Long Distance Skateboarding

Here is some information on my battle with the Mountain View, CA. to allow longboarding on their multiple-use trails: MountainViewSkateboarding.shtml. If you have not done so, please sign the on-line petition that is linked there, skateboarding should not be a crime! Here is some information on local trails to skate: Guadalupe River Trail.

 
  Side view of the Blaster as I first set it up, 100mm INDeeSZ front, 130mm Seismic rear w/ Atobe LDP wheel set Top view of Blaster Closeup of rear wheels and truck dewedging Shot of front wheels and minor wheel bite marks in the middle of the two factory cutouts.  I simply ground down the ridge in the center and no more rubbing. Side view with 15* wedging up front and -12* dewedge in back.  
 

 
  This is the G|Bomb Illuminat board With a 30* Seismic rear truck Here is am IndeeSX 139mm truck on the front G|Bomb 15* pump bracket in front of the Illuminati. Here is the IndeeSZ 100mm truck set up with an AN-24a aircraft bolt king pin.  This bolt pushes the threads clear through the base plate, so I added a short section of 9/16 Here is the AN6-24a aircraft bolt next to the original 3/8  
 

 
  To improve the feel of the truck, I made a Turcite/Delrin pivot cup bushing for the base plate, see next 2 pages for more information. I found the self-lubricating Turcite/Delrin material totally silenced the squeaky OEM pivot cup and also stopped the truck from diving at the end of a turn, instead the hanger pivots in line with the rigid pivot cup.  So this helped eliminate a bit of wheel bite I was seeing with the softer OEM pivot cup.  Currently I have over a year of pumping use on these and no wear visible.  Think of Turcite as a cross between Delrin and Teflon, the strength of Delrin with the self-lubricating properties of Teflon. Now available in 3 sizes (OD is Outside Diameter, ID is the Inner/hole Diameter): Small size (in black Delrin) that is 9/16  
 

 
  Here is my old home-made So I pulled one of the Trackers off and found the nasty looking, fully threaded kingpin, no way I would trust that.  
 

 
  And it just threads into the base, does not pass through.  I had even contacted Tracker's Tech. Support folks for advice on removing the stubborn king pin, thanks for the replies Max, amazing that you can get live human tech support on a 33 year old product!  So soaked it in Kroil penetrating oil, heated the area with a propane torch and left it to sit for a few days.  Managed to get it removed first trying a stud remover and after that failed, clamping the threaded stud in a vice and using a large Crescent wrench on the baseplate and JUST BARELY was able to get that sucker broken loose (without snapping it off).  Since the old threads in the base plate looked pretty cruddy, decided to modify it to take an aircraft bolt. I drilled through the bottom of the base plate and reamed it to 0.375 And viola, an AN6-24 aircraft bolt fits in perfectly and is just the right height and is way stronger than what I pulled out. Here is the truck with the old and new kingpins to the left.  However, I found the hard plastic pivot cup was worn out and sloppy. So drilled out the old cup, machined a 0.5  
 

 
  And here is a better-than-new Tacker FulTrack truck, ready to skate, 106mm wide hanger. I outfitted it with yellow WFB RipTide barrel bushings and an AccelSpring top washer.  Truck is better than it was the day I bought it in 1978. Los Alamitos Creek Trail, south San Jose, CA. See how the rear truck does not line up with the front Left side hole is 2-3/4  
 

 
  Right side hole is 2-7/8 So I found the problem was I was using the rear most of the front set of holes and the front most of the rear holes and that combination was not really intended to be used.  And it was the little 0.1 Holes plugged with epoxy putty.  Then I also used the rest of the putty to level out a longer spot for the truck as it sits just beyond the bend of the kick tail.  I just fashioned the putty to make a level pad for the base plate to sit upon w/o bending around the kick tail bend. Here is my old skool short pumping setup.  About 30  
 

 
  This is an old (late '70s vintage) Santa Cruz Jammer deck, used to have it set up with Independent trucks and Kryptonics 70mm wheels.  To set it up better for pumping, I just mounted the trucks at the ends of the existing bolt holes and drilled a new pair of holes one truck length towards the end of the deck.  Then also scalloped some wheel wells in the rear to get rid of the minor wheel bite and to keep the deck height as low as possible. Front truck is one of the rebuilt Independent trucks with spherical bearing, Delrin pivot cut, aircraft bolt kingpin, and Riptide bushings, wedged 15 degrees.. Rear truck is an old late '70s vintage Tracker truck which I upgraded with aircraft bolt kingpin, Delrin pivot cup and some Khiro bushings, dewedged 12 degrees. Using a 3/8 View of the 60* baseplate with the old king pin and the new A/N bolt on the bottom.  
 

