BD's Mechanical Disk Recorder Build

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opcode66
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Re: BD's Mechanical Disk Recorder Build

Post: # 33586Unread post opcode66
Tue Feb 10, 2015 5:19 am

Light and rigid is best. You don't want them to be bendable. That will ruin your vertical motion from out of phase audio. Could even be hollow and made from syringe needles. Or sewing needles. Though non-ferromagnetic metal would be appropriate.
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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33595Unread post Bahndahn
Tue Feb 10, 2015 10:26 am

opcode66 wrote:Light and rigid is best. You don't want them to be bendable. That will ruin your vertical motion from out of phase audio. Could even be hollow and made from syringe needles. Or sewing needles. Though non-ferromagnetic metal would be appropriate.
Thank you!

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opcode66
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Re: BD's Mechanical Disk Recorder Build

Post: # 33600Unread post opcode66
Tue Feb 10, 2015 5:34 pm

Absolutely! Keep at it! Loving you work here.
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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33612Unread post Bahndahn
Wed Feb 11, 2015 12:37 am

Here is another photo update, a rough setup just to check all the parts fitting. All is well! Some temporary fixes are in place: on the vertical traveller, some foam with adhesive is fixed there to fill a gap I have left for suspension decoupling - I have NinjaFlex thermoplastic elastomer filament that I will use to print little rubber wheels for the bearings that ride the vertical rails, I am currently waiting in some PTFE tubing to fix up my printer for flexible filament printing.

I got some sewing needles and am impressed by how rigid they are. Very suitable transducer-stylus coupling rods indeed!

Next I will begin attempts at cutterhead details and motor stuff for my turntable I will be using. For now, I will use a Harmon Kardon T40 as the turntable assembly. It seems like I good choice because of its platter edge width that is suitable for adding a belt around the diameter. I will attempt to power this assembly with a fan motor [AC]
I salvaged from a very standard 3-speed home fan. I plan on getting the right speed by calculating the right diameter necessary for the drive shaft and 3D printing said diameter drive.

The vertical adjustment system on my lathe design is purposed to accommodate various turntable heights, I imagine I will switch it up someday and I would certainly like to build a solid 14 inch platter.
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EpicenterBryan
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Re: BD's Mechanical Disk Recorder Build

Post: # 33773Unread post EpicenterBryan
Tue Feb 17, 2015 11:17 pm

Bahndahn wrote:Would aluminium work? Why do many designs feature steel pushrods over aluminium? Has anyone used nylon with any degree of success? Other suggestions?
When I build the next Groove Scribe, I'm going with Beryllium copper AKA Spring Copper. It's non magnetic. Hard to find but I think I found some. It can also be soldered. I messed with aluminum tubing. What I bought was non annealed, and as such did not spring back. You need something with spring that will go back into prior orientation. You will never see what is actually going on, but trust me. I also messed with Carbon fiber. That also has serious possibilities and I think you should look into that. Although I glued the carbon fiber rods into nylon screws for the same drivers you are using and had to tear things down, I did notice de-lamination of the fibers right at that connection. I can't say it was for sure that repeated flex at that point or my brute force attempt to disassemble things caused it. After all, it was all glued and I never intended to break thing loose.

Press on Bennett. Go non-magnetic for sure. You can find Stainless that is non magnetic. But I would skip aluminum unless it is annealed. My put is that Beryllium copper is probably the best solution - but try Carbon fiber. Carbon fiber is easy to find, inexpensive, non-magnetic and super light weight. I just can't tell you for sure about the de-lamination issue I saw, and I have less time to play with things than you do.

