Thorn Cycles Forum
Technical => General Technical => Topic started by: Andre Jute on October 25, 2019, 11:20:19 pm
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Found on another bicycle thread:
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FIRST POSTER: Coaster brakes are really just drum brakes, the hub is the brake drum. A lot of benefits to drum brakes that you don't get with disc brakes.
SECOND POSTER: Neither shalt thou bring an abomination into thine house, lest thou be a cursed thing like it: but thou shalt utterly detest it, and thou shalt utterly abhor it; for it is a cursed thing.
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Heh-heh!
That's how I feel about overly sudden brakes, why I prefer the absolutely limpest version of Magura's rim hydraulics (the HS 11 from about 10 years ago; today the HS 11 applies the same pressure as the HS 33, just differently packaged, which I consider a retrograde step), which are ultra-progressive, that is, quite slow to reach their very high calliper grip level, so that you don't take a face-plant every time you brake, as with many discs and Shimano's roller brakes from about the -70 forwards, but come to a good firm stop within an amazingly short distance-to-initial speed. "Limpest" is of course relative: the HS 11 that I have in my standard "just jerk the brakes full on" style, at the end of its progressive retardation will still stop suddenly enough in the last few feet to tilt you out of the saddle when you have to put your feet down, but that's an advantage.
I hate devices which don't serve me, which demand more attention than I'm willing to give them, which demand that I prove my skill every minute I'm on or in them. That's one good reason why I think the Magura rim hydraulics in the lesser (non-racing) versions are the best bicycle brakes ever made.
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...I hate devices which don't serve me, which demand more attention than I'm willing to give them, which demand that I prove my skill every minute I'm on or in them.
Just a different perspective than mine, as that's where and how I achieve my greatest satisfaction, from developing the skills needed to master devices I've deliberately chosen to challenge me. There's such satisfaction in bringing my skills up to the necessary level, keeping them there and then reproving myself and my mastery with each and every use. There's an added satisfaction in knowing someone else can't immediately prove such mastery unless they put in the necessary time and effort, a bit like knowing how to double-clutch or heel-and-toe downshift a car's manual transmission cleanly at speed.
That's one reason why I chose to install Scott/Pedersen SE self-energizing cantilever on the front and rear of my favorite gravel and randomness bikes. Each arm pivots on a helix with adjustable precession and mine are set to the max. The helix provides the equivalent of power brakes as the forward movement of the rim also draws the pads more tightly inward. SunTour later marketed a tamer version with less aggressive helix especially and then finally in a rear-only version in the later years of production but I prefer the originals and love how the allow me to perform "stoppies" (rear-up wheelies under braking) from high speeds. It's a fine edge, stopping with control with that much forward weight bias, but that's the joy in the skill. It makes my other bikes feel dead under braking, but they're not meant for such use.
Similarly, I was deeply into "carving" turns at speed back in my uni years, when all my tire sidewall labels were scuffed from the extreme lean angles. Remember the magazine ads for Avocet road slicks that showed Jobs Brandt cornering at speed? Like that, and for no reason other than the challenge, satisfaction, and thrill of pulling it off.
All the best,
Dan.
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Horses for courses, Dan; more precisely a difference of outlook. If we let the machines challenge us instead of serving us, soon Skynet will take over.
I've seen that photo of Jobst before, for which thanks, though I didn't know it was used for Avocet advertising; casts a new light on a man I admire. That photo shows Jobst working in a parking lot, testing and developing the innovative gear he suggested to Avocet. He had proved everything he needed to prove when he designed the brakes for the Porsche grand prix racer.
I take one look at those narrow, highly inflated tyres on Jobst's Cinelli, and I say, "Rather his coccyx than mine!"
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It's serendipitous that you publish precisely that photo, because I've been spending the last week thinking about leaning suspensions on three-wheelers, which are basically bikes with an extra wheel, and which would transfer the feel of a bike to a more stable base as a non-leaning tricycle cannot. Two wheels at the front of course, one at the back. I have no taste for the instabilities of a single front wheel on a tricycle. Like Jobst used to say, "When your front wheel goes, it's too late for you to do anything."
Have a great weekend, Dan.
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Horses for courses, Dan; more precisely a difference of outlook.
