YourMomLikesRollerDerby

Skates typically use two different kinds of bearings, depending on your skates. These two types of bearings are 627 and 608 bearings.

What’s the difference? The hole in the middle that the axle goes through. A 627 bearing has a 7mm hole, while a 608 bearing has an 8mm hole.

Do you need to know which kind you have? Absolutely. Most likely your skates use a 608 bearing. However, if your skates are made for a 627 bearing (7mm axle), you need to use spacers in order for 608 bearings to fit properly.

Most all bearings are rated in a system called “ABEC scale”. In the skating world, this is often referred to as “ABEC rating”. ABEC has nothing to do with skating at all. In fact the bearings we use for skating are often not designed for skating at all. The 608 and 627 bearings were originally designed for use in industrial applications and are very common in sewing machines. The ABEC scale is one that is meant for understanding the precision to which the bearings were manufactured. The ABEC scale is odd numbers, from 1 to 9, though if you look at longboards, you will see ABEC 11 bearings. An ABEC 1 bearing will have parts that aren’t held to the same standard as an ABEC 5 or ABEC 9 bearing. That standard is how far off from specified measurements each part is allowed to be.

It is important to note that 608/627 bearings are very often designed for high-speed applications where there will be very little load on the bearings. Skaters exert a load on bearings that are much more than what is normally intended for these types of bearings. That is one of the shortcomings of the ABEC scale. While it exemplifies the tolerances used in manufacturing, it does not take into consideration the materials used. Sometimes the materials used in an ABEC 9 bearing are softer or more susceptible to rusting than those used in an ABEC 1 bearing. That will often mean that some ABEC 9 bearings may deteriorate quickly and cause poor performance.

That is not to say that ABEC rated bearings are not suited for skating. I also would not claim that the ABEC rated bearings suited for skating are bad; some are certainly great. What I am suggesting is to not fall into the misconception that many skaters fall into. Don’t think that because you see ABEC 9, the bearings are good. It is possible for an ABEC 3 to outperform and outlast an ABEC 9.

There is an alternative to ABEC ratings. There are many bearings that are sold for the purpose of skating that don’t advertise an ABEC rating. These are often referred to as “skate-rated”. These are normally made popular through word of mouth and brand recognition. There is really no standard of comparing these bearings other than trying them out and seeing for yourself.

So how do you pick out bearings for your skates? Ask around, look for reviews online, maybe even buy a few sets and try them out.

If you try several sets out, be aware that there is a break-in period. This period will be different depending on the bearings, but is normally not much more than a couple hours of skate time.

I have a few suggestions for selecting bearings based on my personal experience and that of others around me:

Stay away from BSB and KWIK bearings – These brands make bearings that often never spin freely, or they break down quickly.

For a good mid-range bearing, I like Bones Reds. These are excellent bearings for the price ($30-40).

For a much higher end bearing, I can’t recommend ILQ-9 bearings by Twincam highly enough. After switching to my ILQ-9 classics, I believe I will be skating on ILQ-9 bearings for the rest of my life. The classics are available for $36, the pros are available for $45.50 and the BCBs (ceramics) are available for $195. The BCB bearings actually come with a lifetime renewal program and a set of classics for when you’re having your BCBs cleaned.

All of the above mentioned bearings are  608 bearings. For 627 bearings, you’ll have to ask around for advice.

This weekend, I had the pleasure of reffing the Atlanta Dirty South Derby Girls vs. Steel City Steel Hurtin’ bout, as well as the ARG intraleague Apocalypstix vs Toxic Shocks bout. This was going to be the first time I would get real world experience with the Tachyon XC helmet cam. Let’s pick up where we left off.

I received my replacement camera pretty quickly. I went to attach it to my helmet and had many issues. I was finding no way to securely mount the camera. I emailed Tachyon, Inc. asking for mounting advice. As I sit here writing this, I have still not received a response.

