Friday, September 8, 2017

Swingarm swinging a bit too much!


Swingarm swinging a bit too much!
More velomobile problems.  I guess that this cycling season has not been good to me, the weather was very bad this year with a late start due to the snow lingering much longer that usual, this was followed by record rain and colder temperature.   As I mentioned previously, work has also kept me from riding regularly.  If that was not enough, I documented a few mechanical problems with my velomobile and some were a bit unusual and I had to wait for parts to arrive to address these mechanical issues.

This week I discovered another unusual problem.  A couple of riders have contacted me to say that they had discovered some excessive play on the rear wheel of their velomobile equipped with a carbon fiber swingarm.  I was a bit intrigued so I checked mine and I saw significant play. I can move the rear wheel more than more than 5mm from side to side.

After looking at different possibilities like a loose swingarm, worn wheel bearings, worn axle, I was able to pinpoint the problem.  The glue holding the bushings inside the swingarm that hold the axle appear to be failing.  I removed the wheel and cassette and reinserted the axle and when I put side pressure on the axle I can see the bushings move while the glob of glue appear to stand still.

video

After an exchanged of e-mail with ICB, I’m sending the swingarm to Europe to be fixed.  Ymte also confirmed that there have been a few other cases where the same problem occurred.  I will be visiting Dronten soon and will bring back the swingarm home.

One more issue I’ve discovered is the mounting point at the top of the rear shock.  The bolt holding the shock is starting to make the hole in carbon fiber a bit bigger even if the bolt is properly tightened.  I think that there should be a grommet to support the bolt on each side of the carbon fiber tube so the bolt never comes in contact with the carbon fiber.

As mentioned previously, I will soon visit several velomobile manufacturers in Europe.  I will report on my findings upon my return.

Velomobiel

Velomobiel introduced the Quattrovelo+ (orange one) next to the standard Quattrovelo. The new model is larger than the current Quattrovelo and offers 2,5 cm more space for knees and 1,5 cm for feet. It is suitable for riders taller than 185 cm or those who have longer legs and larger feet.

IntercityBike

After a few quiet months, designer Daniel Fenn gave a cryptic update on the DF4 project.  It looks like he is reconsidering the 1 wheel drive and is working on a velomobile with traction on both rear wheels… unless it is both front wheels!  Daniel indicated that the new velomobile should still be lighter and faster than the QuattroVelo and Quest.

A few weeks ago I mentioned the new lighter swingarm that Daniel Fenn recently designed for the DF.  A few more details have surfaced.  The swingarm will be a bit smaller enabling the installation of a larger 622 wheel but restricted to the use of a narrow tire that is probably 28mm or less.  The swingarm will have a rounded end to allow different cable routing for other derailleurs. This was necessary since SRAM discontinued the 10-speed XO.  Bearings currently holding the swingarm and connecting to the two velomobile mounting points will be replaced by lighter Igidur bushings at mounting points (which might also change a bit).   The aluminium axle bushings will be replaced by a solid carbon sleeve should solve the problem of glue not holding.  The swingarm could be retrofitted to most DF but may require substantial work to be fitted-in.  The swingarm layout is fairly complex will probably go into production in the fall-winter timeframe.   Price has not yet been set and will be based on production cost.

Finnish Recumbent Championships

Saukki produced a video on his participation in the Finnish recumbent championships.  In addition to Saukki’s performance, there were a number of others who did very well too.  Of particular note Tero Haapanen in his DF velomobile who dominated the events including a top speed of 81km/h on the 200m flying start.

You can see the full results here: http://www.rrfi.fi/en/#portfolioModal4

Schwalbe

Schwalbe has published the 2018 catalog https://www.schwalbe.com/en/catalogesflyer.html of particular interest is the arrival of the Pro-One 28-559.

Bluevelo

While not confirmed, it looks like the old Quest molds are going to the American Midwest.  Stay tuned!    

Monday, July 31, 2017

No time!


No time!
Here is a post of information I gathered over the past few weeks some of them exciting and I want to share.  Unfortunately I have problem finding time to ride or write posts these days. 

For several weeks I’ve been without my velomobile.  After a ride I noticed wear on my new tires.  It turned out to be a flat spot on my Schwalbe Pro One from a minuscule skid as I came to a stop on a small patch of sand over pavement.  At first I suspected that the wear was due to the alignment.  I installed the jig and checked the alignment and found that indeed it was off a few mm.

