[Jukebox-list] Rockola Tempo2 Speed

[Bill Signor]

Ray,
Remember I'm new at this...but it would seem to me if you have an idler 
wheel with the rubber lip worn abit that could cause slippage, thats why the 
fabric tape helps it grasp more and corrects the speed.

While all you guys hash this over, I'm playing my 45's with the tape on the 
rim. When the final results are in I'll make
the change!.Hopefully we'll all learn from this Appreciate all the input!

Bill in Warwick
----- Original Message ----- 
From: "Ray Finch" <babylon at swcp.com>
To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
Sent: Monday, November 05, 2007 9:11 PM
Subject: Re: [Jukebox-list] Rockola Tempo2 Speed


>I thought the size of the idler wheel would make a difference, but thinking 
>it through I see that it does not.
>
> Leaving the math aside, think of it this way:
>
> If you think about the outer surface of the idler wheel, as the motor 
> shaft is turning there is a certain amount of rubber that has to pass by. 
> With the motor speed being constant, the larger the idler wheel more 
> rubber that passes by and the slower the wheel turns.  So far so good, but 
> that's where people get hung up.
>
> Although a larger wheel will indeed turn slower (because it is bigger and 
> so has more rubber that has to pass by) the actual _surface speed_ of 
> where the rubber wheel contacts the motor shaft can't change - if it did 
> then there would be slippage.  Since the wheel if fed by the size of the 
> motor shaft, the _surface speed_ of the wheel will be the same no matter 
> what size the wheel is.
>
> It's a bit like trying to explain why the middle of a record turns slower 
> than the outside edge when the whole record is turning one speed.
>
> In order for the physics to work out, a larger wheel has to move slower to 
> cover more rubber going by on its outside surface.  By the same token, if 
> you have a smaller wheel, it will turn faster *only* because there is less 
> rubber going by on its outside surface.  None the less, the outside 
> _surface_ of the wheel is will still be the same speed regardless.
>
> So, since the surface speed of the wheel is always the same and that 
> surface is in contact with both the motor shaft and the turntable it 
> doesn't matter what size the idler wheel is or what speed it "appears" to 
> be going as the surface speed does not change. The mechanical advantage 
> does _not_ come from the size of the idler wheel, but rather from the size 
> of the turntable and the size of the motor shaft.
>
> 2 cents,
>
> Ray Finch
>
>
>
>
> On Mon, 5 Nov 2007, Ron Rich wrote:
>
>> Bob,
>>  I gave up long ago trying to 'splain" that the wheel size is not 
>> relevent--no one seems to ever believe it !  Ron Rich
>>
>> Bob Ellingson <bobe at halted.com> wrote:
>>  At 02:52 AM 11/5/2007 -0500, you wrote:
>>> Bill, keep it simple. If the tape increased your speed to the correct
>>> speed, that tells you that the ratio is slightly off between either the
>>> motor end piece which engages to the idler wheel, or the idler wheel is
>>> slightly too small.
>>
>> The size of the idler wheel will not matter! If you calculate
>> the ratio of the idler wheel to the motor spindle, and then
>> the ratio of the turntable to the idler, you will see that it
>> cancels out:
>>
>> Spindle Idler Spindle
>> -------- X ---------- = --------- = Speed
>> Idler Turntable Turntable
>>
>> The problem has to be friction, slippage, or mis-match
>> of the spindle-to-turntable size. This isn't in a 50 Hz
>> area, is it? Maybe the spring that enlarges the spindle
>> for use in foreign areas has fallen off?
>>
>> --Bob
>> =======================================================================
>> Bob Ellingson bobe at halted.com
>> Halted Specialties Co., Inc. http://www.halted.com
>> 3500 Ryder St. (408) 732-1573
>> Santa Clara, Calif. 95051 USA (408) 732-6428 (FAX)
>>
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