Subject:
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Re: building a bicycle -- can it be done?
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Newsgroups:
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lugnet.loc.au, lugnet.technic
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Date:
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Fri, 1 Sep 2000 23:14:19 GMT
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Viewed:
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186 times
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David Eaton <deaton@intdata.com> wrote in message
news:G07p2s.MF8@lugnet.com...
> In lugnet.loc.au, Geoffrey Hyde writes:
> > The biggest problem you will find is that each LEGO Technic gear is one
> > brick wide, except for the smallest one which is slightly more than a • brick
> > wide.
>
> You mean the thinnest tech gear which is about 1/2 a brick wide? :) (the • thin
> bevel gear, that is-- too bad they don't make 1/2 brick wide chain!)
No, I said smallest. Bevel gears aren't the smallest. :)
> > Set up four or five of these side by side and your bicycle is going
> > to look more like an overweight elephant should be using it!! ;-)
>
> Perhaps you could build a FUNCTIONAL one that wasn't "accurate" with a
> transmission and separate chains? 'Course that'd be cheating :)
Possibly. but it would be fun trying methinks.
> > The other problem, even if this first one could be overcome is how to
> > compensate for the sideways forces acting upon the chain links, they • weren't
> > exactly designed to swing from side to side much. Maybe enough for a • small
> > amount of swing, given that you incorporate enough links into the chain, • but
> > for one as large as five studs I would expect more than a few snapped or
> > broken links to result, unless using an unrealistically long chain.
>
> Perhaps a 2-geared bicycle would be possible by setting the 'pedal' gear • 1/2 a
> stud off from the 2 rear wheel gears, thus reducing the amount of side to • side
> motion that would have to be handled by the chain...
Quite a possibility, but you'd have to be ungodly accurate in placement of
the gears to ensure that one gear at the rear doesn't get better alignment
than the other.
> Alternatively, making the pedal gear an equal number of gears to the rear
> wheel gears, and making the derailleur work on both sets might also work.
> Hence, the chain never actually bends from side to side-- although this
> probably makes it more difficult to create the derailliur, since operating
> both pedal and wheel derailleurs at once makes for a stretched chain...
Maybe, but it would perhaps look more like a grinder or log chipper than a
bicycle IMHO.
> > I can quite imagine the gear part for the derailleur mechanism at the • back,
> > though, that would be simple enough to do with a few Technic LEGO pieces.
>
> Agreed-- the mechanism to actually move the chain would be fairly
> straightforward...mostly just difficult to work from the handlebars, but • that
> could be worked out without phenomenal difficulty.
Hmmm - flex cable, maybe? I'm not sure any elements are long enough, and
I'm not sure they can be stiffened enough, even if they're long enough.
> > > How would I get the bike to coast, or would the pedals have to turn • with
> > > the wheels?
>
> I thought about this one a bit, and I think it might be possible using a
> somewhat non-conventional locking mechanism. Of course I'm not a regular
> technic builder, so there might be easier ways to do it, but I've used the
> locking mechanism as borrowed from 6949 (Spyrius Robo-Guardian). Rather • hard
> to describe-- I also used it in my portcullis design for my castle so it • would
> lock in place (and not fall down) when being hoisted, while still going up
> smoothly-- I took a photo at:
> http://www.suave.net/~dave/images/newgate/newgatelocker.jpg
It is kind of a ratchet mechanism. Of course, on a real derallieur bicycle,
the gears at the back are capable of remaining still while the wheel goes
forward.
> But in order for that to work, you would have to attach the locking piece • to
> the rear gear wheels, and let the actual axle to the wheel be free from • the
> gear wheels. Additionally, since you might have to work against gravity, • you'd
> have to put rubber bands on the locking piece to make sure it would lock • when
> needed...
Unless a form of slippable clutch mechanism could be made so that gears on
the gear tower for the derallieur mechanism at the back are able to rotate
independently of the actual wheel itself. perhaps a 4x4 turntable, although
bulky, could be made to do the task? The real problem is finding either
gears or a large wheel which has a smooth inner rotation cylinder. I don't
know of the former, and very few of the latter.
> At any rate, this would allow the mechanism to work similarly to a real
> bicycle: When the pedals were turned, the rear wheel would go forward, but
> when the rear wheel turned and the pedals remained still (or were going • slower
> than the rate of the rear wheels), the pedals wouldn't be forced to turn.
> Additionally, when backing up, the pedals would be forced to turn
backwards...
Ya. Kinda unrealistic I guess. Then again there have been times when I
wished I could pedal backwards - I owned a 10-speed bike once ...
> Of course this is all just speculation at this point, but it's certainly • an
> inspiring project :)
It certainly is!!
> DaveE
>
> p.s is there a reason this was posted to lugnet.loc.au? It would probably • get
> a much better response from lugnet.technic, lugnet.general, or
lugnet.build...
I hadn't noticed that when I responded - my bad ... I'll add an xpost to
the technic group I think.
Cheers ...
Geoffrey Hyde
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Message has 1 Reply:
 | | Re: building a bicycle -- can it be done?
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| I have a solution for the coasting problem. This method allows the wheel to move without the pedals moving and even allows the wheels to move forward if the pedals are moving backwards. The pedals drive one axle of a differential. The other axle of (...) (24 years ago, 2-Sep-00, to lugnet.technic)
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Message is in Reply To:
| | Re: building a bicycle -- can it be done?
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| (...) You mean the thinnest tech gear which is about 1/2 a brick wide? :) (the thin bevel gear, that is-- too bad they don't make 1/2 brick wide chain!) (...) Perhaps you could build a FUNCTIONAL one that wasn't "accurate" with a transmission and (...) (24 years ago, 1-Sep-00, to lugnet.loc.au)
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