To start the '15 roadster I choke it a couple of pulls, turn the switch to BAT, and it starts on the first pull. When I try to start on MAG, absolutely nothing happens. I tried the 1156 test, and at the slowest idle I could manage without killing the engine I got 7 to 9 volts. A little faster idle, making the bulb bright, got 12 volts. A fast idle got 17 volts. The car seems to run about the same on BAT or MAG. I did observe that none of these idles was particularly smooth. Any suggestions?
Start on battery and run on mag. Mine is the same and it seams to run fine on mag once I switch it over. Over 38 it wants to sputter, but that could be carb adjustment. (I have an Schebler OF so it's set it and leave it)
This assumes you are using known good coils.
Give it two pulls with choke, turn switch to mag, advance the spark lever 3-4 notches (on mag only) and give it a hard upward pull creating as much speed as possible.
Ron the Coilman
Ron, I'll try that again when the new coils arrive. The ones that are in there now are the coils I robbed out of the touring. I think they're OK, but I'll try it with the new ones and go from there. Meanwhile, I'm going to check timer and plugs to see if cleaning/setting will smooth out the running.
By the way, starting on BAT and running on MAG is OK with me if I have to do it, but it just bugs me that a brass era car that's supposed to start without a battery won't. I'm not a total purist, but I'm enough of one that I'd prefer not have to "cheat" with a battery in the trunk.
You must advance the spark in order to start on mag---(full retard on Batt starts) Paul
Study this diagram and it will help explain.
Magneto Fig8.pdf (48.5 k)
That should read: 15.5 degrees ATDC as Ford recommended.........
As to the Batt. terminals that appeared on the boxes: There were some things the Old Man wouldn't admit to if you paid him.
Here's a downloadable instruction manual from 1912. Magneto starting is discussed on page 11.
Let me see if I can put into words what this is about in a simple explanation of why a properly timed T will not start on magneto unless you advance the lever about 4 clicks. There is a pulse from the magnet that occurs at 4 degrees AFTER top dead center. That is the pulse you need to fire your coils to start on magneto. With lever in full retard the timer contact will go "open" about 9 or 10 degrees before that pulse shows up to fire the coils so crank as hard as you can and you still will not get that spark to fire your plugs because the timer is not connected when that 4 degree pulse shows up. Advance the lever about 4 clicks and the timer will then be "on contact" at the time that the 4 degree magneto pulse shows up and you will get that spark. Remember that the locations of -4, 18.5, 40...are locked because they are determined by the magnet locations on the flywheel. They don't move so there is no danger in advancing the spark a few clicks when the switch is in the Magneto position.
Hope this helps.
can you show a picture of where the spark rod should be in the proper position for Mag starting, as mine has only ever started on mag ONCE since I've been starting it in the last 2 years.
Garnet, that link just opens this thread again.
Sorry about that - a dumbzeihmer's moment on my part:
If that still doesn't work, just go to the home page and search for Instruction Book for Ford Model T Cars
@Garnet: Worked for me. Thx.
With fresh Champion X plugs installed (gap .025) and new Patterson coils in the box, I tried MAG starting again. Over the weekend I cleaned the timer and set the timing. In trying to start today I set the spark in several positions, from fully retarded to advanced down a couple of inches. Zilch. Nada. Muerto. Not even a cough. Running the 1156 test on BAT, a low idle as slow as I could manage without killing it, and the bulb dim, produced 7 - 9 volts. At a medium idle with the bulb bright I got 14 volts. Running fast, with the bulb really bright, produced 19 volts. Switching over, the car seems to run at least as well on MAG as on BAT. The only thing I know I haven't done is clean the mag post, so I'll try that next. Any other ideas?
Are you sure you are turning over fast enough to generate power for the coils?
Of course the question becomes, how fast is fast enough? You seem to has a good speed in your videos but there should be a way to measure the RPM's at the point it is needed when the magnets pass the coils on the mag plate. You probably could take a video or use an existing video and view it frame buy frame in your video editor, then calculate the speed. Then I could do the same thing on a good mag start video and compare the results.
