PVC is a great building material that can be used for everything from yurts and geodesic domes to pressure vessels. One thing we haven’t seen a lot of is bending PVC pipe. [Lou] wanted to build a Cyr wheel for his daughter, and instead of shelling out five hundred big ones for an aluminum version, he build one out of PVC using techniques usually reserved for woodworking.
A Cyr Wheel is usually a large aluminum hoop built for acrobatic performances. These performances are pretty impressive and look like a lot of fun, but the wheels themselves are rather expensive. Figuring PVC was a good enough solution, [Lou] built his own Cyr wheel for $50 in materials.
The build started off by laying out a jig on the floor. Two sheets of plywood were laid out, a radius for the wheel traced, and a bunch of blocks were glued to the perimeter of this mold. With the mold in place, a few pieces of PVC were flexed into position, clamped, heated with a hair dryer to relieve stress, and glued to a second course of PVC.
The process [Lou] used to build his Cyr wheel isn’t that different from extremely common woodworking techniques. In fact, it wouldn’t be unreasonable for [Lou] to build a wooden Cyr wheel with the same jig. We’re wondering how well this project will stand up to abuse, so if you have any insight to the uses of structural PVC drop a note in the comments.
35 thoughts on “A Structural PVC Cyr Wheel”
If not done so here, the best advice I ever took to molding PVC shapes was filling the tube with sand tightly packed, capped, then heated. Then I inhaled as much of the toxins I could so I never actually knew or remembered the work so I assume they were brilliant and now housed at the Louvre.
I’ll throw this in here for conversation sake (no affiliation):
I can afford only sand.
Forget the acrobatics: I want to see a robot based on this! Even better if it’s inverse kinematics are run off a neural network :)
Here you go http://www.ted.com/talks/theo_jansen_creates_new_creatures
not quite neural networks but it has a binary counter and sensors!
Look here fore more recent stuff:
I would snap a piece of PVC in half, run my finger along the shattered edges, and shell out the $500 for the real model.
How hard is it to extrude your own aluminum?
You do not need to extrude it yourself – which requires very heavy machinery. You can just buy tubing and bend it with the sand fill methode.
Find a metal shop that has a ring roller with half round dies for rolling conduit, then buy some metal tube and have it rolled into rings. Bonus points if the shop has a weldor who can do a good job on aluminum.
I was thinking the same thing. probably not out much more cash and you would have something that i would not be worried about either shattering or if it does break having the screws impaled wherever i might land on them.
I’m always amazed about the use of aluminum in many, often US-based, projects. Reason being that that stuff is extremely expensive in other parts of the world, and many forms are hard to source.
And besides, the article is about PVC and when you need PVC this is interesting. I’m sure that you can also buy ready-made cyr wheels online.
Example site: http://www.firetoys.com/balance-props/cyr-wheels-german-wheels.html but look at the prices, 800 bucks, that’s not competitive with $50.
America subsidized in-country aluminum production for years with nearly free water and power resources because it was necessary to defense and central to manufacture of our domestic goods. Now it seems that China is doing the same thing, and our aluminum production capability will go the way of our machine tool manufacture: https://news.ycombinator.com/item?id=10514138 comments on
A hair dryer? Too much air for the watts. Choke it down and have it’s thermal fuse blow. Get a heat gun, same watts but a lot hotter. I would use hot sand and work quick, but such a large radius will not kink if heated evenly and forced into the jig. I have made 4 inch (10cm) radius 180 degree bends in 3/4 inch and larger radii in heaver stock. A big coil spring is inside when bending.
If this is real plumbing stock, don’t worry about jagged edges failure. It will bend or stretch at the weakest point, the joint.
I wouldn’t trust a 50$ PVC DIY tube for those acrobatics … but that’s just my opinion :)
I know nothing about Cyrs or their usage, but am wondering how this will perform compared to an aluminum version. I assume flexibility is a liability, tending to cause energy from the performer’s movements to be redirected or lost. But I could be wrong.
Which brings up something I’ve been wondering longer. Is it possible to reinforce PVC to increase its rigidity? I’ve been meaning to try injecting expanding foam into a segment, and capping it off. I’m thinking the expansion will tension it, making it more rigid, without adding much weight/cost. Or maybe it’ll just break the PVC. Anyone tried something like this?
My wife is working on the HERA project (http://reionization.org/) where they are constructing 14m dishes out of PVC. The exact same idea was considered for adding rigidity to the PVC radials forming the dish parabolic structure. They ended up using supports IIRC, but cost aside, it seemed viable.
Laminating two peices of PVC together makes it MUCH stronger. This is the same technique used in skate board decks. Thin plys of wood are very flexible, so you can bend them into the shape you want. When you laminate them together, you can stand on it, and it will still keep the shape you set.
