Dynohubs for mountain bikes

Marty said:

Does anyone make dynohubs for mountain bikes. It would have to be at least a 20 watt output,
ideally 12 volts. I know there are a few around but their wattage is far too low. I think anyone
that made a decent one with a good output would be on a winner.

20W output would require over 30W input for the best dynamos - you wouldn't put up with this sort of
drag. B&M make a 12V/6.2W bottle dynamo, but it is so fearsomely expensive that you could buy a HID
rechargeable system instead.

Zog The Undeniable said:

Marty said:

Does anyone make dynohubs for mountain bikes. It would have to be at least a 20 watt output,
ideally 12 volts. I know there are a few around but their wattage is far too low. I think anyone
that made a decent one with a good output would be on a winner.

20W output would require over 30W input for the best dynamos - you wouldn't put up with this sort
of drag. B&M make a 12V/6.2W bottle dynamo, but it is so fearsomely expensive that you could buy a
HID rechargeable system instead.

problem with off-road use of (hub)dynamo's is that the lights go out when things get difficult. So
you need a battery to take over, and as most MTB outings are short, it is more efficient to make the
battery a bit bigger and do without the dynamo. Marten

Dear Marty,

You could fit the latest brushless Sanyo dynohub, not in general distribution. Operated as a three
phase generator it'd do fine. But it only works with forward speed.

I currently have a six pound Ametek servo motor that is frequently sold on the internet as a wind
generator. It's rated at 30 V, and can draw 15 A at stall without permanent demagnetization. It's
mounted low in the main frame triangle and is chain driven from a left side stoker's crank.

I use it as a generator and usually maintain 16-20 V while pedaling normally. A free sample of the
latest power converter hybrid IC from TI will downconvert this to 15 V to run my pen computer and
the sine wave inverter. Camille from TI just called to ask about the project. I told her it was
called the Night Assault Bicycle, and it is.

I have previously run the generator to a capacitor bank to level the output, monitored the charge to
10-15 V by adjusting gears and effort, and run a single 9W flourescent bulb with a non sine wave
(sine wave emulating) inverter.

I have a dimmer and two 20 W dimmable fluorescent bulbs. The bulbs claim 100% to 20% dimming but the
dimmer seems to supply a bit less range from full on. At least they don't blink out when fully
dimmed. DHL is bringing two R30 reflectors today to improve the distribution patter. Together they
form the "headlights".

With a similar system, using a Bicycle Lighting Systems headlight, I have navigated little-used
single track uphill in first gear with no loss of light.

A small capacitor or ultracapacitor bank to even things out would help.

Anyway, the motor is rather too large for this application, but 5/8 or 1/2 inch shaft was the only
size I could get pinions in, and the combination of the Ametek's 5/8 shaft, its < 1000 rpm
operating range, it's high generator constant of 37V / 1000 rpm, and an 8 tooth pinion from a go
cart I found in the Northern catalog is the one combination that has worked out. It has rather a
large (several ohm) source resistance, so changes in load require larger changes in speed, not just
changes in effort.

I also have on the bike an Avon Derma Spec fluorescent lamp, strapped on to Minoura Space Bars with
hose clamps, with no solution for the start button. There's a paper on the web that tells you how to
modify these for constant on.

I have also orderd FOUR one watt white LEDs. Each is 3.6V, 300 ma, and in series will run nicely on
regulated 15 VDC. The thing about these is they are RUGGED, and that is what your OP is all about.

So, with a motor similar to the Ametek, and some white LEDs (from Oatley) you may be in business.

The motor fits between the cranks and comes up somewhat higher than they do.

I have one such motor surplus, machined, with the requisite 8 tyooth pinion and chain guard. You'll
have to grab a Dimension stoker's crank from the Quality Bicycle Products catalog at your local bike
shop and fit it with a cog that suits your legs and load. The mount instructions are on my web site:

users.aol.comDGonczOpen ↗

ftp://users.aol.com/DGoncz

I could have ridden that 9W bulb all night and it is the equivalent of a 35 incandescent, although
the beam pattern is broader. On my run up Upton Hill the light was 35 watts incandescent and now
THAT was a significant load, but I was climbing steeply.

Kevin McMurtrie has produced a CCFL fluorescent lamp that shows promise as a headlight. His has a
carbon fiber parabolic reflector.

My senior project at ODU: Google Groups, then "dgoncz" and some of: ultracapacitor bicycle
fluorescent flywheel inverter Equipped with BoBike Mini removable child seat, too!

Marty said:

Does anyone make dynohubs for mountain bikes. It would have to be at least a 20 watt output,
ideally 12 volts. I know there are a few around but their wattage is far too low.

This is a non-starter, because 20W output implies a drag of over 20W and you'll certainly feel that.
--
David Damerell <[email hidden]> flcl?

