Why not use ign. based Tach on a tractor?

Inno · Jun 12, 2010

Like the title says. For example on my MF 202, the tractormeter is there but it is beyond repair, the cable has been missing for years before I got it and I will eventually switch from a generator to an alternator thus having nowhere to connect it to.
I realize that a tractormeter also shows you what your speed is in a certain gear but you could easily figure out your speed by RPM and looking at your old meter. So does anyone simply run an electric tach off their ignition system? I would think it would be more reliable and simpler.

guido · Jun 12, 2010

Hello Inno,
You can also get one with a magnetic pick-up at the crank. If you know the final gear ratio, the tack is all you need to know the traveling speed.
Guido.

Inno · Jun 12, 2010

Thanks Guido.
I guess what I should have asked is can anyone think of a good reason why I would not want to do that, aside from keeping the tractor original, which I have no intent of doing as my tractor is strictly for utility, not beauty. I will eventually paint it and make it look nice but there is already enough that is not original that I'm not worried about it.

MNGB · Jun 12, 2010

There's no reason you can't do that, I installed on on my "B" Farmall about a year ago while working on the gov/carb to see what the RPM's were, I liked it and it's still on the tractor works good.
GB in MN

Allan in NE · Jun 12, 2010

You can,

"If" you're not concerned about the accuracy of the hour meter.

A cable drive on these older tractors give a truer, slower count when the engine is operated at less than PTO speed, whereas with the electric hour meters, the hour meter is more of an "on or off" thing.

In other words, lighter work will result in a lower hour count on the old spring driven tachs.

Just a thought; and somebody please correct me if I'm wrong.

Allan

MN Scott · Jun 12, 2010

Your right Allan. New tractors all have electric 'real time' hour meters. My loader tractor accumulates hours two times as fast as my old IH's when doing light work. So if you have a electric hour meter tractor that was used for light low RPM work with say 5000 hours it really probably has 2000 to 2500 'work hours'. So that newer high hour loader tractor might be a pretty good buy compared to an older mechanical tach high hour loader tractor.

Leroy · Jun 12, 2010

I don't see how a tack could have any bearing to an hour meter, all a tack will do is give engine RPM to be able to set for correct PTO speed. Now an electronic hour meter would do as you say but any tack's I have heard of do not have an hour meter in them. The tractor would have to be gas and the tack would have to work with the number of cylinders you have. I know some tacks can be set for a 4, 6, or 8 cylinder but if you have a 3 cylinder what do you do? Have read on here before that in the case of a 3 cylinder you have to hook to the 6 cylinder and devide what it shows by 2 to get the correct speed.

Allan in NE · Jun 12, 2010

That's my whole point, Leroy.

Hours spent in the seat and engine speed is not the same as the actual accumulated engine hours.

Allan

Allan in NE · Jun 12, 2010

That's my whole point, Leroy.

Hours spent in the seat and engine speed is not the same as the actual accumulated engine hours.

Allan

Roger in Iowa · Jun 12, 2010

I had a tachometer that ran off the ignition on a car. Made it hard starting. Put in a switch so tach could be shut off when starting. Made a big difference.

Tach later failed and would not allow engine to run, must have shorted out, when switch was on.

I think one operated magnetically off of the crank would be more practical and not interfere with ignition and would not have to compensate for number of cylinders. Would also work on Diesel engines!

bc · Jun 12, 2010

On my little airplane, it has the cheap little rectangle tach where the wire makes about 3 wraps around a plug wire. It will switch to hours as well.

gene bender · Jun 12, 2010

Whar about if you arent running the seam size tires as the tractor had when new your old guage isnt going to have the rite gound speed anyway.

Bob Bancroft · Jun 12, 2010

I have a couple of "TinyTach"s on my little AC's. They give me accurate RPM and total hours. If for some reason(like spraying) you might want accurate ground speed, grab a little GPS.

Inno · Jun 12, 2010

(quoted from post at 10:33:46 06/12/10) Whar about if you arent running the seam size tires as the tractor had when new your old guage isnt going to have the rite gound speed anyway.

That is true but it wouldn't be too hard to figure out your speed with a little math.

Thanks for all the replies, I think I'm going to give it a try. I have never heard of a tach. causing hard starting etc. But who knows, maybe on an engine never designed for it it might cause problems. It could also be a wiring problem. I would be using it mainly for setting up the governor and carb etc. but when I eventually do want to use the tractor with 3ph equipment with the PTO I will definitely want it working.

Inno · Jun 12, 2010

(quoted from post at 10:41:59 06/12/10) I have a couple of "TinyTach"s on my little AC's. They give me accurate RPM and total hours. If for some reason(like spraying) you might want accurate ground speed, grab a little GPS.

I like the idea of the Tiny Tach but according to their website the battery in them only lasts around 5 years and is not replaceable. That doesn't sound to economical to me.

Crem · Jun 12, 2010

Inno,
I have cut and pried open the back on those Tiny Tacs and replaced the coin shaped battery in them. I had a couple of them given to me and I thought why not try. I think that mine has been running over 5 years now so maybe I better write down my hours if I want to save them.

Traditional Farmer · Jun 12, 2010

I have a RPM tach from Auto Zone that can be switched to 4,6 or 8 cylinder engines.The old cable tachs ran up hrs at a set maximum RPM run half that RPM and it ran up 1/2 hr on the tach for each hr of operation.The electric tachs just run like a clock for however long the current goes to them.

Inno · Jun 12, 2010

Yes, I have seen some of those which show you hours at a certain RPM. Probably a lot more useful for maintenance purposes.
I think for the limited use my tractor sees, I'll probably just ballpark my maintenance or do things like oil changes once a year. Just keep an eye on fluid levels and the cleanliness of them etc.
I have the backhoe off it and it is in my shop right now getting a whole bunch of things done to it. Did the oil last night and replaced the starter drive. I plan to add some work lights to the back and clean the carb, flush the fuel tank...........the list goes on and on!

MN Scott · Jun 12, 2010

In older mechanical tack tractors 'All IHC tractors' the hour meter is built into the tack and is mechanically driven from the engine. There is no compensation for engine RPM to time elapsed, faster engine turns, faster hours add up. So if you sit in the seat for 4 hours running the engine at 1000 rpm you will end up with 1/2 the hours on the tack than if you sit in the seat 4 hours running it at 2000 RPM.

Inno · Jun 12, 2010

For maintenance purposes this is probably better. So essentially the hour meter is logging actual revolutions of the engine, which you would think would be much more useful than knowing how long the engine has run for without knowing how many revolutions it has made. Combine that with an odometer and you would have a very good handle on maintenance intervals.

Why not use ign. based Tach on a tractor?

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