rjnakata Posted February 28, 2023 Report Share Posted February 28, 2023 Q: Could a plate's mounting type (4x4, UPM, Allflex) affect board flex differently? The fore-aft mounting points of the Allflex are further apart than 4x4. UPM spacing is similar to 4x4. Is it the axel spacing that determines a plate's effect on board flex or is it mounting point spacing? Could it be both? I rode Apex X plates with 4x4 and then with Allflex mounts (with no mid plate fastening) on the same board. The entire setup was identical except for mounting type. I felt the Allflex plate lengthened the turning radius, ie hindered board flex. Was I imagining this? Note: I'm not talking about edge pressure or responsiveness comparisons or how UPM is superior than 4x4 etc. TIA Quote Link to comment Share on other sites More sharing options...
SunSurfer Posted March 1, 2023 Report Share Posted March 1, 2023 The axle position determines where the riders mass is applied to the board. The greater the interaxle distance the less a rider of any given mass will bend the board. Thought experiment: compare the situation where all of the riders mass is applied at the centre of the effective edge vs where the axles of the isolation plate are at either end of the effective edge. The AllFlex design originally had arms that attached to the board at roughly the middle that limited the chord depth able to be produced to about 7mm if my memory serves me correctly. So YES, the AllFlex design appears to intentionally limit board flex. 1 Quote Link to comment Share on other sites More sharing options...
rjnakata Posted March 1, 2023 Author Report Share Posted March 1, 2023 (edited) 2 hours ago, SunSurfer said: The axle position determines where the riders mass is applied to the board Thanks for your thoughts. Is it strictly the axle position? What if the mount points are outboard (further toward tip and tail) of the axles as with allflex vs INBOARD of the axles as with 4x4? (edit) WAIT: the axels of the Allflex appear further outboard than the 4x4 mount by a significant amount! Allflex and 4x4 shown: Edited March 1, 2023 by rjnakata Quote Link to comment Share on other sites More sharing options...
SunSurfer Posted March 1, 2023 Report Share Posted March 1, 2023 (edited) If the mechanism has solid contact with the board below the axle then the axle determines where the rider mass is focused. If the mechanism is designed so that the footprint on the board is not under the axle then the footprint determines where the mass is applied. The design of most isolation plates is such that the attachment points do not cover a significant proportion of the flexing length of the board, compared with the footprint of a binding directly attached to the board. So the "flat spot" created by the attachment points is minimal in its effect on the overall longitudinal flex of the board. When the board flexes under turning load then the board flexes away from the plate between the axles, while beyond the axles the board flexes closer to any overhanging part of the plate. The previous comment noted the effect of the central attachment point of the AllFlex design. The original Vancouver Olympic time Apex plate had the front overhang which was used in various ways to modify flex in the front part of the board. Edited March 1, 2023 by SunSurfer Quote Link to comment Share on other sites More sharing options...
rjnakata Posted March 1, 2023 Author Report Share Posted March 1, 2023 2 minutes ago, SunSurfer said: If the mechanism is designed so that the footprint on the board is not under the axle then the footprint determines where the mass is applied. With Allflex in this example the attachment footprint is not under the axle. So the footprint (not axle) would determine is effect on board flex...do I have that correct? Quote Link to comment Share on other sites More sharing options...
SunSurfer Posted March 1, 2023 Report Share Posted March 1, 2023 IMO yes, you are correct. Functionally, when the board bends under load there will be 2 fulcrum points where the distance between plate and board remains constant. Outside of those the board will bend towards the plate and inside of those points the board will bend away from the plate. Those fulcrum points are effectively where the riders mass is being focused. Quote Link to comment Share on other sites More sharing options...
rjnakata Posted March 1, 2023 Author Report Share Posted March 1, 2023 (edited) @SunSurfer Given the difference in axle / mount / binding relationship, I can see now why the two plates gave a different ride feel. Thanks for your input! Edited March 1, 2023 by rjnakata 1 Quote Link to comment Share on other sites More sharing options...
Jack M Posted March 2, 2023 Report Share Posted March 2, 2023 20 hours ago, rjnakata said: WAIT: the axels of the Allflex appear further outboard than the 4x4 mount by a significant amount! The shape of the plates is different. I believe the axle distance is the same. Quote Link to comment Share on other sites More sharing options...
Jack M Posted March 2, 2023 Report Share Posted March 2, 2023 23 hours ago, SunSurfer said: If the mechanism has solid contact with the board below the axle then the axle determines where the rider mass is focused. For all 3 Apex X-plate mounts, the mount contacts the board below the axle. I've ridden all 3 on Kessler 168s. In my experience the UPM and Allflex versions rode identically. The 4x4 version rides a little differently for different reasons - it is supposed to have 8 bumpers, and that's how I rode it. The Allflex mounts did not make my board carve a longer radius. Mechanically I don't see how that's possible. Quote Link to comment Share on other sites More sharing options...
rjnakata Posted March 2, 2023 Author Report Share Posted March 2, 2023 4 hours ago, Jack M said: The shape of the plates is different. I believe the axle distance is the same. The mount to insert/axle relationship is reversed and spread apart on Allflex vs 4x4 (BTW: I was told only heavier riders need all 8 bumpers for 4x4 by Jason at Apex. Lighter riders can use 4 according to him.) Quote Link to comment Share on other sites More sharing options...
pokkis Posted March 2, 2023 Report Share Posted March 2, 2023 (edited) On both above main force to board is place of axle. On AF version it is way of first insert and on 4x4 it is very close to first insert. Additional general notice is that all solid plates also bend with board, some more some less. Edited March 2, 2023 by pokkis Quote Link to comment Share on other sites More sharing options...
SunSurfer Posted March 2, 2023 Report Share Posted March 2, 2023 (edited) The interaxle distance varies markedly between designs. AllFlex is 784mm between effective axles. See linked thread above. (And see @pokkiscomment below. Exact interaxle distance could be measured by someone with an AllFlex plate, likely between the 2 axles in the rocker arm mech at each end of the plate.) https://allflex.si/about-2/ AllFlex limits the chord depth on that 78.4cm interaxle distance to 6.4mm. see AllFlex website reference above. Edited March 2, 2023 by SunSurfer pokkis comment below Quote Link to comment Share on other sites More sharing options...
pokkis Posted March 2, 2023 Report Share Posted March 2, 2023 In reality that 784 is distance between mounting inserts, axle distance is less than that. But that 784 is quite close of distance between points where force is directed to board. 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.