Bryan

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33783Unread post Bahndahn
Wed Feb 18, 2015 7:49 pm

EpicenterBryan wrote:
When I build the next Groove Scribe, I'm going with Beryllium copper AKA Spring Copper. It's non magnetic. Hard to find but I think I found some. It can also be soldered. I messed with aluminum tubing. What I bought was non annealed, and as such did not spring back. You need something with spring that will go back into prior orientation. You will never see what is actually going on, but trust me. I also messed with Carbon fiber. That also has serious possibilities and I think you should look into that. Although I glued the carbon fiber rods into nylon screws for the same drivers you are using and had to tear things down, I did notice de-lamination of the fibers right at that connection. I can't say it was for sure that repeated flex at that point or my brute force attempt to disassemble things caused it. After all, it was all glued and I never intended to break thing loose.

Press on Bennett. Go non-magnetic for sure. You can find Stainless that is non magnetic. But I would skip aluminum unless it is annealed. My put is that Beryllium copper is probably the best solution - but try Carbon fiber. Carbon fiber is easy to find, inexpensive, non-magnetic and super light weight. I just can't tell you for sure about the de-lamination issue I saw, and I have less time to play with things than you do.

Bryan
Thanks Bryan!

I sourced and obtained some carbon fiber tub today following your suggestion. I had gone about a steel design with sewing needles but hadn't finished it up yet, I figure its better to make the changes while they are easier to make.

The tube I got is .210" OD with a wall thickness of .045". It seemed like a good idea while at the hobby store because it looked useable for both the pushrods and the torque-tube. At the lengths I will be implementing it at, it will be dominantly inflexible; some thought about this and memory of a post of yours [Bryan's] has me wondering of a little flex is needed - if so, I will have to get that flex somehow at the joint between the pushrods and the torque-tube [perhaps with a 3D-printed coupler]. Carbon fiber rod of more narrow diameter may also be a remedy.

I have a full week off next week where I will go all out with general 'completion' of my main lathe structure to hopefully yield some first cuts or impressions.

As for other progressions, I had an enjoyable time last night measuring the speed of my fan motor with a strobe light tachometer - I cant confirm how accurate the iOS app I used is, but it certainly was a useful, good experience.

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opcode66
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Re: BD's Mechanical Disk Recorder Build

Post: # 33784Unread post opcode66
Wed Feb 18, 2015 9:13 pm

It really depends on how you are building out your transducers. You want them to be able to teeter a little but not much. For me, the teetering is in my spring system. Therefore, my linkage to my torque tube needs to be inflexible and rigid. If you have too much play here then you will destroy your vertical motion given out of phase audio.

Since your tweeter based system is similar to Bryans, and you don't have a spring system like I do, you may want some flexibility. But, I doubt it. The real test is if you can move your transducer rods side to side a little. Not much. And, with some force on your end. That is good. Too loose is bad.

If you can too easily move them side to side (teetering) then there will be zero resistance when the opposite channel pushes. And, you'll be left with largely lateral motion. You don't get vertical without some resistance from the other transducer.

45/45 systems are very tricky to get right.
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EpicenterBryan
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Re: BD's Mechanical Disk Recorder Build

Post: # 33786Unread post EpicenterBryan
Thu Feb 19, 2015 12:08 am

Bahndahn wrote:At the lengths I will be implementing it at, it will be dominantly inflexible; some thought about this and memory of a post of yours [Bryan's] has me wondering of a little flex is needed - if so, I will have to get that flex somehow at the joint between the pushrods and the torque-tube [perhaps with a 3D-printed coupler]. Carbon fiber rod of more narrow diameter may also be a remedy.
I see where you are going. My initial thought is you would need a short segment of smaller diameter solid carbon fiber (or other material with some flex) at the torque tube connection. But knowing you are using the same drivers I have messed with and not a speaker like my first version with very little centering spring effect, you may be able to get away with it. The big thing is you will force what Todd calls "teetering" to occur right at the driver spring. Having played with these drivers, I know those springs can still keep the coils of the drivers sufficiently centered even with the driving angle changes by quite a bit (as opposed to the speakers I was messing with on another head design). There is quite a bit of clearance in there on the drivers you are using and they can handle quite a bit of angular misalignment for lack of better terminology.

