As the weather is no good for a model T ride, I dig an old project out of the mothballs.
On my 1922 project I am willing to use a master coil ignition.
Till now I rebuild the master coil. Out of a pile of 15 coils, I bought a few weeks ago on Ebay, I build 12 good working coils. 4 of them are fitted with the old contact points but have new capacitors and are working well on my HCCT. These coils I will use with the master coil. I bridged the contacts of the coils and am ready to put it all in the car but before I do I like to test it all to be sure it works properly. Is there a way I can test the coils and the master coil on my HCCT? What should I read on the AMP meter? Does the cushion spring on the master coil have the same function as on the coils? Should it be set the same way??
(HCCT is home build)
Andre, the Master Vibrators I have encountered use the Model-T coil as originally intended, ie. the points must vibrate to generate the spark. Therefore you should NOT be shorting them out, unless, of course you are using the coil in conjunction with some kind of distributor and point setup. In this case a more modern coil will be superior. The advantage was to have a consistent spark generated for each cylinder with the disadvantage that the coil would get 4X the usage and could overheat and consume the points more quickly.
The purpose of the Model T Master Vibrator (MV) is synchronize the four ignition coils by using the single set of points on the MV.
In addition to other multi-cylinder car coils early Model T Kingston, Heinze and J & B coils had poor mechanical designed coil points (and easily fiddled with by owners)and the MV corrected this problem. KW Ignition and other companies made a boatload of money selling MV's to early Model T owners.
The MV is similar to a regular Model T coil including capacitor except it has no secondary winding and a very low inductance primary winding.
Here is a diagram depicting how the MV is electrically implemented on a Model T contrasting that with the original Model T System.
Notice in the MV installation the original coils have no capacitors or coil points shown. That was easily accomplished by shorting the coil points (closing them with the adjusting screw) or by placing a wire across one of the long ans short point mounting nuts on the four original coils.
only. If you do not short the original coil points you defeat the purpose of the MV.
As you can see in the diagram above the primary windings in both the MV and the original coils are wired in series and the points on the MV provide the opening of the circuit when the primary current reaches 1.3 amps. Depending upon which original coil is being grounded by the timer that coil's secondary winding will fire the associated spark plug.
After shorting the points on the original coils no additional adjustment of them is required.
To test the MV on your HCCT simply wire the original coil primary winding in series with a MV laying on the bench as shown in the diagram and adjust the MV for the proper spark ring/ammeter appearance you desire.
Hope this helps?
Ron the Coilman
I will try this out during the weekend and will keep you posted.
I couldn't wait till the weekend, I just had to dig it out.
As I rebuild the MV, a few months ago I had no HCCT and test it with a 12V battery. I was happy to make it buzz with new points and a new capacitor (brown one).
On the HCCT it didn't work with the new points. To make it buzz I had to change the new under point by an old one with screws.
After changing the points I could set the coil at the same current and spark as a normal coil.
To set the points right is just a little different.
On a normal coil the upper point is set so that the cushion spring make the point go down till there is 1.3A current and no double spark.
On the MV the upper point is set so that the cushion spring is the all way down to get 1.3A and no double spark. The setting is done by the set screw on the top of the points. Bending the upper bridge with the fun project tool was no good.
Tried the 4 coils and get for all the same result. Now I need just to fit them in the car, run with it and try it out on magneto and battery.
To do this I will take a complete working coil box in the car and a few tools to come home as MV fails.
Andre, A few years ago I tried hooking up a master vibrator on my 1912 touring car. There was a wiring diagram in the lid of the MV. I went on a small mini tour with the car and experienced the MV occasionally mis-firing.
Yes, the entire system quits when the master quits and the car stops.
I am guessing that the master vibrator had some type of internal problem and I finally give up.
I set the 4 coils on my motor driven home built coil tester and had no more problems without the MV
Good luck with that MV
In my willing to understand to model T ignition I did more try outs.
I have a second MV coil (just the inside) and tried to make it work as the first one. As on the first one, after a few contact changes (Have no new contact at this time) I was able to make it buzz as the other one, but again, the cushion spring is all the way down and don't follow the contact point. So next question is why the cushion spring don't need to work on both MV's??
After the night (of thinking not sleeping) I decided to try to build a MV myself. I took a ignition coil with an open secondary winding. Soldered two wires on the underside and the ground post, cleaned up the old points and bridged the contacts with a new capacitor and give it a try, the same way as the MV.
After a few adjustment I could make it buzz and got 16 sparks on the HCCT. The only difference is here the cushion spring had to be adjusted to get no double spark and the 1.3A .
Could it be that on the MV with is low inductance primary winding the time to build up the 1.3A is very short and don't need the cushion spring.
A normal coil needs more time to build up the 1.3A and need the cushion spring to give it the time needed?