# Atlas Modifications On The Older Models



## Round in circles (Aug 23, 2015)

I had a near miss today when I reach forward to engage the drive from the running motor and got a "wake up dopey " rap on my knuckles for lowering my hand on to the now moving chuck as I moved back from the machine.


Has any one modified their lever system , so it's safer to take up or disengage the drive whilst the motor is running??

If anyone has ,would you be so kind and pop up a picture of it please , I'd like some inspiration ..I think  .


----------



## wa5cab (Aug 24, 2015)

Of course I have a machine where the belt tension lever isn't across the chuck from where the operator stands.  But I have never understood why anyone would think that they needed to start the motor with the belts slack and then tighten them to start the spindle.  Plus I would not trust such a system anyway.  To me, it looks like a bad accident just waiting to happen.  There isn't much chance that the thing will start on its own, but the probability is non-zero.  And if you happened at the time to be loading something into the chuck, you could easily lose a hand or worse.


----------



## ogberi (Aug 24, 2015)

Same situation on my SB9 9" lathe.  The lever to slack the headstock belt requires reaching over the chuck.  I disengage it only when the machine is stopped.  I get a little bit of slip when starting the lathe at high speeds, but only for a second and then it's golden.  

I do a lot of work between centers and the drive plate + dog whirling around makes me extra cautious.  I recommend to stop the lathe before engaging or disengaging the lever.  Safer that way.


----------



## Round in circles (Aug 24, 2015)

For a while now , after reading it somewhere  I thought it was said it is sound engineering practice to start the lathe with the tension off the belts so that the motor has less of a load hitting it on start up and the bearings will also have less of a shock load on them if engages smoothly & slowly building up from a stopped position.  The belts will also have less wear


----------



## John Hasler (Aug 24, 2015)

Round in circles said:


> For a while now , after reading it somewhere  I thought it was said it is sound engineering practice to start the lathe with the tension off the belts so that the motor has less of a load hitting it on start up and the bearings will also have less of a shock load on them if engages smoothly & slowly building up from a stopped position.  The belts will also have less wear


You're only reducing wear on the belts and bearings by a very small amount.  I doubt that it is worth it.


----------



## wa5cab (Aug 24, 2015)

Actually, as far as the belts go, belt wear is obviously greater when you slip the belts to start the spindle.  The only advantages of starting the motor with the belt slacked are slightly lower peak power consumption in the motor when you start it unloaded and you don't bang the direct drive pin.  Otherwise, you slip and therefore wear the belts every time that you start.  Unless you have one of the underdrive cabinet models, the practice is hazardous to the operator because on most Atlas machines you have to reach over the chuck or headstock to tighten the belts.  Unless you have a flat belt machine or are using link belts, the belts should not slip under normal starting torque.

In brief, on most Atlas built machines this is a hazardous practice.  Don't do it and don't tell anyone else here to do it.


----------



## Round in circles (Aug 25, 2015)

OK Robert or any of the MODS 
Can you delete the whole thread ..  I hear what your saying loud & clear . 
 I've always tried to follow the ethos of :- 

" Never tell folk in detail , how to do dangerous practices " 

 Thanks 
Dave


----------



## wa5cab (Aug 25, 2015)

Dave,

First, my comments weren't aimed at anyone specifically.  The practice isn't limited only to older Atlas machines.  As far as deleting the thread, I went back and read through it again from the top and on balance it would tend to discourage rather than encourage the practice.  So we'll just leave it be.

Now if someone would just come up with a way to economically soft-start a capacitor start motor...


----------



## Round in circles (Aug 26, 2015)

You can buy soft start switches ( I think ) already wired to just connect your wires into .

Let me have a play ......   I'll be back in a few.


----------



## Round in circles (Aug 26, 2015)

Some soft start diagrams .. I don't think you need the external can capacitor supplied but have to substitute it with one shown in the diagram.
Here are some soft start schematics but I think they are for 3 phase .
https://www.google.co.uk/search?q=s...35#tbm=isch&q=soft+start+motor+switch+circuit.

Remember .... I've had a couple of strokes since my apprenticeship days of nearly 50  years ago & since I did my advanced electronics courses over 35 years ago .

I remember playing with " Fenner " speed controllers that gave a soft start & were three phase , but I think that the solution for single phase machines is a speed controller that employs a chopper circuit as in eBay item #191401533404.

Let me know what you think as I may be completely off the scent these days .


----------



## markba633csi (Aug 30, 2015)

I would think you could just reduce the value of the start cap (but not too much) to give less starting current and therefore starting torque. Try around 15-20% less microfarad.  Bet it works.  Don't try it on a permanent split cap (capacitor run) motor though. 
Mark S.


----------



## wa5cab (Aug 30, 2015)

+/- 15 to 20% is the typical tolerance on electrolytics.  50% reduction might work.  But you would have to cut the duty cycle about in half (number of starts per hour).


----------



## timmeh (Sep 10, 2015)

Something to keep in mind on this subject. Think about the position you are in when doing that, i.e. motor running, reaching over to engage drive belt.... and something decides to go pearshaped? I always keep well out of the way of potential things sticking in my head/torso on start-up, until well tested and if a little dodgy(e.g.between centres) just say out the way always.


----------

