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  • Question about older Nimbus Giraffe

    I just aquired a used Nimbus Giraffe from Craigslist - my first giraffe! Although it appears unused, I know it is several years old because it has a track hub. Current Nimbus Giraffes have the safer bolt-on hub. Secondly, the tire tube has a Dunlop valve as opposed to the standard Schrader valve. The tire was flat and I figure the previous owner never came up with a way to air the tire. I have aquired a tube with a Schrader valve and removed the current tube. Upon checking it out more closely at home, I noticed the sprockets are not aligned perfect. One is offset relative to the other. As a guess, I would say there is between a 1/4 and 1/2 inch difference in offset.

    Is this how they all came during that period?

    Do current Nimbus giraffes with bolt on sprockets line up better?

    Is there any way I can align them with spacers or otherwise?

    Regarding the track hub, is there a specific tool for tightening and loosening the lock ring? I attempted to loosen it with a flat blade screwdriver and hammer but it started to cut into the ring.

    Lastly, I've read of 2 techniques for keeping the lock ring from coming loose. One is locktite and the other is spot welding. What other downsides are there to spot welding other than the obvious fact that the sprocket would be permanently attached to the hub?

    Thanks in advance for any answers.
    Level 1 Unicyclist
    D Licensed Skydiver
    Level 4 Silly Walker - government grant pending

  • #2
    Keep in mind that I have no experience with giraffe's, and so my advice only comes from over 10 years working as a bike mechanic.

    This is really interesting. First of all, I can't believe that someone couldn't get air into a dunlop valve. We occasionally had them come into our bike shop on old european bikes, and as I remember we just used a standard floor pump to fill them. I can't remember if the Schrader, or Presta pump was the ticket, but one of them just worked.

    The offset between the chainwheel and the cog I think is what we refer to as chainline. 1/4" isn't much to worry about unless the chain is short. Even 1/2" off on the chainline shouldn't be too much unless you have a very stiff chain, like maybe an expensive track chain. To align them I would say your best bet would be the spindle length on the bottom bracket. Spindles used to be available to put the chainwheel in just about any place relative to the fixed cup on the bottom bracket. If you know how far in, or out it needs to go you can pull your bottom bracket and bring the spindle to your bike shop. They should be able to hook you up with a spindle that will move the chainwheel to the desired spot.

    As for the lockring. Some of them are reverse threaded to the cog so that they lock against each other. Your screwdriver trick might work, but it's not ideal, and you could be going in the wrong direction. You can get a cheap lockring wrench at most bike shops. I think Park tools makes one that is under $10. I would recommend green loctite for this particular job. The green stuff is designed to wick in, and therefore doesn't need the piece to be apart for application. It is also ridiculously strong. It can set so well that you need to apply heat to remove it. If you use this stuff be very careful to get it only on the lockring, and not into the bearings, or cones and locknuts of your hub. Also, this kind of loctite has only a few good uses on cycles (this being one), so get a small tube, or when you go to the bike shop see if they have a drop for your lockring. You probably won't have much use for it in the future because it is a pain to get apart if the need arises.

    Well I think that answers your questions. I think John Foss would be the one to give you better first hand advice. I seem to remember more than a few giraffe post's where he gave the most definitive answers. You might try pm'ing him if he doesn't find this thread earlier.

    Good luck, and have a great time up there.
    "A properly ridden unicycle is like an object in orbit: constantly falling but never landing." -Diogenes

    Comment


    • #3
      Originally posted by Super G View Post
      Is this how they all came during that period?
      Roger Davies might weigh in with background on the Nimbus giraffes. Though I've seen various models, I don't know which one you're talking about.
      Regarding the track hub, is there a specific tool for tightening and loosening the lock ring? I attempted to loosen it with a flat blade screwdriver and hammer but it started to cut into the ring.
      Get a lockring tool as mentioned above. Careful with the screwdriver method, as you can crack/break the lockring. Especially if you're turning it the wrong way. I think the old Schwinn ones were reverse-threaded, but I can't remember for sure.
      Lastly, I've read of 2 techniques for keeping the lock ring from coming loose. One is locktite and the other is spot welding.
      First the downside of Loctite. Even if you use the permanent (red) stuff, you can't be sure it will never let go. I had some green Loctite used on a set of old Schwinn Giraffes I was refurbishing (by a bike shop), and the one I tested slipped almost immediately when I test rode it. They may have done a poor job of tightening things or may not have gotten the grease off the threads, I'm not sure. But you don't want your giraffe to go into coasting mode without warning.

