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Archive for the 'Tech Notes' Category

Blazing Saddles.

Wednesday, June 27th, 2007

Difference in philosophy. Bigger the better and Smaller the better.

If you are happy with the original saddle comes with your A-bike, you are blessed. Well, I’m not. The day, I went for 30mins ride for the first time with A-bike, became the last day I sat on the tiny saddle. It knocked my bottom so good, I couldn’t properly sit on any sort of chair for two days afterwards. This made me to get my Cane Creek Thudbuster LT, but let’s look at more generic saddle upgrade this time.

My girlfriend asked me to change her A-bike saddle to more comfortable one. she is a casual A-bike rider and mostly each riding time wouldn’t exceed 10mins. According to her, the saddle was not very comfortable, but not too uncomfortable either for her use. In fact, she never strongly complain about the saddle until we went to Lock Ness Trip, where we rode reasonably long distance.

The clamp and the rail.

A-bike’s original saddle and seatpost are not in any standardised format, which is used by conventional bicycle. If we want maximum flexibility with saddle, it’s best to go for a saddle with ‘two rail system’ and seatpost with ‘seat-rail clamp’ and the clamp better be ‘micro-adjustable’ to get the comfortable saddle angle and position.

The A-bike’s seatpost size is 25.0mm diameter according to official data, but it is actually around 25.2mm to 25.4mm. Since the seat-tube (=where seatpost goes in) is made of thin metal tube, a little difference in diameter can be forgiven by tightening seatpost clamp (=the silver alminium clamp on top of the seat-tube), but anything more than 25.4mm would not even goes into the seat-tube. So, I would say seatpost diameters compatible to A-bike are: 25.0mm, 25.2mm, and 25.4mm. 25.4mm is the most common size among these.

I bought a saddle and a seatpost off eBay UK. The saddle was Velo Plush branded soft comfort saddle with center hole (£8 including postage) , and the seatpost was 25.4mm unnamed black colour seatpost (£10 include postage). Then I found I made a mistake. They didn’t fit together!!

Too bad he was 9mm. I liked him, you know?

The reason was simple. There are two different size for seat-rail. one is 8mm and the other is 9mm. Most of saddles (including the velo) in the market uses 8mm, whereas 9mm is used by some BMX saddle system. Yap, the seatpost was for 9mm and the eBay listing clearly stated “for BMX”. Well, it was a good lesson.

I bought 8mm seatpost again from eBay for less than £10. This time was Kalloy alminium seatpost 25.4mm, the common product we can find it on eBay all the time. As above picture shows, it did fit to the velo saddle nicely…. but my trouble continued. It was fat…

Look at how much dust I had to bite for doing this ‘supporsed to be a simple’ job. haha.

It seems that cheap seatpost often miss its supporsed size. This is why these are cheap. My kalloy was slightly more than 25.4mm. I could put the seatpost into A-bike’s seat-tube, but it was very tight and it was obvious once it goes in, it would never come out again. It needed a bit of sanding with sanding paper to slim it down.

Sanding process was straightfoward. Wrap a bit of sanding paper around the seatpost and rub, then sometimes wash the paper and the post with water. (This should prevent heating up and clogging of the paper.) Phew, it was tiresome, but if I could save £20 or so by going through this, it’s not too bad, is it?

Tube Cutter in action.

Can you see what happened to the cut section?

The kalloy seatpost got right size, but this isn’t the end of the story. I still had to cut the length of the seatpost. My girlfriend is about 155cm (5foot 2″), and she demanded the seat to be positioned as low as possible.So, I had to cut the seatpost shorter.

The lowest position with conventional saddle has to be higher than the one with A-bike’s original saddle. It is because conventional saddles has ‘nose’ and the point this meets A-bike’s top frame is the lowest it could go. (see pics) If we want saddle to go even lower, we have to get one of those ‘noseless saddle’.

Cutting seatpost can be done simply with metalwork saw, or tube cutter, which I used this time. I bought a tube cutter (for tube up to 30mm) for £8 from UK’s big DIY store, B&Q. Cutting was easy. Just clamp on the seatpost with the tube cutter, and rotate it as tightening the black screw at the bottom little by little. However, the thickness of the seatpost and the capability of the tube cutter probably didn’t match — A strange bump appeared around the cut section. Yes. It grew fat once again!! This time I used mini rotary kit to grind down the grown edge. I guess this extra work could be avoided if I’ve used the cutter to only mark and used metalwork saw for the rest.

I refer this A-bike as ‘Hip-Heavy’. My girl isn’t happy with the nickname though.

