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Thread: Birdy thread

  1. #101
    Car free since 1995 pm124's Avatar
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    Quote Originally Posted by jur View Post
    I installed a 58T chainring for a small improvement. I can pedal up to 40km/h with reasonable comfort. Since the Birdy is my commuting/touring bike, that's adequate.
    Jur, either you spin slowly or your cyclocomputer is set incorrectly. At 100 RPM you should get 42km/h out of the stock 56T chainring and the 11T cog. I've only lacked gears on steep descents.

  2. #102
    jur
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    I think you're right, I do spin on the slow side. 70-90 is more my relaxed preferred rpm, 90-100 and higher when I am putting the hammer down.

    Some time ago I finally realised that pedaling is about 2 things - spinning and torque. Your legs are comfortable putting out a certain torque. If you're riding slowly, then there is no point in spinning for it's own sake - use your preferred torque and just spin slower, your knees won't complain any more than when using that same torque at higher speeds. If you're going fast, then that same torque at a much higher rpm, results in larger power. Chris Carmichael said the same thing about LA - Lance isn't spinning fast to produce large power, he can spin fast because he can produce large power - exactly the other way round.

    Now at about 40km/h I spin comfortably and I can go quite a bit faster, eg 50 is not a problem; but then I need to concentrate hard to avoid bouncing on the elastomer, and of course it tires you out quite soon. I prefer to relax a bit more.
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  3. #103
    Car free since 1995 pm124's Avatar
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    Jur--That makes a lot of sense. I find that to keep the bike from bobbing I do have to keep my RPM down.

  4. #104
    Senior Member Fear&Trembling's Avatar
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    I found that above 110 rpm the Birdy "bob" would become annoying and made for a bumpier ride.

  5. #105
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    how usefull do birdy owners find the suspensionon the road.Would it be better without?

  6. #106
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    I'm having issues with the seat post quick release. It's loose and keeps slipping (I end up 2 inches lower than intended).

    I've tightened it, but even though it feels very tight when I am closing the lever, it feels loose in the last 0.5 cm or so and when it is closed. Any ideas how to fix it?
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  7. #107
    jur
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    Put some lube on the QR surfaces that slide past each other. Boeshield T-9 works wonders. Then you can make the QR close tighter with no extra force.
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  8. #108
    crazy bike girl msincredible's Avatar
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    Thanks jur! I'll give it a try.
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  9. #109
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    Quote Originally Posted by bhkyte View Post
    how usefull do birdy owners find the suspensionon the road.Would it be better without?
    As the current owner of a Birdy and ex-owner of a Xootr Swift, I'm very happy with the suspension. The Xootr was a faster bike on perfect surfaces, but I found it jarring and uncomfortable on most of the roads locally. The Birdy is probably a little slower, but I find long rides much more comfortable. I've done lots of 30-60 mile rides on the Birdy and it's a real pleasure.

    Actually, I'm considering making it my touring bike too. So I'd need to get the rear rack, and increase the gearing range. I have the 9-speed capreo, and am considering getting a 53/39 double crank. Has anyone done this conversion? I seem to remember reading that putting a double crank on may mean that the chain falls off more often when folding?
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  10. #110
    jur
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    Quote Originally Posted by yangmusa View Post
    Actually, I'm considering making it my touring bike too. So I'd need to get the rear rack, and increase the gearing range. I have the 9-speed capreo, and am considering getting a 53/39 double crank. Has anyone done this conversion? I seem to remember reading that putting a double crank on may mean that the chain falls off more often when folding?
    My Birdy is my touring bike too. We travel rather light, so I get away with 2 small panniers at the back. When camping gear is included, I put the bedrolls and tent at the front on the lowrider rack. I still find the 300% gear range of 30-90" adequate. I hardly ever use the low gear and even when riding loaded, the load is not that heavy to require extra gearing. On very steep slopes I might think an extra gear would be handy, but even these usually do not last that long and I'm able to handle them. On monster slopes SWMBO & I usually separate and I wait for her at the top or at rest stops.
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    Quote Originally Posted by yangmusa View Post

    Actually, I'm considering making it my touring bike too. So I'd need to get the rear rack, and increase the gearing range. I have the 9-speed capreo, and am considering getting a 53/39 double crank. Has anyone done this conversion? I seem to remember reading that putting a double crank on may mean that the chain falls off more often when folding?
    Other options for expanding the gear range could be a Schlumpf Speed Drive with a 1.65 overdrive.. that option would eliminate the need for additional chainring/shifter/front derailleur/cables and such.. another option could be a Sachs 3x7/8 rear wheel.. I have a couple of both units in stock.. pm me if interested.

