Velobrico Tinkering: Dynamo lights

Though I have absolutely no experience with dynamos, nor any real idea how they work, last Sunday I decided to tackle the non-functioning rear light from the Tigra ladies’ bike.

This bike has a dynamo installed, even though it is not such an old machine. I was recently told that in Germany it is illegal to ride a bike with battery powered lights. I’m not sure if that is true, (German cycling laws here…) as it does sound pretty nonsensical, though I’m pretty certain you are allowed to ride in Switzerland with whatever lights you want.

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Once I figured out how to engage the dynamo so it would work from tyre rotation (this seriously took me a few days of prodding and pulling to figure out), the front light functioned fine but the rear refused to shine.

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First, I removed the plastic housing and checked the bulb. Filament looked ok. Checked continuity with the multi-meter, all good. Screwed it back in. Crossed my fingers. Nothing.

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Then I had a look at the wiring. The dynamo has two wires coming out of it, one for the front light, another for the rear. Not sure how this can make a complete circuit, but I guess that’s not necessary for DC power. The bulb socket seems to be connected to the mudguard itself, so presumably being grounded is sufficient for a DC circuit. My lack of electrical knowledge is by now apparent.

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The wire hanging out of the bottom of the dynamo seemed loosely connected, but I noticed a spring-loaded connector in the bottom which holds it in place just fine. The wires head into the rear mudguard, then follow a crimp in the side until exiting through a hole in the rear, into the light fitting. This wire is then connected to another metal clip, basically wedged into a bent flap, held in place only by the “springy-ness” of the metal itself…

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The wire going into the rear light fitting looked a bit corroded, so I took it out, sprayed some white vinegar on it (helpful for oxidation), dried it, rubbed it with some steel wool. The copper colour shone nicely, so I “re-twizzled” the strands, rubbed the metal clip with the steel wool and reinserted the wire. Crossed my fingers. Tested it it again. Nothing.

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Then I removed the bulb and filed a tiny bit off the bottom to ensure good contact. No joy.

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I now removed the wires from the dynamo and did the vinegar, steel wool and “twizzling”. Crossed fingers. Tested again. Nothing.

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Not to be deterred, I removed the bulb again, and found bits of spider eggs or some other insect leftovers. Blew those out. Another round of vinegar, steel wool, scraped a bit with a screwdriver, dried it, sprayed a bit of WD40 on it.

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While I was at it, I sprayed a bit of WD40 on the metal clip and the wires at the dynamo. A bit of WD40 often works wonders.

Screwed the bulb back in. Crossed my fingers. And it worked!

A well earned cup of tea followed. If only every Sunday were so productive!

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Are disc brakes really dangerous??

It’s been a while that disc brakes have been seemingly considered dangerous, and are occasionally permitted and banned in professional road bike races.

Personally, I never really understood the cause for concern, and RJ the Bike Guy’s latest video does a really neat job of clearing this up.

Check it out.

Velobrico Workshop: Removable valve stem??

I guess you have heard of a removable valve core, but what about an entire stem?

I recently added another abandoned bike to the workshop and while tending to the flat tire I noticed the inner tube held air, but that the valve stem came out of the inner tube if fiddled with (with an explosive release of tyre pressure too!).

While I assume this is a fault in the inner tube, on closer inspection, it doesn’t look like anything has torn or failed. The inner tube has two rubber joints, the second of which seems to hold the stem base. The upper seems just to hold it straight.

I have replaced the inner tube with a new one from Schwalbe, but can a removable valve stem really be a thing? Never seen this before.

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Velobrico Workshop: BMC Fourstroke FS04 (update 1)

I recently bought a tired BMC Fourstroke FS04 mountain bike, which had seen plenty of action and not enough maintenance.

I saw potential (or as much as anyone can from a couple of mobile phone photos…) and brought it home to breathe new life into it.

Sometimes you get lucky and there’s not much wrong with a bike. And sometimes there’s some skeletons in the closet, though finding them can also be fun.

I’m always itching to give new project bikes a good wash. Often so quickly that I don’t get any “before” photos… I’ve got to learn some patience!

Washing a bike gives you the chance to look at it closely and spot things you previously overlooked. The BMC was superficially lightly dirty, but chain, chainrings, cassette and jockey wheels were well overdue a de-griming. Is half of restoration actually just cleaning?

Now funky shaped frames are great, but who wants to clean their bike with a toothbrush after every muddy ride?

