V1.0 of Bryan's 3D printed head with feedback

[Stevie342000]

Hello Bryan an epic tale indeed, looks interesting.

I was just thinking and I know you may not agree with this but it might save you some money.

Whilst you are prototyping your cutting head and suspension why do you not use some of the steel needles that Jerry sells they are designed for those who are essentially beginners so they get a feel for cutting with out some of the inherent costs such as broken styli?

They may need some trimming and I am not sure what cutting stylus type you are using but am assuming it is a Neumann or Presto?

There may be interactions with the magnets though and with frequency response but it may get you in the right ball park area.

Just a thought!!!!!

[EpicenterBryan]

I was just thinking and I know you may not agree with this but it might save you some money.

Thanks for the note Steve. Your note has merits and I'll try them out for other experimentation I plan to do like those "playing the bones" X-Ray discs. The costs I'm running right now is high, but no worse than what I went through in the early CD adoption phase when "buffer under-runs" caused many coasters to be generated at $15 each. OUCH!

Bryan

[EpicenterBryan]

OK, It's been too long since the last update.
Many changes are coming into focus. Tonight I'll discuss the driver discs. Tomorrow I'll hit on the stylus holder. The next day I'll discuss the push rods. By then the weekend will be here and I'll get it all together for another go!

So the big issue as MarkRob has always stated - is to get the moving mass down. That's my focus these days.

Tonight's discussion is on the driver discs. Now, the discs I'm talking about are the ones that allow connection to the drivers I'm currently messing with. Refer to earlier posts for part numbers and such. There have been many versions of these I have fussed with, but I may have only shared 2 versions. Tonight I will share the 3rd and final version.

Here is some data on the first 2 versions, and new info on what I'm going with now:
Drive discs (Each):
Plastic V1: 1.11g
Plastic V2: 0.56g (last version)
Blank AL disc 0.97 mm thick: 0.76g
Drilled AL disc:0.45g

To make the final and lowest weight version of the driver discs took some doing. Ultimately I decided to go with 3/4" aluminum discs that were 0.97 mm thick. I decided to drill and tap them for 3mm on center, and drill extra holes to reduce the mass. To do that I printed several versions of jigs to hold the discs and provide drill guides. It took 4 or 5 versions. Eventually, I came up with a 2 part guide that would clamp together to hold the discs under tension so they didn't move in the drilling operation.

IMG_3025.JPG

I had a total of 10 blank discs, and I trashed many and broke several bits until I got the final version of the jig right by clamping the two plates together, and only drilling 2 discs at a time. Early on I used American pennies as spacers but discovered only ones from the early 1970's were actually soft copper, and newer ones were nearly 95% zinc. I decided to change the jig so I only needed 2 blanks with no spacers.

Shown on the left are a pair of discs that turned out to be off center because I didn't have the tolerances close enough between the upper and lower jigs and when I bolted them together I didn't realize they were offset.

I also increased the drill size a little (since I broke a metric bit) and it also reduced a bit of weight... So the bottom two are out of control perfect! And I have exactly 2 blanks left. Damn.

IMG_3029.JPG

Thant's it for tonight.
Check in tomorrow for the next batch of updates.

Bryan

[EpicenterBryan]

Forgot to add this photo of what the driver disc looks like on the driver....

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[ROLANDJAYS]

nice drill fixture

[opcode66]

I really wanted to make as many of these parts on my 3D printer as possible. I don't think a usable 3d printed head is feasible unless a LOW-FI result is the intended result.

That has not been my experience. I am closing in on a really good head. Entirely 3d printed. The only metal are the screws, the coils, and the dsub pins I'm using.

Check the video on my thread for the latest cut. I'm getting near full range.

[Bahndahn]

Great work Bryan!

Carbon fiber seems seldom addressed in this blog. It is easy to form, modify weight of [add more resin to match weight], has very high heat handling, and is very rigid.

