Flipper (pneumatic) VS Lifter (electric)

Hi All,

I€™m building a feather and I€™m contemplating using a electric lifter, on it€¦.However I€™m tend to think a pneumatic flipper would be better.

I know my skills are limited so I€™m leaning towards an electric lifter but I€™m concerned that it will be to slow to lift (without the other robot managing to get away before I€™ve lifted it).

Can anyone advise/ give me their opinion on what is better?

Also I was looking for advice on what the electrical and mechanical mechanism would be to create an electric lifter. I€™m looking for a lifter to be as fast as possible, so any ideas on how to construct a fast electric lifter? Would a window wiper motor be any good with a metal arm fixed to it?

Any suggestions would be great

Thanks
billy

A fast lifter or slow flipper needs 1 thing from the setup. Motorpower. Volts * amps.

And you can achive that by combining the right motor with the right gearratio.

A window-wiper motor... Several problems.
1) the fuse in my car for the wipers is a 10A one. Meaning the most you can get out of such a motor is 120W.

2) overvolting is asking for a broken wormgear wheel. Most, if not all wipermotors use a hard plastic wormwheel. It can't handle overvolting nor heavy shocks.

I learned that lesson with Project I and II where the wipermotor was used as a big steering-servo-motor to control the back wheel.

so a good heavy motor and good gearing is the answer. Would it be cheaper than pneumatics or sound the same.

Heavy is a no no in a feather. But light and powerfull is most of the time equal to expensive.

On the cost. A simple RC switch and relais that are strong enough to control the used light and powerfull motor are about equal in pricetag to a RC switch and valve setup.

Cost of gearing depends on your capability to scrounge, beg or find cheap, useable gears ,sprockets, chains, belts and assorted stuff.

In the end, the BIG advantage of using pure electric power is that you can extend the range easely by adding more amp-hours in Battery.
Something very difficult with a custom build pneumatic setup. (the bottles available come in only a few, large sizes)

Hi Billy,

Check out this video and see what you think for the speed of an electric lifter;

http://www.youtube.com/watch?v=TnX9CZfSaz4

thanks for the input guys, thats starting to get me to think now...electric or pnuematic. That wee lifter was a lot faster than what i thought it would be...........and great idea about the threaded rod and a drill motor.

Would something like this work?

http://forums.airsofters.co.uk/pictu...pictureid=1136

You'd be better off using a threaded rod in that kind of set-up - your drawing would put large demands on the motor gearbox which most small ones couldn't handle. You can still get fast lifting speeds with a threaded rod - 'ploughbot' being a good example

what would I need to change in that set up to make it a.threaded rod idea?

Would a set up like this work then?

http://www.airsofters.co.uk/forums/p...pictureid=1140

a drill motor linked direct to a threaded rod, which is fitted inside a tube. On the tube it has a nut welded to it in order for it to go up and down the threaded rod.

if this would work...... any ideas how to connect a drill motor to a threaded rod without welding it?

turn an adapter for 3/8 unf thread 1 side and the thread for the threaded rod you want to use on the other

i see. I dont have a milling machine etc.....can anyone make and adapter for me?

There are only a couple of ways to attach the rod to the drill motor without welding, but with the rotational forces that will be going through the connection, welding will most likely give you the strongest connection.
One alterntive is what Jonny just mentioned; have a shaft collar (basically a bit of thick-ish wall metal tube) that has one half threaded to suit the thread on the output shaft of the drill motor and the other half threaded to suit the rod. You could then put some grub screws through the wall of the collar to press down against the joints once they've been threaded, just as an extra form of security.

Another option is to keep the chuck on the drill motor and put the threaded rod into that (if it's too large in diameter, see if you can get it lathed down to a suitable size) and then tighten the chuck. This won't be strong enough on its own, but if you then dill all the way through the chuck and the threaded rod (say 5mm diameter) and then put a pin or 5mm bolt through it, it will prevent the chuck from loosening and the threaded rod from falling out.

say you want to use 12mm threaded rod. Buy a small block of mild steel off ebay for next to nothing. Drill and tap an M12 hole through one side and drill and tap a 3/8unf hole the other. To make sure they line up, you could drill a pilot hole right through the block.

You don't need fancy machining centers to make parts, just a bit of imagination and some basic tooling

thanks for all the help guys.....would the above design work though? and would a 12v dewalt xrp drill (running on 18v) be a better option for the lifter motor and gearbox?

Should do yeah. As for the drill motor, I can't say but a standard argos 10 quid motor would be more than up to the job, anything bigger is just for boasting purposes

I have a spare 14.4v dewalt xrp drill lying around so it'll be it....and boasting lol.

