High Accuracy Degree Wheel

[posplayr]

The biggest issue with getting accuracy with your degree wheel is the piece of wire pointer. A bigger degree wheel (18") helps but is not really necessary. I tried a laser pointer, but ended up with a simpler and very stable/accurate method of getting readings. I needed to create a small (like a rifle) sighting type pointer and used a straight edged razor to acheive this.

Even with a 9" degree wheel, this safety razor welded to a clutch cover bolt allowed for +/- 0.1 degree (+/- 1 sigma) accuracy readings.

It is hard to adjust the valve timing to less than 0.5 degree increments (my experience last time Chef and I did it). Just make sure you are looking down the length of the razor which you have aligned to be nominally radial to the wheel (when you site you are approximately looking at the center mounting bolt.

See razor welded (at upper left of the wheel at 45 deg ATDC) to the bolt below.

Pos

[jknappsax]

Are you using this to degree your cams?

[reddirtrider]

Are you using this to degree your cams?

Either that or a built in finger slicer.

When you aim at a target from 500 yards, you have to center the bullseye in the middle of the front sight. I use the same technique with a bent closehanger.

[posplayr]

Either that or a built in finger slicer.

I failed to mention that I dulled the edge of the razor without loss of accuracy.

I use the same technique with a bent closehanger.

U put a closehanger on your rifle?

[sharpy]

The biggest issue with getting accuracy with your degree wheel is the piece of wire pointer. A bigger degree wheel (18") helps but is not really necessary. I tried a laser pointer, but ended up with a simpler and very stable/accurate method of getting readings. I needed to create a small (like a rifle) sighting type pointer and used a straight edged razor to acheive this.

Even with a 9" degree wheel, this safety razor welded to a clutch cover bolt allowed for +/- 0.1 degree (+/- 1 sigma) accuracy readings.

It is hard to adjust the valve timing to less than 0.5 degree increments (my experience last time Chef and I did it). Just make sure you are looking down the length of the razor which you have aligned to be nominally radial to the wheel (when you site you are approximately looking at the center mounting bolt.

See razor welded (at upper left of the wheel at 45 deg ATDC) to the bolt below.

Pos

I just use a pointed bit of wire bent over the disc so u look are it 90 degrees to the bike. Whats ure cams set at? Mine are running at 106 centres.

[posplayr]

sharpy

I just use a pointed bit of wire bent over the disc so u look are it 90 degrees to the bike. Whats ure cams set at? Mine are running at 106 centres.

Yes I know most people just use a stick of wire; that is even what is provided with the "store bought kits". The issue is of course being at 90 degrees and having a sharp point and having it close to the edge of the wheel. With a 8" wheel each measurement could be off by as much a 1 degree and cause you to chase your tail as you keep rotating the cams looking for open/close 0.050".

Rapid Ray claims degreeing the cam is much easier with a 18" wheel rather than a 9" wheel. You have twice the displacement at the circumference at 18". I have no argument it certainly is easier to get within a degree.

There really is no way to know you are at 90 degrees. By "sighting", you have established a vector is is much more accurate that the assumed 90 degrees.

Of course if you can place a thin wire at 0.010" above the wheel then the 90 degrees doesn't matter as much, but there is still error.

Using the sighting pointer I can get to +/- 0.1 degree 1 sigma with an 8" wheel; I did not need to drop $55 for a 18" wheel.

Web cams 0.340" lift cams set as recommended at 105 Int 107 Exhaust. We were about 0.25-0.5 degrees off on when all said and done.

Pos

OK Some numbers.

for a 8" degree there is 0.070" separation between 1 degree hash marks

If you have your pointer 0.5" off of the wheel and read the wheel from 3 foot away then

6 inches of lateral movement in your eyeball is 0.083" (1.2 degrees) error

If you have your pointer 0.5" off of the wheel and read the wheel from 2 foot away then

6 inches of lateral movement in your eyeball is 0.125" (1.8 degrees) error

So how well are you relocating your eyeball measurement to measurement?