If you went with a short segment of solid carbon fiber (perhaps a section 1/4 of the total length), you will probably need a short segment of tube that fits inside the one you have (perhaps only 5mm) that can be glued in the end, and then a solid segment to fit inside that "adapter" tube. I know you have a 3D printer. I would recommend sticking with the same material for the union so you don't question yourself related to different materials and such at the interface. Just glue like materials together so you don't drive yourself crazy about causes of unexpected results.

I never tried a non flexible push rod with these drivers.

You are a mechanical engineering student and could probably figure out some things and know for sure. I guess, you should figure the angular error for vertical or lateral modulation when a solid push rod is used. I'm sure you have some gauges and could measure the force needed to deflect the spring face on the driver by the same degree at the distance to the connection on the torque tube. I guess you would also need to measure the force provided to the same point by a driver on the opposite side for a given drive level. If driving that point with one driver can't overcome the force needed on the other driver to "teeter" as Todd calls it, then I guess you need more flex at the torque tube union.

Does that make sense or should I have another cocktail and re-phrase that?

And to Todd, thanks for chiming in as well. Your inputs are also valid.
These drivers are the Surface Wave Transducers that have the 4 point springs on them like used on Groove Scribe - not the full range speakers from my earlier (failed as of today) attempt.

Bryan

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cloop
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Re: BD's Mechanical Disk Recorder Build

Post: # 33788Unread post cloop
Thu Feb 19, 2015 5:03 am

Wow,
That cutter head looks thick! May I ask how you built those nice big drivers? Is there a place where you can buy them? I havent had a lot of luck trying speakers as drivers.

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33797Unread post Bahndahn
Thu Feb 19, 2015 3:24 pm

Thank you Todd and Bryan, fine guidance!

I think I am picking up what you are putting down however it will take a few days for me to process this information; I'm a slow learner and this is all new to me, thanks for taking your time. Mechanical engineering would be helpful in this situation, however I am an electroacoustic engineering student of which is more DSP, psychometrics/psycho-acoustics, sound design, 'music-technology' [contemporary instrument design] etc.

Im certainly going to begin this cutter head build without going all out in calculations and analysis - once the big problems arise, I will know where to dig. For now I'm going to do some empirical experimentation. Maybe applying DC to the drivers or observing them with a high-speed camera will give me the information I need to get an idea.

Is there an optimal teeter 'location'? For example, would it be better to focus the teetering toward the torque tube coupling or the transducer spring? Does it matter/is it known?
cloop wrote:Wow,
That cutter head looks thick! May I ask how you built those nice big drivers? Is there a place where you can buy them? I havent had a lot of luck trying speakers as drivers.
I did not build the drivers, I purchased them at an electronic component store here in Montréal for $25 a piece.

Here is the direct type and source of the ones I purchased [same model that Bryan is using on 'Groovescribe']
http://abra-electronics.com/audible-devices/speakers/spk-trans-l-surface-transducer-large-spk-trans-l.html

Here are some similar drivers, slightly smaller looking.
https://www.sparkfun.com/products/10975

If you want 200 of yet another slightly different model:

http://www.alibaba.com/product-detail/10-25W-Conducting-Transducer-Exciter-50mm_60114766802.html

Yet another:

http://www.ebay.com/itm/Dayton-Audio-BCT-2-45-x-25mm-Bone-Conducting-Transducer-240-612-/221647697253?pt=LH_DefaultDomain_0&hash=item339b3b7565

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33932Unread post Bahndahn
Fri Feb 27, 2015 12:35 am

I'm looking for some opinions on a question I have come to regarding motors.

I've got a number of motors of various sorts, and two places to use them: the platter drive [belt], and the pitch lead-screw [belt, gears, direct, whatever works].

I have the following motors [see photos as well], where do you recommend I use them?

