Tag Archives: cycling

Bicycle frame jigs (2/4)


The election of a frame fixture is not just a matter of budget. It is obvious that if you are going to produce few amateur frames a flat surface or a beam design jig will suit you. If you circulate large amounts of kind of the same type you should ponder over switching to something that ease the assembly and welding at the expense of less versatility.

Potential frame builders have the mistaken idea that the jig must be extremely accurate, built like a precision timepiece and yet possess immense strength for bending and holding the tubing sections in position for welding but in fact the base structure of the jig, sometimes called the backbone, bed, table, base table, face table or frame face can be almost any relative rigid structure. As long as the backbone is level in all directions the real precision and accuracy will come about through the fabrication of the fixtures that attach to this substructure (backbone) and then will be adjusted and secured to position and hold the tubing and parts in place during the fabrication of the frame.

A modified flat plate is enough for welding a bicycle frame

A modified flat plate is enough for welding a bicycle frame

For around 300$ you can start to think about it. In old Europe, for less than 400€ I’m struggling to find the right materials to accomplish my project. I guess this continent is not that cool anymore, isn´t it?

Don´t forget that choosing a frame jig is closely related to the welding technique. For example, brazed lugged construction requires the most from a jig. Full access to each joint is critical. When using lugs, most builders prefer to braze the complete frame in the jig unlike lugsless construction where jigs are used only to tack at 2 to 4 spots on each joint.

Silver brazing a lugged frame

Silver brazing a lugged frame

Consider most jigs offer limited access to one side of the frame. On top of that, if you are gas welding just forget about tackling the job on a cheap parallel beam jig for example. The heat coming from the torch will deform beam materials affecting our setup.

Nowadays TIG welding has become the superstar for joining the tubes of a frame. Both bicycle factories and custom workshops uses it on a daily basis. SMAW, GMAW, FCAW SAW are others common types of arc welding procedures but useless because of the thin-walled bicycles tubes.

Automated robot welder at Merida - Taiwan tacking a full suspension frame.

Automated TIG robot welder at Merida – Taiwan tacking a full suspension aluminium frame. Hand-welded frames are still far superior.

Besides TIG (that uses electricity), gas welding (oxyacetylene for example) is also possible, been the standard for 70 years. As good as it is, gas welding cannot compete with TIG. Anyway, oxy-fuel is still required for brazing, either fillet brazing (bronze weld) or brazing lugs (silver weld). These realiable and old-fashioned methods are still popular between cycle enthusiasts, that’s why you have to keep them in mind for your future jig plans.

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Checking the chain stays

So far: budget, quantity and welding procedures have been taken into account. The quality of a frame depends more on your miters, the time you spend fine tuning the geometry and your welds rather on an expensive jig, that can offer good accuracy of course. Amazing frames can be produced with simple tooling and great skills.

But there are also few considerations about the bicycles you are going to build and how you want to work in order to select the right jig:

  • What are the limitations in the seat tube area? Does the top of the seat tube have to be square cut? If it does, you can’t pre-shape the seat tube top, or use a seat lug with an internal ledge for a cut to length seat tube.

  • Does the seat tube holder arrangement pivot about the center of the BB shell? If so, you can’t build with the seat tube offset from the axis of the shell.

  • Can you easily build interrupted seat tube designs? These are common and unavoidable with rear suspension frames.

  • Are you in the mood of ISP? If you are, size the jig up accordingly or fabricate an extension.

  • How versatile is the rear axle arrangement? Most jigs come with one axle for only one spacing. You have to pay extra for any other spacings. 130mm road frames and 135mm mountain frames eclipse other preferences. How do they do 120 mm track spacing, or 126 mm old road spacing (for restoration, repairs, or using classic parts), or 145 mm if the jig also builds tandems, or the new MTB standard142xM12, or 165-170mm for fat bikes?

  • How do they handle the inevitable pull-in of the rear dropouts?

  • Do you want to build the frame from the BB up?

