Expected Speed of a Linear actuator.

[aero_storm]

No Re-introductions here - I posted a short one in the General section;

So, what kind of speed would the actuator of a typical lifter operate ate? And does it change anything that the Robot will be based more on Speed and power, and that the actuator would be rather secondary?

I currently have my eye on this:

http://www.firgelliauto.com/COMPACT%20A ... e%2005.pdf

However, as you will see, there are four different models to choose from. Any help as to which one, or even if the four of them are suitable for a Robot, would be highly appreciated.

Thanks all,

Alex R

P.S Hi again.

[Metal Demons]

Re: Expected Speed of a Linear actuator.

It varies - the information's all available on the datasheet. Which actuator will or will not be suitable for a lifter I can't tell you, as that depends entirely on the actual design of your mechanism as to what input force is required to apply the required force to lift their robot. Work out what kind of shape you're aiming at, then what the mechanism will be to apply the required motion (whether a 4 bar mechanism or a simple hinged lifter, or whatever else) - then how much force you need to apply where in order to lift them.

Overvolting your lifter will increase speed significantly though, which you can get away with for low duty cycles.

[aero_storm]

Re: Expected Speed of a Linear actuator.

It is supposed to be a simple hinged lifter. The plan was to over-volt it, but I was warned against it on my last stint in these forums.

To the original question; Can anyone give me the speeds of any linear actuator they use, or any that they know is in use, so I can get an idea for the typical speed. Or, I suppose to put the direct question at you, is 2.8 cm/s too slow, because it seems it to me.

Alex R.

[Metal Demons]

Re: Expected Speed of a Linear actuator.

I'd want to shoot for something significantly more than that - I would aim to have the system fully extend in ~1 sec in order to make sure you can actually get hold of them before they get off the lifter.

[RogueTwoRobots]

Re: Expected Speed of a Linear actuator.

For an actuator, 2.8cm/s is a pretty decent speed. I've got one that moves at 3.5mm/s, so by comparison, I'd be happy with 2.8cm/s. If the actuator is quite highly rated force-wise, you could configure your system with a ratio in such a way that the lifter moves a large degree for a relatively small movement of the actuator.

If you want something much faster but still want a high level of force, you're gonna be looking at lots of £££ on an extremely high-quality actuator, or custom-built system. The time Nick mentions of ~1 sec isn't really viable with off-the-shelf actuators. It's certainly achievable for a lifter; Storm 2's lifting arm was devilishly fast for an electric system, but no actuator in sight there - there you're talking about a Magmotor running through a custom-made gearbox setup.

Bear in mind also that your lifter doesn't have to be fast to be effective. If your lifting arm is under a robot and moves, say, about 10-20% of its total travelling distance, the chances are your opponent's wheels will be off the ground and you'll have broken their traction. They're now at your mercy (until you lower your lifter or they fall off) to do with them as you please
So if your lifter takes 10 seconds to go from down to fully up, that doesn't mean it'll take you 10 seconds to lift your opponent up to immobilise them. You could probably manage that in 1-2 seconds

[Metal Demons]

Re: Expected Speed of a Linear actuator.

If you want something much faster but still want a high level of force, you're gonna be looking at lots of £££ on an extremely high-quality actuator, or custom-built system. The time Nick mentions of ~1 sec isn't really viable with off-the-shelf actuators. It's certainly achievable for a lifter; Storm 2's lifting arm was devilishly fast for an electric system, but no actuator in sight there - there you're talking about a Magmotor running through a custom-made gearbox setup.

Cheapest way to do it right is to use the mechanism from an existing actuator (Acme thread or ideally ball-screw) driven off a more powerful motor: the dinky little motors powering the actuators you stated will only pull ~35w at peak, whereas you could, with minor modifications, use something far more powerful like a DeWalt hammerdrill motor - that'll give you plenty of grunt to lift robots quickly. Feel free to buy an off the shelf high speed actuator for the low gear ratio - but you'll probably need to jam the clutch mechanism on it if there is one so as to be able to take advantage of the increased torque given by your new motor.

Off the shelf actuators that get picked up from Ebay or other surplus sources are primarily limited by the fact they're usually designed to open window blinds, move beds, aim Sky dishes, and such like - therefore they don't really need to move fast and can get away with an itty-bitty motor (run at a very high gear reduction). That's something which can be sorted out easily and without going to the extent of a custom mechanism.

[aero_storm]

Re: Expected Speed of a Linear actuator.

Hi Nick,

I am afraid, my friend, that I am a 14 year old, with little or no technical knowledge. I've read up on Robots, I've done as much research as I can, yet I am afraid the only words of the last post that I understood was Drill and and.

The way I see it is thus:

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?

Thanks,

Alex R

[daliad100]

Re: Expected Speed of a Linear actuator.

A word of advice.

Hammer Drills are a pain to pull apart (might just be the one I took apart) because of the extra bit that does the hammer action.

I would suggest using a normal drill as it can't slip into hammer mode and start to reciprocate whilst using it in your robot.

[dragonmaster_1]

Re: Expected Speed of a Linear actuator.

Hi you can get very powerfull linear actuators but they are not cheap got one on a feather crusher
http://www.youtube.com/watch?v=kc6PmRQn_no
this is now going into another bot as a lifter mech 10000 nu of force.

[daliad100]

Re: Expected Speed of a Linear actuator.

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

[Metal Demons]

Re: Expected Speed of a Linear actuator.

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]

Re: Expected Speed of a Linear actuator.

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]

Re: Expected Speed of a Linear actuator.

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]

Re: Expected Speed of a Linear actuator.

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]

Re: Expected Speed of a Linear actuator.

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.