Shame about the trailer not working as smoothly as expected. Could the shimmy have been caused by the load being too far back, maybe worth trying to get more weight in front of the axle
Hi Mac!
Thanks for your excellent suggestions; I did my best to employ both before leaving and numerous times by the side of the road. Extrawheel recommend placing weight as low and far forward as possible, so I put my water bags in the bottom, then again standing vertically at the front. Same for the U-lock and for the netbook and charger. You'll notice in the photos, I gave up attaching anything to the trailer's own rack. Putting *any*thing up that high just made things worse, so weight placement is surely a factor to some degree. However, in the end nothing helped address the inconsistent handling. If it had only done it all the time, I might have been able to hone in on a solution. I lost count of the number of times I stopped, got off, locked up the brakes, deployed the Click-Stand, and knelt down by the trailer to check and adjust everything in hopes of a solution.
What was so baffling was the inconsistent nature of the trailer's handling woes. The trailer would be tracking along wonderfully one moment, then
woggita-woggita-woggita, away it would go, oscillating in
ever greater arcs (same frequency, increasing amplitude) till I did
something (sat, posted, braked, accelerated, leaned, or stopped) or it just spontaneously quit misbehaving. Posting did always seem to bring it on, while sitting sometimes broke the cycle. It never did it on dirt or gravel (it flew upward there), but some paved surfaces were worse than others in terms of seeming to contribute to or cause the problem.
Back home, I've been looking closer at things and my leading candidate for core contributor to the problem is the quick-release hitch. The tolerances are just huge, and the quill can actually slip sideways in the end cap. The other cap's threads are very loose on the quill, there are perfectly smooth back-faces on the nut/head/hitch, and the q/r lever's tolerances are so sloppy there is never an over-center "stop" -- I had to stop myself a dozen times or so to reset the q/r 'cos the lever had rotated 'round to the inside (no stop) and was starting to foul the chain as it passed over the Rohloff cog. I have spoken to Extrawheel about this at length and they sent me two hand-selected replacements for my three "bad" q/r-hitches. At any rate, the hitches are a huge weak point
in my use and I think the problem is aggravated by the relatively low tightening torque required by the Rohloff hub. I think the trailer might well be fine with different q/r-hitches as indicated by the experiences of others, like our own Australian Pete (Il Padrone), who has had very little if any trouble with his Extrawheel and only noticed a slight oscillation on one smooth surface. However, another Forum member has contacted me with a handling experience nearly identical to my own on an earlier model that caused him to give up on it.
I did notice initially, when about to leave home, trailer tire pressure seemed to be a factor. I had an initial oscillation riding in front of my house while running only 1.5bar/22psi, so I raised it to 4.1bar/60psi and it seemed to away. This didn't work once out and away, however. I think the higher pressure reduced lateral scrub at the tire contact patch, and on dirt oscillation wasn't a problem, either. I was going generally slower, but the dirt allowed the trailer's tire contact patch to drift laterally and so it did not impart and transfer a moment-force to the rear of the bike. Otherwise, when on pavement, the effect of a trailer oscillation was very much like the tail wagging the dog. It felt as if a hand had reached out and was laterally pushing the bike side to side at the rear drops. The bike alone did fine with no handing problems of any sort when I tried briefly dropping the trailer and riding the same patch. Trouble is, I didn't want to abandon such an expensive project by the side of the road, so I persisted. Even so, I'm only good for so much such effort with the same inconsistent results, even in the name of Science.
I'd sure like to make it work after investing so much time, effort, and money into it, and the need for it remains. I classify it as a worthwhile experiment of great promise that so far has failed to pan out due to some issues I had not foreseen.
At any rate, the problem of the trailer lofting or pivoting upward enough to foul the mudguard stay attachments and break the 'guard is a stopper for me; those 'guards are expensive, and now I've got to order a replacement from SJSC (can't get the same model Stateside), drill it, rewire it, reattach all my electrical connectors and reapply the logos. SJSC say the SKS 'guards are virtually breakproof and I believe it, but not when hit repeatedly by a 20kg trailer. Looking at the heat-shrink tubing I sleeved onto the stays (to match the black bike), you can see where the trailer fork repeatedly impacted them, causing the breakage. The trailer "flies" when it hits an obstacle, and it also doesn't take much of a difference in slope between bike and trailer to produce the same result. That's the one issue I don't know how to resolve even if I get the trailer to handle consistently.
For use on dirt or gravel behind a mountain bike with no mudguards, I think the trailer might be ideal provided the q/r-hitch clearances can be tightened. For use on my Nomad or other touring bikes with mudguards on anything other than level, smooth pavement...no, 'cos of the fouling problem between trailer fork (tongue) and 'guard stay mounts.
When I get time to fully process my notes and data, I'll cover the trailer issues in more depth in the thread devoted solely to it
http://www.thorncycles.co.uk/forums/index.php?topic=4953.0Best,
Dan.