When I checked for the source of the problem, I found that the bolts had not come loose but I noticed that that the tie rod end bearing on the left side was pulled out of the socket.  This affected the alignment a few mm.  In fact the protection boot was holding the ball in place.  I checked the other side and saw that it was starting to come out.  I did not want to take a chance with trying to re-insert the ball inside the socket.   


I tried to find a source in North America and found none that offered the exact same bearings off the shelf.  I contacted Ymte at ICB and he put some in the mail for me.  Postal delivery and customs make this process fairly lengthy.  After a few weeks I received the parts but currently my garage is full of building supplies, the DF is not easily accessible and I have not had the space or time to complete the repair.  We’ve had a very rainy spring and summer so far so nice riding days have been limited so far so it seems like I did not miss too much.

Several uncommon issues have prevented me from riding my velomobile this year.   It may have something to do with the poor road conditions I experienced early on.  Finding that my rims were cracked was one of these issues.  To address this, I ordered new wheels and rims from Ginkgo.  The new front wheels have the 90mm drums with heat sinks from Ginkgo.  I can use the wheels when I ride in mountainous regions when brakes have a tendency to fade after long and/or steep descents.  The wheels are noticeably heavier than those that came with the DF.  I hope this will not have a huge effect on speed, acceleration and climbing ability.  I also ordered replacement rims and spokes to repair the old wheels.  I am planning to use the repaired wheels for day to day riding.

Hopefully over the next week or so I will be able to fix the velomobile and go riding again.

Drymer/Sinner

It is a busy time at Drymer and Sinnerbikes  the company announced that they were appointed the official Milan velomobiles dealer for the Netherlands by the German manufacturer Raderwerk .

Models like the Milan SL, GT, RS and 4.2 can now be purchased via Drymer.

A few days after, pictures of the new Hilgo were released on Facebook.  The new velomobile is an improvement on the Mango, made of carbon fiber, it is lighter and slightly narrower than the Mango this will provide the ability to go through normal doors.  The first production Hilgo is undergoing testing before being released. The Hilgo already sports a new hood and will be available for 7650€.  Already there are hints of future versions of the Hilgo, possibly one with a Milan type entry hatch.

InterCityBike

Daniel has revealed a new lighter swingarm for the DF weighting 660g complete.  It apparently can be retrofitted to current DF.  The new swingarm should allow the installation of larger wheels on the DF.

Schwalbe

The German manufacturer seems to be making things difficult for velomobile users looking for fast tires.  After cancelling the popular Shredda size 406, the company just announced that the also popular Schwalbe One HS462 size 28-406 will no longer be available.  The tire competes with the Schwalbe Pro-One wireless of the same size.  It is unfortunate that the velomobile market can’t sustain these tires.  The BMX market is the main market for 20in (406) tires.

Trisled

The Australian company appears to be making history one more time.  Trisled recently released pictures and a few details of their newest prototype.  The new velomobile is a significant departure from previous PedalPrix velomobiles.  The unnamed prototype appears to be a full carbon fiber monocoque Aquilla.  Currently it is my understanding that all PedalPrix velomobiles from all manufacturers have a metal frame covered with a shell.  Furthermore, the new tadpole velomobile apparently has front wheel drive and front wheel steering that is probably also a first in the world of tadpole velomobiles.  There are no details or pictures available yet of the structural or mechanical systems.

Byess

I am sad to report that brothers Andreas and Michael Byess have split up their business after 25 years.  The company has been a significant player in the velomobile industry.  Andreas will continue building the current Go-One models Evo R, K and Ks. Michael will not be involved in velomobile production, he will continue to produce manufacture precision parts.  Over the past couple of years Michael had released plans for the replacement of the Evo-K and Evo-R but Michael had indicated that the lack of resources probably due to slow sales of current models prevented the completion of the projects.  Andreas plans on making modest improvements to current models.

Bluevelo

Ray Mickevius posted on BROL that several moldsfor producing velomobiles are available for enterprising individuals.  The molds are for the Cab Bike, Hornet and Team velomobiles.  The molds come with several parts including two working velomobiles. The asking price is C$9 500.  Ray had put Quest molds for sale and while a few people are interested, they are still available.