  • How do you build forks? A fork building feature could be integrated in a design. The rear dropout holder doubles as the front dropout holder in the Henry James Universal frame jig for example. A separate professional fork jig usually costs about $500. You don’t usually build forks? That is all the more reason to have one built in for when you do need one!

  • Can you build the occasional tandem on the jig? An attachment of some sort must be used, and you should not expect the adapted jig to be good for a tandem specialist.

  • How do you mount it? Because of the jig weight and bulk, most jigs require an expensive and complex mounting system that can increase your costs.

  • How portable is it? How much storage space does it need? TIG welding is not a straightforward skill. You might want to set up a frame in the jig, then single-handedly put it in your vehicle and take it to a full-time professional welding shop (an easy way to get perfect welds) for tacking while you wait. Even on a moveable stand, most jigs take up a lot of space.

A case of study: 29er inner tubes


Not long ago bike shops struggled to source specific 29er tubes (700x54mm). A widespread practise was to overinflate the classic 26″ size or 700x35c inners with the risk of sudden blow ups, decreased rolling eficiency and more punctures. Only some beefy tubes behaved well with no surprises for this purpose.

Foto 1 Nikki Gudex tubes

Tubes are within the most iconic bicycle components

Now the market is full of 29 inches tubes. For around £4-5, 6-7€ or 7-8$ you can afford good quality spares. Maxxis (Taiwan) and Schwalbe (Germany) are remarkable brands that produce tubes in many different sizes.

After damaging the original “unlabelled” tubes that came with my bike (probably made by CST, Vee or any other asian bulk manufacturer), I picked the Maxxis Welterweight (4,24€) and Schwalbe Extra Light (6,60€), both in online stores, to give them a go.

A thousand kilometers after testing the tubes with new tyres, the Maxxis tube has result in an amazing and absolute quality product. A bargain for the price (now over 5€).

Maxxis tubes are always true to the word of the company. Since the moment you open the box they meet the announced weight in the worst scenario, and sometimes a lot less.

The Welterweight is not a weight weenie product unlike the intended use of the Schwalbe Extra Light. Officially 205g. versus 140g. Note that the thickness of the butyl wall and tube dimensions will determine its final weight. The valve type, porosity and overall rubber quality have a negligible impact on it.

Foto 2

Maxxis tubes are made in Taiwan while Schwalbe units come from Indonesia

The good thing of the Maxxis is the fact that it is a real 29er inner tube. The Extra Light tube width doesn´t meet the requirements to fit securely a 2.4 tyre despite it is recommended for this size. It is clear when you put them close together that something is wrong in the Extra Light product. It looks like a 700x35c spare.

But what is even more shocking is reading the compatibility printed in the cardbox. It suits also 650b/584mm/27.5 wheels! Wouldn´t have been any wiser to make a compatible 650c/26″/559mm and 584mm tube while producing separately the specific 29er size? The discrepancy of the 29er size (622mm) with the 584mm standard is more than the 559mm measure has instead.

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A nonsense of tyre matching specifications that even claims 700b compatibility (635mm)

The result is that the Schwalbe model is not a proper 29er tube and nor a 650b one. You have to slightly overinflate them on 2.2 Continental Mountain King tyres for example. It’s tricky to slide equally the tube inside the tyre bulging it on many ocassions unless you use an air compressor.

What’s more I got quite a few flats. None with the Maxxis. I reckon even the rolling eficiency is compromised with such a tight fitting. A hassle.

The final blow came when checking the weights. The taiwaneses are only 40 grams on average heavier than the germans, instead of the expected 65g.

Average weights

Average weights. Less than 40 grams average discrepancy between models

Cheaper, easier installation, more reliable and keeping the pressure for longer my vote is on the Welterweights. It’s great that Maxxis produces almost each single size of bicycle inner tubes. Meanwhile the design of the Extra Light tube is all messed up.

Park Tool pin spanners and three newsworthy repairs you can do with them


One of my favorite bicycle wrenches are Park Tool pin/peg spanners. It’s because they are handy, strong, cheap and simple tools but also because of the different coloured grips that break the monotony of any tool wall display.

