Robot Pit Lift

[Burg]

I was wondering if using the pneumatics from the kit to build a cart for the robot would be possible. The idea would be to build an electric pump truck, in theory. We would power the wheels using electric motors, always on full power, just turned on/off through a power button. But to lift the robot + platform up to amost 4' with pneumatics? How possible is that?

You could start at the minimum height of...2', and use a cylinder with a 12" push, gear it in a way that it will lift double that, with a 130 pound weight ontop. Am I crazy, or is it realistic with the pneumatics supplied?

Thanks!

[thoughtful]

i think its very possible. To be easy on your pneumatics, i would suggest you use 4 cylinders.

If you want to start at the hieght of 2' you can order cylinders of 24" in length( not throw) the throw should be around 21"22". This way you can almost go upto 4'. 4 cyclinders should have no problem lifting a 130 lb platform upto 4'. Thats only about 43 lbs per cylinder. You can use extra air storage tanks, because this shouldnt be a problem in this case. You will have to seldom fire up your compressor. Any questions are welcome, post some pics when done, when/if you take on this project and finish it.

[Kevin Sevcik]

Alternatively, you could use a heavy duty scissor lift as seen in older car jacks. The problem with using pneumatics is that they're bouncy unless you use a lot more force than you strictly need to.

Also, I'd be wary of running the cart driving motors at full speed all the time. It will either be too slow at some point or too fast. If you don't want to use a full blown control system, look for a heavy duty rheostat. Say a wall light dimmer rated for 50+W. Then you can "dim" your motors and control the speed. Only in analog.

[Burg]

How would you power the scissor lift? Using a motor? Which kind?

And the dimmer idea sounds cool, but my intentions were to run the motors at half speed by reducing the voltage/current. And keep it at one speed, all the time, with just a button to turn on the motors. I like you're idea though.

And the 4 cylinders I shall look into. I could lift at all four points to reduce any shakes, no?

Thanks guys.

[thoughtful]

yes, the dimmer is a good suggestion otherwise u will have no control whatsoever.

This year we have looked extensively into pneumatics, they can be very stable if you make them, specially when you have no storage limitations. You can even have multi-positioning( having the lift stop any where you want). cylinders with 1 1/2" bore should be sufficient enough. There will be very little shaking if any.

The scisor lift can be either motor or pneumatics powered. A motor will give you much more control, and various positions very easily. If you do decide a scissor lift i would suggest motors. However,the scissor lift has its dowsides too, but if you are only looking for a 4' extension it should be sufficient.

[sanddrag]

You need something like this http://www.harborfreight.com/cpi/cta...emnumber=46604
but a little smaller.

As a note, that vehicle looks very unsafe/unstable on that thing.

EDIT: Here's one more the size http://www.harborfreight.com/cpi/cta...emnumber=41145 but it is still too heavy and too expensive.

[Burg]

Originally Posted by sanddrag

EDIT: Here's one more the size http://www.harborfreight.com/cpi/cta...emnumber=41145 but it is still too heavy and too expensive.

Wow, that is exactly what I'm looking for, except I don't intend on buying anything. But how does the hydrolics work on that thing...I can't even see anything hydrolic on it. Care to explain?

Thanks

[Mark Pettit]

With that much weight going up and down on whatever kind of lift you're creating, make sure you keep everyone clear of that thing while it's activating. That could hurt (or worse)!

[Jeff K.]

Hey, our team was also thinking of a lift somewhat like that one Sanddrag. We were going to use 4 cylinders we ordered and maybe even two compressors, probably 2004/2005 to power it. The dual compressor action will totally be overkill, but will also be really cool. But for powering it, I was pushing for using an idea for the drivetrain another member of our team had for the offseason to build, but we didn't get around to doing it, but then another guy wants to just tow it in on his barstool racer he's building.


Edit:
And more info is below.

[Manavapor]

my team is currently working on a lift using the pneumatics from this years kit. I have been developing the idea for a year now and i have decided to use a scissor type lift. We ordered 3 2" bore 24" stroke cylinders for the lifting and we are going to use telescoping steel square bar on all the corners to prevent wiggle. We are also thinking of running 2 compressors on it

Heres a very crude drawing made in ms paint.
http://img159.exs.cx/my.php?loc=img1...ntitled1re.png

And now i took the time to make a little nicer one in photoshop. I tried to make a top view one bt i totally botched it. hope this helps.
[IMG][/IMG]

[Al Skierkiewicz]

Guys,
I have to put a big caution here. Pneumatics operate like right now, while hydraulics can have some control. (It's all in the valves) I would caution against using something that you can't stop once it starts. I saw a team a few years ago that had a pneumatic actuator on each wheel. When they hit the button, the whole frame and robot jumped up two feet. Knocked one of their pit guys over it was so fast. When a hose popped off and dumped the robot on the floor, they finally stopped using it.
As to using a dimmer, those are only designed for lighting at 120 volts AC and won't work at all on 12 volts DC. A variable speed control from a DeWalt drill (if you are using the NBD trannys) might work for each driven wheel. A foot operated pump up platform is a great idea. Anything that you can do to get the robot up to working height will save your back in the pit as long as you can get it down to where the robot fits through the doors.

[Kevin Sevcik]

Well I was thinking an old-style rheostat dimmer, which is just a big variable resistor, which should work fine, really. I'll agree that newer kinds of dimmers don't have a chance of working. I was just trying to come up with a cheaper easier option than an entire control system. One fixed speed just seems like a bad idea. Either you'll be in a rush and it's too slow, or you'll be in traffic and it'll be too fast. At the very least, make up some voltage dividers and have 2 or 3 speeds and a multi position switch.

As to actuating the scissor lift, I'd go with a lead screw and a motor turning it. I was specifically thinking of a device the Mythbusters used in the ceiling fan episode if you've seen it. This too would be a good place to have speed control.

Finally, whatever system you use, you might want to think of a way to lock it in place. Better safe than sorry and all that.

EDIT: This is what I'm talking about: 200-Ohm 50-Watt Rheostat

[sanddrag]

Here's a speed control http://www.harborfreight.com/cpi/cta...emnumber=43060 but it is only rated for 15 amps, and being from Harbor Freight, I would trust that to be the real maximum capacity.

[Kevin Sevcik]

I'm tempted to say that thing is AC only since it has three prong plugs all over the place, but it's rated in VDC. I'm forced to conclude that I have no earthly idea how it works or if it would work for 12VDC.

[NickNielsen]

Let me add to Al's caution. If you use pneumatics to activate any kind of load-bearing lift, do not depend on the pneumatics alone to hold the load while you work. Include some kind of mechanical support to prevent your lift from falling unexpectedly if a hose or component fails--think of it as jackstands for your robot.

Please, for safety's sake, if you want a maintenance stand and lift for your robot, get one of the many that are commercially available. Don't build your own!

<Edit>To use a single rheostat to control your motors, you will have to calculate the total power consumption of all four motors, then obtain a rheostat able to absorb that power. For the CIM motors provided with the 2005 KOP, you will need a rheostat that can handle the stall current of 133A (1600W) per motor. Again, the best bet is a commercial model.</Edit