 
  Replacing the worn out poly pivot cup with a new one machined out of Turcite (Delrin) Bottom bushing: blue Venon eliminator Front Virage LDP truck, blue Riptide barrel w/ orange Khiro short cone on top Here is a shot of the rear Virage truck on the Blaster with the Atobe Bonneville wheels.  It it set up with yellow over bloe Riptide WFB barrel bsuhings. Perhaps the last run on the Shoreline Park/Bay Trail in Mt. View - unless city reverses skateboard ban  
 

 
  Bottom view of Blaster w/ Virage trucks and Avila/Bonneville wheels Side view of Blaster w/ Virage trucks and Avila/Bonneville wheels Here is my little fix to both reduce/eliminate wear on a Seismic truck as well as eliminate play and noise.  I cut a piece of 12 mil UHMW polyethylene sized to fit the contact area on the hanger.  You can see the area where the aluminum has worn from rubbing against the plastic baseplate. The blue backing layer is removed and the UHMW film is applied to the clean hanger surface. Then use a razor knife to trim the UHMW to fit the shape of the hanger by trimming away any excess material as well as cutting out the king pin bolt hole.  After assembling, the hanger play is greatly reduced against the base plate and with the UHMW rubbing against the baseplate.  One or two layers of tape can be applied depending on the gap between the hanger and baseplate.  The UHMW film runs $2.00/pc. or if you want to do a few trucks, $7.00/ft. which is probably enough to do 6-8 trucks depending on how carefully you cut the material..  
 

 
  I wanted to try my Virage LDP trucks out on the Illuminati.  However, those trucks need little wedging, so instead of dewedging the front bracket 15*, I made a flat dropped bracket, approx. 20mm drop. And here is the finished setup, nice and low and no wedges, at least for now. I took a set of 83mm/77a Centrax wheels and trimmed about 3/8 Here is a shot of the trimmed Centrax (a.k.a. SlimTrax) wheels and the dewedged IndeeSZ truck on the rear G|Bomb bracket.  Shown is 22* of wedges and the bracket at around -13*, so 35* total dewedging.  That leaves the pivot axis (shown via green line) on the truck at about 10* and it seems to work quite well like this.  Added benefit of the wedges is they add a bit of clearance between the wheels and the binding skewer so no wheel bite. Here is how I trimmed the wheels down.  There is a custom machined spindle that fits into the bearing pockets on the wheels and a custom wicked sharp knife in a cut-off tool holder.  
 

 
  Wheel is clamped into the spindle and snugged down with the center bolt.  The knife is lined up with the cut mark, here 7/16 And then the lathe is turned on and the knife advanced to make a clean slice through the 'thane. Here is a typical edge bevel, approx 1/8 Here is a Seismic 130mm and 100mm truck showing the clearancing needed to fit center set wheels. The 130mm truck is one I trimmed, filing down the  
 

