a hard question

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So we're thinking of running a goaltimate league on Tuesday nights at Trillium. (Goaltimate is like half-court ultimate where you score through a hoop.)

The tricky part is we can't anchor the poles into the turf and we can't use 18.5l water bottles because there isn't an easy way to fill them at that field.

So the question is, are there problem solvers out there who could help us engineer a solution? I was thinking about something like the link below but without the mesh.

What do y'all think?

I know that some people use weightlifting plates as anchors on hard surfaces. A 25lb plate is more than sufficient, but users like to cover them with a stiff cloth or mat to reduce the footing hazard.

I've given some thought to the safety of sandbags, but their awkward shapes can make them even likelier tripping hazards, so I've never experimented with them.

The kit on the attached link looks good, but I'd include a ring on the front side as well. So you'd just need a T-junction for the shock-cords. You'd still want to weight it with something, though, lest you find yourself with a drifting goal.

I would think having a cord run directly across the goal line would be the biggest hazard of all.

I think the weight plates are probably one of the better solutions, but they won't address the moving hoop issue in the same way that the water tanks would (no vertical stabilisation). I would think a stiff tube (PVC/steel) that the plates could slide over and the goal slide into would be the trick, especially if the bottom of the tube, where the plates will sit, was flared enough to prevent the plates from sliding off the bottom if the goal happens to be tipped over.

After chatting about this with Speedo on and off for a few weeks, I was humbled by the power of Google today. :) Searching for 'goaltimate on artificial turf' actually returned a few results.

1. "Take some small multipupose plastic buckets, stick an extra wide 3ft pvc pipe through them (sized for the goal to slide right in), put some iron weights in the bucket, and fill with concrete. Insert standard pvc goaltimate set." That sounds a bit heavy but solid.

2. Burnaby's been playing goalty on turf for a while. Cowley apparently designed something that works: http://cowbels.ca/2011/02/27/turf-goaltimate-kit-reborn/

Send any thoughts you have on the above to Speedo (or post here).

Any idea of what kind of weight is required to hold the goal sufficiently steady? My work uses plastic buckets of various sizes that I could...procure...for the cause. We have 4, 6, and 8 L pails that we use on a regular occasion. Looks like concrete is probably about 2 kg/L, so if atanarjuat's 25 lb mark is enough, that'd only be about 5 L of concrete. That said, smaller is always better if we can get away with it. And of course, this all means you're asking someone to not only bring the awkward goal kit, but also buckets full of concrete, so smaller = lighter = better.

Anyone who has used the water containers before: how full do you need them to be?

I'd have guessed the stability criterion at about 35Nm of torque on a single anchor. (I think you'd like an anchor that would remain stable for up to 5lbs-f at an equivalent of 1.5m in height -- seemed a reasonable approximation). The stiffer your hoop; the bigger this number should be.

Whether you like that number or not, the point is to visualize an anchor layout for a given torque. So if you were using a standard 45cm, 25lb Olympic plate, turning that over around its edge would be equivalent to a maximum of about 25Nm. And turning it over completely would require a shock of about 25J (ignoring the weight of the hoop itself).

For additional perspective, a full 19L water jug (I think half-filled usually works?), with a 25cm diameter can resist 24Nm before lifting, but because its centre of mass is already high, it takes considerably less work to turn it over (~2.5J, if I'm keeping the numbers straight).

So you can use those reference examples to figure out how much weight you'd like in a pail of a given size. Rather than making the anchors heavier, it's just as effective to make their bases a little wider, of course.

[T] = [r] x [F]

From Speedo's initial post, am I correct in understanding that water bottles have previously been used successfully? From atanarjuat's writings, the original water-filled bottle may not be an ideal anchor but if it works well enough it seems no more unwieldy to bring full bottles to the field than to bring concrete-filled pails, and the bottles have the advantage of not requiring any construction. Of course, following from IN's point, with concrete's greater density a smaller (and therefore preferable) anchor can be used with concrete than with water.

I've used water bottles, and they work great. They don't need to be full. And if they tip occasionally, not much spills out. I wonder if there is a hidden tap at the field. Near the washrooms maybe?

Anyway, if we just work out the numbers with the formula above [T] = [r] x [F] it becomes pretty obvious that [this problem has already been solved] x [trying to convince me concrete is a good idea] = [waste of time]

Ryan

Math is hard.

Question: where will we keep these things and who will bring them to
the field each week?

With purpose built concrete bases, we would probably be able to leave
them at the fields.

I'm thinking quick set concrete cast about 2" thick into mold made
from a oil drain pan ($4 at cdn tire.) The pans are about 18-20" in
diameter (wider base than a pail bottom) have a nice taper. We could
cast in a piece of PVC in to receive the pole. I'd probably be inclined
to case in a loop of rope that could be used as a handle.

For reference.

Achoo's 2in. thick disc at 20in. diameter has a volume of 10.3L. Assuming your concrete weighs in at 2.4kg/L, the plate would weigh ~25kg (54lbs).

It would be able to resist a torque of 63.5Nm without budging and it would take >60J to flip over.

Not endorsing or contesting the idea -- just facilitating.

david cowley from burnaby ultimate has engineered a solid solution

So is the goaltimate league on?

Registration for Goalty didn't open on the weekend like we'd planned, but it's open now!

As I understand it the Goaltimate League is not moving ahead in Vancouver at this time, but I figured I'd share Burnaby's solution anyway.

What we did is we built modular bases to anchor the arch, these in and of themselves are not very heavy, but they provide a platform on which you can put additional weight that is handy: ultimate bags, weights, sandbags, whatever. The bases are also built so that in the event of a collision the base "should" come apart, resulting in less injuries (or less serious ones).

An earlier post in the thread described our solution to a point, the one linked to below illustrates the construction of one base (which when combined with the information from the previous post) will provide you will all the information you need to duplicate it.

DC

Indeed there was not the interest to go ahead with goaltimate this winter. Too bad because it's pretty fun.

Anyhoo, DC's design is interesting and I hope he takes it to the world and makes a million dollars.

Keep the original caps that come with the water jugs and fill them up at home.
Works a charm. Heavy but it works as long as you're not on a push bike.