Friday, June 23, 2017

My recent velomobile issues and solutions


My recent velomobile issues and solutions
My recent posts on velomobile efficiency appear to have been well received.  There were numerous comments and debate on several points.  I think that there is room for the type of general information to let people better understand velomobiles, as well as I observe as it relates to velomobiles including the technology, racing and commercial aspects.  Looking at the subject I have touched on in the past, I think that I have covered a many subjects but I’m still looking for new subjects to address and I’m open to suggestions.

While I’m writing this, outside the velomobile world, I’m also very busy with other activities and I may not be able to post as often as I would like.  This also affected my riding, in addition to renovation work underway, the weather, large flooding throughout the region and a bumper crop of biting insects has made difficult to ride.

I had a few other setbacks on the velomobile front.  I wanted to get new tires for my velomobile.  I wanted to convert a set of narrow wheels for tubeless while keeping my regular wheels for general riding and brevets because the road conditions are not so good especially in the spring.  I purchased a set of Schwalbe Pro One for the front and a Schwalbe One for the rear from Schwalbe North America as no distributors in Canada had the tires available.  The Schwalbe One tire was not available in size 28-406 in North America so I ordered the 28-406 from Europe and placed another order for matching tubes.  A few days after the order, I received a message from Bike 24 that the tires are in back order with no delivery date.  So I cancelled and placed my order with Ginkgo where stock was apparently available.  I received the tires but they were Pro-one instead, the company decided to upgrade me since they too had no stock.  I was a bit disappointed since I wanted to compare the two versions.  Meanwhile, the latex tubes sent before were no show and after a few more weeks, the package was lost I contacted Ginkgo and they sent me another set of tubes. 

During some maintenance after a brevet I realised that my wheels needed to be trued.  I removed the wheels and took them to a local bike mechanic.  When the wheels came back, the mechanic informed me that two of the rims had a few cracks around the spokes.  I looked at my options and decided to buy a new set of wheels with ventilated hubs as I have had a few close calls after long descents and these may help keep the brakes cooler.  I also bought new rims, spokes and  bearings to replace those on my existing wheels leaving me with a set of spare wheels.

While I had the wheels off, I proceeded to change the L-bracket that holds the steering and suspension.  I mentioned some time ago that the brackets were upgraded to calm the twitchy steering of the early DF and DF-XL.  The new brackets change the steering geometry somewhat. 
 
The old and the new notice the position of the two smaller hole in the middle
The process was fairly quick but I needed to perform an alignment after this.  I used the method developed by Charles Snyder and published on BROL.  I could not get reliable readings in large part because the wheel covers… well cover the rims.  It is hard to see if they are perfectly aligned.  I tried my best to make the measurements but when I went for a ride with the new tires, the velomobile did not feel right, it was pulling to the side and my average speed was reduced by approximately 8km/h.  I needed to do something to fix this.  I looked at other ways to perform the alignment and decided that it would not be too hard to build a new jig that is much more accurate.

Using 5/16in T-Slot tracks, 4in L-bars and some 1/4in bolts, I made two accurate jigs that measure the wheel spacing at the front and rear simultaneously. It did not take too long after I gathered all the parts.
Overall view of the new tool

Close-up on L-brackets


I took my new tool and proceeded to perform an alignment.  I had marked the middle of the tool as a reference to align with the middle of the velomobile.  I used my laser level to find, mark and align the tool and velomobile.  I had placed the brackets on each side 70cm apart but I found that when the middle was aligned, the brackets on the right side of the velomobile were touching the wheels while the left side was about 3cm away from the wheels.  I could not understand what was going on.
The left and right sides do not match

I suspected that the shell was not symmetrical so I checked with PeterB who had performed a few alignments on his DF and with Ymte and they confirmed that the shell is not symmetrical.  This is important for those of you who will want to perform a wheel alignment on a velomobile.

Performing the alignment
After this I performed the alignment without taking into consideration the symmetry.  I was able to get 1.7mm toe-in and took the DF for a ride, my first ride in a few weeks with the new tires (with regular tubes), alignment and the new L-bracket.  I’m happy to report that the steering has improved, the velomobile is much more predictable but there was a significant speed improvement.  Even with my lack of riding, I was able to come close to the best results I posted a few years ago on the same route.  I hope to be riding more in the next few weeks and hopefully improve on those results.

