Expected Speed of a Linear actuator.

**Metal Demons** · 17th August 2009, 23:24

You want me to buy an actuator, take a hammer drill and some how use the hammer drill motor to power the actuator? And, even if this is what you suggest I do, please could you give me some tips on how to achieve it?

To answer your question, what was meant by using a hammer drill was to remove the motor (and gearbox) and coupling this to a threaded rod. A nut on this threaded rod will travel up and down it when the motor is turned on.

If you look at a nut and bolt being tightened or the insides of a glue stick (a twist one) then you should see what I mean properly. However, for it to work you will need to make sure that only the nut or rod is turning.

http://robowars.org/teams/rotwang/blade/

Take a look at some of these pictures. They contain the same mechanism as above.

Finally, wikipedia is your friend

the animation should help if you still don't get it

http://en.wikipedia.org/wiki/Linear_actuator

Yeah, that's pretty much it. Use the guts of an existing linear actuator combined with a bigger motor in order to give you more speed and lifting force - I'd say pick up a lower ratio (high speed) actuator and just put the new motor on it, junking the attached gearbox. I suggested the cordless hammerdrill motor as they're relatively powerful and commonly used in robots - a Speed 900 or something would be ideal too.

**daliad100** · 18th August 2009, 18:03

That certainly beats my way.

A lot easier than a full diy linear actuator and probably more efficient if there's a ball unit.

Something in this link might apply to your motor change over if you do want to do that.

http://www.instructables.com/id/Cord..._for_about_40/

**aero_storm** · 18th August 2009, 20:47

Aha, you misunderstand me :-

I understand how a ball-screw actuator works. What I don't understand is the switching of the drill and the actuator motor. The screw, that turns inside the threded..um..tube-thingy, is powered by a motor..You want me to substitute this original motor with a hammer drill motor?

Pros?

Cons?

Lastly, I was once warned about using hammer drills by a certain Gary Cairns. Could I not just use a normal drill?

Alex.

**Metal Demons** · 18th August 2009, 21:31

Originally Posted by aero_storm

Aha, you misunderstand me :-

I understand how a ball-screw actuator works. What I don't understand is the switching of the drill and the actuator motor. The screw, that turns inside the threded..um..tube-thingy, is powered by a motor..You want me to substitute this original motor with a hammer drill motor?

Pros?

Cons?

Lastly, I was once warned about using hammer drills by a certain Gary Cairns. Could I not just use a normal drill?

Alex.

Pros - your actuator will be more powerful and (RPM dependent, that's why you want to choose a relatively high speed one to start with) faster moving.

Cons - slightly heavier? takes a bit of effort? Really, for this application, there aren't any.

A hammer drill motor isn't necessary, something like a Speed 700/900, RS775, whatever will do the job just fine - just that a lot of people tend to use Dewalt cordless hammer drill motors in robots for something with a bit more grunt than a drill motor.

A normal drill motor (usually a 550 size) won't be as powerful, which is the problem. His warning was against using a hammerdrill gearbox setup - you'll just be using the motor alone if you go that way. I suggest picking up a suitable motor separately rather than getting a whole drill.

**daliad100** · 18th August 2009, 21:33

Pros:
A pre-built actuator unit (less messing about)
Exchanging the motor makes it more powerful
Could be more efficient (ball screw not acme)

Cons:
Hammer drills are a pain to use the gearbox of it with, they have extra weight for something you no longer need.
Hammer drills have an annoying (in this circumstance) recriprocating thing to provide the hammer action which is not a problem if you are just replacing the motor.
If your actuator has a ball unit (less friction) it needs a brake or it could be pushed back down unlike an acme thread which can't.

A Hammer drill was suggested because it genrally has a more powerful motor than an ordinary drill. If you could get hold of a cheap/broken (motor dead) actuator then replace the motor with that of the hammer drill or morot of your choice.

If you would like a look inside a hammer drill then I could post some pics of the one I pulled apart (the disassembly was pretty much the same as a normal drill.)

Finally, don't use a nu-tool as my drill decides to start smoking once you run it for a minute or two under no load.

**aero_storm** · 20th August 2009, 16:59

Thanks all.

At the moment, I'm veering toward the Just buy the simplest, cheapest one, less will go wrong. Please remember this is my first Robot..

Does anyone know any Actuator venders? It seems that if I had a list of websites that sell actuators, it will be easier to compare Speed, Lifting..um..capacity (?) and price.

I know I'm asking a lot, but...

Alex