Analogue tachometer for Onan / Kohler

[wheeledhorseman 573]

Whenever tachometers get mentioned there seems to be a lot of interest. Recently Mark (meadowfield) showed that it's possible to modify an existing standard one. Having some understanding of electronics and having been known to design and build circuits from time to time, I too have been thinking of having a go myself for quite a while now. Fine for me, but not much use to others, and the reality is that making them for others would be a very time consuming thing to enter into.

 

It occurred to me that there must be another way that others can do easily if it works. So a while back I purchased a universal marine tachometer made by Durite here in the UK. Cost me just under £50 for a 52mm guage that's very nicely made and water resistant. A bit of a gamble but in the end there's no other way to be sure.

 

'formariz' made this comment in another thread about regulators....

 

There are at least a couple members here that seem to be knowledgeable enough to accomplish that. The same goes for modifying an analogue tachometer to be used on Kohlers. Probably would be a bit expensive but I think many of us would appreciate and use those services.
 

so I thought oops, I really must find time to try out my Durite tacho - happened today.

 

 

I bought it for my 316 so it was a case of will it work with an Onan. You need to have something like the digital hand held tacho on the right to be able to set up a 'universal' tacho like the Durite. Mine is a really cheap one off ebay that I bought to set up the idle and governor on the first Kohler I rebuilt - it's been an invaluable thing to have ever since.

 

 

You stick a piece of reflective tape on a rotating part, aim the laser at that part when it's spinning, press a button and hey presto, a digital readout. (sorry no pic but only one pair of hands today).

 

 

There's a whole bunch of wires come out of the back of the tacho. One's for powering it on a 24 volt system, one's for the LED back light, and one is apparently 'not used' but it must have a use at the factory I guess. I only needed to use the other three for a test and it only took a couple of minutes to hook it up to the battery and one wire to the voltage regulator.

 

 

It worked (once I'd found the right one of the pair of wires from the alternator) For some reason the first one I tried gave a reading but as engine revs decreased the tacho reading increased. In the photo the wire is connected to the rear most tag - the one that worked correctly.

 

 

The initial reading was high compared to the hand held tacho's reference so it was a matter of adjusting the Durite to match.

 

 

To do this you remove the sealing grommet at the back and inside there's a little trimming pot to adjust. It covers a wide range so turning it a small amount makes a big difference to the reading. Adjusting it gently is the order of the day with a little cross head screwdiver that fits.

 

I checked it at different revs vs the digital one and all seemed good - happy horseman and happy horse!

 

 

(don't know why but he always seems to be happy)

 

Could have left it there and got on with making a new dash panel to take three dials for the 316 but I knew you'd kill me for not trying it out on a Kohler. Didn't really want to go through calibrating it again on another engine (only kidding) so......

 

 

Sorry about needing to use flash but it was at the back of the queue in the barn. Yes it works and it didn't need recalibrating so I guess there's the same number of coils & magnets to an alternator on an Onan Performer and a K301 that has the complete set of stator coils and magnets. I didn't do a full check so it might have needed a small tweak but it WORKS!

 

Don't ask which of the two wires from the alternator I connected it to, they're both the same colour and it worked with the first one I tried.

 

I was kind of 95%+ sure it would work as these are 'universal' and have to be able to work with almost anything from a Mercruiser with standard external alternator to outboards where it's inside the flywheel like a GT.

 

This particular marine tacho also had a 0 - 4000 rpm scale, bonus!

So all I can say is that it worked for me on a 16 hp Onan and a 12 hp Kohler with full set of coils on the stator. It should work for the rest of the engines in the same ranges but I don't have other engines to test other than a 10 hp Kohler. 

 

Will any make of tacho work? I hear you ask. I don't know if the Durite range is available in the US but I'd hazard a guess that a similar 'universal' marine tachometer that's adjustable and made by a reputable manufacturer should work. I've used the Durite 052510 product that's a 52 mm (standard meter size like the voltmeter and hours meter on the 316) and 0 - 4000 scale . They also do a bigger 85mm model with 0 - 4000 scale for those who suffer dashboad envy. The one I've used is 80mm deep, not sure about the bigger dial one.

 

The full range can be found here http://www.durite.co.uk/pdf/2012/5/05.6_Equipment_and_Accessories-Dashboard_gauges_Automotive_and_Marine_and_Accessories.pdf

 

I could have gone for something cheaper from China that claimed to be universal and wasn't or that needed adapting in various ways but at the end of the day just under £50 for one that's water resistant, made by a well known manufacturer and carries a warranty was to my mind a good deal.

 

If you decide to take the plunge with other makes please do report back to this thread - stuff gets easily lost on RS as time passes. At the end of the day this worked for me today when I tried it - that's all I can guarantee.