Anyway, as you can see in these pics, it’s all set and done!! Don’t you think the velo saddle goes well with A-bike?

The ‘Velo plush’ name is used by several different product actually. They have more slim and sporty looking one named same and also in same colouring (other colour also available) too. (pic below.)

My Velo Plush is comfort model and weight about 520g. The Kalloy seatpost weight about 200g after cutting it down, so it makes 720g in total. The A-bike original seat assy is only 330g, so it’s good 390g weight gain. Adding to that, the shape of the conventional saddle doesn’t fit with A-bike’s folding mechanism and spoiles its portability. This is a shame.

Having said that, this saddle upgrade does gain A-bike’s mobility so much by providing comfort to its rider. In my opinion, this is worth sacrificing size and weight for. A-bike is smaller and lighter than any other folding bike even after the modification in the end of the day. I also tried her A-bike with the new saddle for short while. Obviously it was too low for me, but besides that I couldn’t feel any bump of the street at all! It feels even smoother than my Thudbuster. haha. The velo saddle might not be a looker, but this is the power of puffy comfort saddle.

If my words aren’t enough to convince you, hear what the girl said.

“I cannot believe your reaction was so calm when you changed your saddle! This is almost like a different world!! Now I feel like I’m riding a conventional leisure bike. It’s sooo comfortable!!!! Ah, I won’t go back to the tiny saddle anymore.”

Hear that? It’s good.

I heard the stories of A-bike owners gave up A-bike because of their bottom compatibility issue with the saddle. Before you give up, try changing the saddle and think again! It’s not difficult to do! (well, I just went to bothersome path by accident, so don’t take my case as a model.)

There are many other ways of make your A-bike ride comfy. We shall feature them some other time.

Check out saddle/seatpost related topics in A-bike Central Forum for more info!


Spiral Jetty.

Saturday, June 23rd, 2007

My A-bike’s rear wheel has a strange spiral scrape on its right hand side. It was a minor scratch at first, but it seemed growing bigger day by day. It was an unsolved mystery until this morning.

A topic talking about loose chain inspired me to do a little checkout on secondary (lower) chain when I was pumping tyres (I do pump A-bike’s tyre every weekend). Then I found the tyre scraper. It was the secondary chain!! To be more precise, it was chain-connecter-pins!!

The chain has gotten loose to compare to its first state, but it’s not loose enough to set chain tensioner to “H”. I’m not sure why this is happening. Could it be my rear tyre was bigger than usual? No, I don’t think so. Maybe the chain I got was a rough one? mmm… Since A-bike’s gear box has a very simple fool proof (well, more or less) structure, it seems more puzzling. Anyway, the chain pins gave the initial bite on tyre for sure.

Current state of the scraped tyre suggests I’d better get a new tyre and maybe another #25 chain just in case. I shall e-mail Mayhem to seek some advice on this. They may know what’s going on here.

I setup a new topic on this, so if you have same experience, please share it there!

Going button head.

Thursday, June 7th, 2007

Stainless steel Button head bolts and Spring washers from eBay.

Ever since I installed clipless pedals to my A-bike, my trousers often gets catched by A-bike’s top-tube bolts around my thighs. It wasn’t anything fatal — Each catch only lasts for just a fiction of a second. However, it was utterly annoying!!

One of the causes for this nuisance is A-bike’s wide top-tube. While conventional bicycle (including MTB) has less than 5cm width for their top-tube (including outer cable), A-bike’s top-tube width is vast 7cm+!! The socket head bolts sticking out from the side of the tube definitely contributes here.

If you pay attention to your pedaling next time you ride A-bike, you may notice either the bolts scratching your thighs or your feet are on rather outer side of the pedals to avoid the bolts. As long as we use normal pedals, our feet are free, so the wide top-tube isn’t much of a problem. That’s why I never realised this until I went clipless.

Clipless pedals force our feet to be positioned right in the center of the pedals all the time. Thus, it’s more difficult for our thigh to pull out evasive maneuvre.

Anyway, I didn’t want to give up my Eggbeater pedals over this, so I replaced some of the top-tube bolts (edgy socket head), which interfere with my thigh movement, to smoother button head bolts .

Well, I replaced only 3 of 4 bolts so far…. I cannot remove the last one!! I’ve been applying Acetone to the stiff bit, hoping it would break the seal. Soaking the bit in acetone for overnight does extract some brown stuff (grease? Threadlock?), but the bolt is still as hard as a rock. Oh, A-bike factory, what have you done to it!!
I still seek advice on this at this topic in the forum.