Exactly! :) I've been spending the last week thinking about leaning suspensions on three-wheelers
General Motors and Mercedes did a lot of research in this area. Merc's F300 and F400 Carving, Nissan's design studies make for good reading and viewing, even a Piaggio tilting narrow tadpole that made it to market is fun to see. One of the quickest ways to get there on an existing bike is the TreGO attachment: https://www.kickstarter.com/projects/1919966976/trego
Have a great weekend, Dan.
You too, Andre. All the best, Dan.
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Why would anyone on tight turns test road slick tires without wearing knee pads, helmet, gloves, or anything like that?
My early 60s vintage Italian bike had a very low bottom bracket compared to my other bikes. The bottoms of my Campy pedals were visibly scuffed.
As were the foot pegs on my late 1960s Triumph 500 motorcycle.
I am less in a hurry these days.
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As were the foot pegs on my late 1960s Triumph 500 motorcycle
On the matter of lean angles on 2-wheelers, there's a famous foto of Hailwood on the Honda six, taken around 1967, with the caption, "I don't know much about them really, just the basics."
Me, I was content to just watch.
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Thanks for quoting me, from that I noticed that I had said "food" pegs instead of foot pegs, now corrected. Perhaps I was hungry when I wrote that.
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Hailwood was a treat to watch -- but not to emulate unless you really needed a close-up acquaintance with the brambles lining the B roads.
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One of the quickest ways to get there on an existing bike is the TreGO attachment: https://www.kickstarter.com/projects/1919966976/trego
Clever idea. My roads are so unevenly surfaced and potholed that I need full-size wheels and fat tyres.
Seams to me two complete forks with wheels and tyres and brakes solve a lot of problems and permits the ideal of mounting the "leaning parallelogram" mechanism above the centre of the tyre to eliminate scrub and displacement of the wheel and lowering the bike body, which all attend small wheels and short or split parallelogram arms.
There's an exhaustive introduction to the practical geometrics (high weight of ideal system, keeping stuff out of the airstream inside the body, and so on) underlying a tilting velomobile suspension decision at
https://www.youtube.com/watch?v=4vtOcou_qXQ
which I can highly recommend, except that the fellow obviously never taught because he goes at such a rate of knots that he covers the entire subject in 14m35s; I had to go back several times to catch the full value of valuable points he threw out casually at a speed flattering to his audience's intelligence but I fear in overestimation of our speed of comprehension. If I were teaching tilting suspensions at college, I'd spread the subject across at least a semester. In my own book, DESIGNING AND BUILDING SPECIAL CARS, for lack of space in even a substantial book -- on which all the reviewers noted approvingly that I gave a good deal of space to suspensions -- the subject of tilting suspensions isn't even mentioned, except for a glancing remark and a single illustration about the arguably related sliding pillar system once used by Lancia but today used only on a few deliberately eccentric Morgans.
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On tilting tricycles, here's some nifty work: https://www.wuwm.com/post/uwm-students-are-trying-build-better-recumbent-trike#stream/0
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Thanks, Jim. I'm not sure what it is that those college kids, and their instructor, patented or intended to patent. I didn't see anything new there.
I also suspect that their design of four parallel arms parallel to the diamond frame and mounted on it, is much, much heavier for strength than the purer design of two straight, vertically parallel tubes straight across the bike between the front wheels, in which case they could put the two tubes across the bike above the tires so that the outboard pivots fall directly over the centreline of each tyre, which is desirable for tyre longevity; they already have the cost of making up two special spindles, so they might as well have made them longer to put the pivots in line above and over the centre of the tyre. However, even that is unnecessary: If you imagine taking two complete bicycle front ends of a fork with tyre and brake fitted, and the steering tube standing up uncut, you don't need to manufacture spindles: you have them already, and their swivel falls directly above the centre of the tyre's contact patch (or as near as other desirable geometrics dictate). Zero scrub. Magic. Now insert a piece of head tube over each steerer tube and attach in the normal manner with normal bearings and a headset kit and stem, pivot the leaning cross-bike tubes on the two head tubes top and bottom at each side (say on pre-installed studs), and attach the centre of the central upright to the head tube on the diamond frame (ditto), and the suspension is done. For steering attach an arm between each side's stem to the stem on the steerer tube attached to the diamond frame, and you're done -- and you've avoided a whole bunch of manufacturing costs by simply using standard, mass-produced, cheap bicycle parts. In the design solution as I just laid it out, I also think those students could get away with not hard-triangulating the virtual wishbones (in their design they must make four swivelling links very stiffly restrained in the horizontal direction by a heavy choice of materials and fixings or the thing will aim itself and bend all over the place, which will make for surprising steering inputs, to say the least!) by simply making the steering roads a bit stiffer than normal and placing them at the correctly angle -- after all, on a bike, any bike, not just a tilting bike, the steering falls naturally on the centre-line of the bike which is also ground zero for the purest tilting geometry. All the rest is refinement: for instance, at the outer ends of the steering arms a measure of isolation from road irregularities is easily built in by threading the steering rod, fitting a Ford exhaust hanger rubber between large washers, and clamping the rubber in the stem we fitted earlier, now doing duty as an offset steering arm. Voila, isolated steering.
