A question for our Zen Carver

Board building, design, technical innovations and new equipment. Post and discuss your latest creations, ideas, designs and builds here(Pictures not required LOL)

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sk8norcal
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Post by sk8norcal » Thu Jun 03, 2010 9:31 am

BgSurfer wrote:I don't believe I said, anywhere in this thread, that gyroscopic effect improves stability with speed. You have dredged up something from 12 months in the past.

However, in concert with trailing, I suspect gyroscopic effect does play a major roll in side-to-side tipping on a bike or dirtsurfer. Minor instabilities affect "human balance" on an unsupported, stationary bicycle. Once again human reflex creates corrective response, often an over correction for issues of balance. While not great, increased rpm increases gyroscopic force. Added to trailing, that increased gyroscopic force, keeping wheels upright (resisting tipping), could significantly contribute to stability as speed (rpm) increases by damping side-to-side tipping and therefore the human reflex response (feedback loops).

Anymore, I will not respond to "discussions" from the past on this thread.


okkkkk, so you changed your mind on your previous theory about the 3 wheeler.... :rolleyes:

this new theory sounds like a revision of the old theory...
which I believe is wrong too...

its just what I believe, no need to get upset... :p

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sk8norcal
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Post by sk8norcal » Thu Jun 03, 2010 9:36 am

for those interested,
look up the book "Bicycling Science",

there is a chapter in there on balance and steering...

http://www.amazon.com/Bicycling-Science-David-Gordon-Wilson/dp/0262731541

(god forbid no, another link!) :D

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Post by BgSurfer » Thu Jun 03, 2010 11:37 am

sk8norcal wrote:okkkkk, so you changed your mind on your previous theory about the 3 wheeler.... :rolleyes:

this new theory sounds like a revision of the old theory...
which I believe is wrong too...

its just what I believe, no need to get upset... :p


No offense intended...

But, I didn't post on this thread to argue about theories, old or new. I responded to questions/requests from stylezofnz.

Reload...

BgSurfer wrote:I used an old wood ply, MBS Wrangler deck with 25 degree tips. It is stiff. It is fairly short (84.3 cm) which reduces flex as well. However my first prototype had the tip of a MB bolted to the deck and rear end of a dirsturfer (adding the brake) -- it had some flex some but was fully rideable for carving and at speed.

BTW the 24" wheel with relative weight distribution shifted forward should make a great speed rig.

Another option to reduce flex is to bolt a flat plywood deck to a square tube, center frame like I am using for my prototype 3-wheel luges. That should be plenty stiff:

Image

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Dunstan
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Post by Dunstan » Thu Jun 03, 2010 12:09 pm

angrysurfer wrote:Why?


More contact patch? Wider weight distribution?

I'm by no means stating fact, pretty much brainstorming, what do you reckon to the trail theory? I'm more interested in that really, although we've deviated a little way from speed wobble... :) :rolleyes:

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Post by Dunstan » Thu Jun 03, 2010 12:10 pm

How ignorant of me... this thread isn't even about speed wobble... ha!

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Post by stylezofnz » Fri Jun 04, 2010 3:06 am

lol dunstan your on a roll mate, i love this sort of discussion however i really need to study more on "trail" as you have lost me a little at the moment. And please continue on the speed wobble, it's all interesting.
This would be easier discussed over several pints.
Shaker please feel free to input and please feel free to dispute anyone. I just feel there is no need to persue something once you have made a valid point.
Sk8 i was the one that brought up the gyroscopic effect, BG wasresponding to my comment by relating to initial thoughts on earlier prototypes until he discovered this not to be the case.

BG thanks for the ideas. I must admit the thought of reinforcing it with a tubular setup certainly had crossed my mine. I was just hoping to keep the weight down but i guess it doesn't matter too much as i will not be doing jumps on it. I like the idea of speed although i am a whimp when it comes to concrete and tar. Something about it, maybe the fact it's completely unforgiving, scares me. I suspect the brake will help with that though. It's fri night so over the weekend i will redrill the ply deck (also short and stiff :o) and test it. Should it be stiff enough i will post photos and give you a quick review.
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angrysurfer
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Post by angrysurfer » Fri Jun 04, 2010 5:16 am

Dunstan wrote:More contact patch? Wider weight distribution?

What does wider weight distribution mean? Why is there more contact patch?


Dunstan wrote:I'm by no means stating fact, pretty much brainstorming, what do you reckon to the trail theory?


I missed the stuff about trail theory, got a link?

