Tach for Satoh S370 Beaver?

[caferacermike]

So I decided I am going to mount an analog water temp sender and display into my dash using the port for the electric sending unit and then got to thinking about a tachometer. When I first began running the tractor I ran the PTO in it's highest speed of 1,297 (I have the optional reverser with larger PTO shaft) while driving around in 3H. Man it would cut some grass. Then the over heating began and I read that a shredder should be ran around 500-540rpm and starting running the PTO in it's lowest speed. Fast forward. Now that it's not over heating (today at least) and while I'm shopping for pieces I say to myself "Self, you should get a tachometer because numbers fascinate you and you can bore/impress your interweb friends with number such as how many linear miles you shred in an acre with your 42" shredder. Wouldn't it be fun to figure out at what speeds the engine runs to do so?". So then I say to myself "Heck yeah that would be awesome".

Being a mechanically inclined fellow (albeit first diesel) and able engine rebuilder I start looking for 2 cylinder tachs, yeah F-you the kind that connect to the coil for an easy electric pick up. Whilst I was having some difficulty finding a nice analog needle display 2"-3" type electric pick up gauge, I found several go kart and small motorcycle racing digi tachs....................... And then.............................. I thinks to myself, "hey get on that interchat forum you like to go to and ask your silly questions and then ignore the wonderful advice like you do so often". As I log in, it hits me so hard..............................................and thankfully before you jesters got a chance to chastise me,............................................................"Hey diesels don't have a coil, they run on magic". Hahahaha lol, yeah so there.

And then, so yeah, any ideas on how to put a tach on this thing? The KE70 motor wasn't used on a lot of engines and I'm unsure if it ever had a spline gear to run a tachometer or if a kit was available. I could just scab one of those ultra old school cable driven bicycle speedometers to the front of the engine and have it lay on the fan belt instead of a bike tire, then I'd need to use a point and shoot hand held tach to read the engine speed and mark the glass on my bicycle speedo with a Sharpie marker. Ok probably not. Is there an option?

 

[Ilikeurtractor]

I think they manufactured an analog tach for the 2-cylinder diesels but I haven't seen many and would have not have an idea where to get one. It may even be possible the 3-cylinder diesel analog tachs would work but I haven't explored that past the idea stage. You have a couple of other options however:

1.) Get a "tiny tach" diesel unit - these will run $100 but are easy to install. They just clamp on one of the injector lines and use that for a signal. I went with this option.
2.) Use a magnetic pickup type. These are cheaper but harder to install to some extent. I haven't tried this type but I saw someone on the forums that did it and they claimed it worked great. I think you can find these on ebay or amazon, I haven't spent a lot of time looking for these though but they are out there.
3.) Tap into your alternator and try to get a frequency off of it and somehow convert it to an engine rpm. This is probably the most difficult since you need to account for the differences of speed between the alternator and engine and then get a frequency to display as an engine rpm (ideally). In theory this is quite possible but it depends on how much free time and ambition you have and how much you like to play with electronics and the electrical side of the tractor.
4.) You could measure the speeds at various fuel settings using one of those hand-held speed sensors (fairly cheap off amazon or harbor frieght) that use reflective tape and mark the results on the fuel lever. Pretty inaccurate and doesn't give you "real-time" readings, but it would be a low-budget solution if you already have a hand-held speed sensor.

 

[caferacermike]

1, use the injectors? They are mechanical injection so will the "tiny tach" produce a magnetic field that passes through the line and read the pulse from the injectors?

2, magnetic pick up type. That sounds like what I was thinking. But those generally connect to one side of a coil and read the electrical pulses.

Back to google. I'll check for Tiny Tach.

 

[caferacermike]

Google says"Autometer makes diesel tachs that pickup up a field from the alternator" Ordering soon....

It needs to be calibrated with a handheld strobe tach, thankfully I have one..

 

[caferacermike]

Great the video function doesn't work. Try again,

 

[Ilikeurtractor]

1, use the injectors? They are mechanical injection so will the "tiny tach" produce a magnetic field that passes through the line and read the pulse from the injectors?

2, magnetic pick up type. That sounds like what I was thinking. But those generally connect to one side of a coil and read the electrical pulses.

Back to google. I'll check for Tiny Tach.

The tiny tach system uses some sort of proprietary sensor. I wouldn't be surprised of it works on either a "hall effect" sensor or a "peziometric" one. The injector line actually expands slightly during injection and I would think a peziometric crystal could be used to generate a small voltage during this event and then be counted and averaged using some electronics.

 

[Ilikeurtractor]

Google says"Autometer makes diesel tachs that pickup up a field from the alternator" Ordering soon....

It needs to be calibrated with a handheld strobe tach, thankfully I have one..

Cool. I didn't know they had something like that on the market. I'd probably still go with the TinyTach as it's cheaper and seems simpler and more reliable. However, I will tell you that the TinyTach's electonics do not work well in below freezing weather (display shows "low voltage") which is annoying at times.

 

[skylarkguy]

That tiny tach is pretty slick. I just looked and the KE70 in my mt372 is cable driven. The cable exits the engine right below the oil filter on the right side of the motor. Just FYI.

 

[Ilikeurtractor]

The tiny tach system uses some sort of proprietary sensor. I wouldn't be surprised of it works on either a "hall effect" sensor or a "peziometric" one. The injector line actually expands slightly during injection and I would think a peziometric crystal could be used to generate a small voltage during this event and then be counted and averaged using some electronics.

Sorry, this should be "piezoelectric crystal", not "peziometric crystal". Too late for me to edit in the original post...

 

[caferacermike]

That tiny tach is pretty slick. I just looked and the KE70 in my mt372 is cable driven. The cable exits the engine right below the oil filter on the right side of the motor. Just FYI.

Good to know. Could you take a picture of the location? I'm wondering if it's in my casting and with a little work might have myself a tach drive.