You can see a mag start in the first 1/2 minute of:
I have never measured the voltage output of my mag.
This is perplexing?
I agree with Jim T. A good hard yank (video) and that will fire the coil on magneto. If it will run when started on battery and switched to magneto with the readings you obtained cleaning the mag post is pretty far afield.
Tell us about the procedure you used for setting the initial timing?
Have you ever checked the compression on this engine?
I am also concerned that when switching from battery to magneto at a fast idle you do not notice a noticable increase in engine RPM.
There must be something else wrong and we are missing it?
Ron the Coilman
Yep, I agree the mag post idea was pretty much grasping at straws because I couldn't think of anything else. The voltage readings I got suggest that's a blind alley.
My timing procedure (ala Jerry VanOoteghem) was as follows:
"1. Remove #1 spark plug.
2. With ignition off, hand crank engine, (or have a helper do it), with your thumb over the #1 plug hole. Feel for a pressure build up, indicating that you're on the compression stroke.
3. As soon as you feel pressure building, stop the cranking.
4. By looking into the plug hole, you should be able to just see into the cylinder bore. While you're looking into the bore, have your helper continue to crank slowly until you see the piston come up to its highest point. Stop cranking.
5. Look at the position of the pin in your crankshaft pulley. You may need a small mirror. The pin should be exactly horizontal. If it's a little off, either crank more or, if you've gone too far already, put the transmission in high gear and rock the car back to nudge the engine as needed.
6. You are now at Top-Dead-Center, compression on #1 cylinder.
7. Install your new timer and position it at least close to where the timer rod would fit when the spark lever is all the way up. Do not install the timer rod yet.
8. Connect the #1 sparkplug to its plug wire and lay the plug on the head.
9. Turn on the battery ignition. Don't be alarmed if #1 plug is firing.
10. If #1 is firing, turn the timer, by hand, counter clockwise, (as viewed when standing in front of the car), until the firing stops. If it's not firing, skip to the next step.
11. By hand, slowly turn the timer clockwise until #1 just begins to fire. Stop turning at that point. Shut off the ignition.
12. Set the spark lever about a 1/2" down from the top, (or from the fully retarded position).
13. Adjust your timer rod so that with the timer positioned as described above AND with the spark lever in the 1/2" position, you are able to attach it to the timer. Be careful not to move the spark lever or the timer in this process. The timer rod will likely be too long or too short to fit and will have to be bent accordingly until it fits. Once adjusted correctly, install the rod and cotter pin it.
What you have now is an engine timed to fire at TDC with the spark control 1/2" down. This guarantees that when the spark is all the way up, the timing is retarded and is therefore safe for cranking.
14. Test your work. With the linkage all assembled, move the spark lever all the way up & turn on the battery ignition. There should be no spark at this point. Slowly move the spark lever down until #1 plug just begins to fire. Your lever should be very near the 1/2" setting. If so, re-install the #1 plug and test run the engine. If not, re-adjust the timer rod and look for sloppy, loose components in the timing linkage and correct those problems."
No, I haven't checked compression. I'll do that and see what I find.
The problem is probably some little detail we're all overlooking. I'll just have to keep trying different things until I find it.
Since this is a '15 roadster you can look easily below the radiator and see into the crankshaft pulley. Humor me and do this. Set the lever to full retard and turn the ignition switch to BAT. Pull the hand crank handle ever so slowly and STOP immediately when you hear a coil buzzing. I dont' care which one. If you think you pulled it passed the point where it started buzzing then just pull forward some more but ever so slowly and sneak up on the exact point where a plug starts buzzing. STOP there. Pull the crank handle back out of the pulley and look at the crank pulley pin. Pretending the pulley is a clock face, is the pin horizontal at 9 o'clock to 3 o'clock or is it higher up on the right side like from 8 o'clock to 2 o'clock position. Or is it lower on the right as in 10 o'clock to 4 o'clock position?
Are you using an accurate digital meter for your magneto tests or did you use an analog type (with a needle)? I see a problem that nobody else has noticed.