A standard upright diamond frame makes all this much easier to understand and construct than the chimera of a reclining frame and the myriad problems it inevitably brings with it, which all detract from what they're trying to achieve.
I don't see that you need the complications of Ackerman steering if the two front wheels tilt scrub-free and the two front wheels are no further apart than is necessary for stability.
The simplest design for a lean-lockout for parking the bike or holding it at any desired angle, for instance for mounting, which those kids are still looking for, is a quarter of a brake disc plus a calliper with an on-off switch: a common over-centre lever like on quick releases will do the job and needn't weigh much either. Disc quarter fitted to leaning mechanism, caliber fitted to main bike frame, or the other way round in the event that the brake calliper is lighter than the section of brake disc. For those who aren't into leaning bicycles, they have a natural tendency to fall over because that is inherent in their design, and the purer -- less compromised -- the design, the less stiction there is to hold them up, so a mechanical or hydraulic lock is required. What in normal riding holds them up or in a controlled lean is the gyroscopic action of the wheels.
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Unfortunately, after giving this enough thought to be able to offer a workable solution, inspection of my lanes leads me to the conclusion that however I scale a tadpole tricycle, it will be the wrong size. Here's a photo of a road I ride often, actually a lane: though it carries two-way traffic, it is only wide enough for one car; even to pass a bicycle, the driver must put two wheels into the ditch.
(http://www.coolmainpress.com/miscimage/Irish%20lane%2C%20good%20for%20cycling%2C%2024%20Feb%202019%20800pxw.jpg)
You can see from the wear on the tarmac that a car pretty much straddles the road. No tricycle will have enough articulation to drop a wheel into the ditch and come out of it again.
Now consider a lane even narrower, well crowned, with a small but irregularly deep ditch on each side, and hedgerows of gorse (thorny enemies of cyclists) brushing the sides of cars. But that isn't the worst of such farm lanes. It's the grass hump in the centre. A wide tadpole type tricycle, in the normal layback position, won't make it up the hills common on such farm lanes. An upright trike will have to be either built wider than optimal in order to straddle the grassy middleman where the central rear wheel will find irregular traction on the central grass when wet, or too narrow to bother with to fit on one track, while the rider will still constantly be in danger of dropping a wheel into the ditch and ending up in the gorse.
Still, it was an interesting mental exercise while it lasted. Thanks to all for thoughts and links.
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Here's a fun video arguing that gyroscopic forces aren't necessarily what keeps a bicycle upright:
https://youtu.be/2Y4mbT3ozcA
The folks with that tilting tricycle are fiddling with some of these principles & that's what would be new.
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Andre,
The Yamaha Niken is worth looking into. Their engineering is very interesting.
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Thanks, Jim. There were too many comings and goings in my study to concentrate, so I'll watch that video again.
Macspud, I found the Niken by wondering why Honda would suddenly come up with a tilting Gold Wing sister bike called the Neo Wing -- were they rushing in to counter opposition? They were.
Of course you won't need such monstrous cross-bike arms on a pedal-cycle as those powerful bikes require (see the photo below), but the Niken application, which is obviously costly, is much purer (less scrub) than the Honda application, which, if the patent is any guide, is going to cost a pretty penny itself to deliver less. Here's the Honda patent, with nearer bike weight tubes; scroll down past the boring stuff to the patent drawings themselves:
http://www.hondaprokevin.com/new-honda-motorcycles-neowing-3-wheels-reverse-trike-bike
And here's a naked Niken, actually a better design even if it will look odd for a year or two until we get used to the empty space between the wheels, where if I were going ahead with a bicycle proto (I'm not, you need bigger lanes than mine to ride such a bike in) on my bike I would fill with a luggage platform.
