Motorcycle ignition question

Discussion in 'The Projects Forum' started by Classictrial, Aug 23, 2010.

  1. Classictrial

    Thread Starter Member

    Aug 23, 2010
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    I have built a competition motorcycle which has a CDI type ignition system, with a hall effect trigger. In order to be able to use 2 entirely different advance curves I have fitted a second hall trigger driven from the cam, using a mechanical advance retard mechanism, which can be easily altered.

    Have very little knowledge about this type of thing, and wondered if it would be feasible to switch between the 2 triggers when the bike was running, and if so what would be the best way to go about this (there are 2 wires running to each trigger).

    Be very helpful if anyone could advise me on this, as while I can easily repair a magnesium casting, or rebuild an engine, I am pretty much in the dark when it comes to electrical matters.
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    You'd probably want to use a frequency to voltage converter IC so you'd have a control signal based on RPM, then you'd just use that to operate some sort of switching circuit to change over to the advanced sensor when it reached a higher RPM point of your selection.

    I've got to get to the office so I'll leave the simple design to someone else.
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I don't see any reason you couldn't switch between the triggers while it is running. You might get a single miss. However, why go that route?

    Why not use the single trigger control that exists and choose the advance curve you want with a/the microcontroller. (I am assuming at least one of your systems has or will have the advance curve determined by a microcontroller.)

    Model airplane and boat hobbyists have been using microcontrollers to control the advance curve for their engines for several years. There are even DIY sites and partial kits available.

    John
     
  4. Classictrial

    Thread Starter Member

    Aug 23, 2010
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    Thanks for your replies, it seems very difficult to find accurate info on this sort of thing, and I was very glad to find this forum.

    Not sure if it would be possible to use any sort of electronic advance controller, as this bike has no 12v dc supply, and ignition works with a source coil supplying the CDI unit, which is triggered by a hall sensor?

    All I really need to know at the moment is how to go about making some sort of waterproof switch, which can be used to select either one of the hall triggers I have fitted.

    However if it were possible to use a micro-controller of some sort, then that would be ideal, but I have been led to believe this would not be possible on this particular bike (Honda trials).
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Most of us still use 2 cycle glow plug engines. Check out http://www.towerhobbies.com

    I also doubt much electronics will be involved in his device, if there were he wouldn't have two sensors.

    Ah, I see you're back. No battery means forget anything automatic.

    Waterproof switches are easily findable, try http://www.mouser.com

    When electronics are built many of the components are designed as sealed so they can go through a water wash to remove the solder flux from the PC boards but you'll want something more substantial for the type of riding you'll be doing. You'll find a decently built waterproof toggle switch on that website.

    [EDIT:] Shoot, I don't even have hall effect sensors on my Honda CDI, there's a set of trigger coils separate from the magneto/stator that generates the HV as well as charges the battery to run the lights and the necessary electric start. Have to have electric start on this model, they weren't designed with kick starters. (and you best hope your battery doesn't run down, almost impossible to push start)
     
    Last edited: Aug 23, 2010
  6. jpanhalt

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    Jan 18, 2008
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    Aware of Tower Hobbies. Buy very little from it. As for 2-cycle nitro engines being used "most" for model airplanes I would like to see your data. Sales can be deceiving. Based on a sampling of four clubs in Cleveland for everyday flying, gas 2-cycle with ignition and nitro 4-cycle are most common, electrics are next, and nitro 2-cycle are least common. Several guys fly turbine, but my local club has only one regular flyer who does that. We do occasionally have a special event (like speed 40 pylon) for which the engine is required to be nitro 2-cycle. Also, many beginners seem to start with 2-cycle, perhaps due to the Tower influence, but that doesn't necessarily translate into continued use.

    Nevertheless, for the larger models with 2 cycle gas, the ignitions often have an electronic advance; although, it is arguably not necessary except for the very largest of the engines. Here are some links to forum threads on model ignitions. Note, TCI is also discussed:

    http://www.rcuniverse.com/forum/m_3422690/mpage_12/key_/tm.htm
    http://www.rcuniverse.com/forum/m_4344316/mpage_55/key_/tm.htm
    http://www.rcuniverse.com/forum/m_9842658/anchors_9842658/mpage_1/key_/anchor/tm.htm#9842658

    And some engine/ignition manufacturers:

    http://www.3w-modellmotoren.com/english/3W_Modellmotoren.htm
    http://www.desertaircraft.com/index.php
    http://www.rccdi.com/
    http://www.prcmodel.com/modeng/name/onlinestore/category/7

    The OP came to an electronics forum, so I assumed it was an electronics question. I questioned the need for two sensors, but was not aware the bikes had no electrical systems. If that is the case, what provides power to the Hall sensors? I don't understand why one would use a dynamo to generate voltage for CDI and not be able to control the spark timing with an MCU. Worst case, a small battery could control the timing function for 100's of hours of continuous running. Moreover, an MCU would allow easier adjustment of timing curves than a mechanical linkage would allow (see some of the experiments in the model links on odd timing curves). The OP later clarified that he only wanted a recommendation for a sealed switch.

    Some model ignitions (like older 3W's) also use trigger coils instead of Hall sensors. The Hall pickups are a little smaller.

    John
     
  7. marshallf3

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    Jul 26, 2010
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    There must be a tiny winding in the magneto that powers the hall sensors, I'd have to see the wiring diagram of the bike to know much more. Then again I don't recall ever seeing them being used in a bike that small, it's usually a straightforward CDI triggered with a coil.

