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  1. #1
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    Old Hand Screw Handlebar Stem

    Hi

    I have just bought an old folding bike, it's a Pannonia Mayfair. I cant get the handlebars to tighten properly, or loosen for that matter. It has a plastic screw thing (see image) which tightens and loosens, but seems to make little difference to how tight the handlebars are. I am not sure how this is supposed to work (or the purpose of it), there appears to be a normal nut below the plastic one, which from its position, looks like it is actually what is holding the handlebars in place. I cannot however get this to move. Has anyone here had any experience with these hand tightening handlebars?

    stem.jpg

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    Welcome, is this a Raleigh built bike? It could be that the nut is siezed and the knob is turning because the plastic is stripped out.
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    No, it was made by Pannonia. The knob is turning a metal rod, which passes through the nut below. It also moves up and down as you loosen and tighten it, and gets tight at the end of its travel in each direction. So the knob appears to be functional..

  4. #4
    jur
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    Hit the knob with your hand's heel. At the bottom is a taper inside the expanding tube which needs a sharp knock to dislodge it. This is why the knob is big, so you can hit it.

    [edit]Sorry brain fade. I see you are talking about the bars not wanting to tighten.
    My folding bike photo essays www.dekter.net/

  5. #5
    jur
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    Is the nut underneath on a threaded rod? If so it could be an after-addition... not there originally. Perhaps using a spanner to turn the nut would yield a result?
    My folding bike photo essays www.dekter.net/

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    It could be that the nut under the knob tightens the handle bars and the knob loosens the stem to lower it when folded?
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    I cant see the thread, but i assume so. I haven't been able to turn the nut (with a spanner). So is the plastic knob supposed to be used to adjust the angle of the handlebars? I was wondering if it had a different purpose and the nut was for that.

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    sorry, hadn't seen your last post. that's what I was wondering, would make more sense. doesnt seem to work though..

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    There is a bike like yours here you might ask that person
    http://www.cyclechat.net/threads/sho...e.89431/page-2
    Speed Uno
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  10. #10
    weirdo
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    5M, in what way are the handlebars loose? Do you meant that they can rock forward and back, or that the whole stem, with the bars, rotates side to side? Maybe both? I wonder if the same long bolt is meant to tighten the stem wedge and the bar clam simultaneously. If you can get the whole thing out (what Jur was getting at when he said to smack the knob with your hand), it might reveal enough to figure out how it`s SUPPOSED to work.

  11. #11
    Senior Member badmother's Avatar
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    Quote Originally Posted by rodar y rodar View Post
    5M, in what way are the handlebars loose? Do you meant that they can rock forward and back, or that the whole stem, with the bars, rotates side to side? Maybe both? I wonder if the same long bolt is meant to tighten the stem wedge and the bar clam simultaneously. If you can get the whole thing out (what Jur was getting at when he said to smack the knob with your hand), it might reveal enough to figure out how it`s SUPPOSED to work.
    Got a stem or two like this somewhere and I think your suggestion is right. This is a normal quill stem with a big plasticwheel instead of the normal top and I think the wedge is stuck inside the steering tube of the bike. I hope it can be without crushing the plastic. Maybe the plastic can be replaced but the owner may want to keep it original.

    Could the plastic be remowed so that you can hit the bolt under it? Maybe soaking the whole stem in molasses or amonia like the guys and gals in Classic and Vintage.
    °Empty drums make a lot of noice... (Old Hungarian proverb).

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    Thanks for the replies. The handlebars (with a little force) rock back and forward. The nut that I am now assuming would tighten this appears to be stuck, and slightly rounded. There is another nut at the bottom of the stem, which I would expect to release the whole stem, I haven't tried loosening that one yet. So the thinking is that the plastic knob is for height adjustment? And could be stuck, but maybe freed by hitting it?

  13. #13
    jur
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    I had a bike with a plastic nut like that. I ditched the whole lot and unfortunately don't remember well how well it worked. I do remember that the knob had to be hit quite sharply to free the quill stem, to lower it and rotate parallel with the frame for folding. Loosening that nut also loosened the bars to be rotated down next to the frame. But I don't recall that there was a nut where your bike has one.
    My folding bike photo essays www.dekter.net/

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    weirdo
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    Quote Originally Posted by 5M177Y View Post
    Thanks for the replies. The handlebars (with a little force) rock back and forward. The nut that I am now assuming would tighten this appears to be stuck, and slightly rounded. There is another nut at the bottom of the stem, which I would expect to release the whole stem, I haven't tried loosening that one yet. So the thinking is that the plastic knob is for height adjustment? And could be stuck, but maybe freed by hitting it?
    It`s tough to say exactly what you have there, or how its designed, but I`m going to take a guess that:
    ...the plastic knob is supposed to turn a long bolt or threaded rod which tightens the wedge at the bottom of your stem, the nut just above the handlebar clamp threads up and down that same long bolt to tighten the clamp, and the "nut at the bottom of the stem" is just the locknut for your headset bearings. The plastic knob is probably either pressed onto the end of that long bolt or has a threaded insert inside it and yet another lock nut to make it turn the bolt rather than just unscrewing itself. Just my guesses, and I could certainly be wrong.

