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Has Anyone "made" A Foot Brake?

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lowlife

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#1
Just wondering? It seems if I could make the VFD stop the lathe quick enough that maybe I could hook a rigged up foot brake to a micro switch or something. Seems similar to an E brake knob.

Its getting late for me, maybe this is one of those thoughts that should remain in my head?
 
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British Steel

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#2
I've been planning on doing exactly that, I fitted my lathe's VFD with brake resistors (from China... 80 Ohms, 1500w as per manufacturer's specifications but about 1/10th the price), I'm planning a checquer plate bar hinged from the lathe base with a couple of springs, actuating a pair of normally-closed microswitches wired in series. Painted in yellow and black diagonal stripes so it's Obvious!
I already have a Big Red Button E-Stop over by the door so my nearest and dearest don't have to step over my corpse and dodge dismembered flailing limbs to turn the lathe off...
 

lowlife

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That is very gracious of you to think of your loved ones like that!
 
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British Steel

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#4
Thanks, that's the problem with an attached garage/workshop, they get annoyed by the noisy noise in the night, damn youngsters - in my day we wouldn't have heard it over the stereo :(
 

BROCKWOOD

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#5
Ah a Foot Brake & a Neutral for mine would be sweet! Gonna require a few 20A interrupting current relays just to begin for me. I like the All Stop mentioned above. I have Emergency Kills on both sections of my lathe / mill combo. I just so happen to have them split onto separate circuits so the lathe can power feed milling operations. I know to kill the feed first if I get in a bind while milling, but was startled the other night when my wife came out (& forgot protocol). Oh & kill the mill too. The lathe portion is belt driven through a gear train - so there is 'coast' when stopping & no 'neutral'. I can see adding a simple hydraulic disc brake operated by a foot pedal - as the OP said - once the power is tripped. Back to lowlife's setup, If the VFD uses a stepper motor, would not a micro switch as he suggested halt the motor immediately. Assuming it has enough oomph to overcome all the moving parts it kept in motion?
 
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British Steel

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#6
Hydraulic disc brake would work - and you could add a second master cylinder teed into the hydraulic line, activated by a spring and with a solenoid to latch it "off" when power's applied that releases when power drops on hitting the Estop? You'd have to reset it each time you powered the machine up, but worth it maybe?
I've not thought about stepper motors, but the VFD with braking resistor does a pretty good job of stopping "on a dime" (as I believe they say in the rebel colonies).

Dave H. (the other one)
 

MozamPete

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#7
I already have a Big Red Button E-Stop over by the door so my nearest and dearest don't have to step over my corpse and dodge dismembered flailing limbs to turn the lathe off...
That is actually a good idea I need to file away for my future workshop build. If your wiring a new workshop anyway an E-stop at the entrance that kills all the sockets is a great idea (probably want to leave the lights on a different circuit).
 

uncle harry

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#8
My late 70's vintage Harrison M300 lathe has a foot brake that interrupts the electric latched circuit and has a friction brake that uses the v-belt grooves on one of the drive pulleys. It is a standard feature on many makes of engine lathes.
 

Downunder Bob

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#9
A foot brake is not something I have, but I have thought about it. My thoughts are to repurpose an electric 12V clutch from a car A/C unit, wiring it in, such that when the brake pedal, or the emergency stop button, is pressed The holding power relay for the motor drops out and automatically switches on the repurposed clutch/brake. The 12V supply comes from a battery which is always charged as I run 12V lights and coolant pump, and other bits around the shop. The clutch/brake would mount on the main spindle shaft, or alternatively on the shaft input to the headstock gearbox. Not sure yet, it's not an urgent project just a thought.
 

Tozguy

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#10
I was extremely uncomfortable with the time it takes for the lathe to coast to a stop after pushing the big red mushroom switch on the front panel. So I cobbled some things on the lathe to 'stop' the lathe more quickly.
Basically a trip wire or lever operated friction brake on the unused grooves of the motor pulley. It is a contraption that only a mother could love but it works and I feel better with it being available. I suspect that it stops the lathe more quickly than would my shirt wrapping around the chuck.
 

