Walter Rotary Table

[mklotz]

The plates need to be drilled and spaced for that ratio

It was the statement above that caught my attention.

If you understand what's required, that's all that's important.

[pete]

Funny enough, I have a Ebay search on for Troyke rotary tables, this morning I just noticed that some at least were, and maybe all of them are 120-1 ratio. Since there were a lot of tables made by Troyke, then maybe a bit of luck would get you a set of dividing plates from one of those? And Troyke was a very respected name for producing very high quality equipment.

But Marv as usual is correct, The handwheel gives you whole or partial turns. The dividing plates give you a preset location that's easier and less mistake prone than the index and vernier scale. The sector fingers give you your spacing without having to mentally keep track of all of it. 60-1 plates will work just as well for the actual dividing. Different turns and hole spacing would happen, but any simple calculator would give you the turns and spaces needed on the plates.

No doubt Marv's programs will figure all of this out. I'm too computer stupid to figure out how to open and use any of his programs on my computer.


Pete

[wlw-19958]

Hi There,

The plates need to be drilled and spaced for that ratio

It was the statement above that caught my attention.

It was that statement that caught my attention too.

Basically, I look at it as a math problem involving ratios and composite
numbers comprised of prime numbers. In your example of a 120:1 table,
120 is a composite number composed from: 2 x 2 x 2 x 3 x 5 = 120. That
means you can subdivide a circle into any number that can be derived from
those numbers in whole turns. You can look at it this way:

2 divisions require 2 x 2 x 3 x 5 = 60 turns for each division,
3 divisions require 2 x 2 x 2 x 5 = 40 turns for each division,
2 x 2 = 4 divisions require 2 x 3 x 5 = 30 turns for each division,
5 divisions require 2 x 2 x 2 x 3 = 24 turns for each division,
2 x 3 = 6 divisions require 2 x 2 x 5 = 20 turns for each division,
2 x 2 x 2 = 8 divisions require 3 x 5 = 15 turns for each division,
and so on...

In other words, (the number of divisions) x (the number of turns) = 120
(or whatever ratio your table is).

If you wish to subdivide a circle into sub-parts that cannot be derived from
the prime constituents listed above, then you will need a plate that has or
contains the needed prime number to complete the subdivisions required.
For example, if you want 18 divisions, (2 x 3 x 3 = 18), on your 120 ratio
table, (2 x 2 x 2 x 3 x 5 = 120), you will need a plate that contains a hole
circle that can be divided into thirds of a turn to make up the extra 3 in
the number 18.

Good Luck!
-Blue Chips-
Webb

[mklotz]

We're making this too complicated. This is why they taught you fractions in the sixth grade.

The number of crank turns (T) is given by:

T = G/N

where G is the gear ratio and N is the number of divisions.

For example 25 divisions (N=25) on a 40:1 table (G=40)

T = 40/25 = 1 & 15/25 = 1 & 3/5

We need to turn the crank one full turn plus another 3/5 of a turn. To turn 3/5 turn we need a hole circle where we can count off fifths of a turn. That means a circle of five holes or any integer multiple of five holes (i.e., 10,15,20,25,30... holes).

For a 120:1 table we have:

T = 120/25 = 4 & 20/25 = 4 & 4/5

It should be obvious that, if N is a prime, the denominator will end up a prime number and you'll need a hole circle with that prime number of holes. Let's look at N=17 holes...

T = 40/17 = 2 & 6/17

T = 120/17 = 7 & 1/17

There's no way to reduce that (prime) 17 in the denominator so you're going to need a 17 hole plate.



All those lengthy tables in MH and elsewhere are completely unnecessary if you can reduce a fraction. Hey, it ain't nuclear physics. If it's beyond your math abilities, most inexpensive (<$10) scientific calculators have a key (often marked 'ab/c') to do it for you.

[ctwo]

I love math! Does Windows calculator have that function? I could not find it...

[neanderman]

Funny enough, I have a Ebay search on for Troyke rotary tables, this morning I just noticed that some at least were, and maybe all of them are 120-1 ratio. Since there were a lot of tables made by Troyke, then maybe a bit of luck would get you a set of dividing plates from one of those? And Troyke was a very respected name for producing very high quality equipment.

Troyke is still in business here in Cincinnati, so they might be helpful, too.

[chucketn]

Marv,
The scientific calculator in Windows 7 does not have that function.

Chuck

[mklotz]

Marv,
The scientific calculator in Windows 7 does not have that function.

Chuck

I said cheap scientific calculator, not some piece of MS c..p software. Go to the local Big Lots, Walmart, or similar and look at the Casio calculators.

Amazon has them for $7...

http://www.amazon.com/Casio-FX260SLRSC- ... calculator

IMNSHO, every workbench and desk should have one of these as a permanent feature.

However, you really should learn to do this without the aid of the calculator.

[wlw-19958]

Hi There,

We're making this too complicated. This is why they taught you fractions in the sixth grade.

I guess it depends on what you consider "complicated." I think
understanding the underlying math will in the end simplify things.

For example 25 divisions (N=25) on a 40:1 table (G=40)

T = 40/25 = 1 & 15/25 = 1 & 3/5

We need to turn the crank one full turn plus another 3/5 of a turn. To turn 3/5 turn we need a hole circle where we can count off fifths of a turn. That means a circle of five holes or any integer multiple of five holes (i.e., 10,15,20,25,30... holes).

For a 120:1 table we have:

T = 120/25 = 4 & 20/25 = 4 & 4/5

It should be obvious that, if N is a prime, the denominator will end up a prime number and you'll need a hole circle with that prime number of holes. Let's look at N=17 holes...

T = 40/17 = 2 & 6/17

T = 120/17 = 7 & 1/17

There's no way to reduce that (prime) 17 in the denominator so you're going to need a 17 hole plate.



All those lengthy tables in MH and elsewhere are completely unnecessary if you can reduce a fraction. Hey, it ain't nuclear physics. If it's beyond your math abilities, most inexpensive (<$10) scientific calculators have a key (often marked 'ab/c') to do it for you.

That is what I more or less said in my first post on the first page
of this thread.

Good Luck!
-Blue Chips-
Webb

[pete]

Ed,
That's good to know Troyke is still in business, I obviously got some wrong info since I thought they had closed up shop.

Pete

[shootnride]

Funny enough, I have a Ebay search on for Troyke rotary tables, this morning I just noticed that some at least were, and maybe all of them are 120-1 ratio. Since there were a lot of tables made by Troyke, then maybe a bit of luck would get you a set of dividing plates from one of those? And Troyke was a very respected name for producing very high quality equipment.

Hi Pete,
Great tip about the Troyke rotary tables. I will do some research in that direction.
Thanks a lot,
Ted

[shootnride]

This morning I was using Google to try to find some information about my rotary table and up popped my post on this forum from back in 2012. Well, I noticed that I never did a follow-up after I received all of the great feedback from the folks on this forum (I hate it when people do that, and apparently I'm one of them !). So, anyway, just thought I would do it now to show a little belated courtesy.

I did locate some dividing plates on eBay for a very reasonable price that would work well with my RT so after purchasing those, I did a little machining on them and fabricated the rest of the components to complete the dividing assembly. It all came out pretty good and works well. So now the RT will also function as a reasonable facsimile of a dividing head when needed. Here's some pics of the components.

Ted