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pulled front springs on carve board

Posted: Mon Mar 23, 2015 7:20 pm
by tornadoB
Truck set up for street carving.

I added some aluminum plates to extend the tips of my Eglide electric carve board to drop the deck which also added a bit of length Then I tried to de wedge the back Bionic truck to reduce the rear truck over steer in tight carves. I pulled the springs from the front GI bionics to increase the turning radius which also allowed for a much greater lean angle. It does turn harder and improve the carve by steering much more from the front. However I am getting some sliding in the rear. Could be I just maxed our the tires, or….
I think that I may be lifting or un-weighting the outside rear tire in a hard lean because the front leans way more than the rear truck and it does this with out any weight on the board. My deck is totally stiff with aluminum battery box underneath.
Any thoughts?
I currently have the rear trucks springs screwed down a bit, but this further limits lean. I only want to decrease turn but not lean, so am going to try to add more de-wedge/cant in the rear, which will increase lean on back trucks while decreasing turn angle. Anyone played with this type of set up?
I tried going spring less and coudn't even stand on it.

I am hoping that when I get my wheels changed to the carve board type rather than the kenda slicks, I will have the added traction I need. Plus, I am burning through tires in about an hour of non stop carving, so I hope the wider tires last longer.

Please provide any thoughts on the truck setup. and if anyone knows a good mountain board that has a very low deck height please let me know. Looks likes the old GI boards had long tips which dropped the deck, I may try to get one.

Thanks
B

Posted: Tue Mar 24, 2015 12:37 pm
by Gaz
The turning radius is related to the kingpin angle (tip angle) so wedges are the best bet for altering that as you said but I have heard of people running different sized wheels front and back as well, no idea if it is effective but might be worth a punt.

Posted: Tue Mar 24, 2015 1:27 pm
by tornadoB
:)Never even thought about different wheel sizes, though there are not that many options. I may stick some wide carveboard tires on it before adding the sprocket to carveboard hub.
By De wedging the truck I am affecting the king pin angle, I just dont think I have enough dewedge yet.
added my first ever public video of riding a board, at least I think I did. No, I am not a videographer and won't do your next event... :)
https://vimeo.com/123120152

Posted: Wed Mar 25, 2015 3:22 pm
by BgSurfer
Don't buy Carveboard tires. You want these. They are the same only much cheaper. BTW the Cheng Shin 8-3.00-4 smooth tires make all the difference in the world for improving traction when tire pressures are adjusted properly.

I have yellow eggs up front and orange in the rear. I found a little stiffer in the rear allowed me to put more pressure on the back slicks for a little better traction in tight cutbacks.
My real "tight" surf-style carve secret was maintaining higher tire pressure in the front slicks than in the rear. A 60:40 ratio. Low was 29/17 high was 32/20.

Seach "surf-style carve" and variants to find more about my rigs. Check blog link in my signature also.

I also have trucks reg matrix with inside spring positions. That where I put them inside not outside. Much looser.

BTW nice video. good carving.

BgSurfer wrote:For surf-style carve, Cheng Shin 8-3.00-4 smooth tires are the Source. Yep 8-3.00-4s are what you're looking for in a "wide" street slick. Great cutback traction.

You want a hub that is wide enough for the tire. For example. MBS Twistars are too narrow. MBS Tri-spoke hubs work with Cheng Shin 8-3.00-4s, hub width (not diam) is 4.8 cm (1-7/8 in). The GI Multi-purpose hubs work great too, 5.4-cm (2-1/8 in) hub width.

BTW I believe that company at your link is in the US. That is an excellent price for Cheng Shin 8-3.00-4s though.