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Spanners are made of hardened carbon steel to ensure long life while the handle is vinyl coated

My own experience tells me they are not on a daily basis tools anymore, but still esential for any all-round workshop that services freewheels or old fashioned bottom brackets for example.

The green handled SPA-1 fits the adjusting cup on many old three pieces cranksets. The pin ends are round with a diameter of 2.9mm.

The most popular repair you can tackle is a cup and cone type bottom bracket service.

Mural Park Tool SPA-1

Wherever there are two holes with the right size the Park Tool hanger cup pin spanner will allow you to do different repairs. Adjust the tension of the chain by turning the eccentric BB, removing a dustcup and so on

On the other hand, the SPA-2 red spanner has 2.3mm pin diameter. Due to its smaller size fits better a wider range of hole widths. It releases retaining rings on Shimano and Campagnolo crank bolts and the adjusting cone on most freewheel clusters.

A very interesting repair suitable with this tool is the removal of certain type of non-serviceable freewheels that don´t have an extraction tool option. A freewheel destructive removal method will require this spanner to get rid of the lockring.

The Park Tool cluster cone pin spanner is ideal for several repairs where a lockring needs to be removed, on self extracting or one-key release crank bolt systems or even if you need to fit/extract the guides of the BB facing tool inside the frame

The Park Tool cluster cone pin spanner is ideal for several repairs where a lockring needs to be removed, on self extracting or one-key release crank bolt systems or even if you need to fit/extract the guides of the BB facing tool inside the frame

The third and last peg spanner I own is the discontinued yellow SPA-4. It has a flat section designed to uncrew the adjusting cone of one-piece cranks. This is virtually the only repair you can do with this tool, the service of entry level cranksets on BMX’s and department store bikes.

The tool engages two notches of the adjustable left bearing cone. Rare cup and lockring cartridges BB's can also be serviced with the yellow spanner. The cup is run up to the bearings and then the lockring is secured. Note there is no bearing adjustment in this system

The tool engages two notches of the adjustable left bearing cone (2nd pic). Rare cup and lockring cartridges BB’s can also be serviced with the yellow spanner (3rd pic). The cup is run up to the bearings and then the lockring is secured. Note there is no bearing adjustment in this system. Nowadays the best use I found for it was while wrapping the handlebar of a road bike (4th pic)

At this point you might wonder what happens with the Park Tool reference SPA-3. Does it exist? Well, it does. But I haven´t seen one so far. It took me a lot of time to find a presentable picture of this tool and some information.

Blue and black peg spanners are top-rarity Park tools. SPA-3 has the ends facing one to each other. I don´t know the intended use for both tools. It seems the blue one can be used for adjusting old french bicycles headsets and the black for extracting crank bolts dust cups/retaining rings

Blue and black spanners are top-rarity Park tools. SPA-3 has the ends facing one to each other. I don´t know the intended use for both tools. It seems the blue one can be used for adjusting old french bicycles headsets and the black for extracting crank bolts dust cups/retaining rings

Meanwhile SPA-6 uses replaceable pins of approximately 2.2mm in diameter. The distance between the pins is adjustable, allowing use on virtually all hanger cups using pin holes. I have to say I do prefer fixed pegs as they are faster and more comfortable to use.

I have never faced a situation where you need to use the pin spanner wrench with such a distance between pins on a bicycle as in picture 2. Pin holes are likely to be close one to each other and thus more convenient a regular pin/peg spanner

I have never faced a situation where you need to use the pin spanner wrench with such a distance between pins on a bicycle as in picture 2. Pin holes are likely to be close one to each other and thus more convenient a regular pin/peg spanner

Thinking on removing your front derailleur?


Everytime I come across with this question on a bike forum my thoughts automatically go back to the 2003 Tour de France Prologue.

On that day, the scottish David Millar lost the opportunity to win the initial time-trial for less than a second due to his chain that came off the front ring.

News footage from the French TV shows how brave is Millar placing the chain back with his fingers upon arrival. A delicate operation while you’re riding over 30 mph.

