Puckdropper's Place weblog

Building: Level vs Flat

Is your site flat? Good. Water doesn't care, though. What water cares about is level, which follows the curve of the earth.

So here's the problem: Our eyes are good at flat but water responds to level. So keep this in mind as you're surveying your rink site. Do what it takes to establish a level line, whether it's with a line level or laser or something else. This will tell you if you should perhaps move your rink over a few feet to avoid a huge drop.

When I sited my rink last year, I could see the ground was flat. It looked close to level, but as it turned out there was a 20" drop over 48' and a 30" drop over 60'. I wound up making rink brackets to handle the load and had to add a few extra rows of boards as I was filling. As it turns out, my laser level wasn't all that far off. (Over 48', a 1 degree error can be as much as 10 inches!)

So when siting your rink, do what it takes to see how level the site is and not how flat it is.

Experiment 2: Fence

An update to this post is available here

Hypothesis:
By putting a fence around the ice rink, blowing snow and more importantly leaves will be kept from the ice, resulting in less maintenance.

Analysis:
Fencing in the entire rink may actually cause more debris to fall on to the rink rather than less. Leaves can blow off of an open rink but would be trapped in a fenced rink. Also, it's possible for a calm area to develop as the fence resists the wind and this would allow debris to drop onto the ice. (See Bernoulli Principle.)

Implementation:
3/4" EMT tubing* was cut to approximately 56 inches. This was secured to the rink boards using two-hole EMT clamps, two per tube. Insulating bushings were installed on the top of the EMT to keep the cut edges from catching on the fencing as it was installed. The fencing is a temporary plastic fence with approximately 1/4" weave. The fencing is not attached at the bottom, so it's a simple matter to lift it slightly and shovel the snow off the rink.

The fencing extends from 2-4" below the height of the rink boards. This is not only to keep debris from blowing under the fence, but to minimize lost pucks when they inevitably skip over the end.

*Any of you "tautology" guys want to argue? Yes, it's Electrical Metallic Tubing tubing.

Results:
One unintended consequence is that pucks sometimes hit the fence and come back rather quickly. One has to watch for this and get out of the way as the puck will often be in the air.

At this point in time, it's difficult to say for certain if the fence is having an effect on preventing drifting and debris. Initial observations look like it's working, but it's hard to tell.

The fence does present additional challenges during snow removal. It has intentionally been kept loose at the bottom, so it can be lifted to remove snow when shoveling. However, clearing snow using a blower has not been tested at the time.

Postscript:
The fence is not intended as puck control, but more drift and debris control. However, it will keep pucks either on the ice or near to the rink so they're easy to pick up later.

Experiment 1: Ice Rink Cam

The Ice Rink Cam is a webcam on an old laptop running Booru software and Windows 7. The intention of the experiment was to determine where the sun shone most on the rink, so maybe I could put up shade tarp and prevent solar gain.

The camera was placed on a dresser next to a window facing the rink. Pictures were grainy and showed the window screen. However, this was good enough to provide an idea of how bright parts of the rink would get.

Photos from about 10:30 AM until around 1:00PM were flooded out with light, I suspect this was light coming in from the other windows and reflecting off this one. However, this corresponds to the time when the sun would be directly overhead anyway and shade tarps would have to be above the rink to be effective.

It proved to be difficult to see the detail of the shadow lines from the house and trees on the webcam, but from what I can tell the area is pretty well shaded with less solar exposure than the previous rink. One thing to keep in mind is that in Winter the sun generally shines farther South, so if the long side of your rink follows a N-S line, shade tarps will be less useful than if oriented E-W.

In conclusion, the success of this experiment was hampered by the quality of the equipment used and a cat who likes to sleep on that dresser. A little useful data was gathered, but not enough to make continuing or redoing the experiment worthwhile.

Dropping the Liner

When do you drop the liner?

Here's the conditions to look for:
1. Calm winds
2. Favorable forecast
3. Cold weather happening soon

Calm winds are self explanatory. You can drop the liner with an infrequent wind, but it's annoying. The wind will catch and blow that liner without much trouble and make things difficult. Wind is perhaps the most likely to affect your liner drop experience.

A clear forecast is a good place to start, but it's possible to drop the liner ahead of some rain or snow and let nature help fill your rink. How much snow? Well, I'd say less than an inch won't bother anything. There's always the risk, though, of getting more snow than was expected and now you'll have snow ice rather than the best kind of ice: clear ice.

What needs to be explained about the "cold weather happening soon" condition is what "soon" means. It doesn't have to be tomorrow, next week might be soon enough. If you're filling from a well, you might even prefer to fill slowly over several days rather than fill all at once. Your water will come out of the ground at around 55-60 degrees and has to cool to below 32F for ice to form. It doesn't matter if the water loses that 30 degrees slowly over several days or quickly over one, it's got to do it.

On the other hand, you don't want a lake for any longer than you have to have it. While we did notice on the Backyard Rink Yahoo! group that rinks that were liquid didn't seem to have any problems, we don't want to encourage them by having a lake for too long. Animals will remember where the bodies of water are and visit frequently. A week or two won't be bad.

