PDA

View Full Version : Looking for engaging techniques



Mike Amick
12-24-2013, 01:22 AM
Love motorizing things. Just day dreaming about adding something like a
power feed to my mill knee. My problem is thinking up ways to engage
disengage the motor so that I can use the manual handle when I want to.

So I am asking if anyone knows of a book or other resource that suggest or
describes different techniques of engaging a motor .. like the pic below of my
X power feed which is super slick .. but .. its hard to find motor gear boxes with
holes in them for shafts.

How about a cog pulley type thing .. where a lever tightens the belt for engage ..
or really loosens it for free wheeling ? Or something that pushes two gear
together etc etc ... sorry is this is too beginerish ... lol

http://www.mikeamick.com/misc/table_580.JPG

darryl
12-24-2013, 02:07 AM
I repurposed a couple of sattelite dish actuators to use as power feeds on my mill. The gear train has a large final gear, so I made a flanged boss to mount onto the lead screw, then the gear rides on the boss. I also changed to a ball bearing to center the lead screw and added a pair of thrust bearings for it as well. The gear is bored out to fit the boss closely, yet allow it to freewheel. The positioning of the boss on the lead screw sets the pre-load on the thrust bearings.

The housing for the gearbox is machined out so it can slip over the lead screw and mount to the endplate holding the lead screw ball bearing. The output gear can then rotate freely on its boss, leaving the leadscrew motionless, or if I pinch the gear to the flange on the boss, it turns the lead screw.

The handle is made with a flange on it as well, and it is keyed to the lead screw. I tapped a hole in the end of the lead screw, and by tightening a bolt it pinches the flanged handle towards the gear. All I need is about 1/2 turn of the bolt to go from manual to motor-driven, so even in manual mode the handle never feels loose.

This has worked flawlessly for years now. My drive system is a little crude, being little more than a couple of voltage levels to run the motors. Basically I have slower and faster. I really would like to have full control of the speed. I've made provisions for that- just never got around to completing the electronics.

I should add- this is just a friction drive, so it is limited in torque transfer capability. I've never had a problem with this- if it slips I just tighten the bolt a bit more. I usually don't need to, but I can certainly see where a positive engagement would be prudent. You may need a much higher torque for running a knee up and down.

The Artful Bodger
12-24-2013, 02:32 AM
HI, this is one of my first machining attempts but it works well and was easy enough to do. It is an 'X' power feed for my small knee mill.

http://farm4.staticflickr.com/3699/11527368633_a4a6efb330_z.jpg

The engaging is done by the dog clutch which is operated by pulling the handle in or out. The worm and peg wheel was easy to make and gives a very high reduction ratio for the motor which is a DC motor from an old main frame computer's tape drive but really any DC motor that can be run slowly would do the trick. I use a basic pulse width modulated variable speed control. I hope this gives you some ideas.

John

Black Forest
12-24-2013, 09:34 AM
Drop down on one knee and pop the question! Have a suitable ring in hand. Preferably made in your home shop.

Mike Amick
12-24-2013, 05:06 PM
I repurposed a couple of sattelite dish actuators to use as power feeds on my mill. The gear train has a large final gear, so I made a flanged boss to mount onto the lead screw, then the gear rides on the boss. I also changed to a ball bearing to center the lead screw and added a pair of thrust bearings for it as well. The gear is bored out to fit the boss closely, yet allow it to freewheel. The positioning of the boss on the lead screw sets the pre-load on the thrust bearings.

The handle is made with a flange on it as well, and it is keyed to the lead screw. I tapped a hole in the end of the lead screw, and by tightening a bolt it pinches the flanged handle towards the gear. All I need is about 1/2 turn of the bolt to go from manual to motor-driven, so even in manual mode the handle never feels loose.



Afraid I'm not experienced enough to picture this in my head. But it sounds sort
of like a traditional clutch where friction provides the movement.



HI, this is one of my first machining attempts but it works well and was easy enough to do. It is an 'X' power feed for my small knee mill.

The engaging is done by the dog clutch which is operated by pulling the handle in or out. The worm and peg wheel was easy to make and gives a very high reduction ratio for the motor

John

See .. there ya go. I think I need to read about dog clutches. Its new term
to me and I think it is key to a lot of go/no go mechanisms.


Drop down on one knee and pop the question! Have a suitable ring in hand. Preferably made in your home shop.

Whooooo there. Don't even want to know without a disengage strategy.


But that brings up part of the problem. I don't even know what to ask to do
an intelligent google search. If I put in clutch systems .. it not really the type of
info that I am after. If I ask for engaging techniques ... Black Forrest has
me on my knees ! .. But this new term " dog clutch" may yield something.

