Another Hand Crank Coil Tester Question

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Model T Ford Forum: Forum 2014: Another Hand Crank Coil Tester Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Friday, April 11, 2014 - 09:47 am:

Can anyone explain this plate on the Hand Crank Coil Tester?

Coils have to be adjusted to 1.3 Amps.

When testing the Magneto in a running Model T engine, the plate notes that .6 or .8 Amps is an acceptable level for performance.

Should the engine be running on Mag during this test?

HCCT Plate


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, April 11, 2014 - 09:55 am:

Jim
Connect the coil tester "Mag" and "Ground" wire connections to the engine frame and hogshead magneto terminal, start the engine and run on battery when conducting the magneto output test.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Friday, April 11, 2014 - 10:29 am:

Will the same output result be the same on engines without electrical equipment ( pre 1919 ) or added battery ? If not, what output result is satisfactory on HCCT meter ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie on Friday, April 11, 2014 - 10:43 am:

I presume there is an inductor in series with the meter so that the HCCT gauge will read some arbitrary amount (in this case .6) when powered by a good magneto. What the gauge reads is a function of the circuit and will register the same amount for any particular magneto(or nearly the same) regardless of engine speed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, April 11, 2014 - 11:03 am:

That might be what the coil thing/choke inside the housing is for. :-) (If it is still there and working)


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Friday, April 11, 2014 - 12:09 pm:

Well, actually there was no inductor in the base, but Ron "Coilman" came to the rescue and had one.

Recently I got another repro HCCT that needed my help and Ron has again come to my rescue.

I was comparing one repro HCCT to the other one and right away I realized what the problem was with the new one.

The original K R Wilson coil tester that I am restoring had one, but it was too rusty and corroded to suspect it might still work, so I got two of them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Friday, April 11, 2014 - 02:43 pm:

Let me try my question one more time!

Please try to answer the basic question: Why is a magneto considered “good” if it can deliver 0.6A (instruction plate) or 0.8A (on the meter scale) yet a Model T coil AVERAGE current is 1.3A which is way higher?

Yes, you run the car on battery during the HCCT magneto test.

Yes, you connect one HCCT magneto test terminal to the magneto post and the other HCCT terminal to engine ground.

Yes, there is an internal inductor in the base of the Allen HCCT which serves as a load for the magneto during the test.

Yes, the magneto current reading will remain constant regardless of the engine speed if the magneto is good.

The $64,000 question is: Why is a magneto considered good if it can only supply 0.6A or 0.8A but a properly adjusted Model T coil will draw 1.3A AVERAGE (the peak current is more than twice that amount!)?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie on Friday, April 11, 2014 - 03:23 pm:

Because the .6 amp reading is a function of that particular circuit. It has to do with the value of the inductor and the load of the meter. A different inductor value would give a different reading. For instance, the inductance of a T coil is different from the inductor in the HCCT, so it gives a different (higher) reading. The value of the inductor in the HCCT was likely chosen to give a good steady reading over a large RPM range.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, April 11, 2014 - 04:21 pm:

Tom C. has explained it the best but there is another reason I think that that the amount of current is tested different than the amount of current that a T coil draws and that is because when testing the magneto with the HCCT inductor alone you have a way different load current wave form than you do when there is a firing T coil as the load rather than just an inductor. I suspect that the inductor value was engineered from the available cores at that time. What you have to appreciate is that that inductors are not constant value devices like resistors or capacitors but inductors can actually change inductance value signifcantly depending on the level of AC excitation. The HCCT inductor would be a difficult thing to design with laminated iron core but often nickel was added to improve linearity which is to mean that the need here is for an inductor with nearly perfect linearity so that the excitation level doesn't change the value of the inductor. It is a simple circuit but the component choices available can make it complicated. The real question that is answered is that the magneto test mainly relies on the fact that a good magneto will put out a linear increase in AC voltage with a linear increase in RPM and any deviation from that says something is not right with the magneto and their experience has proven that to be a fact. The starting current (or minimum current) doesn't have to be exactly the same as a coil anyway but just something in the ball park since you must remember that the magneto load current waveform is going to be different between the HCCT test using an inductor and a live coil test.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Friday, April 11, 2014 - 04:39 pm:

John Regan:

All well & good.... Running a engine on magneto ignition, no battery, ..... what HCCT meter reading would be acceptable for a good magneto ? Would the double stack coil ring & different size magnets have the same readings as a later magneto coil ring with the later size magnets...... still having the engine run on magneto ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Friday, April 11, 2014 - 04:52 pm:

A friend of mine acquired a KR Wilson HCCT that had been in one family since new (side note, I've known this tester for 40 years, but it was never available for purchase, just use--I missed out somehow, but now it's still available for use, so no real change there!). I've been looking around for an instruction sheet to 'splain it to him, and haven't found one--where do we need to look? I always used it "as is" (and under the work bench where it's been for decades) and set my coils to the 1.3 value, never questioned it all, but the new owner "wants to know why!"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, April 11, 2014 - 06:34 pm:

David
Try this link.
http://www.funprojects.com/pdf/HCCTManual.pdf
This is an original manual that came with the Ford part number 18 Z 245 HCCT. There is no significant difference between this and any other type HCCT.
Ron The Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, April 11, 2014 - 06:37 pm:

Well that did not work. Try the FunProjects website documentation library.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange on Friday, April 11, 2014 - 06:54 pm:

When embedding links into a post, it seems to work better if you have a blank line before and after the link, like so:

David
Try this link.

http://www.funprojects.com/pdf/HCCTManual.pdf

This is an original manual that came with the Ford part number 18 Z 245 HCCT. There is no significant difference between this and any other type HCCT.

Ron The Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Friday, April 11, 2014 - 11:21 pm:

Thanks Ron, & Mark.
I'm forwarding this to him (and keeping a copy for myself too!).
David


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