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Spectrum DX3S RPM setup on a 23cc?

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Old 01-11-2009, 06:09 PM
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Bat Fastard
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Default Spectrum DX3S RPM setup on a 23cc?

Has anyone used the RPM function on the DX3S with a fuelie 23cc engine? If so, where did you mount the RPM sensor?

Jamie
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Old 01-11-2009, 09:09 PM
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SAVAGEJIM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

If I remember correctly, the speed sensor needs to be mounted such that is clocks your flywheel, so the senser magnet needs to be mounted to the flywheel, and the sensor part needs to be mounted somehow to the shroud of the flywheel such that it points to the magnet.

Here is a problem I foresee: The Spektrum sensor senses a magnetic field as the magnet passes under it. Our gasser engines have a magnet built in for the mageneto to fire the spark plug.

So, try this expririment: Dont put the little Spektrum magnet on the flywheel. Instead, mount the RPM senser in the shroud, turn the flywheel, and see of the sensor will read the magnet that is already on the flywheel. If so, use that, and as your gasser runs, the Spektrum should be able to count the RPMs just like it would if the tiny magnet were on there instead.
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Old 01-11-2009, 09:13 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

Wait a minute! Is your Spektrim kit the full telemetry kit? IF so, the Telemtry kit DOES NOT work on magnets!!!! I am initially wrong in my first post so ignore all that unless you bought the RPM kit that uses magnets.

If you have teh fulle telemetry kit, no magnets at all, the RPM sensor reads a reflective pieces of tape, so you have to put that little piece of tape on the flywheel such that it will cross under the RPM sensor.

In either case, you will have to do some creative fabricating to mount the Spektrum sensor part in the flywheel shroud so that it can ither read the magnet or the reflective sticker.

http://www.spektrumrc.com/ProdInfo/F...try_manual.pdf
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Old 01-11-2009, 10:05 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

I am not sure how it works. I bought the DX3S with the data telemetry built in. Just as a test before I made a sensor mount, I placed the sensor close to the flywheel and rocked the flywheel back and forth. It read RPM. I know that the radio includes the little stickers, but it will read RPM from the magnets (there are two on the flywheel). Also with there being two magnets I think it will read twice the RPM that the engine is actually turning. Any Ideas?

Jamie
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Old 01-11-2009, 10:11 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

Unfortunately not. The only way that you can overcome this is to mentally divide the RPM reading in half. So, if you see 35000 RPM, then your true RPM is 17500 RPM.
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Old 01-12-2009, 12:31 AM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

O.K. the solution is to remove the engine and mount the sensor on the inside of the flywheel. I.E. the side that faces the engine, close to the shaft. there is enough room to put the sensor so that there is a solid line of sight on the crank and only the break of the tape.

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Old 12-01-2009, 04:45 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

i just did it ! What you have to do is to zip tieyour sensor harness to the sparkplug cable, on the top of the engine and let your sensor in air. The mgnetic pulse that gave the coil will be detect and you will have the correct RPM. It's seem weird but working. In a idle position i get around 4500 rpm.

I will post picture tonight

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Old 12-01-2009, 09:32 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

A pic of your setup would be cool. My sensor mounting didn't work out so well, it takes only a few minutes for the sensor tape to get dust or dirt on it and the readings are useless. I need some motivation to get mine out and run it some more. Its a year old and has had maybe 2 tanks of fuel run thru it.

BF
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Old 12-01-2009, 10:18 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

I know it's weird but working. Here my pics. The only thinh to do it's to ziptie your sensor to the cable that go to the sparkplug and connect it to the receiver telemetry. The only thing i wish to test is if i just ziptie a servo extension to the sparkplug wire, it will work or not ??? Can you try it before to ziptie the rpm sensor ?

Thanks
Dan
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Old 12-07-2009, 11:54 AM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

Tubeman and BF;
    Thank you for your posts on this- I expect they will be very helpful once I am able to bind my Spektrum SR3300T receiver with my DX3S radio.  This brings me to my reason for posting:  Did you experience any issues in binding your receiver to the radio?  I was able to bind the SR300 with no problem but could not bind the SR3300T using the same setup.  The yellow LED on the SR3300T kept flashing indefinitely, never went to the solid on state indicating a successful bind operation.
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Old 12-08-2009, 12:42 AM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

What settings are you guys using to figure out the mph ?
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Old 12-21-2009, 10:02 PM
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Default RE: Spectrum DX3S RPM setup on a 23cc?

My sensor is "working" in the sense that it gives a reading. But it appears to be showing about double the actual rpm. I have mine zip ties about 3/4" away from the spark plug. Is my sensor bad or is there something else I could be doing wrong?

Also, I covered the sensor in RTV sealant for "waterproofing purposes" Not sure if it was required, but I'm hoping the RTV sealant is somehow causing an issue.
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