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iRobot Scholarship idea : Pool Cleaner Answered

I've seen mods for the roombas before, where the robots are water sealed, and then the wheels are turned into propellers. My idea is that I could water proof the robot in plexi glass, or something, and then a net on it, to collect all the leaves, dead bugs, and other stuff that collects on the surface of a pool. normal pool cleaners only vacuum the floor of a pool, and it takes days for floating leaves and other grime to sink to the bottom. With a robot like this, I could just set it in the pool, and let it clean everything up. What's nice is, when company is coming over, it's embarrassing to have a dirty pool...this modification would allow you to quickly clean up your pool-even on short notice. Update (for some clarification): What I would want to do, is make a case for it, so that you can simply remove the wheels, and connect the propellers/steering device to where the wheels were, then just place the roomba in the watertight case, and it would be able to swim around and clean! Also, i'm working on some sketches of how it would work. I'll post those when they are done.

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ewilhelm (author)2007-08-28

This might be a little late, but one of the tricks I know for building underwater robots is to pressurize the inside of the robot; so, if there are any leaks, air leaks out rather than water in.

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That's a really neat idea, and it makes a huge amount of sense. Unfortunately, I am past that point...we're ready to add the bushings, axles, bearings, etc. today. The entire box is waterproof, except for the lid, which will still have weather stripping. Thanks for the idea though, if I ever one another one, i'll definitly try that.

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Weissensteinburg (author)2007-08-03

Ok guys, so my latest design works like this:

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X---|---o|o----|---X
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If that stays how it should...then the X's are water wheels, the -'s are axels, the o's are bearings. The robot will be places on top, so each wheel will power one propeller. The bearings will be used to keep the axels in place. Bushings will help keep the axles water tight...but I need help finding rubber bushings...does anyone know where to look? I'm using 1/2" pipe as the axle, which needs to fit through the bushing. Also, i'm seeing measurments on bearings such as 5x11..what does that mean?

Thanks =]

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> I need help finding rubber bushings . O-rings epoxied to the case? Would need to be a relatively loose fit or you'll lose too much power from the drag. . cooblades "grease seal" might work. . > Also, i'm seeing measurments on bearings such as 5x11..what does that mean? . I used to know that, but can't recall it to save my life. It's hell, getting old. Check out the web site of a bearing manufacturer (eg, Timken) and see if they have a page that explains it.

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apparently the drawing didn't hold up.

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SacTownSue (author)2007-06-30
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I've seen that, the thing is though, their cleaners don't clean the entire surface, like this will.

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Weissensteinburg (author)2007-06-15

My latest idea consists of a short length of metal pipe, with some kind of ridge, because the robot rolls with tracks like a tank, not wheels, so hopefully I can make the wheels spin the pipe, which then uses something (like the coupling) to spin the propeller on the outside. Where can I get a pre made propeller? Radioshack, maybe?

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aarone (author)Weissensteinburg2007-06-29

I don't think Radioshack'll carry anything like that. Try a hobby store.

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I order them from tower hobbies. Their cheapest are about $1.15.

http://www2.towerhobbies.com/cgi-bin/wti0093p?&C=BGF

If it were up to me I would just take apart the irobot and rip the connections off the motor and use a external motor to power the boat. It costs more but its easier. However your pipe idea is very novel, I would love to see a video if it works.

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How big/how many blades do you think a propeller for something like this would need?

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I bought the LXE473 because it fit onto a Lego axle. Honestly for something like this you can't go wrong ordering a few different styles and just use trial and error.

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k..I'll see if I have anyone local that sells things like this. My latest design will have a 3/4in pole as the axel. I will put 2-3 layers of heat shrink tubing on it, so that the wheels have something to grip on to. Then, I will cold weld a bearing to a hole in the plastic, and cold weld the axle into the bearing. Which is where I get to my next problem..I'll need to make the axle thinner, so a propeller will fit on it. But the JB Weld sealing the bearing to the plastic, and the pole to the bearing should keep it sealed against water.

