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| Truck Reviews (15215 Posts)
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kingpins break
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On 6/7/2005
peters
wrote in from
United States
(64.236.nnn.nnn)
C.C. - flatland pumping with loose reversed-kingpin trucks, will break kingpins. Techie analysis can't disprove this -- it's what I've learned the hard way, out flatlanding on the trails. I think the obvious that you're stating assumes that all or most of the riding is downhill carving and downhill pumping -- and for the most part I agree with you there. I haven't broken pins on my Randal/Gullwing setups for my *downhill* setups, to date. But loosening up the nut, and/or using really soft or beaten-up bushings, then pumping flats for miles -- will absolutely lead to a snapped kingpin on a reversed-kingpin truck. Grade 2's last approx 25-40 miles, and Grade 8's last about 80-100 miles before they break. So, I developed a habit where I switch out kingpins before the snaps happen -- a Grade 8 kingpin costs $1, whereas a trip to the E.R. starts around $500...
I decided a while ago not to use Radikals for flatland pumping, and this recent thread pretty much sums up why! However -- Radikals are incredibly technical trucks, I've been on them briefly and there is NOTHING like 'em. For slalom, for downhill racing, they are king!
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Umm Guys and Girls
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On 6/7/2005
Bola
wrote in from
United States
(162.18.nnn.nnn)
Chris:
We need to talk. Just to clear things up, we at All Boards Sports stock replacement king pins and we have seen king pin breakage and replaced them in almost every truck made that is being ridden out there.
Bola
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King Pin Breakage
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On 6/7/2005 Bola
wrote in from
United States
(162.18.nnn.nnn)
FATIGUE!
Most king pins fail as a result of fatigue. That is alternating stress applied below the failure stress of the material. The number of such cyclic stress is the most important parameter. Without going into fundamental details of this process, the following should apply. The guys that pump fastest will fail fastest if the stress placed on the king pin is above the fatigue limit. The fatigue limit is the stress the material can endure unlimited number of cycles without failure. So, the change made by Radikal to steel is a good one, as steels have fatigue limits. Titanium alloys, on the other hand do not have a well defined fatigue limit, so periodic inspection is called for and king pins replaced once cracking is initiated just like aircraft structural members are periodically inspected and cracked parts replaced. Other factors that can affect fatigue life are material defects, stress risers, surface stress state, microstructure, etc. Shot peening that imparts compressive surface stress on the king pin will increase fatigue life. Well enough being a technogeek, you all go out and skate and be careful out there.
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Umm Guys...
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On 6/7/2005
Chris Chaput
wrote in from
United States
(66.116.nnn.nnn)
At the risk of stating the obvious, it shouldn't matter what cushions you use, what type of wedge pad, what type of pumping you do, or even how much you weigh - a kingpin shouldn't break. I have boards with evey imaginal steering angle and cushion on them, taking higher sideloads than a slalom pump could ever put on them, and I simply don't break kingpins. These boards are slamming into rocks, guard rails, curbs and taking all kinds of abuse and at worse, I bend a kingpin.
I think that Duane is right - don't make kingpins brittle. Let them bend if you must, but any decent grade-8 bolt is going to be strong enough. Let's face it, it's a material flaw or a design flaw. It's NOT the type of riding that being done on the trucks. If that were the case, then Trackers, Indies and Randals would be breaking left and right.
As a fundamentally lazy and cheap skater, I am not going to routinely change kingpins in any truck. I've never had to in the past, and I'm not going to in the future. My car is lucky if even gets oil.
Try the low-tech fix. Use a "normal" material for the kingpins. If they break, it's a design flaw. If it doesn't, the problem is solved.
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Bara's breakage
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On 6/7/2005
JBH
wrote in from
United States
(165.134.nnn.nnn)
Chris, sorry to hear you beefed. Gareth's right; it happens fast and it ain't no fun.
Regarding the broken part: If a magnet sticks to it, it's steel. If it doesn't, it's titanium. I'm guessing you had steel.
I had a similar thing happen to me a few months back: lots of flatland pumping without inspecting my trucks eventually led to a front kingpin breakage. I got lucky, though, as I was just beginning to pump up to speed and was able to roll out of it with barely a scratch. My kingpin was steel, and I weigh only 155, but I sometimes pump pretty hard on flats and uphills, so I probably put lots of stress on it. Also, as McCree described, I discovered, post-breakage, that I had the "older" baseplate insert, on which the threads came all the way to the top of the insert. That's also where the threads stopped on the older (steel) kingpins, and so my pin broke right where it entered the baseplate. I spoke to Mark and Sparky about it. Sparky had me send both front & rear baseplates back so he could put the "new" inserts into the baseplate. The threading stops about 3mm below the top, so there's not a potential weak point where it enters the baseplate now.
