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Post by yellowshark on Aug 21, 2008 19:55:02 GMT
Is there a fundemental, i.e. on the track difference between the two?
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Post by lesbaldry on Aug 22, 2008 6:53:33 GMT
Is there a fundemental, i.e. on the track difference between the two? A bushless question Pete??Blimey  Speak to Ed he runs both and should have the answers? |
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Post by Robin Howett on Aug 22, 2008 8:06:44 GMT
My GM speedo can run sensored or sensorless, the main difference being that when running sensorless the speedo timing can be adjusted from 0 to 30 deg on the speedo this is usefull for mod running when run time is the big issue (it's some of the reason why Chris Grainger is BRCA champion) The problem with that tho is alittle top end rev's is lost..... so with a 3.5 brushless thats not a problem but with a 13.5/ 10.5 thats not good.
Some of the mamba speedos can work sensorless but they had an almost switch like responce at the low end, not good.
Basically the sensored speedo/ motor's mostly seem to be flavor of the moment, the only notable advantage for sensorless is the ability to run in the wet, (hall sensors hate the wet) assuming you can water proof the speedo enough....
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Post by TryHard on Aug 22, 2008 8:16:16 GMT
right, here we go... quick brushless basics. As you know, brushless works by altering the current in the coils electronicaly, rather than mechanically as in a brushed motor. To do this properly, the esc needs to know which phase the rotor is in.. there are two methods to this. 1) Sensored. Motors have hall sensors in them, which feed information back to the esc detailing the exact position of the rotor in the can at any point of the rev range. Hence why it's crucial to have clean sensors in the motor, and a good connection of the sensor cable.. otherwise you'll get interference and the dreaded cogging. 2) Sensorless. Relies on the back emf current in the motor to position the rotor. Obviously, this requires some current going through the motor to start with... which it isn't when the motors stopped! Hence why a number of sensorless speedo's and motors (Mamba, Tekin R1 Pro) have issues starting, where the motor coggs initially to figure out the position of the rotor... there have even been instances of cars going backwards on the start line as the esc gets confused! However, despite this, the big advantages in sensorless' favour is that it is a a) more efficient, which in mod is crucial for runtime and b) more resistant to wet weather (the hall sensors of a sensored system do not like water at all). So, whats the difference on track? not much... sensored is better in the lower rev range, and sensorless better higher up (more efficent). This is why you can see a number of speedo's that switch modes up and down the rev range (GM Genius, Speedpassion GT & LPF, Tekin RS Pro), using sensored operation for the initial and lower rev range (smooth starts and better positioning of the rotor), before switching to sensorless in the high rev regions. A good article by Novak here, but bear in mind it's written by a company that makes a sensored only system... and technology has moved on a bit since it was written. Got any more questions, happpy to discuss it at the weekend  HiH Ed |
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Post by Matt Haskell on Aug 22, 2008 8:31:10 GMT
informative reply.......cheers
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Post by lesbaldry on Aug 22, 2008 10:32:57 GMT
informative reply.......cheers Blimey Matt ,you believe a bloke that drives a blue car..Dodgy.. LOL Ed  |
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Post by Matt Haskell on Aug 22, 2008 12:19:15 GMT
nah, just lulling Pete into a false sense of security ;D
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Post by TryHard on Aug 22, 2008 13:38:43 GMT
nowt wrong with blue... it's these people who can't stick to one colour I wouldn't trust... indecisive  |
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Post by lesbaldry on Aug 22, 2008 14:27:04 GMT
nowt wrong with blue... it's these people who can't stick to one colour I wouldn't trust... indecisive Split personality too I say..half man half dog  |
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Post by yellowshark on Aug 23, 2008 18:23:50 GMT
Thanks for that guys, particularly Ed. I read an interesting article by a guy working for Microchip Technology Inc., all about algorithms for sensorless speedos which suggested that sensorless was more efficient (or is that effective?) because it has more information to work with that a sensored setup – but as you suggest, it wasn’t at all clear to me (not being into electronics) what happened at the moment of start when there is no speed in the motor to provide the back emf stuff. It talks about needing to monitor all 3 phases so that if there is a “detection” error on the first phase the software can correct itself. Whilst a software expert, that’s starting to get into non comprendo speak to me ‘cos I don’t understand the physics, so I was interested in the track realities.
I had got the impression the current fad was for sensored but we are hoping to run a prototype or 1st off the production line waterproof sensorless speedo at the Cotswolds, so it will be interesting to see what the reality is, if it happens.
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Post by TryHard on Aug 24, 2008 4:43:15 GMT
put it this way, I know a friend of mine who ran a Tekin R1 Pro (the sensorless version), and coul never get it too work as well as his Nosram ISTC.... he was one of the guys who had it go backwards! Tekin did try a number of software updates to solve the startup/low revs issue, but it never really went away, especially on the higher wind (13.5, 17.5) motors... hence the RS.
A lot of peope argue that the plane guys have been using sensorless for a while now, so why not track... will thats a simple arguement to refute, as us track boys use the the full rev range, often many times in a lap, whereas the plane boys are pretty much constant revs, most of the time... hence why sensored is currently more suited to 1/10th touring.
HiH
Ed
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Post by yellowshark on Aug 24, 2008 9:10:08 GMT
Not surprised ED, thanks for the factual anecdote. Software guys think they can overcome anything but sometimes you just cannot beat a hard wired solution
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