Visit to the heartland
I am currently planning a visit to Europe and the Netherlands in the fall (September-October) and will take the opportunity to meet with velomobile manufacturers and riders.  I hope to be able to see new velomobiles, discuss with those involved about the opportunity and challenges for velomobiles as well as learning from what is done in their enronment.  I should attend the race at the Dykes on October 15th.  Please let me know if there are any opportunity to meet.

Trisled

The Australian manufacturer appears to be embracing 4-wheel velomobiles.  After the success of the 4-wheel tandem velomobile, braking the tandem 24 hour distance record, the company announced what is probably the first Australian PedalPrix 4-wheel velomobile.  There are few details released but the new velomobile will be tested at the next PedalPrix race.  Here is what we know so far: Completely new chassis design with absolutely no main tube, radical new drive system Ben has been working on for 20 years,  Some comments seem to indicate that the drivetrain may propel the left wheel, this would be similar to the DF-4.  The designers paid special attention to the aerodynamics in the design and the velomobile was completely CAD modeled and CFD tested.  The 4-wheel design should provide safety and stability of four wheels! In the rough and tumble world of PedalPrix racing.

InterCityBike

ICB is apparently designing a foam panel to close the area around the rear swing arm and should be available soon. While it is best to use a bag for small items., this panel is designed to contain loose items from traveling to the rear derailleur compartment.  The cover will be attached to the shelf, reinforcement rib and chain cover with Velcro fasteners. There will still be some small openings such as around the inner swing arm mount and the chain tunnel. ICB is not ready for orders yet so don't start ordering them immediately, there will be an official announcement on the website.. That's why the velomobile bag is provided.

WHPVA World Championships

The championships were recently held in Mannhein Germany with participants from several European countries.  Velomobiles took the first places in all events even ahead of Beano the Streamliner (2 wheels).   There is a bit of controversy regarding the event, maybe there is room for improvement for the next WC.
Results for the WC2017:
1 hour airport crit: http://www.hpv-wm-2017.de/index.…/…/ergebnisse-de/41-1-hour…
333m velodrome flying lap: http://www.hpv-wm-2017.de/…/en/ergebnisse…/38-333-3m-sprint…
1km velodrome standing start: http://www.hpv-wm-2017.de/…/ergebnisse-de/40-1-000-m-sprint…
3 Hour city centre crit: http://www.hpv-wm-2017.de/index.…/…/ergebnisse-de/42-3-hour…
Pictures https://www.wjst.de/images/pretty/central/2017HPVWMMannhein/

Tuesday, May 23, 2017

Efficiency (3)


Efficiency (3)
Velomobile efficiency is one of the best reasons to own a velomobile.  This is the third post, the first was on aerodynamics, the second on rolling resistance and today I will cover weight and mechanical efficiency.  Each velomobile is different so the discussion has to be general in nature. 

I received many good comments on my previous post regarding rolling resistance and some pointed to items I did not mention.  First, it is clear that a tire/tube combination at a given pressure may work best in specific conditions but may not be optimal in all conditions.  There needs to be experimentation to find what is best in your riding environment.  All the measurements will provide some avenues to explore or give you a quick gauge for comparing but they do not provide a definitive comparison for your conditions.

Weight
Weight is an important characteristic of velomobile performance.  Weight has an impact on acceleration and ability to climb hills.  There are significant differences in the weight of commercial velomobiles, are in the 22-23kg range while others are in the 40 to 60kg range.  This is something to consider when choosing a velomobile because the rider has to move that weight.  Currently a racing velomobile can be in the 12 to 15kg range and we could see a sub 20kg production velomobile in the not too distant future.

Weight in cycling is very important.  Several years ago the UCI has mandated that road bikes should not be lighter than 6.8kg, this is to ensure that riders do not have an undue advantage when climbing or accelerating and it was also to ensure that manufacturers are not cutting corners affecting rider safety in the process of making a bike lighter.  Nowadays, with better techniques and materials bike manufacturers can easily make safe bicycles that are less than the 6.8kg limit and the UCI could easily revisit that rule to help increase the performance of cyclists.