I eventually decided to use one of the provided mounts with a combination of the velcro and elastic strap (both provided). The elastic strap had to be wrapped around the mount and through holes in my helmet many times in order to keep it from bouncing too much. I would not call it a very secure mount. I spent close to an hour trying to get it aimed properly. I then put it away until we got to Atlanta.

When it came time to use the camera, the beeping to let you know that it was turned on and then to let you know recording has started was not loud enough for me to know if the button presses were accepted. The venue was fairly loud, but the camera was only a few inches from my ears. This wouldn’t be much of a concern if the buttons weren’t so difficult to press and need to be held down for a few seconds before the button press registers. This was a design choice to prevent accidental button presses and to keep the camera waterproof. Because of this, it almost hurt to push the buttons as hard as necessary and the button presses still don’t always register. This difficulty would be fine, had I been able to hear that the button press had registered. It also would have been fine if it had not been for the next problem I ran into.

The camera has two led lights in it. There is a green led to indicate the unit is powered on and a red led to indicate that you are recording. I had explained to other people how those lights work. I was randomly told that the light was green, when I knew it should have been red. In other words, the camera randomly stopped recording. Sometimes it would stop after only a minute or two; sometimes it would be 20 minutes later. The only way that I could tell that the camera had stopped recording on its own was to either take off my helmet, or have someone tell me.

So before the event was over, I was fairly dissatisfied with the camera. That would only be the beginning of my disappointment, as I had not yet seen the resulting video.

I connected the camera to my laptop to take a look at what I had gotten. The first thing I noticed was that the image was quite grainy. The low light performance was poor. The venue where the bouts were located wasn’t very bright, but I still would have liked to see a better picture in that light setting.

The next thing I noticed was the sound. It was totally unacceptable. I had expected poor sound due to the waterproofing, but nothing like this. The sound was cutting out probably once or twice a second. More than that, during one-on-one official reviews, you could barely even hear the person I was talking to or myself. What you were able to hear, you couldn’t even tell who was talking.

Also, the video isn’t worth watching because my mount went totally out of calibration. It was aimed too high. When I was looking down at skates, the camera was looking at the top of helmets. It was aimed too far in front of the skater I was watching, but this was probably due to my own miscalculation. If the mount had been more secure, it couldn’t have shifted as it had.

In closing, the only thing that I like about this camera is the construction of the back of the camera. The back door latches securely, which makes it feel like it was well engineered. The battery compartment made me feel confident that the batteries would not become dislodged during use. Outside of that, the camera is not worth anywhere near what I paid for it. If I were to put a price on the Tachyon XC (without memory card), I wouldn’t pay more than $25 for it.

Bearings are these sealed metal rings that help your wheels spin and there’s some “ABEC” thing with numbers. The higher the number, the faster they are, right?

Well, at least that is as far as the knowledge of many derby skaters goes. Bearings are a very important component of your skates, but are often taken for granted. They perform a simple task; they help your wheels spin with a minimal amount of friction to the axles. What you don’t see of the bearings is what does all the work, balls. Yes, my balls do all the work in my bearings.

Seriously though, your bearings contain 6 or 7 ball bearings. 7 is more common until you get away from ABEC rated bearings, 6 is more typical of high quality bearings. Before I go too far with this thought, lets talk about the details of the construction of a skate bearing.

When you look at your bearings, you generally see three parts. These parts are as follows:

Dust cover/shield – The part that has the part number and/or ABEC rating imprinted on it. Inner raceway – The ring that touches your axle. Outer raceway – The ring that touches your wheel.

It probably goes without saying what the dust cover/shield does. There is a difference between a dust cover and a dust shield though. Some bearings have only dust shields, while others have both. A dust shield is a metal plate that protects the inside of your bearings from dirt, dust and to a lesser extent, water. Dust covers do the same thing but are thin plastic. What’s the big difference? Dust shields provide an extra bit of protection from impact to the bearing, dust covers don’t. If you have bearings with dust covers, these covers should be facing inward in each wheel. In other words, they should not be exposed once you have your wheels on.

