Laser timing pointer

[RobertGary1]

I need to replace my timing pointer. There used to be a company that made a cool laser pointer that mounted to the case and shown against the rear timing marks. I think they went out of business but it seems like if you could find the right type of mount it would be easy to put such a pointer together.

However, I'm not finding a mount that seems to work? Has anyone mount a suitable mount for a laser pointer?

-Robert

[Guest]

If you can't get to the marks on the starter nose case, a six inch steel ruler on the top crankcase seam behind the starter ring gear is just as easy.

Clarence

[takair]

Or a hacksaw blade.  They flex to lay on top of both the case and the ring gear.  I make a mark on the front of the ring gear corresponding to the timing mark on the back.  Don't even need to pull the top cowl or dog house cover.

[N201MKTurbo]

I've had the same hack saw blade in my toolbox for 30 years. I ground one end to a pointer and bent it down to the perfect position. I hold it in position with masking tape. 

If I had a laser pointer, I would verify its accuracy with the hack saw blade.

Edited October 10, 2015 by N201MKTurbo

[mike_elliott]

If you want to do it right, get this.

http://www.ritesystem.net/

 

[RobertGary1]

If you want to do it right, get this.

http://www.ritesystem.net/

 

I'm not sure I could adjust the timing to 0.01 degree of accuracy  seems a bit extreme. 

-Robert

[mike_elliott]

It beats winging it being sorta close, guessing where the mark one eyeball says 20 or 25 btdc is based on the alignment of a hacksaw blade. Yes you can time it accurately with this tool. Do you know of any reason not to?

[Guest]

If you want to do it right, get this.

http://www.ritesystem.net/

 

These are useful when adjusting the timing on a TCM engine, with one limitation.  The cup is held to the prop spinner with 3 rubber bungee cords which are susceptible to being bumped or shifted by accident.

Lycomings index marks on the back of the ring gear and a straight edge are simple and fool proof.

Clarence

[slowflyin]

I use a dial indicator like this one.  I've used a straight edge many times as well.  Mike B had a timing article and it somehow convinced me you never really know where TDC is without this method.  Not sure it's any better but it works well.

 

[slowflyin]

Here's the article if anyone is interested.

http://www.avweb.com/news/maint/184370-1.html

[jetdriven]

I use a dial indicator like this one.  I've used a straight edge many times as well.  Mike B had a timing article and it somehow convinced me you never really know where TDC is without this method.  Not sure it's any better but it works well.

 

it's accurate to +/- 2 degrees or so.  Just use the time rite. It's not really much more expensive either. 

Edited October 11, 2015 by jetdriven

[MB65E]

I've had the same hack saw blade in my toolbox for 30 years. I ground one end to a pointer and bent it down to the perfect position. I hold it in position with masking tape. 

If I had a laser pointer, I would verify its accuracy with the hack saw blade.

Hack Saw blade = Laser Accuracy 

-Matt

[DaV8or]

If you want to do it right, get this.

http://www.ritesystem.net/

 

That's what I got when I put my mags back in. It works as advertised. I'm really happy with it.

[RobertGary1]

I wonder how much precise timing produces noticeable benefits. We know that Lycoming changed our data plates from 25degrees to 20degrees not based on any change in how they build io-360's (some ignore the data plate and just use the old value). If they could change it 5 degrees on little more than a whim without a change in performance specs I wonder how important it is. 

 

-Robert

[carusoam]

Using precision... Really, using accurate measuring devices...

The 25° produces more power at the cost of some higher CHTs and moving closer to the limits defined by detonation.  This timing is acceptable to some engines and best uses 100LL in combination with knowing your CHTs at all times...

The 20° produces less power and lower CHTs.  It is more accommodating to not having engine instrumentation or using fuels with lesser quality than 100LL

Not using precision... Using tools with less accuracy

The mechanic would add to the risk of detonation by accidentally retarding the timing too much.  Or minimize the power that is available by advancing the timing too much.  And he doesn't really know where it is actually set...

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It is possible for a mechanic to set timing accurately with old style mechanical devices.

It is possible to set magneto timing using less of the mechanic's time with high tech devices.  Akin to using accurate and precise tools.

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It is best to not use imprecision or inaccuracy when setting magneto timing.

Getting 26° when thinking you were getting 25.00° would not be beneficial.

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There is always a discussion of the differences of precision vs. accuracy in engineering 101.  Precision is a digital display that has a reading out into the decimal places.  Even the shop helper can read the gauge exactly.  Unfortunately a digital display doesn't tell much about the accuracy that it is displaying.  Beware of cheep tools with nice displays. They may be precise, but may not be accurate. (Not implying any of the above tools are cheap, or inaccurate)

--------

Going to to a Mooney fly-in is like having the benefits of sleeping at a Holiday Inn.  

All of this information comes from endless reading of MooneySpace. I am not a mechanic. Just a PP.  I think Byron and Ross have produced some of the most interesting reading related to ignition timing and what happens inside the cylinder.