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Jimmy Chaos
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Post by Jimmy Chaos » Fri Jun 04, 2010 5:59 am

Seems to me ,but I'm no engineer that when you compare bikes and boards it might as well be apples and oranges. totally different mechanics, center of gravity, solid frame compared to a flexible deck. Some theories apply ,but some don't.
for ex. If the steering of a bike is locked, it becomes virtually impossible to balance while riding. On the other hand, if the gyroscopic effect of rotating bike wheels is canceled by adding counter-rotating wheels, it is still easy to balance while riding.
My inlines have a fixed front and rear wheel and are not virtually impossible to balance, however trail does apply, when starting at low speed or bombing a hill you can get into that longboarder stance, weight over the front wheel for stability.when your carving your shifty your weight from center to the rear.
just mentioned this cause BG's luge has a fixed rear. If my comments are relevant then good if not that's all your going to get out of me
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Post by shaker » Fri Jun 04, 2010 6:09 am

stylezofnz wrote:Shaker please feel free to input and please feel free to dispute anyone. I just feel there is no need to persue something once you have made a valid point.


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belac
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Post by belac » Fri Jun 04, 2010 8:58 pm

:confused:


sounds like a fun set-up your making mat, maybe have a word with jon over in ausy about some of the ideas, he's the one who designed the 3 wheel outback board. i'll pm the contact details i have if your interested.

regarding the stiffness of the board: i've got a factory second flite lite that was soggy as a dunked buscuit and pretty useless for riding, so i bought some embedding resin ($20 from bunnings, or your uni probly has something similar), poured a thick layer over the botom of the board, and it's stiffened it right up. maybe worth trying if you don't want to attach tubing.

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Post by BgSurfer » Fri Jun 04, 2010 9:50 pm

That square aluminum tube (1.5") with 0.25-inch aluminum mounting plates weighs no more than, or less than, an MBS Comp 95 deck (5 lb or less). That does not include the rear fork/wheel assembly. Of course, you would still have to attach some sort of deck though.

The center of gravity for the 3-wheelers I put together is quite a bit lower than the Outback. The rear wheel also leans into the turns. The channel-truck/axle up front allows a much wider range of hub and tire choices too.



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Post by Dunstan » Sat Jun 05, 2010 4:20 am

angrysurfer wrote:I missed the stuff about trail theory, got a link?


Zis: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics#Trail

Und zis:

I'm going to go ahead and ignore most of the previous, was quite enjoying the discussion before.

I hadn't heard of 'trail' before, but I think that helps to explain why dirtsurfers are stable at speed. I've always thought that a good analogy for riding a dirtsurfer was riding a really low (COG) bike with no hands.

Using that analogy, and the geometry of a dirtsurfer frame, I think that standing on it's deck gives you more damping than just contact with seat and pedals on a bike, plus the fact that the steering mechanism on a dirtsurfer means the effect of trail will be bigger.




When the d-surfer leans, I think the two small forks moving in relation would give the effect of trail? Any thoughts people? Just speculation...

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Dunstan
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Post by Dunstan » Sat Jun 05, 2010 4:21 am

with the pics on page 4

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shaker
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Post by shaker » Sun Jun 06, 2010 8:43 am

Should we not consider the centripetal acceleration generated from the turning motion (with or without handle bars)?

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BgSurfer
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Post by BgSurfer » Wed Jun 09, 2010 4:38 pm

Photos stylzeofnz?

Regardless of the outcome, you gotta post pictures of what you came up with...
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Post by stylezofnz » Wed Jun 09, 2010 5:14 pm

sorry bud, i'm fighting the flu at the moment and have been since saturday. i'll post photos soon. promise :)
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Post by Jimmy Chaos » Wed Jun 09, 2010 5:22 pm

Excuses, excuses Haha! That's alright I have a "just for the F*&K of it" board about 80% done,but haven't gotten back to it because I'm either working or riding.
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BgSurfer
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Post by BgSurfer » Sun Jun 13, 2010 2:59 pm

Finally found the old photos of my first 3-wheeler with rear brake (Compare with ProtoTypeII below it):

[SIZE="5"]ProtoTypeI 3-Wheel ATB[/SIZE]

Image

[SIZE="5"]ProtoTypeII 3-Wheel ATB[/SIZE]

Image
~~~~~

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http://www.bgsurf.blogspot.com/2009/10/street-carver-keeping-stoke-riding.html
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stylezofnz
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Post by stylezofnz » Mon Jun 14, 2010 5:54 am

As promissed. Bg i thought you may be interested in the tire. It came off a 20 year old (the bike, not the girl) girls bike.

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I live life a quater mile at a time. And when i'm not doing that i'm riding my mountain board.

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Jasper
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Post by Jasper » Mon Jun 14, 2010 6:03 am

bloody hell, that wheels huge.

Is that frame mounted on the truck holes?
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