This bike has funny frame.

The bike is Autobike Classic...it has 6 gears and changes automatically without shifting, but has normal rear derailleur and cassette/freewheel. And all those plastic things on the rear wheel spokes.

Not mine, lucky me.

It does look like it is ready to snap in two, doesn't it?

The top tube definitely has an extra pressure point.

Cannondale had a similar frame years ago. In aluminum. On a mountain bike. They had no issues.

not mine

While not my thing either, there isn't anything wrong with those bikes. The auto-shifting mechanism is a little finiky, I've heard, but that's what the plastic weights are - it uses centripital force to change gears, I assume using a low normal rear derailleur.

And the second triangle should make the frame stiffer at the expense of weight.

Yeah, they work. But you don't have any control over the shift points. And the mechanism adds weight and complexity to the bike. All in all, a solution in search of a real problem.

I've mentioned before that when I bought my first mountain bike back a little over 25 years ago, I noticed at the store an aftermarket automatic shifter that you could bolt onto just about any multigear bike. Somehow it would automatically shift the rear derailleur as needed to provide even gearing. No, I did not buy it because it looked awful cumbersome and I didn't really see any advantage over manual shifting. Plus I like being in control of when the gears shift.

And no, I don't have any idea how the mechanism worked. It's been too long and I didn't look that closely at it.

Ah, the Autobike! Last month, I left one on the curb in a college town with a "Free" sign on it. It was gone in a half hour. Goofy bikes!

In both cases (the pictures above) I don't get it. Why not just make a straight top tube? Is that a gimmick? It just looks overdone.

Dan

This frame design adds at least 6" more tubing and two additional tube junctions vs a regular diamond frame. For what benefit?

Larger head tube (even seat tube in some) and a lower stand over? I don't know, just guessing. Or they just wanted something different.

Loved those old C'dales. Lusted after them back in the '90s but couldn't afford one.

Looks like the frame was designed for proper head and seat tube length while accommodating less confident riders who jump down from the saddle to straddle the bike when stopping. Less likely to crush Johnson and the twins, compared with a horizontal top tube.

A simple compact frame with sloping top tube would require an unusally long seat post extension for some long-legged riders (my Globe Camel seat post is fully extended for that reason). The Autobike and Cannondale frames appear to be an effort to resolve that issue.

Fixed it. We see them from time to time at my co-op. The rear wheel weighs in at around 10 lbs. I think the frame is made from surplus dwarf star metal that was once used to make Schwinn Varsity frames. These things have a noticeable gravitation pull.

In the case of the Autobike, the frame is made that way so that they can fit the maximum number of height ranges to a minimum number of frame sizes.

The Cannondale, on the other hand, has the shock in the headset and needs a certain length to contain the internal parts of the shock. For smaller frames, they couldn't just run a straight tube and still have a bike that anyone under about 6' can stand over. Cannondale's Headshock is a somewhat good idea...having only one slider moving makes for a stiffer fork...but it has severe limitations in application.

Yes. Looks like it's collapsing down at any moment...like fighting against gravity.

Autobikes are very rare here in Finland, that's why it caught my eye. First one I've ever seen. For sale on Tori.fi selling site and looking to be in good condition with the exception of the paint on tt and st. Of course exceptional frame geometries are seen some time to time (like Mercedes Benz etc.).

There's a LandRider auto shift, it needs though a plastic v-belt disc to control a v-belt behind the freewheel. Interesting derailleur though, no other wires needed for shifting. Shifts when pedaling harder, troubles might come when on smallest cog and you have to maintain certain speed:
LandRider Auto Shift derailleur

And Bikemanforu has done at least two videos about this thing to the Youtube...

That's an interesting design. The one I remember (as best I can remember) came with a bracket that mounted on the drive side of the rear wheel, and likely operated on a similar principle. But, as I said, that was around 25 years ago, I've slept since then, and I didn't look at it closely enough to figure out how it worked when I did see it.

I still say there's nothing wrong with manual shifting that requires an automatic shifter. I can imagine if it were a $19.95 "as seen on TV" product the commercials would have all us cyclists in black & white struggling like crazy to shift gears on our bikes.

I don't understand why that page called centrifugal force "mythical," though, since it is very much real.

Fictitious force is a proper term, also called an inertial force or pseudo force.
https://en.m.wikipedia.org/wiki/Fictitious_force

Because from a simple dynamics perspective, there is no centrifugal force, it's the centripital force that changes an object's direction. A mass will stay in straight motion in absence of a force.

Here is one more. This geometry was actually more common on childrens bikes. Monark 20-24" wheels or so. See the rear fork...and cable routing from brake calibers.

Cannondale's geometry looks much more stable.

Yes, as far as I have seen, it is actually quite handy. When you learn to keep steady speed with it, the riding could be a lot of fun. I live an area where is a lot of hills. If only the asking price had been lower, I had bought it to look more specifically how it works and the reliability.

+1