Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Electronics, Lighting, & Gadgets HRM, GPS, MP3, HID. Whether it's got an acronym or not, here's where you'll find discussions on all sorts of tools, toys and gadgets.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 04-04-14, 08:30 PM   #26
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,764
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 208 Post(s)
Quote:
Originally Posted by ratdog View Post
Faster downhill rides with the extra weight?
The acceleration of gravity is independent of mass...
JohnDThompson is offline   Reply With Quote
Old 04-05-14, 07:24 AM   #27
Looigi
Senior Member
 
Looigi's Avatar
 
Join Date: Dec 2010
Bikes:
Posts: 8,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Quote:
Originally Posted by JohnDThompson View Post
The acceleration of gravity is independent of mass...
Yes, but terminal speed in air depends on density, other things being equal.
Looigi is offline   Reply With Quote
Old 06-05-14, 10:43 PM   #28
Joe_Hoffmann
Member
Thread Starter
 
Joe_Hoffmann's Avatar
 
Join Date: Aug 2013
Location: Wisconsin USA
Bikes: 1981 Schwinn World Tourist, 200* redline conquest tour
Posts: 30
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Everyone in this thread misses the cool factor of having a car alternator on a bicycle. My main point in starting this thread was for more of an "art" bicycle setup, not AN ACTUAL REPLACEMENT FOR A DYNOHUB!
But I should have clarified that. The purpose would be to build a "mad max" style bicycle.


Obviously a car alternator is not mean for a bicycle, due to the weight and friction. I think if you only desire 6 watts, then the wattage required to spin the alternator would be less than 30 watts, which I think would be do-able for the length of a parade or art bike festival. You could vary the current and voltage into the field coils to produce any power that you wanted. I don't think it would draw 200 watts no-load, but then again I could be wrong. I'm not an electrical engineer.
Joe_Hoffmann is offline   Reply With Quote
Old 06-06-14, 05:51 AM   #29
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,628
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 202 Post(s)
Quote:
Originally Posted by Joe_Hoffmann View Post
Everyone in this thread misses the cool factor of having a car alternator on a bicycle. My main point in starting this thread was for more of an "art" bicycle setup, not AN ACTUAL REPLACEMENT FOR A DYNOHUB!
But I should have clarified that. The purpose would be to build a "mad max" style bicycle.
"Cool" is arguable. There's an "alt bike" forum that might be a better audience for this.

Yes, if you have a point, don't keep it a secret.
njkayaker is offline   Reply With Quote
Old 06-06-14, 06:57 AM   #30
DBA
Guest
 
Join Date: May 2014
Bikes:
Posts: 211
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you can find one, the old VW bugs used to use a 6v system. I'm not sure how heavy the alternators were, but I'd bet they are easier to spin than a modern 12v alternator designed to produce enough juice to run all the electronics in a modern car.

Personally, I'd just use a bike specific dynamo for lighting purposes, but if you wanted to make a trainer/generator to charge batteries or run a tv during a power outage.
DBA is offline   Reply With Quote
Old 06-06-14, 09:56 AM   #31
Joe_Hoffmann
Member
Thread Starter
 
Joe_Hoffmann's Avatar
 
Join Date: Aug 2013
Location: Wisconsin USA
Bikes: 1981 Schwinn World Tourist, 200* redline conquest tour
Posts: 30
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
apparently I started this thread in the wrong category.
Joe_Hoffmann is offline   Reply With Quote
Old 06-06-14, 10:11 AM   #32
RPK79
Senior Member
 
RPK79's Avatar
 
Join Date: May 2013
Location: SE MN
Bikes: Fuji Roubaix Pro & Fuji Track Classic
Posts: 8,724
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 885 Post(s)
Quote:
Originally Posted by njkayaker View Post
"Nowadays"??

That's why it was called "soylent green" in the first place. The whole "it's people" (rather than made from soy/plants) thing being a "surprise" was the point.
Hello! Spoiler Alert!!
RPK79 is offline   Reply With Quote
Old 06-11-14, 06:55 AM   #33
darkrider2
Junior Member
 
Join Date: Aug 2009
Bikes:
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Sturmey-Archer's hub puts out about 3 watts if I remember correctly. That's enough to run a 2-300 lumen led light. Even that level of output puts considerable drag on your pedaling. If you want to run a 1000 lumen light it will be like going up a 15% grade all the time.
darkrider2 is offline   Reply With Quote
Old 06-11-14, 10:37 AM   #34
dougmc
Senior Member
 
dougmc's Avatar
 
Join Date: Jul 2008
Location: Austin, TX
Bikes: Giant OCR2, Bridgestone RB-T, Bike-E, Vision R-40, Novara Safari
Posts: 3,029
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by darkrider2 View Post
If you want to run a 1000 lumen light it will be like going up a 15% grade all the time.
Your idea is right, but you've exaggerated the effect considerably.

1000 lumens is probably around 10 watts for a good LED. Assume that your generator is typical and 50% efficient, and that's 20 watts of drag. (That said, I doubt a retrofitted alternator would be even that efficient.)

Let's say a typical recreational cyclist can sustain 100 watts, so that's 20% of their power gone. And yes, that's huge. So on level ground, looking only at air resistance, that would slow them down by about 7% (1-cube root(0.8)). Going up a steep hill, the light would slow them down by 20%. (Though the percentage would reduce if they produced more power (i.e. worked harder) going up the hill, like most cyclists do.)

But where a 100 watt cyclist could do perhaps 15 mph on level ground, or 14 mph with this generator going ... a 15% grade (and without this light) would slow them down to around 2 mph. (And no, that's not a typo -- I calculated it with 180 lbs of rider+bicycle.)
dougmc is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:39 PM.