First, regardless of whether you have one or two blades on your racer, as you turn a corner, you'll likely end up with some kind of angle or "tilt" on the blades and think that this should help them bite the ice like it does when you're skating.  But you'd be wrong, like I was :)  From a non-physicist perspective, while skating, if you are not gliding straight, you are either on one skate or the other, and usually on one edge of that one skate.  All your weight on one skate edge = GOOD TRACTION.  On any kind of ice racer, you are immediately dividing your weight between 2 or three contact points, and depending on the weight distribution of your racer, you could end up with less that 1/3 of the weight on your skate blade.  1/3 weight = CRAPPY TRACTION.  What happens with not enough weight is that when you go to turn, you basically have a couple little snow plows and they slide sideways on the ice instead of digging in and turning you.  There's an easy fix though.

The Angle

     To the right is a lame graphic of a skate blade's edge.  The black rectangle on the left represents a cross-section of a normal skate blade.  The edge is very slightly concave with small edges on both sides.  This is not effective for ice racers for the reasons listed above, IMO.  To the right is the cross-section of the blade edge that I have found to be effective.  Instead of a slightly concave blade edge, it is ground to a point.  Basic physics tells us that with reduced weight on the blade edge, and a large blade surface area, we have low pressure per square inch, which means low traction.  If we take the same low weight, but now we reduce the blade's surface to a point, we increase the pressure on the ice, and that my avid racers, means TRACTION! :)

     Initially, I ground the blade's edge so that if you held a protractor against the face of the blade's edge, each face was at about a 45 degree angle to the side of the blade.  At 220 lbs and being a sort of agressive rider, I thought that would be good enough, but it wasn't.  I now have it ground to about 60 degrees, and the traction is excellent.  The lighter you are as a rider, the sharper the point's angle may need to be, but 60 degrees per face seems to work all right down to riders under 150lbs.

Grinding the Blade

     "So, how do you put that angle on the blade?", one might ask.  "Well," says I, "that's relatively easy".  Two good methods are a little belt or disc sander, or a pedestal grinder.  You could also use a hand sander or a hand grinder, but it's more difficult to get a nice straight grind.  Just about everyone should be able to get access to one/some of those tools, and if you're building an ice racer, you likely already have one/some/most of the tools mentioned.  You could also build a little jig that holds your blade at the proper angle, and then take it to a skate sharpener and have him grind it too, although you might have trouble finding one to cooperate.  At any rate, again, the important thing is to get a nice straight edge on it, and it doesn't even matter if the point doesn't run exactly down the center of the blade's edge - only that it's STRAIGHT.  Even then, a little waviness isn't going to be instant disaster, just that it won't run as smoothly and efficiently.

Polishing the Edge

     After getting your edge ground, you need to polish all the grind marks out of the edge, especially if you're grind marks will end up being perpedicular to the ice surface.  Remember how the skate sharpener's wheel grinds marks lengthways on teh blade?  Your grind marks have to run the same way, parallel to the blade's ice edge, or lengthwise.  If you don't polish most/all the marks out, they'll act like sand paper or small files against the ice and they can really slow you down.  I know this from personal experience :)  An easy way to smooth them out is to get a whet stone, and use the stone on the blades as if you were sharpening a knife blade.  You don't want an actual knife edge on the blade though.  It can be too sharp which means it will bite too deeply into the ice, and that too can slow you down.  So concentrate on getting all the grind marks out of your blade edges by running the stone lengthwise on the blade edge.  After you're done, you'll likely have a fairly sharp-feeling edge anyway, so use the stone on the actual knife edge and lightly rub it lengthwise a few times until you can run your finger down the edge without fear of actually cutting yourself on it.  The important thing to remember is that the edge will help cut a small groove into the ice when you corner, but it's actually the face of your edge pushing against the sides of those grooves that give you the traction.

