New graduation of bar lengths

[neena]

Hello-

I'm working on customizing a glockenspiel design, making the bars wider (1-1/4" or maybe even 1-1/2"), and thicker... 3/8".  The bars will also have to be longer than the original design offered here.

I need to figure out how to create a new bar length graduation so that all the nodes will line up right on the frame.

Someone has told me that if I just "invent" the length of the shortest bar (Call it "S"),
 and "invent" the length of the longest bar ("L"),
 I can subtract the shortest bar from the longest bar and divide it by the number of bars ("N")
and the results will equal the amount ("A")
between what each bar length should be so the nodes will line up.  So, to look a little like algebra it would be:

("L" minus "S") divided by "N" equals "A" 

OR:

20"-10" divided by 20 equals a half inch.

(these numbers are just to make the example easy for me)

But yet, I think I may be missing something here. Maybe "N" should not actually equal the number of bars... but the sum total of all the widths of bars next to each other (either "white" or "black") plus the sum total of all those spaces in between those bars.

So... am I on the right track?  What am I missing?
Thanks! 
 

[Jim McCarthy]

You pretty much have this correct actually!
Yeas you can take a random length - or guess - for your top and bottom note.... just as long as the material you use at that length is appropriate to the note you need to end up with - so it needs to be higher in pitch by a reasonably significant amount so you can lower it to pitch during the tuning process.

Yes - in your case take your white note bars only.... and go from your hypothetical 10" to 20" - divide by NINETEEN - not twenty - the first bar in the row is your starting bar. The result is 0.53" and is the graduation. So bar one in 10" - bar two is 20.53" bar three is 21.06" etc etc.

If you like you can also do this by physically getting the measurements. Take your top bar and bottom bar and place their ends against a flat wall or similar - space them apart by 18 bar widths (the number of bar that will be between. Then you can take a ruler or other straight edge and line it up from the end of one bar to the other. - Now at each bar width along the wall you can measure from that point to the ruler and you will have your bar length for that bar.