I guess my answer wasn't as clear as it could have been, I went ahead and changed it, your answer seems to work well, except that I don't think they're grappling hooks, which usually have a more distinct hook shape.
Rob
They are called "log grabs", "logging dogs", "timber hooks" - individually. Made up into a sling, there may be another name. They perform the same function as "skidding tongs".
John Martin
According to R.H. :
O.K. The disassembled shots show no signs of an exciter coil, so my original guess at being for measuring the power line frequency directly was wrong. Otherwise, I would have asked for a photo of the base to verify that it did not even have a small hole -- through which a wire could have secured a contact button which is now long lost.
So -- given that, the various calibrated tilts and swivels allow it to measure vibration in different axes, with the knob still tuning for the optimum frequency.
Most induction motors run a bit slower than synchronous speeds, so the ability to tune would help. For example, a two-pole running on
60 Hz would run slower than the synchronous 3600 RPM -- probably something like 3550 or slower.The ability to rotate the axis of sensitivity would make it possible to determine just what is the most likely contributing factor of imbalance -- a good thing when you are looking for the source of imbalance in a complex system with things rotating on multiple axes.
Enjoy, DoN.
I don't see why a device to measure electrical frequency would be marked in degrees if you rotate it or tip it. Photo 1055 b shows a hole in the threads. Apparently a pin can be inserted to lock the screw base in a certain alignment. I think a base like a light bulb is used not to conduct electricity but because it's good for transmitting vibrations along three axes.
If the frequency markings are in Hz, they would correspond to machinery rotating at 3,000 - 5,000 rpm. It could be a car engine or maybe something stationary like a pump or generator. The tilting must be to measure vibration from an engine and the machinery it drives.
I think it might be for R&D of new machinery. It might be for checking an overhaul. It might be for tracing vibration that has been noticed.
Except that skidding tongs (very similar to ice tongs only MUCH heavier, with the "handles" linked to the pulling chain) are much easier and quicker to use. Gerry :-)} London, Canada
On the answer page I added some photos of the box that it came in, where you can see some slots for pieces that I'm missing.
Also I updated the answer to the log grabs, and added Tom's scan from the old Fairbanks catalog.
Thanks to everyone for their input on both of these.
Rob
You first tune it for maximum sensitivity to the fequency in question, then you shift the angles and compare the maximum swing of the reed. This lets you determine in which axis the vibration at that frequency is at a maximum, and thus what is the likely componenet contributing to the vibration, so you can work on balancing it.
Enjoy, DoN.
Rob, Just in case no one else has told you. Thanks for the post's. Great to see the unique things you list. Puff
That is an inertial balance. Its for the purpose of measuring the inertial mass of an object.
The large brass screw near the bottom changes the pendulum arm length. The weight at the top can be altered to increase the weight (hence the numbered slots in the box).
What it's measuring - I don't know.
According to Eigenvector :
I had agreed in another branch of this thread that it was not for measuring electrical frequency -- but the mechanical frequencies will be related to the electrical power frequency assuming an induction motor instead of a series or parallel wound DC or universal motor.
That is a rather different device -- for demonstrating principles in a physics lab. This device which we are discussing looks more like something to use in the field.
It is measuring the amount of vibration at a selected frequency along a selected axis -- for the purpose of identifying the sources of the vibration and eliminating or at least minimizing them, one at a time. You select a frequency, determine along which axis it is strongest, and work on balancing a device rotating at the proper RPM to produce that frequency and oriented to produce the vibration along that particular axis (that is -- perpedicular to the axis of rotation).
Not sure how much we will be able to follow this newsgroup for a while, given that it appears to be under attack by massive cross-posting to/from sci.crypt. I've set my killfile to eliminate those, but there is bound to be a lot of discussion about that -- plus probably cross-posting attacks from elsewhere as well.
Enjoy, DoN.
Sounds like a good description of it, I went ahead and put this on the answer page, I like it better than what I had there.
To everyone at RCM: feel free to join us on one of the other groups on Thursday if you want to post some answers or read some comments on next week's post. Hopefully things will clear up soon.