[chef1366]

The "Mad Max" method.
It worked! Bike runs great! Great low end grunt a great powerband. When the carbs are dialed it's going to be a madman!

[sharpy]

ok i see ure point.. My pointer almost scraps the wheel but i see where ure coming from. thanks

[reddirtrider]

U put a closehanger on your rifle?

You missed the point (no pun intended).

[posplayr]

Quite Right

You missed the point (no pun intended).

I found a very accurate method of reading the degree wheel by not using "the point" on a wire which is subject to the errors as I explained.

Pos

[reddirtrider]

I found a very accurate method of reading the degree wheel by not using "the point" on a wire which is subject to the errors as I explained.

Pos

I'm not disagreeing with your method. To each his own. You once again missed what I was saying. I'll drop it.

[posplayr]

Missed something

You once again missed what I was saying.

Despite the tangents , puns and misdirections your only point seems to be that you use a piece of wire to degree your cams. That is quiet obvious from your first post and is hardly any surprise as I'm sure 99% of people do it that way.

As I stated:

The biggest issue with getting accuracy with your degree wheel is the piece of wire pointer.

99% of the people degreeing cams apparently have no consideration of the accuracy issues of reading the wheel or are happy with just good enough and as such are happy using a piece of wire. U seem to be in the same camp if I got "the point".

So other than to say "I could careless about accuracy in reading a degree wheel", I don't get your point. Is there anything else you are trying to say?

Getting back on point, racers like Rapid Ray are at least sensitive to the accuracy issues of small degree wheels and have taken to using large over sized degree wheel to improve accuracy. The described method exceeds typical 18" degree wheel accuracy using an 8" degree wheel. It might also make a paper degree wheel acceptable but that is subject to too many variables to be conclusive.

Is there anything else I missed?


P.S. as to your safety concerns, I did use a safety razor

[reddirtrider]

Is there anything else I missed?

Yes, you've narrowed your focus down to the accuracy at which you can read the wheel and assume that it cannot be done with a pointer (which most tuners use BTW).

There's a whole lineup of tolerance issues that go into degreeing a cam. For instance, how accurately can you stop the crank? 0.1 of a degree? If not, then your accduracy cannot be within 0.1 of a degree. How about the tolerances associated with the camshaft itself? Do you know what the manufacturing tolerances are?

Here's the point you missed and it's not tangental, a pun, or a misdirection. You don't need a fine line in order degree a cam. I can use a pointer that covers an entire degree on the wheel and still get the accuracy needed by centering the marker on degree wheel on that fat pointer. It's very similar to shooting at 500 yards. The bullseye is much smaller in diameter than the front blade.

Hey, it's a nice idea and I'm glad you like it. Bottom line is, It's my opinion it's not going to work any better than a pointer.

[posplayr]

reddirtrider

I can see that this discussion with you is pointless; this is the point I'm finally grasping.

Just so you know, I have a MSECE with primary focus on Control and Estimation and close to 30 years of systems engineering under my belt. I've worked in the areas of ultra high accuracy inertial navigation, fire control and flight guidance and controls. That means I have a thorough understanding of measurement accuracy, positional accuracy, estimation uncertainly and certainly standard deviations.

I don't mean this to boast simply to offer that information in leu of a specific answer to your suggestion I missed something about overall engine timing accuracy. Your quotes are incorrect and the proposition is laughable.

Since you are not willing to read the essential elements of the prior posts, it is hardly worth my time to elaborate considering you don't read or understand what is already written.

Good Day.

Pos

P.S. my Next Tricks and Traps post will be entitled "High Accuracy Engine Stops"; can U guess how that will turn out?

[reddirtrider]

When all else fails post credentials.

I won't bother with mine, since they are irrelevant to the discussion. If you refuse to take into consideration other sources of error in this system, then as you say, this discussion is pointless.