MTFCA Forum

Timing device

...your title: yeah, pretty much

How does piston movement get transferred to the indicator?

Here is the old school way from back in the day.

Looks like the shaft the indicator is mounted to rises up and down with the piston.

Tourabout wrote: ↑

Sun Dec 04, 2022 4:33 pm

Looks like the shaft the indicator is mounted to rises up and down with the piston.

… except that the piston isn’t straight under the spark plug hole…

use some imagination, Miles

Absolutely not overkill. I like it.

Scott_Conger wrote: ↑

Sun Dec 04, 2022 4:40 pm

use some imagination, Miles

I’d rather just use a plastic drinking straw. Fortunately I live in a state where they’re still allowed….

the amazing thing is, with a micrometer, 6" screwdriver, or a plastic straw, the crank pin is horizontal in every case. That 'ol Henry was a genius.

Here is the manual.

I’m thinking rev2 should have a whistle in the indicator shaft to announce compression!

Rube would be proud!

They were commonly used on aircraft timing.

I didn’t know Rube (my hero) was an aircraft mechanic.

As long as it does not kickback when using the starter, moving the lever on the quadrant will render all the work moot. The pulley pin when horizontal is top dead center from there turn 12-16 degrees to first impulse from the magneto (approx) for stem winders or just after the pistons rolls over TDC and just starts to drop for the rest of us mere mortals with electric starter.
Nice work.

Mark, I’m. Not the sharpest knife in the drawer and my eyes aren’t as good as they used to be so I find “horizontal” sort of an arbitrary value to time an engine by. I built this contraption in an hour or so and the cost was about ten bucks for material. It doesn’t show me approximately where TDC is, but precisely. I was joking about the whistle but found some on eBay for about two bucks each and am going to get some just for fun. The next step will be to get some magnetic strips printed to stick onto the crank pulley so I can align them at TDC, advance the spark fully, and check the “full advance” timing as well. I will have one strip for 3” pulley and another for 3 1/2”. I know it’s not necessary but it keeps me out of the bars and bingo halls.

If you find horizontal (9-3) "arbitrary", you're going to absolutely love 15 degrees ATDC...(9:30-3:30)

That is where your timing is set at.

And don't get your panties in a wad over it being #1. Anytime the hand crank pin is horizontal, SOMEONE is at TDC and it doesn't matter who, as you continue to turn to 15 ATDC. That's where the timer, timer rod bending, and spark lever are all set to. Again...not TDC.

It occurs to me that 15 degrees after TDC can’t be ascertained unless TDC can be confirmed. I’m just not as handy as you are so I need to provide myself with a helper. I guess I’m still a novice having only seven Model T’s for about thirty years, but I’m willing to learn.

David

I'm not trying to be condescending!

For everyone else who may not have lots of experience on model "T"s: On a Model T engine, any time, the crank pin is horizontal, 1 piston is at TDC compression and 1 piston is at TDC exhaust. It doesn't matter which one it is, really. Scootch the engine a bit past TDC to 15 degrees past and SOME coil is going to buzz, and THAT's the cylinder that is just past TDC on compression. And at that setting, if SOMETHING isn't buzzing, then adjust the timer until it JUST does, and adjust your spark rod to make the timer attain that setting. And seriously, it is at 15 degrees past TDC where timing is set...not TDC. Even if you have just one Model T. Or seven.

15 degrees ATDC is the ideal/theoretical setting, but honestly, +/- 4 degrees or so from that setting isn't that big a deal...and is still perfectly safe to hand-crank. And +/- 4 degrees is easily discernable when shooting for 9:30-3:30...it will be obviously one way or the other, or just perfect at 9:30-3:30.

Scott, You don’t have to try to be condescending, it’s a gift. I know exactly what you are saying. By the way, I have twenty or thirty Fordson model F tractors and they time the same way.

David

wow.

with 30 or 40 tractors and 7 Model T's I'm surprised you're having this much trouble establishing what "horizontal" is. I honestly thought I'd be able to offer some help, but it is clear that I cannot, or at least you don't want it. Had I known I'd be bludgeoned with your immense count of vehicles, and the wealth of knowledge that apparently confers, I'd never have offered.

Good Evening.

I made an offset tip for this dial that looks like the offset extensions in Dan Hatch's first photo. I used it to find TDC. Then I continued to turn the crank until the reading went down .087". That is 15 degrees. If you prefer to use the 15.5 degree method, the drop is .093". These measurements will only work with stock crank stroke and rod length.

Twenty years ago Steve Coniff studied this and we wrote an article on the subject of "Model T Ford Ignition System and Spark Timing". See Attached.
When the Model T was first developed the 22.5 degree spacing between magneto current pulses created a bit of a dilemma for being able to start the engine on magneto and creating the appropriate spark advance (notches) for running over various engine speeds.
It is just a theory, but we concluded that the selection of setting the initial timing at 15.5 degrees ATDC was the compromise. If you advanced the spark lever 3-4 notches to start the engine as Ford instructed, you could easily start the engine on magneto with the first spark occurring on a current pulse at 4 degrees ATDC.
Further advancing the spark lever would allow sparks to occur at 18.5 degree BTDC and 41 degrees BTDC.
Take a look at figure 8 and think about it a bit?
Subsequently Tony Wiltshire created his clever initial timing adjusting tool which is not materially different the one in Browning's initial post.
Ron Patterson

You asked if it was over kill, we gave our opinions.

I'd think free play, friction, and flex in the timer linkage, along with play in the timer mechanism, would stymie any attempt to get a truly precise initial setting. Timing gear lash could affect precision setting. I bring mine to TDC as indicated by the crank ratchet pin, then engage the crank and move the engine in the normal direction of rotation until the crankpin is at about 3:30. That seems to work well when starting on battery or magneto, hot or cold. I set the spark lever at full retard, or a notch or two down, when using the starter, and I set it about 1/4 way down when starting on magneto.

In a properly restored Model T all those mysterious variables will not exist or significantly affect spark timing.
The balance is simply another way to accomplish the proper initial timing adjustment we wrote about in the article.
When any piston is set at 15 degrees ATDC the crank pins will be pointing exactly at 9:30 and 3.30 on the clock face.
When starting the engine on battery and the spark fully retarded the first spark will occur at 15 degrees ATDC followed by a constant stream of sparks controlled by the natural rhythm of the coil (approximately 400 cps) operating on battery so long as the timer is still in contact.
Conversely, when starting the engine on magneto with the spark lever advanced 3-4 notches the first spark will occur at 4 degrees ATDC followed by sparks occurring every 22.5 degrees of crankshaft travel.
See the first paragraph on our article
Ron Patterson

When running on magneto, the position of the timer is not important for the precision of the ignition point as that is set by the position of the coils in the coilring. The timer just selects which 1 of the 16 ignition points are used to ignite the cylinder ready for that. So the play in the linkage are not that important to get a proper precise ignistion.
Running on battery is another story.