You can buy little kits.

http://www.carbonmods.co.uk/departments/carbon-fiber-kits.aspx

Im going to make some transducers with transfer-to-stylus rods from it soon. It seems quite optimal.

[EpicenterBryan]

Carbon fiber seems seldom addressed in this blog. It is easy to form, modify weight of [add more resin to match weight], has very high heat handling, and is very rigid.

Bennett, you are right. I discovered tonight I could get rods and hollow tubes at the local toy and hobby shop (in some sizes, not metric). I don't know why I keep doing things in metric since I keep having to order stuff from far away... I guess I made the mental change to metric a few years ago since I do things in Sketch-up and my 3D printer is set up for metric.

Bryan

[EpicenterBryan]

Lot's of stuff to go over. I'll have to do this over several posts.

I've had to hold off with my great mechanical updates and lessons learned, because I discovered my playback cartridge (an M95ED from the late 70's) is toast, and all previously obtained data is total crap. Wow! Let's dive into that first.

Last week I received some CBS Laboratory Test Records I bought on E-bay. The two I purchased were the STR 100 and the BTR 150 discs.

IMG_3063.JPG

So after checking the phono preamp (not 1 but 2 different preamps) using an inverse riaa board that takes line level inputs and strips the riaa curves off and attenuates back to phono levels, and finding that the preamps and the rest of the digital in and out to the PC were correct, I used both LP's and the data showed that my cartridge is toast. The funny (and embarrassing) thing is that the last time I actually listened to records using that cartridge was about a 5 years ago when I transferred some discs to the digital domain. So, when I saw the response I brought a David Bowie LP (Let's Dance from 1983) down to the warehouse and put in on. All the sudden I went... "WTF, where are the highs". But it was worse than the lacking highs - it was messed up like on an AM radio station in your grandparents car.

One of the CBS tests disc had a right and left sweep, the other had spot frequencies with announcement but they both resulted in the same response - my playback cartridge is toast and all previous data is useless. I have a new cartridge - an M97eX on order which has had mostly positive reviews and I'll do a "do over".

Since the STR 100 disc has no riaa curve applied as it was recorded, they note modulation below 500hz is at constant amplitude and above is at constant velocity. They also provide Table II which shows the ideal response.

IMG_3065.JPG

So what I did was to take the response and apply the inverse riaa curve to compensate for what the preamp was doing, then I applied an inverted curve from the data specified in Table II and the result is shown below for the response of this trashed M95ED cart.

M95ED after eq.jpg

Notice there are some crazy low frequency signals. I can tell you that the disc is really warped, and those low frequency issues are really there. But you also notice frequency response dropping off at a constant rate, and 20khz is at-least 12 dB down. That is were where some of the highs went in some of this testing.

Now, one final piece of info. Right before I started all these tests I checked the stylus on the M95ED with a microscope and saw no wear but it had a bit of debris on it and I had a NOS spare so I replaced it. After all these issues, I ran the same tests with the old stylus thinking something may be messed up with the cantilever or something and there was no difference. So, did this cartridge develop an issue when the stylus was removed and replaced, of did something actually age and deteriorate overs the years since the last time I actually used it?

The next part of this update relates to some of the really nasty turntable noise and rumble in the early head response.

After a long phone conversation with KrisD from Seattle ( a fellow 8D owner) and his inputs, most of the rumble issues have been resolved - it turned out to be hardened motor mounts and bent motor mount bolts. Thanks Kris!

So I found some thick and squishy rubber remnants from a local rubber supplier - and cut new isolator bushings for the motor drive mounts.

IMG_3068.JPG

As it turned out, I could not acquire replacement bolts of the correct length, so I just used the fact that they were bent to adjust them so the mating surface between the motor shaft and drive puck were aligned vertically. It all worked fine, and the noise is gone.


Stay tuned over the next week for updates!