This information points at the missing front derailleur as the reason of the problem.

dvcvxcv

David Millar, 2003 Tour de France Prologue, Paris

@ http://www.cyclingfans.com

Yesterday’s chain failure wasn’t the first time that David Millar has experienced a chain problem at a critical time in a Grand Tour. During the 2003 Tour de France 6.5km prologue (photo above), Millar’s chain slipped off as he approached the finish line, costing him the stage win. An angry Millar blamed his directeur sportif for the lack of a front derailleur, causing the chain to slip. Millar finished the prologue second to Bradley McGee by just 8 hundredths of a second.
-Pete Geyer

It’s hard to believe that a bike mechanic involved in such a race like the Tour de France, world class riders and equipment (not the case with Decathlon bikes though :roll:), decided to remove the front mech, because Millar was committed to use a single chainring setup, without fitting a chain stopper on its place.

I can only blame ignorance to be mother of imprudence. Front derailleurs allow to switch from chainwheels, and what is as important: stop the chain from jumping off. On bumpy stone paved roads (pavée) and a NOT enough rear mech to lock up the chain tension while it is working crossed along the cogs we can only predict the chain is going to fall off sooner than later. Even on flat surfaces it will slip off.

Whether if you want to convert your MTB to singlespeed or 1x type transmission, bear in mind you will need a device to prevent the chain from coming off. It can be a double bashguard, a chainkeeper/chainguide/chain stopper or a combination of both.

Posh Paul chain keeper

Posh Paul chain keeper

Many people that are simplifying old vintage road bikes should do the same for fixie/single speed purposes.

All these advises (and devices) are taken into account considering we are talking about pure vertical dropout frames with no other methods to take up the slack in the chain, such us: eccentric BB/hubs, sliding dropouts, and so on, representing the vast majority of frames.

There are only a couple of exceptions that freaks will proudly point out. SRAM XX1 single chainring gruppo and high chain tensioners on singlespeed bikes where the chain works straight! (Bromptons for example).

Even though, I’ve experienced chains coming off in my bike that uses a perfect aligned chain on a Rohloff hub and the extremely high tension provided by the DH tensioner. XX1 failures are even more common, and have been reported frequently despite engineers taking the piss with the deep profile teeth design of the XX1 chainring encouraging not to use a chainguide. I would like to recall that Hermida lost the podium in the last Olympics because of the bloody stupid tendency on bikers to remove the front derailleur and the “cojonazos” of his team fitting new-unproven parts they’d just received.

Hermida’s team underrated the importance of the chainguide that is mandatory on top of the XX1 crankset if you do not install a Type 2 SRAM rear mech. The SRAM XX1 provides extra tension thanks to a roller clutch

If you’re switching to single speed or whatever 1x setup is in your mind, fit a chainguard. You’re not likely to lose a gold medal or the yellow jersey but you teeth instead :mrgreen:. Remember how bad the Cofidis bicycle mechanic should have felt that night after the first stage of the Tour de France: “somebody shoot me”.

Brompton inner tubes


As we’ve seen in previous entries nothing in the Brompton universe is straightforward. Inner tubes compatibility are ample proof of this.

If you eventually need to replace them, bear in mind that a regular 16″ children bike tube will not fit. This is the one you are likely to find in a rush in a bike shop and for your surprise too wide. You’ll notice is very tricky when sliding it inside the tyre. These inners will cover ranges between 1.75 to 2.125 inches (45-50mm).

On the other hand, Bromptons are equipped with up to 1.37″ (1 3/8″, 35mm) inches width tyres. Schwalbe makes good quality spares and are the ones I recommend.

Compatible inner tubes suit from 28 to 37 mm width tyres

Compatible inner tubes must suit 28 to 37 mm width tyres

Most of the Brompton compatible tubes fit tyres from 340 to 355 mm bead seat and widths from 28 to 37 mm approximately.