      Two downsides of the spot weld. The obvious one is being stuck that way, and unable to change out the spokes. The other is the potential for bearing damage if too much heat gets in there, but if it's an actual spot weld this is probably not a worry.

      Originally posted by jtrops View Post
      First of all, I can't believe that someone couldn't get air into a dunlop valve.
      Dunlop valve! I had to look that up. Also know as a Woods valve, I think of them as Japanese valves, because they're very common on unicycles in Japan. I have a Japanese unicycle with one of those tubes, and I've never been able to get air into it with the pumps I have. Oddly enough, I've never ridden it though I have used it in a couple of shows! All I use it for is to demonstrat its built-in kickstand. I really should take some pictures of it someday...
      1/4" isn't much to worry about unless the chain is short. Even 1/2" off on the chainline shouldn't be too much unless you have a very stiff chain, like maybe an expensive track chain.
      Sounds like solid advice, but for bikes. On a giraffe there's more "riding on" the chain, so it's important that it tracks smoothly and can't jump the sprockets. The way to find this out is to set it up, tighten the chain and seen how it flows. If it keeps catching and trying to lift up on top of a tooth, look into making adjustments. But it'll probably be fine. You need enough tension in the chain to make sure it doesn't have too much slack. That's slack when someone is on it; hard to check without riding it. This is because the frame flexes a bit when you apply drive force.
      John Foss
      www.unicycling.com

      "Who is going to argue with a mom who can ride a unicycle?" -- Forums member "HiMo"

      Comment


      • #4
        I think the chainline problem comes down to you chain tension on some level. Even on a bike if the chainline causes the problems John described it would need work.

        On bikes you want to give yourself about 1/2" of slack as you push on the center of the chain. This is at the tightest position. Even without frame flex there is usually a point in the rotation that is tighter. From what John said I would think that on a unicycle the rule should be similar, but maybe a bit less than half inch of slack at that tight point.

        It certainly makes sense to make the final adjustments when riding.
        "A properly ridden unicycle is like an object in orbit: constantly falling but never landing." -Diogenes

        Comment


        • #5
          I am puzzled by the valve, we have always fitted schrader. It is possible that one got through without us noticing on a really early batch or the tube was swapped by the previous owner.

          My solution for the sprocket is leave it if it doesn't move.. or take it off clean threads to degrease it, then apply threadlock and tighten very very tight with a good C spanner and leave to set.

          Offset on sprockets. There is always some offset, it is not normally a problem.

          Hope that helps.


          Roger
          ++++++++++++++++++
          Roger Davies
          Unicycle.com in the UK
          The UK's Unicycle Source
          www.unicycle.co.uk
          +++++++++++++++++++

          Comment


          • #6
            Thank you jtrops, John and Roger.

            Well I successfully replaced the tube (first time I've done that) and re-assembled the giraffe. Jtrops, I am mechanically inclined but I have no experience with bicycle/unicycle mechanical work. With that said, I had to look up what a spindle and bottom bracket is to understand your answer. Upon researching that, I read the obvious fact that bikes with derailers inherently have offset. That made me a little more at ease. Upon re-assembling I noticed the fork opening had enough extra room to allow me to insert 2 washers as spacers. I inserted them in such a fashion as to reduce the offset. The factory offset appears to be aproximately 1/2 inch. (The top sprocket is aprox. 2" from the center of the frame and the lower sprocket is aprox. 1 1/2" from the center of the wheel.) I tensioned the chain as recommended and then looked for any change in tension as the wheel is turned. I did not find any change in tension. Great! Nor did it come close to losing the chain as John warned. Time for my first Giraffe ride!

