The Hilgo story

How it all started

 SinnerBikes/Drymer has produced the Mango for more than a decade but the firm only developed recumbent bicycles and tricycles. The Mango was bought as a complete model from Velomobiel.nl. We have made many improvements to the Mango over the years and made a slightly modified body with much more luggage capacity which we named Mango Plus while re-branding the Mango to Mango Sport.
But developing a velomobile from scratch is quite something else as next to an efficient drivetrain, an aerodynamic body is at least as important. Since air is not something one can physically grab and test, we needed someone with real knowledge and experience in this field to come up with a fresh look for a new model.

So when German velonaut Delta Hotel (real name withheld) optimized a crashed MangoPlus for his own use, I became interested in his project. DH has been profesionally active in composites, with flying gliders as a hobby. DH made his design theoretically more efficient and through tests with water and compressed air he showed that the design really causes less turbulence and thus experiences less air resistence. A first prototype, first dubbed #4 by DH, later Erlkönig and Exclusive when SinnerBikes became more involved, was still a bit rough around the edges but already sported a very promising performance.

Hilgo vs. Mango body

So what are the differences from the final body that carries the name Hilgo and it's predecessor Mango Plus . Because at first sight the Hilgo is only slightly narrower and lower. Length is the same as from the Mango. It is in details like making sharp edges and rounding off the body elsewhere in such a way that turbulence is reduced. But moreover the droplet shape, which was long believed to be the most optimal shape was abondened. The body line as seen from above, stays wide until behind the shoulder to then taper off quick and sharp to a tail that is still wide enough for a rear light and plenty reflective material. Making a very long velomobile body does not contribute a lot to make it even more efficient. This was good news to SinnerBikes, as we wanted to maintain the body as compact as possible and stay with a 3x20" wheel set-up.

The inner room on the other hand is larger. With the front wheels standing up more straight, the space between the wheelboxes could become wider. So there is more room for big legs. And since the Hilgo is based on the Mango+, the luggage space is plenty for a cycling holiday with full camping gear.

Double Vision

So far so good: we had a body. But when it came to the drivetrain, there was a big difference in vision between Delta Hotel and me. Delta Hotel wanted to be able to mount an electric hub motor in the 20" rear wheel. A rigid double swing arm was mandatory for that. Me on the other hand, while being all in favor of having the possibility to easily mount an e-motor, found electric assistance not the first thing to think of in a velomobile and the place of the derailer at the small 20" wheel problematic. DH thought of having a small intermediate gear under the seat but for the life of me, I could not find the room needed for what he had in mind. It simply would take up too much space vertically and ground clearance too much compromised.
In my experience not only as a long distance rider and velomobile builder/repairer, but also as contact person with our customers, ease of maintenance is very important for riders to remain happy for their choice of velomobile in the long run. In my contacts especially with oversea customers, it showed that it was not always easy for riders to do the maintenance themselves, not in the least because of difficult access to the parts. A bicycle repair man (Monthy Python style) is not available in the Australian Outback. So it was vital to make maintenance of the Hilgo as easily as possible. The parts themselves are close enough to normal bicycle parts, the problem is that it is harder to see them and get to them then on a a normal bicycle. Now when a Mango arrives at the SinnerBikes repair stand, the question usually is: is it worth to take the time to remove the top in order to work easier or can we do the job through the entrance and the foothole openings. Even for experienced velomobile repairers a removed top makes the job much easier and also more likely that the job gets done well.

So laminating the top to the body irreversibly, like most velomobile factories have taken up, was completely out of the question for me. A hatch here and there is no match for a completely open top. The problem was how to make taking the top off and putting it on again could be made easier and quicker. Gluing the bolts and a wing nut on top was one piece of the puzzle, the other was to put a layer of kit on the flanges of both top and body, spread the kit evenly and let them harden out overnight. Kit only has to be applied once and does not have to be removed (....) and re-applied every time. Thus the time needed to open and close the top again was vastly reduced from some 70minutes to only 15-20 minutes.

