The Other Measuring Tools

[TomG]

(02-24-2018, 08:58 PM)Highpower Wrote:

(02-24-2018, 04:58 PM)randyc Wrote: I think mine will reside on my coffee table 99.99% of the time (beside my Brunton Pocket Transit) but it looks like, when needed, it's going to be very handy.  This is the Brunton:

Nice Randy.  

This is a wonderful pocket transit. I used to use one made by Brunton to aim radar transponders in the field. Makes me want to own one, but I can't come up with many uses for it in the shop.

Tom

[Highpower]

(02-25-2018, 09:27 AM)TomG Wrote: This is a wonderful pocket transit. I used to use one made by Brunton to aim radar transponders in the field. Makes me want to own one, but I can't come up with many uses for it in the shop.

Tom

I just remember seeing pictures in my youth (Boy Scouts) of higher end pocket compasses that looked similar, and then looking at my El Cheapo $2.00 compass.

Sure would have made picking out landmarks a lot easier.

[randyc]

Tom, that's interesting, the Brunton was probably near-perfect for aligning electronic gear.  I seem to recall reading somewhere that they are also used to align satellite receiver antennae ...  Sounds reasonable because, not only is it a very precise compass, but also a very precise clinometer for measuring elevation angles.  Did you also use the clinometer function ?

I had a Brunton "aiming circle", which is much like a transit, in the Army many decades ago.  It was employed for laying and directing a 4.2 inch mortar and was awesomely effective at it's purpose.

BTW, I hope that I haven't gone too far afield with this post but these are measuring tools, LOL.

Back in the day, I enjoyed backpacking in the mountains here.  I used my old Army lensatic compass which worked fine although considerably heavier than it needed to be for backpacking.  But as I approached and passed age forty, I found the lensatic too hard to read and obtained a very light Suunto M2C compass which I still own and keep in my earthquake-preparedness gear in the trunk of my car.

The Brunton "Pocket Transit" (and the Asian knockoffs below) probably to no one's surprise have never been outside of my home, ha-ha-ha, they are all manifestations of gadgetmania.  I especially like the prismatic compasses, I'd never used one before buying a pair of them about ten years ago.  They are perfect for those with imperfect vision !

   

If I rewound enough years so that I was fit enough to resume strenuous outdoor activity, and if it was available, I'd carry this inexpensive little Chinese compass made by a company named (oddly) "Coughlan".

   

I've seen these online for just a couple of dollars U.S. and they are a lot of value.  They combine the features of map compass and lensatic compass.  I weighed this one and the Suunto and the weight difference is tenths of an ounce, the Suunto being lightest.

And speaking of gadgets, this is part of my electronics lab:

   

The photo is about five years old - there have been more additions since then ...  If there were a "Gadgets Anonymous" I might be one of the senior members !!

[randyc]

I received the protractor today and for the price, it's an amazing little gadget and I have only a couple of criticisms which I'll address later.  As everyone has noted, the protractor has a vernier scale that allows reading down to angular minutes, although this is going to be difficult for those of us with ancient eyes.  However I was able to make readings with the aid of a magnifying glass.

Using this device on a surface plate will be a piece of cake but measuring small parts while holding both protractor and part in one's hands is not easy !  it's almost as clumsy as making thread measurements with the three-wire method.  The part tends to want to slip out of the protractor jaws and I dropped a couple while evaluating the tool.

Practice improves this, as you'd expect.  And speaking of practice, remember how it took a bit of that to be able to obtain consistent and accurate readings with telescoping gauges ?  The protractor is something like that, although not as picky.  When I first started using it, the consistency of my measurements was somewhere between two and seven minutes of angle.

The more that I used it, however, the more improvement I saw and eventually (after about twenty minutes) I was able to repeat measurements within a minute or two of angle.  I expect that the device will, like a telescoping gauge, require a minute or two practice when it's time to make a measurement to confirm that a consistent result is being obtained.

I limited my brief evaluation to the measurement of a set of precision angles, from one to thirty degrees as shown below:

   

The maximum angle that can be measured is slightly over fifty degrees and I felt that the larger the angle, the more awkward the measurement technique.  This may not be a problem in normal usage, like on a surface plate or with part clamped in a milling vise - maybe it's just because I was holding the protractor and the part and didn't have that third hand that would so often be useful !!!

