introducing my diy lathe assembly phase

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carlos820
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introducing my diy lathe assembly phase

Post: # 40983Unread post carlos820
Sun Feb 28, 2016 9:49 pm

Hello I'm new here, and totally inspired by the amazing works of other contributors to this forum. I've started down the path of a DIY lathe. I'm going to post a few pics..to document the construction phase, later when initial tests occur I'll start a new thread for that phase, and so on. Im ok at building/machining and confident on electronics building but naive at record lathing and the art and physics involved for a good machine, so I'll have a go and see what happens.
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Adinol
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Re: introducing my diy lathe assembly phase

Post: # 41108Unread post Adinol
Sat Mar 05, 2016 10:35 am

Hi Carlos,

Looks good.

I was wondering if you feel like sharing any technical details about your build.

What I'm interested in are the following specs.

1- What speakers are you using? How many Watts? And is there a link to a "buy" page?

2- The cones... I've been doing some mental planning about how to approach the cone builds. I'm thinking the best approach would be to first calculate the measurements using geometric equations for cones, then building a test cone from paper and next from a more rigid material. A lot of builders I see using aluminum, but I wonder if that's the best materials, as aluminum is tricky to properly clean for proper gluing. What is your experience with building the cones?

3 - What amp are you planning on using? Are you using an op amp? If so which and how many watts? Or do you think it might be better to use a tube amp? If those supposedly produce better sound it might also mean they should drive those cones "better" in some way.

One thing that always puzzled me is the distance from the stylus tip to the pivoting point. I would imagine that distance should be crucial. My thinking is, a greater distance will yield a more pronounced wave form on the cuts, but will require stronger speakers. But too great of a distance is no good because some spikes might "bleed" into the adjacent cuts (I don't know the proper terminology). But that can be solved with the proper use of a compressor, I guess. That's just my thinking before I even started to build a recording head and I think that length is a crucial measurement, but I have not been able to find any information on that.

Anyway, thanks for sharing your project.

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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 41117Unread post carlos820
Sat Mar 05, 2016 11:56 pm

Thanks! Sure so the drivers are 2.5w 6ohm they measure 2" diameter they came from a Dell speakers set, I don't know of a link to find them online they are just something I already had on hand.
The cones I first made with paper to get an idea for the proper shape and size. I used some thin aluminum I also had on hand to make the cones. They are brazed on edges with aluminum brazing rod. I used map gas and it took several tries to not melt the material as it was so thin. Vigorous Stainless steel brushing of the aluminum helped a lot, the aluminum brazing stick would then flow readily into the edges. A dremel tool with a 120 grit flapwheel sandpaper cleaned up the braze bead.
For the amp, I only have a small 20w amp to start testing with. I have a 16 band stereo equalizer with cut/boost range of 24db. So my plan for signal flow is to play tracks from DAW with inverse RIAA and possible compression and any other filtering needed through an Maudio interface, to the outboard EQ, and to the amp. As for the cutting distance/pressure, I'm hoping having a heavy enough cutting head with an adjustable counterweight on the gantry/arm will give me enough balance and adjustment to work..I have considered a spring or damper..but am also thinking I may be able to adaptively adjust this with a servo that adjusts the height of the cutting head. The groove pitch will be adaptive and controlled via software/arduino. Not sure if I will pre-analyse the tracks and map the groove pitch in a lookup table of sorts to use during cutting or will delay the audio and adjust the groove pitch during the cutting like I've seen others do with their projects. I hope that answers your questions, I honestly don't know what results I will achieve, but I'm having a lot of fun building this project.

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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 41118Unread post carlos820
Sat Mar 05, 2016 11:59 pm

On reading your reply again, I may have misunderstood your question about stylus tip to pivot point, are you referring to the point from which the cones make contact with the surface they affect pressure on to the stylus tip?

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Adinol
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Re: introducing my diy lathe assembly phase

Post: # 41156Unread post Adinol
Mon Mar 07, 2016 9:04 pm

carlos820 wrote:On reading your reply again, I may have misunderstood your question about stylus tip to pivot point, are you referring to the point from which the cones make contact with the surface they affect pressure on to the stylus tip?
Sometimes it's difficult to ask a question, properly, when one doesn't know the proper industry terminology.

