Hi Trikes!
Welcome to our board - I've been pretty busy with work recently and haven't had time to reply to everybody's posts... but anyway, I am really interested in what you guys are up to on your side of the planet - especially that mad looking half-dragon-half-trike thing that you are riding! (That helmet of yours is losing me sleep though
)
Anyway, to address your luge questions - Please see my earlier post further towards the beginning of this thread for my theories on double front trucks. Alternaitvely, you can view a nicer version of the same post on Joel's shiney polished-looking website here
www.gravityking.co.uk/tech/front_trucks.htmAs for luge weight distribution - well, thats an interesting question that we've not really addressed here before:-
I'd say that about 99% of all luges will exhibit quite a heavy forward-bias weight distribution, this is mainly because for a well designed luge that will handle nicely, it is important to get the front trucks tucked up as close to the rider's butt as possible. (but not actually
under the rider's butt, as this would jack him up too high into the air, thus causing drag and instability).
By default, this means that the front trucks will carry a lot more weight as they are closer to the majority of the rider's body mass. The rear truck tends to be mounted just behind the rider's head, where is does not bear much weight at all. It is also important to rmember that when actually riding a luge, only a very small amount of time is ever spent in the fully-prone position, with he shoulders and head flat on the board. Every corner requires different weight shifts and body positions - all of which are pivoted around the rider's butt.
This forward-bias weight distribution is achieved by default, as it is dictated by the geometry of a well designed luge:-
When riding a luge, the majority of the steering input forces come from the rider's hips, as the rider will pivot pivot their upper body and legs around this one position. With the front trucks mounted as close to this point as possible, you get a really nice positive steering response as the steering forces from the rider's body are transmitted directly down through the hips to the front trucks.
If you try riding a luge with the front trucks mounted furhter forward,
away from the rider's butt, you will immediately notice how sluggish and unresponsive the steering will feel. Likewise, if you were to put this sluggish and unresponsive luge (plus rider) on your scales, you will probably see less of a forward weight bias, as the riders weight will be suported more evenly between the two ends of the luge.
When considering weight bias for a luge, it is important to remember that luges are
not cars, and a 50/50 "sportscar" setup simply does not work at all on a luge.
In terms of
grip on a luge, almost
all of the gripping forces in a heavy corner are handled by the front trucks, the rear truck is simply a neutral pivot for them to turn around. The rear truck des not do much steering, or carry much weight. All it has to do is sit there and prevent the back end form scraping along the road.
People have tried running a looser rear truck before, in an attempt to make it a more "active" steering element, but all it causes is instablilty at high speeds, and handling like a forklift truck through the corners.
Buttboards are a differnt kettle of fish altogether. The IGSA buttboard construction rules dicatate that only two trucks are allowed, and the board cannot be "dropped" between the two trucks. They are also restricted in length, width, and there is also a minimum ride height rule.
Here is a nice photo of Matt "Team Poland" (Left), and Len "The Luge" Stocker (Right) showing off their buttboards. Matt's is a simple deck cut from a sheet of flat plywood. Len's however, has a concave across its width to make it a bit more comfortable, and to help stay onboard a bit through the corners. (Not that there is ever any time to get comfortable during a buttboard race!). Both riders incedentally, are using British "Holey" trucks.
Altogether, this formula creates a highly entertaining and competitive class to compete in. Do not be put off by the slightly un glamorous title of "Buttboard", as buttboard racers are some of the toughest around. The buttboard riding style is quite different to that of a luge, as without handles or sculpted body pans, the riders must radically shift their weight around and literally scrape themselves along the road in order to get round the corners.
Here is a good shot of Will "Bogbrush" Stevenson demonstrating the high-art of buttboard styling.
Carrying significantly less weight than a luge, buttboard riders tend to enter corners at much higher speeds, because they know they can brake a lot quicker than luges, but unfortunately they have less momentum to carry them round the turn, so high speed cornering is important on buttboards!. Because of this, buttboards tend to be ridden right on the ragged edge of control, with spectacular four-wheel drifts round the corners. Admittedly they might not have quite so much straight line speed or stability as a luge, but this rarely detracts from the sheer entertainment of riding one.
A buttboard would still have a front-bias weight distribution, as the majority of the rider's mass is still carried through the hips onto the front truck, but perhaps it would not have such a radical forward bias as found on a luge. Buttboard riders still set their front truck up to perform the majority of the steering, and again the rear truck tends to be quite neutral.
As to which is the fastest - Buttboard or Luge? Well, it all depends on the course really. Tighter, more technical courses favour the buttboards as they can be chucked around the tight bends easier - While faster, open courses favour the luges, where their straight line stability and lower profile carries them to higher speeds than the buttboards.
Here is a good demonstration of this point:
Last year at the Swiss World Cup, in my quater final race, I came up against two other luges, and a Frenchman riding a SC8 buttboard that had been hastily modified to allow it to run in the luge class (They had extended it with foam padding). Photo below shows a "standard" SC8 buttboard. (See their website for more radical French wooden creations :
www.sc8.fr/
I had a chat to him before the start, and his theory was that the road we were racing on favoured the buttboard. (The Swiss World Cup was held on an extremely challenging and technical road - See map below:)
The course combined both technical bends, with flowing link-sections, but overall I'd say that it was more of a technical course than a top-speed contest. However, in terms of qualifing times - there had been little to separate the luges from the buttboards, so overall it was a fairly even match.
Anyway, the race started and we all piled off down the hill. I was last off the line (as usual!), and as we went through the first hairpin I could see the pack spreading out in front of me.
