Problem Encountered; need advise

[Hwingo]

Good Morning Art.

Profile shift applied to one gear requires (basically) the application of an opposite shift to the opposing gear. Correct? What happens when a shift (perhaps out of necessity) is applied to the gear being fabricated but the opposing gear cannot be easily altered nor easily re-fabricated? Is this where a wee bit of "wiggle factor" may be allowable without severe consequence?

Harold

[ArtF]

Harold:

Yes. Ideally, the two gears are meant to mesh right on the pitch line, what happens if you pull them out a
bit is the pressure angle changes, but they still mesh, albeit a bit more loosely as the tip of the tooth thins.
  In most applications Ive come across there is more wiggle room than youd think. Thats why I think
printing a blank to see and judge a fit is a pretty good way to see how good intuitive fits are..

Art

[Hwingo]

Thanks Art. Message received.

I am in the process of doing a comparison between the original gear and the purposed gear. I should have the results fairly soon and I will post for your inspection.

Harold

[Hwingo]

It?s now obvious to me, though it has been obvious to you guys from the beginning, that I am dealing with a non-standard pinion gear. Though the original pinion gear can be defined as non-standard for several reasons, e.g., tooth form and tooth number (and perhaps other reasons such as DP and PA), the designer of this ?system? has, indeed, designed a ?system? that seemingly works.

I have no real way to neither alter the original wheel-gear nor fabricate a new wheel-gear (which is too large) so that it can articulate with a new pinion gear which has been given ?shift?. Conventional logic would be to do my best to replicate the original pinion gear as closely as possible. After all, the original pinion gear, with all its anomalies, has been designed to work with that system. The problem that I am having is, I have no ?gear making wisdom? since wisdom comes from experience. So, I haven?t the education/experience to know if I can have a ?wiggle factor? of 0.001? or one of 0.010?. One important tip that you have given me is, the Pitch Circle diameter is the most important thing to consider. Decision making is very difficult at this stage of my educational development.

Here are knowns from original gear:
1. The original pinion gear is 0.996? OD
2. The gear has 9 teeth
3. The Pitch Circle diameter is N x OD / N + 2 thus:
    9 x 0.996 / 9 + 2 =  0.8149? Pitch Circle diameter
4. Using the formula N + 2 / OD, the Diametral Pitch is 11.0442
5. Measured distance between teeth, at roots of teeth, is 0.100?
6. Measured distance between teeth on circle is 0.13799? (see first image)

Here are knowns from new gear:
1. Recommended OD of purposed pinion gear = 1.0828?
2. The gear will have 9 teeth
3. Pitch Circle dia = 0.8858
4. Diametral Pitch = 11.01
5. Measured distance between teeth, at roots of teeth, is 0.100? using Gearotic measuring tool
6. Measured distance between teeth on circle is 0.167? (see second image)

Here is non-factional information:
1. Using a 14.5 deg gear pitch gage, the *best fit* for the Pinion Gear is the 12 pitch blade.
2. A 20 deg pitch gage does not fit the pinion gear
3. There is result-disparity between the 14.5 deg pitch gage and the mathematical formula.
4. At this stage of my development, I trust the formula more than the pitch gage but there remains plenty room for doubt inside my vacant brain.
5. It appears that the distance between teeth on the pitch circle is greater in the proposed gear than the original gear. I suppose this means that it?s back to the drawing board and come up with a gear whose pitch circle diameter is equal to or less than the original gear. Right?

Harold

[ArtF]

Harold:

  Im of the opinion your fine. As long as the tooth space is larger , the teeth of the wheel will fit.
The teeth dont have to hit both sides, youll be turning in one direction only, right? you could is essence cut each tooth in half
and use only the ide facing the direction of rotation. In fact cutting edge gears are now doing that and calling then asymetric
tooth forms.
  I think the drawing you have will work fine, as I said, Im not sure you have a full concept of just how much wiggle room you have on
a low speed , relatively low torque gear. So long as it fits on the shaft and its teeth fit reasonably into the wheels spaces..youll be fine..

worst case..it will wear a bit faster than otherwise..

Art

[Hwingo]

Hi Harold:

  As you shift a gear positive, the spaces shrink between the teeth, the theory being the spaces on the other will be enlarged.

What you need is the width at the pitch line on the other gear, no other measurement is real important. If the width on the mating gears pitchline is X, then if yours is <=X your gear will work. If you have the capability to shift the center distance then you wont have any trouble no matter what you do, if you profile shift your gear outwards by .6 as John did, that implies only that you need to shift the center away from the original mate by the same shift if you dont intend to recut that one.

Art&nbsp;

Ok Art, I think I am beginning to understand. When I read one of your earlier posts, I somehow got it in my mind that the new pinion gear had to be equal to or have less distance at the pitch line than the older pinion gear. Since reading your statement again, the space to which you were referring was space on the mating gear’s pitch circle. I haven’t even begun to attempt calculating the pitch circle diameter of the big wheel. However, since I have the motor mounted on a sliding plate, I can either move the motor closer or further away when meshing the gears. According to your statement, if I understood it correctly, I should have no problems because I can move the entire motor closer or further away as necessary when meshing the gears. Did I read that correctly?

Harold

[ArtF]

Harold

Yes, exactly. It sounds to me like your calculations so far are good, so you should be close enough that
sliding back and forth will get you in mesh, your pressure angle may not match up exactly, but you have no real load
and no high speeds, so Ill bet it works fine.

Art

[Hwingo]

Thank you very much for hanging in there with me. Very much appreciated.

Harold