Bummer – The Beater Vanishes

You would think a bike locked up to a utility pole at high noon on a sunny Sunday in the heart of Fells Point would stay still, yet this morning I found out otherwise.

Sometime in the thirty minutes in between glances outside “just to check,” I was dumbfounded to find my bike vanished while I was upstairs.

Someone must have snipped the cable and thrown the bike into the back of a truck since the Kryptonite U-Lock tied the rear wheel to the frame and prevented it being ridden away.  It probably took less than 30 seconds all told, fast enough that it’s possible no one walked by during the heist.  There must have some witnesses though, as this occurred across the street from a senior center and it seems there’s always someone looking out the window.

So, on the off chance that you see the bike below, drop me a line.  I miss it.

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Before and After

I had left the eMR2 in the garage last year after pushing the throttle produced clicking noises from the motor bay rather than any forward motion.  I figured the noisy transmission had finally given out and embarked on the rebuild of the spare unit, something I had wanted to do in any case.  I had entertained the possibility that the coupler may have been damaged but considering how sturdy it was it didn’t seem like a likely possibility.

Only last week did I finally drop the drivetrain out of the car to separate the motor from the transmission to take a closer look and it was a surprise.  The transmission still rotated freely so the theory that a bearing had seized or other catastrophic internal damage occurred didn’t appear to be the problem.  The pile of black powder settled at the bottom of the bellhousing did look out of the ordinary, though.  The coupler had also shifted towards the transmission and I could see the mangled remains of the self-locking retaining ring pitifully dangling from the input shaft.  The coupler had been laterally constrained by the end of the splines on the motor shaft and the apparently completely inadequate washer at the other.  Figuring there not being much possibility of the coupler wandering, I didn’t use something more substantial like a clamp collar but more secure positioning will be incorporated inyo the new design. Examining the coupler produced the first clue; both splines had stripped completely and one of the pins had a chunk torn away.  Tearing material away from a hardened pin isn’t the easiest task.dsc00928

The electric motor puts out more torque than the four cylinder but considering I wasn’t hard on the car and it had only travelled about 100 miles it didn’t make sense that the splines would be completely destroyed in so short a time.

It was then that I noticed that the collar around the transmission input shaft revealed a lot more of the shaft than I remembered.   Compared to the rebuilt unit there was at least half an inch missing.  That’s when a closer look at the pins on the coupler revealed discoloration from high temperatures and wear on one of the pins that had slightly backed out.
Apparently the motor was working double duty as a metal lathe, grinding the coupler against the transmission collar and absorbing enough power to flatten the coupler splines.  So that’s where all the power and range went.

The ground-down input shaft collar

The ground-down input shaft collar...

On the bright side, at least the destroyed splines were on the coupler rather than the motor, which would have been a far worse situation.  I thought about getting the coupler hardened but this situation is a good reason not to do that.  It’s much more preferable for the more easily replaceable (though still expensive) coupler to absorb the damage rather than the motor or transmission.

...and what it should look like

...and what it should look like

During the design stage a couple years ago I had also developed another coupler that incorporated the shock absorbing hub from the original clutch but went with this design based on its simplicity.  Back then it didn’t seem like the spring hub was necessary as there would be no transmission shifting and the electric motor wouldn’t produce the internal combustion vibrations that the sprung hub is designed to moderate.  Now it appears that retaining the sprung hub is a good idea to relieve the unhardened splines of shock loads so they can live a less stressful life.  There’s additional insurance in the fact that the spring hub can absorb a little angular misalignment just in case there’s some relative motion between the motor and transmission.

I brushed off the old design and incorporating a way to constrain the coupler on the shaft so it doesn’t slide around again.  The spring hub will be harvested from a sacrificial clutch disc that’s arriving within a week.

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Velomobile Progress Update – 31 March 09

“Habits Equal Results”

“Persistence Pays Off”

“Sorry [GF], I can’t make any plans until next weekend”

These are all phrases, passed down through the ages by some very accomplished and intelligent people, that one keeps in mind while making steady progress towards a distant goal, especially when that progress comes in small pieces grabbed from whatever’s left of 24 hours in a day outside of a full day of contract work, the minutiae of daily life and beloved sleep.

Work on the velomobile has continued with some very satisfying results though at the expense of any progress toward rehabilitation of the MR2 and, for better or for worse, any blogging activity.

And so I present, for your viewing pleasure, RESULTS:

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So much progress has been made that this picture is already obsolete: control bars have been bent up, the steering mechanism significantly modified, the whole machine dismantled and rebuilt several times as well as many lessons learned.

Most of the sheet metal parts, such as those that constrain the NuVinci, the upper control arms, and the swingarm shock mount have been found inadequate and led to redesigned parts.  In the case of the front suspension, a significant review of what the hell I was thinking six months ago had to be undertaken as the suspension didn’t do a very good job of constraining the wheel while the NuVinci mounts, in a subtle effort to compensate, interfered with the sprocket mounted onto the machined flange of the NuVinci enough that a chain would not fit.  Just as well then, since the NuVinci control box would, under certain conditions, get crunched by the upper control arm.

Some of this was due to the difficulty involved in machining the NuVinci as it frustrated nearly all efforts to fixture it well enough to machine the flange.  What inititally was only supposed to take Nolan a few weeks and one sixpack of Guinness (in cans) ended up costing a month and a half, several conversations with a wizened old German machinist, several trials with both lathes and mills, handing it off to another friend with the appropriate CNC machining center and a comped dinner.  In addition to the Guinness.  Even then, the numbers on the drawing couldn’t be met and so a few mm here and there ultimately resulted in interference.  I thought machining the flange would be easier than using an adapter to pick up the brake disc mounting holes and bridging the distance to the sprocket with an adapter but that now looks like an improvement to make in the next version.

While those parts are being made I will occupy myself with the cargo racks and the exoskeleton.

Posted in Velomobiles & HPVs | 1 Comment