gearbox torque?!?!? 1

[bauboya]

Hi, I don't know much about mechanics and I'm trying to build a mechanism to drive a set of syringes, and I need to buy a gearbox motor to drive the syringe shaft forward and back. the syringe needs to be driven 70mm, and i'm going to attach a rack and gear to the motor to get this motion. however, because of the hydraulics, it actually requires quite a bit of force, and i don't know what gearbox motor will be strong enough to drive it. i didn't know how to measure how much force i need so i put weights on the shaft and it needs 2.5kg to drive forward at a good speed. (it doesn't have to be incredibly fast but i don't want it to be terribly slow either).

could anyone recommend a motor that will be strong enough to drive it at a good pace??
or tell me what information and numbers to look for in the data sheet??

thanks so much!!

 

[BobM3]

For starters, you're going to have to come up with a number for the required speed. Maybe 1"/sec? Faster?. Having that velocity and the force will allow you to calculate the power you need to deliver to your load. From there you work backwords to get the required motor power.

 

[bauboya]

ok...so if the speed is 10mm/sec?? what do i do next?

 

[PeterCharles]

In metric units =

1 Watt = 1 Newton meter/second

So you've got 2.5 * 9.81 Newtons and 10 / 1000 meters/second

Which gives you

2.5*9.81*10/1000 Watts

 

[BobM3]

Does it have to be a gear/rack/gearbox/electric motor? You can buy electric linear actuators like this:

http://www.mcmaster.com/#linear-actuators/=20pezx

I'm sure there are smaller ones available.

 

[bauboya]

a linear actuator would be ideal, however i can't seem to find one that is strong enough to drive that weight (2.5kg) the distance of 70mm at the speed mentioned earlier.
(at a relatively cheap price that is) if you know where i could find such a part please let me know!

 

[Clyde38]

Try a lead screw for the linear motion (see attached spread sheet). Find a lead screw manufacturer to help with the selection and or find a motor manufacturer to help with lead screw, motor, and gear head if necessary.

See notes in spread sheet.

[link

http://www.linkedin.com/in/clydehancock

]

[/url]

 

[automatic2]

I had worked with a 'syringe' dispenser that used pnuematic cylinders as the 'syringes', driven by a screw. The drive worked relatively well (excepting overdrive conditions). In the end we scrapped the whole thing and went with a multi tube peristaltic. Repeatability was acceptable and maintenance (tube replacement) was easy for the end user.

 

[benta]

These might be too big/powerful, but take a look anyway:

http://www.linak-us.com/

Benta.

 

[TheRocketScientist]

Here's one version of a peristaltic pump:

http://www.ledebuhr.net/pumps/index.php?gclid=CPHp5v7Q35oCFQoMDQod608DzQ

you might use a small gearmotor and a crankshaft and rod to move the syringe plunger. Pretty much any available small gearmotor would do that task. Syringe speed would vary with position a bit.

You could instead use such a gearmotor to drive a lead screw- McMaster offers Acme thread lead screws and mating nuts I'm sure. These gearmotors are pretty beasty, they drive a load of 100's or 1000's of lbs- and surely smaller such units are made:

http://www.aerotech.us/productmanuals/qm1027.pdf

or

http://74.125.93.132/search?q=cache:hyGTjuiaAi4J:

http://www.aerotech.us/productmanuals/qm1027.pdf+aerotech+gearmotor&cd=3&hl=en&ct=clnk&gl=us

Have you considered just using a small air cylinder to move the syringe, and a simple controller to apply the air to extend or retract the cylinder as needed? Presuming you have compressed air available of course.

I doubt that solenoids as listed above would work well, because the force varies greatly with the position of its core rod.