Anyone have a calibrated magnetic compass on a naked Tonti? UPDATED.

[johnr]

Well done Moto. You seem to have sorted it well.  It looks good there as well. For some reason I had imagined a much larger item.
Interesting clock you have there. What is it?

[BRIO]

Tasteful looking instrumentation.

I think it would be hard to adjust that compass. You would need a type that is adjustable not only for variation but also deviation. Then you'd have to complete a compass swing procedure similar to how they do it in aircraft and I assume ships. Not particularly difficult as far as I understand. Maybe you could find a suitable old aircraft compass with the required scissor magnets.

Or this;)

[Moto]

Well done Moto. You seem to have sorted it well.  It looks good there as well. For some reason I had imagined a much larger item.
Interesting clock you have there. What is it?

Thanks, John. I had thought it was a bit bigger myself.

That's the clock I mentioned two or three weeks ago. Here it is: http://wildguzzi.com/forum/index.php?topic=83112.0. Whoops, that's six weeks ago at least! (Its handlebar mount is the one I used for the compass.)

John (Moto)

[Moto]

Tasteful looking instrumentation.

I think it would be hard to adjust that compass. You would need a type that is adjustable not only for variation but also deviation. Then you'd have to complete a compass swing procedure similar to how they do it in aircraft and I assume ships. Not particularly difficult as far as I understand. Maybe you could find a suitable old aircraft compass with the required scissor magnets.
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Thanks for the "tasteful" comment.

The compass is easily adjustable for variation, and suitable for the compass swing procedure that I've just been reading about. In fact, because of Kirby's earlier mention of having calibrated his compass (the same model) on an airport compass rose, I have located a recently-painted one at a small, unattended airport near me (Palmyra, WI) and plan to head there tomorrow or the next day for a swing:



As for deviation, I understand that is usually accounted for with a compass deviation card, which records what course to steer for a true heading of 0, 30, 60, ..., 330 degrees. The idea, as you know, is that the necessary correction can change for different courses.

I had been thinking about that issue too after reading up, and decided that a regular compass deviation card -- the kind I just described -- would be inappropriate for highway travel, since I can't choose my steering direction freely on a highway. But there is nothing to stop me from making at least an approximate "reverse" card, which would indicate my true heading for the indicated points 0, 30, 60, ... degrees on the compass. Since I'll be using the compass rose to try to a better job on the basic variation adjustment, I'll probably go ahead and make such a deviation card unless I get tired of repositioning my bike, or get chased away. Of course, there is probably little real value in doing this, and I have no expectation of posting this card below my compass as is done in aircraft. Enough is enough!

Moto

P.S. I don't know what a scissor magnet is, but would be interested to learn. The compass contains pairs of magnets on rotating shafts.

[n3303j]

Compasses read magnetic north.
Charts are drawn in true north.
Aviation charts show the difference between magnetic and true north for a given area.
This is variance. You correct for variance when navigating from an aviation sectional chart.

Compasses are not perfect.
The errors are noted on a deviation card after the compass is swung.
You use the deviation numbers to select a compass reading that will fly you on the magnetic heading you calculated from your charts.

That being said I have the Formotion  compass on the EV I bought last year. It pointed north all the way from Massachusetts to Tennessee  and back last month. Sounds like a few people have had good luck calibrating it. I'll probably give it a shot. Compasses are a fun way to explore. Used one on the bicycle. Would ride west 3 hours, south 3 hours, east 3 hours then north 3 hours and see how close I ended up to home base. Do the same on the bike but just using the sun. Clouds and noon are always there to keep it interesting 

[rodekyll]

Judging from some of those Kansas roads, you're putting more thought into the direction of travel than they put into the direction of build.  Have you noticed how they go straight for 120 miles and suddenly do a 90º right for a few yards and then another 90º left?  It's like they started building from both ends toward the middle but nobody calibrated their compass.  Left to their natural inclinations they would have bypassed.

If you were prepared to settle for a gps 'compass' that only resolves to cardinal points, and if your intent is to know which road at the intersection trends in what direction, what's the fuss about calibration?  If the road trends south, does it matter if it's 175º or 185º?

 

[BRIO]

Thanks for the "tasteful" comment.

The compass is easily adjustable for variation, and suitable for the compass swing procedure that I've just been reading about. In fact, because of Kirby's earlier mention of having calibrated his compass (the same model) on an airport compass rose, I have located a recently-painted one at a small, unattended airport near me (Palmyra, WI) and plan to head there tomorrow or the next day for a swing:



As for deviation, I understand that is usually accounted for with a compass deviation card, which records what course to steer for a true heading of 0, 30, 60, ..., 330 degrees. The idea, as you know, is that the necessary correction can change for different courses.

I had been thinking about that issue too after reading up, and decided that a regular compass deviation card -- the kind I just described -- would be inappropriate for highway travel, since I can't choose my steering direction freely on a highway. But there is nothing to stop me from making at least an approximate "reverse" card, which would indicate my true heading for the indicated points 0, 30, 60, ... degrees on the compass. Since I'll be using the compass rose to try to a better job on the basic variation adjustment, I'll probably go ahead and make such a deviation card unless I get tired of repositioning my bike, or get chased away. Of course, there is probably little real value in doing this, and I have no expectation of posting this card below my compass as is done in aircraft. Enough is enough!