Best regards,

-a-

 

 

Edited October 11, 2015 by carusoam

[RobertGary1]

Agreed but if Lycoming changed the spec by 5 degrees for a small change in operational characteristics that did not even necessitate a change in operating or performance instructions what's the benefit of a mechanic adjusting with 1 degree of precision vs 0.01. I'm not actually arguing either way but asking. 

 

-Robert

[carusoam]

I think the benefits are in a very narrow range of 'known' settings.  The engine manufacturers defined their work by what they 'knew'.  The settings they selected and the results that they measured.

We have gobs of data including thousands of Mooneys flying in all environments around the world.

We have very little data about flying Mooneys outside the known settings.

We do know that detonation is a real challenge at one end of the spectrum and lack of power happens at the other end of the spectrum.

It is good to stay within the known limits to avoid being a test pilot.  Staying with the appropriate limitations is the cool part of owning a factory built airplane.  There is a lot of comfort while flying, knowing how well the known equipment operates.  Even then, there are plenty of things that can go awry.

Removing all the knowns, leads to having to be really knowledgable about the systems and being on top of all the stuff that could go wrong. Do we really know when detonation begins?  We really know how to void it based on known timing and known CHTs...

The older I get, the more locked into the knowns I become.  When I was young, I couldn't afford melting a piston. Now that I'm older, I wouldn't want to land my only M20R off-field.  I would be terribly uncomfortable having a hangar elf set 25° of timing on an engine that had a name plate marked 20°.

My thoughts shared,

-a-

[RobertGary1]

True but Lycoming says 25 not 25.00. There is certainly some range in which no difference can be detected. Is it 1 degree off? Is it 0.001 degrees off? As an engineer id be more comfortable if Lycoming published a tolerance because guaranteed they never envisioned mechanics setting with 0.01 degree of accuracy. That doesn't mean there may not be some detectible benefit of that accuracy but it's suspect. 

Said another way. We don't know if the ideal timing is 25.00 or 25.01 because Lycoming didn't give us those significant digits so setting with 0.01 accuracy seems to have little benefit.  

However, the device mentioned here that has that accuracy is not much more expensive than Lycoming's official pointer which is about simply an over priced pencil. So I'm not arguing against the suggested device itself. 

 

Edited October 11, 2015 by RobertGary1

[mike_elliott]

True but Lycoming says 25 not 25.00.

 

I am not sure you can absolutely say for certain using the mark 1 eyeball and the marks on the starter gear that you have precisely set it at 25 and not really 26 or even 23. You can sure think you can, however, but you are giving up some efficiency if you are not spot on. I imagine those that race the planes use this tool or one similar. But if being close is all one cares about, then so be, just be close. Personally, I prefer precision when it comes to engine setup and flying. And really, since you are trying to figure out how to locate where 25 deg. (or more likely 20 on a factory reman that you have) is by asking about mounts for a lazer pointer, why not just get this tool instead of a "rig"? It really doesn't cost much and it also allows you to measure things like flap settings, etc. I have one, and it really takes less time to get it right on than my old method of using fishing line extended along the case centerline which was "sorta" close...An A&P was convinced after he swore he nailed 25 deg and was off by 3 deg. when we first played with it. He now owns one.

[N201MKTurbo]

I checked the timing mark with a time right once, it was dead on. I never need to check it again.

[Andy95W]

If I had a customer come into the shop where I used to work and insist on a magneto timing accuracy of exactly 25.00°, I would have charged him more. A LOT more.  

I time mine using a dial on the prop hub to 24 1/2°, and I'm very comfortable knowing its +/- 1/2°.  But to each their own, I guess. 

[jetdriven]

I checked the timing mark with a time right once, it was dead on. I never need to check it again.

not necessarily.  As points wear they open sooner which advances timing. The breaker point cam on a slick is plastic and can wear, which retards timing. Or they can come loose. You have to check them every 100 hours or so to find this drift. 

[jetdriven]

If I had a customer come into the shop where I used to work and insist on a magneto timing accuracy of exactly 25.00°, I would have charged him more. A LOT more.  

I time mine using a dial on the prop hub to 24 1/2°, and I'm very comfortable knowing its +/- 1/2°.  But to each their own, I guess. 

Then you tell him you are unable to give him 25.0 degrees.  You can't charge extra for a job your cannot measure to the expected precision. If all you can do with a flower pot is +/- a half degree Then that's what you can do.   You can also buy a timerite and charge and extra 40$ to get the timing deadass. I'd pay extra.  It likely takes less time since there's less error of measurement and repeated adjustment of the mags to get them exact. 

Edited October 11, 2015 by jetdriven

[RobertGary1]

And who is to say that 25.0 is better than 25.4? Certainly Lycoming never gave us a preference. They only gave us 2 mathematically significant digits. So if you want it set to 25.0 you just made that last digit up yourself. 

 

-Robert 

[N601RX]

I think he is saying that he has verified that the marks on is flywheel is correct in regards to the centerline of the case which is one of the reasons for the digital protractor.  I purchased a rite system a few years ago and use it. I would say that it probably has repeatability of +-.1 deg mostly due to how accurately you pick up TDC of the piston.  We write the values down each your and compare them to the next year.

Edited October 12, 2015 by N601RX