            I've gotta say I was very nervous. Even though it's just a 5 footer, that's a big jump in hight! For comparison, I'm a skydiver with 380 jumps. The fear of skydiving is long gone. But there I was, with my feet just a few feet of the ground, and I was scared. You see, when I skydive I know I will land tiptoe soft. How will I "land" off of this? So this was like my first skydive all over again. What you say, there's nothing in common between the two? I disagree. With both activities you are worried about plowing into the ground! I laughed nervously as I pondered this.

            So I used a 6 foot stepladder at a school playground/parking lot to mount the beast underneath a basketball goal. I'd donned all my protective gear - helmet, shin guards, wrist guards and elbow guards. I got myself ready but was hesitant to go for it. Yep, I was sweating bullets. I ended up psyching myself up and then went for it! There I went, then down I went! I made it about 2 feet and fell off. But the fall wasn't bad! OK, try it again. Same thing. At least now the fear was receding because my falls hadn't been bad. I quickly remounted and yes, the third time was the charm! I realized you have to lean out a bit, then start pedaling to keep it under you. Ta Da! I was riding my Giraffe! As I'd hoped, it wasn't too bad once I got going. I laughed to myself for a good ways as I rode around the parking lot. What a feeling! I was doing great. Then I came upon a small piece of broken glass. I did an evasive maneuver to miss it and again laughed to myself. Then I crashed and burned. Hmmm, I need to get knee protection!

            While riding I felt the giraffe was doing just fine. The offset does not appear to be an issue at all, as Roger indicated. In fact, my first impression is that it is a very fine product.

            With daylight ending soon, I rode all I could - about 30 minutes. I upd'd every time but the last and fortunately came out with no injuries. The planned dismount was good and I was able to catch the uni as well. Once again though, I was hesitant. I found myself riding around mustering up the courage to do a planned dismount! All in all, I had a blast. Viva Nimbus!

            Now back to the original post...

            As for the valve, it appears to be the original. The seller stated he could ride well forward, but couldn't idle or ride backwards. The mint condition of the giraffe and the flat tire with Dunlop valve made me doubtful he ever rode it at all. Therefore I don't believe he would have changed anything on the uni. Plus I have heard of at least one other Nimbus being shipped to the US with a non-Schrader valve type. Not a big deal though. I now have experience changing a tube and I'm the kind of guy that likes to learn that kind of thing.

            John, when the LBS applied the locktite to your Giraffe, how long was it allowed to set up?

            jtrops, I will probably leave the uni as is now that it has passed a riding test. I do have a question about your solution though, in case I decide to perfect the uni. The spindle is what I take to be the axle, which is with the wheel. After looking at the glossary of Sheldon Brown's website, I can see how this could be replaced or modified to alter the location of the sprocket. What confuses me though is your mention of the bottom bracket. I understand the bottom bracket to be the "guts" of the crank assembly (not the bottom of the fork as I would have guessed). Which are you suggesting that I change - the crank assembly or the axle of the wheel in order to eliminate offset?

            Last question (for now):

            I noticed that the wheel itself doesn't spin as freely as I would hope when disengaged from the chain. What is the proper way to grease the axle internally? Please forgive my ignorance. I don't even know if this is something that can be greased or if it is a sealed assembly that you simply replace.

            Thanks again!
            Last edited by Super G; 2009-12-07, 01:51 AM.
            Level 1 Unicyclist
            D Licensed Skydiver
            Level 4 Silly Walker - government grant pending

            Comment


            • #7
              Originally posted by Super G View Post
              You see, when I skydive I know I will land tiptoe soft. How will I "land" off of this? So this was like my first skydive all over again.
              My first unicycle was a giraffe (1980). I am NOT planning to jump out of a perfectly good airplane any time in the near future.

              Once again though, I was hesitant. I found myself riding around mustering up the courage to do a planned dismount!
              The best way to get over the nervousness of giraffe dismounting is to do a bunch of them on purpose. The more you do, the safer you'll feel while riding. Practice them in every direction of the compass, including to the sides. Remind yourself how small the distance is between your pedals and the ground at all times.
              John, when the LBS applied the locktite to your Giraffe, how long was it allowed to set up?
              Unknown. This was in 1990 or so. At least overnight though. We had acquired a set of six Schwinn Giraffes from an elementary school in Ohio that was no longer using them. I was reselling them to interested parties and they had to be safe first. I had asked for red and they gave me green. I had some words with the mechanic-in-charge, they redid it and then they all rode solidly.

