dan williams Posted February 21, 2010 Report Share Posted February 21, 2010 OK so I'm sitting here thinking I'd like to set up a way to monitor rotational speed of the crankshaft. An optical sensor being the easiest method to implement and a resolver being the hardiest. Knowing that the crankshaft speeds up and slows down as it goes through the two stroke cycle it occurs to me that this would be a very sophisticated way to monitor engine fuel and ignition requirements. From instantaneous crank acceleration one can deduce engine load from the ratio of how much the crank slows between power strokes and how much it speeds up during the power stroke. One could also sense pre-ignition and detonation as short-violent deceleration just prior to the power stroke. Could even be used for a rudimentry form of traction control. Then I started thinking of another modification to the basic trials engine. Why are the primary drive gears round? Because they Quote Link to comment Share on other sites More sharing options...
pete_scorpa3 Posted February 21, 2010 Report Share Posted February 21, 2010 Lost me at the first sentence! Congratulations to the GF for her job offer Quote Link to comment Share on other sites More sharing options...
gjbiker Posted February 21, 2010 Report Share Posted February 21, 2010 Hi Dan, I can get my head round the first bit but the just can't quite fathom the idea of a primary gear being anything other than round ? Surely an eccentric profile meshed to another would necessitate the need for carrying shafts to move in a timed and opposed latteral manner to facilitate a constant mesh? Even then the end result would be the same as a round gear? Could you elaborate and maybe even draw a picture? GJ Quote Link to comment Share on other sites More sharing options...
toofasttim Posted February 22, 2010 Report Share Posted February 22, 2010 Dan, use a hall effect sensor, cheaper and more robust. Quote Link to comment Share on other sites More sharing options...
slapshot 3 Posted February 22, 2010 Report Share Posted February 22, 2010 Hi Dan,I can get my head round the first bit but the just can't quite fathom the idea of a primary gear being anything other than round ? Surely an eccentric profile meshed to another would necessitate the need for carrying shafts to move in a timed and opposed latteral manner to facilitate a constant mesh? Even then the end result would be the same as a round gear? Could you elaborate and maybe even draw a picture? GJ FFS Gav, don't encourage him..!! Actually I love reading some of Dan's Ideas, the power of imagination, it's what keeps us going!! Quote Link to comment Share on other sites More sharing options...
dan williams Posted February 22, 2010 Author Report Share Posted February 22, 2010 Heh heh Check these out. Rather extreme examples but fun. http://www.travellingcurves.com/curves/# Spirograph anyone? Quote Link to comment Share on other sites More sharing options...
gjbiker Posted February 22, 2010 Report Share Posted February 22, 2010 FFS Gav, don't encourage him..!! Actually I love reading some of Dan's Ideas, the power of imagination, it's what keeps us going!! Sorry Donald, but I also love innovative ideas I just need them explained 'cos I'm a bit fick Thanks for links Dan - brilliant when you see it in action and so much easier for the likes of me to understand. I assume an eccentric rear sprocket with a compensator for the chain would have the same effect? I also reckon it would make my riding even more erratic than it already is? Nightshift and too much black coffee - don't burn me at the stake - just be glad you're not me GJ Quote Link to comment Share on other sites More sharing options...
copemech Posted February 22, 2010 Report Share Posted February 22, 2010 I would doubt all this, as smoother application(or reduction) of power is what negates breaking of the available traction, not the opposite! This is why some of the mont 4T riders complain, as they want to ride clutch out and let the power pulses work. If you want to create an ABS/ traction control system, connected to throttle, it is much easier done via wheel speed than crankshaft speed. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 22, 2010 Report Share Posted February 22, 2010 (edited) A similar idea to Dan's was used in the 1980s on off-road bicycles to compensate for the cyclic variation in torque applied to the front sprocket. The sprocket on the pedal crank was made oval shaped and it was called a "biopace gearset". Changing the shape of the sprockets on a trials bike wil not achieve what Dan suggests because he is trying to alter the shape of the motor speed power pulse. Edited February 22, 2010 by feetupfun Quote Link to comment Share on other sites More sharing options...
chewy Posted February 22, 2010 Report Share Posted February 22, 2010 Didn't the old bultaco use a primary chain with a slipper tensioner.....they were always regarded as smooth pickup motor...... perhaps a belt insted of chain would be good.....I guesse fitting it into modrn small lightweight is downside if this... I just wonder even if one could measure variatoins of crankshaft speed in real time how this information coulf be processed and used to smooth out the motor( 1 rev of a 0.1 mtr dia wheel at 1000 revs is ?roughly pye d n over 60 work that out through....then look for accelerations/decelerations then what?). Only yesterday I was discussing with a good rider of old bikes timing the "bang" to make the bike work..... with a four stroke it is a more important skill than a 2 stroke. all very interesting but surely a major part of riding skill is using what you have more effectivly than the next guy!. As it is most sections are too difficult for many riders and this has to be due to bike development which seems to be largely centred around top/good riders who will always be able to get more out anything they ride than your average punter. Hopefully I've missed something in your reasoning regards wanting to look at this perhaps I.m "resisting" because finding grip is one of the last tools in a riders kit to dissapear with age...I.m definitly old enough to know this! Quote Link to comment Share on other sites More sharing options...
kramit Posted February 22, 2010 Report Share Posted February 22, 2010 I think Dan started celebrating before the celebration!!!.......I'll have some of what he's been drinking please....... Quote Link to comment Share on other sites More sharing options...
nzralphy Posted February 22, 2010 Report Share Posted February 22, 2010 Go for it. There is nothing saying an optical sensor wouldn't work, but it will be working mighty quickly with a 2T compared to a 4T. The down side of having a eliptical output gear is that it would have to have a matching eliptical driven gear thus negating any benifit. if you could match an eliptical gear to a round gear then you'll get the benifit. Now if you could do that then you will be faced with varying gearbox speed rather than varying output torque/power. How about a variable turbo pressure gate mated to rear traction! Ralphy Quote Link to comment Share on other sites More sharing options...
atomant Posted February 22, 2010 Report Share Posted February 22, 2010 (edited) So what you want to do is smooth out the power cycle? so whats the flywheel doing then? A high res encoder could get the info you need but what you do with it becomes rather tricky I reckon also, something that I have dabbled in, is for a smoother power delivery you might want to consider a wa-nkel engine Edited February 23, 2010 by AtomAnt Quote Link to comment Share on other sites More sharing options...
houseape1000 Posted February 22, 2010 Report Share Posted February 22, 2010 Sorry to butt-in, but I wonder why no-one has made a diesel engine trials bike. Quote Link to comment Share on other sites More sharing options...
slapshot 3 Posted February 22, 2010 Report Share Posted February 22, 2010 (edited) A similar idea to Dan's was used in the 1980s on off-road bicycles to compensate for the cyclic variation in torque applied to the front sprocket. The sprocket on the pedal crank was made oval shaped and it was called a "biopace gearset".Changing the shape of the sprockets on a trials bike wil not achieve what Dan suggests because he is trying to alter the shape of the motor speed power pulse. It's an old idea that gets "re-cycled" ( ) on a regular basis Rotor Q Rings and O.symmetrics chainrings now this one seems daft even to me..... Edited February 22, 2010 by Slapshot 3 Quote Link to comment Share on other sites More sharing options...
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