Project "Groove Scribe"- A DYI stereo 45/45 head.

[Snug Music]

You're doing a pretty good job Bryan.
I find it remarkable that you have patience with this project, which is truly amazing.
A beer for you !!!

Best regards from West-Germany

Scotty

[EpicenterBryan]

I find it remarkable that you have patience with this project, which is truly amazing.

It's just that I hate to give up...

I think I have a solution. As it turns out I don't have enough aluminum left to move the mounting holes. I had drilled out the magnet holes for a different magnet I was going to use early on and there is just no meat left.

But I came up with this adapter! Next up, I've decided to go with phosphor bronze for the X spring (which is on order). I have some brass sheet in a few sizes that I may try out while I'm waiting for the other stuff.

Check this out... You can see where the X will mount. These adapters were for fit checking. The actual ones will be a little different but there is room now to attach the X springs!

IMG_4546.JPG

[Bahndahn]

Hey Bryan,

I've been checking back here ever so often to see what's going down, and I've really been enjoying your updates. You are so close you can probably hear it!

Seeing your progress is getting me excited to begin work on my cutterhead in the summer, as this semester for me has been entirely devoted to building a precision metal-cutting CNC router/mill. Two more weeks to go:

photo 2 (4).JPG

Keep up the great work, Bryan!

[EpicenterBryan]

...I've really been enjoying your updates. You are so close you can probably hear it!

I'm not sure if you listened to the posted test cut or not. If not, it's worth doing especially to compare with the next one. Not too bad, but lacking channel separation which was disappointing to say the least.

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I thought you guys might like to see why I had to make the adapters. As I mentioned, originally I was going to use larger magnets and drilled large holes for them in the head body. But they also had larger center holes. So the coils were going to be on carbon fiber bobbins of a larger diameter that would slide over the push rods and get glued. Somewhere in there, I decided to change out the magnets for ones that were longer, stronger, and had a smaller inner diameter. Using these, I could reduce the mass of what moved through the magnetic field since the coils would also be smaller, and there would be no bobbin if I wound the wire directly on the push rods.

In the first shot you see the outside of the head body, the hole for the larger magnet, the smaller magnet being held by the adapter on the other side, and the press fit nuts I installed tonight for the adapter. In the second shot you see that there was no aluminum left because of the large magnet hole to move the X spring closer to the center of the driver so the screws could be installed without interfering near the center top of the head. The plastic X spring is only there for illustrative purposes. You can see there was no aluminum available to drill holes in that area. Obviously, if I started from scratch, that hole for the magnet would be the right size.

IMG_4547.JPG

IMG_4548.JPG

That's the experimental nature of this whole project. If I were a mechanical engineer I guess that mistake would not have been made. But it's not a bad fix...

Now imagine an X like shown being made of a non-magnetic spring material being mounted inside the head on the adapter and attached to the driver rod. That's what the adapter is all about. This should result in much improved channel separation.

Bryan

[EpicenterBryan]

A quick update for this Sunday night.

I made five "X" springs out of 0.1mm stainless shim stock. The other stuff has not arrived and is non magnetic but I grew impatient. I also drilled holes in a long strip of the same stainless material to make an additional 5 springs as shown on the left. As you know, I always make extras so I can use the best 2 of anything I make.

Here is what they look like installed. On the top side is a dummy driver for fit checking where you can see the 3mm OD rod inserted in the X spring.

IMG_4555.JPG

What I found was some of these "X" springs would move correctly unless excursion exceeded an undetermined point where they would then react like a snap action PC board mounted diaphragm switch as I'm sure people have seen like below:

index.jpg

The problem again is related to the hand made nature of things... a 2mm drill bit will cut through this spring stock without problems. A 2.5mm drill bit can make it wider, but trying to finish the hole with a fresh 3mm drill will distort the hole. And if I try to drill the hole without the intermediate drilling, I have the same results. Then add distortions by cutting the final "X" shape with scissors, and some springs work fine while some act like snap action switches!

So I went back to the 3D printer and the Taulman nylon bridge 3D printer material that I abandoned some time ago. This time I made X springs with it using settings I have fine tuned for the NinjaFlex material. Since I gave up on the Nylon Bridge material, I had modified my printer head to deal with the NinjaFlex product. The NinjaFlex turned out to be to too stretchy for this "X" application but the modification I made to the printer (and a much slower print speed) worked out well in making the "X" springs in Nylon Bridge.