Moto

P.S. I don't know what a scissor magnet is, but would be interested to learn. The compass contains pairs of magnets on rotating shafts.

You say your compass is accurate to within 10 degrees which seems acceptable and a pretty good result considering the amount of metal and a nearby instrument cluster. This is just Gee-wiz banter.

Compass variation is simply the difference between true north and magnetic north in your locale. As you move away from your theater you will have to apply a variation correction factor in addition to the local calibration. Of course this is pointless on a motorcycle where you won't be too concerned about a few degrees.

Deviation is the compass error imposed by the local magnetic fields created by the vessel and the compass itself. Unlike variation this error isn't constant (i.e. add 8 degrees). Since the needles alignment with nearby magnetic fields change deviation varies with the direction of the vessel. Compasses that allow for deviation typically contain sets of magnets (scissor magnets) that allow for adjustment in more than one azimuth section. The compass is adjusted through the compass swing procedure and the remaining difference is applied to a correction chart. I saw the effect of this on a sailing trip where I bought a pair of used large speakers and stowed them under the cockpit. It made a noticeable difference!


Your post inspired me to get a portable compass myself. I decided to get a strap compass since I intend on combining my riding with hiking.

http://www.glensoutdoors.com/silva-wrist-band-compass.html?gclid=CjwKEAjwp-S6BRDj4Z7z2IWUhG8SJAAbqbF3e8Tusm700pNyPnEsAxNHek0Q_Ov1cwjWnn1C-CkIDhoCzYzw_wcB

[Moto]

...
That being said I have the Formotion  compass on the EV I bought last year. It pointed north all the way from Massachusetts to Tennessee  and back last month. Sounds like a few people have had good luck calibrating it. I'll probably give it a shot.

A couple of other ideas for you if you have any trouble calibrating this time (aside from my gauss meter recommendation). Renthal makes some nice looking and apparently high quality aluminum streetbike handlebars in a few different bends, available on Amazon for about $54. I considered getting a set at first. I found this post from a bicyclist who reported no luck with a handlebar compass on his "all steel" bike and complete satisfaction with the same compass on his bike with aluminum handlebars: http://forum.cyclinguk.org/viewtopic.php?t=61710.

On the advice of more than one previous poster, I considered degaussing. I can report that waving the back of my 120w soldering gun around the problem area had no apparent effect. Reading up on the topic, I concluded that more amperage would be needed, and that successful degaussing might be a bit more involved than I had hoped.

Moto

[Moto]

Judging from some of those Kansas roads, you're putting more thought into the direction of travel than they put into the direction of build.

I ride mostly here in western Wisconsin, with lots of twisty and confusing roads. Not Kansas.

If you were prepared to settle for a gps 'compass' that only resolves to cardinal points, and if your intent is to know which road at the intersection trends in what direction, what's the fuss about calibration?  If the road trends south, does it matter if it's 175� or 185�?

I already said I'm happy with my +/- 10 degree calibration. The visit to the airport compass rose is just for fun.

[Moto]

Your post inspired me to get a portable compass myself. I decided to get a strap compass since I intend on combining my riding with hiking.

http://www.glensoutdoors.com/silva-wrist-band-compass.html?gclid=CjwKEAjwp-S6BRDj4Z7z2IWUhG8SJAAbqbF3e8Tusm700pNyPnEsAxNHek0Q_Ov1cwjWnn1C-CkIDhoCzYzw_wcB

That's a good=looking compass, and it could save your life someday. Did you read about the 66-year old hiker who stepped away from the Appalachian Trail recently, got lost, and died after 20-some days?...

You can never have too many compasses. Maybe I need a Silva watch strap compass too.

EDIT: The hiker's name was Geraldine Largay. The official report of the investigating officer does show a photograph of a small compass she carried: https://assets.documentcloud.org/documents/2842887/Geraldine-Largay-Report-Exerpt.pdf. (The last photo, at the end of the report.) Her fatal mistake, it seems, was seeking higher ground for a good cell phone signal, instead of heading downhill for a road or stream.

[BRIO]

That's a good=looking compass, and it could save your life someday. Did you read about the 66-year old hiker who stepped away from the Appalachian Trail recently, got lost, and died after 20-some days?...

You can never have too many compasses. Maybe I need a Silva watch strap compass too.

I haven't but it makes me feel like it was $10 well spent. That is where I'm going in august.

[Moto]

That looks really nice. 

Did I miss where you posted the model number of the compass you purchased?

I'm not sure of the number. Here's a link. It's on closeout, sale priced at $50 plus shipping. Not cheap. However, it's the best compensated compass I know of for a motorcycle right now. (Marlinsclocks.net offers a different one, but it's really a marine compass, complete with calibration instructions for a boat!)

All of Formotion's products are being withdrawn from retail sale. So, love em or hate em, this seems to be the last chance to get em.

Moto

http://www.formotionproducts.com/shop-1/black-compass

EDIT: I forgot to mention another, larger Formotion compass, on sale for only $15! Too large for me, I decided, but a good value:

http://www.formotionproducts.com/shop-1/compass-white

[johnr]

Frankly I'm a little amazed that the compass is accurate to +/- 10 degrees in that setting and I'm sure that will be good enough for your purposes.  Hell, if you are hand steering a yacht to a (properly swung and adjusted) compass course and you can keep within +/- 5 degrees you are doing very well indeed!

[Moto]

Frankly I'm a little amazed that the compass is accurate to +/- 10 degrees in that setting and I'm sure that will be good enough for your purposes.  Hell, if you are hand steering a yacht to a (properly swung and adjusted) compass course and you can keep within +/- 5 degrees you are doing very well indeed!

Well, +/- 10 degrees was my rather quick judgement after calibrating in a parking lot using a hand compass reference. I'm sure the headings were within two tick marks (10 degress) of the nominal directions on the four cardinal points. But I'm not so sure the motorcycle was positioned accurately enough to make those observations worthwhile. I'll report back on my results on the airport compass rose. They may not be so good!

I'm uncertain how best to position the motorcycle on the compass rose. Suggestions welcome.

[Moto]

I did ride down to the airport compass rose at Palmyra, WI, to recalibrate my new compass today.

The short report is:

True         Compass    Compass
Heading    Bearing     Deviation
N     0              10        +10
E    90             90             0
S  180           193         +13
W 270           275           +5

Not quite as good as my initial report of +/- ten degrees, but close.

I did the full compass swing, as I understand it:

1. Point bike N, adjust compass to read 0 degrees
2. Point E, adjust it to read 90
3. Point S, remove half of any difference from 180
4. Point W, remove half of any difference from 270.
5. Cycle through the 12 available points of the compass rose (0 30 60 90 ...) and record the readings.

Here is the record from step 5:

    true   compass   deviat 
       0        10         10 
      30        43        13 
      60        55         -5 
      90        90          0 
     120       118       -2 
     150       160       10 
     180       193       13 
     210       211        1 
     240       243        3 
     270       275        5 
     300       290      -10 
     330       325       -5 

The deviations now seem to be all over the map. Taking all the variability into account (with some interpolation*), I selected these as my working compass corrections:

Compass
bearing                 correction
N (0)                         -5
E (90)                         0
S (180)                    -10
W (270)                      0

Moto

*I interpolated by eye from this smoothed fit:

[Moto]

Update: I found my compass calibration was not as good as I reported once I started riding around, so I'm updating this thread.

At 50 mph the compass bearing could be off by up to around 45 degrees from the value I obtained with the bike stationary at the airport compass rose. I could tell this when I was on true N/S or E/W roads. I tried disconnecting the speedometer cable in case the spinning magnets inside were the problem, but no luck.

So I decided to calibrate to the readings I got at 40-50 mph on N/S and E/W roads, working from an intersection where two such roads met. I got the bearings to within about 15 degrees on all four cardinal points, while under way, though this threw off the stationary readings.

Of course using N/S and E/W roads requires some thought about the difference between geographic and magnetic north, but in my area the two are only 2 degrees apart, so it didn't matter much.

Moto

[Testarossa]

How about the magnetometer-driven digital compass in my Android phone? Is it more or less accurate than a whiskey compass?

[Moto]

How about the magnetometer-driven digital compass in my Android phone? Is it more or less accurate than a whiskey compass?

An Android phone's magnetometer-based compass is just an uncompensated magnetic compass, and should work fine away from the bike.

I think "whiskey compass" refers to the compensated type of magnetic compass installed on an airplane (which is fluid-filled, sometimes with alcohol, maybe explaining the name). If so, the Formotion compass is a simple whiskey compass.

Your phone's compass would be a good standard for navigation if you got off the bike, better than the compensated Formation compass. But you would need to know your magnetic declination (or variance) to use it to find true geographic headings. You can find magnetic declination maps by googling.

[Testarossa]

The compass function in my gps app allows me to switch between magnetic and true readings. This implies that it refers current position to a declination map and corrects accordingly.

[Moto]

The compass function in my gps app allows me to switch between magnetic and true readings. This implies that it refers current position to a declination map and corrects accordingly.

Yes, as I understand it, the reading is magnetic and is corrected by referring to your location, via GPS and a declination map. However (of course), it can still be thrown off by nearby magnetic fields, meaning the corrected reading will be wrong too.

[Moto]

Those with newer bikes might like to know the same Formotion compass works just about as well on my Griso, being accurate to within about 15 degrees at each cardinal point. The same clock mount also works to hold the compass, needing a 35mm screw this time. (But this time you can see a lot of the screw extending below the compass, in the picture.) The magnetic field at the mounting point measured about 0.5 Gauss this time, similar to the successful mounting point for the T3.



I just ordered a second compass. A cheap thrill compared to some others I could name.