So, when you're planning on dropping your liner look for calm winds, favorable weather, and cold weather forecasted soon.

A Minor Change

Since Ice Rink season is here, I'm going to shift my focus to building ice rinks. Eventually, I'll shift the ice rink blog over to the correct section.

Rink Experiments, Theory, and Building

Experiment 1: Camera
The sun has a direct bearing on the thickness of the ice. If the rink is shaded, I'll be able to skate longer without the sun melting the ice as quickly. In order to determine where to place the shade tarp, we need to know which areas the sun shines on most.

By utilizing a camera with a timer to take pictures several times an hour, we should be able to gather this data. A computer webcam and software is being used to take a photo every 5 minutes to observe the solar patterns. The data is being gathered as I type.

Experiment 2: Fencing
A temporary fence with fine enough graduations will prevent blowing snow and leaves from getting on the ice. A second benefit is pucks will be kept in. Think about a drift fence.

Experimental setup: Attach a fence to the rink boards and a second fence on the ground about 5-10' away. The second fence is to stop the majority of the drifts and leaves while the first will hopefully get the rest.

Replacing a Gear, Part IV

Sherline makes a single-point gear cutter for their mill. I've got a Taig mill, which uses a different setup in the spindle. This means I couldn't use the Sherline part, and I couldn't find one for the Taig. So, I built one.

I followed the Sherline design with a few key changes: I made the cutter with a 3/8" shaft so I could grip it in the Taig collet. Since I was making my gear out of Delrin, I used W1 tool steel instead of a HSS bit. The mill had no problem cutting the W1 (once I figured out speeds and feeds) and was used to put the correct profile on the tool. For reference, I put about a 5 degree relief on the tool so the back of the tool wouldn't cut as the tool spins.

Size caused a few issues trying to cut this gear. Since the holder was 1 1/2", and the tool bit stuck out about 1/2", there was a 2" diameter circle that had to be traversed freely in order for the tool to cut. This meant working at the end of a piece of 9mm Delrin, which resulted in lots of chatter. There wasn't enough room for the tailstock to support the work, so I had to turn a much longer center for the tailstock. Were I to do this over again, I'd try to keep the overall diameter of the cutter down to prevent this issue.

At the end, though, I had a pair of gear-shaped objects that ran together quite nicely. Not perfect, but enough to keep the process going.

More on Gears - Checking

When measuring a gear, there's only a couple things the average hobbyist can measure. One is the tooth count and the other is the overall OD of the gear. It's easy to get the tooth count wrong, so if you're looking to replace a gear here's a way to double check:

Calculate a probable tooth size (use a calculator or look up the formula.) Use the tooth size to calculate the pitch circle diameter (PCD) of the gear.

Using a CAD/3D modeling program or anything that will draw a gear and a circle, draw a circle of the overall diameter. Draw a gear of the tooth size and PCD and center it on the circle. The tips of the gear teeth should touch the circle.

Replacing a Gear, Part III

With the other attempts failing, I decided to try making the gear using a milling machine. I already had the file with the gear drawn, so simply used that. I decided 3 milling operations would be best: A rough pass with a large (1/8") endmill for the outside of the gear, a rough pass with a smaller endmill (.6mm) to start the teeth, and a final pass with the smallest endmill (.009" or ~.2mm).

The first and second passes went great... well almost. I broke the .6 mm endmill and decided to use the .8mm in its place without updating the file. At this point, it was more important to see if the process would work than to get all the T's and I's crossed and dotted. No sense in wasting time if something else fails.

Something else failed. The .009" endmill had just a tiny bit of cutting length. Since they're so tiny it wouldn't take much more than looking at them wrong to break them. There was just no way that size endmill was capable of making the cut depth I needed.

After the second pass, I had something that resembled a gear. I'm certain if the third pass had been successful I would have had something that could be driven.

Time to explore other options. There's another approach to milling gears, involving some sort of spinning cutter and turning the gear blank a certain amount to generate each tooth. (Sherline makes one that's similar to a fly cutter, Ivan Law describes one that's a disc.)

As with last time, no idea when the next installment will be, or what the resolution will be.

Replacing a Gear, Part II

I finally got the 3D printed gears. Even though the 3D printing company's software warned me about the tooth size possibly being too fine, I tried it anyway. The teeth did not print correctly, and part of it may be my choice of nylon for the gear. Oh well, sometimes it takes a couple iterations to get things figured out. The bore for the gear was a square, and that seems to have turned out ok. I might cut off the rest of the gear and use the shaft if I can find or make a replacement gear.

I'm not having much luck finding a gear of the exact specs of the old one. It's a small gear, .3 mod, 28T, PCD of 8.4mm. Checking the NWSL catalog, I see several 26 tooth gears listed but no 28T. That doesn't mean it's not available, just that it's not one of the most common sizes.

I may try cutting the gear myself. The trouble with this approach is simply needing the right tooling to do so. Even with a lathe and mill, you still need the proper cutters.

I have no idea when the next installment will be or what the result will be.

Long Range Forecast