This sounds like a pretty good deal on the Torker Giraffes at uni.com.
Why are they so cheap?
Or is the consumer actually getting a good deal this time?
This sounds like a pretty good deal on the Torker Giraffes at uni.com.
Why are they so cheap?
Or is the consumer actually getting a good deal this time?
Is the new Torker giraffe using a threaded track style hub with the sprocket threaded onto the hub and held in place by a lockring? From the pictures that UniBrier posted it looks like they’re using a threaded on sprocket down at the hub. I don’t like giraffes that have a threaded sprockets. It’s not safe. I’d rather that Torker designed a hub where the sprocket bolts onto the hub like Schwinn did on their later model giraffes. The threaded on sprockets usually need to be welded onto the hub to keep them from slipping and that is not an ideal solution.
Maybe Torker has designed something that will keep the sprocket from slipping. I’d have to take the sprocket off the hub to find out. You can’t tell from the pictures. But my guess is that the sprocket is threaded on.
Other than that, the giraffe looks good. It’s not professional quality, but then you’re not paying for a DM giraffe either.
i’m not speaking from experience, but why are bolted on sprockets superior? track racers spend uber money on their bikes, and if bolts were better, that’s what they’d be using, right?
The ‘experience’ is to have the sprocket unscrew. Track bikes are only pedaled in one direction. On a unicycle, we use all our strength to change directions all the time. Threaded-on sprockets can be a lawsuit in the making…
That’s exactly what I was thinking. I am definitely buying one. If it unscrews I am going to be rich! I hope they have good insurance.
i dont think anyone could win a courtcase when their opening arguments are:
“i was riding my unicycle down the street when…”
In this country, any frivolous lawsuit is possible. Shattering your elbow because your unicycle unscrewed on you while you were riding it normally has happened, and probably could be actionable. I’m not recommending this, but potential customers should be aware of threaded-on sprockets if they have them.
I think I have one on my 9-footer (old Schwinn Giraffe hub). Not sure at the moment, I’d have to look. In any case, I give the cycle a thorough test, while holding onto something, before every ride. This one only gets used in the occasional parade, so not many miles get put on it, but those miles are high up in only semi-controlled situations.
We don’t know yet if this new Torker has a threaded hub, or if they’ve found a way to make the sprocket real tight. When I bought my Schwinn Giraffe, $129 was the retail price. What’s the big problem?
Based on a single photo I can’t say much about a product, but it does appear to have only about 1.5" of seat post contact around the clamp. This makes that a potentially weak area for heavier riders. Also, all giraffes seem to get the most stress at the bottom of the seat tube. Can’t see what kind of reinforcement is there.
But based on the picture, this new giraffe looks like a great deal for smaller or lighter riders!
This isn’t exactly true. Speed regulation for trackies is virtually identical to unicycle balancing.
Unscrewing a sprocket on a track bike at speed is at least as bad as falling from a giraffe. Probably worse. You’re pretty high up when you are on the bank, and all that kinetic energy has to go somewhere. Also you’re cleated down so there’s no escaping the bike.
And trackies aren’t weak - most of the elite sprinters can push at least 400-500 lbs with either foot. I can think of several races where I was getting boxed in and needed to suddenly move back by a wheel length or two to make my escape. I used full force to resist the pedal movement, which meant that I was using a source of energy more powerful than my legs. I can’t imagine needing or generating that kind of force on a unicycle.
There are two kinds of track hubs with lockrings. The first, and DEFINATELY UNSAFE version has both the cog and the lockring threaded in the same direction on the same set of threads. This system is sometimes used on street fixed gears where the rider has brakes, so John’s assumption is valid. No amount of lock-tite or tightening will keep this kind on the hub if the rider aggressively backpedals. It’s ok for mild speed modulation for mellow lightweight cyclists, but I’d never ride one.
The other kind is the only type approved for track use. The hub has two sets of threads - a larger diameter one threaded in the normal way so that the cog tightens against the hub when pedaling forward. Just outboard of this set of threads the hub diameter decreases and a second set of threads is cut which tightens in the opposite direction. The lockring mounts on this second set of threads
The way to secure this setup is to first get the cog as tight as possible (a couple of spirited accelerations usually does the trick), then use a C-spanner to jamb the lockring against the cog. If the cog tries to unscrew it tightens the lockring further. After a few good sprints the lockring is tightened again with the spanner. Once it’s well mounted there is no need for lock-tite.
So, I don’t know what method Torker uses, but I assume for safety sake it’s at least a real track hub properly installed. If it’s not, if they are using the poor-man’s lockring, then I definately agree with John that it’s unsafe.
That is exactly the type that Schwinn used on their first generation of giraffes. It has two sets of threads with one of them threaded in the reverse direction. It’s not guaranteed not to unscrew on a giraffe. Welding the cog to the hub is the only way to be absolutely sure that it will not slip.
Schwinn’s second generation of giraffes used bolts similar to lug nuts to secure the cog to the hub. This style of hub will not slip and does not need to be welded. Unfortunately Schwinn is no longer making giraffes and you can no longer get that hub.
