Scurf

[Wildcat]

I swiped the 6" cable from Sleazy Rider to see if it would fit, and it uses every inch with no trimming. I have to make a larger brake clamp because the rear fork is bigger than the rear stay that usually gets a band brake. That takes care of the brake. I laid out the flat bar from before and can make 4 crossmembers. I wanted heavier steel but with 4 of these should be plenty to hold the board. The stand may need a clamp of some kind to hold it up when riding. Maybe a magnet on the fender. The fender has holes where my previous brake idea failed so I might just leave it like that or cover them somehow. I'm going to the hardware to get the right size bolts for the board and should be ready to ride before August.

 

[Wildcat]

I lucked out and found a bike shop just a mile or so from my place. I was on the way home from the Ho Tee Hee Screw store. Ho Tee Hee has every size of nuts and bolts. I have the right size bolts for the board now.

The bike shop had a couple of the 6' brake cables. At the hardware I picked up a couple of magnetic door closer things. I'll attach one to the rear fender for the stand.

I've got the board on, but it doesn't sit flush with the frame. The rear is just a hair above because of the rear section riding up on the rear fork. I may round off the the rear of the board to match the front if I can't get it to sit flush.

 

[OddJob]

I like your cabinet magnet idea.

Most all parallel forms are braced with an X style bracing for strength. Could you do that to stiffen up the board flex on Scurf?

 

[Captain Awesome]

I like your cabinet magnet idea.

Most all parallel forms are braced with an X style bracing for strength. Could you do that to stiffen up the board flex on Scurf?

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Triangle power

 

[Ulu]

I like your cabinet magnet idea.

Most all parallel forms are braced with an X style bracing for strength. Could you do that to stiffen up the board flex on Scurf?

Hmmmm…

If your platform is a thin “slab” it will flex. But ignore that for the moment.

The wood deck should provide lots of diaphragm strength, such that no x brace would be needed in the plane of the wood.

For that to work you need lots of fasteners around the edges of the framework and to the intermediate crossmembers as well.

Imagine when you’re building a house, you have to nail the plywood on 6 inches on center all the way around the sheet edges and 12 inches on center in between. But for high-strength construction the number of nails can triple. The better you tie a diaphragm to the frame, the more rigid the assembly becomes in every direction.

OK this is gonna sound a little harsh .Your strong wood diaphragm is clipped onto the frame in the manner of an ornament. It doesn’t become part of the framework until you screw it down all the way around the edges. Your frame doesn’t have an edge in front at all, which makes the x-brace less workable. The “x” has to brace the inside of a steel rectangle.

Of course you reach the practical limit of diaphragm edge fasteners, when the screws perforate the wood so thoroughly that it just rips apart at the screw lines, Like a perforated envelope.

2 1/2 inches on center was the closest I ever saw them specify 8d nails through plywood. In your case I would suggest no closer than two thicknesses of the wood.

1/2” board = 1” oc min, Fastened into the steel with regular skateboard screws. The maximum is determined by where you need to put the screws to avoid drilling through welds and things. Plus your willingness to drill.

Anyhow I don’t think you have tied the wood Into the structure well, and if you wanna shim it up Instead of grinding at the interferences that would allow you to add extra bracing and extra steel to put those screws in. The pattern can be as practical or artistic as you wanna make it, If you can get that board tied down tight to the frame.

Without the yellow strut welded here, the X will flex a lot. You have to absorb the forces in all three directions at a trussed joint. Look up at your ceiling which is supported by trusses (or Rafters) that also hold up the whole roof. The diaphragm of that ceiling is attached at regular intervals, and it braces all of those trusses to keep your house square.

And it’s not even wood! But it works so well because the diaphragm is attached at closely spaced intervals.

 

[Wildcat]

I still have 13 feet of the tubing so a section could go across the front. One other way would be to just let it flex and ride it that way, but I think a weld might give out or the whole thing would gradually bend and sag.

