I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

In article ,
Tim Wescott wrote:

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Depends what you mean by easy - planetary gears are a classic compact
method, since you didn't mention cost as an object. But it probably is.
If using chains, timing belts, or belts, a jackshaft is the classic
serious gear-down method.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

On Thu, 18 May 2017 14:25:29 -0400, Ecnerwal wrote:

In article ,
Tim Wescott wrote:

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Depends what you mean by easy - planetary gears are a classic compact
method, since you didn't mention cost as an object. But it probably is.
If using chains, timing belts, or belts, a jackshaft is the classic
serious gear-down method.

Something that can easily be stuck onto an existing gizmo, preferably
while leaving the linked-to motor intact.

In a world of unlimited lead time and with no object to cost, "best"
would be to get a motor custom-made for the purpose. That's kind of the
opposite situation from what we have.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Thu, 18 May 2017 13:10:48 -0500
Tim Wescott wrote:

snip
So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Not cheap, but have you seen the NuVinci hub:

https://en.wikipedia.org/wiki/NuVinci

https://www.amazon.com/s/ie=UTF8&ind...=NuVinci%20hub

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Thu, 18 May 2017 15:31:39 -0400, Leon Fisk wrote:

On Thu, 18 May 2017 13:10:48 -0500 Tim Wescott
wrote:

snip
So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Not cheap, but have you seen the NuVinci hub:

https://en.wikipedia.org/wiki/NuVinci

https://www.amazon.com/s/ie=UTF8&ind...=NuVinci%20hub

They're using it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Thu, 18 May 2017 14:38:12 -0500
Tim Wescott wrote:

On Thu, 18 May 2017 15:31:39 -0400, Leon Fisk wrote:

On Thu, 18 May 2017 13:10:48 -0500 Tim Wescott
wrote:

snip
[...]

Not cheap, but have you seen the NuVinci hub:

https://en.wikipedia.org/wiki/NuVinci

https://www.amazon.com/s/ie=UTF8&ind...=NuVinci%20hub

They're using it.


I use to keep up with the bicycling stuff, many years ago... Someone
started making a gearbox back then that mounted in the frame, above the
crank. Never heard anymore about it or saw one in the wild. This
might give you some more ideas:

https://en.wikipedia.org/wiki/Gearbox_bicycle

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Thu, 18 May 2017 16:02:19 -0400
Leon Fisk wrote:

On Thu, 18 May 2017 14:38:12 -0500
Tim Wescott wrote:

They're using it.

I see you can still get the old 3-speed hubs for ~$50 too. You would
have to figure out a way to mount it and fab a special sprocket to go in
place of the spokes...

https://www.amazon.com/Sturmey-Arche...dp/B000BMT2PQ/

https://www.amazon.com/Shimano-SG-3C...dp/B001GSKVIQ/

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Thu, 18 May 2017 13:10:48 -0500, Tim Wescott
wrote:

I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Is the purpose to make an electric drive vehicle or a bicycle with
electric power available?

If the first then possible a dual front crank, i,e, two sprockets,
might work - from motor to crank sprocket, from second crank sprocket
to rear wheel. Note that dual or triple cranks are pretty much the
standard on sports bicycles these days.

If the latter then I would think that there would have to be some
method of disconnecting the motor from the pedals in some manner.

Whizzer, which was a belt driven internal combustion motor design used
a separate belt drive from the motor to the wheel. See
http://tinyurl.com/n4tlr9e
--
Cheers,

John B.

On Thu, 18 May 2017 13:10:48 -0500, Tim Wescott
wrote:

I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

EE, huh? g


I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

Did he use the mid-drive style because the bike doesn't use standard
wheels/tires? I paid $209 for the 800w front hub motor style,
complete with brake levers, thumb throttle, controller, pedal assist
ring/sensor, bag, and rear package tray. They run as low as $159 now.

Here's a 1kw rear for $185. http://tinyurl.com/ly2tdl8


He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

I believe that the lower wattage motors are designed for assist, not
to provide full power/torque, especially for long term use like hill
climbing.


So -- any thoughts on an easy way to gear the thing down?

It already has a reduction unit built in, Tim. There's not much you
can do with a small motor like that.


I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

I hope he isn't driving the pedals. Sprag clutches (cassette or
freewheel, in bike terms) are cheap.

--
In today’s academia and mainstream media,
we’re all guilty of hate until proven leftist.

--Robert Knight, senior fellow, American Civil Rights Union

On Thu, 18 May 2017 20:28:45 -0700, Larry Jaques wrote:

On Thu, 18 May 2017 13:10:48 -0500, Tim Wescott
wrote:

I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

EE, huh? g


I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

Did he use the mid-drive style because the bike doesn't use standard
wheels/tires? I paid $209 for the 800w front hub motor style, complete
with brake levers, thumb throttle, controller, pedal assist ring/sensor,
bag, and rear package tray. They run as low as $159 now.

Here's a 1kw rear for $185. http://tinyurl.com/ly2tdl8


He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board,
and we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

I believe that the lower wattage motors are designed for assist, not to
provide full power/torque, especially for long term use like hill
climbing.


