Category Archives: Product Profiles

Cobra Linear Inner Tube – From BMX to Velomobile?

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photo of cobra Inner-tube

A rather ingenious product that came to my attention while reading up on the ELF velomobile was the Cobra Linear Inner-tube by flybikes.

Rather than having a full anulus as in a normal inner-tube the Cobra is a stright length of tubing sealed at both ends with a small loop allowing the both ends to be joined into a circle at the valve point.  I was not aware of the product before, but in hind sight it is really obvious and goes to show how one’s thinking can easily be limited by just doing things the way they have always been done.

This has several advantages.  Besides the claimed improvement in the speed of changing a flat tyre, flats can also be easily changed without the need to remove the wheel.  This obviously is of very significant use to most velomobiles.  While velomobile wheels are often cantilever mounted allowing access for a traditional inner-tube there is usually at least one wheel which is more difficult to access.  For example the the rear wheel in a tadpole based velomobile is usually mounted in a fork with the added complexity of a rear drive train and often partially or completely hidden within the body.  In such a case the Cobra would be a life saver.

The following video on Vimeo demonstrates the tube changing process.

While designed for BMX, Flybikes supply many BMX components, it is not clear in what sizes the tube is available besides the 20″ 406 standard BMX wheel size however, since many velomobiles use this size, it should be possible to fit the tube to several models.  It is interesting that Organic Transit explicitly recommend the use of a “Cobra or similar” tube for the ELF rear wheels which appear to be 26″.Photo showing cobra Inner-tube join

Some questions remain as to how the tube performs both in the short and long term but assuming you can source a tube in your wheel size it would still be a good idea to keep one and a pair of scissors in your velomobile emergency kit.

If any readers have any experience with this or similar inner-tubes please let us know via the comments below.

 

To Dronten and back by Velomobile

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Yesterday I cycled 45 km (28 miles) from Dronten to Putten in an Alleweder A4.

Photo of the Alleweder A4 in PuttenToday was unsettled and I waited till early afternoon before I returned.  On the return journey I managed to avoid getting lost in Harderwijk, as I had done yesterday, and also managed to follow a shorter route, less then 41 km ( miles).  As it happened, waiting for the weather to clear in Putten had minimum value as I had to contend with a lengthy shower from before Ermelo till I reached Harderwijk.  Once on Flevoland the weather was much improved and I had a mixture of sun shine and clouds all the way to Dronten.

Photo of Alleweder A4 on HarderdijkAgain I had opportunity to chat with Leo Vischer before retuning to Putten this time in a covered Sunrider.  I was able to follow the same route back with a couple of deviations which added approximately 1 km to the journey.  It was good to be able to compare the two different velomobiles over the same route, albeit in opposite directions, as there were both positive and negative differences, but more of that later.

Photo of a Sunrider outside AlligtThe mild soaking of the morning journey was nothing compared to the weather I had to contend with on the journey back to Putten.  The Sunrider cover proved it’s value!  My route took me along Harderdijk for about 5 km.  A straight two-way cycle path along the dyke separating Flevoland from the Zuider Zee.  For almost the whole length I was battered with a heavy squall.  The rain was so bad I had to cycle without my glasses.  While the Sunrider did leak in places, compared to the Alleweder I rode earlier, I was kept very dry!

Photo of Sunrider Velomobile looking along HarderdijkMy limited level of fitness prevents me from pushing these machines anywhere near there limits, and I am very slow, but I was pleased to observe I was able to cover almost twice the distance of my first day without the jelly-legs of the day before.  I am looking forward to the return journey tomorrow.