As you can see the weight of a velomobile is significantly more than the weight of a good road bike. Even the lightest racing velomobiles mentioned above are nearly twice the weight of a good road bike.

When climbing up a hill, a production velomobile is at a significant disadvantage compared to a road bike.  A rider in the best production velomobile has to push the equivalent weight of more than three road bikes up a hill and it could be almost 8 road bikes for the not so light velomobiles.  Since there is no aerodynamic advantage on steep hills and the weight and rolling resistance of the 3 smaller wheels makes the effort more difficult for the velomobile.  As a result, the rider has to expend more energy to climb steep hills and the velomobile will not be able to match the speed of a road bike.

Fortunately, the added weight will be an advantage on descents and increase momentum and that is desirable when the road has a number of short rolling hills.  The energy stored will enable the experienced rider carry the momentum of the descent into the next climb almost effortlessly and at great speed while a road bike rider would need to climb each one.

Of course if one could reduce the weight of the velomobile, there could be important performance gains to be made.  Top velomobile designers will use their skills to choose the best materials to reduce weight and improve performance.  In choosing a velomobile many people will place the looks over other important characteristics such as the weight.  There are a few things the average rider can do to reduce the weight of a velomobile including some choices can be made at purchase time like the type of drivetrain.  But unless you are racing, some things like lighter wheels and tires for the velomobile may not provide a significant improvement since the resulting savings would only reduce the weight by a few percent of the overall weight of the velomobile, the same change would be three or more times as important for a road bike.  A velomobile used on public roads may encounter several hazards and velonauts should be careful when considering lighter components since they can potentially trade-off weight for sturdiness, it depends on the material used and the type of construction.  A light wheel for example could fold more easily in a pothole.

However rider who would like to improve performance can decide if they should be installing optional equipment like a sound system.  An even easier way to reduce weight is looking at what they carry in the velomobile.  I’m probably guilty of carrying too much as I like to be prepared for most eventualities.  Leaving at home the kitchen sink, personal anvil or other stuff seldom used could probably help you get better performance.  It is very likely that you carry a kg of stuff that is not really required.

Mechanical Efficiency
Mechanical is the last element of efficiency; power needs to be transferred from the pedals to the wheel with the smallest loss possible.  Most of this is determined by the design of the velomobile and components but for the most determined rider, it is possible to make some improvements.   I make my comments based on velomobiles with rear-wheel powered tadpole trike configuration because they are by far the most popular, however some but not all of these comments will apply to other models (delta or 4-wheel). 

Getting power to the wheel efficiently requires stiffness.  The crank, boom and swingarm are all elements that contribute significantly to stiffness but the monocoque shell or the frame, as the backbone, is the glue that holds everything together.  When pressure is applied on the pedals, any torsion or unwanted movement of any components will result in a loss of power transfer.  The unwanted movement can be a very small lateral movement of the boom or the swingarm but the loss will be noticeable.  The movement can be so small that you would not be able to see it while riding.  Well-designed components made of materials like carbon fiber instead of aluminum normally provide more stiffness.

People realising the issue have modified their velomobiles to increase stiffness.  Being the most popular velomobile, many changes were reported for the Quest in particular in order to address this issue.  Some of the changes include the replacement of the aluminum coat hanger used to provide stiffness in the turtledeck area and the point of attachment for the rear shock.  The replacement made of carbon fiber material creates an attachment point at the top of the wheel well.  A second change is the replacement of the aluminum swingarm with the newer carbon fiber version.  A third change is the installation of a carbon fiber pillar to give rigidity to the aluminum boom.  A number of riders also have added carbon fiber ribs in several areas of the shell.  Many of these improvements could also be made on different models of velomobile with similar results.  These changes also have the potential of adding extra weight with minimal stiffness improvements so one has to be careful in making this type of modifications by carefully researching, planning and implementing them.   In the case of plastics like the Rotovelo, while I cannot confirm this, I expect that the plastic material would be much less stiff and may contribute to a loss of performance that may be significant, especially in the case of the Rotovelo where there is virtually no additional metal frame.

In addition to stiffness, the drivetrain can be a source of power loss.  Chain line rubbing, unnecessary chain tube, damaged or missing idlers, bad alignment of chain line components are possible sources of power loss.

