Here's Something New To Me
 

Picked up a Schwinn Cimarron in neglected shape this weekend.

Something's going on with this one.

http://farm9.staticflickr.com/8036/7...bb27c671_b.jpg


OK, it definitely has a homemade guard on it.

But look closer.

How many chainrings on this bad boy?

Here's the back side.

http://farm9.staticflickr.com/8034/7...af799f23_b.jpg

First time I have seen this mod.

I noticed the crazy guard when you first showed it off, but I missed the extra ring :eek: It looks like the owner had some trouble keeping the chain on, that chainstay is gnarly! I hope you don't find many more homebrew modifications.

Well alrighty then! Never seen that either

A Fourple!

No wonder he had a chain guard on there. When you consider the fourth ring was just stacked on top of the outer ring, chain was really close.

BB was gnarly as well. Going to try to save this one just for the heck of it. Certainly will not make any sense financially.

http://farm9.staticflickr.com/8305/7...5e665f23_b.jpg

Looks like the previous owner was using the extra ring as a chainguard, the chain certainly could not shift to that with the half-plate bolted to it. Just take all that off and it should be fine.

Oh, yeah it will. That was *the* best steel MTB frame Schwinn could make. DB Cro-mo, tigged and fillet-filled head joints and lugs everywhere else, all the braze-ons a man could want, good geometry.... they're quite desireable.

Can you give me a tooth count on the freewheel? I ran the chainrings through the gearcalc, I think I see what the builder was driving toward but it's just conjecture at this point. Looks like the inner two are step-and-a-half, while the outer two are half-step. It actually makes a good bit of sense.

Unless there's a spacer behind the guard, then you've got I really high top end onthat puppy. Will the FD lift the chain onto it?

If it functions as a Chainring, that's a pretty cool mod indeed. I wonder what the 1/2 guard was for? Maybe to keep the chain from jumping clean off the other side?

He had two washers, under that home made chain guard, as spacers. Also had a regular spacer (like you find behind the small ring), between the outer ring, and the added fourth ring.

53/48/38/28 chainrings, large rear sprocket was a 32, small was 13 (I am too lazy to count the other four).

He also had a similar guard on the rear cassette.

Odd to see a Shimano cassette on a Suntour XC hub. More digging on this one to come.

Do the lights work?

"This one goes to Four.........."

PO got the FD to work by totally removing the high limit screw. It made it.

I believe that the half-moon chainguard is a minimalist design that shields only the portion of the big ring where a rider's pants leg would fall down upon and snag the teeth. That shows a thinking tinkerer for sure.

Generally, half-steps up to the big ring have at least as much to do with shifting performance (up to and down from the middle ring in the case of a triple) as they have to do with gearing preference. Old-style plain chinrings don't lift and drop the chain aggressively unless some degree of half-step-plus-granny is used for the sprocket selection.

I've seen quads before, but those added the 4th ring to the inner side instead of like this one.

One thing to note is that current gearing hardware could have us trending toward a narrow 4-ring crankset!
Firstly with 11-speed chains, and secondly with the arrival of the electric indexed front derailer.
Additionally, as a "racing quad" with only modest 7 or 8-tooth jumps between sprockets, the sprocket spacing can be narrowed toward what is used on rear cassettes, much narrower than typical chainring spacing. Thus a modern quad could be no wider than a 9-speed triple.

And, with electronic coordination of the front and rear shifting, one could realize a very large number of closely-spaced gears, with near-perfect chainline maintained continuously and automatically for a real increase in efficiency.

As for the added weight of a close-ratio quad, witness the one-piece CNC cassettes which have adjacent sprockets fully supporting one another, for structural efficiency i.e. high-performance design.

Now ya gotta save it... otherwise it would be like shooting a perfectly good 5 legged horse

My car has a CVT (continuously variable transmission)... I wonder if we'll ever see such a feature on a bicycle.

Cool old Schwinn, have fun with that one!

+1

They are already out there. A few years ago, one of the inventors was working with Cannondale, and the CVT was inside the rear hub. I'm not sure how those Landriders work, either.

Bill, that looks like one of those "compact" triples often found on triple RSX setups, then with the outer ring added. I like it. That is a lot of shifting, but you can climb anything, run fast, and pretty much everything in between.

:roflmao2: