Author Topic: Removing brakes from Servos  (Read 15477 times)

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Offline m12ax7

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Re: Removing brakes from Servos
« Reply #30 on: February 07, 2012, 11:38:27 am »
I recall (but not too clearly)  that there's been discussion (I THINK it was at Otherpower) about the importance of matching impedance of the servo and the load.  I know that with one of my servo motors much more force (torque) is required to light an automotive lamp (brake light?) than a standard 100w 120vac light.

Many years ago, Zubbly suggested "to me" trying hooking up a power transformer to the servo, for the purpose of better matching impedance's.  I have a couple of 240/440 to 120 (step DOWN) transformers.  I recall that I hooked them up BACKWARDS  using them as step UP transformers,  and noticed a improvement in   torque in verses "apparent" power out.

Yes,  it is obvious that hooking a transformer between the generator (servo motor) and it's load will DECREASE it's overall Efficiency (lost as heat in the transformer)  but overall may increase "system" efficiency by matching drive (whether props/lathe/hand held drill) to servo to load.

I'm posting this in hopes OTHERS will chime in with more actual hands on experience,  as ALL mine is based on OLD memories and only HAND CRANKING my servo.   One should have measurable (valid) data to determine if matching impedance's (servo to load) with a transformer is practical.   Since this idea came from Zubbly it's "my" opinion it's worth  pursuing. 


Offline bvan1941

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Re: Removing brakes from Servos
« Reply #31 on: February 08, 2012, 03:45:04 pm »
m12ax7,
I've been thinking about your post and what amount of torque would be required by the rotor that's developed by the generator trying to supply power to the load. Your right, it can be substantial transmitted to the rotor shaft!

Just thinking, that a load varies the required torque from very high (sometimes an effect almost close to a short) to low as batteries go from a very deep discharge to full charge. Would the " Xformer power dissipation" vary or stay consistent over the power band?

To that, the speed of the wind also limits what torque is potentially available. In my area (Panhandle of Florida), the extra power just may not be there to overcome what's needed at the time, without powerful low speed blades and maybe a transmission to bring the generator into its real power regime.

Chris Olsen has lately been using a combination of a higher stator voltages and a MPPT controller and coming up with pretty impressive wattage from a 3.2M prop! Lots to think about for the medium wind speed band.
Bill

Offline bvan1941

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Re: Removing brakes from Servos
« Reply #32 on: February 10, 2012, 02:19:32 pm »
To all,
Has anyone else had experience with removing Servo brakes (beside Adam), especially other brands other than Fanuc?
I intend to add some pix's to illustrate what I've documented so far on my Fanuc Servo project.

I hope some others will share their experiences here too.
Bill

Offline m12ax7

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Re: Removing brakes from Servos
« Reply #33 on: February 10, 2012, 08:07:44 pm »
Hello..

Though I really DON'T want to admit it,  I did "defeat" the brake on the Kollmorgen servo I have.   I say "defeated" because I did not remove it from the rotor.  I'll point out that when I rescued it from the junk barrel the rotor had already been removed from the stator.   The brake is pressed on, and I did not have the equipment nor access to it,  So I did what most everyone would call a "hack job" on it.    The face of the brake is (when assembled) bolted to the front end bell,  so all I did was to cut the wires to the brake coil and used a ......yes I'll say it...  a angle GRINDER and ground down the surface of the brake.   When I reinstalled the rotor I just plugged the holes that were used to bolt the brake assembly.   

Now when you spin the shaft,  the brake (inside, still pressed on the rotor) spins with the shaft.    I don't believe it adds any extra resistance (torque) to  spin the shaft.

IT WASN'T PRETTY!   but the fact is,  it worked fine. 
I did wrap the rotor/magnets with painters tape to keep it free of grinding dust.

Here (if this works)  is a side view of the rotor with the brake on the left side (front of rotor)  and the face I ground down is facing the output shaft (perpendicular to camera view).

http://www.otherpower.com/images/scimages/4822/Kollmorgen_rotor_1422.jpg


Offline bvan1941

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Re: Removing brakes from Servos
« Reply #34 on: February 10, 2012, 08:48:37 pm »
m12ax7,
Boy, I think taking the brake off that Servo (if it were togetherwhen you started), would have been much harder than the Fanuc. I would in retrospect recommend A Fanuc vice Kollmorgan.
Removing the brake on mine was much easier (rotor stayed in place on the front shell), and didn't have to worry about losing any magnetizing ability and therefore possibly ruining a potential "good generator."

Glad It worked out. Thanks for contributing.
Bill

Offline birdhouse

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Re: Removing brakes from Servos
« Reply #35 on: February 10, 2012, 10:49:20 pm »
12ax7-
nothing wrong with cutting bits out with a grinder.  if it worked/negates the brake, it was a success!  i personally love the brute cutting force of a 4" angle grinder with a 5" cut off wheel on it! 

bill-
when you gonna get us photo's of the servo surgery?

adam

Offline m12ax7

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Re: Removing brakes from Servos
« Reply #36 on: February 10, 2012, 10:58:15 pm »
bvan1941

If there would have been a Fanuc laying in the junk barrel,  I'd have that here too.   But like cards... sometimes you just have to do with what you're dealt!

