Simple Linear Motion? 1

[jdpjhu]

I'm building a bench top reactor setup and I'd like to have my reactors oscillate up and down in a temperature bath. Does anyone know, specifically, what I can use that's simple/inexpensive to set up and will create continuous push/pull motion (mounted vertically)?

I need a stroke of about 5.5" and a slow speed (less than 1"/second). The load I have is about 5-6 lbs, not much. I've looked at several things - linear slides, motors, actuators - but I'm just not familiar enough to know what to choose.

I'd appreciate any help along the lines of what exactly I need to look for, where, how to configure, etc. if anyone can offer it.

Thanks!

 

[ivymike]

there was another post here recently, to do with converting rotational to linear motion, and it may be of use to you...

 

[saxon]

jdpjhu, Using a rotary to linear actuator is one approach. Have you thought of using a pneumatic cylinder operated by a directional control valve, controlled by a timer?

Hope this helps.
saxon

 

[MadMango]

I agree that given the info you supplied (limited) that pneumatics may be the way to go.

Ray Reynolds
"Computers in the future may weigh no more than 1.5 tons."
Popular Mechanics, forecasting the relentless march of science, 1949
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[MintJulep]

I'd also vote for pneumatic cylinder. Simple limit switch on each end to flop the control valve the other way. A few needle valves for speed control.

 

[aspearin1]

I would take my lessons from the carnival geniuses, and examine how in the world they made those plastic horses go up and down. Bent shafts. At the hinge, there is a lot of circular motion, but where suspended (if fixtured right) the motion can be vertical.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[rmw]

Because your application requires slow speed, it is ready made for an electric actuator. Check

http://www.jordancontrols.com

for a selection of electric linears that will do what you want to do.

rmw

 

[sacem1]

jdpjhu:

If we make a quick calc of your power requierements we find:

Load: 6 lbs
Speed: 1"/sec = 60"/min = 5'/min or 5 fpm

Then you requiere: 6 lbs x 5 fpm = 30 lb-ft/min

Since 1 HP = 33,000 lb-ft/min then we have:

30 ft-lb/min / 33,000 lb-ft/min = 1/1000 HP net power use so you will find that almost the smalest motor-reducer combination that turns a crank with 2.75" excentricity will do the work for you.

As a crank that gives you the 5.5" stroke will move 11" in one revolution (5.5" down + 5.5" up) and you want a linear speed of 1"/sec then you have 11 sec/rev which gives you about 5.5 RPM output speed for your reducer with an input power of 1/1000 HP.

Since the power involved is so little you might get along with a simple disk attached to the output shaft of the reducer a journal drilled and tapped to the disk (a simple 3/8" NC bolt should do) with a rod that should be about 16" long and a 6" slider so the swinging motion of the rod is turned into a simple linear motion. Any small shop should have the facilities for making such a device and should be cheap also.

Cheers

SACEM1

 

[jdpjhu]

Thanks to all for replying! I'm glad something seemed to stand out as the majority choice - pneumatics - and have since looked into it and it seems just right. Appreciate your time and help.

Regards,
JP

 

[nbucska]

I suggest a simple excenter driven by belt

<nbucska@pcperipherals DOT com> subj: eng-tips

 

[nbucska]

Aspearin:
It is a simple ___--___ crank.

<nbucska@pcperipherals DOT com> subj: eng-tips

 

[m777182]

You could as well fix your reactor and provide a pipe ring around its body equiped with three or more nozzles directed towards the reactor. Then you can spray your cold/hot water periodically by means of a on/off valve over the reactor surface. Heat transfer coefficient will be much better and the setup is simpler.
m777182