key ways on the crank shaft?

[Handyfarmer]

in the process, of working and studying the engine on my lawn tractor, I noticed something The key way lines up with the crank in the up position, or what would be TDC point, in all my years working on engines, I had not noticed this before, (I am not a mechanic but have done a lot of mechanical work engines and transmissions and other, been doing this for over 50 years, and never noticed this before,

question?

do all cranks and there key ways line up with what would be tdc of the #1 cylinder if it multi cylinder engine, or on single cylinder,,

 

[LS6 Tommy]

Not any any domestic automotive "V" engines I've ever worked on.

Tommy

 

[Ironcrow]

I think it's pretty common for the manufacturer to align the keyway with the first crankshaft throw. On an I4 engine this is TDC. Of course, on a V engine it is not useful for TDC.

 

[Falcon67]

I only see that when the crank damper installed, the zero mark on the damper and the timing tab should correspond to TDC (and should be checked with a degree wheel on any build) - which doesn't have anything to do with the crank key way.

 

[engineer2]

When the factory assembles an engine, and if the engine is in its normal orientation when the timing gears and the harmonic damper are installed, it would make sense for the keyways to be up. Less chance of losing the key when installing these components.

 

[Handyfarmer]

I only see that when the crank damper installed, the zero mark on the damper and the timing tab should correspond to TDC (and should be checked with a degree wheel on any build) - which doesn't have anything to do with the crank key way.

I am not talking about the damper or the timing marks on the block and the damper or the flywheel,

I am asking if anyone else noticed if it is a normal that the key way is lined up with the throw of the crank (or the number one cylinder if it is a inline engine)?
is this a manufacturing norm?

 

[Bessy]

Darn it, now I have to check this on my old Sears tractor... Never noticed or really thought to even check on either the Sears or the Deere.

 

[dmdc411]

Handyfarmer, I've seen both methods for alignment. Facing each other, and not, even seen one engine where the crank key was at an angle of some degree. It varies. My suggestion is get a manual for whatever you're working on. Or use your phone to take detailed pics. Use it all the time at work!

Sent from my SM-T350 using Tapatalk

 

[matt_i]

Its possible, but also worth noting the Otto cycle is 720 degrees of crank-angle. So the #1 cylinder hits TDC twice in that period and only 1 of those is correct for setting ignition timing. One still has to examine the cam/valve relation to determine which one is correct.

The key is sort of a formality with any crank pulley or harmonic balance that's an interference fit with the crank-nose. In production machining they don't use a cute little 1" diameter woodruff cutter like a job-shop would, its the biggest diameter with the most teeth for the longest life. Along those lines I would think it to be most clearance offset 90 degrees from the #1 crank-pin.

 

[bradleykd]

It is all in relation to the phase datum pad. At least in car engine crank shafts. The phase datum is machined early in the process, then the crank pins are milled and ground in relation to this datum. This phase datum becomes the only way to orient the crank, so it is also used in the key cutting machine.

On a 4 cylinder I am working on right now, the phase datum is opposite the number 1 pin. This means the first cylinder piston is up when the phase datum is oriented and the key way is also up. On the V-6 I was working on last year, the phase datum was also opposite the 1 pin, meaning the key way would also be in line with the 1 pin, making that engines key also line up with TDC, but the key would be at about 30 degrees if looking down at the engine.

HOWEVER, it is just as easy to machine that phase datum in any position as long as there is a solid reference point for the phase angles. We cut our keys from the top, but it is also very possible to cut them from any other angle, depending on the machine setup.

All in all, it is not a hard fast rule, but very likely that the key will be at 0 (TDC), 90, 180, or 270 degrees for ease of machine setup.

 

[BillK]

HF,
Basically there is no rhyme or reason to it. I am looking at about 10 crankshafts as i write this. The V-8 Chevy cranks all have the keyway pointed towards the # 1 crank throw. An old Ford has it about 200 degrees off. 289 Ford seems to be off about 10 degrees. A small block Chrysler seems to be pointed at # 1, same with a Pontiac. There is a Ford/Mazda crank that has no keyway at all, which is becoming more common.

So basically to answer your question I do not think there is any hard and fast rule as to where the keyway is located.

 

[Charlie51]

On 4 stroke lawnmower engines, the spark plug fires every revolution-- both power and exhaust strokes.

 

[BillK]

On 4 stroke lawnmower engines, the spark plug fires every revolution-- both power and exhaust strokes.

"Lost spark" Lots of cars the same way but has nothing to do with where the keyway is.

 

[KenC]

On 4 stroke lawnmower engines, the spark plug fires every revolution-- both power and exhaust strokes.

Most, but not all. Older K series Kohlers for instance. Point battery ignition run of cam like older cars. Newer are flywheel mags.