    Wish I could afford 4 stroke engines, in my days of RC they were far and inbetween, cost a ton and had fairly low power output to weight.

    I'm trying to get back in but time is a huge enemy. I've got a slightly off-scale (almost perfectly 1/4 scale) set of plans and full kit of laser cut parts to build a Douglas A-26 Invader, was planning to power it with OS Max 0.46 engines. The nacelles are large enough to house the engines, mufflers and still allow plenty of air flow through them to keep the setups cool. Perhaps a rather boring plane, probably handle like a boat but it would be different.

    Some of you guys are really serious about this stuff - a lot more than I would have thought if you're messing about with engine timing - to me it's just a very "remote" hobby. What makes me sick is to see these people that buy or build the helicopters, for some odd reason they seem to be very tendent to crashing.
     
  8. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    It's just age, nothing more complicated than that. I have flown RC airplanes since the 1952/53 school year. I got my 8-year-old grandson a Blade helicopter for Christmas last year. He had no prior real experience. Guess who flew it better by the end of the night. I assume he must have had some simulator experience, but I didn't really want to ask. :D

    John
     
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Must come from all those video games they play.

    The larger ones are far from inexpensive yet I see these guys straining to keep the things level. They usually make it to about 10' up, start coming down again and then lose it.

    After all these years they've finally started talking about adding a paved runway area to our field, that would allow me the luxury of more tire choices if I can ever get the time to build this project. Luckily the wings detach as separate sides or I'd have trouble even getting it out there, span is about 8' so I guess it's more like 1/8 scale since the actual plane spanned 70'.

    [EDIT:] We actually have one here at Wiley Post airport that's airworthy.
     
    Last edited: Aug 24, 2010
  10. jpanhalt

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    The A26 is a beautiful airplane. There are several avid modelers who are active on this site. "Bernard" (http://forum.allaboutcircuits.com/album.php?albumid=29) makes his airplanes from used beer cans. He may also use N.A. beverage cans to supplement his supply. ;)

    John
     
  11. marshallf3

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    Jul 26, 2010
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    I think it's the huge engine nacelles that first drew me to it. I wanted to build something, preferrably twin, where the engines don't hang out in clear view and I'm a bit leery of using those fan jet setups. You do have a few years on me (at least in the flying part) but I came from the Cox 0.049 era and had a few that had the 0.020. Never owned a 0.010 but I heard they resumed production on them again for a short while. Shoot, you've got to be flea weight to use an 0.020, can't imagine what an 0.010 would require and it would almost certainly have to be free flight.
     
  12. Classictrial

    Thread Starter Member

    Aug 23, 2010
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    Maybe "hall sensor" is the wrong term? Honda manual calls these pulse generators, which on the stock bike are triggered by a magnetic slug fixed to the outside of the flywheel generator.

    On this bike the compression has been raised significantly, and the stock advance curve means very flat power output, and noticeable reduction in top end power.

    For this reason a camshaft mounted pulse generator was fitted, which has a machanical advancer, that can be easily altered to best suit the motor.

    The TLR has a 12v AC generator, with a CDI unit supplied by a specific source coil in the generator, which is triggered by the pulse generator I described earlier.

    If anyone could come up with a relatively simple way to alter the ignition curve on these bikes, then its something that I would imagine would be quite popular, as fitting the pulse generator from an earlier bike is pretty involved, and very costly if new parts are used.
     
  13. marshallf3

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    Jul 26, 2010
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    Sadly, while it's easy to retard a timing pulse electronically, advancing one is not easily done.
     
  14. jpanhalt

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    Not sure I understand why advance is difficult. The model ignitions referenced before can be advanced. John
     
  15. Classictrial

    Thread Starter Member

    Aug 23, 2010
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    Without 12v dc supply to power the required electronic circuits, apparently it is impossible to advance ignition timing. I guess models may well have dc supply so there probably isnt a problem here?
     
  16. jpanhalt

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    I am becoming terribly confused. My comment regarding electronically advancing the spark was in reference to marshallf3's comment that one can retard electronically but not advance.

    Anything electronic, whether it is to retard or advance the spark, is going to require a DC source. However, since one is only controlling the timing -- not generating the power for the spark -- a small, accessory battery will run the timer for a long time.

    Do you have a factory schematic for your bike's ignition system?

    John
     
  17. marshallf3

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    Jul 26, 2010
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    He's dealing with nothing more than a magneto ignition system connected to a CDI. There is no battery on the bike, nor a charging circuit winding in the magneto.

    Typically the only way to change the timing is to move the location of the CDI triggering pickup coil. If you do supply a simple power source and not move the pickup sensor it would have to pick up the signal pulse then wait 360 degrees minus the amount of advance desired before triggering the CDI.

    Dirt bikes do vary though, some actually do have a power source winding to power a headlight but most operate much in the same way a lawnmower or washing machine engine has been built since the early ages.

    The constantly wearing and in need of adjustment/replacement points & condensor system were later replaced when the technology became available to make a simple CDI and many are still built with this exact method.
     
  18. Classictrial

    Thread Starter Member

    Aug 23, 2010
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    Very interesting Marshall..........and quite right about the lay out of the ignition, other than the fact that on this model bike it does have lighting coils and a charging circuit, so I guess it would be possible to self power a small ignition controller, triggered from the stock pulse generator?
     
  19. marshallf3

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    Jul 26, 2010
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    Yes, knowing that it can be done although not the easiest thing in the world to design - at least not for me. They make a ton of controllers for cars that are fully adjustable, you'd think there would be the same for motorcycles out there somewhere as well.
     
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