 

Hope others find this useful.

 

Andy

[JackC 616]

Thanks for the post.  The more instrumentation the better as far as I am concerned for early warning and proper tuning purposes.  Head or oil temperature would be good also especially for the twin cylinder engines..

[meadowfield 2,545]

Andy,

You did the same as me, I'm just a tight Yorkshireman buying a $10 unit from china and rescaling and then tweaking it in pretty well the same way

...I do a nice line in 0-4000rpm stickers to convert now :)

[formariz 11,849]

Upon reading this post I did a bit of searching and did find some marine tachometers made here, used I believe, and not too expensive with the right scale. Also they only have 3 connections those being, battery, ground,and signal. Some can also be programed for the number of poles in the flywheel, or number of teeth.

 

Since only two wires come from the alternater inside flywheel on a battery ignition motor, both with AC current either wire should work. One assumes then that all is needed is to tap into one of the two wires.

 

My concern is if there is any possibility of damaging stator while attempting this.

Edited April 3, 2014 by formariz

[wheeledhorseman 573]

There is a difference between the type you've shown here and the type I used formariz.

 

Here you have a tacho that is adjustable via one of six switch settings so that it covers a range of different applications, probably most. It could well be that one of these switch settings will give the readout required from a Kohler or Onan but I wasn't going to chance it. This type of tacho doesn't need calibrating against a hand held one - it's factory calibrated but there are just the six preset settings are available. (I think meadowfield and SOI worked out how many 'poles' there are to a Kohler alternator)

 

The type I used (and meadowfield for that matter I think) are truly universal in that the adjustment is continuously variable rather than limited to just six precise settings. The disadvantage is that you need the hand held tacho to calibrate it accurately. If you think you can judge the tickover speed of your tractor by ear then you could use that method.

 

I went for the type that I was pretty much certain would work rather than the type which might work. Anyone out there tried one of these?

 

On the matter of your other concern, electronic tachometers work by sensing pulses from the stator coils, any current they draw from the stator is truly microscopic and will not affect its charging operation in any way. As long as the connection of the sensing wire is not bodged in such a way that it could end up creating a short circuit i.e. the cable is routed sensibly away from heat or moving parts where the insulation could become damaged then you should have no issues.

 

Andy

[formariz 11,849]

I understand. It may or may not read accurately in one of positions, but there will be no fine adjustment to make it 100% correct. Found this other one which I believe has such adjustment. I am not sure of cost. Durites seem to be only available from there and they are picey being well over $100.00 with shipping.

 

 

 

 

 

 

infosheet-fp-001-0033_B_Variable-Freq-Tach.pdf

Edited April 3, 2014 by formariz

[wheeledhorseman 573]

When I was looking for one of these I spent hours trawling the net and trying to make sense of manufacturers' and vendors' technical descriptions, all of which seem to come at it from a different angle.

 

I've checked back on the thread by Mark (meadowfield) which he confirmed that the 15 amp alternator on a Kohler acts as a nine pole producing nine alternating cycles per crankshaft revolution.

 

Looking back at the first tacho you posted (with the white face) the nearest setting on the back is for an 8 pole. It would work but the reading would be higher than actual as it would be recieving an extra pulse per revolution. I'll leave you to calculate the % error.

 

The Faria in the info sheet link is a nicer looking dial IMHO and pretty versatile but it's difficult to make completre sense of their spec.

 

 

I understand the frequency bit but in relationship to what? I'm going to make an assumption here that it is for full scale deflection i.e. 4000 rpm.

 

So the Kohler produces 9 cycles per revolution, at 4000 rpm that would be 36,000 cycles a minute (9x4000). In a second that would equate to 36,000 / 60 = 600 hertz. My guess would be that you use either the 400 hertz switch setting tweaked up to 600 Hertz (Hz) by the fine adjustment potentiometer or the 800 Hertz switch setting tweaked down by the fine adjustment. Either way I'm sure they will have made sure that all frequencies between 400-800 Hz are achievable.

 

I hope this helps you. It might be worth contacting Faria to check that my assumption re 'frequency' is true i.e. frequency for full scale deflection (4000 rpm)

 

Andy

 

 

[meadowfield 2,545]

Upon reading this post I did a bit of searching and did find some marine tachometers made here, used I believe, and not too expensive with the right scale. Also they only have 3 connections those being, battery, ground,and signal. Some can also be programed for the number of poles in the flywheel, or number of teeth.

Since only two wires come from the alternater inside flywheel on a battery ignition motor, both with AC current either wire should work. One assumes then that all is needed is to tap into one of the two wires.

My concern is if there is any possibility of damaging stator while attempting this.

