DIY_EFI Digest Monday, 9 December 1996 Volume 01 : Number 376 In this issue: Re: Flywheel/Encoder patterns Re: Flywheel encoder patterns Re: Flywheel/Encoder patterns Forwarded: Re: Flywheel encoder patterns re: Flywheel/Encoder patterns Forwarded: Engine braking???? Re: Flywheel/Encoder patterns See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Chris Morriss Date: Sun, 8 Dec 1996 18:15:30 +0000 Subject: Re: Flywheel/Encoder patterns In message <9612070732.aa08727@xxx.za>, Kalle Pihlajasaari writes [Deleted] > > >I was thinking for 'no-brainer' retro applications one could just add >a viscous brake to te shaft so after the first 20 degrees the units would >then be at the extreme limit of the backlash. > >Problem is extra wear on components from the drag and getting something >that will work at all engine speeds, perhaps something electromagnetic >like a Tacho generator (plug it into your Tacho display also) > >You would have to go with multiple coils to keep things simple but >might be able to keep the old dizzy in the boot (trunk). Getting >this to work with the fuel system would take some doing but if >you make your own into the existing harness you could swap the old >unit back again using the old 35 tooth sensor if you get stuck in >vancouver or something. > >Cheers *<<<-| A neat and very reliable solution to taking up the backlash is to mount an eddy current brake on the shaft. Much easier than providing viscous drag. All you need is a plain aluminium or copper disk rotating in the gap of a horse-shoe magnet. Like a old electricity meter. (If you had the rotating disk meters in the US) The principle was also used as the speed control a#on the old but revered Garrard 401 record turntable. Bye, - -- Chris Morriss ------------------------------ From: Chris Morriss Date: Sun, 8 Dec 1996 18:03:08 +0000 Subject: Re: Flywheel encoder patterns In message <19961207053527.AAA4538@LOCALNAME>, Roger Feingold writes >Been following your discussions and I was wondering if you have a sensor for >your application. If you have an engine operating at redline, the crankshaft >pulse rate might be beyond the response of the sensor, especially if you >have 180 or 360 pulses per revolution. > If it's a variable reluctance sensor then you might be correct, but I think you'll find that a Hall effect sensor will have plenty of bandwidth. Bye, - -- Chris Morriss ------------------------------ From: Todd Knighton Date: Sun, 08 Dec 1996 15:33:22 -0800 Subject: Re: Flywheel/Encoder patterns Chris Morriss wrote: > > A neat and very reliable solution to taking up the backlash is to mount > an eddy current brake on the shaft. Much easier than providing viscous > drag. All you need is a plain aluminium or copper disk rotating in the > gap of a horse-shoe magnet. Like a old electricity meter. (If you had > the rotating disk meters in the US) The principle was also used as the > speed control a#on the old but revered Garrard 401 record turntable. Pardon my ignorance, but what effect does a magnet have on a non metallic element like aluminum or copper. How's it work? And what kind of drag can you expect from such a device? Todd Knighton Protomotive Engineering ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 9 Dec 1996 11:25:28 est Subject: Forwarded: Re: Flywheel encoder patterns one of the problems you will run into with a hall-effect sensor is the tooth width. Most sensor will switch low several mm before the centre of the sensor and the tooth edge coincide, and switch high again several mm afterwards. This will limit your tooth width and hence your resolution for a given diameter. We find that at about 220 mm dia (flywheel size), the best H-E sensor we can get will allow us 60 teeth without resorting to teeth that look like feeler gauges. Andrew Rabbitt From: crsm@xxx.uk:smtp Date: ## 12/08/96 18:03 ## In message <19961207053527.AAA4538@LOCALNAME>, Roger Feingold writes >Been following your discussions and I was wondering if you have a sensor for >your application. If you have an engine operating at redline, the crankshaft >pulse rate might be beyond the response of the sensor, especially if you >have 180 or 360 pulses per revolution. > If it's a variable reluctance sensor then you might be correct, but I think you'll find that a Hall effect sensor will have plenty of bandwidth. Bye, - -- Chris Morriss ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 9 Dec 1996 11:48:14 est Subject: re: Flywheel/Encoder patterns >> overflowing the counters all the time waiting for the next tooth. > >All my counters are sixteen bit. But remember, the counters used for >driving the injectors and coils are not processor clock driven. They >are driven by the crank pulse, so their count would never exceed 719. I think someone may have covered this before, so bear with me; In an ideal world your fuel injector pulse width is nominally constant for a given torque at any speed. However if you're using your crank encoder to drive your counters, then your pulse width (in counts) will increase with engine speed. Your fuelling resolution at low speed will be poor. EG: at 600 rpm idle, you'd be looking at 'round 5-6 mg per cylinder per cycle. You'll have a pulse width resolution of 500 us, where your idle pulse width would be about 2ms, therefore your resolution will be about 1 part in 4. If you use a 1 MHz clock for your counter, you'd have a 1 part in 2000 resolution. Much better! How about instead, using a programmeable down counter which you load with your injector pulse width counter and trigger both the counter and the injector turn-on with your encoder/angle count. Then the counter just counts to zero and turns your injector off. Don't forget you'll might need some voltage compensation for your injector turn-on and off delays. This will make resolution issues even more important to you. Andrew Rabbitt PS: these numbers came from data just lying around. Don't take them ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 9 Dec 1996 11:54:00 est Subject: Forwarded: Engine braking???? this sounds very dubious to me! For a start, you'd want to advance your timing to involve the compression stroke, and what then about knock control? On the other hand, if you're off the loud pedal, you're more likely to be in over-run fuelling cut mode, therefore spark is not likely to do much for you. From: (talltom) talltom@xxx.com:smtp Date: ## 12/06/96 22:00 ## A friend of mine has a 96 chev 3/4t 4x4(with a 350) and just got back from a hunting trip. This guy was a GM line mechanic for 20 years and has owned his own shop for over 15 years, and he insists that his new truck does something so that once the brake is tapped going downhill it will not under any condition gain speed. Neither he or the other mech can figuire out why, but both swear to it. My question is is it possible that the guys at ac-delco have rigged things to retard timing to the point that the compression stroke would be infringed up on as necessary for deceleration??? Makes me wonder if some wise ass has done a little abs system interfacing here???? I realize that some of the company guys have non-disclosure agreements to deal with, but I'd appreciate as much insight into this as is pheasible! ------------------------------ From: Kalle Pihlajasaari Date: Mon, 9 Dec 1996 08:53:28 +0200 (sat) Subject: Re: Flywheel/Encoder patterns Hi Todd, > > A neat and very reliable solution to taking up the backlash is to mount > > an eddy current brake on the shaft. Much easier than providing viscous > > drag. All you need is a plain aluminium or copper disk rotating in the > > gap of a horse-shoe magnet. Like a old electricity meter. (If you had > > the rotating disk meters in the US) The principle was also used as the > > speed control a#on the old but revered Garrard 401 record turntable. > > Pardon my ignorance, but what effect does a magnet have on a non > metallic element like aluminum or copper. > How's it work? > And what kind of drag can you expect from such a device? Basically it is a generator with just one turn of copper in the magnetic field and this is shrotcircuited. This generates drag simply because the energy gets dissapated as heat and it has to come from somewhere. Eddy current merely describes the fact that the single turn of copper is actually just within the bulk material and not specifically defined. The Thelma prop-shaft retarder that was mooted as an electrical dyno break on this list a while ago works on the same principle so it is scalable to large sizes. The effect is proportional to the velocity of the disk which is why it can be used to speed regulation as in the turn-table. In the backlash take up it seems ideal but I have some reservations of it working suitably over a wide enough RPM range. If you set it for drag at low RPM it may cause to much at high RPM and cause wear or lots of disk heating. It has a marvelous damping effect on vibration as they have high speeds and are braked the the most. Cheers *<<<-| - -- Kalle Pihlajasaari kalle@xxx.za/ip Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 http://www.ip.co.za/people/kalle ------------------------------ End of DIY_EFI Digest V1 #376 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".