Update from C2 wrote:UPDATE FROM C2:
The few cases of fatigue cracks that we are aware of to date have started at the small notch in the box frame at the end of the bend under the foot stretcher. This notch was necessary to prevent the metal from tearing when the box frame was being bent into shape. Our pre-production testing of this part showed that we had adequate strength to avoid a fatigue problem. In hindsight this testing was not quite enough since at least in certain loading situations the frame has not been strong enough.
When we first became aware of a failure we realized we had to devise a better test that could duplicate this fatigue crack we were seeing in a relatively short time. In order to get results quickly we had to both speed up the cycle rate and use a very heavy load. We now have the test, which consists of a rapidly alternating load of 600 lbs (275kg) on the rail near the foot stretcher. With this new test we could start seeing a fatigue crack somewhere between 1 and 4 hours. Fatigue is a fairly random process so each part will be different.
Once we were able to duplicate a fatigue crack, we then needed to test possible solutions. Ideally, the solution needed to be applicable to both new production rowers as well as rowers that were already shipped. And for the units already shipped, the reinforcement had to be easily installed by the customer. After a number of dead ends, we now have a design that exceeds the criteria. We are now able to install the reinforcement on a box frame that has developed 2cm cracks and have it go 60 hours with the 600lb fatigue test without any further cracking. At 60 hours we had to stop the test because the box frame was breaking up in other places where the design is the same as on the 14 year old Model C which we have never seen fail.
At the time of this writing, we are now using this method of reinforcement on new production rowers. We are also working on phasing in a box frame that does not need this reinforcement. This design is also required to outlast the 600lb/60hr fatigue test.
We also do max load testing on the frame. This consists of loading the rower on the rail near the foot stretcher with as much load as we can until something fails. The results may come as a surprise to some people longing for the “sturdy old Model C.” The Model C failed at 700lbs. The mode of failure was the monorail hanger bolts plowing their way through the rail. The Model D and E shipped between Aug 06 and April 07 failed at 1000lbs. The mode of failure was buckling along the top edge of the box frame between the foot stretchers. Note that the failure is not at the notch where we had seen the fatigue cracks. The D and E monorail connection was redesigned from the C to get the additional strength. The Model D and E with the reinforcement installed does not fail at 1800lbs. Enough said.
The last part of this process is how to roll it out to customers. To tell you the truth, the cheapest and easiest way would be to quietly eliminate the possibility on new units, do nothing about the shipped units, and just replace the few that fail in the field under warranty. This would be a viable possibility since this type of failure does not involve physical danger. In fact, most of the rowers that might eventually fail would likely fail beyond the 5 year frame warranty. The problem with this solution is that it could damage our reputation and it does not agree with our company mission. The applicable part of the mission reads: “To design, sell, and service unique products of high quality and value for the benefit of the Concept2 community including customers, employees, families, suppliers, and the local community.”
So we decided the best thing to do was to be proactive and eliminate the possibility of this problem occurring by offering a free reinforcing kit to all customers with affected rowers. We consulted a PR expert who said we would be lucky to get 5% of customers to install the fix. We are hoping we can get 20 times that rate.
Dick and Peter Dreissigacker, Concept2 founders
neilgunton wrote:Paul, thanks for the update. Sounds more promising.
I just received my new Model D. There appears to be no reinforcement plate installed (at least, not anything like the one in the pics Concept2 have supplied). The serial number starts "042507", which is after the period they specify as being affected by the problem. So I'm not sure if this unit has the "new" design or not, given the statement in your message that "we are now using this method of reinforcement on new production rowers" - that makes it sound like the new machines will still have the reinforcement plate, for the time being, until they roll out the new design that doesn't need it... I'll call them tomorrow to try to clarify what the case is with my machine.
mpukita wrote:I had a nice note from Bill Patton at C2 after he saw my post about having a new machine (it arrived yesterday) but no visible signs of the thin plates added to fix the problem. He said:
[OK, I am Mark, but what the heck, he's probably trolling the boards like madman!]
I read your recent post on the UK forum and wanted to reply to you directly - we've just posted a more thorough recap of the situation in the form of a letter from Peter and Dick Dreissigacker from the main notice page:
http://www.concept2.com/us/support/rowe ... iption.asp
To quote from this letter:
"At the time of this writing, we are now using this method of reinforcement on new production rowers. We are also working on phasing in a box frame that does not need this reinforcement. This design is also required to outlast the 600lb/60hr fatigue test."
Your box arm was one of "phased in" units that did not need the plates.
In short you are good to go.
So I've got the new box frame. Will have to watch it to assure it's a good fix.
John Rupp wrote:PaulS wrote:still have an example of each one except the Model D (just never got very attached to that one for some reason
Thanks for your comments. May I ask what you didn't like as much about the model D as compared to the others, and do you like the model E better? Is the model E more stable with less shimmy? Details would be helpful as I might consider going that route too.
Thanks and all the best,
neilgunton wrote:I took a few pics of the new machine, which appears to be the new design. These are all views of the area which appears to be affected, i.e. the end of the box frame which the fan is attached to, specifically the end with the foot rests. Please forgive my crappy photography, I tried to just get a few good views so people could see the shape of things in there. I'd be interested to compare it with the old design (which needs the reinforcements)...
Users browsing this forum: Bing [Bot] and 2 guests