seems like ohlins are getting into the mtb world with shocks and a possible fork ???
any one has more info ? interesting to see what will happen to cane creek's DB.
http://happymtb.org/2012/10/26/ohlins-satsar-pa-mtb/
Last edited:
Well maybe that's because the DB is made by Olhins ?Maybe my eyes are fooling me, but that looks a lot like a double barrel with a thicker shock shaft and Ohlins stickers on it.
What on earth could you be referring to?If Ohlins decides to reproduce their version of the double barrel, I really just hope they can make a shock that does not snap in half. Then I'd probably buy one.
By snap do you mean perform very well while having a wide range of adjustments without any known issues?If Ohlins decides to reproduce their version of the double barrel, I really just hope they can make a shock that does not snap in half. Then I'd probably buy one.
Wasn't there issues on last years Demo with the CCDB shafts snapping?What on earth could you be referring to?If Ohlins decides to reproduce their version of the double barrel, I really just hope they can make a shock that does not snap in half. Then I'd probably buy one.
The issue was with the Demo, not the CCDB. That little swing link that attaches to the shock puts tremendous load on the shock shaft. Issues were not limited to CCDB, but also all other brands.Wasn't there issues on last years Demo with the CCDB shafts snapping?
That was implied, that the issue was with the Demo and not the shock. Otherwise I would have just said "CCDB are snapping on frames" with no mention of the Demo.The issue was with the Demo, not the CCDB. That little swing link that attaches to the shock puts tremendous load on the shock shaft. Issues were not limited to CCDB, but also all other brands.
To be a bit fairer, the issues really only popped up on frames with worn, notchy, sticky bearings in that link, increasing the friction and limiting movement on the link under compression. I haven't heard of issues on new or maintained frames.
It's obvious it's easier to snap a smaller shaft so on a frame that puts too much stress on it a shock line ccdb will snap more often than one with a wide shaft like an rc4.That was implied, that the issue was with the Demo and not the shock. Otherwise I would have just said "CCDB are snapping on frames" with no mention of the Demo.
Whoa. Lots wrong with this post.It's obvious it's easier to snap a smaller shaft so on a frame that puts too much stress on it a shock line ccdb will snap more often than one with a wide shaft like an rc4.
meh. maybe. mix a little mechanics, materials science, and math and you will see that a hollow tube can actually be designed to be stiffer than solid.Whoa. Lots wrong with this post.
1) The rc4 shaft is hollow aluminium, as it has to accommadate the rebound needle valve adjuster. In contrast, the DB shaft is solid steel, and hence far stronger for given external thickness.
2) That said, there WERE issues with DB shafts snapping. Hence, the latest version has a slightly thicker shaft, as pictured on the "Ohlins" shock above.
12345meh. maybe. mix a little mechanics, materials science, and math and you will see that a hollow tube can actually be designed to be stiffer than solid.
Correct
also, if that link is free to pivot, (ideally) all stresses on the shock would be normal. sounds like a lazy owner that doesnt maintain their bike could cause some irregularities in the links motion. obviously the shock is designed to be applied in a normal loading mode. albeit, maybe spec could have done a better job engineering the link to run smoother for longer.
In a perfect world, yes. Now let's examine the situation where the rear wheel hits something the size of a basketball and the shock hydrolocks, or at least exerts a whole ton of resistance on the piston, especially near the top of the travel. In that instance it's essentially a rigid member (heh heh) for a split second, and is going to want to bow, a lot. The extra length of that link is NOT what the engineers behind the shock ever designed for, guarantee it. The fault with that mostly lies with Specialized for using the shock in that manner, or partially with Cane Creek for spec'ing that silly narrow bendy shaft, and selling it to Specialized as an OEM component knowing how it was going to be used.
I never had any problems with my Ohlins moto forks and neither I nor my bike was lacking mass. Any bending moments created by poorly maintained or designed/built pivots and frames will definitely cause problems though.That article must be OLD.
Those were the very first generation Double Barrel shocks. They were used in a lot of FSAE programs. There are a stockpile of those things sitting around the CNC lab at my school with 200# springs on them. That version of them is definitely not made anymore.
They also have a solid piston in those. Not solid in the sense that the shims never blow off - I mean a solid piston.
For road applications they worked real well, which is basically what Ohlins stuff is made for.
