which subsequently went with Peter Eland to York for a review in Velovision Magazine. I saw the machine myself at the 2011 York CTC Cycle Show before it was then sold on to a purchaser in Scotland.
The Rotovelo received a lot of attention at it’s launch in 2011, both because of the novel (at least in velomobile terms) construction method, and the realistic potential of this construction method to significantly reduce the cost of a velomobile. Rather than using the time-consuming method of laying up a glass or carbon fibre body, the Rotovelo uses the same rotating moulding method used to form a kayak. This is both cheaper, quicker and more easily scaled to support large production volumes. Unfortunately, as Peter in the Velovision Review (Issue 41 Jun 2011) highlighted, while the production cost in Australia is low, once you added shipping and European import duties the cost was comparable to a much better equipped European built machine.
Seen here outside Kinetics in Glasgow, upgraded with a Rolhof hub, and asking for offers around £3,500 it certainly looks like a good deal.
The speed challenge at Battle Mountain starts today and the first piece of news is that Graeme Obree will not be competing. As Recumbent Gallery reported late last week, there are still some outstanding issues with the fairing for Beastie so Mr Obree is now planing his speed attempt latter this year somewhere in the UK.
One interesting aspect, illustrated in an article on Humans Invent, is the transparent fairing. True to form Mr Obree has decided that he can produce something better. Rather than hurtle down the road hidden inside an opaque bullet he plans to make the “engine” visible, so you can see just what is going on inside.
After his UK attempt, maybe he will continue to refine his design and have something to take to the US next year?
Kris De Decker of Low-Tech Magazine kindly allowed me to republish an article from 2010 – The velomobile: high-tech bike or low-tech car? It gives and an excellent, but slightly dated, overview of the velomobile with a somewhat American flavour. As such the opinions expressed, especially those in the conclusion, are those of the original author. It is none-the-less well worth reading. Here it is largely unedited.
Picture: the Versatile.
Recumbent bikes with bodywork evoke a curious effect. They look as fast as a racing car or a jet fighter, but of course, they’re not.
Nevertheless, thanks to the recumbent position, the minimal weight and the outstanding aerodynamics, pedalling a “velomobile” requires three to four times less energy than pedalling a normal bicycle.
This higher energy efficiency can be converted felt in terms of comfort, but can also be utilised to attain higher speeds and longer distances – regular cyclists can easily maintain a cruising speed of 40 km/h (25 mph) or more. The velomobile thus becomes an excellent alternative to the automobile for medium distances, especially in bad weather.
Basically, a velomobile is a recumbent bike with the addition of a bodywork. Recumbent bikes are considered a bit weird, but they have some interesting advantages over normal bicycles. For example, a recumbent bike has no saddle but a comfortable seat with back support, so that you sit or lie more comfortably and can keep pedalling for longer. Because of their superior aerodynamic capabilities, pedalling on a recumbent takes less effort, allowing you to travel more quickly and further than on a normal bicycle. Recumbent bikes can have two, three or four wheels. Trikes (3 wheels) and quads (4 wheels) offer the additional benefit of stability.
Picture: the Scorpion.
A velomobile – almost always a trike – offers two extra advantages over normal recumbent tricycles. The bodywork protects the rider (and mechanical parts) from the weather, so that the vehicle can be used in any season or climate. Furthermore, the aerodynamic shape of the bodywork further improves the efficiency of the vehicle, with spectacular results.
Velomobile versus bicycle
From the table below (source.pdf) one can observe that the power output required to achieve a speed of 30 kilometres per hour (18.6 mph) in a state-of-the-art velomobile (the Quest) is only 79 watts, compared to 271 watts on a normal bicycle and 444 watts on a neglected bicycle. Pedalling at a speed of 30 km/h thus requires 3.5 times less energy with a velomobile than with a normal bicycle. Going flat out (a power output of 250 watts) gives you a speed of 29 km/h (18 mph) on a normal bicycle and 50 km/h (31 mph) on a velomobile.
Source: “The velomobile as a vehicle for more sustainable transportation” (pdf).
NASA rates the average long-term power output for a male adult at 75 watts, while fit individuals might easily sustain more than 100 watts for several hours, from 200 to 300 watts for one hour, and between 300 and 400 watts for at least 10 minutes. Lance Armstrong is said to have averaged between 475 and 500 watts for 38 minutes during an uphill climb in the 2001 Tour de France. (Source: The human powered home).
If you normally commute by bicycle, you can do two things with a velomobile: Retain the same speed as you normally do, but use 3.5 times less energy, or arrive at your destination twice as quickly with the same effort. This high efficiency greatly enlarges the range of a pedal powered vehicle. The bicycle is generally being viewed as a transport means for short distances, mostly below 5 kilometres or 3 miles (= cycling 15 minutes at a speed of 20km/h or 12.4 mph). However, the average distance of a car trip in Europe and in the US amounts to between 13 and 15 kilometres (8 and 9.3 miles).