I just checked the pin. It's exactly horizontal. The meter is analog. What does that tell us?
I had trouble starting on mag, until the " first" time. It seems to take a bit of confidence, a little advance, and a quick (this where confidence applies) pull.
Try it with a warm engine the first few times. Once it starts on mag a few times, it seems like it works better (probably because I am less afraid to pull hard with the spark advanced.
Assuming you are measuring the 1/2" spark lever setting at the steering quadrant and not at the end of the lever, then about 1/2" = 5 notches and when full retarded would equal about 14 1/4 degrees ATDC. This would be close to the 15.5 ATDC position recommended by some and it would follow that the best position for starting with the mag should be about the same setting or 5 notches down from fully retarded position.
Now, your most recent post you said that the the pin is horizontal when it begins to fire. This would indicate that your timing is set very close to TDC in the fully retarded position and it should start on the mag in the fully retarded position.
I set my timing just past TDC when fully retarded and it starts well on the mag or battery when the lever is in the fully retarded position. I don't have to remember to change the spark setting depending on how I'm starting, just set it all the way up and start it. It saves another opportunity for operator error.
It means your timing is advanced too much and could be hazardous to your arm when starting on battery but also your attempts on starting on magneto now would be even more difficult if you are advancing the lever based on instruction book which assumes your timing is at 15 degrees retarded. Normally the timing if set correct would result in initial timing being set at about 15 degrees retarded (3:15 O'clock on the right hand end of the pin). 4 clicks advanced from there would put you at about 3.6 degrees retarded which would be just barely enough to start on magneto but 5 clicks would put you at about 1 degree retarded which would be fine for magneto starting but with your setup - if you advanced 4 clicks then you would be at about 11.4 degrees advanced. I would reset your timing the easy way and just use the pin. You don't need to measure piston drop nor mess with any of that to set T timing on a brass T since the pin is clearly visible and is way more exact than trying to determine piston position. Every time the pin is exactly horizontal, a piston is exactly at Top Dead Center. Has to be that way since the pulley pin hole is the reference for the throw angles of the crankshaft and the pulley pin hole is the 000.0 Angle reference.
I think the reason you cannot start on magneto is 2 fold. Your timing is off but not far enough off with zero lever setting to prevent magneto starting. I would reset the timer based on ARM safety when starting on bat. The main problem is that your magneto is weak. I base that on the 19 volts that you measured "Running fast with bulb real bright". On my T I can burn out that bulb rather easily and any decent magneto during the same test will produce well into the 20-30 volt range rather easily at high RPM. What you need to understand about starting on magneto is that it is the speed of the magnet passing the coil that induces the current. Slow magnet speed produces not much current but if the magneto gap is large or magnets are weak, you don't get much current even with fast speed and that is what the higher RPM low voltage readings are telling you. Also Ron Patterson noted that you don't seem to notice much difference when you flip to magneto from battery after starting. Usually the higher voltage of the magneto will produce an instant timing advance when you switch to mag from bat. Yours seem to be "so so" - again pointing to a weak mag. To start on magneto you do have to have a healthy magneto but then it is in fact pretty easy.
Hope this helps. Please humor me again and reset your timing to the safer 15 degree retarded point since you do have a stem winder and your present setting is not a good safe place for it.
I respectfully disagree with Jerry's method since it seems not to have produced the correct setting and to my mind is just way too complicated. I think Jerry is a democrat but then maybe not because he seems like a very nice guy when I have met him and I am probably going to catch some heat from him in a couple of weeks for tweeking him here - grin. I am looking forward to renewing old friendships at the MTFCI tour in a couple weeks.
In truth I don't really care what method is used to set the timing only that you end up with it set correctly. I stood right next to Frank Woodin when he got his arm broke and I ended up taking him to a couple of hospitals since I was tour chairperson on that tour. I was just about to say to him that "it sounds like your timing is not right" when it bit him. I don't ever want to see that happen again to anyone including you, me and Jerry too.