Blade Options

     That's all there is to blade grinding. :)  Bear in mind that you don't actually need to use a skate blade.  A piece of 1/8" flat steel works just as well and the edge seems to last almost as well as a skate blade.  The upside is that it's much easier to shape the mild steel than an actual skate blade.  Also, the length of the blade is something else to experiment with.  A shorter blade will be easier to turn because the amount of edge biting the ice is shorter too.  It might also bite the ice better due to a shorter blade having more PSI on the ice, but it might also bite TOO deeply and you might have to change the angle to make it closer to 45º.  A shorter blade might also be a little slower if it has too much pressure or the edge cuts too deeply into the ice not only while cornering but also while running straight.  Still another option to try is to grind a slight curve on the bottom on the blade, similar to a rocking chair, only less curved.  What this does is effectively shorten the amount of blade on the ice but when cornering pressure forces it in deeper, more blade will end up pressing into the ice and reduce how deep it goes, but still give good traction.  Also, a curved blade should help lighten the steering feel and allow the ice racer to be a little smoother cornering.  Something you'll need to experiment with until you find your own "sweet spot" though.

     Lastly, when you try your blades out, out-door ice is usually harder than indoor ice so you may have to modify your egde depending on where you're racing.  If it's warm outside, or the ice is softer, you don't want as sharp a point.  If it's colder or harder ice, you can get away with a sharper point because the blade won't bite as deep in hard ice.  Next, tires . . .

     By "traction aides" I am referring to tire studs or screws.  You can buy commercial bike tire studs and they screw into the outside of the lugs on the tires' treads, usually a knobby MTB style tire.  I have been meaning to buy some and test them, but they are a little pricey when you start considering putting about 500 per tire and for ice racing, you don't necessarily want to use a knobby MTB tire.  Due to cost, availability and experimentation variables, I opted for small screws and washers.

The Theory

     The idea is you want to balance maximum grip (primarily for cornering) with minimum drag and this is bearing in mind that we are racing on ice, not snow, packed snow or snow covered roads.  The best kind of tire, I think, is a smooth tread tire with at least 65 PSI in it.  With knobby tread, you are basically climbing up and down off the knobby parts of the tread as you ride, and this up and down action creates drag and can slow you down a lot, especially if it is a 65 PSI tire or lower.  The same thing happens if you use screws and studs that are too long.  You end up being limited in speed because you have to keep climbing up on teh screws sticking out of your tire.  Lastly, having too many screws in your tire also causes drag because even if the screws are short, you are still climbing up and down on these small screws which causes drag, and more small screws equals more drag.  The design of your ice racer will determine your maximum speed while cornering on the ice track (a skating/hockey rink for us).  For optimum traction, you want to have only enough screws to allow you to corner fast enough that either your steering feels unsafe, or the trike is right on the verge of flipping.  If you are cornering hard and your rear tire is sliding out you obviously need more traction.  Now, deciding whether you need more screws, or just longer screws, that's where you have to experiment.  Lastly, keep in mind that depending on the length and amount of the races and racers, the ice "shavings" will build up and that will also reduce your traction in the corners.

The Equipment

     To the right is a picture of what I use to make ice racing tires, and while you don't need to do it exactly the same way I do, I think the important thing is the screw size.

     I use #6 button head Robertson screws that are 1/4" and 3/8" long.  I also use #6 (or 1/8") flat washers.  Your choice of tire sort of determines how long of a screw you need to use.  Using a small diameter screw means you're using lighter screws and you are poking a smaller screw in the ice, but you can use more screws which seems to mean that more smaller holes gives better traction than fewer big holes.  So, on top of that, I also use a drill to pre-drill the holes, a machinist's scribe and my trusty Robertson screwdriver.  Ideally, you want he screws sticking out about 1/8" and depending on the thickness of your tire, the washers can help shorten the longer screws about 1/16" if need be.  I put the tire on the little piece of 2 x 4 to act as a tire rest.  Some people also use #4 screws but they are harder to find and come in very small packages.