I looked at images I found on the internet and I noticed that in many instances the stylus is quite long. Let's look at this image.

Image

I approach many things that I build, intuitively. When I look at this picture to me it feels that the stylus is too long, i.e. that the cutting tip is too far away from the pivoting point. It feels that with these proportions the drivers have much less control over the cutting tip (that has to work against a lot of friction and resistance) than if the stylus was significantly shorter. Also, a long stylus will end up doing a more pronounced left and right motion. Again, intuitively I feel that some of the peaks might shoot all the way over to the adjacent grooves, so the playback stylus might skip. An that the part that I thought might be solved with a proper setting on the compressor.

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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 41237Unread post carlos820
Thu Mar 10, 2016 8:38 pm

I follow what you are describing, and at this point I do not have any good answers for that, I thought along the lines of if there is a leverage increase because of some added distance between the stylus tip and the point at which the drivers contact the stylus mount, then that may in effect reduce the amount of necessary drive from the cones as force asserted there would/could be amplified at the stylus tip. However as you say, it may end up being a cause of some groove distortions. I'm not yet at a point of testing. If I have more.time this weekend, I am working on fabricating the stepper motor mount, end caps to the gantry/carrier with the flange mounted bearings. I will try to take pics if I make any progress.

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markrob
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Re: introducing my diy lathe assembly phase

Post: # 41240Unread post markrob
Thu Mar 10, 2016 9:11 pm

Hi,

The head looks really nicely made. I'll be interested to see how that works out for you.

I would shorten the shank. There is no extra output with this type of head when using a longer shank. On heads like the Presto, where the stylus rotates about a pivot, a longer shank does result in higher output. If you think about the arc length at different radii given the same amount of rotation, you can see the effect. However, this extra output comes at a price. Using a longer shank, makes the stylus less stiff. The result is reduced high frequency response. It can also introduce a secondary resonance that would be hard to deal with. This is true in the case of your head as well. Look at the stylus used in the pro heads and you'll see the shanks are very short indeed. Since there is no output advantage in this case, its even more clear that a reduced shank length would be a good thing. If this is a standard Presto style stylus as can be purchased from Transco, you can shorten the shank with a pair of nippers.

Hope that helps.

Mark

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Adinol
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Re: introducing my diy lathe assembly phase

Post: # 41248Unread post Adinol
Fri Mar 11, 2016 9:32 am

carlos820 wrote:...I thought along the lines of if there is a leverage increase because of some added distance between the stylus tip and the point at which the drivers contact the stylus mount, then that may in effect reduce the amount of necessary drive from the cones as force asserted there would/could be amplified at the stylus tip...
I see it as a leverage decrease. Or perhaps we are using different terminology. In my mind, the shorter the distance after a pivoting point, the more leverage you have, so you need less force before the pivoting point. I do agree that the longer stylus will "amplify" the wave forms, but I also believe the a longer stylus will require a stronger driver. Not a driver that will produce more amplitude, but simply a stronger one, because there is less leverage and less control.

There's another thing that I've been wondering about.

Some speakers need to be mounted in proper enclosures in order to work right (Thiele/Small Parameters). I believe that's even more so the case with most of the speakers that have very small cones. So, I wonder if there would be enclosures behind the speakers, if speakers are used for drivers.

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markrob
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Re: introducing my diy lathe assembly phase

Post: # 41256Unread post markrob
Fri Mar 11, 2016 5:22 pm

Hi,

The acoustical performance of any driver you intend to use has no bearing on its performance in this application. You are not moving air. The published frequency response and most of the T/S parameters are not useful. You do care about the BL product which tells you how much force the drivers produce when fed a given current (newtons per amp). You also care about the suspension compliance (Cms) along with the moving mass (Mms) as this sets the system resonance. Rms is also potentially useful as this indicates the amount of loss and factors into the damping at resonance. However, even these parameters are modified greatly once you couple them to the stylus holder.

There is no lever going on with this driver arrangement. So no mechanical advantage takes place with a longer stylus. If you compare the excursion of the stylus point for a given movement of the voice coil with a long and short shank, you will not see any larger excursion. If you do, then there is a mechanical advantage/disadvantage taking place. In the case of the Presto style head, the stylus actually rotates over a small arc. In this case there is a change in arc length as you change the distance of the tip of the stylus.