So -- any thoughts on an easy way to gear the thing down?

It already has a reduction unit built in, Tim. There's not much you can
do with a small motor like that.


I just recommended to the customer that they put two chain rings on the
crank, so that they can drive the pedals at one speed and the bike at
another.

I hope he isn't driving the pedals. Sprag clutches (cassette or
freewheel, in bike terms) are cheap.

There are lots of details that are perfectly sensible in his context, but
which I don't feel that I have permission to discuss publicly. Alas.

Just these: (A) it's a weird application, and (B) in its context it makes
perfect sense.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Thursday, May 18, 2017 at 2:10:55 PM UTC-4, Tim Wescott wrote:
I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I think I'm missing the problem - looking at your question, you refer to driving the pedals. Looking at the picture on Amazon, they are driving a separate sprocket on the rear wheel. What's the problem with changing that driven sprocket (on the wheel) to a larger size?

But do like the idea of the Sturmey-Archer 3-speed. Just get that mounted in the middle of the drive train, and you're good to go.

On Fri, 19 May 2017 10:25:58 -0700, rangerssuck wrote:

On Thursday, May 18, 2017 at 2:10:55 PM UTC-4, Tim Wescott wrote:
I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board,
and we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more
current for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

I think I'm missing the problem - looking at your question, you refer to
driving the pedals. Looking at the picture on Amazon, they are driving a
separate sprocket on the rear wheel. What's the problem with changing
that driven sprocket (on the wheel) to a larger size?

But do like the idea of the Sturmey-Archer 3-speed. Just get that
mounted in the middle of the drive train, and you're good to go.

Customer can't easily get bigger sprockets for his chosen rear hub.

That is on the table, but I'm looking at alternatives.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Tim Wescott" wrote in message
news
I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
================================================== =======

Well, to lower the gearing you either need a smaller drive gear and 9 teeth
is the smallest common one I found ( I found one 8 tooth gear but I would be
afraid the diameter is getting too small for durability), or a bigger driven
gear and you say that is fixed so external changes are out. How about going
inside the gearbox on the motor? In the amazon listing there is a sticker
on the motor for www.unitemotor.com, and while I don't read Chinese if you
go there and then click on the button halfway down the right side you get to
another site which appears to be a distributor. Open up the box you have
now just so you know what your are dealing with, then contact them to see if
you can get different gear ratios. You can use translate.google.com to get
the gist of the site, and hopefully someone there speaks english. If you
are going to need these in quantity anyway, maybe you can just order a batch
with a custom gear ratio.

--
Regards,
Carl Ijames

On Friday, May 19, 2017 at 1:30:12 PM UTC-4, Tim Wescott wrote:
On Fri, 19 May 2017 10:25:58 -0700, rangerssuck wrote:

On Thursday, May 18, 2017 at 2:10:55 PM UTC-4, Tim Wescott wrote:
I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board,
and we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more
current for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another..

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

I think I'm missing the problem - looking at your question, you refer to
driving the pedals. Looking at the picture on Amazon, they are driving a
separate sprocket on the rear wheel. What's the problem with changing
that driven sprocket (on the wheel) to a larger size?

But do like the idea of the Sturmey-Archer 3-speed. Just get that
mounted in the middle of the drive train, and you're good to go.

Customer can't easily get bigger sprockets for his chosen rear hub.

That is on the table, but I'm looking at alternatives.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Oh, I dunno, take a look (for example) he http://www.rollerchain4less.com/35-P..._1013-1-1.html They have a pretty big selection. You can, with some machining & welding, get these to fit pretty much any hub. You could even cnc mill an opening in the larger sprocket to be a snug fit over the existing sprocket and either weld or mechanically fasten them together.

On Fri, 19 May 2017 12:30:05 -0500, Tim Wescott
wrote:

On Fri, 19 May 2017 10:25:58 -0700, rangerssuck wrote:

On Thursday, May 18, 2017 at 2:10:55 PM UTC-4, Tim Wescott wrote:
I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board,
and we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more
current for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

I think I'm missing the problem - looking at your question, you refer to
driving the pedals. Looking at the picture on Amazon, they are driving a
separate sprocket on the rear wheel. What's the problem with changing
that driven sprocket (on the wheel) to a larger size?

But do like the idea of the Sturmey-Archer 3-speed. Just get that
mounted in the middle of the drive train, and you're good to go.

Customer can't easily get bigger sprockets for his chosen rear hub.

That is on the table, but I'm looking at alternatives.
Greetings Tim,
Last summer I was working on a project that I thought would need a
larger sprocket than I had. I looked into making my own first. It
would have been pretty easy for me to mill one 'cause I have a machine
shop and a couple CNC mills that would do the work, I just needed the
tooth dimensions, which I found easily enough on the web. But I also
found more than one site that sells little gas engines for bicycles
that sold several sizes of large sprockets and a couple sites that
would make custom sizes. As I recall the prices were pretty cheap. I
ended up avoiding the need for a custom sprocket and don't remember
which bike motor sites were selling them but it didn't take me long to
find them when I looked last year.
Cheers,
Eric