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#31
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"Liquid Drive" bike prototype at auction
In rec.bicycles.misc Carl Fogel wrote:
: Is the length of the chain-run a problem? That is, : are longer chains less efficient, harder to shift, : more prone to wear? Triple the cost and weight of the chain... Many recumbents use an idler wheel or two to manage the peculiar chain routing. I would think this eats some efficiency, maybe a percent or two? Then again some efficiency might be regained since the chainline from chainring to cog is relatively straight. All in all I'd consider it a minor issue in upright-to-recumebent comparisons. -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
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#32
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"Liquid Drive" bike prototype at auction
"Dave Kahn" wrote in message
... Tandem sprinting is spectacular. See www2.ijs.si/~mleskovar/tandem1_2.jpg I certainly feel sorry for the stoker on the Japanese team in this photo. Shouldn't he have a little more ... headroom? |
#33
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"Liquid Drive" bike prototype at auction
Carl Fogel wrote: Ryan Cousineau wrote in message ... [massive snip] That's just the trick. Chain is so good, it defeats all other options. You use belts or enclosures if the filth bothers you, but that's it. Maybe some recumbents would benefit from a long, stiff shaft drive, given their ludicrous chain issues. Dear Ryan, I love ludicrous issues. I occasionally see recumbents wobbling along on my local bicycle path, but have never inspected a dead one's anatomy--possibly there is a secret recumbent graveyard. Is the length of the chain-run a problem? That is, are longer chains less efficient, harder to shift, more prone to wear? Or is it the peculiar arrangements rather than the mere length? Are recumbent chain problems worse than tandem chain problems? Any concrete answers or even wild speculation will be appreciated, since I'd hate to shoot such rare creatures just to dissect their chain anatomies. I can recall only a single tandem sighting in fifteen years and fear that they may be extinct in these parts. J.J. Audubon Go for a ride in or outside Victoria BC on a beautiful day. You will see tandems flying past in their miriad colours, in harmony with the "single" bikes of greater number. Bring your binoculars, and your bicycle watching experience will be enhanced. - there are birds too, if you like watching them as well. Bernie |
#34
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Recumbent bikes (was: "Liquid Drive" bike prototype at auction)
Tom Sherman wrote in message ...
Carl Fogel wrote: Ryan Cousineau wrote in message ... [massive snip] That's just the trick. Chain is so good, it defeats all other options. You use belts or enclosures if the filth bothers you, but that's it. Maybe some recumbents would benefit from a long, stiff shaft drive, given their ludicrous chain issues. Dear Ryan, I love ludicrous issues. I occasionally see recumbents wobbling along on my local bicycle path, but have never inspected a dead one's anatomy--possibly there is a secret recumbent graveyard. Recumbent owners keep their bikes forever. There are no low quality/low price recumbents (equivalent to discount store bikes) and the majority of commercially produced recumbents were made in the last 10 years. Therefore, unlike upright bicycles, one is unlikely to find recumbents in dumpsters, along the curb, at police auctions of abandoned bikes, etc. Is the length of the chain-run a problem? That is, are longer chains less efficient, harder to shift, more prone to wear? Chain wear mainly occurs when the tension (power) side of the chain is bent around the drive cog(s). Since recumbent chains are generally much longer, they typically last much longer (assuming similar conditions of use). I suspect that the cost per unit distance for recumbent chains does not differ significantly from upright chains. Shifting quality on a recumbent depends primarily on the quality of derailleurs, shifters, cassettes and chainrings used. An advantage of RWD recumbents is that the chain angle is lessened when the driven cog does not line up with the driving chainring. One can get away with using cross-gears much more so than on an upright. On the downside, recumbent shifter cable runs are typically longer and more convoluted than those of uprights are, and this can impact shifting in a negative manner. Small drivewheel bicycles that use larger than normal chainrings generally have poorer shifting quality - this is true of both recumbents and small wheel uprights. I had 73/52 chainrings on a bike I used to own [1] and front shifting was not the best. This is compounded by the lack of large chainrings with ramps and pins. My current bike uses a clever step-up jackshaft to avoid this problem and has excellent from shifting. [2] Or is it the peculiar