Monday, March 28, 2011

Like the Golden Gate Bridge...

The new tube motor is in place and gets its open & close stop limits set, and final wiring is completed.

Our attention turns to the tube motor controlling the north ridge vents. It hasn't been operating automatically as it normally has. It still opens and closes when the switch is operated manually, albeit, when the switch is put to the open position, the skylight closes, and when the switch is put in the close position, the skylight opens, but hey, heretofore it has been doing so automatically; closing when temperature inside is being conserved, and opening when temperature inside is being vented. But lately it stopped behaving and now just sits there oblivious to its environment.

My technician helper noticed that the close stop limit looked a little too close for comfort, so we decided to adjust the motor's stop limits since we were right there with the control box and limit adjusting tool. With the control box we can open and close the skylight vents as we stand right there on our ladders at the ready to adjust the motors limit settings. Throwing a 3 position toggle switch on the control box alternately opens, stops and closes the bank of vents, allowing us to fine tune the stop limit settings while we observe the position of the vents.

First, we opened the vents slightly to then test the close stop limit. Toggling to the "close" position, we watched and listened as the vents closed. A subtle ca-thunk sound beyond just 'closed' told us that indeed the motor was pulling the vents closed too much. He toggled the switch the other way to open the vents a few inches and then turned the adjustment setting on the motor housing to make the close stop limit activate sooner.

Unbeknownst to us, the 'subtle ca-thunk' involved two brass screws attaching a distant rack bracket to a skylight vent wooden sash to snap off, and the rack fell back away from the sash, rotating on the steel shaft to an inverted position. (Follow the link to an archived post detailing what the rack and pinion system looks like) When Ben toggled the switch to 'close' again, the pinion gear drove the inverted shaft upward where it caught an edge of the wooden roof frame and drove the steel shaft away from its mooring in the pillow block screwed to a rafter, ripping the screws out of the bottom of the rafter and splitting the rafter to boot in the process.

I suppose it's just as well it happened when we were there to stop things when we heard the horrendous snap. Had it happened automatically, either the steel shaft would have been bent beyond repair, or other unimaginable damage to the skylights or roof frame could have occurred.

Fortunately, after disengaging the rack from the pinion gear and its wedged position against the roof frame, the steel shaft appeared unbent. The rafter was repaired with stainless steel screws and gorilla glue, and the rack bracket was resecured to the vent sash. It was necessary to move it slightly to one side, because the old broken off screws still remain in their original holes, making it impossible to reattach the bracket in the same place.

Next blog post takes a look at resetting the stop limits.

Friday, March 25, 2011

Replacing a tube motor

Along the ridges of the greenhouse are venting skylights that open and close by means of tube motors that activate (via remote computer command) to rotate a steel shaft affixed to a rack and pinion assembly that is attached to the wood framed skylights. In the picture below, notice that a tube motor is in place along the left bank of skylights, while none appears along the right side. That's because it burned out, and is being replaced.

A bronze bracket on which the motor mounts is shown on the leftmost tube motor below:

The one on the right side has been removed in the photo below because it was deemed partially responsible for the failure of the motor.

These tube motors have adjustable "stop limits" that tell the motor when to stop turning, either closing or opening. This is because the rack shaft is only so long, and the motor must stop cranking when the skylight is fully open or fully closed. The bronze bracket has a square hole where the square shaft of the motor fits, providing a fixed point against which the rotating motor bears to cause the steel shaft to turn, operating the skylights. In this case, it seems the square hole was slightly oversize, giving the motor shaft a 'sloppy' fit, and playing havoc with the adjustment of the stop limit setting. Along with the immense combined weight of 10 triple glazed skylight vents on a motor just barely rated to lift them, and 11 years of faithful service, we theorize that this is why the previous motor burned out.

The solution, we hope, is to modify the bronze plate on its backside, which will be out of view, with an additional plate cut to a much tighter fit, and a new motor.

The motor has a key way at the steel shaft end to mate and lock rotation with the steel shaft.

Below you can see the steel shaft and the detached rack and pinion setup; detaching it from a couple of skylights let's us pull it back to facillitate sliding the new motor onto the shaft.

The new motor slips in nicely with the modified bracket and awaits electrical reconnection and stop limit adjustments:

Looking back down the greenhouse ridge:

That was fun!

Thursday, March 17, 2011


The possibility of installing a web camera has arisen here at Searock. We are investigating the feasability and practical requirements. In the meantime, see if this conveys the idea:

Thursday, March 3, 2011

Chimney soot power wash

There are 7 fireplaces in the house, 6 chimneys, and 17 'portals' distributed among those chimneys. By 'portals', I mean openings on the chimneys, out of which smoke would presumably be expected to come. But some of those portals are 'architectural', i.e. for 'show' only, and 2 minor ones are for attic ventilation only. The architectural ones are generally closed up with sheet metal. This was done at some unknown time in the past, perhaps to keep out birds or rodents. Some of these painted sheet metal covers have long since fallen out, but the vertical stack itself is screened with wire mesh. One of these sheetmetal covers developed a tiny hole some years back, a year or two before our tenure began, and a colony of bees took up residence inside the chimney space. Thought I'd blogged that, but I can't seem to find it. I'll have to post some photos of that adventure later. It was very good honey!

The current project is:

to try and remove these soot stains that have been here for many years. They don't add to the charm of these rustic and majestic sculptures:

They are on the leeward side of the great room and kitchen chimney. The two central portals are architectural. The windward side shows the 'original' appearance:

Setting up the job was a project in itself:

Most projects here involve several foot cruises around to various tool rooms and lumber piles. Helps to develop a perspective on the work:

Once everything is set up and safety checked, work can begin: an initial blast with the power washer, followed by a spritz bath of dilute muratic acid.

I let the acid sit for a while and then blast away again.

When everything is put away and the chimney is dry, the reviews are mixed. There is certainly an improvement, and I'm glad to have made the effort. I'm satisfied, but I wish it could have been a more dramatic difference. At least it's not such an eyesore anymore.

Other projects beckon...