16 inches inner tubes are very light :mrgreen:

16″ inner tubes are small and as a result very light :mrgreen:

Bromtpon Eazy Wheels


Replacing the factory wheels was the first repair that came to my mind when I got the Brompty. Although I did it long ago, I have saved it for last within this saga of Brompton repairs because the result is not satisfactory. I would say work in progress 🙂

Factory rollers vs. Eazy Wheels

Factory rollers vs. Eazy Wheels

By installing the Eazy Wheels you have the added advantage of being able to pull the bicycle along on the ground. Stardard wheels are just simply a shame and won´t work.

I love the idea of the versatility of a Brompton

I love the idea of the versatility of a Brompton

Good, I have no more to carry mine everytime I go walking with it when commuting, I thought. But the reality is that your bike needs also a rear carrier, or Brompton mudguard at least, to support parked mode and wheel it along. Otherwise the Eazy wheels by themselves won´t make any difference. I can’t believe I didn’t figure it out until I put them on. Well, at work I never needed to pull/push the bike around :mrgreen: .

Eazy_wheels_4_close_up

Tyred rollers with industrial bearings can also be fitted to the rear rack

A rubber bung, fitted to the bottom of the seat post, can be used as a brake to prevent unwanted rolling.

Full kit

Eazy Wheels full kit with rubber thingy

My Brompton does not have a rear mudguard that will add the extra wheel for stability, or what it could be even better, a rear rack that comes equipped with two wheels improving the handling when it is half-folded.

IMG_4666

Bikes with no mudguards/rack but Eazy Wheels installed, are as stupid as mine looks in the picture

Not everybody need to enable this function. That is the reason it is offered as an option when placing your order. In that case you will have to pay on top 20 quid for the better quality wheels, and another 50 quid for the pricey mudguards or 100 quid for the Version R of the bike (mudguards & rack).

The installation of the wheels is so straightforward… nothing to say about it. What a drag!

Brompton rear frame clip for older models


One of the most frustating things in pre-2007 models is the lack of a mechanism that stops the rear triangle from folding when you lift the bike up.

IMG_4590

Got it from Brilliantbikes.co.uk that delivered overseas some Brompton parts faster than any spanish dealer

In order to update my 1999 Brompton the retro fit kit is needed as it comes with an 8 mm seat clamp bolt. If you are using already a 6mm bolt there is a much cheaper kit for sale without the clamp lever, £9 instead of £23,75

Packaging content

Complete retrofit kit

The installation process consists on two steps.

First you will have to modify the rubber damper discarding the conical buffer disc (aka suspension block bolt) for the one that have a recess to engage the latch lever.

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Suspension block bolt disc to be replaced

IMG_4605

Appearance of the new disc bolt. This time is inserted thru the elastomer from the other side

A plastic shim washer (SW), a stepped nylon washer (C) and a nut (N+BW) is necessary to hold the block (SB) from behind when fitting the new buffer disc bolt (BD) as shown in the picture (Fig. QR10). Grease the bolt not to have funny noises. After installing the bolt make sure the small hole is in the bottom position and thus the two tiny lines marked in the disc facing up.

Follow the steps shown int he picture

Follow the steps shown in the Fig. QR10

Secondly replace and discard the old quick release bolt. Three parts will be assembled inside the seat clamp band (SCB) of the bike in the order and orientation shown in Fig. QR05: a hollow stepped cylinder (S), the metal lever (L) and the spring (T). Assemble the parts sliding them with the quick release in angle.

New seat clamp and parts inside the frame band

New seat clamp and parts inside the frame band

Tighten the seat clamp by using a nut and the required metal tabbed washer (SCW) for M8 bolts. Fig. QR06

IMG_4607

For post-2007 bikes use the existing flat washer instead (M6W).

At this time, the installation is fully functional but not complete. The kit does comes however with an ergonomic black handle (HDL) that protrudes much longer than just the metal lever. Secure it to the lever with the self-tapping screw (STS). Fig. QR 07

IMG_4602

My bike now updated :mrgreen:

And this is it.

For further instructions you will find helpful the video from the official Brompton Channel on Youtube. Hard to find better technical advise and spoken english. Well done.