redbug119

I bought a Stem Captain compass and I have been having problems with it being magnetized on my Trek Verve 3 bike. I have been changing out all the screws I can to non-magnetic ones. But I still have not had any luck with it. Does anyone have any suggestions on how I can work around this problem?

LesterOfPuppets

If it has a fork with a steel steerer, I don't think you'll have any luck. You might be able to calibrate it in a fashion similar to how they calibrate boat compasses, with strategically placed steel bits taped to the headset spacers, headtube, bars, stem as needed to get good readings.

EDIT: I guess compass adjusters on boats are usually actually magnets, not just hunks of steel.

VegasTriker

I doubt if any of the screws themselves are magnetic. There is no reason a bike manufacturer would use anything that is magnetic on the frame. However it is correct that you can't mount a compass near anything of substantial size that is made of steel, except for stainless steel which does not attract a magnet. The tip of the needle in a compass is magnetic and that is why it points toward magnetic north in the northern hemisphere. Unfortunately when you put a compass next to a chunk of steel like a headtube it will mess up the reading because it points toward the steel instead of magnetic north. Just confirmed it with a quality backpacker's compass next to a piece of steel and the readings were wonky. The closer to the steel the more off the reading.

Steve B.

Go carbon ?

Tourist in MSN

I had a compass in a bell, got rid of it.

Buzzkill53120

A compass needle is magnetized, that’s how it points to magnetic north. Any ferrous materials (with the exception of stainless steel) in the vicinity will affect its accuracy. Stem bolts, cable housing, etc. Surrounding hardware does not need to be magnetic to effect a compass.

Note from Stem Captain website: “IMPORTANT NOTE: Steel frames or components and electronics mounted near the compass may cause magnetic interference. The Compass 3.0 includes a non-magnetic stainless steel stem cap bolt that must be used to mount the base.”

Barry2 

Just an FYI
My stainless steel fridge is covered in magnets. It’s only certain types of stainless that are non magnetic.

Barry

2_i 

The only way you can make the compass work is to put it on some arm stretching away from any magnetic material, at least 4"/10cm long. Magnetic does not mean that it is magnetized, just that it attracts a magnet. However, when you ride, the magnetic needle wobbles, moves around. It is hard to get a useful reading. I speak from actual experience - my compass was held on an alu extension. If you really need to rely on a compass, you can keep one on your body and take a reading when stopped and holding the compass away from any magnetic material

Most common stainless steel is not magnetic, at least for practical purposes. For the fridge you may want to use a less standard one to keep your customers happy sticking magnets.

Polaris OBark

Anything with iron in it is going to be ferromagnetic. All steel contains iron.

A carbon stem with steel bolts may still be problematic; there is no reason it should be any better than an aluminum stem.

Garmins usually have a compass display, FWIW.

cuevélo

Nope, austenitic stainless steels like 316 are not ferromagnetic.

https://www.kjmagnetics.com/blog.asp?p=stainless

Polaris OBark

The iron is ferromagnetic due to the four unpaired electrons in its d-orbitals. The only way you are going to change that is to put the iron in a very strong octahedral crystal field environment.

cuevélo

I can only find sources that say that austenitic stainless steel is not ferromagnetic.

Polaris OBark

I think it says it is weak.

I am not a materials scientist, but I am genuinely curious how this could be achieved. I'll look further when I get a chance.

As for the bike, the easiest way to assess whether the stem bolts are the issue is to take one out and see if holding it close to the compass needle does anything significant. I would be very reluctant to replace (normal) steel stem bolts with titanium, aluminum, or brittle stainless steel bolts, for safety reasons.

Tourist in MSN

Above where I said that I had a bell with a compass that I eventually chucked, I did not try to figure out what kinds of stainless steel my stem bolts were, I simply could not find a place on my handlebar where the compass gave a good reading after holding the compass in many places trying to find a good spot for it. Took less than a minute to find out that it was not going to work.

Some stainless is more likely to affect a compass than other kinds of stainless. And you have stem bolts, star nut in a steerer tube, steerer tube, brake lever bolts, bearings in a headset, and other hardware that may affect a compass like cables (both inner and outer), etc. A compass in a stem cap is a good idea if it would work, but that does not always work.

redcon1

The accuracy of a small compass mounted on the stem would be questionable regardless of any magnetic effect from frame or mounting material. I agree with other posters- use a decent lensatic or baseplate compass tucked into your jersey when you stop to get your bearing. Ans stand far enough away from the bike to ensure no effect.

Or, get a Garmin with a compass feature.

Ghazmh

I thought the Verve had an aluminum frame. Maybe the compass has an aluminum magnet?

LesterOfPuppets

Steel stem bolts, steerer, HS bearings, starfangled nut, etc.

Iride01 

Actually it also depends on the magnet too. The neodymium super magnets stick to most common types of stainless steel just as well or better than a common magnet sticks to plain steel.

And I think that many stainless steel fridges are just a thin layer of stainless steel on top of steel.

Inusuit

I'm not a metallurgist by trade so I don't know about different kinds of stainless steel or different types of magnets. A cheap magnet on one of those clamps that you use to hang stuff from the refrigerator sticks strongly to two different stainless steel firearms. My Garmin has a compass but I usually know where I'm going and which direction is north.

Tourist in MSN

Thanks, I needed some good humor.

Moe Zhoost

Navy ships compensate for compass deviation due to iron containing materials by the use of Navigator's Balls. Perhaps you could rig up a scaled down version for your bike.

redbug119

Got an extender type thing that is designed for a Garmin but works in this case! Thanks for all the replies and science explanations!!