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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 02-03-08, 10:55 PM   #1
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DIY Rollers

So, I was scrounging around a friends garage the other day and I came across an old-ish set of rollers for use with a table saw. Its like two side pieces which hold 5 metal rollers on bearings in a row so you can slide pieces of wood on em. My question is, do you think they could be re-organized or used to create a set of rollers to ride on on the cheap? I dont really know the mechanics of rollers, so I have no idea, but I'm pretty sure I could get a similar set, or those for dirt cheap. Any ideas or comments?
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Old 02-03-08, 11:29 PM   #2
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What diameter are they? Here are my rollers just so you can see what your goal is.





The back wheel rests on the two back rollers. The black rubber band transfers the rotation from the rear rollers to the front roller so both wheels spin. The drums are 85mm in diameter. If you can manage to build that out of what you have then awesome. It seems like a pretty big project to me but it might be possible.
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Old 02-03-08, 11:37 PM   #3
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The smaller the roller diameter, the more watts it takes to spin. Kreitler's site has a chart which others comment are more "ballpark" guidelines to the watts required (varies with your weight, tire size, tire inflation pressure) LINK. The table saw rollers I've seen, they were too small in diameter and I wonder if the supplied bearings are up to the load & RPM's bicycle rollers are subject to.
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Old 02-03-08, 11:44 PM   #4
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http://www.woodcraft.com/family.aspx?familyid=4346
those are a lot like the set I saw.
So you are saying the drums are too small to work? Could someone give me a brief rundown of why it wouldnt work? That chart just seems to suggest you would have to exert more force to go a given speed.

Edit:
http://toolsandmore.us/index.asp?Pag...ROD&ProdID=531
that looks like a better picture. The rollers dont look that much smaller than the ones you have. I wouldnt be using the rollers too excessively, so I'm not entirely worried about the longevity of the bearings, and they feel pretty sturdy and well made. I basically just want something to ride occasionally in my dorm room when the weather is bad for multiple days at a time.
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Old 02-03-08, 11:50 PM   #5
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The smaller the the drum the harder you have to pedal. I have no idea how hard you would have to pedal with those drums.
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Old 02-03-08, 11:51 PM   #6
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The smaller the the drum the harder you have to pedal. I have no idea how hard you would have to pedal with those drums.
so, presumably, the problem would be that you couldnt ride fast enough to keep upright if the rollers were too small?
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Old 02-03-08, 11:54 PM   #7
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yes but the lower the radius the harder it will be to ride
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Old 02-03-08, 11:57 PM   #8
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Harder, as in physically more exerting? or harder as in more difficult to stay on the rollers?
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Old 02-04-08, 12:00 AM   #9
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I only need to ride at about 50 rpm (about 10 mph) to feel reasonably sturdy. I think you could probably go that fast on small drums. But yeah, the main problems I can foresee is how much leg power you will need and how sturdy you could get on whatever setup you make. If you pump your tires up as high as possible the 85mm rollers spin with almost no effort so you should probably try that out if you manage to build small drum rollers.

edit: Harder as in leg power. The slower you go the harder it is to balance. I suppose those problems go hand in hand.
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Old 02-04-08, 12:02 AM   #10
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Read step 2.
Basically the smaller contact patch combined with the higher speed of a small roller create a lot more resistance. The link above talks about it in a bit more detail.
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Old 02-04-08, 12:03 AM   #11
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Hmm, maybe I'll give it a shot. I just was looking through a trade show pamphlet and it looks like they have a set of those 5drum rollers for like 25 dollars, maybe i'll look into those. I dont think those rollers look that much smaller than normal bike roller drums, but I'm not sure.
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Old 02-04-08, 12:12 AM   #12
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i saw some rollers at performance for 120.

i'd rather just cough up the money... and i don't have it so...
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Old 02-04-08, 12:17 AM   #13
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Your campus gym should have decent exercise bikes.
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Old 02-04-08, 12:19 AM   #14
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The rollers in that picture are $100 at performance right now.
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Old 02-04-08, 12:23 AM   #15
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Hmmm, could someone link me to the 100 dollar rollers?
Perhaps its worth the extra 70 bucks.
Thanks to everyone for the help.
I dont want to use the campus bikes because rollers help maintain form.
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Old 02-04-08, 12:32 AM   #16
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http://www.performancebike.com/shop/...tegory_ID=4121

I'm sure there's a 10 or 15% off coupon out there right now, too.
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Old 02-04-08, 07:27 AM   #17
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nashbar has some for <$100 as of last night
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Old 02-04-08, 07:44 AM   #18
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my dad made a set for me when i was like 13, out of some angle iron and and a bunch of drums from a printing press... they were pretty good all and all. good luck finding those for cheap though
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Old 02-04-08, 07:44 AM   #19
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I still haven't figured out how rollers work. Can someone PLEASE explain how you don't fall? What holds you up?
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Old 02-04-08, 08:01 AM   #20
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I still haven't figured out how rollers work. Can someone PLEASE explain how you don't fall? What holds you up?
Are you serious?
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Old 02-04-08, 08:17 AM   #21
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I still haven't figured out how rollers work. Can someone PLEASE explain how you don't fall? What holds you up?
Well, actually you can fall. Just as riding a bike on flat ground, you balance by a combination of weight shifting and steering, and just as on flat ground, balancing at low speed is more difficult than at higher speeds. Except on rollers, balancing at any given speed is more difficult than on flat ground for reasons that are not clear to me. A smooth pedaling motion is particularly important in staying upright on rollers.

Unless you like falling, learn rollers by setting them up in a door frame so you can support yourself on the door frame while getting on the bike and pedaling up to a reasonable speed. Search YouTube for videos of people cycling on rollers. Some are quite funny, others quite amazing.
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Old 02-04-08, 08:39 AM   #22
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I still haven't figured out how rollers work. Can someone PLEASE explain how you don't fall? What holds you up?
I believe that it's primarily precession that keeps you upright. Precession is the same thing that keeps a gyroscope upright.

I read this interesting physics article about bicycles awhile ago which was about what keeps them upright. Precession actually isn't necessary when you are riding a bike, but it is necessary to ride with no hands.

However on rollers I'm sure precession plays a much bigger role.
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Old 02-04-08, 08:53 AM   #23
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Are you serious?
Sorry, I ride my bike outside.
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Old 02-04-08, 10:27 AM   #24
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I'm not sure how much of a role precession plays with a moving bike (eg, outside) when compared with inertia— i seem to recall a diy project where some folks mounted a counter-rotating set of wheels and found the bike more difficult to ride no-handed, but not impossible to ride. However, on a set of rollers there is no linear inertia, so precession likely plays a greater role.
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Old 02-04-08, 10:29 AM   #25
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pics of diy roller death plz
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