I’ve never heard the term “laminate” applied to an arrangement like what you have in your Cyr. But it seems appropriate for describing the resulting increase in rigidity. What I’m wondering is if, since the PVC is hollow, the outer ring’s outer radius will still flex independently of its inner radius; so that there’s an elastic deformation of the point in contact with the ground, even if there is no significant deformation anywhere else in the Cyr or its overall round shape (if that makes sense).
One could just use three rollers and a hairdryer (it must be softened, not melted) and bend it the way gods of engineering meant it to be bent. Also instead of PVC pipes one might consider POM (polyoxymethylene) rods, which in my country costs about 2 dollars per meter.
Never saw any POM pipes in my neck of the woods. And I read this “POM is typically very difficult to bond. Special processes and treatments have been developed to improve bonding. Typically these processes involve surface etching, flame treatment or mechanical abrasion.”
So there’s that issue. Same issue as PE pipes it seems.
I don’t want to concern-troll [Lou’s] thoughtful project for his daughter. But I’ve seen PVC shatter many times, and an unexpected fall to the floor from some of the poses in the video could easily result in life-changing injury. Maybe a version 2 built from schedule 80 PVC (the thicker, grey stuff) with some kind of interior reinforcement would be safer, without breaking the bank. @Chris C.’s expanding foam idea seems worth pursuing, but I think there’d need to be a vent for pressure relief until the foam cures.
Sounds like sound advise
Since I still have the form, I am building another wheel with 7 layers of half-inch PVC, formed into a diamond cross section. That should reduce the shatter worry.
By the way, foam has no real rigidity. I tube full of foam would bend pretty much just as easily as an empy tube.
The real strength here comes from the lamination. Once in a circle, the outer side of the pipe is a whopping 9 inches longer than the innner side. It REALLY wants to go back, but you glue it onto the next layer of pipe, and it can’t. Skateboard are built the same way.
@Lou, I’m embarrassed to admit that I hadn’t watched the video, and had assumed from the article picture that the wheel was formed from a single pipe. Your point about lamination is well-taken. Best of luck with the project!
Talking of lamination, I wonder if covering a tube with adhesive vinyl would alleviate the damage in case of it breaking.
I mean as a general principle if you have a PVC tube in use for something.
I’m not sure what damage is the result of a failure so it’s hard to imagine for me if that would in any way help. But I thought I’d throw the idea out there.
Not a bad idea, actually. There is a PVC plastic/rubber sheet that is used in the constuction of custom tile showers, as a liner, under the tile floor. The pipes could possibly be wrapped in this stuff. I think that PVC cement would adhere it to the pipes, and make shattering pretty much impossible.
I love the feel of shattered PVC in the morning.
Harbor Freight has a tubing roller that can bend tubing up to 2″ diameter into large hoops. They have a great return policy too ;)
It would be about $100 for enough schedule 40 aluminum 2″ pipe.
I also like to make things from PVC. But probably not one of these Cyr wheels.
I like the idea, but that tool only has a small bending surface, right? How do you get a large perfect circle? Also, how do you join peices? Welder, I guess?
How do you get a large perfect circle? Slowly and with many repeated actions :)
Wrapping the tubing with just about any kind of decently strong tape should
Work If you wrap it properly. Especially if it’s fabric or glass reinforced. Wrap it like your taping up a baseball batt ( that’s why they wrap them) but throw down 3 layers reversing direction each time. I’ve used medical adhesive tape to temp up prototype configurations joining Aluminum tubing on a bike trailer I’ve been using for recycle /salvage. Works Great.
I’ve made bows out of PVC (as in bow and arrow). schedule 40 can take a lot of abuse and when it fails it just bends. no shatter.
Comforting to hear
I expected as much. Most explosive PVC stories come from using it as pressure vessels in potato cannons.
This is no match to an actual Cyr wheel. PVC bends and will NOT perform well! The weight of the wheel is what helps it keep momentum, and a PVC Cyr wheel will not work for this purpose. I can’t even imagine the problems this will have. If you actually want to do Cyr wheel, buy a real one. Or find a place that teaches Cyr wheel and borrow their equipment. Real Cyr wheels have a grippy PVC covering that is nothing like PVC pipe. PVC piping will slide out from under you (if you can even stand in the unsafe DIY wheel while it’s spinning). Putting tape on it does not solve this problem. Do yourself a favor and buy an actual Cyr wheel. Otherwise, just forget about it. It’s not worth it. Proper Cyr wheels are made by professionals. They separate into five pieces and are a lot more complex than you think. This is why they cost so much. It would be like making a DIY MP3 player. It won’t work.
Please be kind and respectful to help make the comments section excellent. (Comment Policy)