Thanks for the fast reply Biff. The odor you smell is my brain melting trying
to figure out the logic, math and commands on this infernal machine. I'll try
to copy a bit of what I've got on here and we'll go from there.

These are my input data items:

CATEGORY DATA IN
Input RPM = 1725.00 <-- Known rpm
Output RPM = 150.00 <-- this is the target rpm
Ratio = 11.50 <-- calculated... 1725/150=11.5
min pulley size = <-- ignore these 2 for now
MAX PULLEY SIZE =

From which I calculate available ratios (this is real primative at the
moment):
WHEN RATIO CALCULATED RATIO 1 RATIO 2
1 2:1 FACTOR TREE 4 PULLEY /2 5.75:1
2 3:1 FACTOR TREE 4 PULLEY /3 3.83:1
3 4:1 FACTOR TREE 4 PULLEY /4 2.88:1
4 5:1 FACTOR TREE 4 PULLEY /5 2.30:1


And this is my ratio calculator worksheet:
Pulley diameter ratio:

DRIVER dia. DRIVEN dia.
1.0 1.5 2.0 2.5 3.0..........
1.0 1.00 1.50 2.00 2.50 3.00
1.5 0.67 1.00 1.33 1.67 2.00
2.0 0.50 0.75 1.00 1.25 1.50
2.5 0.40 0.60 0.80 1.00 1.20
3.0 0.33 0.50 0.67 0.83 1.00
..
..
..Where DRIVEN/DRIVER = ratio

And these are my rpm out worksheets:

RPM 1

DRIVER(1) DRIVEN(1)
1.0 1.5 2.0 2.5 3.0......
1.0 1725.0 1150.0 862.5 690.0 575.0
1.5 2587.5 1725.0 1293.8 1035.0 862.5
2.0 3450.0 2300.0 1725.0 1380.0 1150.0
2.5 4312.5 2875.0 2156.3 1725.0 1437.5
3.0 5175.0 3450.0 2587.5 2070.0 1725.0


RPM 2

DRIVER(2) DRIVEN(2)
1.0 1.5 2.0 2.5 3.0......
1.0 1725.0 1150.0 862.5 690.0 575.0
1.5 2587.5 1725.0 1293.8 1035.0 862.5
2.0 3450.0 2300.0 1725.0 1380.0 1150.0
2.5 4312.5 2875.0 2156.3 1725.0 1437.5
3.0 5175.0 3450.0 2587.5 2070.0 1725.0


1.0, 1.5, etc. represent pulley diameter and 1725.0, 2587.5 etc. represent
output rpm(input RPM/(DRIVEN/DRIVER)). The table continues out to 30"
diameter in both the "driver" column and the "driven" row

At the moment I'm thinking of using 2 identical rpm worksheets (for a 4
pulley system) and making Excel spit out whatever combination of the 2
worksheets produce the target output rpm. The other option(I think) is to use
a command to loop through the same worksheet twice to get the combined output
rpm.

I realize there might not be an "exact" match for the output rpm, but if I
could choose between combinations that produce within 98%-100% of the target
rpm that would be close enough.

I didn't include the min and max pulley size data in the first question
because I think that'll be easy to solve compared to the rest.

Thanks again for the reply and let me know if this is enough data,

Rob




"T. Valko" wrote:

This is something I would need to see to understand what's going on. The
basic lookup is no problem but you have all those calculated conditions that
need to be dealt with. If you don't get any other replies that solve the
problem and you are willing to send a copy of the file to me I'll see what I
can do. Let me know in this thread if you want to do that.

--
Biff
Microsoft Excel MVP