Edit: Forgot to mention, they are heavy tires (4-ply).

~~~~~

Posted: Thu Mar 26, 2015 9:26 am
by tornadoB
BsSurf

Great info. I am new to the whole channel truck and inflatable tires so this info is much appreciated.

Got your message about carve board being cheng Shins. How about tubes? Seems kind of hard to find?
I haven't been using eggs, I thought they would limit max lean. My front trucks turns way more with out springs, so I don't have to de wedge the back so much to limit rear over steer, but it is kind of squirly at speed. I have some yellow eggs and I will try them in the back to see what happens.

I bought my Eglide board used and am using it a reference to build the ultimate electric street carver. So far I have lowered it by extending nose and tail with aluminum plate to raise the trucks. It doesn't seem like you mess with lowering your boards..It made a difference on my board, but it was higher to begin with. This is why I was looking for the lowest mbs deck. Maybe the old GI decks?

I have some lipos and am waiting for the new battery box. It currently weighs over 50lbs with the lead acids.…. so dropping some weight will help also.

What do you think about flexible mountain boards vs stiffer decks for street carving? I am used to stiff long board decks but can flex the crap out of a snowboard...I have a battery box so my the board is totally stiff. If I went to a mountain board I have to add battery protection that flex's or put batteries on top, as seen in other mbs ebuilds, which I don't want to do as I am riding with out bindings.

I had crazy idea of trying to design or get designed a truck mount that would de-wedge at speed. As, I am building an eboard it could be linked to the esc, so the turning radius would decrease as speed increased while still allowing full leaning. The truck would only have to pivot about an inch…
My board really likes to do full lean turns but it is awkward once the speed is beyond the tightest turning radius.

What would your set up be for 10-14mph hard carving?

Thank you for going so deep into street carving and sharing the stoke.

B

Posted: Fri Mar 27, 2015 1:26 pm
by BgSurfer
Don't have time for thorough answers at the moment. Maybe this weekend. Where are you located?

Basically, tight surf-style cutbacks control the speed on my hills. I'd say my average carving speeds are between 10-14 mph. At 20 mph, I'd be coming in hot...

Posted: Sun Mar 29, 2015 10:31 am
by BgSurfer
Cheng Shin tubes with the correct stem shape/angle for MB hubs are hard to fin without seeing the actual tube. In the past I have used MBS tubes for 9" diameter hubs in Cheng Shin 8-3.00-4 tires without any problems.

Your current hubs do not look like they are wide enough to mount carveboard or Cheng Shin smooth tires.

Tip angle between 0-45 degrees affects turn radius -- closer to 45 degrees tighter, closer to 0 very little turning.

Deck bottom height over axles affects lean/turn responsiveness. Skateboard axles are usually significantly below the bottom of the deck. Drop-decks bring axles level with or slightly below the deck bottom (more stable for speed).

For all MBS decks, I believe axles tops are very close to level with the bottom portion that is closest to the ground. With channel trucks, this provides sufficient leverage for good street carving. Increasing deck tip length drops the deck below the axles increasing stability but reducing responsiveness -- hard leans will be hard to execute.

GI decks have longer tips because the mounted their trucks in a position that is flipped relative to MBS channel truck mounting.

Older MGS Comp 95/16 decks had inside and outside truck mounting position holes in the deck. The new ones do not. Spring positions for GI spring Bionics are outside only like Matrix Lites and Pros. The further the springs are placed away from the center of the deck the stiffer and less responsive the ride.

This is a MBS comp 95 deck I redrilled for GI Torsion Bionics (no spring holes). Note the spring holes for the Matrix trucks the inner holes are no longer present in this later model. The standard MBS Matrix regulars used to have inside and outside spring mounting positions (picture below). Carveboard springs are close to the center -- like inner spring mounting holes in the these trucks. Springs closer to the center allow more/easier leaning but are more wobbly at speed.

MBS newer model deck outer holes only (not in use because of GI torsions mounted)

Image

Inner and outer spring mounting positions:

Image

Blue Comp with inner matrix springs mounted and Yellow Comp with Flipped GI Torsions (no inner spring holes).

Image

Way too much information for me to re-post in this thread. Do google searches with these search strings:

surf-style street carving site:surfingdirt.com

tip angle site:surfingdirt.com

axles level with bottom of deck site:surfingdirt.com

axle placement site:surfingdirt.com

speed wobble site:surfingdirt.com

An earlier post:

BgSurfer wrote:I posted this at SilverFish and thought it might be helpful here also. I was discussing the basic turning principles for a skateboard or mountainboard truck.

I rode skateboard trucks teens to early 20s and again at 54 for my first mountainboard (all-terrain skateboard truck 15.75" axle length, 400mm) -- never really considered how they worked. The kingpin pivot axis/angle concept is incorporated into the skateboard truck design but is still the same basic principle as that of the channel truck. (Reverse kingpin angle was not being considered.)

