RPM

[rickw]

Whats the easiest way to measure RPM

[dieselguy86]

Buy a Garrett turbo speed gauge

[rickw]

THX.

Any other options that cost less than $500.00 plus USD?

[dieselguy86]

There's quite a few different ways, but you asked for the easiest. It doesn't get much easier or reliable than the garrett gauge.

Laser tach works but is very sensitive to just the right conditions.

The rc turbines use a magnet in the compressor nut, this works great but you'd need to be good at electronics to build a stand alone system. Or buy the xicoy ecu kit for ~$300, but I think you need all the sensors hooked up and an rc signal for it to work. A bunch of extra for one thing, but its an option.

There's an optical option, where a transmitting and receiving leds are mounted straight across from each other. In the middle is a compressor nut with a hole filled thru it. The hole is inline with the 2 leds, when it lines up, the leds cab see each other and registers a signal.

The other optical option is like the laser tach, where the compressor but is painted half white/ black. The white reflects the signal to the receiving led, and counts it as a signal.

[rickw]

Thanks
I'll check out the optical solution.

[racket]

I use a laser tach off ebay , like this one www.ebay.com.au/itm/384120560884?hash=item596f5e9cf4:g:2BUAAOSwFEFgiRob , comp snout/nut painted half gloss white , half matt black , with a crescent shaped piece of the reflective tape that comes with the tach fitted to the radial face of the comp outboard of the nut on the half white segment, this way you can get a good reflection if the tach is in an axial position to the shaft .

But if you need more than 99,999 RPM then you'll need to look at more complex/expensive units like the ones Joe mentioned

Cheers
John

[rickw]

Thanks I'll check that out.

[Sweetenough]

This is probably not by far the easiest way to check the rpm.....
I use a www.full-race.com/turbo-speed-sensor-kit
connected to a "small" ABB PLC so I can monitor and logg speed among other parameters.

But if you want to check the speed by hand when running, then the handheld laser tach is by far the cheapest/easiest way.

Kind Regards
Thomas

[rickw]

I just picked up a hand held unit. I am a bit concerned that the reflective tape being affixed to the compressor blade will not remain there when running but we'll see.

[misterg]

Funnily enough, I'm looking at this, having become very frustrated with my optical tacho (and nearly losing it into the engine! ).

I'm trying to make a magnetic sensor now. I think the key is an extremely sensitive Hall-effect switch: Honeywell SM451R. This switches on and off with alternate magnetic poles and is sensitive to 7 Gauss (a good inch away from a decent magnet).

It is trivially simple to connect this to an Arduino to measure / display RPM.

I've got as far as demonstrating that it will function with a magnet taped to the compressor nut (and spun by hand).

I intend to trigger it using a diametrically magnetised* ring magnet embedded in the compressor nut, but I couldn't find one the size I needed other than from China, so I'm currently waiting for the slow boat to dock before I can progress any further. I expect to have to experiment a bit to try and make sure I get reliable triggering.

Will keep you posted!  



(*one that has N & S poles on opposite edges, rather than the more common ones which have N & S poles on opposite faces)

[racket]

Hi

Some of the early experiments were conducted with a magnetised nut , not sure how they magnetised them but might be worth a try

Cheers
John

[rickw]

Well that worked just long enough for me to get a sense of max RPM by feel at least.

[stevie]

I selected this:
"For the tach I've ordered a E3X-NA11 and a diffuse fiber."

Alas it is completely burned up in the shop fire. Never tested it aside from power on.

I keep checking in here folks I am still digging through the ashes. Thanks for the inspiration.
Steve