Don't worry too much about Steve's safety, he has the art of safety hand crank starting a Model T perfected to a T and has a video to prove it.
I would bet that Mr. Woodin was not using the correct method of hand cranking when he broke his arm.
I do agree that any person cranking a T should know exactly how it is timed and it should never ever be timed so that it is anything BTDC when the spark is fully retarded.
The question I had is how fast do you need to crank it to start on the mag? So I videoed several attempted starts with some starting and some not. Then using the known video frame rate of 30/sec and measuring the angle of crank rotation from one frame to the next I calculated the speed of each no start and each start. I got this:
19.5 degrees in one frame = 97.5 RPM NO start
20.5 degrees in one frame = 102.5 RPM NO start
23 degrees in one frame = 115 RPM Start
24 degrees in one frame = 120 RPM Start
25 degrees in one frame = 125 RPM Start
28.5 degrees in one frame = 142.5 RPM Start
So it looks like at least on mt T that anything at about 115 RPM and higher works for mag starting. I'm sure that other cars will preform differently.
The photo is just a single frame of the video.
You might want to gap your plugs at 0.030 the recommended gap by Ford.
I run my plugs at that gap without problems.
You cannot test one T and make the sweeping conclusion that 115 RPM will work on all of them. I hate to keep harping on this subject but TIMING is everything. I almost hate to keep going here since I am already getting hate emails from this thread ha ha.
The ONLY pulse you can start your model T with by hand cranking is the 4 degree retarded pulse as identified by posted timing diagram. That one ONLY! Why? Because even it you are a very strong man, you will not be able to get up the momentary instantaneous speed of a few milliseconds to quickly pass the magneto coil winding by a fast moving magnet when you are pulling AGAINST compression. Thus advanced timing of the other firing positions prevent their being used for starting. BUT.... when you pass through TDC suddenly you get HELP big time from the compression itself now pushing down along with your arm strength. This is how you get the sudden acceleration necessary to induce the coil current high enough to get you that spark. You simply must have the timer in the right position so that the 4 degree mag pulse is connected to the appropriate coil when you jerk that hand crank. I personally believe the main reason for the magnet placement on the flywheel at the retarded position was ALL about getting that one pulse at 4 degrees so the T would start easily by aid of compression thus increasing magnet speed a ton for an instant. If that pulse were moved to 4 degrees advanced you would never get it to spark since hand crank speed would probably be too slow regardless of your strength unless the engine had little or no compression. I have seen an 80 year old lady (Mirriam) from Alabama who could hand crank start her T and it was mainly because of this cranking speed assistance given by the engine compression once she got the thing past TDC.
Does this help make it clearer?
As an electronically-challenged individual, I appreciate efforts by John, Ron, and others who get it to explain to me what I'm doing. It's not your fault if I'm too thick-headed to get it all on the first, second, or third reading. I'll keep plugging away until I do. Don't give up on me.
I have the two articles, that Ron regularly posts links to here, printed out and stapled together. I periodically re-read them. I get it while I'm reading it, but have a hard time explaining it to anyone else. Then I find when I re-read them, I always learn something new. Maybe one day, it will all sink in and stay there. But then again.....maybe not.
We agree about the cranking speed, like I said, "I'm sure that other cars will preform differently". It was just something that I have never seen measured and was a fun exercise, both physically and mentally. Those same coils on my HCCT will put out a consistent spark at less then 60 rpm but apparently not in the car under real conditions. I need to measure my mag voltage to get an idea how it compares to other cars. All I know know is that it starts well on the mag and I have a significant increase in speed when switching from 6V to mag.
I agree that the timing is the key to good starting on a mag. I also understand what your are saying about rocking over center to get a little speed boost from the compression. However at only 4 degrees after TDC the piston only has traveled down less then 0.002" from it's highest point. Probably not enough of a mechanical advantage to increase the cranking speed significantly. Now at the 26.5 degree mag spark point I would expect to see a increase in speed due to the compression but that is getting kind of late.
The timing method Steve referenced was purposely made "complicated" so as to cover every last detail, (that I could think of), for newbies, (or Democrats).
