# Emergency brake



## Torbo (Oct 13, 2014)

I´m planning to make a emergency brake to my Crusader lathe. 
I'm thinking of making an iron rod hinged at each end, with a electrical switch connected in series with the stop switch. 

Has anyone made ​​such and can anyone give me some ideas about this project?


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## Torbo (Oct 13, 2014)

I´m planning to make a emergency brake to my Crusader lathe. 
I'm thinking of making an iron rod hinged at each end, with a electrical switch connected in series with the stop switch. 

Has anyone made ​​such and can anyone give me some ideas about this project?

Maybe a string can do the same thing as an iron rod?


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## JimDawson (Oct 13, 2014)

I assume you want to install this as a foot operated switch.  This is a common way to do it, many lathes come factory equipped with this system.  Normally it also operates a mechanical spindle brake.  Connecting the new switch in series with the stop switch is the correct way to do it.  I don't really have any advice on the best way to build it, but it needs to be designed so that it will not fail in use.  There are cable operated safety switches available.  Here is an example of what I am talking about:  http://www.automationdirect.com/adc...ax_Protection_Length_(SDM2_Series)/SDM2K96X11


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## Torbo (Oct 13, 2014)

Thanks! Maybe a string can do the same thing as an iron rod? Then I can have two, one in knee height and one in shoulder or abdominal height?

I will try that to morrow


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## JimDawson (Oct 13, 2014)

Torbo said:


> Thanks! Maybe a string can do the same thing as an iron rod? Then I can have two, one in knee height and one in shoulder or abdominal height?
> 
> I will try that to morrow




Yes, I think so.  Exactly how you make it is not so important, that it works when you need it is the most important.


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## Torbo (Oct 14, 2014)

I think emergency stop is a better name than brake. Im thinking of a electrical engine brake, but that is not possible with at AC-motor I have heard. DC motors is easy to stop, only to put the + to ground after switching off.

To day I will make a string arrangement for cutting the electrical wire/switch for the engine.


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## John Hasler (Oct 14, 2014)

You can electrically brake an induction motor by applying DC to one of the windings.  It does require some calculations to determine the voltage and some relays.  The DC must be disconnected quickly when the motor stops.  It won't hold the motor: just slow it quickly.


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## Torbo (Oct 14, 2014)

Thanks! That was interesting! Do you have some drawings? Shema? 
I was thinking of to put in some rectifiers/diodes in a loop in the stop phase? 

In the first time I will have this mechanical electric stop: 

Five flat iron bits and a little extra. The iron rod was 20 mmm i diameter.
It worked well
Fire flatjern men det kom et lite stykke til for å tilpasse bryteren.


In the end I used a micro switch




It is to little plase for the start stop hen del, but I will fix that tomorrow


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## mws (Oct 14, 2014)

FWIW: I added FWD, REV and JOG to my milling machine using a few relays. But I also wanted it to spin down much quicker, so I added a dead short across the normally closed contacts of the power relay. This shorts across the the motor's L1-L2 windings when the relay drops out.  It seems there is just enough remaining magnetic field in the motor when this relay shorts that it brakes the motor to about 50-60% of it's operating RPM VERY quickly, at which point the field collapses and it coasts to a normal stop.  

The comment about adding brief DC to a winding got me thinking; maybe I can replace the short with an appropriate sized capacitor/resistor combination that is charged while the motor is running. Hmmm...

Mark


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## GK1918 (Oct 15, 2014)

Forgot where I read about someone used a motorcycle disk hydraulic brake, master cylinder with a wide brake pedal.  The brake pedal has a plain ole stop light sw.  The switch then
went to a relay that interupted the power feed (before the drum switch) I thought that was slick.  If I remember correctly this was an under drive S Bend so all was hidden in the
cabinet.  I think the brake rotor was attached to motor drive pulley??  but it kills power and stopped it on a dime.....


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## Torbo (Oct 15, 2014)

Thanks for ideas.I remember when I was car-mecahnican I find that the windscreen - wipers had an electrical brake. In off position the + on the el.motor the viper got ground, and the induction/el.production from the motor stopped it momentary. I was a electrical brake. S.E.V. Mashall had a intern brake from the metal around the anker/rotor.Interesting if av condensation can make a brake? May be combined with some rectifiers ?


