Mechanical tachometer problem/question (Atomic Four)

[Rachel]

I previously started a "Wanted" thread looking for a new instrument panel for my (now ex) Atomic Four. I ended up instead removing and refurbishing the existing panel (which had been "whomped" by an errant cord end as the non-electrical side effect of a lightning strike).

There is some further chat about it in the "Wanted" thread, but I thought I'd start a new one for this tach issue. The previous thread is here, for reference: http://plasticclassicforum.com/viewtopi ... sc&start=0

The problem I'm having now is with the tachometer, and has two parts:

1) The tachometer needle is resting on "10" (i.e. 1,000)

2) The tachometer needle does not move when the engine is running

Other than that, it's fine ;)

As this photo shows, it was not resting on "10" as a result of the "whomp"; it must have happened when I had it out for new glass and to try to fix the ammeter (which I don't think is working, but which is less critical than the tach).



Here is what it looks like now (sorry for the horrid photo, it was dark and raining; at least it shows the basic problem).



Here is the back of the tach. All I did when I removed the gauge, was to unscrew that silver, knurled ring at the top of the cable; the main bulge of the tach stayed with the gauge. It removes and reinstalls smoothly.



Unfortunately, I didn't notice when it started reading at "10," but it must have been while I had it out (?) I didn't drop it or anything untoward.

What I have tried so far is as follows:

1) Just running the engine (no movement)

2) Removing the cable at the tach end and turning the square drive cable within by hand; then reinstalling it (no change)

3) Removing the cable at the engine end (looks similar to the tach end) and turning by hand and with a battery-powered drill (no movement)

Does anyone have any thoughts on this? I don't know that it worked in the past, but I'm guessing it did. And also it was sitting at "0" before, so it seems likely to be a new issue that I somehow caused when I took it out.

Rachel

[Clint]

Is "Whomp" a technical term for lighting strike???? I thought you were more technically inclined than that!!!!!

[boatsnh]

Hi Rachel,

Hope it worked prior the the "Big Zap", but if it did not, hmmm.

My first thought is that major electrical "juice" went thru this meter and 100% cooked the fine innards that generate the magnetic field to move the needle.

The needle is driven by a magnetic field that is generated as the cable spins - the faster the spin, the more magnetic field. Same kind of action as on old wind speed indicator - Usually inside something like this there is a verv fine wire winding that generates an eletrical current & creates a magnetic field - there is also some kind of "hairspring" that exerts a "return" force on the needle to offset this magnetic field - the spring is calibrated over the range on the face . Kind of delicate stuff that usually works in milliamps and low voltages.

So if you spin the cable & nothing happens, the field windings may be toast - or you might be lucky and the cable drive slipped off the drive gears or the magnetic drive "pot" is out of alignment and does not allow the needle to move (stuck together) . If it moves at all, and the needle sticks it may be because over time "stuff" gets in there...Id' blow it out with canned air & lubricate the pivot - ultra fine sewing machine oil might do the trick - not even 1 drop.

I have the same unit (as mentioned in prior post) and might take the thing apart tonight on the bench to see what kind of fun little mysteries may lurk in the innards of a 30 year old meter. I'll give a heads up on what I find.

Hate to tell you this, but I'd suspect if you looked inside the tach by taking off the rear cover, and gave it the 'ole electrical smell test you would smell burnt electrical stuff because the windings are cooked - ouch.
Mike

[Rachel]

Clint: Welcome to the forum! And... if you're the Clint who would potentially like to rent my dock (but just called my very technical use of "whomp" into question), well, the price just went up ;)

Actually, I said "whomp" because I don't know for sure that an electrical current that went through the meter during the lightning event, or at least not in the usual way. What happened was that I had an extension cord draped over the cockpit seat and then down in front of the panel, then the female end was tucked behind that guard strip that's over the knobs just so that the open end would face down and no rain would get in.

Well, when the lightning hit the next door boat, my cord was touching his boat stand, and so some current zipped up the cord and exited the end, causing the body of the plug to... well... "whomp" the face of of the gauge panel in a crack-the-whip sort of way. At the time the engine was not installed and the gauge panel was not hooked up to anything. So current was there, nearby, but I'm not sure if any actually went into the panel. The tach needle was still on Zero after that event, as shown in the photo above with the broken glass. It's only since I fiddled with it that it went up to stay at "10."

Mike: Thanks for the technical info on the tach. If you do look at your panel, I would be really interested in what you find. It sounds like you know your way around a mechanical tach a lot better than I do.

Rachel

[boatsnh]

Hi Rachel,
I opened up my tach & it's much simpler than I at first expected - not a whole lot to go wrong here.

There is a permanent magnet, the size if a piece of dentyne gum, on the shaft the needle is mounted on. The magnet is enclosed by a steel cup. For the thing to work, the cable turns a ring on the end of the cup. The magnet is attracted to the cup as it spins and makes the needle rise. Pretty slick.

There are mechanical stops (bent sheet metal) that hit little bumps on the cup to keep it in range. There is a spring in the front of all this that returns the needle to zero & provides tension.

So, to troubleshoot....

Take the tach out of the panel. then remove the 90 degree attachment on the back of the tach - it screws into the tach end. Then you can take the 2 screws on the back cover off and the whole thig is there to see. Turn the needle with your hand - don't worry, it's pretty hard to break. it ought to move easily - if not, some "gump" might be in the movement. Clean with air and blast with wd-40 - Not a delicate movement, just a simple bearing, so wd 40 is fine. Look for the little metal fingers that are the stops - you will hear "clicking" as the stops hit the cup. See if one is bent? Make sure the spring is working - might not be. The pointer should return after you move it to 3000.

Check the magnet with a little wire brad - it ought to be attracted to it. But this is the hard part.....is the magnet at the "correct" strength to work properly?