Picture: the Sinner Mango Red Edition.
A velomobile reaches a constant cruising speed of 35 km/h (21.7 mph) with the same energy output, so that the distance covered in 15 minutes becomes 9 kilometres (5.5 miles) instead of 5 kilometres (3 miles). At a speed of 45 km/h (not unusual for a regular cyclist) the distance covered in 15 minutes becomes more than 11 kilometres (6.8 miles). Thus, twenty minutes of pedalling on a velomobile sufficiently covers an average automobile trip. The velomobile could replace a substantial portion of car miles, especially because the vehicles also protect their occupants from wind, rain and cold.
Picture: the Quest.
By definition, velomobiles are built for speed. The bodywork offers a distinct advantage at higher speeds, starting at 20 to 25 km/h (12.4 to 15.5 mph). Above those speeds, almost all energy produced by a cyclist is channelled toward combating air resistance. Because of the upright position, the aerodynamics of a cyclist on a normal bicycle are disappointing. A velomobile, on the other hand, suffers less air resistance than even the most aerodynamic sports car.
At lower speeds, however, the relatively heavy (25 to 40 kilograms) velomobile becomes a disadvantage. It accelerates slower than a normal bicycle, and has considerably more difficulty climbing a hill. An electric assist motor can solve this problem in hilly regions. The motor can help the velomobile climb, while energy can be recovered from the brakes during the descent. Of course, an electric assist can also be considered on flat terrain, an option that is gaining a lot of popularity these days.
Picture: the Leiba x-stream.
By definition, the velomobile is essentially built for longer distances. For shorter city trips the traditional bicycle is unbeatable. It accelerates faster, it is more manoeuvrable, and it is very easy to hop on and off.
Velomobile versus electric car
Dries Callebaut and Brecht Vandeputte, the Belgian designers of the WAW-velomobile, calculated how the efficiency of a velomobile relates to the efficiency of an electric automobile (using their own data and this source). During an eco-marathon earlier this year they equipped their velomobile with an electric motor, a complete substitution for pedal power. This is not really what the vehicle is intended for, but the advantage of the experiment is that it allows for an unequivocal comparison.
The energy consumption of the WAW was measured at 0.7 kWh per 100 kms (62 miles). This makes the velomobile in excess of 20 times more efficient than electric cars currently on the market. For example, the Nissan Leaf requires 15 kWh per 100 kms. The enormous difference is of course due to the enormous difference in weight. Without the battery, the Nissan weighs just over a ton, while the WAW weighs less than 30 kgs.
Picture: the Versatile.
For a human powered velomobile the comparison is a bit more complicated and open to interpretation, because a human does not run (primarily) on electricity, but on biomass. The efficiency of a human powered velomobile thus depends on what the cyclist eats (the efficiency of an electric car also depends on how the electricity is generated). Callebaut and Vandeputte set the primary energy use to 0.6 kWh/100 km for a vegetarian diet from your own garden, to 2.4 kWh per 100 km for the average diet of the western non-vegetarian.
Picture: the Versatile.
A human powered velomobile is thus 15 to 62 times more energy efficient than a Nissan Leaf. Not just 6 to 25 times, because we are comparing primary energy here. The 15 kWh that is consumed by the Nissan equates to around 37.5 kWh primary energy since electricity plants (in Europe) have an efficiency of 40 percent.
You can also argue that burning fat is a positive thing regardless of where food comes from, since obesity and a lack of exercise are endemic throughout the western world. The energy that is now being wasted in fitness centres, or the fat that is hanging in front of the television, could be put to good use as an oil substitute in transportation. In this view, the velomobile consumes (just as the cyclist and the pedestrian) 0,00 kWh per 100 kilometres.
Origins
The origins of the velomobile can be traced back to the beginnings of the twentieth century, but the modern, streamlined velomobile only appeared in the 1980s. The first commercially available velomobile was the Danish Leitra. In 1993, the Dutch Alleweder appeared on the market. About 500 of them were were sold in the Netherlands, Belgium and Germany throughout the 1990s.
Picture: the Alleweder.
The Alleweder introduced an important technological innovation: the self-supporting, monocoque coach work, similar in construction to that of a car – though much lighter. This gave the velomobile a sturdier construction without weighing it down. The suspension system introduced by the Alleweder was also inspired by automobiles. The bodywork of the original Alleweder is made from aluminum plates riveted together, a technique inspired by airplane builders.
With or without a roof
All velomobiles produced since then are based on the construction principles of the Alleweder. The only difference is that the bodywork no longer consists of aluminum but is made up of composites (like Kevlar). These materials are more expensive, but offer more freedom in designing the fairing, allowing for better aerodynamics.
Picture: the Go One 3.