    Assuming that you need to adjust or remove the handlebars to fold or for some other reason, or that the swaying bars make it unsafe or a PITA to ride, I`d say you have little choice but to escalate the battle. If you can live with it as is, you might still be curious enough to operate, but you take the chance of mangling things more.

    If you decide to go for it, some penetrating oil (WD40 works well) on the stuck nuts will help to free things up after several hours of soaking, though you still might be in for a fight. Then I`d try ViseGrips or ChannelLock type pliers to get the stuck nuts to move. If you manaage to get it all apart, you`ll be able replace the mangled nuts, but the long bolt might be tricky. If you`re able to get the clamp nut up a little bit so there`s some space between the nut and the clamp, try again to loosen the plastic knob, then smack it down like Jur said. That should hopefully free the wedge so that you can twist and pull the stem out. From there it will be obvious how it all works.

    5M177Y, I have no idea how much experience you have at working on bicycles, or on bikes from what era, so forgive me if you already know a lot of this. Do you know how a quill stem works? You can google up a diagram if not- it`s very simple when you see one, but if you have no idea, none of our comments will make much sense. And the nut at the bottom of the stem- is it a large diameter, but very thin nut that the stem goes all the way through? If that`s the case, it almost certainly WOULD be the locknut for your headset bearings. Loosening that without being able to get the stem out won`t help you any- it just gives the little BBs in the bearings a chance to fall out and get lost. If you find diagrams of a threaded headset and a quill stem, you`ll be in a good position to try it yourself. If you can`t find those, or you just don`t feel like messing with it yourself, you could always take it to a shop and have the mechanics there give it a shot.
    Last edited by rodar y rodar; 05-18-12 at 08:51 PM.

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    weirdo
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    Quote Originally Posted by badmother View Post
    Got a stem or two like this somewhere and I think your suggestion is right. This is a normal quill stem with a big plasticwheel instead of the normal top and I think the wedge is stuck inside the steering tube of the bike. I hope it can be without crushing the plastic. Maybe the plastic can be replaced but the owner may want to keep it original.

    Could the plastic be remowed so that you can hit the bolt under it? Maybe soaking the whole stem in molasses or amonia like the guys and gals in Classic and Vintage.
    Badmother, did yours clamp the bars also?
    What`s with the amonia or molasses? I haven`t heard of that one- is it for reconditioning the plastic or for freeing stuck metal parts?

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    Senior Member badmother's Avatar
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    Quote Originally Posted by rodar y rodar View Post
    Badmother, did yours clamp the bars also?
    What`s with the amonia or molasses? I haven`t heard of that one- is it for reconditioning the plastic or for freeing stuck metal parts?
    Actually you reminded me, I need to edit: Soaking in diluted molasses is to get rid of rust on steel or when steel&steel is joined w rust.

    The Amonia is when a stem or seatpost of aluminium is stuck in a steel frame (not the case here). At the moment I have stuff brewing in winegar, that is what I should have said instead of Amonia, winegar is for cleaning up steel. Looks horrible actually. Tend to forget about it brewing outside and peopel who have been invited for dinner starts wondering what the old witch is cooking up this time..

    Third method is dropping the corroded steel in a water bath with some soap and then add electrisity. Spooky. Got some heavy batteries sitting here waiting for the experiment but not done it yet.

    I have one or two stems like that. One is in the shed, the other one maybe on a bike in the basement. Going to take a look tomorrow.
    °Empty drums make a lot of noice... (Old Hungarian proverb).

  17. #17
    Senior Member badmother's Avatar
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    The stem I found is just a long quill stem and the plastic nut is there to loosen the quill without tools. There is a different bolt and a nut under the bars holding the bars, so two different systemslike any quill, just looking slightly different at first glimse.

    I know I have seen stems where the long bolt going trough the stem is also holding the clamp around the bars.
    °Empty drums make a lot of noice... (Old Hungarian proverb).

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    weirdo
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    Quote Originally Posted by badmother View Post
    Molasses...
    amonina...
    vinegar...
    Thanks, Badmother.
    I wonder if the OP is having any luck. I did a search on that bike and found he`d also posted in another forum- hope it works out one way or another. And there are a few (not many) pics of that model floating around in Cyberland- it looks like the stem is original. One link led back to an old post here on BFnet, but the pictures for that one didn`t work any more.