Raceways are a critical part of bearings, in that if machined with imperfections, it can greatly affect performance. Raceways are just metal rings, the full width of the bearing that have groove cut on the internal surfaces. These grooves serve as a track for the ball bearings to roll in (we’ll talk more about this in a moment). They also help to trap the ball bearings.

Most dust covers/shields are held in place with a metal retaining ring against the outer raceway. If you remove this retaining ring, you can now remove that dust cover/shield. You are now looking at the inside of your bearing. Chances are, it’s pretty disgusting looking. It will be filled with lubricant and any debris that may have made its way inside. Besides that nastiness, you will see the ball bearings and a metal (there are some bearings that use some types of plastic for this) ring that is bent around each one of the ball bearings. If you look closely, you will notice the flat areas on this metal ring in between each ball is the same width. Those flats are the key to the primary purpose of the ring. What I have been calling a ring is actually two rings (one on either side of the ball bearings) that are linked together in some fashion. This part is called the cage and its primary purpose is to create the appropriate spacing between ball bearings in order to prevent jams.

I’ve mentioned the ball bearings many times. These are simply metal (with certain exceptions) balls machined to be as close to a perfect sphere as possible. Believe it or not, machining a perfect sphere is something engineers have been struggling with for a very long time, so as close to perfect as possible is what we get. As these balls roll, any imperfections in the surface of the ball, or unevenness in the machining will create chatter. What I mean by chatter is it will roll roughly every time that spot hits the raceway. The more chatter in your ball bearings, the more friction it creates.

Now that we have talked about all the parts, lets put it all together.

The outer raceway is seated tightly in your wheel. It has the dust covers/shields mounted firmly to it with retaining rings. In between the dust covers/shields are the ball bearings inside their cage. For you math geeks, here is how you can understand how a bearing stays together:

X = radius of inner raceway at the bottom of the groove

Y = diameter of one of the ball bearings.

Z = radius of the outer raceway at the bottom of the groove

X + Y ~ Z

The reason for the approximation is that there is a certain amount of slack that varies depending on the tolerances the manufacturer was following.

Because the raceways have a track, the edges are raised. With the space allowed for the ball bearings, they are unable to roll out from between the raceways. Likewise, the inside raceway can’t simply come out.

Now, the inner raceway is tight against the axle and the outer raceway is tight against the wheel. As the wheel rotates, the outer raceway rotates with it. This forces the ball bearings to spin with the rotation of the outer raceway, also rolling in the opposite direction in the inner raceway.

The idea is that all the friction created is a smooth rolling friction. If there are imperfections in the ball bearings, there will be some bouncing or sliding friction. If the friction created is not the smooth rolling friction I described, it requires the skater to work hard to gain and maintain speed. It will also speed the degradation of the bearings.

In the next part of this series on bearings, I’ll talk about understanding ABEC ratings.

An additional, easier formula for the math (stats) geeks to understand how bearings are held together is this:

X = internal radius of the outer raceway at the thickest point

Y = external radius of the inner raceway at the thickest point

Z = diameter of one of the ball bearings

X – Y < Z

My last post about helmet cams ended with my first impressions of the Tachyon XC helmet camera. Basically, it looked like a very solid choice.

Last night I took the Tachyon XC to practice with me, along with my laptop to check the results. I was setting up the side mount, having trouble to get it aimed in the direction that I was hoping for. I finally got it in a position I could live with, when one of the most simple (but critical) parts of the camera failed.

The camera has slots on the sides to slide into the mounts. At one end of the slot there is a notch that locks the camera in place inside the mount. I went to slide the camera back into the side mount. No click. I tried the other mounts. Same thing, nothing keeping the camera from falling out other than friction. Upon closer inspection, I notice that the notch was now gone. This is the only way that the cam can be secured, which makes it useless for its intended purpose.