The Method

     The first thing I do is decide where I'm going to put the screws in the tire.  If it is going to be a front tire for steering (on a trike), you only need the screws on the outside half of the tire because that is where the weight and traction will shift to while cornering.  During cornering the inside tire will have less weight and give little traction benefit.  For a rear wheel or the front wheel of a two wheeler, you need to place screws pretty much from sidewall to sidewall.  The top picture to the right are the two front tires for a trike.  The top tire had one row of screws offset to the outside of the tire's center but testing showed that there weren't enough screws to prevent understeer in the corners and the tire didn't roll as much as anticipated because it is 110 PSI and pretty stiff.  The solution was to add a 2nd row of screws on the centerline of the tire, like the bottom one.

     To locate the screws and get an even pattern, I take my drill with a small bit (1/8" or smaller) and drill holes from the outside in.  This not only leaves a small hole that I can see on the inside but helps the screws go through the carcass easier too.  The only thing about drilling is that you need to make sure the hole isn't too big or the screw won't stay tight for long, and you also run the risk of slicing the threads in the tire casing and causing a high pressure tire to bulge out badly.  The small black dots you can see on the outside are identical to the ones you can see on the inside.

The Installation

     Installing the screws is simply a matter of screwing hundreds of little screws into the pre-drilled holes.  I screwed one in until I felt how tight it would go until it felt like it was stripping a little, then backed off a bit, and tried to replicate that "feel" with the rest of the screws.  While I was pre-drilling the holes, my little helpers (my 8 and 6 year olds) wanted to come out and "help build some bikes" so they used their little fingers to best effect and they patiently put the washers on the screws, and stood the screws upside down on the table (as you can see in the top picture) for me.  Not only that though, but the washers had a smooth side and a burred side from when they were punched out and I showed them the burr and asked them if they could try to make sure the smooth side of the washer was against the screw head so they wouldn't cut the inner tube.  They were extremely concerned about a flat tire so they made sure they got every washer the right way up.  Lastly, they helped me like this for about 2 hours a night, for three nights, and they did close to 2500 screws!  I was very impressed with their dilligence and attention to detail.  For the 2007 season, they should both have their own trikes to race if they want to, so it should be a nice little reqard for their effort in '06.  Anyway, it was far, far faster for me to just be able to pick up a screw with a washer already on it and screw it in, than to mess around with my fat fingers trying to get the little washers on myself.

The Complete Tire

     To the right is the completed tire.  I have lots of old tubes that were split or damaged beyond my interest to repair them so I use them to protect the tubes from the screw heads.  Part of the reason why I used the screws I did was because the Robertson socket generally has fewer sharp edges than a Phillips and it is much easier to drive in a confined space than a common.  Regardless, I took an old tube and split it down the middle along the inside edge which is closest to the spoke nipples.  I cut it sort of like how you would gut a fish.  I cut out the valve and then slid the good tube into the one I'd just opened up.   I install the tire on the rim like normal, then I inserted the two nested tubes into the tire, finished putting the tire on and inflated the tube like normal.  Some of the ice racers experienced flats but I had no problems at all, even with 100 PSI.  After a lot of racing, the screws can loosen up a little and some of them actually cut little moon crescents into the "extra" tube by pinching it between the screw heads and the washers.  So if it hadn't been for the extra tube, it would have flattened the tire.  The finished tires are much heavier than normal, especially after putting 500 or more screws into them.

The Evolution

     To the right is a small example of the evloution in our trial and error learning curve.

     The top tire is a 26" 65 PSI MTB tire with a relatively smooth center and was used on the rear wheel of an ice trike.  I used 1/2" #8 screws in it and while it had tremendous traction, it also was a real beast to keep rolling when you got it going fast because it was easy to feel the tire going up and down off the screws.  When you stopped pedalling, it slowed down pretty fast.

