Bod Rodz Speed Sled

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Postby trikesrule » Wed Feb 13, 2008 2:03 am

Furlong the #6 headrest is aerodynamically incorrect as in the taper is way too steep. Tapers leading off at the rear should not be any steeper than 9 degrees other wise the air becomes turbulent. Going forward the air is already turbulent because of his shoulders. But (going to the front)the rider and luge is in 'dirty air' because of his flat soles shoes. Then the cuffs of his shoes may or may not add to the problem. Sometimes a ledge can actually clean up an aero problem. But as there is no smoke trails wool tufts or pressure readings available we can only surmise that they are adding to the bad aero. His drag tail starts from the front and at 50mph is about 2 1/2 times the size of his shoes (not great) but that appears to be the norm. Unfortunately thats the downfall of the pegless style. Boom luges have an advantage over pegless but I haven't seen anyone take advantage of the 'grey' area in the rules and build a aero correct front fairing that ones feet slip into. I guess they put that in the too hard basket. Actually it's a bit of a challenge. The other thing is it's only going to come into play from 40mph and up(!) then it's a case of slowing down. So is it worth it? It's a whole big can of worms. .......trikes
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Postby DrNo » Wed Feb 13, 2008 7:17 am

Still looking for those shots.

Furlong, my intent is to see how I came across them first before I share them. I had received pics from one of the guys at one time and if this is the case I will not share without their consent, that wouldn't be right.
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Postby ChrisMcB » Wed Feb 13, 2008 8:58 pm

trikesrule wrote: Boom luges have an advantage over pegless but I haven't seen anyone take advantage of the 'grey' area in the rules and build a aero correct front fairing that ones feet slip into.


I'm not sure what grey area you refer to, but this board would be illegal by IGSA rules.

A) nose cones in FRONT of the rider's feet.
B) No part of the luge may present obvious trappings, ...
C) No "Toe loops" allowed.
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Postby CowboyDan » Wed Feb 13, 2008 11:04 pm

The rules state "Bodywork, nose cones in front of the rider?s feet and tail cones behind the rider?s head and fairings are allowed." The trapping and toe loop rules would just dictate that the fairing would have to end before your toes.

trikes having such a gentle angle on the rear fairing would be difficult... the luge is limited to 3m, unless you're 4ft tall you'd struggle to fit within the fairings :)

Then again, if you're solely trying to bust a certain speed are the rules really important?
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Postby stevefernando » Wed Feb 13, 2008 11:45 pm

Does anyone from the old days have pictures of the guy from Lake Tahoe in his teflon aero-suit? Now there was an idea... I think his name was Garret?
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Postby trikesrule » Thu Feb 14, 2008 1:08 pm

About two years back I started making some aero panels for a chaps Luge but never got round to finishing them off as he needed to the luge back so he could use it. Still have the rear one but scrapped the front one as it traps the front feet. And yeah it is difficult but not impossible to tidy up the air at the rear cause when you actually get it up in front of the fans one dosen't need as a large a rear fairing as one thinks (we'll talk about it at NPG). The real gains (and challenge) is up the front. The nose I now have in mind is a definate step forward without the trappings. As I said earlier the traditional Luge drivers head is basicly in 'dirty air' so tail fairings wouldn't do very much at all except add weight. To go faster at the rear one must first fix the aero problem at the front and there is a little problem with the hands but it would be posibble to turn the aero thing off the hands into a Vortex Generator. This is better than going turbulent. I see a few guys sort of like tilting their knuckles forward. Thats the wrong way. They should be leaving their knuckles straight up and down as it's more important to get the air around rather than over the top. It's all got to do with pressure gradients working to minimise the drag tail by tending to the aero shape of anything facing forward..........trikes
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Postby SMRTIC » Thu Feb 14, 2008 9:34 pm

Hey Trike,
So what do you think of this approach? I kinda agree with most of your observations, but I firmly believe it is more important to close the air behind you than to punch a clean hole in front of you. I do have a project with both coming together though. I was told that the sled pictured was very good at closing the draft behind it.

Image

Image
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Postby trikesrule » Fri Feb 15, 2008 12:18 am

Bill how do I blow those pics up. I clicked on them and they didn't grow. And would you have a pic from above? I've looked at one of your Luges on FastEddies site I think it was. They look pretty good but I didn't analize the aero aspect of the luge and driver. Carbon fibre Luges or just the body Bill? ...........trikes
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Postby CowboyDan » Fri Feb 15, 2008 1:16 am

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Postby Rafa88 » Fri Feb 15, 2008 5:18 am

[ben] wrote:Was it anything like this?

Image


thats not a sled, that is a space shuttle
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Postby SMRTIC » Fri Feb 15, 2008 7:13 am

Trikes,
There are more pics and info here


http://www.street-luge.com/phpbb2/viewtopic.php?t=116
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Postby A Lally » Fri Feb 15, 2008 8:27 am

Hey Bill,

Drop me an email when you get a chance. I keep getting bounced back from you. Hope all is well.