Bryan

[Kris D]

Hi Bryan, Nice job making new isolation grommets! Try McMaster Carr for the bolts- they have everything!! I would send your idler pucks to Terry at Terry's Rubber Rollers, they are the same spec as Presto 6N and 8N. That should help with your remaining rumble issues.

Best - Kris

[rsimms3]

Bryan - For your replacement grommets, do you have any information on the material you cut from? I haven't been able to find anything quite close enough to the original material to put on my 6D project. Most everything I've found has been too soft or too hard and ordering a bunch of different materials isn't really feasible or cost effective.

As for bent bolts, I have used bolts from the hardware store that were the same head/size and cut them down to length with a Dremmel in a previous project.

[ROLANDJAYS]

For those interested in working with carbon fiber .....
Wear a dust mask when cutting, and If you can get diamond coated tools, they work the best

[EpicenterBryan]

For your replacement grommets, do you have any information on the material you cut from?

I don't. It was left over from another project and came from the scrap bin at the rubber place. For the other project I bought several types by the pound. That piece looks like it was a section of an industrial anti fatigue mat. It has grooves on one side. I have lots left if you want me to mail you a chunk. PM me with your address and about how much you could use. What I have is 6" x 33".

[EpicenterBryan]

My new phono cartridge arrived and I ran frequency sweeps and did some listening to some old favorites. WOW! That’s more like it. Now I’m confident in my playback and ready to do some test cuts.

I’ve messed with a bunch of things in this down time, and here are some updates.
We already discussed the drive discs. So how did things go with the Stylus holder, and various push rods?

Stylus holder:
V1 Plastic / Nylon: 1.31g
Aluminum machined V1: 2.00g
Aluminum V2 (made from V1): 0.54g

You saw the first plastic version with the threaded nylon insert, and the first big block version of the aluminum Stylus holder. The V2 version is a much reduced one made from the big block V1 holder. Some of the extra material was removed on the mill, some with various dremmel tools, and the rest with hand files. These mods took several nights of fussing with but the weight came down from 2.00g to 0.54g! In this shot I used solid threaded aluminum rods - 21.6mm long made from an anodized cap screw with the head cut off.

IMG_3045.JPG

The goal on this version was to reduce the moving mass as mush as I could. I still threaded the discs and connection point to the stylus holder but I decided to change the way I assembled everything. In previous versions, I poked holes through the driver cones and glued the driver discs in place using alignment tools inserted on the back side of the drivers. Using threaded rods and nuts, I would tighten everything up and set it aside for the glue to harden (epoxy).


After removing the alignment tools I would install rods or screws from the back side of the driver into the stylus holder in final assembly. The reason I didn't want to use that method this time, is it left extra push rod material inside the driver since I could only cut the push rod down so far from the outside of the driver. That left extra mass associated with the pushrod going through the center of the driver, or would leave a head if I used a screw.

IMG_2904.JPG

I played with the idea of using 3mm aluminum tubing for the push rods, but since the discs I made were threaded as well as the Stylus holder, I went that way first. And this time, I decided to adjust everything very carefully outside of the head, making sure each side had the same number of threads and doing several test fits before gluing both discs in place. This time I used super glue, and also put super glue at each threaded connection.

Bad idea.

It turned out that when everything was glued into place, including push rod connections to the stylus holder; the discs were not perfectly centered or perhaps angularly misaligned. So with little upward pressure (downward cutting force) the geometry was messed up and the driver voice coils would rub. I tried putting shims under the drivers in various spots but the geometry was just too screwed up

I disassembled everything and destroyed the push rod threads in the process, but was able to salvage the discs and the stylus holder (after chasing the threads with a tap). While looking at the drivers I discovered that there was left over glue on the cones which made a shelf or lip and I could not remove it without trashing the "surround” which is really what keeps the coils centered. The driver discs would never be able to be glued at any other angle or orientation than last time. So in a last ditch attempt, I used some threaded sections I made from 3mm aluminum tubing, and some short sections of guitar strings to add flex to the push rods.