Here are some of the hand cut stainless springs and some springs printed at 0.75mm thickness "X" springs in Nylon Bridge.

IMG_4554.JPG

I spent quite a bit of time playing with these options, and I do think the Nylon is going to work out well. It does flex, but does not stretch. Just going from feel, I think adding these "X" springs in Nylon Bridge will move the primary resonance up by several hundred hertz. I'm OK with that since I already know it will not add additional resonances.

IMG_4556.JPG

Just so people know I'm not going AWOL... Our family is moving our 92 year old mother into assisted living this week. I'm a 4 hour round trip drive away, so I may not have time for updates in the near term.

Bryan

[sakuszi]

I think so too

[EpicenterBryan]

A quick update:

Here is a really cool way to cure CA (super glue), super fast and rock hard!

I ran across this idea on YouTube and decided to try it out on my new FB coils / rods.
It involves baking soda. WTF?

IMG_4561.JPG

Anyone who uses CA knows it normally stays liquid when there is excess, like when you are trying to build up a connection. What I have been doing prior to tonight is applying just enough to make a connection first and letting it dry. Then applying another coat and putting cotton strands around the connection for reinforcement and then soaking with more CA. Repeat as needed... That takes time, and half the time my cotton sticks where it shouldn't (like to my fingers).

With this new method, you do the first application to make a connection as before, but then after applying more CA, you sprinkle baking soda into the wet CA. It instantly starts heating and cures into a rock hard substance in a few seconds! Then you can either blow off the excess baking soda, or apply more CA and repeat until you have built up the joint as thick as you want.

Baking soda 1.jpg

Baking soda 2.jpg

The great thing about this is that you can sand or file the hardened stuff as needed! And you can literally do that within less than a minute.
People do similar things with other types of powder filler and CA. There are several videos on YouTube. One guy sands bone to make dust and uses the same idea to fill nut slots in guitar head stocks to be able to re-cut them.

For some reason this CA and baking soda mixture generates heat and cures instantly. I have no idea what is going on from a chemistry standpoint, but now there is also a way to keep CA from running down from where it's applied. Just sprinkle some baking soda on it and it stops and turns to stone.

It's very interesting and I'm sure you guys will find a use for this idea. I'm planning to use it for bonding the push rods to the torque tube.

How cool is this?

Bryan

[Snug Music]

A quick update:

Here is a really cool way to cure CA (super glue), super fast and rock hard!

Hey Bryan,..
That's really cool! Baking soda ... I'll steal my wife sometimes baking powder, hopefully it does not come into the kitchen, otherwise I get bump with the rolling pin! heheheee .. lol

Best regards..

Scotty

[emidisc]

Hi Brian
I have been using a product called "Supa Fix" for the last few months and it appears very similar to your baking soda method,
and as you say makes a massive difference to the strength of a joint, I've also used it to make my own drive belts from o' ring section.
Would it work with fine metal filings? May give it a try.

Emidisc

[EpicenterBryan]

I have been using a product called "Supa Fix" for the last few months and it appears very similar to your baking soda method,

Wow, that looks like colored baking soda. Perhaps the metal powder is already in there though.
It's interesting that at 1:27 in the video on their front page that you can see some smoke from the heat I mentioned when using baking soda:

http://www.supa-fix.com/

Let us know how adding metal powder works. Also, since you already have the powder, can you test to see if it's conductive or magnetic?
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BTW, I'll be doing a post tomorrow on some things I learned this week - much of which was posted in the thread on "VTA confusion" here, but my take on the info relates to Groove Scribe and some possible issues: http://lathetrolls.com/viewtopic.php?f=1&t=6369&hilit=vta.

I've been looking at some of the patents either mentioned directly, or mention on other pages mentioned in the same thread. What a great resource that thread is! It's helped me think about some performance issues I haven't even looked at yet like harmonic distortion. But also possible decreased channel separation at high frequency (as MarkRob mentioned), although I'm sure the bulk of low channel separation will be cured with the X springs. But now is the time to address everything I can!

My head details like stylus and torque tube length, and also distance to piano wire mount need to be addressed. Spring back of the recording media was not accounted for in my head details and should be addressed with a new understanding of it's impact! Perhaps this should be done in your head too? Some of what I've learned explains why the stylus angle on the Souri head is so large.