As Gary said you should have more than enough torque for lifting be it a cheap argos drill or a dewalt, what you might want to look as is increasing the potential speed of your actuator though - obviously the faster the motor rotates the faster it will lift but also the larger the thread pitch (e.g. 12mm thread has larger pitch than 10mm). Also bringing the point the threaded rod/actuator meets the lifting arm closer to the pivot point (and adding an intermediate linkage to increase potential movement arc) are things to think about!

If you were after a threaded rod with a high pitch and good power transfer then you could even look at using ball screws,

http://www.ebay.co.uk/itm/Machined-Ball ... 1c1c922830

These are using in computer controlled mills and lathes to control the axis. Precise and a 5mm pitch would be very useful but the price reflects the machining precision you get with them :)

Those ball screw things look good. Would a 5mm pitch be a good enough pitch to make the lifter fast? Ie. So I it would take less turns to travel the distance?

Yeah with a larger pitch your lifter would move further for the same amount of turns as a thread with a finer pitch. A 5mm pitch would most likely be fine - even the pitch of scissor jack threaded rods, while less than 5mm, are larger than standard M10 or M12 threaded rod:

[attachment=0:3dxp1kyd]k3_build (36).JPG[/attachment:3dxp1kyd]

Not the clearest of pictures but you can see the threads are more spaced out compared with standard rod; this is one reason Kaizer's lifter has a good speed. The threads are also thicker and more durable, and the threads on a machine ball screw would be even more so.

I would start out with a regular threaded rod. It's cheap and simple to implement. Get used to building a bot and get it into the arena. Then look on ball screws or an acme thread as an upgrade later down the line. Believe me, you will have enough worries getting a robot running in the arena!

For reference, say an M12 threaded rod has a pitch of 1mm. It means that for every one rotation of the rod, the nut will move 1mm along. A 5mm pitch will mean that the nut moves 5mm along for every rotation. But there is a cost, it does mean that the motor will have to work harder to lift the same amount of weight at the end of the arm.

If you do get around to using ball screws then I would recommend covering the rod in an extending metal coil and don't open up the nut, ball screws work in a very interesting way by using small ball bearings to travel along the rod. They are a pain to get back together correctly if you take them to bits.

one of these

http://www.ebay.co.uk/itm/1-Tonne-10...item3f02488ddb

cut down be ok? I figured that the thread pitch on this must be ok as it doesn't take long to raise on of these by turning it by hand.

how did you connect the jack threaded rod to your drill motor with that set up? did you use a collar or weld it or....?

M12 does have a tread of 1.75mm.

My lifter looks a bit like jamies
here's a pic
[attachment=0:3afxhwcm]untitled 2.png[/attachment:3afxhwcm]

Thanks for the photos, has given me a good idea of what to do/ expect.

I think my lifting system will be similar to this now:

http://forums.airsofters.co.uk/pictu...pictureid=1148

have a look at my thread, this is what I used to build my robot
viewtopic.php?f=111&t=3440

Thanks for the link i've just sat and read through it all. You mentioned putting a limit switch on it so when it was fully extended it would cut the motor off.. What did you do in the end? If you were using a speed contoller surley you could have stopped the power to the motor using that?

I didn't in the end as it was too complicated to do. I just used my eye to see when the lifter met it's end point of lifting

I see. Did u just use toggle switch connected to a servo or did you use s speed controller.

CONTROLLING THE LIFTER MOTOR
=========================

I ' m thinking of using a servo with a toggle switch or similar to turn the motor on - off - backward, rather than a ESC. Would there be any advantages using a ESC rather than a switch to power on - off - reverse?

Would two micro switches glued to a servo work? if so can anyone help me with the wiring, so that the motor can be on - off - reverse?

Thanks Guys
Billy

I would go for one of these http://robotcombat.com/products/0-TD-RCE225.html they will control your motor, and have limit switch inputs so you dont stall/over-run your actuator.

You can do it with servo/microswitches, but i would use them to switch relays to handle the load, you can also fit limit switched into it as well.

Thanks for the link and the pointers. Just because it's my first robot I fancy having a go and making a switching unit rather than buying it off the shelf. Do you know how I can wire the micro switches to the relays?

Hey Billy,
I used a bang-bang controller for my first robot which was an electric lifter.
I would use a ESC if u had the maoney as they are far better
The problems with the servo setup are;
It doesnt have a failsafe so when i turn my transmitter off it goes either full forward or backward
It either goes full speed forward or backward so you can't controll how fast you want it to go at.
I am now using an electronize FR15HVR which works perfectrly

Thanks for the input. I know what youre saying with full forward or backwards. I thought about that. I just thought they be a cheaper way of doing it. With a spektrum 2.4ghz transmitter does that have a fail safe?

spektrums do have failsafes
it is the cheapest option and does work but the only thing is that it isnt reliable

aye, I know what your saying. you get what you pay for :lol:

Thats the thing with robotics

I wouldn't use a speedo on and arm, unless you have limit switches or closed loop.