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'[OT]: Bike gear ratios'
2002\11\22@173030 by Jinx

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> Apparently there is a french company called Mavic Mektronic that
> makes an electronic gear change system for bikes with Derailleur
> type gears. Uses a push button on each handle bar, one for up, one
> for down shift - F1 paddle change style

I'd heard about something on the market but hadn't looked into
it too seriously, thanks for the link. I reckoned a couple of steppers
with worm gears could do it, kind of like machine heads on a guitar,
there's not that much tension in the wires

> see http://www.bikyle.com/mavic.asp Apparently uses the energy
> in the drive train to do the shift so they don't need large batteries
> and actuators. Not sure I would want one at that price though.

Exactly. There's "being a prat" and "being a prat with too much
money". Being able to do smooth transitions up through the gear
ratios isn't really the end of it in suburban cycling, but it would help
on a clear road

NZ$1500 ? Aye chihuahua

> A search gives lots of sites with reviews, which all seem to be
> glowing brightly :))

Parts of me used to glow brightly too ;-) Rudolph The Red-Nosed
Reindeer ? Ha, you amateur

What strange directions threads take

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2002\11\23@055458 by Peter L. Peres

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On Sat, 23 Nov 2002, Jinx wrote:

*>> Apparently there is a french company called Mavic Mektronic that
*>> makes an electronic gear change system for bikes with Derailleur
*>> type gears. Uses a push button on each handle bar, one for up, one
*>> for down shift - F1 paddle change style
*>
*>I'd heard about something on the market but hadn't looked into
*>it too seriously, thanks for the link. I reckoned a couple of steppers
*>with worm gears could do it, kind of like machine heads on a guitar,
*>there's not that much tension in the wires

Last time I used a bicycle and tinkered with the derailleur gear mechanism
I found out the hard way that the wire tension is 3-4kgf-ish.

The force required for the torpedo-style (in-hub) gear changers is much
lower, but with 2kgf peaks and some continuous tension.

Peter

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2002\11\25@172429 by llile

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While on the subject of bikes, I have a project I have been kicking
around.  I've built a number of recumbent bikes, some with underseat
steering and some with a conventional handlebar on a really long
gooseneck.

The long gooseneck models are easy to build, but suffer from excessive
weight.  The rider can pull very hard on the handlebars, and so I end up
beefing up these components so they weigh quite a lot.  Also, brake cables
become excessively long, and the back brakes hardly operate at all because
they stretch.  This is also sometimes a problem on tandem bikes with long
cables.

Underseat steering solves both problems nicely.  The handlebars are under
the rider's seat, brake cables are shorter than a regular bike and thus
stiffer.  Another advantage is the arms hang at a natural angle.  Folks
like me with carpal tunnel appreciate it when our hands are used in
relaxed, natural positions, as opposed to bearing weight on a regular
bike, or up in the air.

Underseat steering has one complication that is a showstopper, though. You
must have some linkage from the handlebars to the front wheel.  I have
used cables, rods, and various other things.  Any play in this system can
result in wierd oscillations in your front wheel.  These oscillations
usually kick in at high speeds going downhill.  They can get really scary.


The forces involved in steering a bicycle are really quite small. though.
I usually steer my recumbent with one finger.  One hangs on to the
steering bar more for support, or to oppose pedaling, than to steer.

I keep imagining an underseat steering mechanism with a servomotor
connection to the front wheel, a steer-by-wire system.  It is not hard to
find standard servos which will handle 300 oz-in of torque, seems like
plenty.  Most steering is actually very fine adjustments, not gross
movements.   I can imagine a system which would monitor it's own battery,
and alert the user if the battery was low.    Seems like a really
interesting project.


-- Lawrence Lile





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On Sat, 23 Nov 2002, Jinx wrote:

*>> Apparently there is a french company called Mavic Mektronic that
*>> makes an electronic gear change system for bikes with Derailleur
*>> type gears. Uses a push button on each handle bar, one for up, one
*>> for down shift - F1 paddle change style
*>
*>I'd heard about something on the market but hadn't looked into
*>it too seriously, thanks for the link. I reckoned a couple of steppers
*>with worm gears could do it, kind of like machine heads on a guitar,
*>there's not that much tension in the wires

Last time I used a bicycle and tinkered with the derailleur gear mechanism
I found out the hard way that the wire tension is 3-4kgf-ish.

The force required for the torpedo-style (in-hub) gear changers is much
lower, but with 2kgf peaks and some continuous tension.

