Rek-o-Kut Platter speed

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concretecowboy71
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Rek-o-Kut Platter speed

Post: # 46030Unread post concretecowboy71
Wed Feb 08, 2017 10:26 am

Howdy:

As a part time hobby/project, I have been restoring an old Rek-o-Kut Imperial. The rubber rollers have been redone by Terry's Rubber Rollers and the machine has been stripped and lubricated.

The platter currently is running at about 45.2 rpm. I tried blending a heavier oil into the spindle well to possibly slow it down, but that has not worked. The motor is a type of synchronous AC motor and I am considering getting a variable frequency power supply. Has anybody used one of these for a Rek-o-Kut? The power supplies on the market range from 3 watts up. Does anybody know how many watts those old motors need on the Rek-o-kut rim drive TTs?

Any other suggestions are welcome too. Paired with a Grampian C Type head, this rig sounds very good.

Thanks!
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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markrob
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Re: Rek-o-Kut Platter speed

Post: # 46032Unread post markrob
Wed Feb 08, 2017 12:12 pm

Hi,

Check the rating plate for the motor. If its like the 6N's, they used a 1/15 HP Bodine NYC34 (IIRC). 1/15 HP is about 50 watts (750/15), so I'd go for a drive that can do a bit more than that. You want a drive that can do V/F compensation if you want to run over a wide speed range. You could also go the route of modifying a car inverter to allow you to adjust the frequency and output voltage. I did this for a simple 100 watt modified sine inverter and it worked really well. The modified sine types will run the motor a bit hotter, but it seems to be OK. Nowadays, there are true sine wave inverters on the market that would be a better choice. Going that route requires some electronics knowledge. May be best to go for a commercial drive.

One other way to drive the motor would be to use a 100 watt or bigger audio amp with a variable oscillator at the input. Depending on the amp, you might need a step up transformer to match the impedance of the motor. For example, an amp that can drive 100 watts into 8 ohms will produce 28 Volts AC RMS so you would need a about a 4:1 step up transformer to drive the motor.

Mark

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concretecowboy71
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Re: Rek-o-Kut Platter speed

Post: # 46048Unread post concretecowboy71
Thu Feb 09, 2017 2:26 pm

Thanks for the info. I don't have the skills to hack a car inverter. I was hoping for a more off the shelf solution. I have very strong mechanical skills, but lack the skills needed to make something myself.
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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markrob
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Re: Rek-o-Kut Platter speed

Post: # 46049Unread post markrob
Thu Feb 09, 2017 3:03 pm

Hi,

I did a quick search and found this manufacturer that makes small single phase in single phase out V/F drives

https://www.wolfautomation.com/manufacturers/leeson/ac-drive-25hp-115v-2-4a-single-phase

Looks like it costs about $250

Might be able to snag a used one on Ebay for less.

Looks to be all analog so the frequency is variable over a continuous range from 0-60 hz via a pot. Look at model 175320 1/4 hp max 115 Vac in - 115 Vac out

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Re: Rek-o-Kut Platter speed

Post: # 46051Unread post Gus
Thu Feb 09, 2017 5:08 pm

markrob wrote:Hi,

I did a quick search and found this manufacturer that makes small single phase in single phase out V/F drives

https://www.wolfautomation.com/manufacturers/leeson/ac-drive-25hp-115v-2-4a-single-phase

Looks like it costs about $250

Might be able to snag a used one on Ebay for less.

Looks to be all analog so the frequency is variable over a continuous range from 0-60 hz via a pot. Look at model 175320 1/4 hp max 115 Vac in - 115 Vac out
As always nice find Mark!
if i knew it, i didn't bought 50hz pulley for my Rek-o-Kut...

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concretecowboy71
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Re: Rek-o-Kut Platter speed

Post: # 46065Unread post concretecowboy71
Sat Feb 11, 2017 11:18 am

Thanks for the info!
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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Re: Rek-o-Kut Platter speed

Post: # 46066Unread post concretecowboy71
Sat Feb 11, 2017 11:30 am

http://www.ebay.com/itm/Leeson-Speedmaster-Adjustable-Speed-AC-Motor-Control-174930-1-4HP-/262822178481?hash=item3d316c2eb1:g:fNQAAOSwo4pYiALC

Is this something that might work? I am sorry for my ignorance here, but this is new territory for me and I know nothing about motors. I thought this would be a fairly easy problem to solve. Perhaps it is, I don't know.
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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markrob
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Re: Rek-o-Kut Platter speed

Post: # 46067Unread post markrob
Sat Feb 11, 2017 1:29 pm

Hi,

Doesn't look like it will. Its single phase 120/240 Vac in, 230 Vac 3 phase out. That's configuration is much more common than the drive I pointed to.

Mark

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Re: Rek-o-Kut Platter speed

Post: # 46068Unread post concretecowboy71
Sat Feb 11, 2017 1:37 pm

Great thanks. I will look farther into the drive you suggested.

I am also going to pull the rek-o-kut apart again and get info off the motor badge.
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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mratx
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Re: Rek-o-Kut Platter speed

Post: # 46070Unread post mratx
Sat Feb 11, 2017 3:13 pm

If you keep an eye out on ebay, you can probably get an Invertek Optidrive VF drive for under $100, just look for one where the five digit model number begins with an 11 (like ODE-2-11005), those are the 100-120v models, the 12 number series are 200-240v.