  19. #19
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    Quote Originally Posted by 5M177Y View Post
    Hi

    I have just bought an old folding bike, it's a Pannonia Mayfair. I cant get the handlebars to tighten properly, or loosen for that matter. It has a plastic screw thing (see image) which tightens and loosens, but seems to make little difference to how tight the handlebars are. I am not sure how this is supposed to work (or the purpose of it), there appears to be a normal nut below the plastic one, which from its position, looks like it is actually what is holding the handlebars in place. I cannot however get this to move. Has anyone here had any experience with these hand tightening handlebars?
    stem.jpg
    I have one on one of my Rallye Royal Sport Jet Star Bike-http://sites.google.com/site/compact...-jet-star-bike. They were popular in the 1970s. When it functions as it should, it is very easy to turn to tighten/loosen the stem to rotate the handlebars for "collapsing" or sliding the stem up/down for fit. It sounds like one or both below:

    • Your nut-which is inside the knob-is frozen in place.
    • Your stem needs servicing.
    • or both


    What I did with my Raleigh Twenty using PB Blaster: http://sites.google.com/site/compact...ess-starts-now I don't know if PB Blaster would harm plastic like your knob. My Raleigh Twenty is all metal in that respect & I covered up the parts (like saddle ) I did not want the PB Blaster to get on. I myself would head over to the nearest bike shop for that sort of problem anyway. After all, you might not be able to replace that sort of early 70s unique knob just in cast harsh chemicals might damage the plastic.

    Here is an ad for this sort of bike with plastic knobs: http://losangeles.craigslist.org/wst...029730933.html
    Last edited by folder fanatic; 05-22-12 at 10:30 PM.

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    Hi guys. Sorry, I didn't realise there had been more replies!
    I have tried WD40 to try to loosen the nut, but no luck as yet I'm afraid.
    Here is a photo that shows all the nuts
    stem.jpg

  21. #21
    Senior Member badmother's Avatar
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    Theoretically you need to hit the plasticnut to release the stuck "nut" innside the stem but I am not sure the plastic can take that.

    Next option ids to soak the stem in "stuff" that can loosen up the corrotion but that is not easy since the bike is all in one piece.
    °Empty drums make a lot of noice... (Old Hungarian proverb).

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    weirdo
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    As long as the nut on top of the bar clamp is still tight, I don`t think smacking the plastic will do any good- the top nut is still holding the bolt, so the wedge can`t go anywhere. Need to loosen that top nut first. See if you can clean up the flats with a file enough to get a good wrench on (better a regular open end wrench than an adjustable). If not, you`ll have to use Vise Grips. Loosen that nut first, THEN try the wedge (hitting the plastic handle). The big, flat nut at the bottom of the stem is definitely the headset locknut- I wouldn`t mess with it until you`re able to get the stem out because all that will do with the stem in place is let the bearing rollers fall out.

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    I think the plastic nut should theoretically move independently of the nut below it. It does loosen and tighten and pass up and down through the nut.. just it doesn't actually release anything. That said, that nut below is the main problem at he moment, as the handlebars are not tight enough for my liking.

  24. #24
    Senior Member badmother's Avatar
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    Quote Originally Posted by rodar y rodar View Post
    As long as the nut on top of the bar clamp is still tight, I don`t think smacking the plastic will do any good- the top nut is still holding the bolt, so the wedge can`t go anywhere. Need to loosen that top nut first. See if you can clean up the flats with a file enough to get a good wrench on (better a regular open end wrench than an adjustable). If not, you`ll have to use Vise Grips. Loosen that nut first, THEN try the wedge (hitting the plastic handle). The big, flat nut at the bottom of the stem is definitely the headset locknut- I wouldn`t mess with it until you`re able to get the stem out because all that will do with the stem in place is let the bearing rollers fall out.
    Looking at the picture left me with the impression that the plastic nut can be turned, at least some and that what is stuck is that cast iron thingy innside the steerer tube. This is why I said hit it. If I am wrong about this of course my suggestion is not the best.


    To the OP:
    There is too many "nuts" mentioned without specifying. I do not understand what "the nut below" is suposed to mean. If it is the top nut of the headset then for sure do not touch it!
    Last edited by badmother; 05-30-12 at 01:38 PM. Reason: zPelLiNg
    °Empty drums make a lot of noice... (Old Hungarian proverb).

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    Quote Originally Posted by badmother View Post
    There is too many "nuts" mentioned without specifying. I do not understand what "the nut below" is suposed to mean. If it is the top nut of the headset then for sure do not touch it!
    Sorry, when I said "nut below" I meant the one directly below the plastic thing.. the one holding the handlebars in place.

    Which one at the top of the headset shouldn't I touch? There is a thin one below the reflector holder and a more conventional one above it (which I have undone).

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