Peter

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2002\11\25@202544 by Bob Ammerman

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I would think a bicyclist is depending on force feedback from the steering
gear. This would complicate a steer-by-wire system.

Bob Ammerman
RAm Systems

{Original Message removed}

2002\11\25@205300 by Josh Koffman

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I'd be worried about the battery dieing on the road somewhere. What if
instead of a steer by wire, you make a power assisted steering. Instead
of replacing the mechanical link totally, put an encoder on the
handlebars, one on the front wheel, and a servo on the front wheel. Then
use a PIC (of course) to measure the encoders. When you see the front
wheel encoder start to oscillate, generate counteracting forces using
the servo. If the rider is truly trying to turn, you'd be able to
measure a change in the handlebar encoder as well.

Just some thoughts.

Josh
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EraseMEllilespam_OUTspamTakeThisOuTSALTONUSA.COM wrote:
> I keep imagining an underseat steering mechanism with a servomotor
> connection to the front wheel, a steer-by-wire system.  It is not hard to
> find standard servos which will handle 300 oz-in of torque, seems like
> plenty.  Most steering is actually very fine adjustments, not gross
> movements.   I can imagine a system which would monitor it's own battery,
> and alert the user if the battery was low.    Seems like a really
> interesting project.

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2002\11\26@043341 by Alan B. Pearce

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> I keep imagining an underseat steering mechanism with a servomotor
> connection to the front wheel, a steer-by-wire system.  It is not hard to
> find standard servos which will handle 300 oz-in of torque, seems like
> plenty.  Most steering is actually very fine adjustments, not gross
> movements.   I can imagine a system which would monitor it's own battery,
> and alert the user if the battery was low.    Seems like a really
> interesting project.

I would have thought this would be an ideal use for a double acting
hydraulic ram arrangement. One on the front wheel, one on the handlebars and
a pair of hydraulic lines. Could even get some extra leverage into the
system by using different diameter rams if necessary.

Horses for courses - this gives the feedback as well - KISS principle :)))

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2002\11\26@044843 by Jinx

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> > I can imagine a system which would monitor it's own battery,
> > and alert the user if the battery was low

With magnetic impulse charging the battery should stay topped
up under normal circumstances. It's what I plan to do for the 6V
sealed lead I use for my LED lights

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2002\11\26@113145 by llile

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Now, force feedback is an interesting complication I haven't considered!
That would certainly make the project extra complex if it is needed.

I think sideways forces on a bicycle wheel are usually minimal, except
when you are going down a track full of ruts.  This is no off-road bike,
so I won't worry about that possibility just yet.   I am imagining the
rider is more involved with feedback from the vestibular system than the
hands.  I'm tempted to hack this up just to see if it would work.

Now I have worried a little about what kind of sensor to sense the
position of my underseat handlebars with.  The handlebars themselves will
be a conventional carbon fiber straight handlebar in a conventional
gooseneck bearing welded onto the frame.  You need lots of strength in a
handlebar because the rider pulls on the bars to oppose the legs.  The
sensor has to accept getting wet, and either has to accept 360 rotation or
be arranged with a heavy duty end-stop  since you have a 40 cm lever to
haul on it with.  I can't imagine the end-stop torque on a conventional
pot being good enough.  Rotation at least 180 degrees is essential.   Is
there a waterproof pot that would fill the bill?


OTOH, servomotors are quite waterproof all by themselves and contain a
nice high quality pot and a beefy end-stop.  Maybe I could hack apart a
small servo and couple it's pot to my PIC.  I could even stick the whole
thing in the servo case!

ANd thus we also have the makings of a force feedback system.  Big servo
drives the steering wheel, and a signal off the big servo feeds back to
the PIC processor.  PIC drives the little servo which is coupled to the
steering bar.  Signal off the little servo POT drives the PIC which runs
the big servo.

Now, can any one spell O S C I L L A T O R ?  I can imagine this thing
going down the road flapping, or getting unstable at certain speeds.

-- Lawrence Lile





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I would think a bicyclist is depending on force feedback from the steering
gear. This would complicate a steer-by-wire system.

Bob Ammerman
RAm Systems

{Original Message removed}

2002\11\26@113659 by llile

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face
Alan SeZ:
>I would have thought this would be an ideal use for a double acting
hydraulic ram arrangement. One on the front wheel, one on the handlebars
and
a pair of hydraulic lines. Could even get some extra leverage into the
system by using different diameter rams if necessary.