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Overall, the bike is sound, frame is good, components all there. There’s a few dings, but no visible evidence of crash damage – especially important for aluminium frames. Brakes are ok (if a bit spongey), rotors are true, headset is fine, BB has no wobble.

The front hub was loose, so I stripped and repacked it with new grease. Bearings were fine, races good. This was sorted very quickly and only minor adjustment was needed to the disc brake caliper to avoid rubbing against one pad after tightening the cones.

The rims are slightly out of true. Usually I use rim brake pads as a makeshift truing stand, to see minor wobbles and where to adjust spoke tension. Truing wheels on a bike with disc brakes will be more tricky, so I’ll leave that for later…

The biggest fault the seller mentioned was the twisted derailleur and chain. The derailleur looked ok, so I removed the hanger with the intention of replacing it with a spare from the Steppenwolf, but found it was a slightly different shape and wouldn’t fit.

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A trip to the bike shop later, the mechanic told me he didn’t have any spare hangers in this shape, but he could bash it straight for me. Back home I reinstalled it, stripped the derailleur, serviced the jockey wheels, reinstalled the derailleur and chain (minus one link), and wouldn’t you know it – it worked perfectly! 👍

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If you read my earlier post, you may recall the seller mentioned his local bike shop quoted almost twice what I paid for the whole bike to sort this out (presumably replacing derailleur and hanger).

Turns out that was pretty poor advice as I sorted it in two hours (including an hour’s walk to the bike shop and back with the kids), at zero cost (a contribution to the tip jar was all they would accept – but I also bought some cleats). Some adjustment needed for perfect indexing, but 80% there. Result!!

Next I adjusted the handlebar position, flipped the riser stem down and adjusted brake and shift lever positions, taking the opportunity to lube/grease all the screws that hadn’t been loosened in years.

While poking around I found a couple of other issues: a sawn off seat post (kids, just don’t do it…!), a loose pedal spindle and some broken chainring teeth, but overall this is turning out to be a nice little restoration project.

Watch this space for the next steps!

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A saddle and a lock, at the same time…

This is a pretty neat idea. Saves lugging a lock/chain around, and avoids scratching your paint while you’re riding.

I do wonder how heavy it is, but in fairness, on a town bike it probably won’t make much difference to “performance” or centre of gravity.

PS. I unfortunately have not received one to test, but if the right people are reading this, you know what to do! =)

Velobrico Workshop: BMC Fourstroke FS04

Summer is a time for holidays, taking a break, recharging the batteries, and filling idle moments scanning second hand bicycle adverts…

The latest addition to the stable is a well loved (i.e. ridden hard and put away wet…) BMC Fourstroke FS04 (2006?) fully suspended XC mountain bike. 

As you can tell from the ad photo, it has seen better days and needs some TLC, but fundamentally it’s solid, with an interesting frame design, sound pedigree and some nice components.

I picked this one up very cheap, for less than the cost of a second hand front suspension fork (which I’m on the look-out for the Steppenwolf Tundra). 

Here in Switzerland (and maybe also where you live), servicing and repair costs are relatively high. An overhaul and replacing a couple of parts can easily run into hundreds of Swiss Francs, which puts people off repairing things when they break.
In this case, the previous owner had bent the derailleur hanger, snapped the chain and twisted the rear derailleur (miraculously without breaking a spoke…), and was quoted a relatively high sum to repair by his local bike shop. So he put the bike up for sale, to fund a replacement.

As servicing costs are high, this also puts many buyers off such a bike. Which is great news for folks like me who enjoy a challenge, and finding diamonds in the rough!

BMC is now a well known and respected bike manufacturer, with successful racing teams in road and MTB disciplines, but I didn’t know that they are a relatively young brand. 

Apparently they began as a Swiss distributor for Raleigh bicycles in the mid 90s (after Raleigh’s heyday…), then branched out into framebuilding when the distribution contract was terminated. What a great outcome that they’re now such a highly recognised brand on their own merits.

Incidentally, while aimlessly browsing the ads, I came across another ad for the same bike in fully working order, for over four times what I paid for this one.

For once, I managed to take some photos of the bike in original as-bought condition (usually I’m so excited when I get something new that it immediately gets a wash and tinkering starts as soon as I get it home…), so here they are below.