It should have produced the correct setting as it calls for a spark, with the crank pin horizontal and the spark lever 1/2" down. Steve's spark was with the lever fully retarded. (Perhaps Steve is a Republican?)
This all assumes however that there is very little slop in the timer control linkage. I see in another post that Steve had some slop in the spark rod lever. That would have botched up my timing procedure and likely did. (Looks like Steve fixed the original instead of buying a new one. Democrat?)
Looking forward to seeing you in MN John. We can discuss politics there. ;>)
(To those who haven't followed the entire message string and John's earlier comment/ribbing towards me, the "political" comments are in response to him. Please take no offense)
I agree Jerry that likely politics isn't affecting the settings here ha ha. I also agree that slop in the linkage can affect it a bunch. Method used is not important but final result is very important. If one pulls the timing lever down and then slams it back to full retard it can "toss" the timer to a more retarded position than "normal" and this can be dangerous if that is the position it is in when setting the timing. Later if one then has the wife retard the lever they pull it up slow leaving the slack in the timer such that the timer is now at its most "advanced" position. On some T's this can be enough more advanced to bite the person starting the car. I always tell folks when checking their timing to pull the lever down and then put it back up slowly to the top. This leaves the timer in the most fully advanced position and thus if the timing then shows 15 degree retarded pin position (9:15-3:15) then all is perfection. Unfortunately if there is linkage slop then setting for zero at 4 clicks is not going to be a repeatable situation. If the timing wasn't so important for arm safety it would not matter that much. The problem is that black era cars with aprons under the radiator make it difficult to see the crank pin. Brass era cars are easier. When possible - the best time to set the timing on any T is when the radiator is off the car. Contrary to what is often posted, I don't find that much difference from timer to timer and I have used New Day and Anderson interchangeably without finding the timing affected enough to warrant having to rebend the rod. Perhaps I was lucky. I don't change timers very often. I do however pull the crank ahead 4 times after final timing to verify that I get the same pin position 4 times in a row thus testing all 4 timing positions. This verifies timing cover centering and also any possible bent or miss located contacts in the timer.
You mentioned an error I saw in an older thread. You said that the 15 degree setting is the same as the 9:15-3:15 pin position. Actually the 15 degree setting should be 9:30-3:30 positions. If you set the pin at 3:15 and 9:15 then the timing would be 7.5 degrees ATDC.
30 minutes on the clock is equal to 15 degrees.
Jerry, my course of action in l'affaire du slop was totally apolitical. It was ethnic (Scotch).
yeah but my clock is metric ha ha.
Actually I tell folks to set it so that the pin is noticeably down on the right side since it is really about safety and there is plenty of travel in the lever to get one all the advance that is necessary. You are correct of course. Either setting (3:15 or 3:30) is fine by me but I do get worried when it is set exactly at TDC and NO the time setting does not change with daylight savings time ha ha.
On a separate note - doctor I know said that even today the break of the arm bone at the usual place it breaks from hand crank is called in medicine a "chauffeur's break".
Some people rebuild there crank handle and weld a new shaft on it . One time I had an engine here who was nearly impossible to start with the crank .Then it came out that they drild the hole for the rachet on the wrong place. Now my question : what is the best crank handle position in relation with the crank [pully] pin .
THANKS for your answer !!
I understand completely Steve. I'm Belgian
Your question is relevant to this thread and the simple answer is that when the pin is horizontal the crank handle is 30 degrees counter clockwise from vertical or horizontal. There are four possible positions that the handle can be when the pin is horizontal but if you are cranking correctly and pulling with the left hand the crank needs to pass the TDC position when it is at the 11:00 o'clock position. Now it is possible to pull the crank from the 8:00 o'clock to the 2:00 o'clock position without passing TDC and there is little chance it would start. So to have a good chance of starting on the mag it is important to start the pull with the crank handle near the 8:00 o'clock position with the crank pin in the vertical position. It also makes sense that if you can start the power pull as far down as possible you will be better off. That is if you can start pulling near 7:00 o'clock, then you have more of a chance to get the engine up to the required speed to fire the mag/coils by the time you get to the 11:00 o'clock TDC position.
