Velogical velgdynamo's

Op de hoofdpagina schreef ik in de afdeling van nieuws van fabrikanten:

2013-3-3: Ik zag de webpagina over een nieuwe velgdynamo van voligical lang geleden (ik meen midden 2012) maar het leek me niet echt interessant. Velg- en banddynamo's hebben te veel nadelen, dus noem ik hem hier alleen als curiositeit: http://www.velogical-engineering.com/rim-dynamo.

en in het gedeelte waarin ik dynamo's die mogelijk interessant zijn opnoem:

De velogical velgdynamo is een curiositeit. Hij lijkt me niet al te interessant vanwege mogelijke problemen in de regen, omdat het rubber relatief snel vervangen moet worden, en omdat de prijs aardig hoog is, nl. ca. € 150,-. Ik las er al midden 2012 over en hij schijnt zomer 2013 beschikbaar te komen. Vermogen is lager dan van andere dynamo's, dus hij voldoet niet aan de duitse (StVZO) eis van 3W bij 15km/h. Mijn ervaringen met een velgdynamo van Sanyo (ergens jaren 1990) zijn niet positief in de regen, maar mischien dat dit als noodvoorziening te gebruiken is voor diegenen die niet veel in het donker fietsen, en ik neem aan dat hij geen lawaai maakt i.t.t. dynamo's die op banden lopen.

Nog te vertalen naar NL:

At first there was just one such dynamo, but on 2013-9-19 I revisited the page on these dynamos to create this page with a user report on the only model then made, which was the sport model (I think), and now there are 3. From the site:

Massa: ?
Zelf te onderhouden: ?

Report based on an email exchange of a bicycle builder with me, about using the Velogical dynamo (original one, which is the 'Sport' it seems) which he allowed to be used for on my website.:


One of his customers agreed to test the new Velogical rim dynamo on a so called "demi-course" in French or "Halbrenner" in German, i.e. a road bike but more comfortable, with wider tyres and and some possibility to take light luggage (see the pictures).

The dynamo seems of high quality, extremely compact and light, low noise, easy to install on the bike.

The instructions for the wiring are to put a 5W bulb in parallel series with the headlamp, which is supposed to lower the resistance (and the manufacturer claims the dynamo heats up less then). This gave some problems in the LED headlamp Lyt not working in some cases, it was unclear why, so he disconnected the bulb which made everything work fine.

The mounting arm seems surprisingly small and looks fragile but it does the job. Maybe there isn't that much force... The weakness in his opinion is not slipping in wet weather but rather the fact this dynamo must be very close to the rim in the off position (3-5mm) and so the wheels must be very true. Also, if this is not the case then the effect of more/less pressure on the dynamo wheel is immediately visible with the headlight's output varying from weak to strong, with each turn of the wheel..

WHS: this shows that small imperfections in the rim's trueness already make the dynamo slip a bit when it's dry...

All in all he thinks the Velogical dynamo is only suitable to demi-course bicycles that will rarely use lighting and where you don't want to use battery powered lamps.

All dynamos have flickering lights due to imperfect wheels/tires/slipping, but when you pay €150 it's more disappointing. For use in more adverse conditions and/or bikes with wider tires, a Axa HR or B+M Dymotec would be preferable.

WHS: We need to differentiate in flickering coming from the dynamo due to e.g. slipping as with sidewall dynamos, and flickering from the headlamp because of not enough power coming from the dynamo or because of the low pulsed power from dynamo hubs (some headlamps then give a burst of light, get dark again, give a burst again with low power). So the flickering here with the Velogical dynamo can be caused in 2 ways... One as mentioned above, the other caused by the headlamp which tries to give light but the dynamo doesn't provide enough at low speeds (power output of the original velogical dynamo is less than standard StVZO dynamos).

He doesn't have an opinion yet on whether it's really worth the price, but his view was that that depends on whether it's reliable, which is not yet known.

WHS: Sounds logical to me :) Though for me it would not be worth it because of the possibility of slipping already when it's dry, never mind in the rain or with snow! Note that I haven't had a report yet on how well it works in the rain...

I got a comment from Velogical about this report, that the bulb used was actually meant for a dual headlamp setup (5W for dual lamp, 20W for single lamp)... Also that setting the tension with stronger rubber band should be able to take care of slipping. Well, I can only go by the report I got, and I have to go with the report from someone who used it above claims from a manufacturer. I cannot just accept a manufacturer's claim that "this will fix it" as true. If Velogical want to send me dynamo to test then I will see about testing it all myself under all circumstances and whether another rubber band helps, but I will let the comments as above stand (note that I discussed Velogical's response with the bike builder).

