Post by: erh300 on February 21, 2007, 03:23:11 PM
Post by: pinbuffer on February 22, 2007, 05:54:20 PM
Post by: Re-Evolution on February 22, 2007, 08:33:30 PM
Yes the bowties should be 180° from each other.
pinbuffer
your statement is inaccurate the track diameter has nothing to do with where the bowtie is located. The initial and final track will be of different diameters due to the migration the ball goes through. As the ball travels down the lane it loses axis tilt which causes the track diameter to increase. The only time it would not change is if you are a full roller or the ball skidded the hole way down the lane and never lost it's tilt. If the latter happens the ball will hit like a marshmallow cause it won't have enough traction to drive through the pins properly.
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Post by: pinbuffer on February 24, 2007, 07:55:13 AM
You're correct, I shot my mouth off based on a poor assumption. I talked to someone with actual knowledge (as opposed to me who has none
) and he said I was an idiot and you were absolutely correct. As the ball hits friction, it loses both tilt and rotation due to the effect of gimbal. Still not sure what gimbal is So after I was thoroughly confused during our discussion, I asked about the 180* thing... he said yes, but followed it up with a "who cares". (Well obviously some of us do) I wonder if I can find a class that crams 4 years of Physics into a few months.
Sorry again for answering without a full understanding.
Post by: erh300 on February 24, 2007, 04:05:57 PM
Post by: Re-Evolution on February 24, 2007, 06:48:06 PM
The bowties will only be 180° from each other on the track but not the ball due to the fact that you are not tracking around the full circumference of the ball.
For example lets say you have an average amount of tilt say 13 2/3° with this amount of tilt you would have a track diameter of 11.5". In this case the bowties would be 180°/11.5" away from each other on the track but for them to be 180° from each other on the ball they would be 13.5" from each other.
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Post by: Re-Evolution on February 24, 2007, 07:02:37 PM
I don't really feel that gimbal is a proper term due to the fact that a gimbal is part of a 2 or 3 axes system (gyroscope) that resists migration and a bowling ball only has 1 axis which migrates to a preferential spin axis.
copied from answers.com for reference:
gimbal
A gimbal is a mechanical device that allows the rotation of an object in multiple dimensions. It is typically made up of two or three pairs of pivots, mounted on axes at right angles. A three-axis gimbal may allow an object mounted on it to remain in a horizontal plane regardless of the motion of its support. Shipboard compasses, chronometers, stove and even drink holders are typically mounted on gimbals to keep them level to the horizon at all times.
Illustration of a simple two-axis gimbal.In aerospace navigation, a gimbal is a device using Euler angles to measure the rotation of an object in three dimensions and to control that rotation. Gimbals used in spacecraft have three sets of three gyroscopes in the inertial measurement unit (IMU), one for each axis (x, y, and z). These gyros provide a stable reference to the vehicle's position and attitude in all three dimensions.
Gimbal lock occurs when all three gyros hit the limits of their ability to move within the sensing mechanism—they hit hard stops and stop moving around.
In a normal situation, the gyros are aligned with the vehicle's local reference - +x being in the velocity vector, +z being in a radial vector pointing to the earth (for earth orbiting vehicles) and basically pointing downward (using the control panel for reference) in the Apollo CM, and +y being a right-handed complement to the +x vector. Aligning the platform (the IMU's) was done at launch (to give an initial position) and at various times during the mission when the vehicle's position is accurately known. During AS-XII, the movement of the vehicle exceeded the normal rates for movement in the respective axis, and was nearly hitting the stops in the IMU.
The "eight-ball" was used for gravity-oriented flight parameters only. It was basically the same as the "eight-ball" flown on airplanes - that is - a gyroscopic platform which aligned to the local gravity field.
Gimbal mechanisms are also used in some mirror mounts, for precision rotation of optical elements without translation.
In spacecraft propulsion, "gimbaled" refers to a pivoting or swiveling mount, often for a rocket engine. For example the space shuttle main engines are gimbaled -- they can point in different directions to control the vehicle flight path.
The world's largest gimbal was constructed to simulate the capsizing of the USS Oklahoma in the movie Pearl Harbor.
In saltwater fishing,it is also a device used for landing large fish. When fishing with a large rod, a gimbal transfers the weight of the rod from the arms and wrists of the angler to the hip or waist, effectively allowing the angler to concentrate on leveraging the rod instead.
Inside the gimbal there is usually a horizontal pin that the fishing rod locks into, allowing rotation of the rod in one plane only, up and down.
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Post by: pinbuffer on February 26, 2007, 09:28:25 AM
quote:
I posed this question because in all the times I've sanded a ball at the bowtie, the bowties (or my marking of them) never seem to be exactly 180* from each other. It's always confused me because I believe they should be. I don't let it bother me, though, and just sand at the top bowtie, flip the ball 180* and sand it again even if my mark on the ball doesn't line up. I just thought I'd finally ask and get other opinions.
Well, it's easy enough to estimate what angle it is. Trace your flare ring and mark your bowtie locations. Measure the circumference (C). Then measure the distance from bowtie to bowtie along the circumference, this is arc length (s). Now we calculate the angle (θ ) and convert the angle from radians to degrees.
( s * 2π ) / C = θ
( θ * 180° ) / π = angle°
Assuming I did my substitution correctly (Given my track record in this thread...), you will get the approximate angle you are curious about.
Due to all the other elements mentioned, i.e. migrating axis, loss of tilt and rotation, I'd assume that there may be a change in angles depending on which flare ring you choose.
Post by: pinbuffer on February 26, 2007, 10:04:33 AM
quote:
pinbuffer
I don't really feel that gimbal is a proper term due to the fact that a gimbal is part of a 2 or 3 axes system (gyroscope) that resists migration and a bowling ball only has 1 axis which migrates to a preferential spin axis.
Well, I can only state what I was told by the my friend and that was "effects of gimbal". But upon further personal research, I've run across http://en.wikipedia.org/wiki/Precession which I think can certainly help in understanding this problem a bit more.