Here is a photo with the crank pin horizontal:
And the pin in the hand crank shaft should be abut 70 degrees from the crank handle, as:
I did finally check my mag output voltage. When running on the mag and using an Triplett antilog meter I measured a minimum of 14 volts at a slow idle and 33 volts at a fast speed. This is a little more then you measured on yours so it may follow that you may have to spin your engine faster then I need to spin mine to get it to fire on the mag.
What is the condition of your magnets? Maybe a in car magnet boost would help out.
Because of when the power pulse is available and the needed position of the timer to catch it what would be the possiability of a kick back with a mag start?? Both T's will easly mag start once i learned about the needed advance on this forum and i have never experanced any sort of kick this way.Sounds scary till you have done it.Bud.
Starting on magneto is almost impossible on any pulse from the magneto other than the one at 4 degrees retarded. That is because of the boost in cranking speed that you get on the "down side" due to compression aiding you instead of fighting you. If you want to prove it out one way or the other, pull the plug wires off of the plugs and leave the plugs in the motor while propping the wires close to ground. Advance the lever to the 18 degree timing position and crank away while watching the spark plug wires. I doubt you will be able to get enough speed on the "upside" against compression to generate a 1/8" spark distance via the magneto and coil. If your motor has really weak compression then it might be possible to generate such a spark but I doubt you can. I am not that strong myself so I know I can't do it. Make sure your timing lever precludes the spark being the 4 degree retarded magneto pulse since that one is easy.
It would be possible to it to fire before TDC but when starting on the mag there is quite a safely margin. Once you advance the spark lever 3 to 5 notches to pick up the 4 degrees ATDC mag spark you would have to advance it another 22.5 degrees or about eight notches to pick up the next mag spark. And unlike starting on the battery, not only would you have to advance about 11 to 13 total notches but also have to be turning the motor over fast enough to fire the mag at that point.
Depending no how your car is timed, you could get a bone breaking kick back when on battery power with spark advance of just a few notches and slowly turning the motor over. In fact you could get a kick back on battery power without tuning the engine at all under the right (wrong) conditions, kind of a backwards free start. The bottom line is you would have to work harder to get it to kick back on mag power then battery power. I wonder if it has happened before? Probably has.
Jim: Thank you that is what we NEED !!!!
What is needed with all the right info is for people to get in front of their Ford at [The place of learning]!! I wonder the percentage of T owners who will not crank their T's from fear?? Thanks guys! Bud.
Several years ago, I saw a post (I'm almost possitive it was on this forum) from someone who actually proposed the crank be removed from the car or at the very least used only as a conversation piece. THAT person needs a Model A with an auto advance distributor.
At the Colorado-Wyoming tour 2 years ago, one of the participants blew his starter and had taken the crank off. This was after several other problems, and he left the tour before the final day and trip over Trails Ridge Road. If I had known earlier of his problems, I would have loaned him my crank to start his car. Even if you don't use it, I suggest leaving the crank on the car.
Don't get in a hurry! Just last weekend, I stalled the car backing up and jumped out to crank start it, forgetting to retard the spark. I didn't get hit, but called myself several stupid names!
Will it start on mag now that the compression is up?
Let me see if I understand this properly. There are two methods of hand cranking the Model T.
First is on battery. In this case, the timing should be fully retarded. The spark lever is fully up and the spark starts at about 15 ATDC. This will ensure the spark will not occur before top dead center and thus prevent kickback and a broken arm.
Second is on magneto. In this case, the spark lever should be pulled down 3-5 notches which is 8.55 to 14.25 degrees. (2.85 degrees per notch.) With initial timing of 15.5 ATDC, this advances the spark enough so the timer turns on at 6.95 to 1.25 ATDC. I see where the 5 notches allows the magneto pulse at 4 ATDC to fire and start the engine, but not the 3 notches of advance. But at 5 notches, since the spark is at 4 ATDC it will prevent kick back and a broken arm.