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## mws (Oct 15, 2014)

Torbo said:


> .Interesting if av condensation can make a brake? May be combined with some rectifiers ?



Oh it would have to be charged up to some DC value with some rectifiers. I already have everything needed; caps, diodes...  time however is always in short supply. Anybody got a device to slow the clocks?

If I come up with something workable I'll post it. 

Mark


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## Torbo (Oct 17, 2014)

Wery good! With DC arrangement it is also easy to make regulate the speed of the motor. Im wondering of to set a few big rectifiers i serie with one of the intake clamps, an ground them i off position, and have a open circuit in on position?It is easy to tray. Test circuit:Start the motor and stop it, while rotating I can check that the speed will be redused? Som other ideas would also be interesting?


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## mws (Oct 18, 2014)

Unfortunately the DC, applied to an AC motor, can only serve to brake (break  ) it. A variable speed DC motor is a completely different device entirely.


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## Torbo (Oct 18, 2014)

The emergency stop is working very good, and is very stable! I was thinking of to put a DC-generator and put the + to ground when stopping.But it take some place, so Im also thinking of a bycycle-discbrake. My be it can go under the cover where the engine is placed?But I will try some electrical thing first. ?


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## rwm (Dec 30, 2014)

Have you pursued a mechanical brake any further? I like the bicycle brake on the motor idea.
I need to do something like this also.
R


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## f350ca (Dec 30, 2014)

I used the caliber from an old snowmobile on a disk sander I built. The rotor I believe was from the rear of a GM pickup, turned down to smooth out the wear. These are a good heavy break, stops the 16 inch disk in a second or two where it will coast for 4 or 5 minutes. A bicycle one would work but the pads may wear fairly quick, they aren't meant to stand much abuse.



Greg


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## rwm (Jan 2, 2015)

That's a really nice sander! The snowmobile brake is a great idea. They make similar ones for go karts- cheap.
I have seen some large industrial lathes stop within less than one second when turned off. How is that typically done? Is it a brake setup on the spindle? Motor brake? Whay wouldn't all lathes come with a motor brake? Seems like and inexpensive upgrade.
R


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## f350ca (Jan 3, 2015)

rwm said:


> That's a really nice sander! The snowmobile brake is a great idea. They make similar ones for go karts- cheap.
> I have seen some large industrial lathes stop within less than one second when turned off. How is that typically done? Is it a brake setup on the spindle? Motor brake? Whay wouldn't all lathes come with a motor brake? Seems like and inexpensive upgrade.
> R



Thanks, built that sander a few years ago for the cabinet shop. will remove a lot of material in a hurry if you push it.
I haven't been around a lot of lathes but over the years I've owned 4, all had brakes. The Taiwanese 14x 40 had a pedal controlled brake that shut off the motor and operated a band brake on the motor shaft, it would stop almost instantly, great for threading up to a shoulder. The Colchester Student had a drum brake on the input to the headstock. The 16x 80 Summit lathe I have now is clutch driven with a wet band brake that comes on when the cutch is disengaged. At slow speeds it stops pretty quick, but takes two or three seconds to stop the 12 inch three jaw if your at 1000 or more rpm. My Hardinge has an electrically operated cork pad brake that rubs on a drum on the motor shaft. it slows it down pretty quick but not instantly, but it coasts for a long time if you shut the brake off.

Greg


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## uncle harry (Jan 3, 2015)

My Harrison M300 lathe has a primary v belt drive from the motor. The brake is a matching v-shaped shoe pivoted to rub in one of the pulley grooves. The shoe is connected to a foot pedal bar with a lever-based design connected to the shoe by a push rod. An adjustable trip bar interrupts the electrical latch when braking.

I have not powered my lathe yet but I have heard that this is a very effective brake.


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## Torbo (Jan 4, 2015)

uncle harry said:


> My Harrison M300 lathe has a primary v belt drive from the motor. The brake is a matching v-shaped shoe pivoted to rub in one of the pulley grooves. The shoe is connected to a foot pedal bar with a lever-based design connected to the shoe by a push rod. An adjustable trip bar interrupts the electrical latch when braking.
> 
> I have not powered my lathe yet but I have heard that this is a very effective brake.


@

Thanks everyone!
I like the matching v-shaped shoe pivoted to rub in one of the pulley grooves specially.

The easiest way to du it I think?
(If the electrical don work!)


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