pavedwave distance skateboarding distance skateboarding, flatland pumping, cross-country adventuring, boardwalk cruising, and all things skateboarding and good times
I hear people saying titanium is brittle. But there must at something that aeropace engineers know that longboarders don't about its fatigue properties. I suppose the only way to emperically state they are too "brittle" would be for somebody to a) buy one b) use one c) break one. I'm certainly no engineer. But differnt metals will have different fatigue thresholds.
At $30 or so, i can see why nobody is jumpting on it. I know Radickal sells one but my plates came with a std. Its really a piece of cake to replace them. The rear truck KP would be difficult but those don't seem to be the problem. The front KP can be easily replaced since the agnle is so high(55#). No JP weld or anything. So its a tough sell to me to buy a titanium.
Titanium is good for areospace applications for two reasons. One, its very light for the strength it provides and two, it doesnt change properties much with temperature changes. Neither of these two properties are particularly important to longboarding (unless your REALLY want to cut down on weight). I still have confidence in grade 8 pins. So far ive NEVER broken a grade 8 FRONT kingpin, only rear ones. The custom pins that james and i had made have not broken so far. I suspect it has more to do with the shape of the KP (splines or no splines, how much threading) than the quality of the material. I agree with blake and stacato, i prolly should shed some pounds and reduce the wear on my gear and also should be more mindful of replacing kingpins BEFORE they break.
I want a kingpin made of Busse Combat's infi steel. Those knives take some a use and I am not aware of any that have snapped. I think Jerry Busse charges 100 dollars an inch for a custom knife. 300 for a kingpin would be an expensive experiment.
Last edited by egret on Tue Apr 28, 2009 11:02 am; edited 1 time in total
i thought it was the front that breaks. The rear breaking seems like it would be more easy to recover from.
My Rads are supposedly Ti but don't seem very light weight to me for some reason. I am sure the Ti is lighter than the grade 8, however.
But why would Randal and Rad bother casting them? Just to save a few grams? It seems that strength would be important to both.
Again, somebody has to test one and break one before i believe it is more brittle. Air frames and the fan blades of a jet turbine can't be too brittle, can they?
Yeah, rear KP breaks are a lot better than front KP breaks, believe me ><
When a rear breaks, you hear a POP and then a little jingling as your washer and pin hit the ground. Then your rear truck becomes uncontrollably unstable and you jump off and pick up the scattered bushings and hardware.
When a front breaks, you hit the ground, fast.
Ive broken a stock Bennett KP but they are weakly designed and I suspect they are not grade 8 (they dont bear the grade 8 markings). Trust me, its 0 fun.
As to why truck manufacurers produce TI kingpins, i think the answer is that people will buy them for $30. I do agree with your testing argument tho, no one that i know of has actually tried to break one and seen how long they last. If you want to buy me one ill beat the hell out of it and report back tho!
I'm no engineer but I don't think titanium has much give. It is rigid. The jet engine parts you mentioned would not be absorbing a lot of shock. Are the bolts and rivets used titanium or steel?
I'm with panda. 30 bucks is not outrageous fir a kingpin if it won't break. I bit the bullet and bought virages primarily for the clearance and stability. My Bennetts have hooked up and sent me flying enough that 300 dollars is worth the peace of mind. I hope, haw haw. Falling sucks. LDP stance is not the easiest to land on your feet from when the board suddenly stops. I've never broken a kingpin but it is always on my mind. My heart goes out to camel.
yeah titanium is infinitely stronger than steel, but it depends on how it's being used.
for aerospace use titanium fastenings are exactly that - fastenings torqued up to hold components together, with no give allowed or desired.
on a skateboard, the very nature of tac'ing puts lateral stress on the kingpin, and as it's not secured hard-and-fast in the baseplate, there is room to move and to break. at least grade 8's bend a little before snapping.
stainless steel is similar in brittleness to titanium, too much flex or vibrations cause it to crack before bending.
now from all this, i was looking at some old-skool boards the other day and some old ACS trucks caught my eye.
mainly 'cause the kingpin was secured into the baseplate with a nut BEFORE the bottom barrel is installed. which got me wondering, something like this could alleviate the requirement for an additional cone/barrel at the bottom, plus hold the kingpin in place securely with no chance of sideways movement in the baseplate. obviously the kingpin would need to be threaded almost the whole length (which might negatively offset any benefits).
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