dynamic gears

[tecnos]

hello

is there any mechanism with gears that have dynamicly variable diameter?

thanks!

 

[Jboggs]

Short answer: No. How would that even be possible?
Longer answer: There are mechanical drives with variable speed ratios, but no gears are involved. Google Mechanical Variable Speed Drives.

 

[1gibson]

Are you asking about a CVT, continuously variable transmission?

 

[drawoh]

tecnos,

There are gears out there that are not round. The radius varies as the gear rotates. Of course, you have no control over this as the machine rotates.

Google non-circular gears.

--
JHG

 

[3DDave]

I've seen sprocket designs for use with chains that vary their size. There are also friction drives that are gears with atom-sized teeth.

Something of particular interest?

 

[tecnos]

Thanks, CVT seems close to what I was thinking of. I didn't knew it already existed.

 

[tecnos]

but instead of doing it with a belt, could you do it with an actual gear?
somehow to increase the diameter of a gear (by axons positioned as radii)?
can you imagine this happening somehow?

 

[1gibson]

If you use a gear instead of a belt, then tooth count matters more than diameter. Can't really grow more teeth on a gear.

Ever seen a multi-speed bicycle?

What are you trying to do?

 

[fegenbush]

In addition to what 1gibson said, the tooth form also changes with the pitch diameter for an involute. The tooth form for cut gears can be used for a narrow range of pitch diameters. Outside of those ranges, the tooth form is inefficient, at best.

 

[tecnos]

'Can't really grow more teeth on a gear.'

why can't you have the teeth increased in number with a mechanism? that will expand the circumference of the gear and at the same time, more teeth will somehow emerge?

I am not trying to do something specific, I am just trying to conceptualize that: a gear with variable diameter

applications can be various, once we can conceptualize it

 

[1gibson]

Because it isn't practical. The correct question to ask isn't "why can't you" it is "how could you?" You can increase the teeth with a mechanism, look at a bicycle. You can't do it on a single gear. I'm just now realizing that you are the magic car person...

Engineering is about solving problems practically and economically. If you don't have a problem to solve, or any regard for those concepts, I don't think I have anything else to add. Sorry.

 

[tecnos]

@1gibson
what do you mean magic car person?
maybe you were also saying that a continuously variable transmission box cannot exist? or could not imagine the mechanism to create it?
Engineering is solving problems, but innovation is about exploring the unknown.

 

[1gibson]

I was referring to the only other thread you've started.

I'm not saying a CVT can't exist, if you scroll up you'll see where I point out the fact that they already do.

You may want to look for an innovation forum. Fair warning, it's difficult to explore the unknown if you don't know the known.

 

[tecnos]

Thank you all for your input.

 

[1gibson]

Can't argue with that logic, so I guess you win. I'll disappear into the sunset now and let you get back to your thread. Sorry for the reality check disruption.

 

[3DDave]

I think I can solve the problem using sentient liquid metal that I will ask to change diameter.

Now all I need is someone to imagine a way to do that and I'm good to go.

 

[fegenbush]

Separate question(s):
-If you can change the pitch diameter of the gear (and increase/decrease the number of teeth), how will the mechanism be able to handle the change in center-to-center distance of the gears in question?

-Does a coupling able to handle significant radial displacement/misalignment also need to be invented?​

-If you can change the number of teeth of the gear (and increase/decrease the pitch diameter), would you need to increase the tooth count by a whole number multiple of the original number of teeth?

If you increase the tooth count by one, the other teeth will need to be able to redistribute themselves equally around the circumference in order for the gear to remain round.​

 

[hydtools]

Well let's see. A discrete tooth inserted or removed and a descrete change in pitch diameter accompanied by a descrete change in rotation center. Can it happen while engaged or can the driveline be stopped to allow the gear to change and then re-engage? One tooth at a time or an interger multiple of teeth at a time? Tooth pitch would be constant, pitch diameter would not.

Ted