(https://mcn-images.bauersecure.com/pagefiles/645718/niken-28.jpg)
from https://mcn-images.bauersecure.com/pagefiles/645718/niken-28.jpg
Must say, that mess of tubing and wiring wouldn't go too well on a pedal bike.
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There are some videos of tuned Nikens being thrashed around a race track by motorcycle racers and they are all impressed. There is also a guy (French IIRC) who has added a turbo to one, he goes totally nuts on it, he just loves it. Yamaha did a great job engineering it.
Thanks for the link, I'd not heard of the Neo Wing before. The Gold Wing is surprisingly fun to ride for a 1/3 tonne armchair. lol. I had a one for a couple of weeks twenty-odd years ago. I was out for a ride with one of my mates on a lovely windy road, when we stopped for a brew he was saying how impressed he was with how it appeared to be handling the twisty bits. After the brew stop, before setting off again, he was looking around the bike and while he was looking at the wear on the back tyre he was ribbing me a bit, saying that I should try a bit harder. I was thinking that might not be the best idea with a borrowed bike and said that I was at about my happy limit. He carried on ribbing me for a while until he got round to the front tyre, there was a sudden shift in his demeanour, he just said "you're right, don't try any harder. you've already found the limit.". I went to see why the change in his tune. The visible wear pattern on the front tyre extended across the full tread and then about halfway up the sidewall. An awful lot of weight for a fairly skinny front tyre. It would maybe be improved with a twin front wheel setup. For cruising in luxury comfort, which is what it's built for, it was great. It even had the stereo linked to the speedo which got louder or quieter depending on speed.
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Heh-heh. I was looking into the Gold Wing with the idea of turning it into a leaning three-wheeler, just for the hell of it, and because it would be easier to prototype what I had in mind on a powered frame than on my bike, which would follow; meanwhile I wouldn't be wrecking the irreplaceable historic paintwork on my bike with elimination experiments. But there's no point when Honda will have a production model next year, and the Niken is already available, and several pretty powerful three-wheel tilting scooters too, none of which I knew when out of the blue the idea of turning my bike into a tilting three-wheeler came to me. Anyway, the last time I had a big bike, the biggest Laverda, was in the 1960's, and in Ireland there's an onerous graduated process of getting a motorcycle license, which people over seventy probably (I haven't looked into it in detail) need to go though again every year. Duh, that's too much trouble. The solution, to make the front track wide and use the thing with a car driver's licence, makes tilting wheels irrelevant, as their main purpose is stability, which a wide track automatically provides. Anyway, taking a tape measure to some of my favourite rides in the lanes soon demonstrated that two wheels in tandem is the optimum bike configuration for me, and that the girth of the Gold Wing, even with only two wheels, would be more of a menace than a pleasure (the rear wheel would be constantly on wet grass or, more likely, sliding off it unpredictably onto high-friction tarmac -- ouch). Your experience is another data point on a right decision. And some fascinating bike research has come up, inter alia in the links Dan and Jim posted.
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Andre,
I realize you're now off the idea of a three-wheel conversion and I grok the reasons why. However, I finally re-found some relevant links to a conversion product so I'll include them here before they again sink into the obscurity of my larger links collection:
Videos:
https://www.instagram.com/stories/highlights/18021673069232156/
https://www.instagram.com/p/B4w6g-gAH1-/
Stills:
https://www.instagram.com/leventvebisikletleri/
https://www.instagram.com/p/B4u0N39gHT7/
https://www.instagram.com/p/B4t7DLYAoIy/
https://www.instagram.com/p/B4ryeM1Al5Q/
The Turkish caption translates roughly to...
Hello new beauty handmade 3-wheeled custom... With 47 staff, the front luggage part of the bike can be removed and the bike can be made with 2 wheels... Another beauty of our bike is that the front wheels can be used inclined at a certain angle 'when driving' or 'in turns'. This provides an extra driving pleasure. You can also use the front luggage part as a market car if you like... Shipped all over Turkey, let our pedals be plentiful.
