Measuring RPM of diesel engine

terrifictimbersllc · May 23, 2013, 06:30:13 AM

I really just want to check the idle and full speed RPM of the Kubota diesel on my sawmill (42HP, 4 cylinder). But it would be nice to see the RPM while sawing. Thinking of adding a tachometer (link below), which reads the engine frequency via a transducer clamped around the fuel line. But before I spend about $100 I'm wondering if there are other options. I have a front remote so I'd have to get the signal up the cat track if I want it mounted on the remote instead of the engine. Too bad engine RPM isn't one of the diagnostic options in Accuset 2!

http://tinytach.com/diesel.php

bandmiller2 · May 23, 2013, 07:04:09 AM

TT,thats probably as good as it gets for a constant reading tach.Spotcheck you could use the stewart Warner handheld.Some of the older diesels used a mechanical tach driven like the old spedometers with a flex cable. Frank C.

Nomad · May 23, 2013, 07:54:01 AM

Is there an unused (spare) wire in the track you could pirate to transfer the signal? Then you could splice into it from both ends.

Magicman · May 23, 2013, 08:01:11 AM

I have used tinytach on gasoline engines with good results. Sadly, I can't use that one on my Lombardini because the injector lines are internal.

SPD748 · May 23, 2013, 09:25:37 AM

Autometer (model #2888) makes a diesel tach that picks up from an alternator. I've used this model several times with great success. One drawback is having to calibrate the unit by adjusting the displayed rpm to the actual engine rpm. I used a hand held strobe pickup for this task. I prefer the 'look' of the standard round dial/needle over the lcd display.

Another option is the 'Dakota Digital Universal Flywheel Tachometer Interface' which picks up pulses from the flywheel ring gear and converts those into a usable signal for any electronic tach. With that, one could go with Autometer's 4000 rpm tach (model #2890) for a nice setup, although it would cost around $220 :-\

-lee

pineywoods · May 26, 2013, 03:20:53 PM

Why bother with engine rpm? Bandwheel rpm is what's really important and that's dirt cheap. Bicycle speedometer from walmart, $10 bucks or so.

terrifictimbersllc · May 26, 2013, 03:39:46 PM

Interesting idea, but for idle and full speed engine rpm checking and adjustment.

barbender · May 27, 2013, 01:13:49 AM

Quote from: pineywoods on May 26, 2013, 03:20:53 PM
Why bother with engine rpm? Bandwheel rpm is what's really important and that's dirt cheap. Bicycle speedometer from walmart, $10 bucks or so.

Piney, how did you rig that up? Something like that would very handy for keeping an eye on slipping drive belts, how much lost band speed causes a wave, all sorts of stuff.

pineywoods · May 27, 2013, 11:25:10 PM

Quote from: barbender on May 27, 2013, 01:13:49 AM
Quote from: pineywoods on May 26, 2013, 03:20:53 PM
Why bother with engine rpm? Bandwheel rpm is what's really important and that's dirt cheap. Bicycle speedometer from walmart, $10 bucks or so.
Piney, how did you rig that up? Something like that would very handy for keeping an eye on slipping drive belts, how much lost band speed causes a wave, all sorts of stuff.

Bike spedo consists of 3 parts
1. small magnet fastened to bandwheel. glue, tywrap, duct tape etc.
2. pickup coil mounted somewhere where magnet passes with 1/4 inch.
3. display unit with cable connecting to item 2

The whole works runs on a single 1.5 volt button battery, turns itself on when bandwheel starts rotating. Setu[ program selects mph/kph, speed/distance, and wheel size. A 20 inch bike wheel is quite close to a 19 inch bandwheel. In speed mode, a slipping drive belt is quite noticeable, as is a blade that's starting to get dull. Distance mode will show how much blade has been through the wood, resetable for each log or blade. Some interesting data can be derived from that...

I've had 2 problems with mine.
1 The button battery doesn't last very long
2 a broken blade can take out the magnet and pickup coil. Recommend mounting these on the idler side..

barbender · May 28, 2013, 12:55:46 AM

I'm going to have to try that, Piney. I think I meed to come hang out with you for about a week so I can steal all of your good ideas ;D

PC-Urban-Sawyer · May 28, 2013, 02:16:42 AM

Quote from: barbender on May 28, 2013, 12:55:46 AM
I'm going to have to try that, Piney. I think I meed to come hang out with you for about a week so I can steal all of your good ideas ;D

From what I've seen, you'd need a month of Sunday's to even come close to getting them all.

Herb

barbender · May 28, 2013, 07:01:09 AM

I think you're right, Herb ;)

Magicman · May 28, 2013, 08:22:51 AM

That plus you can not steal what he freely gives away.

tyb525 · May 28, 2013, 09:13:04 AM

I've done the bicycle speedometer thing too - it works!

barbender · May 28, 2013, 11:28:09 AM

I know, Piney is free with his knowledge ;) I always enjoy looking over whatever project he may be sharing on the forum, I always learn something.

barbender · May 28, 2013, 11:30:20 AM

I also enjoy the Magicman's wisdom on the ins and outs of full time portable sawing ;)

terrifictimbersllc · June 04, 2013, 02:19:10 PM

Quote from: nomad on May 23, 2013, 07:54:01 AM
Is there an unused (spare) wire in the track you could pirate to transfer the signal? Then you could splice into it from both ends.

Yes there is, just found it. Unused red wire in front remote control box comes out with a tab connector on it inside the head, hanging above the up down motor. It goes through the 16 pin connector P(1)-13 and is labeled W25. The diagram says W-25 is for an accessory probably a laser. I can use it instead for the transducer and put the tiny tach on the front remote control box. There are still some other unused accessory lines too, through the cat track.

Now I have to figure out where I can mount the transducer. There is no metal fuel inlet line, where it is supposed to go. Just metal outlet lines for each injector (see picture). Maybe a line with a closed end could be mounted to the fitting where the rubber fuel inlet line goes in? I have an email in to them. I like Pineywood's idea of monitoring bandwheel speed as well for belt slippage.

Nomad · June 04, 2013, 04:56:51 PM

It would really be nice to watch both the RPMs and band speed, wouldn't it?

UN Hooker · June 04, 2013, 10:40:29 PM

A transducer would go on one of those four vertical metal lines (injection lines) in the picture.
Be sure the line is clean where you clamp it on - sand off any paint etc.
UN

terrifictimbersllc · June 05, 2013, 08:52:45 AM

Quote from: UN Hooker on June 04, 2013, 10:40:29 PM
A transducer would go on one of those four vertical metal lines (injection lines) in the picture.
Be sure the line is clean where you clamp it on - sand off any paint etc.
UN

Thanks! Shows what I know. Out to measure the line now.
p.s. A light sanding and the diameter is 0.236", or exactly 6 mm, what I expected because everything else is metric on this Kubota. Good to go, that's one of Tiny Tach's standard transducer sizes.

p.s.s. Tiny Tach is ordered. I'll post the modification in the Useful Sawmill Mods thread with a link to that here. Thanks again everyone.