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. For the heat-shrink, I'd try a local electrical/electronics supply house (where the local electricians go to get their parts) or hobby store (eg, Radio Shack) - shipping will eat you up on something like that. Explain what you're doing to a manager and you might get some stuff for free - especially if you promise to put their logo on your 'bot (check the rules first). . Try something similar at an industrial supply house for the bearings and other mechanical parts. They may be able to make some valuable suggestions, too. . cooblades is probably right about the prop not being that critical. I wouldn't think that speed is that important for a pool cleaner as long as you can produce enough thrust to push a full net around. An R/C boat site might be the best place to ask if you want a definite answer. I'll try to track my friend down tomorrow, but I have the feeling that what he does won't scale down very well and all he'll be able to provide is generalities.

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That place is within driving distance from me, though. And their whole thing is like for hobbyists and such.

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> Where can I get a pre made propeller? Radioshack, maybe? . I'd start looking at radio control (R/C) sites. Shouldn't matter if it's boats/planes/cars/whatever. Their equipment is designed to be light and rugged, if not always cheap. Should be able to find all sorts of props, gears, levers, cams, servos, etc. Don't know if a ducted fan design would work for the prop, but it would look cool.

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Actually, I'm volunteering at my temple, and they have me setting up the computer lab...we have to throw out a bunch of computers that were donated, and don't have certain key parts of a computer...i could take a fan from that, and take out the propeller.

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> I'm volunteering at my temple . Kudos for volunteering and Shalom. . . I'm guessing here, but I don't think a computer fan will work well - too many blades and designed to run at higher RPMs than what I think you're looking for. Might work for proof-of-concept, but I'll bet you need a "hydraulic prop."

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What do you mean by hydraulic prop?

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> What do you mean by hydraulic prop? . One designed to move water (vs. one designed to move air).

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Ah..I was hoping that you didn't, for some reason, mean the kind of hydraulics in a back hoe.

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. ROFLMAO! As you can probably tell, I'm trying to apply what I've learned in an industrial environment. It wasn't my money and efficiency is not as important when you have a 480V/3-phase power source. You seem to be doing a good job of translating what I suggest to The Real World.

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I can't tell..is that last line you being sarcastic?

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. Not at all. I would not have sent the PMs if I didn't think you had a pretty good head on your shoulders and have a real good chance of making something that works well and is practical. . And you seem to know what you can and cannot do with the knowledge/resources/time you have available. Some of the other proposals are very good, but I doubt that the proposers are accurately appraising their capability to actually build it (particularly time and money).

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W_world (author)2007-06-21

Really neat idea. Have you considered making it submersible? you could use a "swim-bladder" type system to ballast it. I think it would be cool if it could seek out debris in a 3D setting; you could use a camera to find the debris against the solid color of the pool walls.

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Weissensteinburg (author)W_world2007-06-21

I think that if I were to step up to that level, it would make it infeasible for me to do in less than two months..i'd need: Totally water proof casing cameras and face recognition like software motors..and a way to control them in relation to what the camera sees automatic water pumps etc.. Good idea, It would just take too long, and would be very expensive.

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loubard (author)2007-06-20

Isn't this similar to the Scooba product iRobot already available? Great CAD btw.

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Weissensteinburg (author)loubard2007-06-20

No, the Scooba mops tile floors. iRobot does have a pool cleaning robot, but not one that cleans the entire surface of the pool. Thanks..I had to sit around for a while (long story) yesterday and the day before, so I spent a while working in sketchup.

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Weissensteinburg (author)2007-06-19

I've made a semi decent drawing of it on sketchup...now what would be the best method to export it?

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. That looks great - both the design and the drawing. I really like the funnel/scoop design. I think the prop needs to be closer to the centerline or it will go in circles - some bias on the rudder may handle it.

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Thanks! I'll be able to fiddle with the alignment when/if I make it.

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..figured it out. The video shows an animation of the it from different views.

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NachoMahma (author)2007-06-17

> How big/how many blades do you think a propeller for something like this would need? . If noone else has an answer, I have a friend that has a speedboat (and seems to know quite a bit about prop design) that I can ask for some tips. Not sure how well what he knows would scale down. I'm betting that the speed you will be turning the prop and the amount of torque/HP available will be the major factors.

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It would be great if you could ask him. I've been trying to guesstimate (can't believe i just used that word) how fast and how strong that robot will move. Do you know where I can find those kinds of specs about the create?

