Re: Audio Tachometer for 2 stroke engine

On Sat, 23 Apr 2005 15:13:39 +0000, Mook Johnson top-posted:

> I think you have real boats confused with R/C boats. These boats are
> radio controlled and 3' to 4' long. Key to these is speed with some over
> 100MPH actual speed not scale. Racers play with props, strut angle and
> depth, boat ride attributes, engine modifications, exhaust tuning,
> nitromethant % of fuel mix, and on and on and on to get the speed. All
> kinds of dials for them to play with in the search for the ultimate setup.
>
> A boater will typically flip his boat 5- 10 times during a practice
> session. There is a jon boat on site to go pick it up, clear the water and
> out she goes again. The problem with the curent technology for RPM
> measurement is that if the boat hits the water upsidedown at 60+mph it
> commonly rips that unit and its associated wires off and sinks to the
> bottom. So for that reason, boaters will be a litter conservative on how
> they run the boats so the don't flip it.. Kind of defeats the purpose.

So get a plastic bag, put your precious instrumentation package in it,
dump in some styrofoam peanuts, and shrink-wrap it, as was suggested about
a week ago.

Or, use expanding urethane wall foam.

Cheers!
Rich


>
>
>
>
>
>
> "Rich Grise" <richgrise@xxxxxxxxxxx> wrote in message
> news:pan.2005.04.23.15.04.10.839402@xxxxxxxxxxxxxx
>> On Sat, 23 Apr 2005 11:28:04 +0000, Mook Johnson top-posted:
>>
>>> AM radio is a very interesting option for one type of this application.
>>>
>>> The other type is a glow plug engine that doesn't have an EM signiture
>>> once it is running.
>>>
>>> The actual use for this device would be to monitor the 2 stroke engine
>>> on high performance R/C boats. The plan is to have the unit velcroed
>>> to the boat and it just listens to his engines whine and logs the RPM.
>>> Thats why
>>> it needs to float since the 38" boat may be running at 80+ MPH and
>>> often flip over and fly off the water spectacturlary. If the unit was
>>> seperated
>>> from the boat I want it to float so it can be retrieved.
>>>
>>> The attempt is to make the unit easily transportable fom boat to boat
>>> if there are several boats to performance monitor and tune all that
>>> needs to be done is to remove the unit forn the velcro and stick it on
>>> the other boat. No external wires or plumbing.
>>>
>>>
>> If this description of your scenario is really accurate, then the actual
>> RPM value really doesn't make any difference. No one who gets off on
>> spectacular crashes is going to be concerned with _actual_ values - just
>> make something up. What you _really_ need is a secret magic box that
>> does nothing, (except survive the crash, of course) and a display on
>> your box that shows impressive numbers. "Yeah, I was cranking out
>> THIRTEEN GRAND when it crashed. Gonna hafta work on that next year!" and
>> show them the display on your control box that's showing, oh, I don't
>> know - 13052? 17449.5?
>>
>> Who really cares?
>>
>> Break a Leg!
>> Rich
>>
>>
>>
>>
>>>
>>>
>>>
>>>
>>> "dalai lamah" <antonio12358@xxxxxxxxxxx> wrote in message
>>> news:do57h44lmzw$.1n7so9qprvvx2$.dlg@xxxxxxxxxxxxx
>>>> Un bel giorno Mook Johnson digitò:
>>>>
>>>>> I have a crazy idea to use a microphone near the exhaust of a 2
>>>>> stroke engine to measure the instantaneous RPM of the engine.
>>>>
>>>> Just out of curiosity: if you can put a microphone near the exhaust
>>>> (and therefore you need to mount the sensor somewhere on the vehicle),
>>>> why can't
>>>> you put a knock sensor on the cylinder or a capacitive pickup on the
>>>> spark plug cable?
>>>>
>>>> Anyway, I think you could have better chances by receiving the EM
>>>> spikes generated by the sparks. If you put an AM radio near the
>>>> engine, you will hear a very clear RPM signal, and I guess it's even
>>>> better with a 2-stroke,
>>>> one-cylinder engine.
>>>>
>>>> --
>>>> asd
>>
>>
>>


.

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