This appears to be a simpler, Turkish homebuilt version of the Trego setup I linked to earlier in this thread. Tantalizing in its apparent simplicity, the track is remarkably narrow and looks as if it could be made narrower yet. As it is, the overall width looks no wider than your rack-mounted baskets, though they of course skim above the ground rather than run on it, so even this narrow track might be impractical on your roads. It is nice how it simply replaces the front wheel and attaches to the fork's dropouts and canti brake mounts, leaving the bike ready to convert back to its original form. I don't see front brakes, but some front discs or perhaps drum-brake hubs would address that shortcoming nicely. I have no connection to the product.
• Of tangential interest might be this attempt to DIY a leaning cargo trike: https://www.instructables.com/id/fail-a-full-tilting-3-wheeled-cargo-bike/
• Seen this one?: https://www.bikeforums.net/utility-cycling/1094508-front-end-kit-2-wheels-front-cargo.html
• Otherlab ( https://www.otherlab.com/home/#current-projects ) has a tilting "inflatable car": https://www.otherlab.com/blog-posts/inflatable-cars
• Have you seen the Harley-Davidson TRiO conversions?: https://www.tiltingmotorworks.com/bike/harley-davidson-trio-kits/
Three-wheelers do have a problem handling irregular road surfaces; unlike a bicycle's single track, a tricycle has three. Back in 1982, I tried the Vector HPV intended for record attempts and found it fairly miserable to ride in the real world not because of its focus but because it was almost impossible to avoid potholes -- what one or two wheels missed the other(s) fell into: https://books.google.com/books?id=ldgDAAAAMBAJ&pg=PA87&lpg=PA87&dq=early+winters+human+powered+vehicle&source=bl&ots=AC8C57u29T&sig=ACfU3U3IZE6YMdh1PixTCa_3WErpHOEIOw&hl=en&sa=X&ved=2ahUKEwjS7On6neblAhUTFjQIHQFuCyIQ6AEwAHoECAgQAQ#v=onepage&q=early%20winters%20human%20powered%20vehicle&f=false My Dutch friend reports the same shortcoming with his three-wheeled Quest Velomobile when used on rough roads.
Best,
Dan.
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Dan. that's a super lot of links. Maybe I'm just slow in my sunset years, but that spring between the two top tubes seems to me to be merely decorative. It can't have much, or indeed any, bracing function.
The best of the lot is still the Trego you linked earlier in this thread; I really like its multi-functionality. What I don't like is non-standard 16" wheels when 20" are so easily available. But it seems to be thoroughly designed and engineered by someone who has done his homework. The suspension geometry is not perfect, and the two cross-body tubes have had to be made pretty heavy because they're so close together, and not triangulated at all, but that is probably a compromise for luggage capacity.
Your remark about my pannier baskets is apt: The idea of a tilting tricycle is to make it no wider than the handlebars. Also I liked your remark about designing a trailer so that two wheels follow each other. If applied to a tadpole tilting tricycle, that would solve the dangerous problem of the grassy middleman on many of my favourite lanes. Of course, it would complicate the design to an extent I haven't had time to consider beyond the obvious that the rider would when leaning out of the two-wheel track side be lending a considerable part of his weight to an overturning lever.
I didn't start down this road because of my balance. My balance is in fact better on the bike than on my feet, and my reflexes are still those of my twenties. I merely had an urge to buy a Gold Wing, and thought I'd turn in into a tilting three-wheeler merely for interest (which idea evaporated when I discovered that Honda will be marketing a tilting tadpole Neo Wing next year -- and anyway the Tilting Motor Works already have well-developed kit as on the Harley you reference, cutting into the opportunities to license a new design) and perhaps then on my bicycle. The idea was that a powered proto would be easier to develop than a bike proto. When I was younger, I would have ordered the Gold Wing the next day, but it is just as well I plan better these days, because I also discovered that I would have to go through a very time-consuming process even to get a big-bike license, and at my age have to renew it at inconvenient intervals. If you make a tadpole wide enough to drive on a car license, you also lose the need for a tilter, and whatever you do on such a wide vehicle isn't transferable to a bicycle used in the lanes, so self-defeating of me. The bicycle is very important to my life, in the most literal sense of exercise and fresh air contributing beside the chemicals to keeping me alive. There the project died as a practical prospect for lack of application to my lifestyle, so to speak, though of course I still have an intellectual interest. The truth is that any time I give to motorised pursuits will probably cut into cycling possibilities -- and I know which do me the most good!