Suspension can also rob significant power; every push on the pedal can contract the rear suspension to some degree.  This is particularly noticeable when climbing a steep hill at low cadence.  There could be a significant bobbing effect.  Instead of using the power on the pedal to turn the wheel, part of the energy is used to compress the rear shock.  The problem can be larger when the rear shock is soft.  Adding more air in an air/oil shock or installing stiffer springs or polymer in a mechanical shock could improve efficiency.
 
 Bearings play an important role in the velomobile efficiency.  Since all bearings are not created equal, for the same size bearing, there are several categories, some have looser tolerances and there is a bit more movement inside so they do not roll as well as others, I would call them cheap but there are others that are of tighter tolerance and are more efficient.  In the United States there are 5 classes of bearings (ABEC1, 3, 5, 7, 9 with 9 being the best) but since bearings are made in many countries, they may use another standard such as the ISO and DIN that have similar levels, see table below. Bearing classes explained
 
ANSI Standard 20
ISO 492
DIN 620
ABEC 1
Class Normal
P0
ABEC 3
Class 6
P6
ABEC 5
Class 5
P5
ABEC 7
Class 4
P4
ABEC 9
Class 2
P2

The different classes take into consideration several factors that will affect performance internal clearance, surface finish, ball accuracy, torque, noise, cage type, and lubrication Some racers use the lowest friction bearings to lower resistance and improve performance but the gain could be small relative to the increased cost for those bearings.  A 406 wheel equipped with 28mm tires will turn almost 10 times a second at 50km/h and small movement could make you lose significant power but the loss is even greater if those same bearings are worn or damaged.

It may surprise some people but bearings in the front wheels can be subjected to intense heat generated by hub brakes.  Excessive heat can also contribute to bearing failure.  Repeated long descents under load may cause bearings to fail.

There are bearings in wheels, pedals, bottom bracket, cassette and some can be changed some cannot because they are sealed inside the unit and you may have to change the whole unit (cassette, pedal, bottom bracket) if they are worn or damaged.  Idlers could have bearings or bushings and the bearings could be sealed too.  A damaged bearing or bushing will typically have one of many of the following unwanted movement (lateral or perpendicular), difficulty turning, noise (grinding, rubbing) or other damage like missing or damaged seal.

A key aspect of power transfer is the drivetrain. There are many different types and all are not created equal.  Velomobile drivetrains borrow elements of several bicycle systems but they are different in several ways from traditional bicycles.  First difference is the chain length; velomobiles have the equivalent of 3 standard lengths of chain.  To function properly the drivetrain also needs idlers, tensioners, chain tubes to transfer the power from the pedals to the wheels, something only recumbent bikes use.  Second, because velomobiles have higher top speed than unfaired bikes, velomobiles need higher gearing but due to their higher weight, they also need lower gearing than most road bikes to climb steep hills.  As a result, the required gearing range is much greater than the gearing used by other bikes.  This means that components are often near or at the maximum capacity.  To meet the requirements, velomobile designers will mix and match different components made for different types of bikes (grupo) for example road and mountain bikes and even urban bikes.  They have larger chain rings some pushing 75 teeth, wider range cassette e.g.:  11-36 or more. 

Most often, high capacity long cage rear derailleurs will be chosen to handle the range.  I expect that designers will soon take advantage of the 11 and 12 speed rear derailleur developed for mountain biking with wide range gearing and install them in velomobiles soon.  It may not be a slam-dunk for velomobile applications there are several potential issues.  First, since the internal space required for the extra long cage derailleurs and the smaller chain may create some issues.  It is also not clear if the rear derailleurs designed to be used for single ring applications could handle the extra chain required for a 2 X11 or 2X12 configuration especially if the big and small ring has a big difference in the size of the rings e.g.: 62-34. 

