28th-Mar-20, 02:18 PM
Okay Alan so ONE person here runs on tracks with absurdly long straights.
DISCA is something most unusual, and will only ever be experienced by 80 people a year (16 teams of 5)
My point was that as NEARLY ALL of us don't, to NOT change the ratio when putting in a much more powerful motor, to run on a typical small home of club track would generally be a mistake.
So a good start point in my experience has generally been to split the different between the original ratio, and using a ratio which keeps the same top end speed - if the motors have similar torque. Often when messing about with motor upgrades I go a couple of teeth either side of that middle split principle on my spur (or crown for inline), but end up right back there in the middle for the sweet spot.
In regards to pitch diameter versus outer diameter, I was attempting to point out that your wording of
"Instead, the manufacturers stretch and squeeze extra teeth or fewer teeth onto the same diameter gear." indicates that you were talking in terms of OUTSIDE DIAMETER.
Whereas, as you say in your last post, the contact point along the radii between centre line and outside point of tip changes, so in actual fact, the diameter being talked about is changing based on where the pinion contacts the spur. The pitch diameter is changing.
If you had written
"Instead, the manufacturers stretch and squeeze extra teeth or fewer teeth onto gears with the same outside diameter by changing the contact point along the edge of the tooth which changes the pitch diameter [or working diameter in lay-speak] to keep the effective pitch as close to the base point as possible."
any possible confusion from the first post would be avoided.
Maybe you think this is semantics, - and I really wasn't trying to be picky or score points or anything; but because the layman so often doesn't understand this principle, they think the D.P. (or modulus) changes in proportion to the tooth numbers. It's just something I have spent ages trying to get people to understand in recent years.
And of course as you say, stretch it too far and you end up with a very inefficient - and dang noisy pair of gears.
- Not that this stops everyone running the biggest tooth number pinion possible to get insanely tall ratios for DISCA. a bit either side 2:1
cheers
mark
DISCA is something most unusual, and will only ever be experienced by 80 people a year (16 teams of 5)
My point was that as NEARLY ALL of us don't, to NOT change the ratio when putting in a much more powerful motor, to run on a typical small home of club track would generally be a mistake.
So a good start point in my experience has generally been to split the different between the original ratio, and using a ratio which keeps the same top end speed - if the motors have similar torque. Often when messing about with motor upgrades I go a couple of teeth either side of that middle split principle on my spur (or crown for inline), but end up right back there in the middle for the sweet spot.
In regards to pitch diameter versus outer diameter, I was attempting to point out that your wording of
"Instead, the manufacturers stretch and squeeze extra teeth or fewer teeth onto the same diameter gear." indicates that you were talking in terms of OUTSIDE DIAMETER.
Whereas, as you say in your last post, the contact point along the radii between centre line and outside point of tip changes, so in actual fact, the diameter being talked about is changing based on where the pinion contacts the spur. The pitch diameter is changing.
If you had written
"Instead, the manufacturers stretch and squeeze extra teeth or fewer teeth onto gears with the same outside diameter by changing the contact point along the edge of the tooth which changes the pitch diameter [or working diameter in lay-speak] to keep the effective pitch as close to the base point as possible."
any possible confusion from the first post would be avoided.
Maybe you think this is semantics, - and I really wasn't trying to be picky or score points or anything; but because the layman so often doesn't understand this principle, they think the D.P. (or modulus) changes in proportion to the tooth numbers. It's just something I have spent ages trying to get people to understand in recent years.
And of course as you say, stretch it too far and you end up with a very inefficient - and dang noisy pair of gears.
- Not that this stops everyone running the biggest tooth number pinion possible to get insanely tall ratios for DISCA. a bit either side 2:1
cheers
mark
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