arrangements rather than the mere length? For reasons of aerodynamics (reduced frontal area) and power production (angle formed by the seatback, seat base and BB) unfaired performance recumbents have the BB located higher than the seat. A direct chain run from the BB to the rear sprocket(s) would pass through the rider. Therefore, some combination of mid-drive, jackshaft, chain idlers, chain tensioners and chain tubes is required for chain routing. Any concrete answers or even wild speculation will be appreciated, since I'd hate to shoot such rare creatures just to dissect their chain anatomies. I can recall only a single tandem sighting in fifteen years and fear that they may be extinct in these parts. J.J. Audubon [1] http://www.ihpva.org/incoming/2001/wbone2.jpg [2] http://www.ihpva.org/incoming/2002/sunset/Sunset001.jpg Tom Sherman - Planet Earth Dear Tom, You know how to pander to my chain fantasies. It's so much easier to ask than to think. I'd never thought about how a longer chain should last longer and cross-chain with less angle between the front and rear sprockets. Your two pictures delight me, though perhaps not in the way that you intended. I feel like someone who's never seen anything but labradors stumbling over his first basset hound. Those (no offense intended) are some weird-looking bikes. The recumbents that I see in my little backwater in Pueblo, Colorado, must be the equivalent of the inexpensive mountain bikes sold at WalMart. The riders sit higher, their feet are lower, the wheels are larger, and the chain runs seem much more straightforward than that Rube Goldberg contraption in your second--I mean your beloved current bike, the one in your second picture. If you'll pardon a somewhat personal question, do the chains on the more complicated bike give any trouble in terms of staying on? That is, do you need some recumbent-specific chain-watchers to tame the unruly beasts beyond the guide-wheels? Thanks for a marvelous answer, Carl Fogel |
#35
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Recumbent bikes (was: "Liquid Drive" bike prototype at auction)
Carl Fogel wrote: ... The recumbents that I see in my little backwater in Pueblo, Colorado, must be the equivalent of the inexpensive mountain bikes sold at WalMart. The riders sit higher, their feet are lower, the wheels are larger, and the chain runs seem much more straightforward than that Rube Goldberg contraption in your second--I mean your beloved current bike, the one in your second picture. This bike fits your verbal description. http://www.easyracers.com/gold_rush.htm It is one of the classic recumbent designs, but is hardly "x-Mart" in quality or price (you can get a rather nice road bike for $3000 US). Both my former and current bike are rare and unusual by even recumbent standards - however they provide a good illustration of chain management issues. If you'll pardon a somewhat personal question, do the chains on the more complicated bike give any trouble in terms of staying on? That is, do you need some recumbent-specific chain-watchers to tame the unruly beasts beyond the guide-wheels? The Wishbone (nickel-plated bike) had the worse chain management, as the chain would fall off the idlers at a distressing frequency. This could have been cured by a different idler design that included a "chain dog" which is a pin or plate that forces the chain to stay in the idler groove. Most regular production recumbents have these (this bike was more of a prototype). On the Sunset (red bike) the chain(s) can fall off the jackshaft cogs http://www.ihpva.org/incoming/2002/sunset/Sunset005.jpg although that is a rare occurrence. This is the one weak point in the bike's design as far as I am concerned, and something I plan to have corrected at some point. Thanks for a marvelous answer, You are welcome. Tom Sherman - Planet Earth |
#36
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Odd bikes
Why are tandems more popular in some places while not in others?
This year I've spotted 2 recumbents, 3 upright trikes, 1 folding bike in the wild (only counting sightings in Finland). Don't recall seeing a tandem ever. -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
#37
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Recumbent bikes
In rec.bicycles.misc Carl Fogel wrote:
: The recumbents that I see in my little backwater : in Pueblo, Colorado, must be the equivalent of : the inexpensive mountain bikes sold at WalMart. : The riders sit higher, their feet are lower, the : wheels are larger, and the chain runs seem much : more straightforward than that Rube Goldberg Not necessarily, they sound more like touring bents by your description. Go read some recumbent websites (there's plenty) for info on all the designs out there :-) -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
#38
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Recumbent bikes (was: "Liquid Drive" bike prototype at auction)
(Carl Fogel) wrote in message . com...
