Re: Bridgeport servo motors

Scott,
What are you using, Ameteks? Have them running yet? Anyone else using
these on a BOSS & getting decent performance out of them?

-Brady

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
<polaraligned@o...> wrote:

>
> These motors were custom made for HP. They are brand new. They
> even came in the brand new packaging. I guess in your situation
> you are looking for a set up that will "bolt in" for your Boss.
> I know I can't run these 1:1, but I am just trying to figure out
> what ratio I need. I'd like to do the conversion right the first
> time. I am very interested to see how your motors work out.
> I did check them out a couple of weeks ago.
>
> Good luck,
> Scott
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "braidmeister"
> <braidmeister@y...> wrote:
> >
> > Scott,
> > The Ametek's look very appealing initially, but I don't like them

for

> > a Bridgeport for several reasons:
> >
> > 1. Many of the Ametek ones don't have a 2" or longer shaft on

them.

> > You need 2" or better if you want to bolt right up to a BOSS

factory

> > belt drive.
> >
> > 2. I don't think that they have enough power to run 1:1, and the
> > highest RPM I have seen them rated to is about 2000 RPM or so. So

if

> > you did gear them down to 2:1, you might see a max rapid rate of

150

> > if they can pull the load.
> >
> > 3. They are used...not sure the condition of them, but they were
> > designed for a reel to reel tape drive...
> >
> > I don't have any direct experience with these motors and

initially

> > was looking at them. Surplus center sells a few variations of

them.

> > The 36v model has a 5/8" X 2" shaft that will bolt right up to

the

> > BPs drive belts.
> >
> > I just bought 3 of these puppies:
> > http://www.surpluscenter.com/item.asp?

UID=2005020410354708&item=10-

> > 1802&catname=electric
> >
> > I chose them because they will definately have enough power for

the

> > retrofit running 1:1. I don't plan on running them full voltage,

so

> > my rapids will be a little slower...but still capable of over 400

IPM

> > in theory. I'm going to shoot for the 150-200 IPM range and be

happy

> > with that.
> >
> > The reasons I chose them are they are cheap @ $80 ea, they have 2
> > 5/8" shafts that are 2.5" long, and they are 9.125" long at the

body

> > so they will fit between the Y axis and the knee. I will have to
> > shorten the shaft on the Y...but it sure beats trying to EXTEND a
> > shaft, which is the case with the treadmill motors. So, aside

from

> > shortening the rear shaft and making some type of mounting/face
> > plate, these are a bolt-in deal. I really didn't want to fool

around

> > with extending shafts, drilling shafts for encoders or coming up

with

> > some type of external belt-drive because the motor was too long

etc.

> > Belt drives are not cheap...
> >
> > I haven't decided on a servo drive yet. I am leaning towards the
> > Rutex though because it has more features that the

Gecko...although

> > wiring is a bit more complicated.
> >
> > Hope that helps,
> > -Brady
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
> > <polaraligned@o...> wrote:
> > >
> > >
> > > There has to be a difference between a new servo motor at $800+

and

> > a
> > > brand (not surplus) treadmill motor at $100+.
> > > I have servo motors that I paid, what some would say "dearly"

for,

> > > from a dealer on e-bay. He has sold hundreds of these surplus
> > motors
> > > and has excellent feedback. He states that as many as half

have

> > been
> > > used sucessfully on Bridgeport retrofits. Of course, he has an
> > > interest in selling motors so....
> > >
> > > Here are the motor specs:
> > >
> > > Torque constant: 44oz-in/amp
> > > Voltage constant: 32.5v/1000 rmp
> > > Peak torque: 600 oz-in, or 37.5 in-lb
> > > Nominal voltage: 40vdc
> > > Maximum voltage: 60vdc
> > > Demagnitization current: >20amps
> > > Terminal resistance 2.60 ohm
> > > Max rpm at 50vdc is about 1200 rpm
> > > No-load current <.51 amp
> > > armature inertia .09oz-in-sec^2
> > > 4 bolt holes in face for easy mounting.
> > >
> > > They came with 1000 CPR Renco encoders pre-mounted. I may move
> > > the encoder to the leadscrew though. The seller states that
> > > these are the largest servo's that a Gecko will drive. The

motor

> > > also has a heavy duty front ball bearing. At $150 per motor

with

> > > encoder installed, I find them to be quite reasonably priced
> > > considering they are "real" servo motors.
> > >
> > > The big question, If I decide to use these motors, is what my
> > > reduction ration will be. I need to trade off between torque

and

> > > speed, and the BIG unknown is what torque is REALLY needed to
> > > drive my Bridgeport. I would rather err with a higher reduction
> > > ratio than find myself without enough torque.
> > > If I go with a 3:1 ratio and triple my torque I will get 80

inch per

> > > minute rapids. More than an inch per second SEEMS plenty for

me.

> > Why
> > > do people need such fast rapids on a mill? What do you think

about

> > > even a 4:1 reduction? Will I regret it later? Do I ask too

many

> > > questions? I mostly mill small parts, say 6" on each side or

less.

> > >
> > > A fellow CNC'er here used these same motors on a Rong Fu mill in
> > > direct drive and said they worked, but were at their limit. My

3:1

> > > reduction will triple the torque, and after all, the only forces
> > > different between my Bridgeport and the Rong Fu is the dead load
> > > of the larger table. (The Rong Fu leadscrew is also finer

at .1" per

> > > revolution). The cutting forces should be identical.
> > > The BIG question is will I produce enough power with these

motors

> > > to drive my Bridgeport. What do you think?
> > >
> > > Scott