scooby dooby doo Posted January 3, 2003 Share Posted January 3, 2003 but to get to the rear wheel it needs a fairly tortuous path to get there without being on the way. eg dash - bulkhead - down to the tunnel - along the tunnel - through the rear bulk head - to the dedion tube (how much slack so it can move ok?) - round the hubs etc - wheel.... HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Morls Posted January 3, 2003 Share Posted January 3, 2003 Why isn't the prop the obvious place? Esp. on a BEC where there's a lot of prop. Mark ☹️ My Caterham Silver Jubilee No. 7 is for sale ☹️ Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 3, 2003 Share Posted January 3, 2003 harder to attach to the prop (as the glue has to provided ALL the centripetal force) and it moves about a bit so its harder to get it to read reliably. HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Morls Posted January 3, 2003 Share Posted January 3, 2003 Sorry, I'm in work mode, therefore a bit slow 😳 Because of the rotational speed (surely offset by the small radius?), of the prop or because on a disc is it butted up to a ridge to help offset the centripetal force? Mark ☹️ My Caterham Silver Jubilee No. 7 is for sale ☹️ Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 3, 2003 Share Posted January 3, 2003 because the glue takes all the load. on a wheel rim you can get the rim to take all the load and the glue justs stops it moving sideways. on a hub you can at least make the load purely lateral so its a lot easier than the propshaft. I know of one builder with a sensor on his propshaft and 6 magnets. every few miles to sva one fell off and he recalibrated. luckily 2 survived for the test and there was still one left when he got home. he's a competant builder as it was his second 7 (westie then a dax) so i assume its just not a nice place to put magnets. small radius makes its worse - F = mv^2 / r. so smaller radius means bigger force. I think i worked it out at well over 1000 times the force of gravity... maintaining a 1mm gap to something thats mounted on rubber bushes (ie the gearbox) is tricky as well - if the prop moves it might wipe out the pickup. HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Paul Thompson Posted January 3, 2003 Share Posted January 3, 2003 Propshafts do mangle sensors. I have done two so far when I slipped off the black stuff and am looking to change the location to the front disc. Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 3, 2003 Share Posted January 3, 2003 i put mine on the wheel as i was worried about the disk getting too hot. a few 100 degrees will melt the plastic the magnet is mounted in and i expect start attacking the araldite as well. or is that not a problem 🤔 HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Trevor Phillips Posted January 3, 2003 Share Posted January 3, 2003 Mine's on the wheel also. With the Sigma not sure if you might have difficulty calibrating it down to a small propshaft circumfrence and still maintaining accuracy. It would be useful to buy extra sensors for other wheel sets. Are they available anywhere? Racing pics and items for sale here Link to comment Share on other sites More sharing options...
SvenDriver Posted January 3, 2003 Share Posted January 3, 2003 The sensors are very simple magentic reed switches. Most bike shops will sell you a spare mounting kit (as they are called) for under a tenner. If all you need is a magnet to stick on the wheel then any small magnet will do. Link to comment Share on other sites More sharing options...
Silver 21 Posted January 3, 2003 Share Posted January 3, 2003 joining this thread a long way in and it may have already been covered but seeing hoopy's comment about the platic covering on the magnet. The best bet is to buy a magnetic door latch from B&Q, remove the magnet from the platic housing and use this, much more contact area to stick the magnet to the inside of the front disc. I've also got a Sigma and works great, magnet has fallen off once but that was after a 360 spin and whilst travelling backwards at high speed at the Oulton Trackday last year 😬 😬 Graham Competition Secretary Lydden, Curborough, MIRA, Llandow, Curborough, Aintree...What more can you ask for? Link to comment Share on other sites More sharing options...
stevefoster Posted January 4, 2003 Share Posted January 4, 2003 The best way is to bust the Sigma magnet out of the plastic cover ,key it and glue it straight on to the rim. The sigma magnet is a small cylinder and is quite powerful. A door latch magnet sounds to big to me but I may be wrong. You can buy spare Sigma magnets from bike shops for a couple of quid a piece. I have one on all RF's of my sets of my wheels. /Steve My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
Mick Day Posted January 4, 2003 Share Posted January 4, 2003 OK so the mech. speedo is binned: what do you use to seal the hole into the gearbox where the R/A drive used to live? Mick Link to comment Share on other sites More sharing options...
SvenDriver Posted January 4, 2003 Share Posted January 4, 2003 Go for the easy life. If you are ditching the speedo you can still leave the speedo caables in and just ditch the speedo. Why make work for yourself?? Link to comment Share on other sites More sharing options...
stevefoster Posted January 5, 2003 Share Posted January 5, 2003 No seal is needed. It is a selfsealing drive. Binning it all will save you 0.71kgs in weight. I posted 0.5 before but that was for the Vecta immobiliser. /Steve My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
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