You know how to pander to my chain fantasies. It's so much easier to ask than to think. I'd never thought about how a longer chain should last longer and cross-chain with less angle between the front and rear sprockets. Your two pictures delight me, though perhaps not in the way that you intended. I feel like someone who's never seen anything but labradors stumbling over his first basset hound. Those (no offense intended) are some weird-looking bikes. The recumbents that I see in my little backwater in Pueblo, Colorado, must be the equivalent of the inexpensive mountain bikes sold at WalMart. The riders sit higher, their feet are lower, the wheels are larger, and the chain runs seem much more straightforward than that Rube Goldberg contraption in your second--I mean your beloved current bike, the one in your second picture. If you'll pardon a somewhat personal question, do the chains on the more complicated bike give any trouble in terms of staying on? That is, do you need some recumbent-specific chain-watchers to tame the unruly beasts beyond the guide-wheels? Thanks for a marvelous answer, Carl, I'll entertain you with a few more pics. http://www.biketcba.org/TRICORR/vrex2.jpg http://www.biketcba.org/TRICORR/mgruizenga.jpg The first one is of my slightly customized V-Rex. It has a pretty straight chainline, with only one power side idler to prevent too much chain slap. It's never come off, although it once jumped the return idler by the fork. It has an ISO 507 (24") rear wheel and an ISO 451 (20") front wheel. This model is considered a 'sport' model, and it's the equivalent to a mid-level road bike. Both of Tom's bikes would be considered 'faster' bikes. The 30/44/56 chainrings shift a little balkily, but as Tom wrote, larger rings do that; and it spends most of its time in the big ring anyway. OBTW it takes about two and a half chains , which seem to last about 10,000 miles. By far the most common recumbent model in my club is the TourEasy. The second pic is of one of the club members on his aluminum-framed model. These bikes have the rider sitting more upright, but they are made to be used in conjunction with the fairing you see. Keeping the rider relatively close to the fairing helps aerodynamics, so the bike you see is not slow. In fact, the speed demons of the club put body socks on the bikes, in effect making lycra-bodied streamliners. They ride with the 'A' riders in a swarm, like jet fighters protecting a bomber squadron. The smell-the-roses riders like this model too, because the low pedals make it easy to ride; so if you see one going slow, consider the engine. TourEasys have no power side idlers, so chain deflection, even in the extreme gears, is almost unnoticeable. To relate back to the original subject, I for one would rather continue to deal with chain routing than to lose efficiency or gain too much extra weight with a hydraulic drive system. |
#39
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Odd bikes
wrote in message
... Why are tandems more popular in some places while not in others? This year I've spotted 2 recumbents, 3 upright trikes, 1 folding bike in the wild (only counting sightings in Finland). Don't recall seeing a tandem ever. Darned if I know. But I do know that the best bad-winter-weather tires seem to be made in Finland (Nokians), and that tandems are, in general, a fair-weather bike. Maybe there's the connection. |
#40
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Recumbent bikes (was: "Liquid Drive" bike prototype at auction)
Tom Sherman wrote in message ...
On the Sunset (red bike) the chain(s) can fall off the jackshaft cogs http://www.ihpva.org/incoming/2002/sunset/Sunset005.jpg although that is a rare occurrence. This is the one weak point in the bike's design as far as I am concerned, and something I plan to have corrected at some point. The rear chain on my Sunset falls off to the inside of the jackshaft cog almost every time I coast on a rough, high speed descent while in the smallest rear cassette cog. This is due to a combination of the chain line and having the lowest chain tension when in the smallest cog. I'm using a Dura-Ace short cage rear derailer. So once I stop pedalling on a descent (usually 50-60 km/h range) I shift to a larger cog towards the middle of the cassette and coast. When I want to pedal again I start pedalling and simultaneously shift to the smallest rear cog. The real solution is to put chain guard discs to each side of the jackshaft cogs. Interestingly when the chain falls off the jackshaft cog it sits on a collar next to the cog and I'm able to reach down with my right hand and put the chain back on the cog. I've done this at speed several times, in fact twice on one descent last weekend when I was riding with a tandem. I told them I lost the engine as I reached down and put it back on the cog. I don't like taking a hand off the handlebars on a rough descent though and it gets my glove dirty. Normally for a hilly club ride I'd be riding my Bacchetta Aero which has much better chain management along with lower weight, less rolling resistance, superior aerodynamics, a smoother ride and a higher seat height which makes it easier to talk with riders on conventional bikes and also more traffic friendly on roads with poor sight lines and/or lots of SUV's. I wasn't riding the Aero on the ride last weekend as it wasn't one of the faster paced rides and I wanted to get a reasonable workout plus I was expecting some wet roads and my Sunset has mudguards while on the Aero there really isn't provisions for mounting them, at least on the low clearance carbon fibre road bike fork. You can see the Aero at www.bacchettabikes.com. Zach Kaplan |
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