Originally Posted by Chip
The cast NRS towers with a single u-bolt and flattened shackle will rotate under stress. I think that the mechanical action of rowing tends to compress the tubing slightly which loosens them over a season.
Two U-bolts per tower is a better setup: more surface contact. I'd guess that the NRS flattened shackles will fit in Zorba's holes (so to speak). I use plain shackles from the hardware store.
Excellent work. If I'd not hacked up my own towers last year, I'd get these.
Indeed- I was taking pics of the revelation we had here when this post went up, so I looked at my old NRS towers- check out the wear marks- this indicates where they were actually touching the frame:
Ours are machined, so there will be 100% contact on that surface. Combined with the two U bolts (I designed around the standard NRS U-bolts, which are the ones shown in all the pics), these things aren't going anywhere! They * Should * be better about not letting the pipe deform when the bolts are cranked down as well- spreading out the load more evenly over a larger area etc...
The latest though from here is that if it takes a wrench, it isn't really adjustable. The fit is good enough on these that I had to check out the pin option:
The same pins I have for the cross bars will fit beautifully, and the fit on the whole thing is 'rattle free' so this should work well- We liked it enough that I changed the 'B' design as the first ones were going into the machine.
Don't worry though- I can go back to threads with Heli-coils (which is how it should be done anyway) should folks still want the bolts.