Regarding your question of whether the firmer rear bushings might have contributed to the break: I don't know, but I doubt they had *much* to do with it. It could be that firming up the rear required more turn from the front, but I'd bet it's more due to the CUMULATIVE overturning or repetitive stress issues you identified. Again, I can offer a similar experience, or rather a similar setup: I ride clear/clear or clear/red on front and green/black on rear (first color named is closer to kingpin nut), and except for the breakage I spoke of above (which almost certainly was due to overuse and the "weak point" of the old insert style), I've been fine, even though I've done a LOT of HARD flatland pumping.
Now, I regard my flatland pumping more as exercise or practice, but in a sense it's that kind of "grocery store" riding that McCree says not to do--or at the very least, it's like doing *a lot* of racing. Problem is, I like my front Radikals so much that, for slalom at least, I hate riding any other front truck, even for practice; they just don't feel as good. Dammit, McCree, you're worse than a drug dealer! :-) So I am doing my best to check them often, and to use the bushings as intended and not overtighten them.
Bottom line: I think McCree's right. They're not "everyday" trucks, they're racing trucks. They work really well within their design parameters, but can be unforgiving if you push them too far beyond. I'd suggest talking to Mark or Sparky again, making sure you've got the newest design of insert and kingpins, and replacing kingpins after x number of hours of riding, as determined by them. You can keep the old kingpins as souvenirs, like shark's teeth, or maybe Sparky can melt 'em down into a new knife for Keith! :-)
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up trucks
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On 6/7/2005 toddc
wrote in from
United States
(198.39.nnn.nnn)
Will there be a way to actually buy them this time around?
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I would rather have...
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On 6/7/2005
duane
wrote in from
United States
(68.15.nnn.nnn)
a kingpin that bends before it breaks
too much heat treating, you don't need high tensile strength in a kingpin to tighten against rubber bushings
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Up Trucks
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On 6/7/2005
CeXa
wrote in from
Brazil
(200.141.nnn.nnn)
Hey all you guys interested in Up Trucks, the new revolutionary urethane truck, there's a new batch getting out of the factory, with Phase 2 and Phase 3 series, with a new anti-wheel-bite device!
These trucks are specially developted for Slalom, Longboard, Vert, Street and Freestyle, with different sizes and hardness for each terrain.
I will be posting some pictures of them soon.
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Then there's the pattern
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On 6/7/2005 Chris B
wrote in from
United States
(204.78.nnn.nnn)
I'm fairly certain the kingpin i brook was steel, but i could be wrong.
What is consistent is that both breaks occured while pumping flat, which i do almost every day, with red and clear bushings. Although it was on a flat riser when it broke, i had recently switched from a wedge.
Repetitious flatland pumping looks like its pretty consistent across the board though, aye?
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Radikal kingpins
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On 6/7/2005
SamG
wrote in from
United Kingdom
(193.203.nnn.nnn)
Having broken two front and one rear of the first generation titanium kingpins, I requested steel versions of the same from Sparky and these were immediately manufactured and delivered. All three breakages occurred when pumping on flat with the trucks wedged. My weight is 150lb. After discussion with Keith, I now run the trucks flat and tune through bushing changes. There have been no breakages whilst running the steel kingpins. Now I also check that both the pins and axles are firmly installed after each run. It's best to be sure of your kit. Support from Sparky and Radikal has always been first class.
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Kingpins
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On 6/7/2005
Joe I
wrote in from
United States
(63.87.nnn.nnn)
For what it's worth, both my kingpins broke while pumping flats. The last one was on the red / clear bushing.
Joe
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Stress raisers
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On 6/7/2005
-X-
wrote in from
United States
(68.239.nnn.nnn)
http://www.rockcrawler.com/techreports/fasteners/index.asp
Where, specifically did the kingpin in question fail? Picture?
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rad response
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On 6/7/2005 chris b
wrote in from
United States
(68.60.nnn.nnn)
OK..........now,PSR, i followed that but i cant claim to completely understand it!
The only lighter bushing combo i can use is clear/clear and that's what i'm switching to...(Sparky suggested a similar line)
Chuck, thanks for the offer, but since Radikal warranties the break, i'm just going to send it back to them...Sparky likes to take a good look at the part failures.