So while this all is already pretty exciting, the real news is the gearing of the Hilgo. For me as a testrider it was clear that a wide-range MTB Kassette complemented with either a 34/50T double or 30/39/52T triple was the way to go to achieve a gearing that was not only palatable for the flats in the Netherlands but to also appeal to say: riders in Germany, France, Austria and Britain where flat roads are the exception, rather than the rule.

A direct drive to the rear wheel I tried out on the road, but as I noted above, the very tight clearance at the 20" rear wheel was not in accordance with the ease-of-access-to-components requirement as well as the difficulty to make a wide gearing range in a highly limited space. We went back to our roots: a mid-drive just in front of the rear wheel box. In tests with my TransforMango, I already found that a mid-drive could be made that is only marginally less efficient than a direct chain to the rear wheel. 

The KISS principle: Hilgo-gearing.

The break through came when senior advisor Jan coined the idea to replace the derailer with a simple gliding rail that moves the return idler. (Jan held a patent for a sliding cassette, which would be just ideal in the Hilgo, but for it's complexity and high cost of production). 

Now the hard work of optimizing began: making a prototype, fitting it in the Hilgo and test it on the road. After several iterations we had it nailed. A standard 11-speed 11-40 cassette shifted perfectly with a non-indexed Hilgo gearing which has no spring to push back, but instead two shifting cables, pulling the rail in either direction. Shifting action is very light, so  the grip-shift can be twisted even with very sweaty hands.The biggest problem for me as a test rider, was to get rid oft he hand-brain automatisation that I learned from the long use of indexed derailers.  The Hilgo-gearing is almost frictionless and has no ratchets to feel when you shift. You shift through the soles of your cycling shoes.  Young colleague Donny, who's hobby it is to restore vintage bicycles, showed me the way: "oh, you just pedal along and turn the shifter until you feel that it shifts". And that is really all there is to the Hilgo-gearing. In 5500 test-km the Hilgo-gearing indicates low maintenance and trouble-free use.  As for keeping the rail moving smoothly: the first idea was to seal the moving rail to keep it clean. But as this was not all too easy and the system was still in development anyway, this was postponed. After a while of use, I noticed that after lubricating the chain, the rail of the gearing was automatically lubricated as well. Problem solved by itself.... Dust is kept in solution in oil and the gearing keeps on shifting just as smooth as new. The open rail allows for an occasional cleaning, say two times a year.....
All in all the Hilgo-gearing is a true KISS system: Keep It Simple and Straightforward.

Ease of maintenance to the max.

To make the ease of maintenance complete I had already decided against chain-tubes and a for an open chain-tensioner that allows for the chain being taken off without opening the chain. One can release the tension on the chain when working on the chainline and a dropped chain can easily be popped on again.
The simple chain tensioner does not have a spring, but a bungee-cord. It may not be high-tech, but at least it is easy to see how it works and a bungee-cord replacement is easy to find and made to the correct length. The chain tension is rather low this way. Now, normally a derailer system on a bouncy road needs a high tension to avoid ghost shifting, but since the gearing is positioned at the mid-drive, it is free from wild rear wheel movements.  A low chain tension is great because it means a more efficient drive-train.
The chain tensioner is in front of the bridge and there is enough space for a very long cage. With the standard configuration of 34/50T Compact double and 11-40T cassette, all the gears can be shifted without losing chain tension. This at itself is already pretty revolutionary. That also means that 34/60T double chainwheels is a very real possibility, which makes for an even wider gearing range. One only needs to realize that on the 34T, not all the gears on the cassette can be shifted, so you need to switch to the big 60T ring in time.

