Enormous Chain ring
 

Hey peeps. I am looking for a chain ring that has an outer diameter (including the teeth) of 26". Is there such thing, or would I need to have somebody cast one for me? I am attempting to make a hubless wheeled bike. This is really the only solution I have found for the drive train. Do you guys have any alternatives for a good hubless drive train? Thanks in advance!

I've seen very large sprockets salvaged from older Schwinn exercise bikes before. Just pics on the net, never in real life. Not sure of the diameter, but they are huge!

Cool. Thanks. I guess that would be extremely inexpensive too. I realized, however, that when I would turn on the side that the chain ring would be on, the chain would probably catch the ground, resulting in a very painful experience, unless I made arms that attach to the rotating part of the wheel and put a smaller chain ring on the arms.

Are there any other alternatives to a hubless drivetrain?


**EDIT** Where can I find a chain ring as big as this guy's, but without the stuff inside of it. I want just the toothed rim of the ring.

I think you'll find that guy's chainring was custom made, probably for pacing behind motorized vehicles.

For a precision job, you'd need to have something machined out.

You could take pieces of regular chain rings and mount them to a large disc. This would probably be functional, if not overly smooth.

So you're trying to make something like the picture below, only human powered?

You could possibly make a belt drive setup by attaching a second rim off the side of the rear rim. Maybe a 24" paired with a 26". Of course then you'd need a belt drive setup at the crank. And some way to attach the wheel to the bike. And make it freewheel. Unless you're going fixed.

How do you plan on addressing the gear ratio issue? For example, if you have an effective gear of 49/99 on a 26" wheel you would travel just over 12 inches forward for every rotation of the crank, which is about 1/5th the gear inches of an average single speed bike.

http://farm1.static.flickr.com/130/3...2db71fc5a0.jpg

Ok, the OP says things that make no sense to me. He wants a large chainring cause he wants to make a hubless bike.

Im' just trying to picture what that would be like since one is up front and one is out back.

I was considering a belt driven system actually. The gear ratio was kinda keeping me back from starting this crusade.

As I was driving home from school today, I thought up a great, low-profile idea:

In between the seat tube and the tire, have a roller that has two gears welded to each side, then have a chain ring on each side of the bike and run a chain from one chain ring to a gear on the same side, then do the same on the other side. I think that sounds like a bullet-proof idea. What do you people think?

Double reduction gear:
http://www.canosoarus.com/08LSRbicyc...%20BkStand.JPG

Not quite, but close. It will look similar to the picture, but it is a hubless, so I wont have a sprocket. Just the front chain ring and the one near the seat tube.

Right, but its the same principle, with the jack shaft.

You might consider using two eccentric bottom brackets (one at the crank, one on the jack shaft) in order to be able to tension both sets of chain/belt.

Oh I forgot to say that I am going to somehow put a shield type side to the roller so that it could be welded to the seat tube. And FYI, when I say seat tube, I don't mean seat post. I am talking about the tube that the seat goes in. Am I using the right word?

How will the wheel attach to the bike? How do those motorcycle wheels attach? These look like Houdini's bikes!

Follow the bolt pattern outside the cog teeth. Those bolt to the stationary inner part of the hub. The 8 staggered bolts to the left of the cog teeth bolt to the frame. There's several nesting layers and lots of bearings involved.

edit: this is my hubless...thing. its much more simple

http://img.photobucket.com/albums/v520/lz4005/ultie.jpg

Uh...I have no idea what you are talking about. Could you please clarify?

I was answering BlackSunshine's question about the motorcycle.

Oh. I see ;). I thought I read somewhere on the interweb that the rear wheel is driven by magnets. How the **** does that work? Oh, and here is a badass video of a hubless chopper.

Recumbent/human powered vehicle people have been making extra-super-large chainrings for ages. Have a look:
http://fleettrikes.com/vacuum_trike_sprocket%20blue.jpg
from http://www.fleettrikes.com/vacuum.htm

I remember instructions from an old HPV news that showed how to make a chainring from an aluminum plate using a router. Read http://www.ihpva.org/HParchive/PDF/05-spring-1980.pdf , starting on page 2.

If you're wanting to build a "hubless" bike, you better get good at machining your own parts. The chainring will be the least of your worries. :cry:

Hey there, Jeff. I am not sure if you saw the latest posts or not, but I found a more logical idea for the drive train.

I found this airless tire(scroll all the way down to see the airless tire), and I think it will correspond perfectly with my design. The way that the hubless design was designed, the wheel/tire/inner tube would not be able to be removed unless you took a plasma cutter or hack saw to the frame. :lol: I guess that's the best way I could think of for making a hubless bike. I like the idea of the airless wheel anyway. Better for the environment. ;)

You are mad, you must know that. Awesome project though. I've got one question, where will you get the rims? Bicycle rims are feeble without the spokes holding them in place.

It doesn't.

If you really want to get complicated and adapt from the motorcycle world, there have been some custom motorcycles made with a hidden friction drive, using a rubber roller to drive the rear tire directly rather than a traditional chain/shaft/belt system.

You could always ask Eric Paulson how he did his.
Or just read about it and look at the pics.
http://bikerodnkustom4.homestead.com..._horseman.html


Chain to jackshaft, belt from jackshaft to rear wheel.

Ectomorphs for the win!
That link shows how very complicated a hubless project really is.

My favorite part: "that way the go-roundy **** doesn't run over the air thingy".

That is covered. ;) Thanks for the suggestion though. If you read the thread I just linked you to, you would see that I am having trouble with the design of the roller driven system.

Do you have any prior experience building wheels, bikes, cars, etc? There seem to be some gaps in your understanding of mechanics.

you know you could just use a 2 speed cassette one with a small gear like a 11 or 12 that you attach your big chain gear to and the second gear be a chanring read like a 40 or 50 a weld a few old chains around the rim and put the second gear in the chain around the wheel

<_< i saw this on the road bike forum, neat idea but you'll go through so many head aches if you don't prototype things before you build the on the bike. . .

then again i am in college to become a mechanical engineer