Hmmm - Where would you get such equipment?


-- Lawrence Lile

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2002\11\26@114914 by Alan B. Pearce

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>Hmmm - Where would you get such equipment?

A good place to start is probably an outfit that manufactures replacement
gas lifts for motor vehicle tailgates and the like. Else any plant outfit
that manufactures safety guards for equipment that would be big enough to
require power lifting. The sort of things used on fork lift trucks and mini
diggers would be too large I would expect.

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2002\11\26@121825 by Mike Mansheim

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> I think sideways forces on a bicycle wheel are usually minimal, ...

They may be minimal, but I think Bob is right - I would think the force
feedback is an integral part of the natural balancing.  I've not ridden
a recumbent, so I'm only trying to imagine steering with an underseat
handlebar with no feedback, but I don't think I would like it.
Perhaps you only need resistance to movement? and/or a centering spring?

> be arranged with a heavy duty end-stop  since you have a 40 cm lever...

I thought you were from the U.S.?  Have you been converted to metric?

>                  ...PIC drives the little servo which is coupled to the
> steering bar.  Signal off the little servo POT drives the PIC which runs
> the big servo.
> Now, can any one spell O S C I L L A T O R ?  I can imagine this thing
> going down the road flapping, or getting unstable at certain speeds.

Because you've created a circular reference!  I think this is called
resonance? Little servo and little servo pot need to be independent of
each other.

Someone else mentioned a concern about the battery.  I would assume that
you would take advantage of turning wheels for power as much as possible.
If wheels not turning, steering probably isn't critical.

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2002\11\26@130236 by Dale Botkin

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On Tue, 26 Nov 2002 EraseMEllilespamSALTONUSA.COM wrote:

> Hmmm - Where would you get such equipment?

I would think quite a bit of automotive brake system gear could be adapted
to your use.  Check the racing supply joints like Pegasus for the
non-Detroit stuff that is much more hack/custom friendly (look for
Tilton).  Also, I would bet a quick check of the local Yellow Pages would
yeild a few industrial hydraulics suppliers.

Dale

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2002\11\26@133227 by Lyle Killough

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> Hmmm - Where would you get such equipment?

Bimba manufactures a line of small _aluminum_ hydraulic cylinders for
low-pressure applications (500 psi max).
http://www.bimba.com/products/products.htm

You are looking for their "500 Hydraulic line".

Lyle

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2002\11\26@135726 by llile

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Sez:

>> I think sideways forces on a bicycle wheel are usually minimal, ...

>They may be minimal, but I think Bob is right - I would think the force
feedback is an integral part of the natural balancing.  I've not ridden
a recumbent, so I'm only trying to imagine steering with an underseat
handlebar with no feedback, but I don't think I would like it.

Underseat steering is a real trip at first. Most people can't ride it
without some practice.  My earlier effort at underseat steering worked
fairly well, but suffered from several problems.  The first of which was
the bike was made out of 1.5" EMT tubing, way too soft for a bike! The
whole bike would shimmy at about 60kph/40mph

>> be arranged with a heavy duty end-stop  since you have a 40 cm lever...

>I thought you were from the U.S.?  Have you been converted to metric?

Friends don't let friends use inches.  I've been trying to stay with
Metric ever since High School.  My lab finally decided everything must be
metric after the last fiasco.  Remember what happened to the Mars
satelite? Well that same thing happens to toasters, too only you can still
find them after the fiasco occurs.  All of them are made in factories that
are all metric, with circuits boards that are all metric and so on.


>Someone else mentioned a concern about the battery.  I would assume that
you would take advantage of turning wheels for power as much as possible.
If wheels not turning, steering probably isn't critical.


I am planning on using a lead-acid cell beause they are cheap and the
voltage is a reliable indicator of state-of-charge.  An LED will be green
if the voltage is OK, red if it is below a threshold.  I could even put an
audio alarm on it.  Hope to put this where it will be visible by the
rider.

--Lawrence

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2002\11\26@153815 by Bob Barr

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On Tue, 26 Nov 2002 11:15:00 -0600, Mike Mansheim wrote:

>
>I thought you were from the U.S.?  Have you been converted to metric?
>

Here in the U.S., we're inching our way towards the metric system but
we've still got miles to go. :=)


Regards, Bob

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2002\11\26@154201 by Chris Hunter

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A pot probably wouldn't stand up to the rigours of cycling.... it would be
better to find some other type of sensor - optical or magnetic would
probably be favourite.