Thanks
Mike A

topct
12-24-2013, 05:44 PM
But this new term " dog clutch" may yield something.

Thanks
Mike A

Google images has several opinions on the subject.

darryl
12-24-2013, 09:18 PM
While the engagement ring could be made from silver, gold, and bits of hard cutting materials such as diamond, a disengagement ring could be made from 12L14. In the event that the engagement does not proceed to the state called 'welding' (sp?) then the engagement ring shall be removed and the disengagement ring shall take its place. This change should be made only when the bearing shaft is not in motion. After discovering this part swap, the 'shafter' or 'shaftee' would have little reason to suggest a continuation of the engagement. The action would be very positive, though it's possible a death could result.

:)

Yes, the device I described is a friction clutch, with no positive engagement of teeth, etc. I have no pictures of it.

Mike Amick
12-24-2013, 10:03 PM
Holly crap !!! It took me to the very end of your entire description to realize that it was
a joke .. I kept thinking .. oh no another new term "engagement ring" and "disengagement ring"

lol

Mike A

WilsonT
12-26-2013, 12:12 AM
I wish I had the ability to draw what I envision. What I see in my mind would be the shaft that turns to raise/lower the knee would be cut into two parts. Each part would have splines cut into it and a collar with matching splines on it could be used to join them such that the handle could be used to raise/lower the knee. The collar would also have a dog clutch on it such that when it it was moved into engagement with the gear that would motorize the knee, the handle would be disengaged and vice versa. Thus, it would allow you to use the motor to raise/lower the knee without danger of hurting yourself.

Mike Amick
12-26-2013, 04:14 AM
Wilson .. I think your description is the essence of a dog clutch ..

Now that I know what a dog clutch is .. I'm finding all kinds of things. One thing I found
for powering mill axis's is wheelchair motors. They are pretty cheap, a nice size, about
the right speed .. and the biggest thing !!!! is they have a freewheel lever .. meaning they
have engage disengage built right into them !! I want to get one and play with it.

Mike A

Mike Amick
12-26-2013, 04:15 AM
Wilson .. I think your description is the essence of a dog clutch ..

Now that I know what a dog clutch is .. I'm finding all kinds of things. One thing I found
for powering mill axis's is wheelchair motors. They are pretty cheap, a nice size, about
the right speed .. and the biggest thing !!!! is they have a freewheel lever .. meaning they
have engage disengage built right into them !! I want to get one and play with it.

Mike A

Rosco-P
12-26-2013, 11:54 AM
Another consideration of any power feed design is disengaging the handwheel when the power feed is in use. Getting smacked by the spinner of a rapidly turning handwheel in the leg or the nads is a real attention getter.

lakeside53
12-26-2013, 12:08 PM
MY CNC avoids that by having folding handles on the hand-wheels. You only forget once or twice...

Mike Amick
12-26-2013, 01:37 PM
Another consideration of any power feed design is disengaging the handwheel when the power feed is in use. Getting smacked by the spinner of a rapidly turning handwheel in the leg or the nads is a real attention getter.

hmmm yea .. the other axis's I would say "not that worried" but when it comes to the knee, that handle would be a weapon.

thanks for the heads up
Mike A

becksmachine
12-26-2013, 01:46 PM
A rather quick and dirty "dog clutch" can be made using the two halves of a jaw type flexible coupling. Just leave out the rubber spider and mount one of the halves so that it can be manually positioned to either engage or dis-engage the teeth on the opposing half.

Probably doesn't work very well if it needs to be dis-engaged under heavy load. But with light loads it has worked well for me.

Dave

Mike Amick
12-26-2013, 04:00 PM
wow .. thats what I am talking about ..

digging a little I see you mean something like this.
http://www.ebay.com/itm/1Pcs-22mm-x-24mm-D40mm-L66mm-Motor-Flexible-Plum-Coupling-Shaft-Coupler-/131054424254?pt=BI_Heavy_Equipment_Parts&hash=item1e8373d0be

thats great !

KJ1I
12-26-2013, 05:02 PM
Mike,

Check your PM.

Kj

boslab
12-26-2013, 08:00 PM
How about an electromagnetic clutch motor, got one off a roller shutter door
http://www2.mikipulley.co.jp/en/product/category.php?id=pcb
It was dc 24 volt and holds like bronchitis!, wont let go, at least when i get it
Mark

Mike Amick
12-26-2013, 08:34 PM
niiiice ... Boslab .. but something tells me that some of those cost as much as mill is worth .. !!

jim davies
12-26-2013, 11:25 PM
Every time I see a Chevy Cobalt electric motor off the PS rack I think
about what a great knee lift motor it would be. Must be a zillion or so around
now.