2014-7-21: Another report from someone who used the dynamo on the rear wheel of a bike:

I own the trekking model of the dynamo and so maybe I can add some points.

Some remarks about my setup: The dynamo runs on the backwheel of our back to back recumbent bike tandem. Some pics are here:

http://radseiten.die-andersecks.de/tandembau.php

The dynamo is not connected directly to any lighting components but to a Forumslader which is specifically adapted to the characteristics of the dynamo (thanks Jens During for that). The lighting is then done via a Busch & Müller Cyo Premium head lamp for e-bikes which is powered from the Forumslader's 12V buffer and which offers 7V to the rear light, the Philips Lumiring (you remember, we were already in a discussion about its power consumption while charging its capacitor). Apart from that we charge our GPS batteries, the digital camera and our phones from the Forumslader which during the last vacations were the main energy eaters.

One thing about the 5W bulb which is also mentioned in the report on your website: The manual doesn't claim to install the bulb in parallel with the headlamp but in series. Electrically it's totally clear that the headlamp doesn't do anything if the bulb is in parallel as its resistance is very low as long as it is cold. Therefore the current takes the way of the least resistance which doesn't lead through the headlamp When putting the bulb in series under low power it will have almost no resistance but when the dynamo speed increases it starts lighting, its resistance increases, too, and therefore both the dynamo and the lamps are more or less protected against to much current (which would let the dynamo overheat).

WHS: The dynamo was wired correctly I presume. Perhaps the times that it didn't work it was wired parallel... Or perhaps it was because of the wiring being wrong in some cases of because the wiring wasn't fully OK when testing. Whatever it was, it points to one problem with the dynamo when using the bulb, namely that the additional component introduces an added complexity in wiring and in connections.

Jens During, the Forumslader guy has tested the dynamo at high speed and written on the Liegeradforum about that: http://www.velomobilforum.de/forum/index.php?threads/compact-dynamo-am- federbein.38819/#post-567470

Back to my setup and my experiences: During our last vacations we had the dynamo running for more than 1000km. Its sound is of course noticable but acceptable. At around 30-40kph the wind around the ears becomes dominant and the dynamo cannot be heard anymore. When cycling with lights on the Forumslader shows a negative balance in its buffer when going at lower speeds but a positive balance when going faster (~30kph and more). This shows that with all the energy conversion losses the dynamo is well suitable for average bicycle lights. As mentioned earlier during vacation it was able to charge GPS, camera and phones faster than we discharged them while using them (okay, we had a look at not wasting too much energy, but we used them all). We never had any problems with slip when it was dry. But when it was wet it was only a small step to the dynamo not spinning at the correct speed anymore. It still runs but only slowly. According to the remaining sound it follows the bike's speed up to about 15kph and then remains there (of course depending on how wet it is) even if the bike accelerates further.

WHS: This is typical for any rim or tyre driven dynamo. I've experienced it with lots of them...

According to Velogical this behaviour also depends on the type of rim, its surface etc., but I cleaned our Remerx Super Jumbo from all grease and oil before. Maybe with rim brakes it is possible to "dry" the rim a little bit but with our disk brakes it isn't.

WHS: I don't think drying works, certainly not from wiping the water off the rim, it will always stay wet in my experience. If you brake so much that the rim gets warm/hot such as in a descent, then still I don't see it evaporating water on the rim quickly enough.

On a conventional bike I'd use the dynamo on the front wheel as the rear wheel will most likely be sprayed by the front wheel. On our tandem the distance is too big for the front wheel to really spray the rear wheel Funnily enough the wetness problems usually begin earlier when the wind comes from the left side where the dynamo is mounted. So it's really the rain itself that is blown onto the rim...

For our lighting I'm quite happy to have the Forumslader between dynamo and lamps as with its buffer it can bridge the power gap for quite some time when it is wet.

Conclusion: In my opinion it is the best solution you can have if a hub dynamo is not possible. It seems to be long lasting, has better bearings than conventional sidewall dynamos, runs more smoothly. Its electrical specs are somewhat unconventional which you should know and use the bulb correctly. But especially for a bike which has to run regularly under all conditions I would still do everything to make a hub dynamo possible. True wheels are a condition of course, but well, that's also a condition for a well running bike which is what we all want :-)

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