I was hopeful (and remain hopeful) that Torker would design a better giraffe hub that will not slip. We need one because all of the giraffe hubs available right now are the threaded track style hub. We need one of the giraffe manufacturers to manufacture a hub that will not slip. Something with a bolt on cog or splined cog or something else that will prevent the cog from ever coming loose while riding.
Ahem - bolt on conversion of a disc hub if anyone felt like making their own for a giraffe.
As a very experienced, yet former, track racer I can attest that it is possible to put a screw-on cog on a hub and not have is come off by itself. You just need to put on the lock ring with the proper tool – and grunt a little in the process. I think that the screw-on style is better because you can actually get the cog off to rebuild the wheel should the opportunity present itself. I’m for being able to fix stuff.
Wow! I like that!
That’s the way giraffe unicycle hubs should be made, with the cog bolting right to the hub like disk brake rotors do.
I doubt you could retrofit an existing giraffe with a hub like that. I think the giraffe unicycle hubs are narrower than bike hubs. It might be possible to find a bike hub with a disk brake mount that’s the right width to fit an existing giraffe frame. That would be cool. But then there is also the issue of chainline. It would be pure luck if the chainline remained all in line. Most likely the chainline will be off and will have to be adjusted at the bottom bracket. Unfortunately most giraffes don’t have a bottom bracket that can be adjusted for changes in chainline. But if you’re building your own giraffe you can take all those issues into account and make it all work with that retrofitted bike hub.
I’m for Tommy Morningstar’s approach. It’s much simpler and more maintainable. John, do you have some stories which would say that Tommy’s approach is not the correct one? If so, how do you know the hub and cog were installed correctly?
I’m currently working on two giraffes that have seen a lot of use and haven’t been welded. One is a 6-footer that the owner jump-mounts and does 10+ mile rides on. I haven’t heard a word about the hub giving any problems.
Dustin Kelm has had problems with the cog spinning loose on his Semcycle giraffe. He uses that giraffe for shows and some of his tricks put a lot of back pressure on the pedals (for example, getting out of the side ride). He was Loctiting the cog and lockring, but even that would eventually work itself loose. I believe he now has the cog welded in place.
I believe John Foss has also had the experience of a slipping cog while up on a giraffe.
The cog can eventually slip even if the cog and lockring are installed correctly. The big problem is that you can never be sure if it is still tight until it slips, and at that time you’re SOL. It’s not a safe design.
I have heard Darren Bedford say that he will never sell a giraffe that hasn’t had the cog welded to the hub.
I have a Semcycle hub on my Schwinn giraffe. The cog and lockring are Loctited and they were installed very tightly. That works for me for now but I am going to have the cog welded on one of these days (hopefully before it ever slips on me).
I really like the sure-fire bolt-on cog idea. It will not slip. All you have to do is make sure the bolts are tight and Loctited and the cog will never slip. If you have to replace the cog or replace a spoke or do other maintenance on the wheel you can easily remove the cog. It’s the perfect solution.
Bolting the cog on a disk brake hub is brilliant. Cheers to the guy who thought of that.
John #2 responds:
As experienced track racers, I have no dispute for what those guys are saying about how track hubs work for mondo-powerful track racers. Clearly if those designs were inferior for track bikes, they would be changed. Track bikes are specialty items, and tend to be expensive anyway.
In any case, the danger of a sprocket unscrewing on a giraffe is potentially higher than in a track race. I’m guessing the danger in a track race is a sudden loss of control, leading to possible tangling up with other riders. If other riders are not nearby, the two-wheeled track bike should be able to stay upright.
On a unicycle, without warning, the wheel will roll out from under you. This can lead to a fall without warning, landing in whatever position your body happens to be in. This is a lot worse than a UPD that you at least have a second or two to prepare for.
Once upon a time, a friend and I purchased six old Schwinn Giraffes from an elementary school in Ohio that was no longer using them. I then resold them, but first took them to the bike shop to have the hubs tightened because they were the threaded kind.
What followed is the main fuel for my mistrust of bike mechanics when working on unicycles. I specified “red Loctite” to be used, and for them to be tightened to the limits of their tools and skills. What I got was green loctite, and a sprocket that unscrewed as soon as I tried to rolling-mount it in the parking lot.
This was a well-known and popular bike shop, one of Long Island’s largest. With multiple mechanics on duty most of the time, unicycles were probably always relegated to the lowest-level mechanics; the ones that assemble new bikes or do other basic tasks. I was told green Loctite was used because red was supposed to be permanent.
So I had to explain the job to them again, and wait again for it to be done a second time. But rest-assured, even assembled by a popular bike shop, one of those old Schwinn Giraffe hubs is still a potential problem. The only worse things that can happen on a giraffe are frame or chain breakage. You may get a little bit more warning with a loose sprocket, if you’re paying attention.
Thank you for the input, Johnx2. The one I am working on right now has room for 2 lockrings; that plus red Loctite should be fine. The others I will have to see what is available. Thanks again for some more cognitive challenges!
If you go with the Loctite, use the Loctite primer to clean the threads. The primer will clean off grease, oil, and dirt and will let the Loctite get a stronger bond.
