Synchronous AC motor for leadscrew

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EmAtChapterV
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Re: Synchronous AC motor for leadscrew

Post: # 37081Unread post EmAtChapterV
Thu Sep 03, 2015 4:42 pm

Helical cut gears, I'm assuming.

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jesusfwrl
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Re: Synchronous AC motor for leadscrew

Post: # 37088Unread post jesusfwrl
Fri Sep 04, 2015 5:39 am

In general, helical gears are much quieter than straight cut gears. You can observe this on most cars, where there is a substantial gear whine when driving in reverse and it is much quieter when driving in the forward gears. This is because forward gears are helical gears while reverse gears are straight cut, because they are not used as much.
From the description of the Neumann gearbox, it doesn't sound that complicated as in having a real reduction. I would assume the fast motor is going straight through with no reduction. And the normal motor is going through a warm and gear drive which is a bit of a different story, although it does offer a reduction. It is much simpler and does not involve the several gears usually employed in more complicated differentials or reduction units. This can be achieved using only two gears and a centrifugal clutch. But, then again, I have no idea how it is really done by Neumann. Apart from the fact, that most off the shelf gearboxes for motors have straight cut gears that are really on the far opposite of precision engineering, they also have horribly imprecise bearings. The majority of the noise produced by helical gear or warm gear drive systems is not actually by the gears themselves but by the bearings. If the bearings are really well made, a helical or warm gear would not produce any noticeable amount of noise. Think of the feedscrew and half nut: it is essentially a gear drive which is used on all lathes and yet they still work without producing noise because of it. A good leadscrew has very precise bearing so they don't produce much noise either. There is no reason to avoid gears completely, unless you like the idea of replacing the leadscrew with a winch pulling the carriage with a rubber band.

Is the gearbox on the Neumann coupled directly to the feedscrew? Or is it driving the feedscrew via belt?
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
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Sillitoe
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Re: Synchronous AC motor for leadscrew

Post: # 37090Unread post Sillitoe
Fri Sep 04, 2015 7:21 am

I've been doing pitch motor comparisons for the last couple of months...
Check out brushless dc gear motors with integrated controllers, check data-sheets for the voltage range that the motor can be driven within.
Controlling both pwm and motor voltage can provide the full range of desired speeds.
Good luck. :D
James

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EmAtChapterV
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Re: Synchronous AC motor for leadscrew

Post: # 37097Unread post EmAtChapterV
Fri Sep 04, 2015 11:38 am

jesusfwrl wrote:There is no reason to avoid gears completely, unless you like the idea of replacing the leadscrew with a winch pulling the carriage with a rubber band.

Is the gearbox on the Neumann coupled directly to the feedscrew? Or is it driving the feedscrew via belt?
There's a rubber coupler between the gearbox and the leadscrew flywheel to reduce any potential vibrations and irregularities, but otherwise it's straight across in a straight line.

Speaking of a winch pulling the carriage across, has anyone ever seen or used a Hydrofeed lathe? I seem to recall they used hydraulic pressure sent through small (recording pitch) and large (lead in/out) valves to push the cutter carriage along, and the result was very smooth.

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jesusfwrl
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Re: Synchronous AC motor for leadscrew

Post: # 37100Unread post jesusfwrl
Fri Sep 04, 2015 12:10 pm

Thanks for the information.
Funny that you would mention an hydraulic lathe. I was just thinking the same thing this morning. :idea:

I have never seen this done on any disk cutting lathe, but it would definitely work. I was also thinking that the same thing could be accomplished using a pneumatic system instead of hydraulics, since the torque required is a bit too low to bother with oil. I am sure it would work great, although I am not sure if the cost of such a system would really be worth it. Precisely regulating air/oil pressure and damping sounds way more expensive than electric motors and gears. I might be wrong though. Both hydraulic and pneumatic cylinders of that size would be very cheap. The issue would be what comes before the cylinder. Also, air compressors and hydraulic pumps that run silent are usually very expensive. Unless you are situated in a pressing plant where you already have the air and oil supply available, it would probably cause more problems than it would solve.