After using their stuff extensively both on MTB's and dirt bikes, I'm convinced they're really not made for off-road use. A big part of it has to do with their shaft durability, at least on MTB's. They do snap, and not just on Demos (although most of those fail in that manner). They also bend. A lot. Their moto fork cartridges also rely on a very small diameter rod, which is also steel I believe. They have to be replaced frequently and recommend checking runout against spec on every rebuild. Better hope you have a damn stiff chassis to put those cartridges into.
As for hollow 5/8" aluminum round stock vs 8mm solid steel stock - put them through a deflection/bending test and see which one sees permanent deformation/failure first.
Had no idea but I assume a wider yet hollow shaft of the rc4 is still stiffer so it handles some forces better. Also no one claims their saints are weaker because they are hollow, quite the oppositeWhoa. Lots wrong with this post.
1) The rc4 shaft is hollow aluminium, as it has to accommadate the rebound needle valve adjuster. In contrast, the DB shaft is solid steel, and hence far stronger for given external thickness.
2) That said, there WERE issues with DB shafts snapping. Hence, the latest version has a slightly thicker shaft, as pictured on the "Ohlins" shock above.
Making it hollow doesn't make it stiffer. Removing material ALWAYS makes it less rigid. A hollow structure can simply supply more stiffness for the same mass.Had no idea but I assume a wider yet hollow shaft of the rc4 is still stiffer so it handles some forces better. Also no one claims their saints are weaker because they are hollow, quite the opposite
Yeah he did switch to Ohlins this year. They've got some work to do! Anytime he landed a jump it looked like that bike wanted to buck him right off.Mike Alessi and the MotoConcepts team are currently testing Ohlins rear shock and front fork for SX.
You know, I was thinking about this in the context of Easton's larger diameter handlebars the other day. They claim that increasing the bar diameter from 31.8 to 35 makes it stronger and lighter. This just sounds bizarre to me. If anything, smaller diameter would allow for more strength and lighter weight. What's with that?Making it hollow doesn't make it stiffer. Removing material ALWAYS makes it less rigid. A hollow structure can simply supply more stiffness for the same mass.
Not entirely true. You have to make sure that given your manufactured shaft runout and the highest compressive load it's going to experience that it doesn't buckle, though of course the stiffness required to stop buckling is usually reached long before a practical shaft diameter for a shock is reached.The rod diameter for a rear shock is based on the displacement requirement for compression damping, not for stiffness. If the rod is being damaged on a specific frame, then you shouldn't be looking at the shock for fault.
I think that we can agree that it should be a "given" design parameter that the rod be able to support the spring and damping forces generated. Unless the shock is a specific strut design, it shouldn't be taking much. if any, load from the frame.Not entirely true. You have to make sure that given your manufactured shaft runout and the highest compressive load it's going to experience that it doesn't buckle, though of course the stiffness required to stop buckling is usually reached long before a practical shaft diameter for a shock is reached.
Yeah of course, I was just being a bit pedantic.I think that we can agree that it should be a "given" design parameter that the rod be able to support the spring and damping forces generated. Unless the shock is a specific strut design, it shouldn't be taking much. if any, load from the frame.
My point was simply such that the reason an RC4 has such a large diameter rod, and the CCDB considerably smaller has nothing to do with strength and stiffness and everything to do with displacement based on the damping design.
That is exactly what those shocks pictured are for. FSAE.That's most likely the version of the DB made for Formula SAE, which is a collegiate competition for engineering schools where they build & race small open cockpit cars. Due to the size of those cars, DH mtb dampers end up working well and running revalved versions have been the hot setup since about 2002 or so.
FSAE was very successful at taking 100% of my free time when I was in school. This is an FSAE car (from my alma mater):
If all you care about is rigidity and stiffness for the "strength" of the bar then a larger diameter, thinner wall is almost always better. However since you need some minimum wall thickness for any tubing on bike parts for impact resistance you have more constraints you have to optimize within, so larger diameter doesn't always yield better strength/weight.You know, I was thinking about this in the context of Easton's larger diameter handlebars the other day. They claim that increasing the bar diameter from 31.8 to 35 makes it stronger and lighter. This just sounds bizarre to me. If anything, smaller diameter would allow for more strength and lighter weight. What's with that?