I purchased the aluminum tubing to experiment with the idea of using it for the pushrods and since I had it, I tried to thread some and was successful (kind of). I was able to thread about 6 continuous inches of it, and also broke it off in my die 3 times. It was kind of embossed inside, but had actual 3mm threads on the outside. The walls were very thin and it was fragile but functional. Here is what the threaded and non-threaded sections look like:

IMG_3058.JPG

I used 2 short segments of the threaded tube (perhaps 8-10mm each), and put a short segment of guitar wire (perhaps 8mm) inside both - centered in-between, and crimped each connection. Who knows if it will hold and it sure looks ugly and misaligned but the driver voice coils don’t rub and it can take quite a bit of force – so I’ll test it just for fun. No, the stylus won’t be sticking out that far. There is left over super glue in the upper hole that I still need to drill out.

IMG_3071.JPG

CONTINUED ON THE NEXT POST.

[opcode66]

To be fair, your thread should be renamed. Your head doesn't currently have feedback...

[EpicenterBryan]

CONTINUED FROM PREVIOUS POST
I mentioned playing around with 3mm tubing for the push rods. The big issue was how to attach it.
I found a product called Alumiweld, and bought some at Harbor Freight. It has a much lower melting temperature than normal Aluminum and can be used kind of like solder or brazing rod. So I gave it a try connecting some 3mm tubing to a trashed driver disc.

IMG_3060.JPG

I also bout a pencil butane torch and tried it with a tube going through a disc.

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It's king of tricky stuff and melts really quick if you hit it with flame. It blobbed more and faster than I expected, but I used a nearby screwdriver to sweep some off while still molten and cleaned up the rest on a grinder. I think it is practical with some practice.

IMG_3042.JPG

As far as the push rods go... here is some measured data for general info:
Aluminum M3 threaded screw – head cut – 21.6mm long: 0.34g
Aluminum tube – 3mm 21.6mm length: 0.23g
Nylon threaded rod – 3mm 21.6mm length: 0.15g
Threaded Aluminum tube – 3mm 21.6mm length: 0.14g
20mm guitar string – 20mm length:0.21g

More on this tomorrow, and then I think I'll need to close this thread and start a new one (good comment Todd). Things have changed so much. It's kind of the way thing go when experimenting. Some times the twists and turns are more interesting than the original path.

Bennett (Bahndahn) turned me on to some drivers that I think will work even better, and I already have a mounting head printed, and tooling for making some of the parts. I'll be using carbon fiber for the push rods, torque tube and stylus holder.

What a journey.

[opcode66]

Indeed! I'm already on parts for 1.B of mine...

[emidisc]

Bryan you appear to be following a similar path to my own experiments ie. Alignment of coils within the driver etc the low temp aluminium weld looks interesting my torque tube is made from brass so that I can solder items to it,
The drivers you found are very tough (I am now using the same) if you look inside from the back you can see the coil formers are aluminium as apposed to the normal paper/card type
I will try to upload some pictures of my effort - like yourself I have been trying to keep the moving mass as low as possible
I am starting to realise how difficult it is to maintain the required geometry during the build
Emidisc

[emidisc]

Photos as mentioned on my previous post......

[EpicenterBryan]

like yourself I have been trying to keep the moving mass as low as possible
I am starting to realise how difficult it is to maintain the required geometry during the build

Hey emidisc, great progress there. It's so fun to see other peoples versions. Looking forward to seeing your results.
Are you using piano wire for the torque tube? I discovered yesterday that the hobby shop also has that in many sizes.
Did you have a chance to weigh any of the components before you assembled things?

If you end up wanting to try the aluminum discs or the 3mm tubes, I got it on Ebay as well as the blank discs (3/4"). The tube is made by K&S metals and you can get it through their web site also. My hobby shop carries that brand but didn't have the aluminum tube.

Bryan