Small actuator/piston Design

[Mr RB]

Leadscrews are very difficult to implement. You can't really couple the screw direct to your motor/gearbox shaft as that won't take the high axial loads of 15+ lbs. So then you have to spin the nut with a belt or chain, and have the nut mouted on high axial load (thrust) bearings, which is a pain. Or you mount the screw on thrust bearings and connect the nut to the load, so then you need a system to stop the nut and load spinning but without causing drag.

It's probably best to go for a complete actuator (expensive!) or a cheaper option would be a high torque worm drive gearbox and very short lever (like I said with the windscreen wiper motor suggestion).

 

[superfrog]

While leadscrew is what would be best engineering wise, I must second Mr Black as the implementation is actually quite hard, without proper machining equipment to fit the screw.

If you happen to have a lathe and a mill laying around, I d go for the screw and have a bit of fun with these toys.

Otherwise the wiper motor sounds like as good as it gets, and I believe those come for really cheap. They might even have the end switches in already.

 

[deesnyas]

Im going to draw some pictures of what im wanting and upload em. Its scale will probabaly be a bit off...don't laugh :/

 

[deesnyas]

Here it is Its a real dummy but you get the Idea. Looks Like the shaft isn't supported but the Hex nut will be and it never fully leaves the shaft Its going to be fun finding a small motor. I was looking at the window lifter motors at amequipment and they are 7 inches long-ouch!! I need something SMALL!

 

[superfrog]

it is hard to see on your schematic what actually moves.

Is the screw the translating part or is ti the nut ?

 

[shortbus=]

Hi, can you at least give an idea of what your doing? I understand that your trying to build something to market to people. but to get help on how to do something we have to know what the object is doing.

There a lot of ways to do a lot of things, but more information is needed to help.

Cary

 

[deesnyas]

It's the nut part, the one on the screw that moves up and down. They come anti-backlash but since I'm not looking for precision I think just a regular nut would be sufficient. The part that I'm really looking for is a relatively inexpensive motor that is pretty small ( maybe pancake ) and strong, by tomorrow I'll figure out how strong.

 

[user_88]

The pictures here are something similar to your sketch.

However there is another part that is not shown. A separate piece of angle iron has an acme nut welded to it, and rides in the groove of the piece shown in the picture, as the threaded acme rod that is shown rotates.. ..... I would have included it ... but it seems to have gone missing.

The motor here is a stepper motor, but you could just as well use a DC motor of some sort.

You can see the shaft coupling between the motor shaft and the end of the acme threaded rod.

 

[Mr RB]

Stepper motors are rated for high axial loads, a size 23 (similar to photo) is usually rated for around 5kg to 6kg axial load. That's about 11 lbs.

But DC gearmotors don't have the quality bearings that a size 23 stepper motor has. They can have huge torques but the output shaft of the gearbox is poorly supported and uses crappy bronze bearings, not precision ball bearings.

You need axial load rating on the leadscrew bearings of maybe double the actual 15lb load, to allow for friction and inertia. So you need something rated for >30lb axial load.

Inexpensive pancake motors won't have high axial load ratings, usually in one axial direction they are held together by the rotor permanent magnets and on the other axial direction they have a tiny nylon washer. They are probably the worst possible choice of motor to couple direct to a leadscrew!

Motor choice is going to be dependant on the speed of laod movement, type of load, friction of load, how often it needs to move etc etc. These are all the things that you have not provided any information on!

 

[deesnyas]

SPEED: Needs to transverse the 1 inch distance in less than a second.

LOAD: Actual load is 9 lbs so looking to move 15. The load will be at end of stroke not throughout. I know what friction is, but friction of load?

OPERATION: It is used on need based. Up for a few seconds then down to rest until next use.

 

[Boncuk]

Hi deesnyas,

I suppose the load will be connected (moved) by the nut while the thread is spinning.

Here is a suggestion of a powerful DC-Motor (4.5 to 15V) with various ratio reduction gears.

The torque values in the datasheet are given in g cm. To calculate for nM divide by 10,197.0

I am using a real small motor (dia 12mm, reduction gear 14mm) to drive solar panels the way I described earlier in this thread. Speed is no issue to track the sun, so those small motors and reduction gears are fully sufficient.

Moving an object 1" in less than 1 second depends on rpm and pitch of the thread.

I guess you don't want that actuator heavy and bulky. One motor is about 28US$ and worth an experiment. The motor type is 385.

Alternatively you might use an RB35 (available with different ratio gear boxes as well), made in China, priced approximately US$15.

Regards

Boncuk

 

[shortbus=]

I found you another style of screw actuator. One with a 1.0" stroke at 20pounds lift is only 3.14 inches long when retracted. here is a link;
**broken link removed**

another link on how to select as far as size and pounds of lift rating;
**broken link removed**

You still haven't given any idea about what you really are trying to do or make. There are a lot of other things involved with picking something to move something. Are there any side loads while lifting? How is the "lifter" connected to the load? What are the conditions that it is used in outside or indoors.

I can't speak for everyone, but I don't think anyone is going to swipe your idea. We just want to help.

 

[deesnyas]

I'm not terribly worried about anyone swiping my idea, its just that its not just my idea anymore (NDA).

Okay,

1. no there is no side load besides minimal room for error, the lifter is going to be the load i.e. custom design lifter (nut).

2. standard will be inside environment, but since enclosed outside could be an option for someone i suppose.

Thanks a lot Shortbus! The link is like a quick class, I was gonna ask a bunch of questions as to why stepper motors but ya... Now ill ask just 2.

A.) Not going to ask this one, ill find out if they are comparable to the price of dc motors when I talk to them but

B.) What about the controllers, the article said it works from pulses received, if I only need to instances (max extend and min) wouldn't this greatly reduce the cost?

 

[shortbus=]

B. I don't know about microcontrolers, maybe one can be programed to do this for you. Or the company might sell a package, actuator drive together.

Just did a real quick search and came up with this; Stepper Motor Linear Actuator has integrated chopper drive., Haydon Kerk Motion Sol

 

[PA1]

Try Buy Linear Actuators, Electric Linear Actuators, DC Linear Actuators - Progressive Automations US and Canada. they got lots of different strokes