Im off to the track in a few minutes, crazy night ahead :-)
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Postby trikesrule » Fri Feb 15, 2008 10:15 am

Hi Bill I'll have a closer look at Bathurst as ths shot is abit far away for me. So apart from the obvious up the front (shoes). Hold up lets talk about shoes in a new Post soon as I've come across something that may well help in that department (especially for pegless). So what do I see. I'm looking at the area where you rest your head. Specifically the the way the air comes down off the shoulders. Raise that area up so as the air transition stays reasonbly smooth. That'll mean possibly having a straightline high speed only luge as moving your head off the board will be difficult. The pod at the back is that made of softish material.? Anyway I'd round the corners off (thumb size) then have a 19 degree welcoming area for the air about 2" long then taper off at 9 degrees. When you've gone to your length that you want cut it off square. That'll create a small vaccum area and if you put a small Vortex Generator on top that'll induce the air to fill in behind you. Basicly you will be controlling the way the flow reattachs / realigns itself after the Luge and driver has gone thru. I can get a pic of a VG on my cart if you'd like to have a look. With the gravity racing I've done there is a lot of emphasis on minimising pressure changes from front to rear. John Rogers touched on the Centre of Pressure position in an article elsewhere (which I haven't read yet) which indicates he understands there is something to it. We've gone off topic (sorry mod) here. We should start a new Post just for aero..........trikes
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Postby [ben] » Fri Feb 15, 2008 3:03 pm

trikesrule wrote: Tapers leading off at the rear should not be any steeper than 9 degrees other wise the air becomes turbulent.


That means that a rear fairing one foot tall would have to be almost SIX FEET LONG to be effective!!! Something that long would bottom out on a road without extremely smooth grade transitions.

What would a good compromise be? Even at 12 degrees, the fairing would still be 3.5 feet long.
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Postby bobswartz » Fri Feb 15, 2008 4:33 pm

I should not even be doing this since I have to much to do in the mad science lab, but I felt the need to chime in..

It is I that wrote the dissertation on Center of Pressure in regards to the dangers of riding luge over 80 some mph. Many theories, mine and others have been proven and disproved with my Jet Luge venture and the need to do it fast and safe. I have access to Wind Tunnel software simulation now and then and the means to occasionally test the theories in real life at very elevated speeds. I have no problem openly sharing the safety info, but I need to keep some of the speed things to myself for a bit longer. I will share the following though.

1. In post analysis the Bod Rodz speed record sled was well build by an aircraft metal expert and mechanic. It had alot going for it, but experienced the center of pressure / COG shift in real life and real time. Causing a pretty sick accident.
2. Everyone spends all their time trying to make the luge faster with "trim" I will call it, when the far bigger drag factor is the rider. It is almost like adding fairing to a school bus. Feet , hands, helmet, legs and such present a nasty front to the air. As trike was saying... tail feathers do little to clean that up. Again it would be like putting a cone on the back of a bus.
3. Workable and practical tail cones and cleaning up the rear air in anyway, may not make you noticeably faster, but it can knock down the draft you leave to a minimum so your opponent has a more difficult time draft passing.... this will make it seem faster if no one can pass.

I have riden behind many luges with "rear draft effects" I will call it. Bill's luge knocks down or redirects the draft (negative pressure in rear)pretty good, but it is still there. I felt it. The weird thing is ,the rear fairing that I think he made for Stacey. It was less aerodynamic to the EYE and a bit ugly in shape but it flat out worked... It was the first time I could not find the draft on a luge 1 foot away and at 55+mph.. It was freaky. I ended up over taking, but it was only because of my patience and body mass.

The long white aero looking missile luge belongs to Ross Bradbury (sp) from Canada, That was his entry in the Guinness run in brazil. He sent me a picture and was disappointed when I told him to take that stuff off, because no aero device was going to make him faster that Dave Rogers on that hill. He didn't believe me citing Dave age was going to be his downfall.. (young punk). I told him that worrying about all those panels (care, adjustment, bumps, grinds,length, making turns) was going to take him off his mental game of racing. I have not talked to him since the race, but I saw a few pictures of him racing without the tail feathers... and I am not sure why... could have been rules or transport destruction. Again my point is the mental game and experience is even more important than the gear. That is why the Rogers Bros, Bill Smrtic, Tom Mason, Andy Lally, Darren Lott, Grumpy and John Fryer (the older more mature riders) are faster no matter what gear you invent to run against them.

For the purpose of these discussions you need to keep focus on the intend of your mods. Mods for top speed, do not directly equate an all around competitive luge and typically cause new problems. Mods for Top speed can also put you into a new realm where a luge as you know it is no longer safe.

Last point to ponder... The typical teardrop airfoil it seems people are trying to create will always be a tough fit on luge since the general form is 180 degrees the wrong way... That is why the old skate cars were head first..... don't go there please...

Do you want to be a fast luge racer? Work on these things in order.
1. Seat Time....... ride race ride race, practice practice with people that are better than you, even go to a racing school if you are committed.

2. Work on YOUR form. (don't be a bus)

3. Play with speed toys on your luge for the remainder 5% of the speed quotient.

Oh yea..... if you don't put safety first.... you cannot do steps 1 2 or 3 for very long.

Have fun and be safe
Bob
Last edited by bobswartz on Fri Feb 15, 2008 5:52 pm, edited 3 times in total.
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