The primer is an acetone based cleaner that also acts as an activator that speeds and improves the curing. It will help guarantee that you get the strongest possible bond with the Loctite threadlocker.
As a mechanical engineer, former track racer and former bike mechanic I can agree with both camps in this discussion.
On one hand, I agree that the multiple bolt-on solution is better for mass produced giraffes maintained by average bike mechanics.
However there is a potential flaw - if the bolt pattern of the cog isn’t perfect then the cog will be excentric on the hub which means the chain will be alternately loose and tight. My experience with this effect on track bikes is disasterous. The mechanic will install the wheel and cranks so that they allow free movement of the wheel at all times. This means that the chain is only at the right tension when the high point of the cog and chainring coincide. When the low spots coincide the chain can, and usually does, come off.
This is one reason why track cogs, hubs and cranksets are expensive. (the other is that there isn’t much demand). I’ve used road cranksets with track bikes with poor success because on a road bike a little excentricity in the chainring is unnoticable.
As for giraffe riders stressing the chain/sprocket combination more than trackies or couriers, well, I still don’t by it. I can easily skid the wheel on my fixed gear, which means that I routinely take the wheel up to and beyond the limits of adhesion. It’s hard for me to believe that any unicycle rider has ever managed to get that much traction on a giraffe. Also, since the torque on the cog is proportional to the wheel radius times the traction forces, even if the were able to bring the wheel up to the limits of adhesion the torque on the giraffe hub would be significantly less. For the same contact patch force the torque at the hub of a 700c wheel is 34% greater than the torque at the hub of a 20" wheel.
Finally, there is the abuse factor. I routinely slide my fixed gear for 20’ or more in emergency stops. Sometimes I’m sliding over potholes and other road defects where the wheel is takes impacts while locked up by the chain and cog. I don’t use lock-tite, and have never had a cog come unscrewed.
Then again, I use reasonably high quality equipment and always do my own work BECAUSE I’ve had cogs come unscrewed when they were cheap or installed improperly. So I do sympathize with the wish to have a fool proof bolt-on solution for giraffes. (You can usually engineer something to be fool proof, but never damn-fool proof.)
Since giraffe riders are unlikely to need to swap cogs between heats for tactical advantage, there isn’t much penalty for welding, bolting or otherwise permanently installing the sprockets IF they are exactly round when finally installed. Trackies DO change gears every now and then (usually by swapping wheels), and good thread-on cog are inherantly well centered, so the double-thread track hub solution is pretty close to optimal for bike use.
I also disagree that giraffe riding is inherantly more dangerous. The turns at the track can be up to 2 stories tall near the top, and a tumbling fall at 40 mph while tangled with other riders is quite a mess. My last serious crash at the velodrome left a bruise on my hip that took a couple of years to completely heal. I think they are both equally capable of putting you in the hospital or worse, so careful selection and setup of equipment is critical.
Thanks for the comments, cyber. So far it seems as though the giraffes I’m working with are of lower quality than the track components, and they are not the best of the track components. Perhaps Dustin and other top performers would do well to look into better hubs (if they are not already) such as the Phil Woods which are running about $150 per hub. The Surly track cog I just purchased for a giraffe appears to be very strong and runs about $30 retail; with the lock ring running about $14. So there may be issues behind these stories such as component quality and installation procedure.
The most important thing to say is: learn to check your uni carefully before you trust your life to it. That’s a good habit for any sport.
Except that you’re forgetting that in a stop a bicyclist, whose weight is distributed over two wheels, has perhaps 1/4 to even 1/6 of the pressure on that wheel that a giraffe rider has. Since the coefficient of kinetic friction for a rubber tire is far less than the coefficient of static friction, it seems clear that a giraffe rider putting a couple of g’s on a lever arm, directly into the ground with no skidding, could go way beyond a track bicyclist in terms of torque on the rear sprocket.
Yeah, it’s hard to say. When I really want to stop I slide back off the seat to get as much weight on the rear wheel as possible, and try to ride at immenent loss of traction. I’m a heavy guy - 220 lbs - and the bike weighs about 20 lbs so there is probably 120 lbs or more on the rear wheel when I really want to stop. (I normally have about a 60/40 weight distribution in level riding. By scooting back I change that to a 70/30, but the decelleration moves some forward so let’s call it a bit less than 50/50.)
Dustin weighs what, about 160? With the giraffe about 200 lbs into the ground? If he gets a 25 degree lean on his giraffe he’s pulling about 1.09g’s, which means a dynamic weight of 218 lbs. I still don’t think he comes anywhere near breaking loose - if he did he’d slide out every now and then - but let’s say he sometimes gets to 80% of max traction. That means he’s working with an equivalent contact pressure of 175lbs. 175lb20" is about equal to 120lb29", so yeah, it does look like giraffe cogs can get loaded up pretty high too. If Dustin rides with someone on his shoulders then he’s clearly got more traction available than I would on my track bike. I’m convinced.
Then again, track bikes sometimes have two riders:
Bottom line is that good equipment properly installed is essential for either one.
BOT, does anyone know if the Torker giraffe has a decent cog and hub? As U-turn says, in the $30 sprocket/$15 lockring range on a hub with decent threads?