When operating at or near the limit of components that were not designed together, one has to be careful that efficiency is not affected significantly.  Some of the new wide range cassettes may not fit standard hubs but if they did they may create issues.  There are cassettes with 9 and 10 teeth that are used to provide the speed for mountain bikes racing down hills or for trikes with smaller wheels.  In their applications they could be fine because these gears are only used seldom going down a hill for example but they are highly inefficient.  In velomobiles, we will tend to use the higher gearing even on flat ground and for much longer periods of time.  The angle of the tooth spacing increases and the chain does not sit in the grove very well; to illustrate this at the extreme, imagine a 4-tooth cog, the teeth would be spaced 90 deg.  The chain would get stuck or skip when you would try to turn the crank.  I have a bike with a Capreo hub with a cassette that has a 10-tooth cog and I find it awkward to pedal and I can feel the inefficiency.  Some road racers don’t even use 11-tooth cog on their cassette because they feel they are inefficient but I think they are OK in velomobiles.  As a side note, it is not certain that cassettes with 9 and 10-tooth cogs could be fitted on to velomobile axles as they are typically require installation onto smaller diameter hubs.

Velomobile with smaller rear wheels (20in/406 or 16in/349) at the rear will require higher gearing, to compensate because the smaller wheel means that it has to turn significantly more than a 26in wheel to achieve the same speed.  To address this issue, manufacturers will often install a mid drive; a secondary gearing that can be as simple as a 3-speed cassette and derailleur to Internal Geared Hubs (IGH) like a Rohloff.  Mid-drives add some amount of drag but can provide a much larger gear range.

As mentioned above, it is possible to use other gearing system like the IGH. There are different make and model of IGH with their pros and cons, there are also a few pedal-based internal gearbox and even hybrid systems that have an IGH coupled with a cassette and there is also crank based systems like the Schlumpf that multiply your gearing.  They each have significant advantages including providing a wide range of gears, some have the ability to change gears when at a standstill and they have low maintenance.  Unfortunately, some of those are noisy and can be heavy and may have torque limitations that can be exceeded by velomobiles under certain conditions and can’t be shifted under load.  As far as efficiency, some reports indicate that there is a 6% penalty for IGH compared to derailleur systems.  This can be significant for a performance-oriented rider and something to think about when making your choice for gearing.

There are other factors that could create power loss. In my previous post on rolling resistance, I mentioned ensuring proper alignment contributes to mechanical efficiency but so is truing of the wheels.  A wobbly wheel will sap your power because you will need to push harder to maintain your speed. While more rare, brake adjustment could be over-tightened and touch ever so slightly when the brake handle is released and this is another thing that could sap your power.  Brake adjustment should be part of proper regular maintenance. In short, if it rubs, squeaks or grinds it probably robs your power and needs to be fixed.

Lastly for a good velomobile, you also need efficient brakes to keep velomobile rider safe.  Most velomobile use drum brakes on the front wheels.  There are 70mm and 90mm drums and both will stop a velomobile efficiently on flat ground but when the road gets hilly, 70mm brakes will probably be unable to meet the challenge, the brakes will quickly overheat.  The larger 90mm version will fare better but they will eventually overheat and lose their braking efficiency.  There are 90mm drum brakes with added fins to cool brakes faster and some riders have designed simple water injection system to further cool brakes.  Riders in mountainous areas should consider these enhancements.  There are some velomobiles equipped with disk brakes that may offer better braking in some conditions but they require more maintenance and many have switched to drum brakes.

Through this three part series on velomobile efficiency I think that I have covered most elements affecting efficiency and performance. While I’ve touched on many things, the information is fairly superficial and there is much more to investigate to deepen your knowledge; an ocean wide but a foot deep.  There is still a lot to be researched and I would hope those who can add apiece to the puzzle would publish their findings through public forums so everyone can learn.  I hope that these post provided you a glimpse into what makes a velomobile efficient.

Effigear

A new pedal-based gearbox designed for mountain biking is now available. EFFIGEAR's has a gear ratio of 444% with 9-speed providing a similar range as derailleur-based, double chainring 24/36t with an 11/34t cassette.  This system provides the ability to shift under load contrary to other IGH and gearbox systems.  The gearbox system weighs 2.8kg including cranks and shifters.  The gearbox can also be used with a rear derailleur to further increase the range.  Unfortunately to install in a velomobile would require the design of a new crank mount.  This system is similar to the Pinion gearbox that offers several systems from 9 gear 568% ratio, 12 gear 600% ratio to an18 gears and 636% ratio.

www.effigear.com

SPEZI

If you did not have a chance to attend SPEZI this year, there are several who reported on the annual show including The Laiback Report with an excellent Spezi video tour and interviews.  . Wim Schermer reports on SPEZI on his blog  and Ligfiets reports on several items of interest