              Re chain tension. being a 5-footer you have a fairly short run of chain so you probably have nothing to worry about. I'd only mess with it if you experience the chain sticking/clicking. This will only happen if it's got a lot of tension on it. But I don't know a good measure for how tight that should be. The longer the giraffe, probably the greater amount of tension you want to be safe. This is because, assuming similar frame construction, over a longer distance there can be more frame flex, which will momentarily create more slack in the chain. It's more of an issue on taller giraffes.

              Same with the wheel friction. Unless it really spins crappy, I wouldn't worry about it. Giraffes are novelty cycles and for most people do not rack up lots of miles so they don't get a lot of riding wear & tear.

              As for my first unicycle, I still have it, and it's almost always the last cycle used in any show I do (not that I do them much anymore). Though I disassembled and re-greased the bottom bracket area many times, I've never taken apart the wheel axle and it works fine.
              John Foss
              www.unicycling.com

              "Who is going to argue with a mom who can ride a unicycle?" -- Forums member "HiMo"

              Comment


              • #8
                Great first ride. I'm glad I could help, even though I've never ridden a giraffe, or even looked at one closely. I knew John would have insight.

                The bottom bracket is the entire assembly that the cranks attach to. It includes: a fixed cup (chainwheel side), a spindle (axle to which the cranks attach), an adjustable cup with a lock ring, and bearings that can be loose, or caged. This is the spindle to which I was referring. The axle on your hub won't change your chainline. You will need a new spindle with the same spacing between the "cones," but more or less on the drive side to change the chainline. Honestly, I wouldn't worry about it though. It sounds like it's functioning very well as is.

                If your wheel isn't spinning as free as you think it should I would guess that it needs to be adjusted. Hubs with locknut's need to be adjusted a touch on the tight side because when you tighten the axle nuts on the dropouts the hub will loosen very slightly. It is exactly the opposite with quick release hubs. We used to have a couple of sets of dropouts on our bench just for getting good adjustments.

                When the wheel is off and you spin it while holding the axle does it spin freely? Is it hard to move the axle by hand? Repacking the hub is pretty easy, but most likely it will have loose bearing so be prepared to catch them as they fall out of the hub when you take it apart. To do any hub work you will need a cone wrench. It will be helpful in the disassembly, and necessary for the adjustment later. I'm going out on a limb here, but I would guess that you will need a 15mm cone wrench. You will also need a small adjustable wrench, or a 16mm box end wrench. I generally use a 6" crescent wrench.

                It sounds like you are already familiar with Sheldon Brown, I would look on his pages. I'm sure that whatever I'm going to say is said better by him.
                "A properly ridden unicycle is like an object in orbit: constantly falling but never landing." -Diogenes

                Comment


                • #9
                  Originally posted by rogeratunicycledotcom View Post
                  I am puzzled by the valve, we have always fitted schrader. It is possible that one got through without us noticing on a really early batch or the tube was swapped by the previous owner
                  I think some of the very first Nimbus 5' giraffes we sold at www.unicycle.co.nz had Woods valves, back in about 2003. I remember because my mate Rudy had one and would always ask me to pump up the tyre.
                  Take a squizz at my YouTube videos!

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                  • #10
                    Well I took my wheel back off to make sure I was thinking right. I was wrong. The wheel spins freely. My impression that it wasn't was due to me spinning the axle itself. Doing that takes more effort than I would have thought but again, the wheel spins freely. My apologies for asking assistance for something that didn't need anything done.

                    So I came in from my shop last night and my wife asked if I had been riding the giraffe (in the shop). I had to say, "No, it's too tall to ride in the shop." I find it nutty that I obtained the giraffe and rode it the only chance I had and the very next day a nasty winter storm started.

                    On a sad note, I was bummed to read that Sheldon Brown had passed away in Feb. of 2008. I had just discovered his site by researching the terms jtrops used in this post. His website is a goldmine of bike info and it appears he was quite an interesting character to boot.
                    Level 1 Unicyclist
                    D Licensed Skydiver
                    Level 4 Silly Walker - government grant pending

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