Tuesday, September 19, 2017

knarly knurling the sequel

I figured out some things:

I could/should have bought a scissor/clamp knurling tool that would not requore side pressure on the rotating tube. This side pressure can cause deflection of the tube and the result is a messy, unintentionally repeating groov (micro knurling). This might have been okay except that powdercoat is pretty thick and requires larger, deeper grooves.

The live center that should have alleviated the deflection appeared to creep away from the rotating tube. The force of cutting the grooves was enough to wiggle the tube into the lathe chuck and away from the live center. I could probably have reversed cutting feed direction but I had thought of a better solution:

The solution was to use bearings instead of a live center:

With a chuck in the tail stock, I ran a bolt through a few 7/8" diameter bearings and clamped a tube block on the rotating tube and the bearings. This made it so that the tail stock didn't need to apply any force and wouldn't creep away. With minimized deflection, the tube was rigid enough to have clean, intentional grooves... at least some of the time. It turns out that this takes some trial and error. The amount of force applied to the rotating tube (when first contact is made) affects the radius at which the knurl wheels sit and this can determine whether the initial cut is in phase or slightly out.
I had been content to just pay for pre-knurled clamps (for the production run bars) but it is time to cut some costs and start to make them on the manual mill. I need to figure out how to do multiple passes and get the cutting wheels hooked up perfectly in their little grooves on subsequent passes.

I'll probably stick with the micro knurls if further little tests don't prove too wasteful. The larger knurls (middle) produced mixed results on the few that I made today. I made the horizontal knurls (top) by holding a manual tool on the rotating tube and pulling but this also led to mixed results. A tool post-mounted horizontal knurl might be a good option that I have yet to try. That tool is only $20 so its worth a shot.

Saturday, September 16, 2017

Cody is still rocking his 9" bars. In reference to the rust on the bends: "that's from all the hang five bails"... Inferred subtext: (and I've never regretted a single decision since riding with these bars)

Monday, September 11, 2017

Moto Grom bars





These bars sit between stanchions/fork legs that are 6" apart and within a 4" wide clamp. The vertical sections were ovalized to allow the weld area some room. 29" wide, 3 up, 6.5 back and pretty heavy as they are .083" thick (my BMX bars are .065")


Saturday, September 9, 2017

Huntsville

Ran into Chance and Josh out in Huntsville. They let me get a few clips with them before the sun dropped



Chance's Stout from a little more than a year ago: "Iv'e beaten the shit out of this thing" (..have more confidence, I'm knee deep in bitches and I can sink an eight foot since I started riding this frame)

I got some Profile DJs on there, but they required a two foot breaker bar to get them on the spindle. The tolerances of the "new old stock" cranks and the current stock spindles was a bit too tight. I did get a stiffer spring for my fork but still managed to bottom out on a big 8-10' drop that had a little transition... er, it had a decent transition that was full of thorny weeds that I had to skip over. Was that a "cool story bro"? 

https://www.youtube.com/watch?v=zIvR32lEzPY&feature=youtu.be

Friday, September 8, 2017

Steve's 7"s and some 25.4 clamp 4" up, 10 back 3 up that are for sale