One Speed Pulley Problem

One Speed Pulley Problem

Postby PopFugitive » Thu Jan 03, 2019 8:47 am

Hi all,

I'm having a bit of a problem with my VPI Prime motor. I've ordered an ADS, with the intention of installing a one-speed pulley so that I can use two belts simultaneously.

My pulley has arrived, and it looks too big. I've attached a photo of my existing pulley. My VPI Prime model is a Hong Kong market model meaning it runs on a 50hz 230V power supply.

Do I have the wrong pulley? I assumed that my motor ran at 300rpm but I'm no longer sure that's the case. If so, any idea how I can get a pulley for my particular motor?

Thanks all!
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VPI Prime Pulley.jpg
VPI Prime Pulley
VPI Prime Pulley.jpg (417.38 KiB) Viewed 698 times
PopFugitive
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Re: One Speed Pulley Problem

Postby Beck » Thu Jan 03, 2019 5:28 pm

I think you have the wrong pulley. Your pulley looks like a Scout pulley. Look at the motors on VPI's website and you will see what I am talking about. A single speed pulley should look like that which is attached to the Signature motor.
Prime #16-67| Fat Boy 10 | Dual Pivot | Ortofon Cadenza Black | ADS | Ayre P-5xe phono preamp, K-5xe preamp, and V-5xe amp | Audio Sensibility Statement SE interconnects and Testament speaker cables | Magneplanar 3.7i | Mapleshade audio rack
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Re: One Speed Pulley Problem

Postby patagonia » Thu Jan 03, 2019 5:43 pm

you should have 250 rpm 50hz motor thats the used for the 220v Prime´s.

The ADS Will supply 110v 60hz so you would need a diy pulley to catter for the differences, but you Will still have 110v only so don´t know if the torque the motor will give you Will be enough, you could buy the correct hurst motor under US$100 think it will be easier and cheaper tan making a special pulley.
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Re: One Speed Pulley Problem

Postby patagonia » Thu Jan 03, 2019 5:52 pm

A correction, read on another thread that the ADS can be bought Factory configured for 220/50, did not knew that, if yours is 220/50 please discard my previous message.

Regards
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Re: One Speed Pulley Problem

Postby PopFugitive » Thu Jan 03, 2019 8:12 pm

Thanks all. Should be getting my ADS in the coming weeks so going to see what speed the motor ends up running then. My pulley is definitely not either 300rpm or 600rpm looking at photos so maybe that will shed some light.

I fear I may need to either come up with a DIY solution or (more likely) buy a new motor!
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Re: One Speed Pulley Problem

Postby Brf » Thu Jan 03, 2019 8:59 pm

PopFugitive wrote:Thanks all. Should be getting my ADS in the coming weeks so going to see what speed the motor ends up running then. My pulley is definitely not either 300rpm or 600rpm looking at photos so maybe that will shed some light.

I fear I may need to either come up with a DIY solution or (more likely) buy a new motor!


If your Prime was spec'd for the Hong Kong market, it will have a 50hz motor installed. I assume that the turntable runs at the correct speed when plugged directly into the wall.

50hz per second x 60 seconds (1minute) = 3000 rpm for a 2-pole motor. The Prime motor has 12 poles, therefore, it will run at 3000/12 = 250rpm

Pulley size for a 50hz 250rpm motor with a 12" platter = [(12 +(.125)(.5)) x 33.333]/250 = 1.60"
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Re: One Speed Pulley Problem

Postby PopFugitive » Thu Jan 03, 2019 10:55 pm

Thanks - that is massively helpful. It explains the pulley size difference too - the pulley likely isn't that much smaller than that on a 300rpm 60hz motor.

Now my problem is that my local distributor doesn't think that there is a one speed pulley for my motor, which is a bit frustrating. I'm going to have to find a way to get something else that works...
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