Mark. Thank you. Check your FreeMail
Tod....hell yes i'll be in Chicago...
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Radikal kingpins
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On 6/6/2005 PSR
wrote in from
United States
(69.161.nnn.nnn)
I've seen these get 'tweaked' by lightweight riders with the earlier models,yet with heavier rider going on unmolested.After witnessing that, I was skeptical of Radikal's new designs. I had made an informal suggestion that a company like Bowmalloy be looked into ,as they make high-strength bolts for nifty gadgets like RollerCoasters and U.S. Navy Destroyers, which of course need moderately high-stress hardware. The route taken by Radikal is similar, where the kingpins have been seriously up-rated (as compared with anyone else) to deal with the rather sudden side-loads we Slalomers put on trucks.
As someone who tends towards maintenence Vs. overuse, my un-educated guess is that you had the wrong bushing kit in there, and there's just too much side-to-side movement going on. That is NOT to be confused with 'side-to-side Slop', rather it's the exacting build of the other pieces of these trucks that transmits force into the kingpins.
Too stiff of a bushing, set on 'loose'; or conversely, too soft a bushing kit being squished too much while slightly over-tightened; but in either case, it's the rider demanding more Lean (with lots of force) than the kingpin bolt can stand that stresses them out. Having the Bushings sorted out, and Not Tightening them much is a major aspect to tuning Radikals.
The amazingly robust construction of the baseplate and hanger, made to exacting tolerances, and having high strength, and energy storage (titanium flexes, but dosen't break unless it's cold) that's an unusual combination in flexible mechanisms that means that the bushings, and then kingpins, become the 'dampeners' for all of the forces generated at the truck's pivot. A rider at moderate speeds can readily excede 2 'G's of their body mass in lateral acceleration, while Racers can get more 'G's going, depending on traction,technique, and confidence. You do this at a 4-cone/per/second clip, and yeah, metal fatigue will be encouraged. So, we have not an under-engineered product in terms of 'static build' (Mark is an Architect after all), but rather a peculiar grouping of dynamic forces contributing to an ovrstressed member, something that by 'the numbers' probably shouldn't ever occur.
But then again, I don't built Skateramps with Nails, ever. I use screws, joist hangers, P/T wood, and have ramps that've lasted Outdoors 20 + years. I'm only a Draftsman, Coaster/Lift Mechanic, and as such am under-educated (my math often sucks), but I do understand Dynamic Load vs. Static Load. I don't skate in a Static manner....
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Failure Analysis
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On 6/6/2005
Chuck
wrote in from
United States
(65.141.nnn.nnn)
Chris B - I am well-schooled in failure analysis...if you'd care to send me the kingpin I can take a stab at it.
The "half raised edge" is only indicative of half the kingpin's failure mode (shear overstress).
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KINGPINS
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On 6/6/2005
MARK MCCREE
wrote in from
United States
(65.40.nnn.nnn)
Chris, sorry about your beef. I can say that your experience with king pins is not the norm. Of all the races and generations, not one of us has broken one yet. Joe I. broke 2. It's frustrating.
e-mail me with your # so I can ask you some questions.
But-
Radikal king pins are not titanium. That decision was made immediately after the 2003 breck series. Radikal only had 20 sets made and we were still testing. Noah was the recipient of the first "Challenger" disaster.
We switched to chomoly steel.
we then had to tool-aneel-then re-heat-treat to spring steel specs. Not to bore you with "geezeisms" They are now as strong as you can possibly made them.
We then counterbored the stainless base plate insert so the pin screwed into the insert past the threads. now any side to side stress is not right at the point where the treads would meet the base plate. Yours may be issued prior to this change.
CB, I don't know the issue generation of your RADIKALS. I will talk to you .
I would like to remind everyone that constant use without maintainance of high stress parts spells eventual failure. These are racing trucks- not "pump to the corner store twice a day" trucks. Pins sould be replaced every season.
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randal shtuff
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On 6/6/2005 dave g
wrote in from
United States
(207.69.nnn.nnn)
C.C..Only 2 alterations! I adjusted the axle to axle length prior to realizing it really turns quickly, But you're correct on keeping a more true control!
C.B... That offset will never be a rear truck (for me) It is a natural quirky front turner It isn't extremely squirley..but it hasn't exceeded 25 mph yet (and it probably won't with me on it) I like my bushings loose and it fits that bill..But I figure she'd be "brakin up Scotty" at speed!
