[modeleng] Fw: 12V variable speed power supply

Hello Rich

As mentioned in my last message (below) the Proxxon controller solved my 
variable-speed problems.

BUT the bottom speed of the rotation of the leadscrew was too fast, despite 
the gearing of the pulleys (and the small dimensions of the lathe precludes 
a larger driven pulley)..   I have overome this problem by installing a 
small countershaft, which reduces the bottom speed to 7rpm.   I would like 
this to be even slower, and if I can find a scrap of say 5" round aluminium, 
this will do the trick.   In the meantime the turning finish at this speed 
is very good.

If you DO convert your hobbymat, give me your email address, and I will 
illuminate this idea with pictures.

Cheers!   Hubert


----- Original Message ----- 
From: "Shep" <shep.28@xxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Friday, September 19, 2008 4:12 PM
Subject: Re: [modeleng] 12V variable speed power supply


> Hello Julian and Rich
>
> Thank you again for your sage advice.   I tried out the dimmer switch 
> set-up, and as you predicted, it lost torque at low speeds.
>
> Last evening, looking through ME adverts, I saw an easy answer to my 
> problem - A Proxxon  power supply unit NG 5/E.   As it is such a beautiful 
> day, I drove from St Albans to Dunstable to visit Chronos.   This power 
> supply produces 12V DC with 5A capacity.      It has thyristor electronic 
> speed control (with feedback) and does not lose torque on the lowest 
> speeds. It is a very neat looking job.
>
> Unfortunately I have no knowledge of electronics and am therefore, at my 
> great age, unable to assemble components.   Had I this knowledge, I would 
> have dispensed with screwcutting by gears, used a stepper motor and 
> controller, (suitably programmed) to produce an infinity of screw threads 
> and fine feeds..   Two rotary encoders would ensure that the mandrel and 
> leadscrew were always in synch.    As I had no-one to help me set up this 
> most desirable system, I have opted for a conventional change-wheel 
> screw-cutting system and the variable feed as mentioned above.
>
> Rich - if you DO make a mod to your Hobbymat, I think that the Proxxon is 
> an idiot-proof, neat and successful, and relatively inexpensive method. 
> It does what it says on the box!
>
> I thank all friends who have contacted me.    What a wonderful, friendly 
> and helpful List!
>
> I am glad to see that my original message has cleared the 'block' and that 
> there have been so many messages over the past few days.   I get quite 
> lonely when the messages dry up!
>
> Cheers!   Hubert
>
> 

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