Drop-In

I was also more than done with the traditional drop-outs that holds the mid-drive axle in the Mango. The mid-drive could literally drop-out when the quick-release was not tightened enough. That usually bent the drop-out in the frame on one side. The drop-out can be bent back and the axle can be held by an additional mount to prevent it from dropping out, but well, it's not a nice thing to happen on the road.
As the ongoing frame from the Mango was also history in the Hilgo, I had to think of something else anyway. It was crystal clear that the mid-drive had to be mounted in a drop-in. That way the weight of the mid-drive could never move itself down and out again. It's now even easier than it already was in the Mango to remove the whole mid-drive assembly for say: putting on a new cassette or replace the secondary chain-line from standard 24-16T to 22-18T for more extreme mountain use.

Q

Not so very exciting maybe, but still a good improvement is the small q-faktor of the cranks. In other words, the distance between the cranks is smaller than usual with "normal" bikes. It is better to have the cranks closer together, so why is the q-factor of most bikes so wide? This is because of the chainline on normal bikes, The chain has to go next to the frame and the rear wheel towards the cassette and this forces a wider q-factor upon the rider. It's not so bad on a normal bike, since one can stand on the pedals occasionally. At least this is my best guess... On a recumbent and a velomobile one is not so adaptable. You cannot stand on the pedals. This is why it feels better to have a smaller q-factor on recumbents/velomobiles. Although I don't want to generalise: cyclists' bodies and preferences can vary a lot.
Still, for the average velonaut I very much expect better ergonomics with a smaller q-factor. Not to mention that it becomes easier for long-legged persons to fit inside the Hilgo body ;-)
But next to no manufacturer seems to make cranks with a small q-factor. It took ICB some persuasion to get one manufacturer to make a crank with smaller q-factor but alas, the crank length cannot be made shorter than so much.
I did not like to be restricted to an expensive crankset and a shortest length that seems too long for me and possibly others, so I looked on. Then I thought about the old square taper cranksets. While with modern two-piece cranksets you cannot choose the length of the axle, with a square taper bottom bracket you can choose for a much shorter axle. Instead of 107mm or 113mm axle, there are 103 mm and even 102mm square taper axles. They are not commonly used, but they are readily available and that's what counts. Combined with equally readily available BMX cranksets with 110mm BCD that can be ordered in a great variety of lenghts from 125mm to 170mm in 5 mm increments, I found the ideal crankset set-up for the Hilgo, adjustable to individual needs and/or preferences.

Hub-motor in mid-drive?

Some clever minds have noticed how the drop-in mid-drive might allow for a compact rear-hub e-motor with the 11-40T cassette to replace the standard 135mm axle. One could ride without motor in summer and only put it in in wintertime when it is that easy to swap between the two hubs.Batteries could just lie on the velo floor and even the controller could be taken out when so desired. Being not very knowledgeable myself about e-motors,  I'm cautious about this possibility until we can confirm it. But it sure looks like a real option.

Anything else?

That's about all for the moment, but already a lot of ideas come about for the future. A carbon version is in the cards, a top with a very long entrance, front rings that can be shifted while standing still. With a small company like SinnerBikes/Drymer it can take some time for major changes to bring about.  I hope for people who see the Hilgo as an open source project. Some things that riders/tinkerers think off and try out might even get into production, others will remain a one-off. We shall see what the future brings. The Hilgo is adaptable....

Personal thoughts

The whole process of development of the Hilgo, the discussions with Delta Hotel and all the team members of Drymer, the failures and the "Eureka" moments, the hard heads not wanting to budge, finding myself often in the middle and finding the path towards a production Hilgo. It has all contributed to my own development as a person. I have gained tremendously in self-esteem, something I have never had a lot off. I hope I have also risen in the esteem of others :-) I think it is time to call myself not just a velomobile repair-man but also a velomobile-developer. Not.... that I could possibly develop a velomobile all by myself.
Ha, a photo has now been posted on FB with me giving the Hilgo my personal "seal of approval". That is no joke: I truly love riding the Hilgo.