You can't break anything, there's 9 poles on a k series stator, so it might need a little adjustment as Andy says.

Oops, posts crossed!

Edited April 3, 2014 by meadowfield

[formariz 11,849]

Seems that the search for the elusive tacho is getting closer!

The Faria is a pretty nice one since it is also only 2 inches in diameter and I believe it also comes in white face. Now it may be a matter of cost which I have not yet found. I will indeed contact them for more precise information on their specs.

 

Now having a relatively good understanding how these work I gather that having one work for a starter/Generator system is not a possibilty?

 

Thank you very much to all of you for the help.

 

Cas

[wheeledhorseman 573]

Seems that the search for the elusive tacho is getting closer!

The Faria is a pretty nice one since it is also only 2 inches in diameter and I believe it also comes in white face. Now it may be a matter of cost which I have not yet found. I will indeed contact them for more precise information on their specs.

 

Now having a relatively good understanding how these work I gather that having one work for a starter/Generator system is not a possibilty?

 

Thank you very much to all of you for the help.

 

Cas

 

Hope your search come up trumps and at a cost that's bearable.

 

Re the starter generator scenario I'm working on something that might make this possible.

 

If you look back at how the hand held tachos work with the bit of reflective tape then consider this....

 

I haven't tried this yet but a traditional auto tacho that gets its pulses from the points expects two pulses per crankshaft revolution on a 4 cylinder engine. (most of these tachos can be set for 4, 6, or eight cylinder engines)

 

So my idea is this - stick two bits of reflective tape on the PTO drive (like the one in the picture) but 180 dgrees apart and mount an optical sensor close to it. I've had the components to hand for some time just haven't got round to trying it. If the idea works and you're not bothered about visually having a little sensor that shouldn't really be there then it could just be the solution.

 

Andy

Edited April 3, 2014 by wheeledhorseman

[formariz 11,849]

After a few hours of searching the 2" Faria is nowhere to be found. Found another model but it is 4" and expensive. Incredibly the least expensive one with the best manufacturer description of adjustments is the Durite. It will come out at slightly under $100.00 with shipping. Not only it seems to be a quality item but we know it works so I may just be getting that one.

 

 

"So my idea is this - stick two bits of reflective tape on the PTO drive (like the one in the picture) but 180 dgrees apart and mount an optical sensor close to it. I've had the components to hand for some time just haven't got round to trying it. If the idea works and you're not bothered about visually having a little sensor that shouldn't really be there then it could just be the solution."

 

Found one company which makes pretty much the above in Canada for farm tractors but with sensor it coats about $300.00+

[Save Old Iron 1,563]

All,

 

what exactly are you looking for in the way of diagnostic information from a tach resident on the tractor?

 

Aside from the "cool factor" or "eye candy factor", what use is the tach permanently mounted to a garden tractor?

 

High RPM governed speed is the only one that comes to mind. Anyone else have preferences to specific RPM's that are crucial to monitor?

 

What about a single OVER REV warning light if the RPM's exceed 3700?

An automatic over -rev limiter is easy to construct.

Edited April 5, 2014 by Save Old Iron

[meadowfield 2,545]

All,

 

what exactly are you looking for in the way of information from a tach resident on the tractor?

 

Aside from the "cool factor" or "eye candy factor", what use is the tach?

 

High RPM governed speed is the only one that comes to mind. Anyone else have any RPM's that are crucial to monitor?

 

What about a single OVER REV warning light if the RPM's exceed 3700?

Chuck, I think you nailed it for me...

Cool factor agree an over rev light would be more useful.

[wheeledhorseman 573]

I could write an essay on this one starting with why did WH produce chrome hub caps for machines designed to work in the dirt and mud? I guess even they realised that for some 'eye candy' is important and there was a market to exploit. From the 'eye candy' perspective tachos are what real tractors have - was Pond wrong when he wanted to make WHs that looked like tractors? Isn't that what has given them the appeal that they have?

 

In terms of monitoring a tractor then sure, lights are in a way all you need but gauges are a way of monitoring changes that need investigating so a transmission temp guage as fitted on a D is way better than an over-temp warning light, and oil pressure guage is way better than a critically low oil pressure warning light and thinking about the tractors I have with the idiot light panels, they can't really be seen in bright daylight and get generally ignored by the operator anyway.

 

In my case there's eight acres to be looked after by several horses operated by a number of people, I added an hours meter to my C-120 auto for obvious reasons otherwise I wouldn't have the slightest idea when a transmission service was due. Actually all my hard workers could do with one as they probably exceed the engine service intervals by having just a yearly service.

