Author Topic: Rhodes Tine Length Curve  (Read 244 times)

Offline cinnanon

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Rhodes Tine Length Curve
« on: February 10, 2019, 03:43:51 PM »
Hi all, i've been searching and searching for this topic and couldn't find anything.  If you can link me to a previous topic that would be much appreciated. I apologize if it's been discussed before.

My question is in regards to the tine length charts that i've seen. Is there any reason why they are not nice smooth curves? Instead they look like someone traced them after the fact. Was it so that someone could use a ruler and the lengths were rounded to nearest fractions?

The nerd in me wanted to find a formula for the curve, so I threw all the tine lengths I found in a previous post in excel to see which tines had the most "error" in lengths.

The formula I found to fit the best was an exponential formula, and it came out to

y=7.573e^-.027x

where "x" is the key number and "y" comes out to the length. In this formula "e" is Eulers number (2.71828), not "times ten to a power"

What I found is that the tine lengths are on average .027" off. The one I found to be the farthest off is key 19. It is .081" off of the curve. The closest one was within .001", key 42.  I can't upload my spreadsheet but i'll post a picture later.

« Last Edit: February 11, 2019, 09:31:50 AM by cinnanon »

Offline pnoboy

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Re: Rhodes Tine Length Curve
« Reply #1 on: February 10, 2019, 04:56:08 PM »
I think that one thing that will throw off the smooth curve you are looking for are the tuning springs.  At different points within the compass of the piano, Fender uses different weight springs.  These different weights change abruptly, i.e., the springs immediately transition from one weight to another--they don't change in some smooth manner.

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #2 on: February 10, 2019, 07:30:17 PM »
That’s right! Is there a chart somewhere with those changes? I see VV has one, is there an original one?
« Last Edit: February 10, 2019, 07:32:06 PM by cinnanon »

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #3 on: February 10, 2019, 07:40:03 PM »
I see only one change in the manual between notes 33 and 34. VV has five different tuning springs.

Offline sean

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Re: Rhodes Tine Length Curve
« Reply #4 on: February 11, 2019, 09:40:30 AM »

I don't understand your formula.  Does the caret indicate an exponent?  Did wordpress garble your formula?
Hmmm... e would normally be 2.71828....

In the four pianos that I have, there are three tuning spring sizes.  The bass notes have the thick springs, then transition at tine #23 (G) to the thin spring with 5 windings per leg, then transition to the small spring with three windings per leg at tine 41(C#), 42(D), or 44 (E).
My springs are shown at https://ep-forum.com/smf/index.php?topic=9799.msg54387#msg54387

I constructed my own tine cutting chart:  https://ep-forum.com/smf/index.php?topic=9647.msg53350#msg53350
This was transcribed from the tuning chart posted at the end of the Vintage Vibe copy of the Service Manual. 
Vintage Vibe's link to the Rhodes Service Manual:  https://cdn.shopify.com/s/files/1/0666/2821/files/Rhodes_Manual.pdf?6596484715058753348

However, I prefer to cut my tines a little bit longer than the chart indicates, and push the tuning spring a little bit further down the tine.  At one point, I thought I had the energy to compare the tone with the tuning spring very close to the end, and the tone with the tuning spring well away from the pickup.  But I was wrong, I don't have the energy to test and document that.

Sean

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #5 on: February 11, 2019, 10:01:32 AM »
Yes I missed the "2" in that constant.  I corrected it a bit ago. The caret is an exponent yes.

I actually did use your tine cutting chart information from that link below. Since the VV tine chart didn't have lengths, I didn't bother.

What i'm doing is probably overkill for sure. I thought maybe there were certain notes with undesirable harmonics or resonant frequencies at certain lengths so they were altered.


Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #6 on: February 11, 2019, 10:05:55 AM »
So the chart you transcribed goes to the resolution of 1/64 of an inch (.015625"), which should be plenty good enough for a good smooth tine length curve. I'll take into account the tuning springs also. Are all tines the same base tine, just cut to length?

Offline sean

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Re: Rhodes Tine Length Curve
« Reply #7 on: February 11, 2019, 10:18:44 AM »

Yeah, same tine, just cut to length.


I still don't understand your formula.   Can you show me the calculation for the length of a tine, say tine #13?

y = 7.573 times ((2.71828 to the negative (.027x)) power?

y = 7.573 times the [.027x]th root of e?

Sean

Offline sean

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Re: Rhodes Tine Length Curve
« Reply #8 on: February 11, 2019, 10:21:58 AM »


Oh, holy crap.  It works!

5.331" for tine 13

Sean

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #9 on: February 11, 2019, 12:49:48 PM »
Yea! The chart says 5.344” for tine 13, which is almost negligible difference. I wonder if the differences are due to the type of tuning that was used (perfect thirds vs perfect fifths or whatever they are)
« Last Edit: February 11, 2019, 12:51:27 PM by cinnanon »

Offline sean

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Re: Rhodes Tine Length Curve
« Reply #10 on: February 11, 2019, 03:17:55 PM »


Interesting little exercise.  But I wouldn't use the formula.  Use the chart. 

Not worth the risk of cutting a tine short. 

Sean

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #11 on: February 11, 2019, 04:12:01 PM »
Totally agree. I'm just using the formula to find a "best-fit" curve to determine if the tine lengths have error, or find out why they are the way they are.

Offline AvionKeys

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Re: Rhodes Tine Length Curve
« Reply #12 on: February 13, 2019, 01:27:51 PM »
I agree with Sean about leaving them a hair long, more room for tuning!

This math is pretty cool. Now do the Wurlitzer reeds!  :o

Offline cinnanon

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Re: Rhodes Tine Length Curve
« Reply #13 on: February 13, 2019, 03:11:34 PM »
I believe DocWurly already has that!

Offline AvionKeys

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Re: Rhodes Tine Length Curve
« Reply #14 on: February 18, 2019, 11:26:10 PM »
Ahh cool, thanks! Just looked it up. So curious to have that dimension be linear. I wonder what the curve of the solder blob weight looks like. Very cool.

Cheers!
M