If I had only one or two samples to measure, then I'd not know if the measurements obtained were indicating errors in the tool or errors in the parts.  But with eight samples of different angles, I'm confident that my measurements were a good indication of protractor accuracy.

The measurements were consistently undersize but just barely, the mean error was -1.5 minutes of angle and the standard deviation was 1.9 minutes of angle so one can be reasonably assured - at least with this particular instrument - that a measured angle would be in the range of 0.6 minutes to 2.4 minutes HIGHER than the indicated measurement.  That's pretty darned good accuracy for a tool that is available for less than $30 USD !

Oh yeah, I made a note of the measured error and placed it inside the plastic case for the protractor.

This leads me to a problem that could have been addressed with a simple design change.  There are no means of zeroing the protractor; whatever the existing error, you have to live with it.  Would have been nice if, by loosening a couple of screws and slightly nudging the vernier dial, I could move the low reading of -1.5 minutes to 0 minutes on the scale.  As is, all of the movable parts that would permit zeroing are screwed and then pinned, having been "aligned" by the manufacturer.

But here's my major criticism and I just can't find any excuse for this shortcoming.  The "reference bar", the sliding bar with the sharp chamfer on one end, has a sixty degree vee on side that is clearly meant to ride in a sixtee degree groove on the mating part.  These are the parts (and note that I have yet to thoroughly clean the protractor, LOL):

   

The lack of the vee groove allows the reference bar to wobble from side to side slightly with modest pressure, even when the clamp is securely tightened.  This doesn't affect measurement accuracy but is irritating when trying to hold an odd-shaped part in one hand, the protractor in the other hand while the part is moving.  (BTW, flipping the reference bar doesn't improve the wobble.)  The device is fairly well-made, incredibly well-made for the cost, and the lack of this helpful feature detracts a bit from total satisfaction.

Addendum:  Been playing with the protractor for another twenty minutes and apparently some of the previous errors were operator-related.  I'm getting zero errors (within the limits of the instrument) on some of the angle blocks now.  It would be interesting to hear other owners' experience regarding this device.

[f350ca]

Thanks for the review Randy. Appears to be a good investment. Mine hasn't arrived yet.

[randyc]

(03-16-2018, 08:31 AM)f350ca Wrote: Thanks for the review Randy. Appears to be a good investment. Mine hasn't arrived yet.

Any chance you could give us your impressions when you receive it ?

[f350ca]

Sure

[randyc]

One more thing that I just discovered, and this may be representative only of the one that I bought, but the protractor head cannot be reversed on the square and maintain accuracy. That's a real shame, it would be a useful configuration.

When I reversed the protractor I saw an error of more than one degree ! The reason, looking closer, is that the inside edge of the short leg of the square is very rough and stoning didn't improve things much. A cup wheel on a surface grinder would be the ticket for fixing this but I don't have a surface grinder, LOL.

Hope that yours doesn't have this problem (and the vee groove problem) Greg.

[TomG]

(02-25-2018, 07:04 PM)randyc Wrote: Tom, that's interesting, the Brunton was probably near-perfect for aligning electronic gear.  I seem to recall reading somewhere that they are also used to align satellite receiver antennae ...  Sounds reasonable because, not only is it a very precise compass, but also a very precise clinometer for measuring elevation angles.  Did you also use the clinometer function ?

Randy,

We used the transits to aim X-band radar transponders. The azimuth wasn't critical because the included angle of the beam on that axis was quite large. The elevation was a different story with the beam angle only about 3º, so we used the inclination function to set that.

Tom

[randyc]

Thanks, Tom, I wonder how much the government had to pay for our Brunton gear, LOL ! The one that I used was one heck of a nice instrument and was "militarized" well including shock mounting (and protective covers for transport).

A performance update for the protractor: last night I disassembled the protractor (at least to the degree possible), thoroughly cleaned and lightly lubricated it with sewing machine oil. After wiping down and reassembling, I find no error greater than one minute when measuring my entire set of angle blocks. VERY impressive tool !