Rpm sensor on nitro engines.

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Greg Ruggles

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Nov 20, 2024
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I just picked up my Futaba 10 px and I'm going to be setting up some telemetry. Just curious, how many people use the rpm magnetic sensor? Where and how do you attach the magnet without it flinging off.
Thanks in advance for your comments.
Greg
 
I bore the hole on the mill with about a 1/2 thou press fit, warm the flywheel up with a torch and it goes right in, haven't had one come out yet.

Alternatively you might be able to use an undersize reamer to get the job done.



View attachment 334827
Thanks for the reply. I'll see if the boss at work will let me do this on the cnc.
 
I just picked up my Futaba 10 px and I'm going to be setting up some telemetry. Just curious, how many people use the rpm magnetic sensor? Where and how do you attach the magnet without it flinging off.
Thanks in advance for your comments.
Greg
You can use a small collar on the drive shaft cable too. just press or epoxy the magnet into a hole on the collar, mount the sensor so it pick up the rpm.
 
None of the magnets were marked N and S like the bar magnets in school. So we would take 2 magnets and the 2 surfaces that were attracted to each other were N and S. Then to identify the N side we would do a test pass by the sensor holding the magnet by hand to see if it triggered. If it did then you knew it was N. I usually marked the surfaces red and black with a Sharpie at the time of checking which were attracted, not knowing what as N or S.
 
Wish Eagle Tree still offered their system and data logger.

View attachment 334906

This is way better:

https://www.sm-modellbau.de/UniLog-2-und-Zubehoer

225496-Unilog.jpg
 
I bore the hole on the mill with about a 1/2 thou press fit, warm the flywheel up with a torch and it goes right in, haven't had one come out yet.

Alternatively you might be able to use an undersize reamer to get the job done.



View attachment 334827
Terry, do you have a picture of how you mounted the sensor? I was thinking about getting a 1/2 wide flat aluminum and bending it in a 90. Slot Two holes and attach it to the motor mounts. This was I'll have adjustment parallel to the engine and then slot two holes for the sensor. That way I'll have adjustment perpendicular to the engine to get my 1~2mm distance. What do you think???
Greg
 
Terry, do you have a picture of how you mounted the sensor? I was thinking about getting a 1/2 wide flat aluminum and bending it in a 90. Slot Two holes and attach it to the motor mounts. This was I'll have adjustment parallel to the engine and then slot two holes for the sensor. That way I'll have adjustment perpendicular to the engine to get my 1~2mm distance. What do you think???
Greg

Not a great pic but I milled a slot in an aluminum mount so the hall sensor presses into it then the mount is screwed with a standoff to the side of the hull.

Not sure what the Futaba sensor looks like but sounds like you have a plan.


SAW datalogger (2).jpg
 
Thanks for the picture and your help. My sensors arrive tomorrow, Saturday, so I'll start working on the project. The boss gave the approval to mill the pocket on the flywheel. So I got that going for me...
 
Thanks for the picture and your help. My sensors arrive tomorrow, Saturday, so I'll start working on the project. The boss gave the approval to mill the pocket on the flywheel. So I got that going for me...

After I bore the hole in the mill I leave the flywheel in the vise and stick a 1/2" gage pin in the spindle with the magnet stuck to it to help align it for pressing it in.

Do you have a set of gage pins or some other way to measure the hole?

RPM sensor.jpg
 
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