I. AC Motor from home fan - three speeds [measurement notes: black and white wire = 582[581.75]rpm .263ohm, black and red = 1750rpm?? running hot,, .223ohm, black and blue 1740rpm .286ohm]

This motor is the choice I have been implementing in my plans. I am not fixed to the decision, yet it seems like it would be the most powerful. I am probably basing that off of its relative size.
photo 3.JPG


II. Two DC motors, salvaged today from an epson 4400 large printer I found! These motors, as stated in the printer's service manual, are purposed in the printer at 42 volts. The seem beefy.
photo 1.JPG


III. Two small stepper motors, salvaged from the epson 4400 Driven at 24 volts according to the service manual, steps per revolution: currently unknown

IV. One 'Wantal 42BYGHM809' Stepper Motor Purchased new, 0.9 degree per step. I originally purchased this for the platter drive but now I have been moving towards using the fan motor there.
photo 2.JPG
What do y'all think?
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Gus
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Re: BD's Mechanical Disk Recorder Build

Post: # 33949Unread post Gus
Fri Feb 27, 2015 3:59 pm

About stepper motors the round one is good for belt drive turntable but does not have many torque to cut a disc for more infos look here http://www.altmann.haan.de/turntable/

fun motors is a good choice but i think you have problems with RPM stability, give it a try and let us know if it work well :)
better option is a strong motor from reel to reel machine
look here
http://www.ebay.com/itm/Vintage-BODINE-Type-NYC-13-1500-1800-Motor-for-Reel-to-Reel-Tape-Deck-/371266707974?pt=LH_DefaultDomain_0&hash=item5671386206

or a dc servo motor

http://www.ebay.com/itm/Sony-PCM3402-Reel-To-Reel-DC-Servo-Motor-1-/261791577446?pt=LH_DefaultDomain_0&hash=item3cf3fe7566

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dimi751
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Re: BD's Mechanical Disk Recorder Build

Post: # 33981Unread post dimi751
Mon Mar 02, 2015 5:06 pm

Great work ! Which turntable drive you going to use? You build your own drive or you use dj turntables

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33995Unread post Bahndahn
Mon Mar 02, 2015 8:32 pm

Gus wrote:About stepper motors the round one is good for belt drive turntable but does not have many torque to cut a disc for more infos look here http://www.altmann.haan.de/turntable/
Thanks Gus! Great resource.

I have now tested all of my motors to find that the 'Wantai' motor is by far the best for the turntable platter. 68oz/in torque! I am unable to vary the speed by pinching the shaft. It makes some sound, but I have plans to do all I can to silence its transfer through the belt to the turntable, using a very heavy spindle with the motor mounted in a somewhat flexible carriage, all separate from the lathe body will be my first implementations. If that doesn't work, I will make a phase cancellation pulley - belt 'feedback'. Phase cancellation goes pretty far these days https://cycling74.com/2015/02/04/transforming-room-sound-with-a-max-patch/

I looked at some DJ turntables today, but being a $300 option I am far more interested in working out the stepper motor configuration. I ordered the "Big Easy Driver" for my Wantai motor as the "Easy Driver" was a little underpowered. Regardless of these little expenses, The whole build has cost less than $600.

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 33996Unread post Bahndahn
Mon Mar 02, 2015 8:36 pm

Oh shit! I missed a really important feature of the article Gus provided!! Read below, quoted from http://www.altmann.haan.de/turntable/

Motor Control ...

How do we accomplish a steady motor speed and a smooth rotation? Of course we do not control the stepper motor with digital steps, as this would lead to a rather rough ride. We treat the stepper as if it was a synchronous motor (which it is), so we feed it with sinewaves. A bipolar stepper motor has two coils (just like a AC synchronous motor).

We need a sine-wave for coil #1 and a 90 deg offset sine wave for coil #2 (as I said, just like AC-synchronous).

This is often done with a mains transformer plus a capacitor for delaying the sine for coil #2. This is not really accurate and also not adjustable.