I believe this makes sense to me, but two questions. First, since one cannot get the engine cranking fast enough to get a spark on the compression stroke (BTDC), would it really matter if the spark lever was advanced more, even all the way, since the only one that will work is the 4 ATDC. Any BTDC pulse would not fire (too slow cranking speed.) And so since no pulses BTDC will fire, one cannot get a broken arm while hand cranking on magneto regardless of spark lever position. Second, wouldn’t one want the lever advanced far enough before the 4 ATDC magneto pulse so the coil had plenty of time to saturate, and not just “catching” the 4 ATDC pulse, so wouldn’t 10 or so notches be much better, since even at 5 notches, that only provides 2.75 degrees of rotation to saturate?
Good question. I would not say that say that it is not possible to crank fast enough to get it to spark BTDC on the mag. Assuming that everyone cranks correctly by pulling with the left hand and that the normal pull is from 8:00 o'clock to 2:00 with the TDC point at 11:00. Then if the pull was started at 180 degree BTDC rather then the normal 90 degrees BTDC, the 41 degree BTDC mag pulse would be at about 12:30 and the 18.5 degree BTDC pulse would be about 1:30. It would be very easy to get it up to speed to fire at the 41 degree or 18.5 degree BTDC positions.
The bottom line as long as you pull with the left hand, you should be good in any case. Of course some strong arm will come up and spin the engine at 200 rpm with the right hand and all bets are off.
Now if you set your timing as I do and as a few recommend, it should start on battery or mag just fine with the spark in the fully retarded position. My timing is set just past TDC, maybe a degree or two. On one hand there is less of a safety factor but on the other there should be no confusion about the need to advance 3 to 5 notches when starting. "Now was that 5 notches of advance to start on battery or mag?"
I don't know haw many degrees before the maximum mag pulse it takes to get the maximum spark.
Wow, just a degree or two past TDC. I hope you don't have any slop in the linkage anywhere.
Don't be scared,it works!! Unless its free every start is stem wind for me.Bud.
Tom and Jim have some good points. Not to put anyone on the spot, but I'd like Ron or John's thoughts on this. I, too, think it is possible to crank fast enough to get a spark BTDC on mag, so I'm not about to try advancing it all the way to find out. Especially since I crank with my right hand. I seldom try to start on mag, but sometimes I do. I have better luck with a warm engine. Battery just seems easier, so that's how I normally do it.
Here is a little more info.
From the 1917 Ford manual, instructions on starting on the mag it states that "Care should be taken not to advance the spark too far, as it may "back kick"". So, at least Ford thought it was possible for it to bite you if advanced too far.
Also from another thread John R. said, "If your timer is set incorrectly to advanced position and you have the switch set to battery then you will get a kickback but with the switch set to mag you won't unless you have something really screwed up with your setup." I guess having the spark fully advanced when starting on the mag would qualify as "something really screwed up".
I believe Ford recommended setting the initial timing at 15 degrees ATDC (the 2 & 1/2 inch rule) was for safety reasons.
I agree with John Regan. The only "reliable" way you could start the engine on magneto was to advance the magnets on the flywheel by 7 degrees. Hence you could take advantage of the speed of the downward moving piston and the spark occurring 4 degrees ATDC.
You could not rely on starting with the spark later and anything earlier was potentially dangerous.
Additionally, the engine ran well under most (Model T era) conditions with spark occurring at about 18 or 41 Degrees BTDC.
Ron the Coilman
The brass steering gear quadrant has a range of 20 notches eg Lang's 3509 Steering gear quadrant, solid polished brass.
If the timing range on the crankshaft is 80°, does it then follow that each notch on the quadrant represents 4° on the crankshaft?
That would make sense to me. The standard steel spark quadrant has 28 notches and assuming the full range of timing adjustment is 80 crankshaft degrees this give 80 divided by 28 = 2.85 degrees per notch. Then for a 20 notch spark quadrant it would be 80/20 = 4 degrees per notch.
