Re: Mariss' Surplus Center Motor - Thanks

Roger,

Thanks. Anything made by PacSci is going to be of excellent quality.

Let's do a little math here:

Assume you are looking to get 100 IPM on the Z axis. A 10 turns/in
screw would have to spin at 1,000 RPM to do that.

1HP is 396,000 in-lbs/min; it would take .303HP or 226W to lift 1,200
lbs at 100 IPM (1,200 lbs * 100 IPM / 396,000 = .303HP). This is easy
work for a 500W motor.

The motor would have a no-load speed of 3,000 RPM at 75V (75V/25V *
1,000RPM = 3,000RPM).

Figure on the motor developing its rated power at 80% of no-load
speed. That would be 2,400 RPM.

The correct reduction ratio would be 2,400 RPM / 1,000 RPM for the
lead-screw. That is a 2.4:1 reduction.

It would require 306 in-oz of torque on a 10 TPI leadscrew to lift
1,200 lbs (in-oz = 8 * lbs / pi * TPI = 8 * 1,200 / 3.14 * 10 = 306
in-oz).

A 2.4:1 reduction would place a 127 in-oz torque on the motor (306 /
2.4 = 127).

The motor's Kt is 33.8 in-oz/Amp. This means the motor would draw
3.77 Amps while lifting 1,200 lbs at 100 IPM (127 in-oz / Kt = 3.77A).

The motor would stay very cool at that current.

Mariss




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "vrsculptor"
<vrsculptor@h...> wrote:

> Mariss,
> Thanks for the tip on the Surplus Center motors. I got two of them.
> They are Pacific Scientific treadmill motors, real well built. They
> spin at about 30 rpm with a single D-cell. They have flat endplates
> with 2 1/4-20 through boltssoend mounting them will be a layup.
>
> I'm planning on using one as a knee motors on my large servo mill.
> If its well enough built to run on a flashlight battery it should
> have no problem with 76 volts at 10 amps. I unfortunately won't

have

> any time until after Thanksgiving to mount an encoder and do real
> testing.
>
> I just hope it can lift a 1,200# table/knee with a 2 or 3:1 belt
> reduction on the motor and a built in 10 turns/inch helical
> gear/ballscrew jack. The knees ways are turcite lined and pretty
> slippery.
>
> Roger S.
>
> Mariss wrote:
> "I stumbled across this motor:
>
> http://www.surpluscenter.com/item.asp?UID=2003070308293941&item=10-
> 1931&catname=electric
>
> It's rated at 4800 RPM at 120VDC with a continuous rated torque of
> 250 in-oz. Working the numbers gives a Kv of 25 volts / 1,000 RPM
> and a Kt of 33.8 in-oz per Amp.
>
> At 72 volts you would get 2,880 RPM and draw 7.4 Amps at its rated
> torque. The power output would be 533 Watts or about .71 HP. I don't
> have this motor nor have I tested it with our G320 drive but it may
> work.
>
> At $24.99 it may be worth a gamble.