First glance suggests that the bike is mostly sound, and other than replacing a derailleur hanger (and possibly the rear derailleur), all it needs is a bit of an overhaul (hub servicing, brake bleeding, new chain, pedal adjustment etc.). Will be interesting to see if the derailleur is reuseable…

Watch this space!

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Velobrico Workshop: Motobecane Eclair (1986) update 

A couple of weeks back I posted about the latest addition to the Velobrico pile of bicycles. A mysterious Motobecane Eclair. Mysterious mostly becuase I couldn’t find out much information about the bike.

Since then, I found that Motobecane went bankrupt in 1983. The remaining assets were purchased by multiple parties, including Yamaha, and rebranded MBK.

I found a French Motobecane brochure from 1986, but no Eclair. All brochures I could find from after this date were for mountain bikes or BMXs, under the MBK badge.

So still no trace of the Eclair (which from looking at the components, should date from about 1986).

Then a breakthrough clue.

Through a Google image search I found some photos of a couple of Motobecane Eclairs. All had been repurposed as fixies or otherwise lightly modified, but were always in the same colour scheme and interestingly also in the same large frame size.

And all located in Germany….

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The other clue as to provenance came from a sticker on the down tube with ZEG written on it. This stands for “Zweirad Einkauf Gemeinschaft“, which I understand to be a bulk purchasing cooperative.

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So I’m guessing when MBK went bankrupt, they sold their remaining inventory, along with exclusive licences to sell Motobecane branded bikes, in certain national markets.

So Germany got the Eclair, and similar variants maybe appeared in other countries. I wonder if Spain got the Profiterole, and Italy the Paris-Brest (yes, it is the name of a patisserie as well as a bike race).

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Has anyone spotted something similar? Just this morning I saw a MBK (not Motobecane) Mirage with a similar looking frame (internal cable routing and same seatpost clamp under the rear stays) in Zurich.

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The Eclair needed quite a bit of tweaking before it could be safely ridden, but eventually I got it out the door and went for a fairly long 65km test ride.

Prior to the test ride I noticed the rear wheel was untrue and had very loose spokes. I tightened them, trued the wheel, and after a few small test runs they seemed to loosen again. So further tightened them, same story. Then I switched out the spoke nipples on the loosened spokes.

This was sufficient for it to survive the test ride, but the spokes definitely loosened again by the end of the ride. Given I can’t remove the spokes without removing the freewheel and can’t do that without a tool that doesn’t disintegrate on the first use, it seems easier to just switch out the rear wheel with a new one. I can’t really imagine why spoke threads could be stripped (which seems the only explanation for the continual loss of spoke tension). Does anyone have experience with that?

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The test ride was otherwise very positive. The brakes are good, though not as powerful as modern equivalents. The mudguards kept me clean =). I was glad not to have to use the lights as the dynamo seems to add 5kgs to the bike when in use…

The handlebar position gave me pins and needles. I get that on some of my bikes but not on others, and have never figured out exactly why that is. Reach or top tube length?

The VP Components pedals were a pleasant surprise, well built, comfortable and suitable for both regular shoes or MTB cleats. Apparently the low cost B’Twin pedals sold in Decathlon are made by VP Components, so buy with confidence.

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The bar tape has stretched apart in the usual spot, on the tops behind the brake levers.

Basically, the downward pressure applied by one’s hands spreads the wrap open over time. This is very common and is so easily avoided by “reverse wrapping”, where you rotate the tape outward from the top (right bar clockwise, left bar counter-clockwise). It’s a neat technique, and worth trying if you haven’t done so already.

I averaged 29 km/hr for first 18kms of my ride (until my phone died) and never did the bike feel unstable. Not bad for a purpose-confused hybrid/aero/tourer/commuter frame!

While the test ride was successful, and this frame offers a good ride, it is just far too big for me.

The current saddle doesn’t look good, so I intend to swap that onto another bike and replace it with a more comfortable one, more suited to a hybrid bike and less “race-y”.

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For me this frame makes for a better a road racer than a commuter, mainly because I have never been a fan of commuting on drop-handlebar bikes. I find the riding position awkward for stop-start riding from traffic light to traffic light, and the skinny tyres poorly suited to cobble stones and tram tracks! But as a weekend racer for a taller cyclist. This bike would be great.

As a final thought, while browsing the Motobecane catalogues, I came across this most fetching photo from 1984.

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I just couldn’t wear shorts that… short.

Maybe that’s why I’m not a fan of Motobecanes?

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