I have an air supply here already which is located in a separate shed outside the building so I could theoretically try it out... Actually, if I had the spare cash I would do it just for the fun of it. I am drooling just at the thought of this! 8)

Unless you mean using a noisy motor and feedscrew assembly to move a hydraulic cylinder instead of moving the carriage and the hydraulic cylinder would just transmit the force to another hydraulic cylinder. Now, this is an interesting approach...I was also looking at air motors for driving the platter. Then, we would need a control panel with loads of gauges, switches and knobs and many many blinking lights and other stuff like that which would of course all be necessary for the task of feeling like you are operating a time machine instead of a disk cutting lathe. But wait... I already feel like that!
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
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gold
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Re: Synchronous AC motor for leadscrew

Post: # 37119Unread post gold
Sat Sep 05, 2015 2:38 pm

jesusfwrl wrote:
Is the gearbox on the Neumann coupled directly to the feedscrew? Or is it driving the feedscrew via belt?
I don't have a photo ready to go so I'll try a description. On the D shaft that is the output of the differential there is a chromed wheel about a 1/2" thick by 4" in diameter. A vulcanized rubber disc about 1/8" thick by 3" in diameter is attached to the flat face of the disc with a machined piece that is kind of like a Y. The bottom of the Y is attached to the metal disc face and the top of the Y attached to the rubber disc. The vulcanized rubber disc has two holes towards the outer diameter of the disc.

The same type of chromed wheel assembly is fitted on the lead screw. There are two screws with foam gaskets that protrude from the lead screw side. They fit in the holes of the vulcanized rubber disc. This is the decoupling.

This is from memory. I'll take another look at it when I'm at the studio but that's the basic idea. They use that method, less the extra chrome discs, to decouple the turntable drive shaft.

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mischmerz
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Re: Synchronous AC motor for leadscrew

Post: # 37126Unread post mischmerz
Sun Sep 06, 2015 1:22 am

Even a cheapo 200 Dollar turntable has 33,45 and 78rpm via electronic switching and belt drive. Surely that would be good enough to drive a lead screw? Most of them have some form of +/- ten percent of speed variation. I think it should be possible to patch some electronics into the equation to have a bit greater variance? One could use the 45rpm with variable set to -20% as 'normal' speed to drive the lead screw with 20% speed available to increase the pitch. And switch to 78rpm for lead-ins or lead-outs. This is how I am (probably) going to drive my lathe :)

mm.

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jesusfwrl
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Re: Synchronous AC motor for leadscrew

Post: # 37127Unread post jesusfwrl
Sun Sep 06, 2015 4:25 am

What turntable are you thinking about?
My turntables are all belt drive and use synchronous AC motors that run at a constant speed and the speed change is done by mechanically moving the belt to a different size pulley.

The technics SL1200 doesn't not land itself to easily remove the motor and use it somewhere else unless you plan on using the entire platter as a flywheel? I have never opened the audio technica or stanton SL1200 clones so I don't know what motor they are using. Some extremely cheap belt driven turntables that have 33, 45, 78 capability along with a -/+10% pitch that people use to throw on the street before the crisis have some extremely tiny DC motors with not much torque at all. I picked up some of them from the street a few years ago and quickly realised why they were thrown on the street...

It's a good thought though, if you can find the right motor in a turntable.
However, if you do not already have a turntable with a suitable motor, it would probably be cheaper to just buy the motor alone together with a drive unit rather than buying the entire turntable just to scavenge the motor.

What lathe are you using, mischmerz?
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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mischmerz
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Re: Synchronous AC motor for leadscrew

Post: # 37128Unread post mischmerz
Sun Sep 06, 2015 10:58 am

I am talking about a Gemini TT-1100 .

http://www.amazon.com/Gemini-TT-1100USB-Belt-Drive-Turntable/dp/B001UJS9EE

Yes, the motor is small. But it should have enough torque to run a lead screw, especially with the right pulleys. I have a Rek-O-Kut ./ Grampian. And I am currently thinking about building my own lathe to advance into stereo cutting.