A modern velomobile weighs between 24 and 40 kilograms, is about 250 centimetres long, 80 centimetres wide and 95 centimetres high. The three wheels have suspension and the bodywork has integrated rear view mirrors, head lights, indicators and (sometimes) brake lights. A velomobile also has a luggage compartment comparable to that of a sports car.
The present-day velomobile comes in two varieties: vehicles in which the head of the driver sticks out (like the Quest, the WAW, the Versatile, the Mango, the Velayo, and the Alleweder) and vehicles in which the driver is fully enclosed (like the Go-One, the Leiba, the Leitra, the Pannonrider and the Cab-Bike). In the case of a fully enclosed vehicle, part of the bodywork can be opened to get in and out. In a half-open velomobile, the driver enters and leaves via the hole where the head sticks through.
Velomobiles can have open or closed wheel arches. Closed wheel arches give better aerodynamics but they make the turning cycle larger and hamper the changing of a tyre.
Picture: the Pannonrider (picture credit) has solar panels on the bodywork (wind power is another option!).
Fully enclosed velomobiles give the best protection against bad weather, of course, but they do carry a few disadvantages. The main problem has to do with ventilation. Even in cold weather, the driver may “overheat”. A body that delivers 200 watts, produces around 1000 watts of waste heat, which mostly escapes via the head. In a fully enclosed velomobile hearing and sight are also affected. The windshield can steam up or it can become opaque because of rain or snow (windscreen wipers are not an option on any velomobile, probably because of the extra weight that would be added by motor and battery).
Picture: the Velayo.
A fully enclosed velomobile thus needs an efficient natural ventilation system (which can happen via air intake in the nose of the vehicle). Some manufacturers have come up with a compromise. The WAW has a small optional roof with a ventilation system that can be manipulated from the inside of the vehicle. It can be quickly installed and it fits in the trunk when folded up. The Versatile also has a smart roof, bypassing the heat and ventilation problem while still protecting the rider from the rain.
Picture: the Hase Klimax.
The German manufacturer Hase recently presented a recumbent tricycle with a foldable fairing (and an electric assist motor). This is not a compromise between a fully or a semi-enclosed velomobile but between the latter and a normal recumbent trike – the most comfortable and aerodynamic option in warm weather.
Two-seaters
Recently, some two-seater velomobiles have appeared, such as the Bakmobiel (a cargo bike) and the DuoQuest. The essential idea is that occupants sit next to each other. It’s good to see that cosiness still beats aerodynamics.
Another recent trend are velomobiles that have been especially designed to easily hop in and out of. The adapted design lowers weather protection and aerodynamics, but the result is still a more efficient bicycle at higher speeds, which comes in handy for shorter distances.
Are velomobiles too expensive?
The high purchase price is often mentioned as one of the largest obstacles for a breakthrough of the velomobile in the mainstream market. A fully equipped machine will cost you at least 5,000 euro (6,700 dollar) – considerably more than what you pay for a good quality bicycle. In the US prices have come down from a level twice as high, since now some of the popular Northern European brands are also produced in the States. Shipping a velomobile across the Atlantic is not cheap.
Picture: the Quest.
The high price stems partly from the surcharge of a recumbent, but mainly from bodywork. Each velomobile is hand-crafted, with the fairing requiring the most work. It would of course be cheaper to produce velomobiles on an assembly line, especially when this would happen in a low-wage country. But even then – including social exploitation and extra environmental costs – nobody expects to see a velomobile sold for less than half the current price. Lightweight materials, crucial to make the technology work, just happen to be expensive.
Picture: the Quest.
You can look at it differently, of course. A velomobile is more expensive than a bicycle, but it is cheaper than an automobile. Since the performance and the comfort are also in between that of a car and a bicycle, the price starts to look more reasonable. Moreover, a car requires fuel, and a velomobile doesn’t. Maintenance is limited to changing the tyres. Whoever changes his or her automobile for a velomobile is definitely making a economical decision. Governments could help overcome the purchase price by financially supporting velomobiles instead of electric cars and biofuels – at least their ecological gain is clear and they don’t need a completely new charging infrastructure.
Alternative to the automobile?
The most important obstacle for the velomobile is not the purchase price. It is the competition of the automobile. Although a velomobile can ride on a wide enough bicycle path, because of its larger dimension and higher speeds the vehicle is more suited for the road. The concept of the velomobile is sound as long as the vehicle does not have to share the road with automobiles. On current roads, piloting a velomobile would be relatively dangerous. Car drivers don’t always see you, and in spite of the many strengthenings in the bodywork you are very vulnerable against, say, a Jeep Cherokee.
Picture: the Alleweder.
A breakthrough in the velomobile thus requires either a completely new infrastructure for pedal power, or the substitution of velomobiles (and other human powered vehicles) for automobiles on the existing local and regional road system. The latter option, which I prefer, would not be conducive to car sales, but there is nothing or nobody that stops car manufacturers from producing velomobiles.
© Kris De Decker (edited by Shameez Joubert)