As I said before,  this servo,  when shorting any two or all three of the power leads GREATLY increases the 'back' torque (turning rotor by hand), with all three leads shorted you can hardly turn the shaft.   I can NOT imagine what torque would be needed if the neo magnets were any stronger than they are now.   I have a matched pair of smaller Allen Bradly servos,  one I've had the rotor out (for at least two days) and the other has never been taken apart.   Shorting the leads of either motor gives the  SAME amount of back torque,  the only way you/I can tell which one has been taken apart is the scribe marks I put on the stator/end bells.

Again,  I know that removing rotors of servo motors is suppose to ruin/weaken the magnets,  just that  "I'VE"  never seen it to be true.   Also,  I have NEVER worked/seen a Fanuc so maybe there's something very different about them.

I'd like to mention that the magnets on the rotor are pretty small.  I'd guess (it's been a two years since I've had it apart) the magnets are about   3/16 X 5/16 X 5/8.   Of course,  there's lots of them.  *L*

Offline bvan1941

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Re: Removing brakes from Servos
« Reply #37 on: February 10, 2012, 11:26:08 pm »
m12ax7 and Birhouse,

 m12ax7-- I too tried shorting just two leads and could hardly turn the rotor by hand, I can imagine shorting all # leads!
About your Servos,I meant that the Fanuc wasn't hard to remove the break assy. It was screwed to a mount on the back end of the case. On yours, It just seemed to be more difficult to do. Your Servo is as good if not better than the Fanucs -- If brand name and reputation has any meaning. Sorry if I cast any negative connotation on kollmorgan Servos. Did you get the output you expected ?

Birdhouse-- My motor hasn't got back from the machine shop yet. The boss asked me to leave it with him until he can show his machinist what this can do as a generator. His thought is to hook one like this to an engine and make a mobile generator for his truck working in the field!  Now there's people looking to use Servos here in "redneck City"  "It's all your fault" LOL.  He even asked me for this Forum website!!

 I'm getting my camera ready--hopefully this week to post some pixs.

Bill

Offline bvan1941

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Re: Removing brakes from Servos
« Reply #38 on: February 26, 2012, 05:27:34 pm »
To all,
Trying to document my FANUC - A06 brake removal process with some followup pix's as promised. If these pix's aren't good/ big enough please advise and I will redo them. Please look at "Birdhouse's" picture (on an earlier page here) showing the Servo split apart, It will fill in the gap in my explanation.  I'll try and explain my pix's in order :

1- First pix is just to show approx size of the Servo and blade/s I'm going to try with this Servo.  The 9.2' Rotor is an S-809 Foil.

2- The side view is trying to show where I split the case apart, Should show up as a silver line on side of servo not quite halfway back from front edge of case.

3- The backcover is to show how I cut the (2) brake control wires, off along with a "dozen" other control wires on the top of the back cover.

4- This pix shows how the (3) brake parts look as they sit screwed over a magnet coil in the back half of the case after splitting the two halves apart. What is not shown here is approximately (6) little springs and spacers used to push this whole assy. forward engaging a gear as part on the armature shaft (located on the front half of the case). This is what "locks up" the servo when no power is applied to the (2) wires on magnet coil, going to the tiny socket on the red backcover. When this Servo is used normally in an industrial setting , power is applied to the brake's magnet coil retracting this assy. back from the metal gear on the armature and the motor spins freely in either direction!

5/6- A pix of the (3) parts making up the "brake assy." and The dark fiber center piece with matching gear shape and (2) metal plates that are attracted by the manetic actuated coil mounted in the back half of the case.

7- This is the round aluminum "plate" holding the rear bearing that centers the armature shaft, and the tachometer assembly. It also seals the back end of the motor from the elements. It is held in place with hex head screws ( not necessary to be removed for this process). The (2) yellow brake wires from the magnetic coil) are taped for now(could be cut off) .

8- The red back cover is shown lying on its back, but is screwed to the "back plate" and is removed first to DETACH THE TACH ASSEMBLY BEFORE SPLITTING THE CASES APART!! Remove the (3) screws holding this tachometer assy. to the plate and armature shaft.

Gents, this is my first attempt at multiple pix posting along with an explanation of my project. Hope it helps someone. I'll try and answer any other questions requested.
Bill

Offline bvan1941

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Re: Removing brakes from Servos
« Reply #39 on: February 26, 2012, 05:32:19 pm »
PS:  I KNOW---- I KNOW The pix's are from "down under"

             LOL
Bill

Offline wilfor03

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Re: Removing brakes from Servos
« Reply #40 on: February 26, 2012, 08:02:22 pm »
Hey Bill....