     The middle tire is a smooth 26" MTB road tire rated at 85 PSI.  It was used on a FWD trike but didn't have enough traction so three more rows of screws were added, one down the middle and one down each side.  It ended up with over 500 screws in it.  I believe it is the ideal setup and with more careful screw placement, more, smaller screws can be installed, in 5 rows, which will give both great traction and less rolling resistance.

     The bottom tire is a 24" Maxxis Holy Roller and while it has square tread blocks, it doesn't roll too badly considering it is only a 65 PSI tire too.  A 24" high pressure Kenda Kwest would be a better choice though both for tread and for PSI.  The 4 rows of screws proved to be enough to provide all the traction required.  Again, a high pressure tire would have been ideal though.

     The rear tire of the bike in the bottom picture is a 700C road tire with over 700 screws in it.  I'm not sure if the screws are #6 x 1/4" or #4 x 3/8".  The limiting factor with a 2 wheel bike is their ability to corner.  While still very fast on the straights with these tires, a hybrid trike is faster on the corners by far.

     In the end, the two types of racers are broken down into hybrids with blades and spiked drive tires, and all tires with spikes.  If the ice is soft or rough, a two wheeler with spiked tires will be fastest, followed by a trike with spiked tires, and then a hybrid trike and bike.  If the ice is smooth and/or hard, a hybrid trike is faster, followed by a hybrid bike, a spike tired bike, and lastly a spike tired trike.  The design of the ice racer has a lot to do with the ability to get traction too, so you'll need to experiment a bit to find out what works best in the end.

30 Sept 2006

     I had a piece of high density, closed cell foam that was similar to the foam pads on work-out benches, and it is about 6" long and about 4" in diameter.  I took a 6" piece of 1" x 1/8" 6061 AL tubing and about 8" of 1" x ¼" AL flat bar.

     First, I drilled and tapped a ¼" NC hole about 5/16" in from the squared off end of the flat stock.  I cut a notch in the side of the AL tube that was wide enough and thick enough to let the bar slide into it.  I used a ¼" to drill a few holes where I wanted the slot, and then a round and a thin flat file to shape the slot.   I drilled a ¼" hole in the middle of the side of the AL tube that was 90º offset from the slot.  The plan was to insert the flat bar into the slot, use an Allen head ¼" screw to go through the tube's hole, and tighten into the threaded hole in the end of the flat bar.  By tightening the screw, it would pull the bar tight against the inside of the tube and hold it securely.  It worked great :)  The big holes in the flat bar are 5/16" holes to lighten it a little, and the smaller holes are ¼" and will provide 3 height settings for the headrest on the seat.

     Next, I used a utility knife to cut a slot in the foam that was just big enough to allow the flat bar to slide through it.  Then I used a scriber to poke a hole in the side of the foam so that when the foam was slid onto the AL tube, I could push the Allen screw in throught the foam's small hole and screw it into the flat bar.  The second pictrue shows the foam slid onto the AL tube, then the flat bar pushed through the slot in the tube, and the foam, and then the screw being inserted through the small hole in the side of the foam and the AL tube, and tightened into the flat bar's threaded hole with an Allen wrench.   The two small black friction caps are from handle bar grips and they will close off the ends of the headrest when finished.  The headrest was held up to the back of the seat with the rider on it, and the flat bar was marked where it needed a slight bend to provide support in the proper place.  The AL flat bar can easily be bend more or less to suit the rider's preference later.

     The 3rd picture shows the painted and assembled headrest.  I might have changed the lightening hole locations for the benefit of cosmetics, but I didn't want to drill too many big holes lest they weaken the headrest.  Next, it was located on the seat back, the holes were picked up, and ¼" SS Allen head bolts and flat washers were used to screw it to the seat back.

     The bottom picture shows sort of a bad shot of the headrest mounted on the bent. :)  The whole headrest took maybe an hour to make, and cost maybe $15 - $20.