 

The tacho I'm adding to the 316 is to my mind essential as the Onan is probably the only engine I've got that needs highish revs to prevent the head coking up quickly, though like the Kohlers it actually has good torque at lower revs and is happy to pull a trailer, roller or aerator set thus. So it will be easy now to say to whoever's on it - keep the revs above xxxx. WH knew this but only fitted it to the top of the range Onan tractor - cost I guess and same reason they didn't fit an hours meter to all autos. I'll also be adding a tacho to my D-200 with 3-point as I want to use the pto shaft at some stage but there's no way of knowing the rotational speed without one either monitoring the engine, or the shaft itself - hence trying out an optical triggered one that will run from the pto shaft.

 

Feel free to shoot me down guys, I've got my kevlar on.

 

Andy

[Save Old Iron 1,563]

No shooting anyone down from my vantage guys. I love this stuff and probably could qualify as the patron saint of gizmos.

 

I thought I was missing out on something with the tach's as I haven't had to EVER use one on my garden tractors. The JD diesel compact I have - yes - I need one for PTO speed for brush hogging and such.

 

I fully agree with instrumentation for engine temp and trans temperatures.

 

@ Andy and Mark - where I was going with the LED RPM indicators is maybe a F/V chip with a few comparator trip points (user adjustable within reason) to light LED's - one at idle and maybe 3 additional ones for 3400, 3600, and 3700 RPM's. Other than those speeds, I'll be darned if I know why any one would want to monitor anything in between.

 

The irony of chrome hub caps had escaped me until you mentioned it!  I have never owned a pair of those either.

Edited April 5, 2014 by Save Old Iron

[formariz 11,849]

Definitely the gizmo addiction for me Chuck. Like many things we do to these tractors, nothing really necessary or sometimes useful. However watching the flicker of that little needle just makes me happy.

[wheeledhorseman 573]

I love healthy discussion with a few tongue in cheek comments thrown in Chuck, it's one of the great things about RS.

 

 

 

@ Andy and Mark - where I was going with the LED RPM indicators is maybe a F/V chip with a few comparator trip points (user adjustable within reason) to light LED's - one at idle and maybe 3 additional ones for 3400, 3600, and 3700 RPM's. Other than those speeds, I'll be darned if I know why any one would want to monitor anything in between.

 

 

Sound idea Chuck. It's simple but effective and I'm sure many would benefit from having one and even want one. The possibilities are endless when it comes to applying electronics, my problem is lack of time despite having retired (so don't count on it too much!)

 

On the analogue (and probably digital) tacho front, they can give indication of a faulty electronic ignition module (aka igniter in the US I believe). If your engine starts missing a beat or two and the tacho flicks at the same time then its often the ignition module that's on its way out. This led me to think about sensing the dwell angle if you're taking pulses from the points to bring an LED on if its time you need to clean, adjust, or replace them. A bit beyond the F2V chip idea but it's possible. So many ideas, so little time, and so much grass to mow etc. Its a hard life  even after retirement!

 

 

Definitely the gizmo addiction for me Chuck. Like many things we do to these tractors, nothing really necessary or sometimes useful. However watching the flicker of that little needle just makes me happy.

 

 

And why not - it's going to make me happy too when I get round to actually fitting mine to the 316. Each to his own, and all happy horsemen - what it's all about!

 

Andy

[formariz 11,849]

Came across this one made in India, which seller states that there is some adjustment through little hole in back of it. Rather cheap at $25.00.

[bmsgaffer 2,043]

Came across this one made in India, which seller states that there is some adjustment through little hole in back of it. Rather cheap at $25.00.

 

I saw that one, but I am not sure it is water resistant/weather proof, which is a good thing on tractors that may get caught working in the rain.

[Deere Hunter 54]

 

'formariz' made this comment in another thread about regulators....

 

There are at least a couple members here that seem to be knowledgeable enough to accomplish that. The same goes for modifying an analogue tachometer to be used on Kohlers. Probably would be a bit expensive but I think many of us would appreciate and use those services.
 

About 10-12 years ago you could send an Autometer Sport Comp Tach back to the tech department to get recalibrated for a kohler. From what I remember it was only on the analog tachs could they do the recalibration. I had this done to a tach and it was cheap! Was like $25 bucks and they rebuilt the tach, new lens, tach housing, wires, etc all for that price and covered shipping. Never had a tach on any of my workers, just my pullers. I recently installed a tach from MWSC that they are building in house. Its a pretty nice piece that shows max RPM and playback. Of course this isn't something I would put on a worker.

[123GO 78]

Great thread here folks, my sights are set on a tach for mine too and I dont give a shart what anyone thinks of any of my WH candy. 

 Guess folks just need to get over how we twerk'em!  Or is it tweek'em? Ya I can not twerk, sorry guys..

 Shoot if we all do exactly like the others, sadly every song would sound same