 
  Oh, and here is a shot of me riding the Bay Trail in Palo Alto, CA. in 2012.  Just up the trail a way is the border with Mountain View and across that line on this exact same trail goes from totally legal to totally illegal!  If anyone can explain that to me, I would love to hear it. King pins - REVISITED.  So, in the center is an AN6 aircraft bolt that I removed from my rear truck after about 7 months of skating.  Note that is is intact and did not break in that time!  Well, in the quest for a potential replacement bolt, I decided to try an F911 bolt.  While an AN bolt is rated at about 125Kpsi tensile and 75Kpsi shear strength, the F911 bolt comes in at 180Kpsi tensile and somewhere around 90kpsi shear strength.  Since my estimates of bolt loading and stress cycles says that the AN bolt is surviving something in excess of 100K cycles which says the loading is just over half the shear strength, so maybe 38K-40Kpsi.  What is important about that is that if you can keep the loading on a bolt below half it's yield stress, it can have potentially an infinite life under tha loading.  Well half of 90Kpsi is 45Kpsi and if the analysis is correct, the F911 bolt may do the trick.  Unlike AN bolts, they come with a long threaded portion, so I had to order a longer bolt and trim off the excess thread for the bolt I am using in the truck.  My plan is to run it in the rear truck and just ride it until it either breaks or I decided it has been in there long enough (bolt installed 21.JAN.2013).  So stay tuned, this may take a year or more for this Wanted to lower the G|Bomb Illuminati deck a bit in back to match the dropped bracket I had made for the front.  So I mounted the adjustable bracket on top of the deck with a steel plate below to provide support for the bolts.  I just used a scrap of steel maybe 1/8 Since the rear pair of bolts are pretty highly stressed like this, I drilled out the holes and used a pair of 1/4 Now available, Delrin fixed spherical bushing made for non-precision trucks like Tracker and Bennett.  Made to the same OD and ID of our medium sized Delrin pivot cups, machined with rounded outer edges and a 3.5mm overall thickness.  We can also make a smaller 9/16  
 

 
  For folks needing to sand down a Delrin pivot cup to fit a particular truck, here is a quick tip.  Simply wrap the end of a pencil or small wooden dowl with tape to create a snug fit for the pivot cup.  Then chuck the end of the pencil into a drill and use that to spin up the cup and hold a piece of sand paper to the outside of the cup.  This will allow you to quickly reduce the OD or length to precisely fit the base plate.  And to test the fit, just push the baseplate onto the end of the cup with it still attached to the pencil and drill.  For even easier use, you can clamp the drill to a bench or in a vise to hold it and allow two-handed access for the sanding and fitting.  And make sure your base plate has a small hole drilled in the bottom of the pivot cup hole.  That will let air escape when you insert the cup and also enable easy cup extraction with a small punch if you need to pull the cup out for additional adjustments.  Finally, realize that the Delrin material does have a bit of give to it, so you have a couple of options for sizing the cup to your particular truck.  For example, if your hanger fits loosely in the pivot cup (outside the base plate), then driving the slightly oversized cup into the base plate hole will shrink the inner hole diameter a little bit.  Likewise, if the hanger fits just right outside but is too tight with the cup installed, reducing the outer diameter of the cup will eliminate the inner diameter change.  If you need to make the cup fit loosely in the base plate, you can always use a flexible adhesive to hold the cup in place. For trucks needing a Delrin/Teflon pivot tube (like an open ended pivot cup), here is a large dia. (0.780 These pivot tubes have a hole clear through so are a little tricky to remove.  One easy way is to use a thread tap or bolt (1/2 Well, even AN bolts as king pins do not last forever.  This one failed after approx. 6mos/500miles of pumping on the front VIrage LDP truck.  Looks like classic metal fatigue, it snapped right at the baseplate, king pin inverted with the nut below the base plate.  I think it failed when the board side bushing split and let the hanger over rotate. Here is a preliminary post-tensioned king pin concept.  The idea is to use a chro-moly steel sleeve with a smaller high strength bolt inside.  The sleeve is sized to just bottom out at the desired bushing compression.  Then the bolt can be torqued up to a high value to place the sleeve into a high compression load.  Then in use, the loading on the sleeve will stay under compression loading instead of swinging from tension to compression as a typical king pin bolt is loaded as the truck turns side to side.  But you can see the steel sleeve, the bottom cap that supports the bottom of the sleeve and the smaller bolt that fits down inside the tube.  This is similar in concept to how things like bridges are built where steel rods inside the concrete are post-tensioned to keep the concrete under compression load at all times (concrete is weak in tension, but strong in compression).  The idea being that cracks in the steel grow when the steel is under tension as happens on the outside of the bolt when the truck turns to the other side.  So will try and get this set up in a truck and give it some test rides to see how it works.  
 

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