A Swiss luge was leading, followed by the French buttboard rider, followed by another luge, and then me in last place.
I needed to make my way up to first or second in order to make it through to the semi finals, so I passed the third placed luge in the second corner, and dropped him for the rest of the race.
This left one luge in pole position, followed by the buttboard ahead of me. As he had predicted, he was faster through the turns, but I reeled him in on the fast sections in between. I had to get past the buttboard, but the road was difficult - and there were not many safe overtaking points between the hairpins where I could get a clean pass on him.
So I had to sit behind him for corner after corner, turn after turn, waiting for my moment. I could see the guy was nervous, and he very much aware of my luge breathing down his neck. Every corner, he would flash a look behind while on the brakes, to see how far away I was.
Meanwhile the pole placed luge had shot ahead of us both and had a clear lead over both me and the buttboard guy.
Anyway, I had decided by the 4th hairpin that I would just have to wait and overtake him on the final corner - A high risk strategy, as if I stuffed up, I wouldnt get any second chances.
The entry to the last corner was extrmely fast, coming out of a long flowing high-speed section, straight into a mild chicane before opening out onto the final hairpin. The chicane was extremely desceptive, as at a moderate speed it was a breeze to negotiate, but when taken flat out without braking, it was a mind-warping test of nerve.
Buttboard guy did a spot of one-footed panic braking on the way into the chicane, as even his high-tech SC8 buttboard did not have quie enough high-speed stability to let him take it at full speed and still maintain control.
I knew that my luge however, had the grip, momentum, and stability necessary to negotiate the chicane at full speed without braking, and it was just a matter of keeping a cool head and trusting the luge in order to make it through in one piece - so as soon as I saw his foot go down, I knew I had him....
He exited the chicane ahead of me, but with less speed and momentum than I had, so as we plunged down towards the final hairpin I took advantage of the slingshot I had gained from the chicane - and I went for the inside and passed him on the brakes going into the corner.
Also, the exit of the last corner was open and flat, and very dusty - not a lot of grip. With more momentum, and better grip, I was able to run a faster line and carry more speed through the turn, to keep me ahead until the finish line taking me to 8th place overall.
This one descent for me was the highlight of my 2006 season, and I can still vividly remember every twist and turn of the course, and most importantly - passing that French buttboard rider!
So there you have it Trikes - I hope this has answered a few of your questions, and I hope you will go and build yourself an awesome streetluge (or a buttboard!). But before you start building, I'd advise you to build to a design that has been tried and tested before going for any radically unusual designs. Simply because it will give you something safe and predicatable to learn to ride on. Once you have got the hang of how a luge really handles when you are on it, then you can start to experiment...
.
I can see that you are a skilled constructor, and I hope to see some interesting luge stuff coming from you in the future. (Go on - make a GRP luge fairing!). In the meantime, we are here to help.... GO! BUILD!
Ride hard, Stay safe.
P.S. Make a buttboard for your daughter, it'll be lighter and easier for her to handle while she gets the hang of riding the thing...
P.P.S. As for the headfirst luge - I know Curtis Head, and I've seen him on his "Skeleton" luge. It is an admirable but mad-cap exploration of head-first riding, but it is ultimately flawed by the braking method.
However, in America - your average luge-run does not involve that much braking as they tend to ride quite open flowing courses, as afforded by the big wide roads in America. The only braking really needed tends to be after the finish. As such, in the past, American luges tended to reflect American cars : Big, heavy, not great round corners. There are some noticable exceptions however, such as the Rogers. Bros. designs, but even these tend to be favoured only by those few cometitive riders prepared to travel beyond the US, and compete abroad in the World Cup series. Likewise, I doubt if Curtis's head-first board has the braking capacity to be able to challenge any of the exciting technical courses, without the constant fear for shortening your neck...
Now, there is a Frenchman called Claude, who has solved the head-first braking problem, and he builds Skeleton luges that are both fast, safe, and manouverable. He calls them "Skull-boards", and his website is here :
www.skullboard.com/. His boards are fexible along their length, and the rider can use his body to flex the board downwards when he needs to brake, which brings a rubber skid-pad mounted on the belly of the board into contact with the road, thus applying the "bakes".
This is
highly effective, and he can brake better than pretty much any other rider on the hill. I have had to swerve round him on a number of occasions to avoid a collision when he has braked in front of me. They look unconventonal, but are extremely simple. He has solved the braking problem without resorting to any unnescessarily complicated braking systems.
There are skateboard trucks available with mechanical braking systems - "Brakeboard" etc... but none are really satisfactory methods. I've ridden a "Zinger" luge fitted with a mechanical brake system, but it suffers from the inherent problem of flat-spotting your wheels whenever the thing locks up (Which happened quite a lot). Pretty much all of these mechanical braking systems are aimed at the toy-market, and none are really race-worthy. And anyway, on a luge - whats wrong with using your feet? It works!
) handles of yours, and join them to the top of the chassis rail somewhere near the front truck? (The link would pass under your legs). When I say 'link' I'm talking about a piece of bent tube lashed to the chassis rail at the middle, and plugged into the handle tubes at each end. (Could be something dead simple - like a bicycle handlebar, bent / modified to fit?). You could use U-bolts to hold it in the middle, and use some imagination to join it to the handle tubes at each end? (And I dont mean holding it on with stickers.... ;D)
).
and thanks for the update. I really must get my buttboard out the shed this year ! Just had to move it out the way, so I could get at the pile of firewood.......