Mark

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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 41280Unread post carlos820
Sat Mar 12, 2016 10:37 pm

Thanks for the information on the stylus length. Once I get the complete assembly together and make initial tests I'm sure I will be fixing and tweaking the head ☺ right now the stylus/cone connection seems very rigid..so this may not work at all.id like to get away from using any hot glue at all on the next version. For grins I ran some signal thru the head and simply held the it over a piece of aluminum allowing the stylus to just barely touch the surface...and well there was a lot of sound coming off that plate...also looking at the stylus under a microscope its vibrating for sure. I attach another view of the head.
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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 41281Unread post carlos820
Sat Mar 12, 2016 10:59 pm

Here are some.pics of today's progress...
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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 45573Unread post carlos820
Fri Jan 13, 2017 8:43 pm

So its been quite some time since I posted an update. Life gets in the way of the cool stuff sometimes, but I'm back at it, made a little progess, but still need a way to go to be abke to cut any sound. I'd like to post a few pics and ask a few questions of the group.
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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 45574Unread post carlos820
Fri Jan 13, 2017 8:45 pm

Here is another pic..
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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 45575Unread post carlos820
Fri Jan 13, 2017 8:57 pm

Some questions for the group; my current mount for the cutter head allows for a tilt, I haven't figured out how to make it vertically adjustable, as right now it is fixed. One thought is to make the entire gantry vertically adjustable and have some damping, or maybe its better to rework the mount point of the cutter head to allow a vertical adjust and then add some dashpot as I have seen on other diy lathes. My question is do all lathes have to have a dashpot for vertical damping, what if there is no vertical play/motion in your overhead design? I know of the imperfections of the cutting surface but wondered if it can't be addresses in a different way? Maybe more soft of a base where the turntable it self sits? Any ideas and comments are much appreciated. Hoping to get the stepper motor mounted and get some motion on the lead screw this weekend.

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markrob
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Re: introducing my diy lathe assembly phase

Post: # 45582Unread post markrob
Sat Jan 14, 2017 11:28 am

Hi,

You want the cutterhead to ride in some sort of suspension. I've seen a simple adjustable spring (e.g. Presto 6N) or something like a turntable tone arm with adjustable counterweight (e.g Vestax VRX2000). If you try to set the cutting depth using some sort of fixed micrometer adjustment, I think you are doomed to fail. Remember, the groove is only 3-5 mils wide. That doesn't allow for much error. Even a small amount of platter runout or blank surface thickness deviation/warp will kill the depth control. So you allow the head to float and track the deviations. The resulting spring/mass system resonant frequency needs to be considered such that the head suspension reacts fast enough able to track changes in height (typically slow changing), but not too fast that you get bouncing. This also implies that you need some sort of mechanical damping to keep the system from oscillating (think critically or over damped system). The damping can be from a dashpot or friction introduced into the suspension. If you are good with some math and PM me with you email, I can send you a paper by H. Davies that goes through the theory of the entire mechanical design of a cutting system. From platter drive, to head design (he was one of the designers of the Grampian cutter head) to suspension.

Mark

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carlos820
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Re: introducing my diy lathe assembly phase

Post: # 45587Unread post carlos820
Sat Jan 14, 2017 1:51 pm

Thank you Mark, I have an idea how I can add a local suspension at the head mount location, going to work on developing that and report back when I have something to show. I really appreciate your reply Thanks again!

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CountMoogle
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Re: introducing my diy lathe assembly phase

Post: # 45603Unread post CountMoogle
Mon Jan 16, 2017 1:35 pm

Awesome awesome! I freakin love all the information! seeing all the handy work put into diy lathes is just so cool.

What I'm most confused about is the software side of things.
(I haven't had a chance to really look this up yet, but if you have answers I'd rather ask you directly)
You say "play tracks from DAW with inverse RIAA" But I have little understanding as to why this is needed.... or what It means heh.

the quote- "I'm an mechanical engineer not Musical Wizard, Damit!" comes to mind.

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