Amsterdam A-Biker

[Artefex]

Hello All,

Bought my Abike about a month ago and have been riding it almost every day (When its not raining) for its intended purpose, a combined bus and bike journey to work.

So far I have not had any major problems with it, but I think it is clear from the many posts that the ABike is not quite a perfect product. However, as I am an engineer I recognised it as a fundamentaly ingenious design the first time I saw it and the challenge of modifying and improving it is part of the fun.

I have only made some minor adjustments so far but will post them and any future mods here.

ABike.jpg (48.81 KiB) Viewed 43149 times

So far the biggest change I have made is to completely remove the front brake. I felt it was unnecesary and more likely to throw you off the bike if used to stop quickly. The front wheel now runs more smoothly without the brake rubbing against it. I also found that over tightening the front wheel bolt also stops it spinning freely. If you adjust the tension on the bolt there is a point where it is tight enough not to come loose and there is no resistance on the wheel.

The small wheels and low weight of the Abike mean that it doesnt pick up much momentum (For example if you go down a dip in the road there is not enough momentum to carry you up the other side like a normal bike), so removing any sources of friction helps.

I also found that, no matter how much I adjusted it, the bolt on the rear brake pad was rubbing on the tire and making a groove in the rubber. I solved this problem by removing the bolt and replacing it the other way around, (as shown compared to the original):

Rear Brake.jpg (91.2 KiB) Viewed 43170 times

You can also see that I have changed the chain tension to High, as the chain was loose enough to touch the side of the case.

[Artefex]

Thought I should add that I replaced the red hand grips with some black foam ones. More comfortable and much better at stopping vibration. It has been noted in some previous posts that standard handlebar grips are too small to fit, mine came from an old exercise bike with thicker tubes for the handles.

Handles.jpg (42.54 KiB) Viewed 43142 times

Another addition that comes from a previous post on this forum is the elastic between the handles. This makes the handles spring into position when folded and stops them flapping about when carrying the folded bike. I used the screws for attaching the bell to fix the elastic and then stuck all the loose ends together.

Elastic.jpg (48.84 KiB) Viewed 43147 times

[Job]

Great mods!

My mods:
+black foam grips
I didn't like the colour of the red ones, and the vibration in my hands was too much.
So I also opted for the black foam grips!
Only I used standard racebike ones, they fit really well
Plus they make the grip thicker, which is nice for my large hands.

+the elastic band around my brake grips
I missed the post on the forum, but figured this one out for myself.
Only I use a circular shock cord, so I can use it to tie little things to my Abike, e.g. a loaf of bread!

planned mods:
+making an infinitaly adjustable chain tensioner (I'm an engineer too!)
I already made a sketch, now I have to get a prototype made and test it.
Reason for this is that my chain is too loose in position M, and too tight in position H.
On my bike the tension would be fine at about M + 1/3. But the design of the tensioner doesn't allow for positions in between..

+make a foot operated / coaster brake on the rear wheel (and get rid of the brake grips and cables altogether)
I just hate hand-operated brakes.
Nice to see you're doing without the front brake!
You could remove the brake drum from your front wheel, and shave off a couple of grams there too.
I keep my front brake on for the moment, so I always have a spare brakeband with me should the rear one fail!

Interesting comment on the front wheel bolt tension, I will try that, cause my front wheel is not running as smooth as I like.

+put a suspension seatpost on
I think this will help reduce the strain on the bike.

+put a different saddle on
But I haven't found a nice and simple short and small one yet.

+cosmetic changes to get rid of the red plastic, and the prints on the bike.

+fit the toolkit to the bike (so I always have that with me)

+fit suitable leakproof tyres / wheels

+try to increase the distance travelled per pedal stroke.
Easiest seems to change the freewheel to a 15teeth version. Will require readjustment of the length of the primary chain. If it all fits in the gearcase..

So plenty of plans!

Job

[Guest]

I have similar plans but havent found a suitable seat yet. Do you know a good bike shop in Amsterdam where they have a lot of different parts to compare?

I agree that the gear ratio could be higher. On a flat bike path with a good surface (Most of them in NL) you just cant go fast enough. Its quite embarasing when you are pedaling like crazy and old ladies go past on thier omafiets. I am considering an electric motor for this, the low torque and high speed would be perfect, but changing the gearbox would be better if it can be done.

On the chain tension, a simpler option may be to drill 4 extra holes part way between the M and H ones.

[Job]

I haven't found the ultimate bicycle shop yet. It seems there are many shops, each with their own strongpoints / speciality.
The other day I was in an BMX-shop called Soulcycle at the Weteringschans. They have some interesting saddles, although their seatposts are all 25.4mm diameter.
The Abike seatpost is stamped 25.2mm, so I'm not sure the new post will fit without sanding down..
But it might be worth checking out.

Regarding the chain tensioner:
The drilling of extra holes in between the standard ones is an interesting option that I'm considering as well.
So when I bought the new screws, I also got an extra long set. These are needed if I drill extra holes, cause the nuts won't sit in their recess anymore.

I'm delaying this option because it will weaken the plastic tensioner ring, and I don't have spare ones yet.
Also I'm waiting helpful advice (and hopefully some new parts) from the abike-shop.nl.
If I get a new chain, chances are the length will be different, so no drilling yet!
See my post in 'Abike plus noises':
viewtopic.php?f=2&t=1411

Job

[Artefex]

Carrying Strap.