We want something better. So what do we do ?

We just generate a 50 Hz (or 60Hz) sine wave on the computer using a music program (like cool edit), plus a second sine wave with 90 deg. delay.

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Sillitoe
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Re: BD's Mechanical Disk Recorder Build

Post: # 33999Unread post Sillitoe
Tue Mar 03, 2015 4:50 am

Nice work Bahndahn, that room sound max control system looks amazing!
Your belt feedback/ phase cancellation idea sounds interesting.

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Re: BD's Mechanical Disk Recorder Build

Post: # 34076Unread post Babooino
Mon Mar 09, 2015 8:02 am

We just generate a 50 Hz (or 60Hz) sine wave on the computer using a music program (like cool edit), plus a second sine wave with 90 deg. delay
.


You mean as in a varispeed? This is what i do here: oscillator->amplifier->12/120v transformer->motor

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Gus
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Re: BD's Mechanical Disk Recorder Build

Post: # 34083Unread post Gus
Mon Mar 09, 2015 7:06 pm

Babooino wrote:
We just generate a 50 Hz (or 60Hz) sine wave on the computer using a music program (like cool edit), plus a second sine wave with 90 deg. delay
.


You mean as in a varispeed? This is what i do here: oscillator->amplifier->12/120v transformer->motor
if you use stepper motor you don't need the transformer 12/120v just turn up the volume until to see the motor spins.

mp3 player->amplifier->stepper motor

i use for my steppers this amp

http://www.ebay.com/itm/New-Audio-Power-Amplifier-DIY-Kit-Components-OCL-18W-x-2-BTL-36W-TDA2030A-/391038778037?pt=LH_DefaultDomain_3&hash=item5b0bba3ab5

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EpicenterBryan
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Re: BD's Mechanical Disk Recorder Build

Post: # 34109Unread post EpicenterBryan
Thu Mar 12, 2015 1:45 am

So Bennett,
I got a kick out of the post about using two out of phase signals going though a power amp to drive a stepper like a servo and all that... fun stuff - but really? Please save yourself the effort and give me a call. I'll explain what you need and you can share the conversation on your post. You should have my day number. PM me if you can't find it.

Bryan

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Bahndahn
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Re: BD's Mechanical Disk Recorder Build

Post: # 34125Unread post Bahndahn
Fri Mar 13, 2015 11:52 pm

EpicenterBryan wrote:So Bennett,
I got a kick out of the post about using two out of phase signals going though a power amp to drive a stepper like a servo and all that... fun stuff - but really? Please save yourself the effort and give me a call. I'll explain what you need and you can share the conversation on your post. You should have my day number. PM me if you can't find it.

Bryan
I followed this offer up and gave Bryan a call today to talk about motor matters. I gained some important insight:

Firstly, the setup regarding the 90º offset sinusoid waves is a little cumbersome setup-wise, this was certainly becoming obvious as I began testing this approach. Its certainly easy to find or build small amplifiers, but playing back or generating the sines - two channels worth, is undoubtably somewhat taxing. I was considering generating them from an arduino but that wasn't progressing very well.

Next, it is important to note that micro stepping is a process instilled by the stepper-motor driver, not the motor. I however did not realize that the extent of micro-stepping resolution - a driver with 1/256 micro-stepping resolution on my Wantai motor [0.7 degrees/step=400 steps per revolution] works out to 102400 steps per revolution?! This is presumably too fine at this point, but simply put: obtaining smooth motor operation without auditory interference via the belt-to-cutting-platter is certainly possible with square wave use.

I'm going to see what kind of resolution I can get out of my "Big Easy Driver" - I literally abandon it without even testing it when this sine wave thing came up.

What about a subtle low-pass filter on the output of the stepper-motor driver if problems occur? Are the square waves that come out of the driver also at a 90º offset?


Thanks again Bryan for your time today!

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