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. I talked to my friend and (after much discussion) he recommends getting a prop with ~18" pitch and a diameter of ~4". This will probably be too much prop, but he thought you should be able to chuck the prop to a drill and use a file to make the prop smaller and smaller until you get the speed you want - if it looks too ugly get a new prop of that size. He said you may want to start with a 3" prop, too many variables to be sure.

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Thanks. I called our local hobby shop (like I told you about before) and they do have a selection of props. Also, do you think there's a way to water proof the bearing I posted a link to?

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> do you think there's a way to water proof the bearing ... . Not that I know of. Most of the brgs I've seen that needed to work underwater either used a pressurized lube system or were designed to use water as the lube. I'd try it and see what happens - it'll probably last long enough to get your project built and a video shot. As cheap as they are, even a poor student can afford to ruin one or two. Silicone spray may help, but it's as expensive as the bearings. . . That's great having the hobby store nearby. I'd try browsing the aisles for ideas and inspiration. They probably have all sorts of gadgets, widgets, and gizmos that will come in handy.

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NachoMahma (author)NachoMahma2007-06-18

. Have you tried seeing how the R/C boaters pierce the hull? Remember that my background puts me at a disadvantage at the scale you are using (when you're using a 100HP motor, frictional losses from a bearing shield just don't matter). This kind of thing is what keeps boaters up at night experimenting and I bet they have much better ideas than I.

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I think that I might just put the bearing inside, and then have a tight hold drilled in the plastic, and use petroleum jelly to lube it/water seal it.

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I don't know if i'd call it nearby...but i think i could annoy the rents into getting me there...

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. No idea on the specs of a Create. If you can't find the specs on the web site, try contacting someone at the company that might know.
.
. I'll talk to my friend and see about getting y'all together. I do remember him mentioning a web site called Scream and Fly. Just checked and sure enough, http://www.screamandfly.com/ is a site for "hot rod" boaters - try posting to one of the forums. They may even be able to tell you how to guesstimate. LOL

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NachoMahma (author)NachoMahma2007-06-17

. Well... I went to the iRobot site, but everytime I'd get close to what I thought would be helpful I'd get a Flash not installed msg. The info seems to be on the web site, but I can't tell. If not, it appears that they have a few good ppl in the forums - maybe one of them knows (or can give you some ballpark figures). Wouldn't be surprised to discover one (or more) of the engineers hangs out in the forums.

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cooblades (author)2007-06-15

Oh btw just to warn you water robots will always veer off course. Also the propellers will create a counter torque which will make your robot veer into the wrong direction so when you mount them, make sure they are not straight but at an angle to correct this. My guess if the propellers are anything like RC planes it should face the bottom right. Sensors will be a must if you want anything that does more than get stuck at the edges. Especially for a skimmer. The level of difficultly programming a water based robot goes from Crawler, Skimmer and Hovering being the hardest. Good luck!

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oh really? i always found that skimmer was the hardest, followed by hovering then crawler... always found that all of the challenges of actually being partially submerged in water far outweighed the challenges of keeping the hovercraft above water...

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I meant hovering underwater in the definition "wavering between conflicting positions". In the video I posted the first robot is a hovering robot the second was a skimmer and the third was a crawler.

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ah, sorry, I mistook hovering as my favorite type of land robot!

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Yeah, this will definitly be a skimmer

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NachoMahma (author)2007-06-16

. Have you done any prototyping of a mag coupling yet? The more I think about it, the more problems I see for a DIYer on a tight budget and short schedule.
. It will need some type of thrust bearings to keep the magnets apart. The bearing mounts will need to be sturdy, which may present space or aesthetic problems. For your use, plastic/plastic or plastic/steel may work, which would make them easier to fabricate, ie, no "real" bearings, just pick low-friction materials.
. Alignment may present problems.
. The distance between the magnets (hull + 2 airspaces) may require larger and/or more expensive magnets that don't fit your space or budget.
. These may not be a problem for you, but I think you need to do some experimenting before you get too far with your design.
.
. While I think the Cool Factor of a magnetic coupling is orders of magnitude greater than cooblade's grease seal, the grease seal should be much more practical. Very easy to seal the hole in the hull and it shouldn't be too hard to find a "grease" that won't leave a slick.

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I haven't..my plan was to find some, like you said, low-friction materials..the magnets would keep each other in place, and separated by the Plexiglas. The only distance between them would be about a fourth of an inch of plastic.

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