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    This is the ride I did on Sunday, and I spent a lot of time in 1st gear. Could be I'm just a weak climber

    EDIT: Motionbased isn't very good at rooting out obviously erroneous GPS data. There are some steep bits for sure, but not 31% climbs or 84% descents (that would be near free fall, no?)

    I'm considering riding fully loaded over Mt Tam to get to Stinson Beach or Point Reyes national seashore. I really don't know if I could make it up those hills with full camping gear. On the other hand, I haven't tried either - maybe I should try overnighting in a B&B in Stinson Beach first, with a smaller load. If I can avoid increasing the weight, cost and complexity of adding a double crank that would only be a good thing.
    Last edited by yangmusa; 12-02-08 at 04:05 PM.
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  13. #113
    jur
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    Bruce:

    I still have that one Schlumpf SD from you... I bought it specifically for the Birdy, even though at that stage I was unsure of what I would be getting.

    One reason it isn't installed yet, is the Birdy's rear swivel arm has a slight depression where the chain goes past. I'm unsure at this stage whether the smaller chain ring required by the Schlumpf will cause regular chain rubbing.

    Unrelated Schlumpf questions:
    1. Do you get the gear shifting buttons unscrewing? I have a few times just caught one or the other button before it fell off mid-ride. I have made a tool for tightening but that hasn't helped. The locking set screws are as tight as I dare. I daren't use Loctite for fear of not getting the button off again when I need to. Any thoughts?
    2. Do you get slippage of the bottom bracket when in overdrive? This has happened to me a few times now, not very bad though, but enough that I avoid hard cranking in overdrive.
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  14. #114
    Eschew Obfuscation SesameCrunch's Avatar
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    Quote Originally Posted by yangmusa View Post
    T
    I'm considering riding fully loaded over Mt Tam to get to Stinson Beach or Point Reyes national seashore. I really don't know if I could make it up those hills with full camping gear. On the other hand, I haven't tried either - maybe I should try overnighting in a B&B in Stinson Beach first, with a smaller load. If I can avoid increasing the weight, cost and complexity of adding a double crank that would only be a good thing.
    Yangmusa:

    What do you think about just putting on a double crank without a front derailleur? Just change in/out of the small ring by hand when you need it. I did that for my Merc and it's very handy for the occasional times when I need a low gear. Fairly low cost solution.

  15. #115
    Car free since 1995 pm124's Avatar
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    Sometimes I get a bit of slippage when I've cleaned the bike. If Jur's trick doesn't work, try a little hairspray or any other similar substance on the seat post.

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    Quote Originally Posted by jur View Post
    Bruce:

    I still have that one Schlumpf SD from you... I bought it specifically for the Birdy, even though at that stage I was unsure of what I would be getting.

    One reason it isn't installed yet, is the Birdy's rear swivel arm has a slight depression where the chain goes past. I'm unsure at this stage whether the smaller chain ring required by the Schlumpf will cause regular chain rubbing.
    That's interesting.. not exactly positive of the answer there.. looking at my Birdy, I can't see where a decrease in chainring diameter would cause any clearance problems.. my bike has a double chainguard and the inner chainguard doesn't contact the frame... I think the Capreo Birdy runs a smaller chainring (45t) as I remember... this would yield a 288% range of approximately 30 to 88 gear inches.

    Quote Originally Posted by jur View Post
    Unrelated Schlumpf questions:
    1. Do you get the gear shifting buttons unscrewing? I have a few times just caught one or the other button before it fell off mid-ride. I have made a tool for tightening but that hasn't helped. The locking set screws are as tight as I dare. I daren't use Loctite for fear of not getting the button off again when I need to. Any thoughts?
    I lost one once... looked for 1/2 hour and I knew within a block of where it fell off... my guess was it must have rolled into the sewer.. from that time on, I use a spot of Loctite blue (as you know, same as what's on lots of brake adjusting screws).. none of my shift buttons have fallen off since and I'm still able to remove them if I want ..



    Quote Originally Posted by jur View Post
    2. Do you get slippage of the bottom bracket when in overdrive? This has happened to me a few times now, not very bad though, but enough that I avoid hard cranking in overdrive.
    I don't, and all my installations have aluminum BB's, but they are cinched down pretty well.. do you have the Schlumpf socket tool?