So stay tuned. I'll be posting some diagrams with dimension details on what I have now, and what can change to fix the issue in theory and what can change within practical limits with what I already have built. I'll also post some old patent images that will help illustrate what's going on.

Just so you remember, this is what the last torque tube / v-spring assembly (and stylus) looks like from the last Groove Scribe test. To give you an idea of scale, the rod is 3mm in diameter. The stylus is 1.6mm in diameter.

IMG_4570[1].JPG

Bryan

[Snug Music]

My head details like stylus and torque tube length, and also distance to piano wire mount need to be addressed. Spring back of the recording media was not accounted for in my head details and should be addressed with a new understanding of it's impact! Perhaps this should be done in your head too? Some of what I've learned explains why the stylus angle on the Souri head is so large.

Bryan

hey my friend,...

Bryan, what u think about this one!>> https://books.google.de/books?id=riMJ5Uo8fZgC&pg=PA393&lpg=PA393&dq=dmm+cutting+stylus+angle&source=bl&ots=Y6_hH0mcA0&sig=JlcfOxRuI2tWowx5mW1H1gXXNjs&hl=de&sa=X&ved=0ahUKEwiXmfm5l8_LAhUKJ5oKHTaNBbEQ6AEILjAB#v=onepage&q=dmm%20cutting%20stylus%20angle&f=false

[EpicenterBryan]

Bryan, what u think about this one

Scotty, I have seen that. It is not the same problem or solution to what we are working with. DMM cutting is direct in soft metal, and the metal does not spring back, and the process is more like making metal parts in a machine shop with different material issues.

[Snug Music]

Bryan, what u think about this one

Scotty, I have seen that. It is not the same problem or solution to what we are working with. DMM cutting is direct in soft metal, and the metal does not spring back......

yes I understand! then will probably just what you said. rethink and go completely new approach to the thing. am tomorrow in the University, let's see what my former professors say. they also have very good helped me souri-cutter head.


Best regards

Scotty

[EpicenterBryan]

Hey guys,
I thought I would go over a few things.
Since I have to make a new Torque tube, I decided to look into the whole Vertical Modulation Angle (VMA) and Vertical Tracking Angle (VTA) discussion from the other thread. It's apparent I need to change some things!

First off, here is a diagram from the Benjamin B. Bauer patent US3490771 on the subject. The quick version is that the VMA when cutting has to match the VTA on playback or second harmonic distortion results. But also, it turns out that there is spring back from the material being cut which also needs to be accounted for and amounts to about 20 degrees.

The Benjamin B. Bauer patent "Sound recording method and apparatus" which has all the details about springback and the fix can be found here:
http://www.google.com/patents/US3490771

Cut and Playback.jpg

There is also an excellent article written by Benjamin B. Bauer in Audio magazine, Feb 1963 on pages 19,20,46,68,69. This one is a must read. This discusses how the original Westrex head which was designed to have a VMA of 23 degrees actually ended up having an effective VMA of 2.5 degrees because of the unknown at the time effect of 20 degrees of spring back.
http://www.americanradiohistory.com/Archive-Audio/60s/Audio-1963-02.pdf

So I decided to draw up my existing torque tube and see what the angle was. As you can see, the angle to the piano wire connection at the rear of the head is only 18.4 degrees. Without accounting for the 20 degrees of spring back, it actually has an effective VMA of -1.6 degrees!

Torque tube 18.4 degrees.jpg

There are several ways to fix this. I'll go over the options. The first one is to set the stylus lower in the hole. That would change the length and thus increase the angle. I've ruled that out. Increasing the length adds unsupported aluminum from the shank and I don't want that to flex.

The second one I'm also ruling out. The easy fix (well, not so easy really) is to move the stylus toward the back - behind the link connections which effectively shortens the torque tube. That would be like the Neumann, Caruso and Todds Bladerunner (and others). The reason I'm ruling that out is because of the difficultly level in making the tapered hole for the stylus (and the special tool needed). Also because of the need for a stylus tool and the unknowns of getting the stylus aligned. I like the presto style stylus since it has a flat surface in the front where a set screw pretty much guarantees proper alignment when the screw is tightened. But that means it has to be in the front so a set screw can be used.

The next option is to shorten the piano wire connection as much as possible, and then the total length of the torque tube. Below is an example that results in 38 degrees - leaving an effective VMA of 18 degrees. As I have read it should be 20 degrees +/- 5 degrees. 18 degrees is what the effective VMA of the Neumann is - correct me if I'm wrong.