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Latinrascalrg1

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#11
I was extremely uncomfortable with the time it takes for the lathe to coast to a stop after pushing the big red mushroom switch on the front panel. So I cobbled some things on the lathe to 'stop' the lathe more quickly.
Basically a trip wire or lever operated friction brake on the unused grooves of the motor pulley. It is a contraption that only a mother could love but it works and I feel better with it being available. I suspect that it stops the lathe more quickly than would my shirt wrapping around the chuck.
I Like your brake setup....I have been contemplating doing something similar which leads me to this question if you wouldnt mind answering..... Is your setup completely Manually activated
Or is it automaticlly activated by hitting the stop button? Looking at the pictures you posted i can see the mechanical aspect pretty clearly however I think i also see some kinda solenoid that im not sure about but think it may activate your brake and would like to know how it works if you wouldn't mind elaborating a bit?
 

Bob Korves

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#12
The factory spindle brake that came with my Kent 13x40 is just two expanding brake shoes, completely enclosed by the headstock side v-belt pulley, inner workings not visible. The drum size could not be more than 4" (100 mm) in diameter, but it stops the spindle apparently instantly, even with a large 4 jaw chuck and a heavy part spinning at high rpm. The motor is automatically turned off at the same time. The slowdown is not visible at all to the eyes, step on the foot pedal, it is immediately stopped. The real issue is having my brain engaged and my foot above the pedal, which only happens quite rarely on iffy operations. To use it when surprised by something randomly turning bad would take a lot longer, nearly all of that time taken up by getting the operator (me!) awake, focused, and remembering what to do.

I used the brake for internal threading to a close shoulder until I figured out how to thread outward rather than inward. It hasn't been used in many years now. Still nice to have for dicey operations, but I now try to avoid dicey operations... :eek 2:
 

Tozguy

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#13
Sure rascal,
It is completely manual. There is no solenoid. You may be referring to the little black switch in pic 471. This is the relay switch from the chuck safety hood. The chuck hood was taken off the lathe a long while ago. The switch was repurposed and located under the chip pan.

The leather strap surrounding the motor pulley is 2 ply. The two plys were glued together so they would match the curvature of the pulley. One end of the strap is anchored to the cabinet while the other end is held by a spring. When running, spring tension is held by the tip of a rod that sits between the cabinet and chip pan. There is no tension on the strap and the pulley turns freely with very little rubbing on the strap. When the rod is retracted the spring is released and it pulls tension on the leather strap. The rod only has to move a 1/4 inch before dropping the spring.

When the cross pipe in pic 471 is rotated either by the red handled lever on the left or by the trip wire near the floor in pic 470, it retracts the rod. Pic 474 shows how the the cross pipe acts on the rod. Ignore the curved white strip of plastic, it has no function in the system. The relay switch is set to trip before the rod drops the spring.

Hope this helps. Don't hesitate if you have more questions. Bob's words resonate with me. While working on the brake system I was saying to myself 'make durn sure you need have to use this contraption'.

PS Your idea of a solenoid connected to the main panic button is excellent. I am sure that there are many other ways in which my set up can be improved.
 

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Reddinr

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#14
I plan to do a similar thing, maybe this winter if time allows. My lathe already has a brake but I will be adding a VFD and plan to have the VFD decelerate the spindle fairly rapidly. On most VFDs he deceleration time is programmable so you can do what is most suitable for your lathe and size of work piece. I will likely disconnect the hardware brake shoe and attach the contacts of the brake switch to a VFD input. In general, the "off" or "emergency off (EMO)" circuits should have switches that have normally closed contacts and open when activated. This guards against a loose or broken wire causing the circuit not to work when you most need them. If there is a loose wire the motor won't start and it gets fixed prior to emergency or needing to turn off. Your VFD manual should show specific wiring and programming for the various on/off/EMO switches. They are all similar but . On mine, I plan to have the EMO button still separately activate a contactor on the input of the VFD to get the more complex VFD circuitry out of the equation if there is a true emergency. What VFD do you have?