At the moment, even though the mod isn’t completed, minimized top-tube width and smoothness of the button head works great. 95% less chance of my thighs get catched!!
(the 5% is the remaining bolt of course.)

The replacement parts for this modification are;

4 x “M5″ size “0.8” pitch button head bolts (2 x 16mm length and 2 x 8mm length)
4 x “M5″ size Spring washers
4 x “M5″ large washers (ext. diameter 15mm)

(I chose rust resistant stainless steel.)
*’Bolts’ are sometimes labeled as ‘Machine screws’ in some shops.
*10mm length M5 bolt canbe used instead of 8mm M5.
*Be careful not to mistake ‘large washer’ as ‘penny washer’. They are different.

Please note, button head bolts have somewhat weaker tightning strength than the socket head bolts of the same size, due to the size of the hex-key they use and the depth of their socket. I would not recommend to this bolt replacement mod. for other part of A-bike at the moment.

(Left) New button head bolt and A-bike original socket head bolt. (Right) Short bolt assembly for top-tube/seat-tube joint.

While A-bike original bolts are for 4mm Hex-key, button head bolts need smaller 3mm hex-key.

The screw assy. here is glued, but still manageable.

(Left) My A-bike with 3 bolts replaced on the left and normal A-bike on the right.
(Right) Soaking in acetone… please! get unscrewed!!

Making impossible possible.

Sunday, May 27th, 2007

As some of you already noticed, Sinclair A-bike’s seatpost clamp screw is one of the most troublesome screws of all. The clamp is a quick release all right, but it isn’t a quick adjuster by any means — —- In order to gain access to the screw, we need to unscrew another screw! If we want to tighten or loosen the seatpost clamp on the street… this is… complicated. Some solutions were posted here in A-bike Central Forum in last year. Now, here comes another method.

Bikehut ‘Ball ended hex key set’ £9.99 from Halfords. This Hex key (a.k.a. Allen key) set canbe gripped as the photo below, clever.

But No, that’s not the point. What really clever about this tool is its ‘ball ended’ part.

This allows us to turn the anoying screw from angle position without removing the other screw!!!

This ‘ball-ended hex key’ is not a rare tool, so you should be able to find it in decent tool ( or Automobile tool) retailer near you and of course also on the web. When you use this tool to adjust the seatpost clamp, please note the following points.

1. Use 3mm hex key.
2. You turn the screw by ‘swinging the hex key’, and not by ‘rotating hex key’s axis’
3. Adjust the screw with the quick release lever ‘loosen (opened)’.

The price and the quality of this tool vary, so make your choice as you please. For example, Halfords also offers similar ball-ended hex key set in their superior professional range (car-tool section) and it costs £19.99. Then somewhere like Maplin sells ball-ended 7-Piece Allen Key Set for just £2.99!!

You can also refer this topic on tools for A-bike maintenance.

A small tip for carrying the A-bike

Saturday, April 21st, 2007

Have you ever got this experience?

When you carry your fully folded A-bike by grasping the handlebar stem while you are walking (or running to catch a bus), the crank arms and handle bars of the bike rotate and go sideways. This may cause inconvenience and affect the portability of the bike itself. Even worse, the turning crank arms and pedals may hit the saddle and cause damage on it.
Photo of the tip for carrying the A-bike Photo of the tip for carrying the A-bike #1

I have a small tip here for you to slove the problem.
No rope, no string, no strap, no wire, no bungee chord nor hook is needed.

After you have folded your A-bike, just prop a pedal against the end of the folded handle bar on the same side and prop the other pedal against the back of the saddle.
Photo of the tip for carrying the A-bike #3 Photo of the tip for carrying the A-bike #4

See? The problem is sloved now!
Photo of the tip for carrying the A-bike #5 Photo of the tip for carrying the A-bike #6

The bike is now more portable and even more compact now.

This method also works perfectly when you put your A-bike inside the storage bag.

Self maintenance tips : Noise Reduction

Wednesday, April 4th, 2007

1. In your riding time without any adjustment of the brake cable, if you hear a metallic scratch sound from a wheel then adjust its brake band. In this photo, grip the red circle and bend it outside(not too much!!). This is not a serious(or open occured) problem. Because the friction(between the brake band and the brake drum) starts from the blue circle, the band would be automatically arranged following the drum as riding & braking.

2. If you hear a pulse(or bit) sound(tuck tuck tuck…), tighten the nozzle cap of the rear wheel. These in-line photos show the reason. (You can here the pulse sound, here)

※ If you have a problem on your lovely A-bike then read this article in A-bike Central forum first. You will notice a fact that these A-bikers are too active in answering when you ask a question on the forum.