41 replies to this topic

[Uncle Fred]

That's only if the idler gear is the same size. This car has four different size gears.

[Cheater]

Fred,

No sir, that is not true.

The gear ratio that exists on the input side of an idler gear is reversed on the output side.

Another way to view is is that when the first gear moves the idler one tooth, it also moves one tooth on the following gear.

From Wikipedia:

"An idler gear does not affect the gear ratio between the input and output shafts. Note that in a sequence of gears chained together, the ratio depends only on the number of teeth on the first and last gear. The intermediate gears, regardless of their size, do not alter the overall gear ratio of the chain. But, of course, the addition of each intermediate gear reverses the direction of rotation of the final gear."

[Uncle Fred]

Perhaps it's the definition of an idler gear that's the problem here... This system does not have just one gear but is attached to shaft with a different size gear on it. It is not really a simple "idler gear".

[Cheater]

I'm willing to listen, Fred, but so far you're not convincing me...

 

Perhaps you could mock up the gear system you're seeing and actually test my claim?

[Uncle Fred]

I see that a simple idler gear does not change the ratio, when it is between two gears, but there is a shaft with a different size gear on it attached to the idler gear with a different number of teeth on it.

[Gator Bob]

A gear train with intermediate gears set at 1:1 becomes an idler set-up not effecting the original Drive/Driven ratio.

Varying the tooth count on the intermediate gear set will change the final drive.

 

I think either method works on slot cars.

 

Full Definition of IDLER GEAR

1:  a gear placed between a driving and a driven gear to transfer motion without change of direction or gear ratio  

[Cheater]

Fred,

 

The more I think about it, the more I think you are correct.

 

What that dragster has is two "chains" of gearing that are geared together.

 

Bob, 

 

The definition you posted seems inaccurate to me.

 

The direction of rotation of the final driven gear is determined by how many idlers are interposed between the initial driving gear and the final driver gear.

 

If there is an odd number of idler gears, the final driven gear rotates in the same direction as the driving gear.

 

If there is an even number of idler gears, the final driven gear rotates in the opposite direction as the driving gear.

[Cheater]

Fred,

 

Looks more and more like you are correct.

 

See this LINK.

[Uncle Fred]

Thank you, Greg.

[George Blaha]

Hey ya awl,

 

There are no idler gears in this setup – they are all driven gears – loosen the setscrew on any one of them and you'll have no movement of the vehicle – therefore no idler gear or gears. Assume the outer ratio is 2:1 and the inner ratio is 2:1, then the overall gearing is 4:1. 

 

George Blaha

[Uncle Fred]

Perhaps it's the definition of an idler gear that's the problem here... 
 

[Uncle Fred]

George,

 

I'm sure you recall the Magwinder chassis I gave to you because I deemed it too flimsy. You built it up with a Pittman 85 that worked pretty well.

[Cheater]

George,

 

Please see this LINK.

[Gator Bob]

What that dragster has is two "chains" of gearing that are geared together.

Bob, 
 
2. The definition you posted seems inaccurate to me.
 
The direction of rotation of the final driven gear is determined by how many idlers are interposed between the initial driving gear and the final driver gear.
 
3a. If there is an odd number of idler gears, the final driven gear rotates in the same direction as the driving gear.
 
3b. If there is an even number of idler gears, the final driven gear rotates in the opposite direction as the driving gear.
 

1. Gear 'chains'... Sprockets ???
 
2. Take that up with - Merriam Webster.  
 
3. Result may vary.

[George Blaha]

once a cross is rotating at a reduced speed this now becomes the output speed of the motor and you go thru a second set of gears that are not a 1 to 1 ratio (I assume we are talking about the magwinder) the gear that is driving the final rear end gear is smaller and therefore the speed of the rear gear is reduced again by the ratio of input gear to output gear. the overall ratio will be determined by multiplying the out side gear time the inside gear. I have read the post suggested.  Physics is physics.

 

George Blaha

[Uncle Fred]

Here we go............. Does the squeaky gear get the oil?

[Gator Bob]

Jack Shaft.