Or how about a rectangular section of expanded metal welded in? Along with a brace in the front. The frame is 6" wide so that would make kicking a little easier, or the board could go right on top of the expanded metal.

Or maybe diamond plate steel.

 

[Ulu]

You could make the platform with steel and just make wood accents from the state board, but I think you lose this Skurf style at that point.

Expanded metal has no real structural value in any direction. It’s mainly for traction or grill work. You can’t screw the wood to it.

Don’t discount adhesives. GE #1 silicone applied to sanded wood and steel will add lots of strength. It would still need some screws. You can get a big tube of that here for less than four dollars.

 

[Ulu]

If you add that extra strut at the front, and x-brace it, that will add a lot of strength.

I drew a little side view in red here.

If you add a little post where I show the red dot, to give the X a shallow pyramid shape, that will add lots of strength.

The thing is that little crossmember may not be in quite the right spot Where X crosses.

 

[Wildcat]

I went and put my weight on it to see where the flex was. It is all in the downtube, the bottom frame doesn't flex at all. I have a fix in mind for that. Using the same tubing as before, two pieces 30" long will run from the top down to the bottom and get welded in on each side. Where they attach on the bottom looks to be a couple inches behind the braces already added, so a couple slots in the board might be necessary. They will get painted to look like more bamboo.
I also marked off the board to trim the end for a better fit.

 

[Ulu]

There’s always a way. You just gotta find one you like.

 

[Wildcat]

I trimmed the board and cut out a couple lengths of pipe. This is about how it will sit, but flush with the top.

 

[SwissGuy]

What if you would go this way?

Does it interfere with the front wheel then? If it doesn't, I think this would probably look better and also give more stiffness (triangles) than before.

 

[Wildcat]

That's a good idea! They touch the tire right there, but a little further back and they sit fine with no interference of the board or footing. Has 3-4 spots to weld, so I'm fairly certain this will take care of the flex. I'll have to give the welder a call. With all the extra added to the frame I could have made it out of real bamboo.

 

[ScubaLFK]

I went and put my weight on it to see where the flex was. It is all in the downtube, the bottom frame doesn't flex at all. I have a fix in mind for that. Using the same tubing as before, two pieces 30" long will run from the top down to the bottom and get welded in on each side. Where they attach on the bottom looks to be a couple inches behind the braces already added, so a couple slots in the board might be necessary. They will get painted to look like more bamboo.
I also marked off the board to trim the end for a better fit.

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I would bet the majority, if not all the flex in your downtube is at the bends near the bottom. You've braced the connection to the bottom frame, but none to your bends. An easier fix is likely to just gusset those bends. That'll stiffen them right up.

 

[Wildcat]

You're right, all the flex was right at the kinks near the bottom. The 4 welds on each side will shore up the bends like triangles.

 

[Ulu]

Well it needs reinforcement, but now I think you’re buttering the bacon.

Just a little bit of proper trusswork will save you 2/3 of the weight you’re trying to add there.

 

[Wildcat]

The welder showed up early and this should be the last welding for awhile.

 

[Wildcat]

The welder brought his grinder so the welds were cleaned up. All I had to do was sand it down. I mixed the paint to give a lighter shade, closer to bamboo, but it comes in a lot of shades. When it dries I'll add the brown rings, only thinner this time. I think they were too wide last time.

 

[OddJob]

Notice how the real bamboo bulges slightly where the rings are? I was wondering if you laid down a strip of tape, like a pin striping tape or other thin tape to create a little dimension before you paint the stripes / joints that it would create that look?

 

[Wildcat]

I had thought of using something to make a ridge like that. I have a roll of brown twine that I could use to wrap each ring, then use glue that dries clear to hold it. I think it wouldn't hold up for long and easily get damaged in regular use. If I used tape that might come loose after some time. But then I could just re tape it. If I use brown tape I wouldn't even have to paint, just clearcoat all of it. Now I'm looking for brown tape or pinstriping. I haven't started painting so I'll give this a try. If it doesn't hold then I can paint the rings on.