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Quote:

Originally Posted by Old Git ray (Post 80688)

Actually we don't...

Actually, we do - it's the same bl00dy thing - different name!

I've used it in the past to give better accuracy to maritime navigation - OK, I use it to get back to to good fishing marks.

Quote:

Originally Posted by Gas_Up_Lets_Go (Post 80795)

Actually, we do - it's the same bl00dy thing - different name!

I've used it in the past to give better accuracy to maritime navigation - OK, I use it to get back to to good fishing marks.

I know that, I was just trying to make out I was clever and failed...

and just a bit extra to that - when GPS first appeared selective availability (the US govt. scrambling the GPS signals) was built in to stop foreign users and naughty civvies from doing things with it they shouldn't. That 'feature' though was disabled as of May 2000 and the govt. publicly said they won't turn off or otherwise disable the system. Hence about a year ago our aviation industry finally woke up to the value of the system and started designing and trialling various GPS approaches at some UK airports. About time; the Americans have been doing it for years. NDB approach to a dodgy fading beacon at night with low cloud and strong crosswinds or a nice GPS approach in the same? No brainer. Don't get me started on the issue!
Regarding the 2D vs. 3D speed computation, interesting question. Next time I'm able I'll try some zero groundspeed autorotations, see what happens. Standard 1500 - 1600 ft/min ROD = about 18mph if my maths is correct

Quote:

Originally Posted by JMo (Post 79169)

That's a comprehensive report, thanks Ray (I had my tank up the other day too, it's a bit of a fiddle as you say - I can see the price to check/adjust the valves being pretty high labour wise...)

As a thought - Presumably the speedo reads off the gearbox output shaft? - hence the smaller front sprocket spinning faster shows a higher top speed right?

Now correct me if I'm wrong (I'm no mathematician) but you kept the 15T front and you put a larger rear sprocket on instead (say 47 teeth), the rear wheel is now effectively turning slower for the same engine revolutions? - would than not correct the speedo over-reading?

If so, perhaps this is the problem - that the bike actually ought to be running slightly lower gearing (that is using a larger rear sprocket), but they put on a 45 tooth in an effort to keep the revs down at speed and improving MPG?

I'm going to try it next time I fit a new chain and sprockets...

xxx

3 teeth extra at the back = 1 tooth less at the front. You would need a longer chain, changing the front to one less you could get away with using the same chain. Having a smaller front sprocket would also wear out quicker.

Hi Rick -

This is all true, I realised my maths was up the spout after I'd written that...

Certainly lowering the gearing causes the speedo to over read even further, although for anyone interested, once you fit an 18 inch rear wheel, I'd say the stock gearing would be pretty much bang-on - I am running 15/46 with the 18 inch rim and it only over-reads by a couple of miles per hour now...

Of course the 18 inch rim also has had the effect of gearing it higher, so i will be needing that 48T rear sprocket after all, just to get it back to somewhere near normal!

xxx

Just used this thread to help me fit the Speedo Healer I took off my old FZ6 onto my new Tenere. Very helpful.

Cheers!

Quote:

Originally Posted by crazyclimber (Post 81819)

As an extra to the GPS discussion, neither the Americans or the UK military use what is effectively public GPS sats, they used to use them in the beginning many moons ago (The military actually funded them) but now they have there own ones that give out a highly encrypted signal which are very accurate and which all the new drones use for navigation.

I'd be careful using a sat nav to calibrate a speedo, it's not just down to the number of sats that it can receive it's also the speed at which the unit updates it's display which is all down to an onboard timing chip, if they were that accurate the Police would use them as a sat nav unit is about a tenth of the price of the calibrated speedos that they have to use in the traffic cars.

Soooooo... these speedo healers - bearing in mind I'm now running 14/48 with an 18 inch rear wheel - God knows what speed I'm actually doing! (actually I do know, as I have my IMO fitted which is bang on for the 21 inch Michelin Desert, and the speedo is about 11mph over at a true 70mph)...

Where can I get one from and also, is there anything less than �79? on ebay... (eek!)

xxx

edit: ah found one for �55 that will do the job - http://www.speedotuner.com/ - presumably based on what n0ct0 says, one for the FZ6 will work?

Yes, the harnesses are the same. Mine came straight off my FZ6 and went straight on the Tenere. Same connectors.

Just to throw a curve ball on this thread: how do Yamaha (and all other manufacturers come to that) calibrate the speedos in the factory? I would have thought that any slight variation between the values of each speedo's electronic components might require something built in to the circuitry in order for the factory to calibrate each speedo.

Anyone fancy taking their speedo apart in order to locate the PCB mounted variable potentiometre(s)?!!

regards,
Rick