Have seen other posts on this (viewtopic.php?t=421) but think I have found the best way of carrying the A-Bike. I used an old laptop bag strap and fixed it to the side o the front wheel and the handlebar stem. The advantage of this is that there is no need to remove the strap before riding. In the unfolded position the strap does not get in the way of pedalling.

strap.jpg (57.16 KiB) Viewed 42995 times

Carries like a backpack over one shoulder.

strapfixing.jpg (59.06 KiB) Viewed 42997 times

bike with strap.jpg (39.92 KiB) Viewed 42934 times

[Job]

Wow, that looks like a quality mod!
I really like the way the strap stays on while riding, without being in the way.

Nice work!

Job

[Artefex]

Gear Ratio Mod

So far the greatest problem I have with the A-Bike is the low gear ratio, especially here in Noord Holland where there are no hills to be found. In preperation for replacing the freewheel I have taken measurements and made a quick drawing in the freely available Sketchup (This forum wont allow posting the .SKP file but the images are below).

The radius of the 15 and 16T freewheels can be easily worked out from the number of 1/2" links formed into a circle. Measuring the existing 14T freewheel shows that there is 3mm of clearance between the chain and the casing. The radius of the 15T freewheel is around 2mm larger so it will just fit. I have also drawn a 16T freewheel to show the amount of plastic casing that would need to be removed for this to fit. A 16T freewheel will be well within the bolts required to hold the case together so this should also be possible after some filing.

I intend to build both options using the "Claws" BMX freewheels from ACS and some half link chain.

[Artefex]

The increase in speed for each gear option is as follows:
14T: (14*35)/(8*9)*15cm*Pi = 320.70425
15T: (15*35)/(8*9)*15cm*Pi = 343.6117, +7%
16T: (16*35)/(8*9)*15cm*Pi = 366.5191, +14%

[Job]

Interesting graphics!

I made a picture of the freewheel and it's chain in the housing:

freewheel in casing.jpg (149.2 KiB) Viewed 42993 times

As you can see you can just about measure the gap via the lubrication hole (on the left).
But the gap seems to be even smaller at the recess for the front fork (bottom, curving upward).
I hope the bigger freewheel will fit, but the gap is quite small..

And someone on this forum said it was impossible to get the freewheel off the shaft..

At Soulcycle they have 16teeth freewheels in stock for about e12.
But I don't know if they're the right kind, as there seem to be different types of freewheels.

Also I measured the travelled distance for each complete pedal stroke.
-320cm unloaded
-300cm with me on it (and 90psi in the tyres)
So this is quite a considerable difference!

My city bike does about 500cm, but that would put way too much strain on the a-bike mechanics!

If you want some help in changing the freewheel, let me know. I'll be happy to assist.

Job

[Artefex]

I think I have found the correct freewheels here http://www.pietendebmx.nl/shop/index.php?main_page=index&cPath=2_56&zenid=1de17c8d8036ad1522fc239ce8ede078
The ones on the Soulcycle website are the left hand drive type or non standard sizes.
My understanding is that the freewheel thread must be the 'English' size, 1.370" x 24tpi

Ill see if it is possible to remove the old one before I order them...

[Artefex]

Folding Seat Using Standard Parts.

Finally replaced the seat. Personally I didnt find the original one uncomfortable but the post was too short. Used a BMX seat instead because they are small, practical and look cool.
To make the seat fold it should be the kind that attaches with two rails, using a saddle clamp that allows adjustment off the seat angle. A quick-release bolt replaces the bolt in the clamp so that the seat can be easily folded.
The only non-standard part is a bolt through the clamp so that it doesnt fall off the seat post while folding.

BMX Saddle.jpg (38.16 KiB) Viewed 43053 times

BMX Saddle Folded.jpg (54.19 KiB) Viewed 43124 times

The bike now feels more stable because contact with the seat is better than with the original and the height is correct. The bike is also smoother to ride after I tried using a silicone lubricant on the plastic steering bearings.

[Artefex]

Not had time to remove the freewheel yet...
Partly because I also had to deal with the chain stretching after a lot of use. It was already a bit too long when I got the bike but was quite tight on the H tension setting. Recently I found the chain length had increased by a suprising amount and was starting to rattle and get stuck against the wheel and gearbox. Because the chain tensioner was already on High, I tried removing one pair of links from the chain but this was too short on Low tension!
I couldnt find a half link for this size chain on the internet so made my own;

Half Link.jpg (36.8 KiB) Viewed 42966 times

I just bent one set of outside links into a half link shape and filed the holes at one end a bit larger, so the link pin will move smoothly instead of locking. The smaller end then goes between the next set of outside links (one inside link removed) and is pinned in place like normal.
This link is stiffer than the rest but the chain still bends and the chain is perfect at Medium tension.

Back to the problem of increasing the A-bike top speed, the 8" wheel copy solves this problem.
Calculating the distance travelled for each crank rotation (As shown above for the different freewheels) with the 8" wheels gives: 8": (14*35)/(8*9)*20cm*Pi = 427,605
This is 33% more distance travelled than the 6" wheels, still using the original gears.

[airness1977]

Greats mods, Artefex!

I bought mine in these days, and arrived yesterday (from other person that bought it for a gift and it doesn't like finally) and I have a question about the brakes. I like the idea of removing the front brake, maybe i'm going to do that, but I was thinking to change the left hand brake (rear brake) to the right hand brake, because here in Spain (I don't know out of here) the rear brake always is at the right hand brake (I'm not sure if I'm explaining it clearely). Do you think is possible to remove the left hand brake and change the rear brake to the right hand brake?

Thanks a lot.

[Perihelion]

I'm very interested in the left/right brake handle change as well. I can predict that I'm going to be going down a hill one day and forget that the right brake is the front one and and up going for a spill...