A vertical kingpin pivot axis (90 degrees to ground) would turn the sharpest/tightest if leaning would make the axles move around the pivot axis. As the kingpin pivot axis increases from 45 to 90 degrees, the ability to tip the deck side-to-side (lean) approaches zero -- deck remains level as axles spin around the kingpin pivot axis at 90 degrees.

As kingpin pivot axis increases from 0 to 45 degrees, less lean angle (deck relative to ground) is required to turn the board. As angle of the kingpin pivot axis approaches 0 (zero), more deck lean angle relative to the ground is required to turn the board. Pivot axis at zero degrees -- deck leans but board will not turn.

The channel truck's kingpin angle relative to the riding surface drove the turning mechanism principles home for me. The angle of the channel-truck kingpin (axle pivot axis) is determined by the tip angles of the mountainboard deck.

The channel truck kingpin represents the axle's pivot axis. The pivot axis is the axis around which the axle rotates. The plane of axle rotation is perpendicular to the pivot axis. Basically, channel truck axles rotate around the kingpin.

Also, placement/position of the pivot axis relative to the axle (distance from axle) affects the diameter traced by axle tips during their rotation about the pivot axis, which also affects leverage.

Angle of the pivot axis determines the amount of deck lean required to initiate turns, which combined with deck leverage, affects quickness/snappiness of turn -- responsiveness. Elastomer density affects leverage effect and snap (quickness of response), and is used to fine tune responsiveness.
Pivot axis angle also affects turning radius.

I switched from all-terrain skate trucks to channel trucks when I modified my mountainboards for surf-style street carving -- channel trucks were more responsive, with springs for RTC.

Greater deck width increases lean leverage. Increased deck height above axles increases lean leverage. Bushings or springs damp lean leverage. More lean leverage increases responsiveness.

As axle-to-axle distance decreases, turning radius decreases.

At this point for me, changing deck design will have more effect on rig responsiveness/performance than truck design. But I have ideas for truck design as well (weight related).

This is my most responsive channel-truck rig with kingpin angles (deck tips) at 35 degrees:

Image

Image

Posted: Sun Mar 29, 2015 12:34 pm
by BgSurfer
Continued from previous post...

Inner and outer spring mounting holes are clearly visible on the tip of the this MBS Blue Comp 16 deck. Inner postions in use:

Image

Posted: Sun Mar 29, 2015 12:35 pm
by BgSurfer
Continued from previous post.

Inner and outer spring mounting holes are clearly visible on the tip of the this MBS Blue Comp 16 deck. Inner postions in use:

Image

Springs in outer positions on these MBS Matrix regulars.

Image

Posted: Mon Mar 30, 2015 8:42 am
by tornadoB
BgSurf

Thanks a million for all the info. I have a lot of tweaking todo.
I got some trispoke hubs and have them just on the front and put yellow eggs in the rear....what a difference. I think I heard trumpets play when I first got on it....
I had the front slip out on me a few times with the kenda's and it wasn't pretty. It feels so much surfier and groovier now..Can't wait to get all four going once i drill out the drive sprocket.
The only concept that I can't get head around is the deck height being lower than axles making it more difficult to lean hard. I am still about 1" above axles now and dropped the deck about 1" from original and it handles better. With electronics on the bottom it would be hard to go below the axles anyway.

I think my next biggest improvement will be a shorter board so I can put springs back in the front and keep my turning radius, my board is currently 45 1/2" from truck to truck.

I am like a kid in a candy store with a ripping carveboard and empty street in front, especially when i get my lipos with longer run times.

I currently live in Austin Texas and only kiteboard in the summer, so I am dry docked and couldn't get my lean on, during the week. I am moving back to California in a few months, unfortunately Santa Monica, so surfing is more of a hassle than when I lived in North San Diego.

I lived in Asheville a while back so was not to far from your area... could have used one of your carve setups there.

You da man....
B

Posted: Sat Apr 04, 2015 10:39 am
by BgSurfer
For surf-style carving, I found stiffer decks to be faster (snappier) and more responsive than decks that flexed. The flex seemed to use up the speed. The greater the distance between the axles, the greater the flex.

Regarding deck height above the axles:

In channel trucks especially (but skate trucks too). The deck bottom is above the axles. Now remove the springs or any mechanism for return-to-center (RTC). The deck will not remain upright, it will tip and fall to either side.

If the deck is below the axles, remove the springs or RTC. The deck will remain level/stable between the axles. The deck would be more like a hammock between two trees. Because the deck is stable and more difficult to tilt, it will create less responsive steering. This would be very important for something like a street luge.

I graduated from UT many moons ago: Hook em' Horns. The Hill country should have a few good grades -- traffic could be an issue.

I like your electric solution to flat-land surf carving.