Also, after trying to use them, I found the supplied mounts to be wholly inadequate. There is a side mount for a helmet included, though it is intended to slide onto the strap from goggles. If you want to attach it directly to the helmet, your only option (without modifications) is to use the supplied velcro. The velcro is more than strong enough to keep the mount and camera attached to the helmet, but allows for an unacceptable amount of bouncing. There is a way to mount the other two mounts with velcro to the top of a helmet, but I didn’t get a chance to see if that would alleviate the bounce very much. I want to reiterate , there is no other included method to attach to a helmet than velcro.

I wrote an email to Tachyon Inc, after getting a voicemail message saying to contact them by email. It was probably worded a little stronger than necessary, but hey, I was angry. I got a response a little more than 12 hours later. They were very polite and agreed that this camera was definitely broken. They want me to ship the camera (not the mounts or accessories) to them and they will ship a replacement. They also told me that there is a “new mount that [they] feels corrects any deficiencies in [their] original mounts”. They said it has been shipped out to all of their customers and I should receive it soon.

So now I have to find a box to package the camera in and take time out of work to go to a post office. I’m hoping that I just got a defective unit, but I don’t have a whole lot of faith in that. If it turns out that this was just a fluke and I got the rare defective unit, the mounts I have can be altered easily to be very secure.

Also, the video was exactly what I was expecting. Considering the average quality of all-in-one helmet cams and the lighting conditions in our space, it was definitely good enough for my purposes.

I’ll keep you updated on my findings of the replacement unit.

One of many tools that help a referee learn how to implement the rules is video footage. More often than not, that footage was filmed with the fans in mind. This makes for exciting video, but isn’t always the best way for a ref to learn from it. Because of this, I have wanted a helmet camera for some time now. The idea is that the helmet cam will capture as close to what I am seeing as possible. This will keep the focus on only what I need to focus on in whatever reffing position I am working.

This should be an especially good tool for jam refs in training. The camera will remain on the jammer I am watching at all times, making it easier to judge how many points the jammer should have gotten.

Because of this desire, I have done much research on helmet cams. There are several different types, ranging from $80 to $1000+. The two most common types of helmet cameras are all-in-one (the piece that is attached to your helmet does everything) and a bullet camera + DVR. The latter uses a camera (basically just the lens and processor) which is attached to a Digital Video Recorder by a wire, which records the video to a hard drive or other media.

There are pros and cons for each.

The bullet cam +DVR combo can provide much higher quality video and puts the weight in your pocket. Though it also requires a wire to be routed from the camera to the DVR, which can be damaged somewhat easily and can get in the way.

The all-in-one cameras eliminate the wires and tend to be less expensive. However, they produce a lower quality video and put all the bulk and weight (mostly batteries) on your helmet.

For me, the decision between the two types was an easy one. I didn’t want to deal with wires. So then the field was narrowed to basically 3 different cameras. The GoPro HERO (which looks like a mini digital camera), the Oregon Scientific ATC-3000 (I believe the link leads to an ATC-2000, but they are very similar cameras) and the Tachyon XC.

The GoPro camera wasn’t even worth my time since the maximum it can record is 56 minutes. Not even enough to record a single bout.

The ATC-3000 shows a lot of wavy distortion during high motion activities. The sound quality is bad enough that you might as well not even waster the storage space recording it.

The Tachyon XC was the clear winner here. It has a similar form factor to the ATC-3000 but without its video problems. The sound is not a whole lot better than the ATC-3000, but it is better. At $230 including a class 6 16Gb SD card, it’s a steal.

Upon receiving the Tachyon XC, I was very impressed with the variety of mounts included. There are included velcro sheets, perforated in different shapes to accommodate many different types of mounting methods. The door on the back that covers the battery compartment, memory card slot, video and usb connection is difficult to close. That difficulty is part of what impressed me; the latch very securely closes the compartment and completely seals it off, preventing water or dust from getting in. The whole thing seems extremely solid and well-made.

I’ve yet to figure out where it needs to go on my helmet, so I haven’t gotten a real-world test yet. When I do, I will post a full review.