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rider weight
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On 6/6/2005 chris B
wrote in from
United States
(68.60.nnn.nnn)
I thought about that too....i'm 190 lbs...but Keith and Mandy are about the same weight and they dont have this problem....i've thought that maybe i ride front heavy though....i watched the other guys at St Lou and they both look to have a center or rear weight distribution when riding...
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Weight
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On 6/6/2005 Michael
wrote in from
United Kingdom
(195.92.nnn.nnn)
I do believe the owner of Radikal devotes a large part of his training time to maintaining a racing weight that allows for a reasonable margin of safety in his own products.
(I havent broken mine yet either)
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radikal trucks/broken kingpins
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On 6/6/2005
a.con
wrote in from
United States
(24.126.nnn.nnn)
just curious...
all y'all breaking kingpins on radikal trucks
how much do you guys weigh?
could it be rider weight is the x-factor here?
dislocated elbows are not fun
in fact ..ill skate vert..if i wanna get broken
is this a product/engineering flaw?
or are we talking about 190lb+ riders..
cuz if thats the case..thats the answer.
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Daves Randal
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On 6/6/2005 Chris B
wrote in from
United States
(204.78.nnn.nnn)
hmmm......Maybe put that offset on the rear and a nice, polished cutdown Randal on the front!.
(got the transfer.....mucho gracias senioro)
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Sparky's advice
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On 6/6/2005
Chris B
wrote in from
United States
(204.78.nnn.nnn)
Spoke with Sparky this morning.
He stated this.
He thinks that the kingpin breaking, such as mine again, would be from overturning the truck past it's limits.
I heard not metal-to-metal contact, but he stated it need not go that far.
He does make a point here though...I do allot of pumping around the neighborhood on this board, not just riding thru courses. Mostly flatland. This may put allot more strain on the kingpin than racing down hills.
I can buy that.
One thing he did recommend is keeping a front Rad as flat as you can keep it without hindering the turning point. Meaning dont wedge it if you dont absolutely have to, to fit your style. The wedging can lead to overturning the truck. When mine broke, it was flat, but i've ridden it on a wedge for months, so the damage may have already been done.
I'm a bit more concerned about not knowing if/when i'm pushing it past it's limits though.
In any event, the crack wasnt a perfect snap, it had a raised edge on half of it. The local engineer says this is the sign of a stress crack, not a fatigue failure, so it was definitley from force, not a chemical.
The lesson learned is if you are using your Rads to ride the streets, change that kingpin more frequently.....or if you're like me, learn to sleep on your right side...i wont be rolling over for a while.
Final note: Once again, when i called, Sparky took the time to sit down and talk to me about it, offered advice and backed up his work. The customer service at Radikal continues to be top shelf.
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Dave's Randal Offset
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On 6/6/2005
Chris Chaput
wrote in from
United States
(66.116.nnn.nnn)
Dave, I hear what you're saying but you may have come to a false conclusion about that setup. You've changed three (or more) things about the setup at the same time.
1. The hanger width has been decreased by over an inch
2. The new position of the axle trails more and is lower
3. The wheelbase has also shrunk
The narrower hanger and shorter wheelbase could account for more quickness than the trail's stabilizing effect. It's hard to say. The better test would have been to keep the hanger width at 150mm, to have moved the front truck up the length of the offset, and to see how it worked as a front truck, and then as a back truck. The other issue is that the 50 degree baseplate turns very quickly (more steer than lean).
What I am suggesting is that we take the 35 degree rear truck and flip the swingarms OR that we put the rear hanger on a front 50 degree baseplate and keep the swingarms in the stock position. We'd want to maaintain the same hanger width and axle-to-axle wheelbase for real A/B testing. Changing only one thing (axle position as it relates to the kingpin/pivot cup) is the only way to compare the result.
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oops!
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On 6/6/2005
DAve G
wrote in from
United States
(207.69.nnn.nnn)
Marion..e mail your office #! My puters all mussed up to retreeve!
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Karr Heart
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On 6/6/2005 DAve G
wrote in from
United States
(207.69.nnn.nnn)
I'll call shortly! I only "lurk" on the run these daze! Gotta work a late "dinner" trip tonight Ahhh...gormet food on the river..but it don't launch till 3:00!! Gotta get a few chores/errands done prior..Been working every day for a month and a haff lately tween surveying and raftin'When I get time off..I'm mowin' da' lawn payin' bilz and so 4th
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