That servo brake in the pix looks just like the ones I took out of my Omron-600w servo (in the picture below).

I really like that thing sitting up there on my 25' tower making power for me (when the wind blows here....not real often).

Finally got to see it "start" to furl a couple days ago, during one hell of wind through here. It was quite a show for me.

Thrill of a life time, eh?

Keep up the good work and keep posting your progress as its still very interesting for us, too! You're getting closer every day, Bud!

Bill


Offline bvan1941

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Re: Removing brakes from Servos
« Reply #41 on: February 26, 2012, 09:59:46 pm »
Thanks Bill, I read and enjoyed your project very much!
I hope some of the guys deciding to try a servo will find this a help. I know Adam's (Birdhouse) split Servo pix helped (backed up with his encouragement to keep at it) and gave me a little more comfort doing something like that for the first time. Your Omron Servo,
Mike (97 fishmt) said he has used them, I think. Believe he's happy with their performance too!

By by the way, notice you using PVC blades. Have you been happy with their performance? Nice hub too! Like that you painted yours, it should help the UV problem. I made some for my 1st. project 2.5 years ago and still running. Will inspect and let you know the results later on. Going to use a 9.2' rotor on this Fanuc motor.
 People here thinks me "strange" but, interesting with my hobby.
Bill




Offline wilfor03

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Re: Removing brakes from Servos
« Reply #42 on: February 27, 2012, 08:08:07 am »

By by the way, notice you using PVC blades. Have you been happy with their performance? Nice hub too! Like that you painted yours, it should help the UV problem. I made some for my 1st. project 2.5 years ago and still running. Will inspect and let you know the results later on. Going to use a 9.2' rotor on this Fanuc motor.
 People here thinks me "strange" but, interesting with my hobby.
Bill

Bill...
Yup, love the PVC blades I got on there. They're 37" each, and I want to chop em down a couple inches for a bit more speed (more power).

I like to use PVC first, and figure out what size seems to run best here in my area with my winds and gennys, then, plan on carving (chainsaw) some wooden ones

for the permanent mount. PVC is so easy to work with and fast to get me into the ball park on what works with whatever it is mounted to.

Yea, that's a real hum-dinger for a hub, eh? That too, is just for the PVC blades temporarily. I use 2- 7 1/4" (Cheap!) saw blades from the Tool Shed here in town.

They set me back a whole $2.00 each. Woo-whoooo!!

I plan on using 1/4" flat steel hubs once I find what works good. I know the feeling about people thinking you strange and such. But, when the power grid goes down

here, I just flip a couple switches, and continue on with normal lifestyle, while they all do without until they get out their gas generators and fire em up!! I keep my

gas generator in reserve until the solar panels no longer put out.

Well, Bill, keep on keepin on....you're doin good!!

Bill

Offline bvan1941

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Re: Removing brakes from Servos
« Reply #43 on: February 27, 2012, 01:15:19 pm »
Bill,
I initially made my blades like yours and was constantly making blades because of "flexing" and to adjust rpms for less than desirable winds here. What I did to improve speed was come off the hub with flat bar steel arm about half the radius and mount blades along that arm using a wide spacing to attach the pvc blades. I used 4" pvc I had for this experiment. This significantly reduced the "flexing" of the pvc in strong winds and destroying the blades from pole strikes due to blade flex. So when you look at my rotor, it looks like only the outer half of the rotor has blades.
(It's based on theory that the inner half of blade does little work) It seems to be true for me. They seem to start around 4-5 mph(guess) and speed up quickly!  Highest winds estimated-- 35-40 mph. By the way the blades are silent.
Bill

Offline wilfor03

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Re: Removing brakes from Servos
« Reply #44 on: February 27, 2012, 01:50:07 pm »
Bill,
I initially made my blades like yours and was constantly making blades because of "flexing" and to adjust rpms for less than desirable winds here. What I did to improve speed was come off the hub with flat bar steel arm about half the radius and mount blades along that arm using a wide spacing to attach the pvc blades. I used 4" pvc I had for this experiment. This significantly reduced the "flexing" of the pvc in strong winds and destroying the blades from pole strikes due to blade flex. So when you look at my rotor, it looks like only the outer half of the rotor has blades.
(It's based on theory that the inner half of blade does little work) It seems to be true for me. They seem to start around 4-5 mph(guess) and speed up quickly!  Highest winds estimated-- 35-40 mph. By the way the blades are silent.
Bill

Hey Bill.....
Must be sorta dumb here....can't picture in my mind what you're doing? Are you keeping your normal hub and attaching flat stock to it (expanding the radius) and then

mounting your PVC blades to it? Wouldn't happen to have a picture of it, would ya? Mine are nice and noisy when they start hitting the 3-6 amp mark. When I hear em

starting to roar, I high tail it out to the workshop to see what the ammeter is showing (that's how I get me exercise at this age!!).  ;D  Appreciate the info, Bill.

Bill