Chris

{Original Message removed}

2002\11\26@154415 by Peter L. Peres

picon face
You can remove the play by using a differential transmission with cable.
Boat supplies should have all the parts. I'd use a doubled system I think.
If one cable parts the other will allow you to land softly. Differential
cable is fairly accurate and strong. Plan on 30+lbf tension per cable
imho.

Peter

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2002\11\26@155706 by Chris Hunter

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You could easily charge your lead-acid battery from a simple dynamo
arrangement, and if you do sufficient cycling, you need not worry about the
state of charge.

Chris

{Original Message removed}

2002\11\26@195701 by Josh Koffman

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I've seen small hydraulics used in a lot of scenery automation in
theatre. I don't think there is a regular supplier, but many surplus
shops often have an odd assortment. Princess Auto (a Canadian company)
makes custom hydraulic cylinders. I don't know if they're able to make
them that small though.

Josh
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"Alan B. Pearce" wrote:
> A good place to start is probably an outfit that manufactures replacement
> gas lifts for motor vehicle tailgates and the like. Else any plant outfit
> that manufactures safety guards for equipment that would be big enough to
> require power lifting. The sort of things used on fork lift trucks and mini
> diggers would be too large I would expect.

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2002\11\26@200023 by Josh Koffman

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You could use a stepper motor as an encoder. Tough as nails, and no need
for an end stop. And if you drive it right, you can use it for force
feedback.

Josh
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completely foolproof is to underestimate the ingenuity of complete
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spamBeGonellileSTOPspamspamEraseMESALTONUSA.COM wrote:
{Quote hidden}

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2002\11\27@145108 by Lyle Killough

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Try http://www.bimba.com/products/products.htm for small, low pressure
(500 psi max) hydraulic cylinders with _aluminum_ (or aluminium if you
prefer) bodies.  Look at their "500" series.  I'd hate to be putting a
steel hydraulic cylinder on a bike!

Lyle Killough
------------------------------------------------------------------------
------------------------
Sure Grip Controls Inc.
V:  250-374-2278
F:  250-374-1099
http://www.suregripcontrols.com
EraseMElylespamEraseMEsuregripcontrols.com

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'[OT]: Bike gear ratios'
2003\01\28@162706 by Jinx
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> > Apparently there is a french company called Mavic Mektronic
> > that  makes an electronic gear change system for bikes with
> > Derailleur type gears. Uses a push button on each handle bar,
> > one for up, one for down shift - F1 paddle change style

http://abcnews.go.com/sections/scitech/CuttingEdge/cuttingedge020830.html

I saw the LandRider (http://www.landrider.com) commercial for the first
(and probably last) time yesterday. It uses a govenor on the rear
set to move the chain. That system seems to work OK - couldn't find
any negative comments about it on the web. At NZ$1000+ it's way
more than I'd pay for a bike, plus you still have to manually change the
front set and there are only 14 gears altogether, although there are a
couple of features I'd have a go at copying. 30 mins of relentless glee
club enthusiasm, badgering and exaggeration doesn't exactly endear
you to a product either

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2003\01\28@164332 by cdb

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On Wed, 29 Jan 2003 10:27:34 +1300, Jinx wrote:
> Apparently there is a french company called Mavic Mektronic
> > that  makes an electronic gear change system for bikes with
> > Derailleur type gears. Uses a push button on each handle bar,
> > one for up, one for down shift - F1 paddle change style

That reminds me, back in the 70's my father had a Renault automatic - 15 or something it had the engine in the back, anyhow at that time it was the only commercial car with  an electronic gearbox, it worked by pushbuttons as you could select the individual gears or have it do everything automatically. The gearbox was a standard manual but with a set of solenoids that the control unit 'steered into the correct position.

A  clutch IIRC wasn't needed as it borrowed the Citroen pre-selector/centrifugal clutch system of the Pallas and AMi8.

Oh yes jinx moi an Oz boy? I'm a Blighty boy living in Oz at the moment. Though dadykins and family are true blue Oz boys 3 or 4 generation!

Colin
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2003\01\28@172734 by Jonathan Johnson

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>Oh yes jinx moi an Oz boy? I'm a Blighty boy living in >Oz at the moment.
Though dadykins and family are true >blue Oz boys 3 or 4 generation!

>Colin

Umm....blighty boy? dadykins? where exactly ARE you from Colin? I'm an
Aussie by the way and have never heard these ones in conversation......by
any origin.

cheers
JJ

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