Mark

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Re: Rek-o-Kut Platter speed

Post: # 46071Unread post markrob
Sat Feb 11, 2017 3:28 pm

Hi,

I see the older Invertek series on eBay. This seller has 5:

http://www.ebay.com/itm/INVERTEK-DRIVES-LTD-0-43HP-OPTIDRIVE-OD1-11033-BTU-100-120V-CC-/192099984668?hash=item2cba0d251c:g:RJYAAOSw4A5Ym9Rg

I would offer quite a bit less since he is selling untested ($75??). I tried to fine a manual on-line at Invertek and they don't seem to post it. The newer E3 series would also be good, but probably go for more $.

It would be good to see if your motor is a synchronous type as that can't be adjusted over a wide speed range (maybe +/- 20%??). Not a big deal since you seem to only need to trim the speed a bit. If you wanted to try half speed mastering, That might be an issue.

Mark

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Re: Rek-o-Kut Platter speed

Post: # 46162Unread post concretecowboy71
Tue Feb 21, 2017 9:31 am

Here is a pic of the motor:

Imagerekokutmotor
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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markrob
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Re: Rek-o-Kut Platter speed

Post: # 46164Unread post markrob
Tue Feb 21, 2017 10:07 am

Hi,

That motor is much smaller that the Bodine NYC-34. 1/100 HP is about 7.5 Watts. The rating shows .4A or 48 watts. I'm guessing it probably draws somewhere between the two values. Might make sense to look at going with an audio power amp and step-up transformer. 50-100 watts should do. A 120 Vac to 24 Vac step down transformer run in reverse as a step up should do nicely ( 50 watts into 8 ohms is 20 Vac RMS). Get one rated for 50 VA or more. For example:

http://www.digikey.com/product-detail/en/triad-magnetics/TCT50-05E07AB/237-1612-ND/3995772

If you are cutting from a DAW, you can use one of the two outputs to generate the correct frequency needed to get the motor to speed. Use the other for the Mono audio to the cutterhead. Just calculate the frequency using the formula:

(desired speed / actual speed) * 60 hz = frequency

In your case:
(45/45.2) * 60 = 59.73 Hz

In the DAW, adjust the drive to the power amp so that you have 120 Vac on the secondary of the transformer with the motor connected and you are good to go. If the amp is stereo, you can bypass the electronics in the K8 and drive the head directly.

If you have a spare power amp sitting around, you can run the experiment pretty cheaply ($18 for the transformer) and some time to wire things up.

Mark

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Re: Rek-o-Kut Platter speed

Post: # 46268Unread post concretecowboy71
Tue Feb 28, 2017 8:57 pm

After a lot of research, it seems that it should be unusual for this kind of motor to run fast. Unless there was a bad problem with the actually frequency of the power from the wall. I ended up solving the problem mechanically by lightly sanding the rubber roller. I could see the motor running slow due to dirt and wear, but fast should be almost impossible. Is this a correct conclusion for a synchronous motor?
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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markrob
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Re: Rek-o-Kut Platter speed

Post: # 46269Unread post markrob
Tue Feb 28, 2017 10:30 pm

Hi,

That's correct. However, the final speed of the platter is also determined by the ratio(s) of the motor pulley shaft diameter, platter diameter, and possibly rubber roller(s). Its also possibly that the AC line frequency could be off, but in the US, I doubt this would be a big factor. If you are using a strobe disc to make the measurement, a it would read the correctly in spite of line frequency variation if that were the only source of speed error. How did you determine the speed?

Mark

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Re: Rek-o-Kut Platter speed

Post: # 46275Unread post concretecowboy71
Wed Mar 01, 2017 9:36 am

Twofold:

We did use a strobe. I understand that it could be misleading because the lights we would be using would be "strobing" at the same frequency that the motor would be locked into.

We are also using test tones, cut and transcribed back into the computer using a quartz lock turntable (Technics SP15) that we feel should be a good benchmark for speed. We then compare the tones and see where they come in. We are still a tad bit off, but I did not want to keep shaving the rollers until I was sure that I was heading the right direction.

Thanks for your help on this.
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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Re: Rek-o-Kut Platter speed

Post: # 46276Unread post markrob
Wed Mar 01, 2017 10:15 am

Hi,

I was going to suggest just what you are doing. Also note that you can make slight changes in the speed based on the pressure that is applied to the rubber drive elements. The change in pressure changes the effective diameter. Not sure on your unit if that is adjustable. Too little pressure and you will have slippage. Too much and you may load down the motor. Also note that in some cases, the rubber drive elements function as an idler. In this case, it has no effect on speed. If the rubber roller is a compound type (two rollers on one common shaft), then the ratio of the two rollers does affect the speed.

Mark

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Re: Rek-o-Kut Platter speed

Post: # 46277Unread post concretecowboy71
Wed Mar 01, 2017 10:33 am

Great! You have verified a lot of what I am experiencing. The rollers are indeed compound (one stacked on the other essentially). I shaved the roller that was in direct contact with the platter and that made the difference that I needed. There is adjustment for roller pressure and I have been experimenting a lot with that. I have experienced both slippage and motor loading that you mentioned, but have found a good medium point with good torque and no indication of undue load on the motor.
Cutting Masters in Bristol,Virginia, USA
Well Made Music / Gotta Groove Records

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