Of course I thought of something else after posting... An off switch like a micro-switch would be momentary, not a maintained contact. If it is wired into the FWD/REV circuit it may require a relay in the circuit that drops out when the brake is activated and stays off until reset somehow. Otherwise the lathe would stop but could start up again once your foot leaves the brake pedal. Some VFDs can be set up with a "trip" input that does not require such a relay. It is VFD and VFD set-up dependent.
 
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Latinrascalrg1

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Tozguy, Thank you very much for clearing that up so quickly. So that i understand, what i thought was a solenoid is a switch that kills the motor as soon as the brake if manually activated, correct?

The way i was planning on setting the brake was would be considered a "Deadman kill switch." I was thinking about having a foot pedal bar setup that needs to be stepped on to run but automatically stop the motor and spinning chuck when foot is removed. Being a NOOB i was thinking more about my safety being alone in the shop but haven't made a final decision yet so thanks again for sharing your setup, I Appreciate it.
 

uncle harry

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#16
I plan to do a similar thing, maybe this winter if time allows. My lathe already has a brake but I will be adding a VFD and plan to have the VFD decelerate the spindle fairly rapidly. On most VFDs he deceleration time is programmable so you can do what is most suitable for your lathe and size of work piece. I will likely disconnect the hardware brake shoe and attach the contacts of the brake switch to a VFD input. In general, the "off" or "emergency off (EMO)" circuits should have switches that have normally closed contacts and open when activated. This guards against a loose or broken wire causing the circuit not to work when you most need them. If there is a loose wire the motor won't start and it gets fixed prior to emergency or needing to turn off. Your VFD manual should show specific wiring and programming for the various on/off/EMO switches. They are all similar but . On mine, I plan to have the EMO button still separately activate a contactor on the input of the VFD to get the more complex VFD circuitry out of the equation if there is a true emergency. What VFD do you have?

Of course I thought of something else after posting... An off switch like a micro-switch would be momentary, not a maintained contact. If it is wired into the FWD/REV circuit it may require a relay in the circuit that drops out when the brake is activated and stays off until reset somehow. Otherwise the lathe would stop but could start up again once your foot leaves the brake pedal. Some VFDs can be set up with a "trip" input that does not require such a relay. It is VFD and VFD set-up dependent.
I have finally finished wiring a VFD application on my Harrison M300 13 X 40 lathe. The machine already has safety feature such as E-STOP, Shroud removal interrupter and existing brake limit switch. I bypassed the existing master control relay as well as the existing For/Rev limit switch safety wiring. I added an aluminum plate with 2 limit switches over the existing F/R assembly and made a polyethylene cam that attaches to the existing steel cam with rare earth magnets for the low voltage inputs to the VFD. Also, I added a new ice cube relay to replace the original master control relay. Included in the MCR circuit is a standard stop/start pushbutton combination. Finally, the common F/W for the VFD is wired through normally open contacts in the MCR relay which drop out the VFD when braking or manually stopping with pushbuttons.
A pilot light is wired in the start/stop circuit to indicate that the machine is in the F/W operating condition.
 

Tozguy

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#17
Tozguy, Thank you very much for clearing that up so quickly. So that i understand, what i thought was a solenoid is a switch that kills the motor as soon as the brake if manually activated, correct?

The way i was planning on setting the brake was would be considered a "Deadman kill switch." I was thinking about having a foot pedal bar setup that needs to be stepped on to run but automatically stop the motor and spinning chuck when foot is removed. Being a NOOB i was thinking more about my safety being alone in the shop but haven't made a final decision yet so thanks again for sharing your setup, I Appreciate it.
Correct.

A foot pedal while running set up might limit your normal movement eventually.

Maybe consider a kill switch that is attached to the operator (like on a water scooter) that will give you some freedom of movement but will trigger if you move too far.

In a real panic situation you should have some kind of braking not just power interruption.
 
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