My sense is still that electrical current (lightning) is the issue if this tach does not read - High current near the panel from lightning could have very easily "demagnetized" the magnets - Just like magnets can be demagnetized by a sharp blow or heat. These are pretty mild magnets to start with, I suspect. FWI was able to get a 1000 rpm reading with perhaps 150 rpm with a drill so it's not running at high speeds.

If yours is toast, let me know & I can send you mine, It's not going into the boat again and I know it works.

Mike

[Rachel]

Mike,

Thanks so much for checking yours out! Great info :)

Since mine is now rather hard to get to (it's wedged in behind the new gas tank and around the corner from the locker opening), I'll be going by feel more than sight and the more I know ahead of time the better: To remove the tach, did you take out the four screws at each outside corner of the tach housing?

And... did I somehow miss that you had a panel like mine that you might be willing to part with? I ask because even though I "repaired" the ammeter (by reattaching one foot and straightening the needle), it still does not work. I'm not surprised, as it took the brunt of the wh...er.... force. The needle feels "floaty" again after I worked on it, but the gauge does not work. So I would be very interested in yours if you are interested in selling it to me.

On the good side, the oil-pressure gauge and the temperature gauge do work.

Rachel

[Oscar]

and to try to fix the ammeter (which I don't think is working, but which is less critical than the tach).

Not sure I agree with that statement. I can hear what the engine is doing, the health of my electrical system has to be measured.

I agree with the previous poster. Time for a tachectomy and autopsy. Suspect some "wiggling and lubing" may do wonders.

[Clint]

Hi Rachel. yup its me from work. Just giving you a hard time. If you need a REAL tech to work on your boat just let me know, I will be glad to fix it right for you.

[Rachel]

and to try to fix the ammeter (which I don't think is working, but which is less critical than the tach).

Not sure I agree with that statement. I can hear what the engine is doing, the health of my electrical system has to be measured.

Well let me re-phrase: Which is less critical to the new owner of the boat than the tach is :)

Actually though, it was a fellow at Moyer Marine who suggested that of all the gauges on the boat, the ammeter was the least desirable to replace, if I had to get new ones. Maybe because people often use other gauges to get data on their electrical system? (Such as Link 10 and the like.)

I agree that once you get used to how an engine runs, you almost don't need a tach, but when you are first getting to know it, it's nice to have one.

Clint: Pfffft (And to think I innocently suggested this forum as a useful source of information...)

Rachel

[Oscar]

The tach on my old Catalina read low, I did the fluorescent tube and tape on the flywheel trick to check it. After that I never looked at it.

people often use other gauges to get data on their electrical system? (Such as Link 10 and the like.)

Agreed. For anyone who goes away from the yellow umbilical cord for more than a few hours and who relies on electricity a condition monitor is a must.

I had three banks, two inverter/chargers and two monitors to keep track of the electrons for up to a week at sea.

[boatsnh]

Hi Rachel,
If your Ammeter is toast I'd suspect it was shorted out - the oil pressure is purely mechanical on that model - Surprised the temp is working.

I do have the mechanical Tachometer for your Instrument Kit - ( I think it fits). Your photos Look pretty much the same as mine but mine does not have the 90 degree angle attachment on the end of the gauge like yours - mine has the cable entering straight into the gauge - I think that angle bit can be removed and swapped - worth a look - I you want this , let me Know....Did you get new glass?? Mine is ok. Tag a e-mil to me and I'll tag a photo back - emil is in my profile..
Mike

[Rachel]

Hi Mike,

I know we don't usually "announce" PMs here, but since the board is about to go down for some period of time, and since you're expecting an e-mail, I hope the group will excuse me this one time.

With that preamble, let me say that I am definitely interested in that tachometer, but that I don't see an e-mail address in your profile. So I'm going to send you a PM (which will show up in the messaging area up to the left of the log in), and I'll include my e-mail address.

Thanks,

Rachel

[Tim]

There's an email link button at the bottom of every post that a member makes, and also the same button found in the profile page on the left side.

[Rachel]

I'm sorry, Tim, but for me there is no "e-mail" link at the bottom of boatsnh's post, nor in his profile (neither yesterday, nor today). There is a "pm" link, but I knew he was expecting an e-mail.

I do get more links at the bottom of other people's profiles - for example there is an "e-mail" and a "www" link at the bottom of yours, but not on everyone's. I was assuming it had something to do with how they set up their user preferences (?)

I'm sorry to have subjected the group to extra posts.

Here is what I see (sorry they are so low res - I'm not sure how to take a better screenshot):





Rachel

[Tim]

Apparently my admin-ness provides me all-seeing capability.

Sorry for the unfounded lecture, since it seems that all do not see the same as I.

[Rachel]

Apparently my admin-ness provides me all-seeing capability.

Well, we pawns struggle on as best we can ;)

(Of course you know I'm kidding, and I'm thrilled to have the forum here as a resource -- thank you very much for all your work, which makes this place so fabulous.)

**************************

Here are photos of a Westerbeke panel that boatsnh has kindly sent me (yes, he has already shipped it; would that I got things sent off so promptly).

The "new" Westerbeke panel:



My original A-4 panel (pre-reconstruction) for comparison:



Back of the new (Westerbeke) panel:



Back of my original A-4 panel (ignore the fuel-line-plugging dowel):




It looks so nice that I think we (new owner/I) may use more parts from this one than from the original! (Not sure yet if all parts will mate with the Atomic Four senders, since this was a diesel panel; but I will find out. Certainly seems like the ammeter should be usable, and the tach, which are the ones I really need.)

I thought I'd post it here so that a future searcher might know that there are other similar panels to look for (I had not realized this).

Thank you, boatsnh :)

Rachel