hattymender Posted January 11, 2008 Share Posted January 11, 2008 For no particular reason other than I was bored while shopping I've bought a compass. Don't know why as I have a perfectly good sat-nav. Just a cheap thing but it's driving me mad. It works perfectly well 'hand held'. It works perfectly well in a Ford Escort. In a Land Rover everywhere is North. Unless it's on the middle seat when it will concede that not every direction is North. Just. If you're moving. It will work near the back door. But I'm not rigging up CCTV to see it. I'm assuming 1/2 ton of cast iron under the bonnet + iron oxide bulkhead may have some bearing. Putting it on middle seat has a large ferrite mass rotating below it, handbrake drum, which may be damping the engine's influence? Has anybody successfully fitted a compass? What's the trick? Bit of steel (e.g. a nut) strapped to it to balance the engine? Chucking it is the easy option but it's the principle. I've paid for it. It will be made to work. Could be another excuse to get a (aluminum) V8 though? Rich Quote Link to comment Share on other sites More sharing options...
Guest WALFY Posted January 11, 2008 Share Posted January 11, 2008 If it's a silva type compass it will always point mag N. Unless it has some outside influence. Being close to a veh will have some interferance with the reading. I always step away from the veh to take a bearing. Not sure how the dash mounted globe style overcome the inteferance though. Quote Link to comment Share on other sites More sharing options...
moose Posted January 11, 2008 Share Posted January 11, 2008 if you are bored have a read of this ..... compass info Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted January 11, 2008 Share Posted January 11, 2008 I was going to say, this is a well know problem, on boats anyway, and would be solved by having your compass 'swung' i.e. adjusted to read true. easy on a boat, where things stay still, harder with a vehicle with its contents changing regularly. Ultimately, as Walfy says, step away if you want to get a decent bearing. Quote Link to comment Share on other sites More sharing options...
hattymender Posted January 11, 2008 Author Share Posted January 11, 2008 if you are bored have a read of this ..... compass info I tried. But I got bored. The way it's raining I think the bit about tidal influence may be more relevant................................ Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted January 12, 2008 Share Posted January 12, 2008 Aren't they supposed to point North ? I always thought that was how they worked, rotate the compass until the N lines up with needle. Of course, I may be missing something that's quite important here. Mo Quote Link to comment Share on other sites More sharing options...
hattymender Posted January 12, 2008 Author Share Posted January 12, 2008 Aren't they supposed to point North ? I always thought that was how they worked, rotate the compass until the N lines up with needle. Of course, I may be missing something that's quite important here. Mo Doh! Yes you're right. Jack Sparrow had a compas that points towards what he wants, I have a compass that tells me where the engine is! Neither point north! Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 12, 2008 Share Posted January 12, 2008 Inside a vehicle the metal work and current carrying cables distort the magnetic field causing all sorts of problems. Vehicle compasses should have a couple of magnetic adjusters to fine tune the direction the needle points at and these should be set while the vehicle is running in its normal condition. It is easiest if the vehicle is parked facing north before adjusting. Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted January 12, 2008 Share Posted January 12, 2008 Doh! Yes you're right. Jack Sparrow had a compas that points towards what he wants, I have a compass that tells me where the engine is! Neither point north! Ah, I see ! Mo Quote Link to comment Share on other sites More sharing options...
Boothy Posted January 12, 2008 Share Posted January 12, 2008 Whilst holidaying on a cruise ship in the middle of the Med just of Morrocco,I ws treated to a tour of the bridge, where a periscope is fitted to the compass. The ships magnetic compass is situated at the highest possible point of the vessel up this bloody big high mast thing, where it has less magnetic influences on it and can only be normally viewed by the periscope. Load of carp because they don't use it, but it's there I suppose if every things else fails. So Hattymender, fit a periscope on a pole, end of problems but watch for low bridges and things. Your welcome Quote Link to comment Share on other sites More sharing options...
western Posted January 12, 2008 Share Posted January 12, 2008 Set it as NT has said above & try a 4 point swing, N,S,E & W, at work when we change an engine [single engine aircraft] or refit the fin a compass swing has to be carried out as soon as possible, normally a 4 or 8 point swing is sufficent, the compass detector unit lives inside the fin & has the rest of the aircraft in front of it. Quote Link to comment Share on other sites More sharing options...
Troddenmasses Posted January 12, 2008 Share Posted January 12, 2008 They are affected by all sorts of things - for example in the aircraft that I fly, the compass swing is only valid for one particular electrical set up - usually everything on. When you turn a powerful heater (pitot) on and off, the compass moves by 5 - 10 degrees. If you are accelerating or slowing down it mis reads massively. Just do what pilots do - use the GPS and follow the roads. Quote Link to comment Share on other sites More sharing options...
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