  17. #117
    Car free since 1995 pm124's Avatar
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    Quote Originally Posted by yangmusa View Post
    As the current owner of a Birdy and ex-owner of a Xootr Swift, I'm very happy with the suspension. The Xootr was a faster bike on perfect surfaces, but I found it jarring and uncomfortable on most of the roads locally. The Birdy is probably a little slower, but I find long rides much more comfortable. I've done lots of 30-60 mile rides on the Birdy and it's a real pleasure.

    Actually, I'm considering making it my touring bike too. So I'd need to get the rear rack, and increase the gearing range. I have the 9-speed capreo, and am considering getting a 53/39 double crank. Has anyone done this conversion? I seem to remember reading that putting a double crank on may mean that the chain falls off more often when folding?
    Yes, the suspension is a must with the little wheels. The Birdy's suspension is pretty tight. There is about 2 cm of travel on a good pothole. Good at absorbing road vibration, but nothing like a mountain bike.

    When I ride in Thailand, I use a double on the front. The chain falls off every time I fold the bike. So, I usually switch to a wax based lubricant. Helps keep the fingers clean a little bit. Being a New Yorker, I always fold and bring it inside.

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    Birdybike Group

    Hi,

    I was looking thru the Birdy Wiki entry and found a link to this discussion. Just wanted to let you know that a lot of Birdy specific information can be found at:

    http://sports.groups.yahoo.com/group/birdybike/files/

    I am the group moderator there. We have been around since 1999 and have nearly 900 members. A lot of queries that have been put here have been addressed in many filed messages over these many years.

    I'm near Berkeley, California and have three Birdys.

    Cheers,

    Bob

  19. #119
    Car free since 1995 pm124's Avatar
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    Hi all. Anyone check out the Flicker album on the 2008 World Birdy Meeting? http://www.flickr.com/groups/birdy-b...th/2586804762/

  20. #120
    jur
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    Birdy Monocoque 3 months update:

    I give a touring review at the end in case you want to skip all this stuff.

    It's been 3 months since getting Birdy Monocoque, during which I almost exclusively rode the Birdy.

    Gearing:

    I have upgraded the shifter and derailer to 9sp '08 XT after the 8sp Alivio started showing a large amount of hysteresis requiring me to double-shift down and single-shift up in order to do a single down-shift. I have since discovered this is partly due to the cheap chains I was using in rotation with the original chain - the original Shimano one works a lot better. Never mind, I am still wearing out the 3 chains I have in rotation, and the upgrade to XT was intended anyway. Currently I am still using the 8sp drivetrain with the 9sp shifter - it works. Once the cassette is worn I'll install the 9sp one I have on ice.

    I originally intended installing a SLX Shadow derailer for its low profile and direct cable routing; but when I got it, I found the Shadow couldn't be fitted due to the cable routing - the cable comes out the rear fork member too close to the RD to allow the cable to go sideways enough to engage the cable stop on the RD. So I did a bit of RD swapping at home and ended up with a medium cage XT for the Birdy. (The SLX Shadow went on SWMBO's Reach Offroad instead.)

    As mentioned in an earlier post, the front chainring was swapped for a 58T Vuelta to improve top end gearing. It is adequate now but a wider range for touring is probably the way to go. I may install a second chainring a la pm124 and see how it goes with folding etc.

    The chain has self-derailed a number of times when in the lower end of the gearing, falling in between the plastic guard and the chainring. I don't know why this happens. Possibly after swapping the chainring, the guards are no longer firmly held in position and allows the chain to gradually push it aside when touching it, ending up so eccentric that it touches the metal anti-derailing device with every revolution. With the guard out of the way at one position, it could derail. I will get a metal guard from Greenspeed to fix it good.

    I still haven't decided to install the Schlumpf Speed Drive.

    Tyres:

    The original back tyre threatened to blow off the rim several times one day, so I took it to the LBS who gave me a 1.5" Marathon Racer instead for a discount. I have since replaced the back tyre with a 1.35" Marathon Plus for commuting/touring duty. The front still has the Maxxis Birdy on there. The Racer I took on tour as a spare.

    Rear suspension:

    I have taken to commute with the harder green elastomer; it allows me to spin faster without reaching the bouncing cadence. For more leasurely rides I swap in the red one. I carry the spare in the saddle bag for on-the-go swapping.

    Braking:

    The front brakes pads were poor from the start, so pretty soon I ditched them and installed better quality units with replacable pads. Big improvement. The rear are still the originals; I hardly ever use the rear brakes so they are still in almost new condition, as are the rims.