Michaela

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dimi751
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Re: Synchronous AC motor for leadscrew

Post: # 37132Unread post dimi751
Sun Sep 06, 2015 8:38 pm

What's the torque specs on the Gemini ??

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Re: Synchronous AC motor for leadscrew

Post: # 37134Unread post mischmerz
Sun Sep 06, 2015 10:52 pm

dimi751 wrote:What's the torque specs on the Gemini ??
Not a lot I am sure. But it *might* be enough for a lead screw if it has an appropriate pulley. It would for sure be an easy solution. And there might be a few other turntables around with the same technology and more torque.

Michaela

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dimi751
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Re: Synchronous AC motor for leadscrew

Post: # 37135Unread post dimi751
Sun Sep 06, 2015 11:11 pm

Be carefull because there might not be enough torque on the Gemini to drive the rek o kut leadscrew

I can't comment on your over head because I've never owned one so I have no cue wether this will work.

I would play it safe maybe a technics sp10 mk2 or try the oem decks start torque 4.5kg and running torque 3.5kg

The family of oem decks are as follows these have start torque 4.5kg

Stanton (ST-150 & StR8-150)

American Audio (HTD 4.5)

Audio-Technica (AT-LP1240-USB)

KAM (DDX5000)

Synq (Xtrm 1)

Reloop (Rp6000 Mk6b)

Regards
Dimi

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Re: Synchronous AC motor for leadscrew

Post: # 37136Unread post mischmerz
Mon Sep 07, 2015 12:05 am

dimi751 wrote:Be carefull because there might not be enough torque on the Gemini to drive the rek o kut leadscrew
i

You may not be able to use any units that use some form of feedback (like magnets under the turntable). And most of them are direct drive while the Gemini has a belt drive which makes things a lot easier. I personally wouldn't use a Rek-O-Cut bridge with this, but a maybe a linear ball bearing slide with a lead screw or even a tooth belt.
blafasel.jpg
I know that is a bit flimsy, but you get the idea :)

Michaela
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jesusfwrl
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Re: Synchronous AC motor for leadscrew

Post: # 37139Unread post jesusfwrl
Mon Sep 07, 2015 3:57 am

It might work to use the Gemini table parts, but I'm still wondering why not just get the same or a similar motor on its own?

I've never seen the motor in the Gimini but the ones I have seen in similar arrangements, are all just simple brushed DC motors. Just take apart a cordless drill and you'll get a much more powerful motor.

The speed control for such motors is really simple, if you can get a basic motor with decent torque, controlling the speed would be the easy task. I am experimenting a bit with such motors that I had laying around but most of mine are either too small or too noisy.

I am going to take apart a cordless drill soon and see what that can do. But, for a final solution I would probably prefer a bl DC motor with encoder and servo controller. What I am still debating would be direct drive vs. belt drive.

So, does anybody know what type of motors are used on the VMS70 and how their speed is controlled?

Since it uses two motors, I assume their control method did not provide the option of getting the entire range form a single motor.
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Re: Synchronous AC motor for leadscrew

Post: # 48435Unread post EpicenterBryan
Sun Nov 12, 2017 11:12 pm

jesusfwrl wrote:Let's get more specific: the feedscrew in the fairchild has a pitch of 35 tpi.
I've found mine is actually 32 TPI.

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Re: Synchronous AC motor for leadscrew

Post: # 48436Unread post petermontg
Mon Nov 13, 2017 7:50 am

Here is a motor that is used elsewhere for feedscrew.

https://www.maxonmotor.com/maxon/view/service_search?query=386255

With regards to Neumann motors, There are a couple of motors in there controlling different functions. I will have a look through my files here later for you.
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