Rob
I agree with the functional description. My questions are: 1. Why was the Edison screw base used as an interface?, and 2. Are there any other known uses of the Edison screw base for anything other than light bulbs, heaters, and other electrical connections? We may never know, but it is sure interesting.
Don Young
OK, many of us knew what it was, but how many of us have actually used item # 1057, the Detex clock?
Here's a picture of one of the buildings I patrolled as a young Coastie at the USCG Training Center on Governors Island, NY, off the southern tip of Manhattan. Trust me, the attic space of that building can be pretty creepy at 3 in the morning!
Thanks for the memories!
That's where I used a Detex. In the photo, if you turned right and walked to the end of the row, that was where I slept. If you continued across the street, there was a building with a portico along the front. That's where I carried a Detex. It seems like I sneaked around in sneakers instead of those shoes with heavy rubber soles we wore during the day.
To measure vibrations, wouldn't you want a stem with a large diameter, like that screw base, in order to be as stiff as possible? It might have been a tube with pipe threads, but light-bulb threads screw in quicker and are almost impossible to cross thread.
The wide frequency range suggests to me an internal combustion engine and not an electric motor.
A tugboat! I'll bet they rev to 4,000 or more and they would want to investigate vibrations before incurring unnecessary damage. The engineer hears something isn't right. He screws in the device. It's easy with the bulb threads. He tunes it to the engine RPM. He tips the device to see if vibration of the engine and various shafts rotating at that speed seems normal.
Now suppose there's a 5:1 reduction gear. He swaps weights to make the pendulum 5 times heavier and 5 times slower. Now he can turn it to an angle to check vibration from the slower shaft.
1975ish for me.
Did you jam beers in the vents of the window AC units in the rec rooms to get them cold...err...I mean cool? Or did you spend the big bucks and buy them out of the vending machines in the barracks - the ones half stocked with soda and half stocked with beer?
How much did it suck sleeping in the ferry terminal when you missed the last ferry (3:00AM?) to the island?
I was there at ET School in 1972. I don't remember air conditioning. There was no beer in the barracks and I don't remember a rec room. Some said the draft beer at the club tasted like dishwater but I liked it. The speed limit was 15 except where it was 5 or 10. I had two friends in the SPs who said it was ridiculous trying to clock somebody doing 16 in a 15 zone, but that's what was expected. They drove Matadors.
We suffered a warrantless locker search. In my locker was camping gear. In my camping gear was a cooking kit. In my cooking kit was a teaspoon. The sneering clerk demanded to know what I was doing in possession of a spoon. Obviously he assumed it was drug paraphernalia.
Those were two of many reasons I hated the place. I served on a ship with a classmate. He begged to get off. He was told no way. One day the crew began saying he was acting just like me. The captain offered him the duty station of his choice if he would leave immediately. He chose Governors Island and we sailed straight there.
He told me he hadn't learned anything about electronics as a student or in the field, so he figured the only billet he was fit for was an electronics instructor. That way he'd be around people who knew even less than he did.
It suddenly occurs to me that it's probably not for 50 - 80 Hz but 50 -
80 RPM. Isn't the arm too long, the weight to big, and the spring too light to vibrate at 60 Hz?This page says the steam engine on a Liberty ship was designed to turn at 76 RPM. I suppose that was at full speed, so you would want a device that could be tuned to lower RPMs to check vibrations when the ship was cruising slower.
Easy on the electronics instructor putdowns! I ran one of the training labs at the ET school for about 9 months just before my discharge in
I know two guys that got speeding tickets on the Island. One was doing
18 MPH on his *bicycle* on that long sweeping road around the back of the island. The other chirped his tires on his souped-up VW Bug after we replaced the engine in the old auto shop. The SP's claimed that if his tires chirped, they must have been going over 15 MPH at the time. You can't argue you with them, so you pay the fine and do the duty.The rec rooms I speak of were the TV rooms at the end of the hallways in the barracks. As far as the club, the $1 Black Russians were my poison of choice.
He who enters covered here...
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