Quoted post said:

Originally posted by Doug Goncz
Dear Marty,

You could fit the latest brushless Sanyo dynohub, not in general distribution. Operated as a three
phase generator it'd do fine. But it only works with forward speed.

I currently have a six pound Ametek servo motor that is frequently sold on the internet as a wind
generator. It's rated at 30 V, and can draw 15 A at stall without permanent demagnetization. It's
mounted low in the main frame triangle and is chain driven from a left side stoker's crank.

I use it as a generator and usually maintain 16-20 V while pedaling normally. A free sample of the
latest power converter hybrid IC from TI will downconvert this to 15 V to run my pen computer and
the sine wave inverter. Camille from TI just called to ask about the project. I told her it was
called the Night Assault Bicycle, and it is.

I have previously run the generator to a capacitor bank to level the output, monitored the charge to
10-15 V by adjusting gears and effort, and run a single 9W flourescent bulb with a non sine wave
(sine wave emulating) inverter.

I have a dimmer and two 20 W dimmable fluorescent bulbs. The bulbs claim 100% to 20% dimming but the
dimmer seems to supply a bit less range from full on. At least they don't blink out when fully
dimmed. DHL is bringing two R30 reflectors today to improve the distribution patter. Together they
form the "headlights".

With a similar system, using a Bicycle Lighting Systems headlight, I have navigated little-used
single track uphill in first gear with no loss of light.

A small capacitor or ultracapacitor bank to even things out would help.

Anyway, the motor is rather too large for this application, but 5/8 or 1/2 inch shaft was the only
size I could get pinions in, and the combination of the Ametek's 5/8 shaft, its < 1000 rpm
operating range, it's high generator constant of 37V / 1000 rpm, and an 8 tooth pinion from a go
cart I found in the Northern catalog is the one combination that has worked out. It has rather a
large (several ohm) source resistance, so changes in load require larger changes in speed, not just
changes in effort.

I also have on the bike an Avon Derma Spec fluorescent lamp, strapped on to Minoura Space Bars with
hose clamps, with no solution for the start button. There's a paper on the web that tells you how to
modify these for constant on.

I have also orderd FOUR one watt white LEDs. Each is 3.6V, 300 ma, and in series will run nicely on
regulated 15 VDC. The thing about these is they are RUGGED, and that is what your OP is all about.

So, with a motor similar to the Ametek, and some white LEDs (from Oatley) you may be in business.

The motor fits between the cranks and comes up somewhat higher than they do.

I have one such motor surplus, machined, with the requisite 8 tyooth pinion and chain guard. You'll
have to grab a Dimension stoker's crank from the Quality Bicycle Products catalog at your local bike
shop and fit it with a cog that suits your legs and load. The mount instructions are on my web site:

users.aol.comDGonczOpen ↗

ftp://users.aol.com/DGoncz

I could have ridden that 9W bulb all night and it is the equivalent of a 35 incandescent, although
the beam pattern is broader. On my run up Upton Hill the light was 35 watts incandescent and now
THAT was a significant load, but I was climbing steeply.

Kevin McMurtrie has produced a CCFL fluorescent lamp that shows promise as a headlight. His has a
carbon fiber parabolic reflector.

My senior project at ODU: Google Groups, then "dgoncz" and some of: ultracapacitor bicycle
fluorescent flywheel inverter Equipped with BoBike Mini removable child seat, too!

Doug -

Have you any data on the efficiency of your generator?

You refered to a Sanyo brushless dynahub- is that the the 250W hub for Sanyo's regenerative braking ev-kit (that was supposed to be available last spring)?

Is ODU Old Dominion?

The OP was looking at a mountain bike application on the dyno hub. I'm assuming your flourescent lighting is for road based applications and not intned for mountain biking shock. Is that correct?

[email hidden] (Marty) wrote in message news:<[email hidden]>...

Quoted message said:

Does anyone make dynohubs for mountain bikes. It would have to be at least a 20 watt output,
ideally 12 volts. I know there are a few around but their wattage is far too low. I think anyone
that made a decent one with a good output would be on a winner.

Marty

The only generator that would work is indeed a dynohub. Both the Shimano Nexus and the Schmidt offer
6 V 3 W, although they may be rigged to 12 V 6 W at high speed. Schmidt may eventually issue a 12 V
6 W that will get full brightness at 15 km/h, but don't hold your breath. The efficient lights they
use make them quite useful light sources on the road but not as much in the woods.

I think you might use either that or one or two LED headlights such as the Cateye EL-300 for basic
lighting (easy sections, reaching the trails, on-road cycling) and keep your high power battery
headlights for the more technical sections. But when one consider that the typical cyclists produces
60-80 W, sometimes 100 W continuous, robbing 30 W of these to power a headlight seems presumptuous.

Michel