I'm playing around with my first coil rebuild. I checked that the cushion spring was resting against the rivet head, but when I install the points and adjust the gap, it bends the heavy upper section of the point down against the cushion spring so that it is now resting aginst the upper section instead of the rivet. I hope I am being clear. With the point laying on the bench, the cushion spring rests against the rivet head. With the point on the coil and adjusted for .032 the cushion spring is up against the upper support.
I have put washers under the stand-offs to bring them up to the level of the coil top. This does not help. I think I need to bend the upper point support (Not cushion spring), near the mounting holes, but wanted to get some other input before I do this, as some of these "Adjustments" can't be undone.
Thanks for any help,
This is common and is caused mainly by the point upper brass piece not being made out of thick enough brass. Original points have .050 brass up there and repro points are about .040 and this results in the upper bridge piece then bending in a slight ARC from end to end. Sight down the upper bridge piece once you have the gap at .032 and you probably can see that it is bowed from mounting end to adjuster nut end. To de-arc this upper bend, I usually hold the coil in my left hand with my thumb up under the front lip of the bridge - thus my thumb is laying flat against the adjuster spring. This is to support the spring end of the bridge. I then tap on the very center of the upper bridge with my small coil point adjuster mallet while sighting down the length of the bridge to see when it is straight again. Once it is straight the points may or may not be resting against the rivet but usually they are but you will have to reset the 1/32 gap since it will change. If they are not then you have to add tension to the coil point cushion spring. Some do that by rolling a nut driver across the spring near the mounting end of the bridge but that requires you to remove the bridge again. I make a tool that allows you to increase or decrease that tension while the points are installed but in truth - without an HCCT or Strobo-Spark tester, you will be flying blind. There simply is no way to know when you have the right amount of tension without testing the coil in either of those type testers. Too much or too little tension on the cushion spring will cause the dreaded "double sparking" that makes the T run like crap. Welcome to coil rebuilding.
Using the nut driver procedure of adding tension to the cushion spring is depicted in the MTFCA Coil Rebuilding videos. At the time (almost ten years ago) it was the only method available.
The problem was that unless you are very very careful you could damage the upper point bridge and render it useless and unrepairable.
Subsequesntly John Regan developed the tool he now sells and he allowed several of us rebuilding coils to give it a try. We liked it's simplicity and low cost. It's use is foolproof and, if properly used, will not damage the bridge.
Ron the Coilman
Are you and Ron talking about the same tool, or two different tools? If it is two tools, I think the one Ron's is talking about is the one I ordered from you. Maybe it will come today.
I was just fitting things up last night and ran into this. I will wait until the tool comes before I get into this adjustment thing very seriously. Yes, I can see the upper bridge with a pretty good bow in it. I thought about straightening it out last night, but wanted to ask before I did something wrong.
John and I are describing the same tool. It is for setting cushion spring tension.
The other tool is for setting the cushion spring rivet height and hence cushion spring travel.
Ron the Coilman
Thanks, Ron. I think I'm getting close.
Hal the Coilman
Perhaps photos of both tools is in order to eliminate any confusion.
This photo is of the tool for adjusting cushion spring tension:
This photo is of the tool for adjusting the cushion spring rivet height:
Ron the Coilman
What is the max. travel of the cushion spring ?
The FORD Book says .005 is that correct ?
thanks for your answer Toon
To properly answer your question I need to tell you the entire story.
NOS coil points made in the Model T era had .005 cushion spring travel.
The coil points available today have cushion spring travel much greater. I measured cushion spring travel on several upper point bridges this morning and found .018-.020 cushion spring travel. Clearly this must be corrected to get the point alignment mounting geometry correct. That is the purpose of second tool pictured above.
We have also found that by increasing the .005 cushion spring travel to .010-.012 the coil works better and you can still properly install the points. It is not important which number you choose (.005-.012) but it is important that each of the four coils cushion springs are set the same to avoid inter cylinder timing differences.
One last point. Many people think the .030 point contact gap is the critical adjustment, it is not. As long as the contact gap is greater then the cushion spring travel the coil will operate correctly. This of course assumes that the cushion spring travel is the same on each coil AND the cushion spring has sufficient downward tension to properly "follow" the vibrator blade. Adjusting that tension is the purpose of the second tool discussed above.
I hope this helps.
Ron the Coilman
Thank you Ron that is what I like to know ,
now I can set my coils the right way whith
my HCCT, as soon as I know how to send pictures
on the Forum I will do that, much more difficult
as working on a Model T !!!!
Thanks Ron. It is getting clearer now.
I still do not have the tension adjusting tool, but I replaced a capacitor this weekend and poured in the tar. After bending the upper bridge like John suggested to get the bow out of it, I set the gap and tested the coil. 16 sparks! I adjusted for 1.3 amps and all looked well.
However, upon closer inspection, I found that the points are not closing squarely. Instead, they are hitting on the back edge, farthest from the adjuster stud. Also, the upper bridge, although straight now, barely goes down the adjusting post far enough to get both nuts on (No upper washer). I believe setting the cushion spring rivet height will help this. I have over .020 travel. This is something I have not messed with, yet. I believe that if I bring this down to .010-.012, like you said above, they may close more squarely and the upper bridge will be farther down when the gap is set correctly. Still experimenting and learning.
Thanks again for all your help,