Torque tube 38 degrees.jpg

But as you can see in this mockup, there is just not room in there to do it what with those X springs and magnets. Behind the V spring would be a new connection block for the V spring and piano wire.

IMG_4574.JPG

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[EpicenterBryan]

CONTINUED FROM PREVIOUS POST

The next option is the way I'm going.
First, the torque tube and piano wire will be shorter. Then as mentioned in the Benjamin B. Bauer patent and Audio magazine article, I'll add an angled shim between my lathe and my head. And will angle the stylus in my torque tube.

Here is an example that now has a 20 angle between the cutting tip and the piano wire connection. And below that, what it looks like when the head is then angled as well.

Torque tube 20 degree with correction.jpg

Torque tube 20 degree with head tilt.jpg

And here is a graphic from the B. B. Bauer patent that shows the stylus and head angle combination well:

head angle shim.jpg

The actual angle used really depends on what size torque tube I can fit in the head. So I'll be prototyping up something this week. Once that's done I can calculate what angle I'll need for the stylus and head shim. The new V-spring and piano wire mount block will probably be prototyped on the 3D printer, but then I'll make one on my mill. The torque tube prototype will probably be made in aluminum with this gizmo attached to my mill.

IMG_4575.JPG

I already had the rotary stage and used that on my last stylus holder, but I just got this incline table yesterday so I could try drilling the angled stylus hole. Depending on how my prototype comes out I might use it, or send it to John to duplicate in better precision.

Oh, I also wanted to list some other pages I found that had really useful info on all this.

A great resource on the subject of VTA. Also lists VTA of varieous cartridges in different time periods:
http://www7a.biglobe.ne.jp/~yosh/vta.htm

Another great list of references with synopsis of each:
http://www.audioasylum.com/cgi/t.mpl?f=vinyl&m=12364

A good overview of VTA and SRA (stylus rake angle).
http://www.audioasylum.com/audio/vinyl/messages/1240.html

Bryan

[Snug Music]

The Benjamin B. Bauer patent "Sound recording method and apparatus" which has all the details about springback and the fix can be found here:
http://www.google.com/patents/US3490771

Wow,..
Bryan, the PDF is awesome !!! Especially since I love old equipment. I became very warm feeling while reading. Memories of the time when I was little and my first portable record player with speaker (mono) got. hehee .., the turntable I still have! smile ...
If times each read ... its worth it !!!

[EpicenterBryan]

Bryan, the PDF is awesome !!!

Glad you liked.
Mark turned me on to that yesterday. It really explains what is going on with that angle and the history behind the discovery.

Bryan

[sakuszi]

great ! I do not understand. Where is the VTA? it seems to me that everything is anyhow, gramophone needle hits the groove side, anyhow, crooked groove mono, stereo above or below the left and right side of the groove, so I understand. The angle of inclination must be due to a knife undercut lacquer plates, as well as soil and plow crashes sideways
If the needle is blunt it does not read the small incisions, high frequency ?

[EpicenterBryan]

I do not understand. Where is the VTA? it seems to me that everything is anyhow, gramophone needle hits the groove side, anyhow, crooked groove mono, stereo above or below the left and right side of the groove, so I understand.

Let me clarify. When the stereo information (L-R) is cut, the stylus moves up and down in an arc (vertical motion). The arc is defined by the VMA (vertical modulation angle) which is the effective angle formed from the cutting point to the end of the cantilever (the connection between the piano wire and head body). When it is played back, the playback cartridge also has a cantilever and forms an angle. On playback, it's called VTA or vertical tracking angle. The two angles must match for lowest distortion and correct stereo image. However, there is also bounce back from the material being cut that also needs to be accounted for in the cutting cantilever when the groove is actually cut. That bounce back accounts for an additional 20 degrees.

Here is a diagram showing the arc that the stylus moves through during vertical modulation on a Westrex ...

westrex torque tube.gif

Bryan

[emidisc]

With reference to the "SupaFix" I just did a quick continuity test and although I could not pass current through the cured adhesive it is attracted to a magnetic source, I also attempted to file the cured surface and could not do any significant damage to it! hence the company video showing a grinder! What is interesting is that after my filing attempt the material then appears metallic!
Having checked the filler powder material spec it contains calcium oxide.
NOTE! There is a number of warnings regarding the toxic contents! So please handle with care
Emidisc