How does the mechanism of a small stationary bike (without a belt) work?

[ValeryV]

While the mechanism of general stationary bike with a moving belt is more obvious, the following mechanism for a more smaller version eludes me. Does anyone have an idea what's inside there, and how does the dial change resistance level?

 

[ValeryV]

Hmm after a bit more research I realize this is friction mechanism

 

[Artisi]

Amazing.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[ValeryV]

Ok, Sherlock, would love to know what you think

 

[chicopee]

So if it is a friction mechanism, after a good work out that housing should get pretty warm.

 

[robyengIT]

another possibility is a magnet close (adjustable) to a rotating iron pipe

 

[IRstuff]

I think there's insufficient volume for eddy-current to work. The price is also too low for that type of mechanism. The cheapest eddy-current bike runs about triple the cost of the bike shown on Amazon.

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[capnhook]

You crank that little knob on top, then go for a sandwich..

Proud Member of the Reality-Based Community..

[green]To the Modelmaker, your nice little cartoon drawing looks cool, but your solid model sucks. Do you want me to fix it, or are you going to take all week to get it back to me so I can get some work done?[/green]

 

[Scuka]

The dial has a friction pad on top and it grinds against the shaft of the pedals. Tighter you turn the dial, the more friction you get.

It's a common way stationary bikes achieve resistance.

 

[rb1957]

where's the rest of the bike ?

another day in paradise, or is paradise one day closer ?

 

[SuperSalad]

I can speak from personal experience on this exact model since I bought one at a garage sale a few years ago.

Scuka is exactly right on how it mechanically works (at least initially; more details below). Chicopee is exactly right if you exclude "a good workout" as it warms up instantly (at least initially; more details below).

If anyone were to ask "How does it work?" the answer would be "terribly". It broke after just a few uses and just freewheeled offering no frictional resistance nor heat buildup. It was worth all of the $5.00 I spent on it for entertainment purposes alone though.

Andrew H.

http://www.mototribology.com

 

[IRstuff]

My old elliptical cycle used a friction belt. After we got a new one, I took the old one apart and could see shreds of the original belt remaining; it would have died PDQ had I kept using it.

One thing that's annoying about the friction approaches, of course, is that as you progress, you want to increase the resistance, which makes it wear out quicker.

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[chicopee]

Instead of a friction pad, I would have designed the mechanism to emcompass roller bearings with a crank to put pressure on the shaft connected to the pedals

 

[dvd]

The only way that pushing against the shaft produces resistance is with friction. Bearings pressing on the shaft won't provide enough frictional resistance. Power in = power out, where the input power is the person exercising and the output power is heat dissipation. Low friction bearings pushing on the shaft don't create any heat to dissipate the input power.

 

[3DDave]

The trick is to get the surface finish smooth enough that there is friction without significant wear. Since that costs money, it won't be seen in this application.

 

[SuperSalad]

3DDave,
It isn't a lack of money getting in the way of that material's development. If it did, motorcycle clutch mfgs. and brake pad mfgs. would have a much improved products. Or were you saying the application of some of the materials used in an application like a automotive brake pad? I would assume the friction pad on this gizmo was probably either a curved piece of metal or a rubber bicycle brake pad.

Andrew H.

http://www.mototribology.com

 

[3DDave]

Hey SuperSalad, surface finish <> material. Plus this is about a cheap pedal mechanism. Feel free to start a new topic.

 

[SuperSalad]

Um......ok. I'll assume you meant the latter then. Yeah, it didn't use any expensive material meant for durability. It squealed a lot so I assume metal-on-metal, though that may not necessarily be accurate.

Andrew H.

http://www.mototribology.com