    Folding:

    I have it down to an easy non-rushed sub-30s now. I could do it in less if I rushed but haven't timed myself doing it fast yet. I have to be careful with the chain as the medium cage XT RD gathers less chain and it tends to fall slack. That was unexpected; I thought the RD difference to be small enough so that is not an issue. It may be the lack of cable flexibility that prevents the RD from swinging backwards fully.

    The wider rear tyre snags on the front low-rider rack when folding. The narrower Marathon Plus does not have this problem, but the wider Racer and the Maxxis do. The rack has a short section of bar sticking out behind the pivot; I cut this off to solve the problem. I don't now what the extra section is for; you can't use it for hanging a pannier hook on as it will slip off.

    Annoying Little Things solved:

    - I have found I can remove the rear wheel after all by pulling through some cable from the front to free up the bake arm, allowing the pads to separate far enough to pull the wheel out.

    - I have an acceptable solution for bottle cage fitting - a black plastic Cateye cage comes with slots to fit wide cable ties through, and these go around the stempost. For folding, the bottle cage interferes but since it is on cable ties, I just push it aside to the right.

    - After fitting the rear folding rack, I found the bike rests on the back of the rack instead of the mudguards, providing a reasonably stable self-standing folded bike.

    - The handlebars don't snag on the rear wheel QR when folding down if I push it down past the last safety stop. No biggie - the current lower position is my preferred position anyway. I may drill an extra hole for the safety stop to engage in.

    - I have trimmed the cables to a bit better neatness.

    Loaded Touring:

    I took the Birdy on a 10 day loaded tour of Kangaroo Island. We drove to the island ferry point on the mainland and left the car behind.





    As you can see from the photos, I had small panniers on the back; each was loaded just over 5kg. On top of the rack I bungeed the sleeping bag in a waterproof bag. My Crocs were captured under the same bungee.

    For water bottles, I had the original Cateye on the stempost, plus another one cable-tied to the top tube. I used white electrical tape to protect the paintwork under the cable ties. Under the rear rack was a third bottle held in place with a big rubber band with a hook on the end. All these worked quite well, but I had to remove the 3rd bottle when folding, which happened only in the car journey to and from the island ferry.

    On the front I carried both our Thermarest mattresses rolled up with the tent. Each of those was about 2kg, pannier included. The front "panniers" are home-made vertical racks made from flute-board (Coroflute, Coroplast) with straps for holding the rolls.

    On the handlebars I hung my small backpack which was mostly empty; I had it with me for when going out on foot and suchlike. It proved to be very handy for easy storage of extra items like food. It also had a 2l water bladder for insurance, but which I never used.

    So, how did the bike handle the load?

    Poorly and brilliantly.

    By far the biggest effect was from the load on the front. The extra inertia of the load had the effect that the front end of the bike flexed like a belly dancer on steroids. I could shake-rotate the bars from side to side while the frame twisted. This effect led to uncontrollable shimmy at speed. At speeds above 30-40km/h, the front would self-develop a low frequency shimmy which I could not damp out except by slowing down. I could never take one hand off the bars at say 20km/h either, when the same shimmy would set in with one handed riding such as when trying to take a drink. I never lost control, though.

    I have put a lot of thought into why the Birdy does this. Other users as well as the Australian manual mentiones that the front suspension pivots have to be tightened to fix this.

    I disagree.

    The mechanism for the shimmy involves the steering geometry and the suspension. As the wheel turns sideways, the contact patch shifts forwards and sideways. At speed, this has the effect of compressing the suspension spring as well as straightening out the wheel. The stored spring force will tend to exaggerate the straightening of the wheel so it goes in the opposite direction, oscillating to and fro. The frequency of this oscillation is directly dependent on the spring force and the rotational inertia, ie the load. Heavily loaded, the effect becomes strong as the system is poorly damped due to the ratio of load mass and spring force.

    Damping can be added by trying to hold the bars straight, by making the steering bearing drag or by making the pivots drag.

    Tightening the pivots to make them drag heavily may fix the shimmy, but now the suspension has lots of stiction (which degrades performance) and folds with some effort (which you don't want either). Mine is already as tight as I will allow it; to fold it, I have to drag the front around to the folded position, it won't swing freely. I am definitely not going to make matters worse there. Plus lots of drag will make them wear much faster, and I don't want that either.

    So, the shimmy is not caused by "loose suspension pivots" as is alleged; it is caused by the geometry design. A better approach might be to get a highly damped elastomer for the front. This same shimmy is also the cause for me not being able to ride it no-hands while unloaded.

