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10ee Electric Tach

Lmc6d9

Plastic
Joined
May 25, 2020
Hello all!
I bought a 1951 square dial machine with an elsr. It unfortunately did not come with a tach. I searched around a bit for one on eBay, craigslist, and even called monarch about one but no luck. So I have been toying around with the idea of doing something sacreligious to the monarch and making a digital tach that displaced the RPMs in large numbers. I even thought about expanding on that idea by creating a heat map on the tach to represent the motor load. Even further.. adding a hour meter to assist in doing maintenance intervals. I wanted to get the communities takes on it.

1. What is the max RPMs on this lathe? I've seen 4000 or 5000 RPMs but nothing definitive.

2. How did these tachs work? Were they connected to the gearing in the head stock or were they driven from voltage generated from some other source?
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2. I think I see a small hole on the bottom tach cavity where the lead wires used to be.. is that correct?

3. Is this a bad idea? Good idea? Concerns? Alternative sources for tachs?
 
I put one on a South Bend lathe. I used a magnetic pickup mounted so it almost touched the teeth on the spindle gear of the back gears and used a Red Lion digital readout that can be configured for the number of teeth. Installed it N years ago and haven't had to do anything since.

The lathes came in various speeds but you don't have to worry about this installation because it will indicate whatever speed you have. You don't have to worry about exceeding a generator's speed because there is no mechanical connection, only the mounting.

Bill
 
Sacreligious , I wouldn't worry about that. Its not like your trying to restore a One of only Two built Dusenberg or something. This is supposed to be PRACTICAL machinist, so do the practical thing. In the end its just a tool, and you need to make that tool work for you. Don
 
I prefer ANALOG readout - the human eye can integrate a mere peripheral-vision glance faster.

That may be true if you are leading the race on the Nurburgring, but a machinist usually has more time to contemplate things. I personally prefer numbers.

Bill
 
That may be true if you are leading the race on the Nurburgring, but a machinist usually has more time to contemplate things. I personally prefer numbers.

Bill
Same here especially on a dro do not like analog.
 
Did you do anything to balance the pulley after putting the magnet holder on?

Cal

short answer: no.
longer short answer: I replaced spindle bearings, belt idler bearings, backgear bearings and motor bearings. It runs so damn silky smooth at any speed I just haven't really worried about it.
 
short answer: no.
longer short answer: I replaced spindle bearings, belt idler bearings, backgear bearings and motor bearings. It runs so damn silky smooth at any speed I just haven't really worried about it.
I guess you could mount counterweight non-magnetic pieces at 90-degree increments if you were concerned . . .
 
I've put an electronic speed display on my CVA. The sensor is of the 'gear tooth' type and senses the teeth on the spindle lock ring. Sensor is made by Honeywell and produces a pulse output for each tooth.
 
I couldn't resize the image size on my phone, so now I'm back home here's a picture.

SpeedSensor.jpg

The bracket is light alloy, glued to the headstock casting as I didn't want to drill into the rear bearing cavity.
I designed and built a digital display for the front, but this will probably be very different on a 10EE.
 
10EEs are essentially the same.

I would be interested in more details on your display.

Adding extra wires for a spindle-lock interlock switch, similar to what square-dials have, would also be nice.

Cal
 
I have many of those hall effect type sensors from automotive crank position sensors. What electronics board and digital display did you use to convert the multiple pulses per revolution into a displayable RPM?
 
I have many of those hall effect type sensors from automotive crank position sensors. What electronics board and digital display did you use to convert the multiple pulses per revolution into a displayable RPM?
It's entirely DIY. The sensor is, as you say, a Hall effect with integral magnet. The version I have has a single output which switches hi/lo as the segments on the ring pass under it. From there the signal goes to a PCB with a microcontroller on it. The uC is programmed to measure the time between hi/lo and lo/hi transitions. It can then convert this to RPM and display it on 4 seven segment LED indicators. It covers about 8 to 3000 RPM.
My background is in electronics and firmware design so for me, none of this was hard to do. The most expensive bit was having the bare
PCB made, but I think you can even get this done cheaply in China. (As Clough42 did for part of his ELS)
If electronics isn't your thing you can probably get a ready built PCB to do this.
In mine, I can compile the firmware for different numbers of teeth on the ring, but this might be an issue with an off-the-shelf board which would probably expect one pulse per rev.

BenchTest.jpg

Panel was manually engraved on an old Taylor Hobson Pantograph engraver. Still irks me that 'coolant pump' isn't centered with the switches.
 
... If electronics isn't your thing you can probably get a ready built PCB to do this.
In mine, I can compile the firmware for different numbers of teeth on the ring, but this might be an issue with an off-the-shelf board which would probably expect one pulse per rev. ...

That's the part I've had trouble tackling. All the off-the-shelf boards I've found expect 1 pulse per rev. IIRC the spindle lock has 12 teeth on it. I guess I could find an automotive tachometer that can be setup for a V12. :D
 
When I looked into this last, there were a number of PCB places in the US that catered to hobbyists. The price to fabricate a few 4-layer boards was quite reasonable. I know that rabler had some boards made recently, but I don't recall who he used.

Can you post a photo of your finished PCB?

Cal
 
CVA has eight teeth on the ring, so it would be easy to add a chip to divide it by 8. Slightly more difficult to divide by 12 if that's what 10EEs have.
Will take a picture of the board for you tomorrow (it's late here).
 








 
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