Of course this is an average and not a linear change because when the differences in the length of the spark level arm, the radius of the timer and the orientation of these to the timer control rod.
Two thoughts. One is that as Jim points out - the lever position using notches or "click count" does not provide a linear relationship to amount of timer rotation in degrees. The 4-5 click position has demonstrated enough advance to "catch" the 4 degree ATDC mag pulse for magneto starting on a typical T that is timed reasonably correctly. Second thought is that advancing the lever further or "all the way" and assuming that the T will start only on the 4 degree ATDC pulse anyway assumes the timer has infinite closing dwell contact time to catch all of the magneto pulses that ever occur. Remember that as you move the timer lever you are moving a "window" of timer contact dwell time that must encompass the 4 degree ATDC pulse whose time is absolutely fixed by flywheel magnet position and engine block magneto coil position. For any pulse from the magneto to fire a coil, the timer must be connected to a coil at the time the pulse occurs. The 4-5 click positioning of the lever usually places this dwell window to be straddling the 4 degree ATDC pulse.
Upon rethinking my post above I suspect I didn't help clarify since in fact the timer does encompass likely all of the meaningful pulses from the magneto at -4,18.5, and 40. I tend to focus on the leading spark since it alone actually ignites the cylinder and the trailing sparks from the other magneto pulses don't do anything after the ignition event has occurred. The material point is that the 4-5 click position sets the timer to catch the correct mag pulse to start the car. That is the simple point at which I should have stopped any further explanation ha ha. I am getting too old and my brain is already on tour. We are leaving for the MTFCI tour in about an hour.
Thanks Jim & John.
Good to find out about the steel quadrant and its [range of?] 28 notches (average 2.85° per notch).
I have just now read this thread for the first time. A lot of really good information. Two things, though. One a point I have not seen. One, a clarification.
Steve Jelf, et al,
How level was the car situated when you made your voltage measurements? The gap on the magneto is critical. MOST model Ts have more end-play in the crankshaft than they should. I measured one with over fifteen thousandths one time. Due to clutch pressures, slightly tapered bushings and bearings and a few other things, crankshafts tend to float either forward or backward when the engine is running. But when you are cranking the engine, you are pushing the crank in and therefore the crankshaft back. This widens the magneto gap to maximum. If your engine tends to float forward, you may be taking readings when it is at it's best. When you are cranking it, it will be at it's worst. For this reason, when you take those "idle-voltage measurements", park the car facing up on a slope. Gravity will tend to float the crankshaft backward (widening the gap) and give you a measurement more like what you have when hand-cranking.
Second. The burst of cranking speed is not all about compression pushing down and giving an assist.
When the traveling piston is halfway up the cylinder, it is moving at it's fastest in relation to crankshaft degrees of rotation. Both physical drag and rising compression are resisting that travel with their greatest leverage. When the piston nears the top of the cylinder, Both the increasing compression and the physical drag go to nearly zero. This is occurring at about 10 degrees before top dead center. The sudden loss of resistance versus your powerful pull results in a short burst of speed. (Basic fluid dynamics. Pressure vs resistance equals volume/speed.)
Why is this important? Maybe it isn't. Except to understand that the compression push assist occurs about the same 10 degrees after top dead center, or about 20 degrees rotation later. Those 20 degrees give you the time for the crankshaft speed to accelerate. That acceleration may give just the burst of power to the coil to fire the cylinder.
This forum is one of the best sources of basic and advanced physics and electronics since growing up around my grandfathers ranch (farm) and my fathers TV repair shop. Thank you Ron P., John R., and others. I learn more here than anywhere else these days. (College mostly taught me fancier ways to say what I already knew.)
Drive carefully, (John, have a great time on the tour!) and enjoy, W2
If the emergency brake is set the magneto gap will be at it's greatest limited only by the rear main bearing thrust surface.
Ron the Coilman
I presume the attached rods are the same distance apart in both early and late 3530 spark rod levers?
Word Lead (rather than Spark) used in 1917 UK booklet.