    Another approach is not to load the front, or to load it less.

    The suspension also made the ride brilliant. The extra load made the ride much more plush again. This was particularly important as a lot of the KI roads are gravel roads which are often heavily corrugated from cars or rough from bad surface wear. The suspension did a huge job to smoothe all that out. SWMBO also agrees that the suspension on our bikes made all the difference between a horrible ride and a tolerable ride.

    The only other bike which I have ridden fully loaded, with heavier load, albeit with all the load on the back, was the Raleigh Twenty. My opinion is the R20 is a better touring bike. Much better. I screamed down slopes faster than 60km/h fully loaded, with never a whimper from the R20, absolutely steady as on rails. With the Birdy I would now be nursing sores if I tried that.

    Nevertheless, once I got used to the load shortcomings, it was fine.
    Last edited by jur; 01-05-09 at 10:30 PM.
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  21. #121
    Car free since 1995 pm124's Avatar
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    Very interesting. I get hands-off shimmy, but the bike is pretty darn stable at speed. I usually use evenly distributed panniers on the front, though.

    On my recent ride there was an 11Km steep descent with hairpin turns that cars become stuck on. I was faster on the Birdy than I was on a hardtail mountain bike on the descent. I've never really loaded up though.

    I also had chain derailment issues. That happened after the suitcase was smashed last year. I bent the front chainring badly enough that it derailed even with the chainguard on it. Putting a new one on straightened that out.

    Running it with dual chainrings invites it to derail unless you can fit an outer chainguard and an inner damper such as the kind Dahon uses. (The Dahon one fits, but the way.) You may also want to check your chainline if you are not using your original bottom bracket. Finally, you might want to double check that the crank is on good and tight.

  22. #122
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    Quote Originally Posted by jur View Post
    Folding:
    I have it down to an easy non-rushed sub-30s now. I could do it in less if I rushed but haven't timed myself doing it fast yet.
    I haven't timed myself folding the bike at all. But one thing I've noticed is that initially my chain almost always fell off and got folded/kinked - required dirty hands and swearing to put right. Now that I'm more used to it, I swing the back wheel under faster (or with less hesitation), and that seems to make all the difference. The chain rarely falls off.

    Quote Originally Posted by jur View Post
    Annoying Little Things solved:

    - I have found I can remove the rear wheel after all by pulling through some cable from the front to free up the bake arm, allowing the pads to separate far enough to pull the wheel out.
    Oh, I've not had trouble with the brake stopping the wheel from coming out. On my bike it's tricky to get the wheel out with the rear skewer in place, and impossible to get the wheel back on. The skewer catches on the derailleur, where it mounts to the frame. This is a minor annoyance, not really a big deal - but it strikes me as bad design.
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  23. #123
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    Jur--The "low frequency shimmy" does not sound like shimmy at all, but rather a dangerous speed wobble. In the hands of a less capable rider, that can cause some big problems. This is not a known problem with the Birdy from what I've read on the forums. But Martin Donnely on the Yahoo groups forum experienced speed wobble on a 1990s era Birdy that was heavily modified (and cracked). You might want to contact your dealer and try to get Pacific/R&M to replace the frame for you. That would be totally unacceptable in my book. Unless I'm in sand or powder, I find both of mine to handle well at speed.

    Are you certain that there isn't anything pressing against the moving arm of the front suspension?

  24. #124
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    Jur:
    I had a stabilty problem which was caused by a removeable bag I mounted off the stem of a mountain bike.

    While the mounting was solid, the weight in the bag would flex the bag and oscillate from side to side, turning the steering and causing the wobble.

    Could your problem be in part due to oscillation of some of the loads you have attached to the front fork?

    David

  25. #125
    jur
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    The load I had on the front was none too rigid, I admit, and I also considered that to have a significant influence. On days where I had some stuff in the loosely-slung backpack, the tendency to wobble was a lot worse.

    I still have the bedrolls assembled; I'll check them again with no load on the back and with extra strapping to make the load more rigid.

    Perhaps there is something wrong with the frame on the whole - I have had the riding no-hands problem since the beginning. So I'll give it a good check-up. It's just that the bike felt really unstable while loaded.

    Oh, and another thing - on coming back home, I found the front tyre quite soft - and I know that is a major factor too. I let some air out for the dirt roads, but don't recall that it was that soft.
    My folding bike photo essays www.dekter.net/

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