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[Kirk]

Split shaft collars have amazing holding strength. (much stronger than set screw type) Perhaps you could have one made to the correct diameters, or perhaps you local bearing shop will have one with the right inside diameter and you could weld a steel plate to make the correct outside diameter.
The hope is that you could grind/saw/hack the old one out and then bolt the new one in place.

[JMauk]

Split shaft collars have amazing holding strength. (much stronger than set screw type) Perhaps you could have one made to the correct diameters, or perhaps you local bearing shop will have one with the right inside diameter and you could weld a steel plate to make the correct outside diameter.
The hope is that you could grind/saw/hack the old one out and then bolt the new one in place.

That is exactly the type of design I had in mind.  Didn't know they existed, especially ready made.  I think such a collar could be inserted without removing existing plates.

[JMauk]

Here is today's test with extra weight.  Have a more complete video of both tests today coming up next.

[JMauk]

As Promised--

[ta0]

That went very well! Nice and smooth and probably faster.

I hesitate to calculate a rotation rate because there is a frame skipping problem on the video, probably due to the editing of both videos together. Could you re-post the video of just the top again (preferably the raw video)?

Anyway, that top is spinning great. Congrats!

[JMauk]

Thanks.  As shown on one video, a piece of the top layer of plywood on one side of the spool did come loose. Not big but a sign the plywood will not hold up over time.  I am thinking also that the blue rope we are using is not as thick as the original climbing rope we planned.  I think the rope is layering on itself during the pull.  So am thinking to redo a core like Kirk's split-shaft collar attached to two metal plates.  It should fit into the current spool slot and be the right diameter for the blue rope. 

Working on uploading the raw video segment of the spin, I think it's sideways!  Don't get dizzy!

[Jack]

As Promised--

i have a question: why does the rail car seem to learch? is that the video or is it part of the mechanics?

[JMauk]

I think the hesitations are because of the layering of the rope on top of itself, compressing and uncompressing.

Here is raw video link:

Ooops, not the one I was thinking of.  Will try again. The original was sideways.  Will see if I still have it. 

[JMauk]

Nope, I did load the sideways one, youtube just won't play it sideways!

[ta0]

Thanks for re-uploading the video. This time the timing had no problems.
Unfortunately, you are still stuck at about the same peak rotational speed: 182 RPM.
The hesitations in the cart show that it could be a little smoother. Also there is some energy left on the cart when it gets down. I still think you could break 200 RPM of peak rotational speed if you had everything perfect. But I am not sure how useful that would be because the rotational rate decreases quite fast:

@ t_o (30s)  => 182 RPM
@ t_o + 26s => 150 RPM
@ t_o + 95s => 100 RPM

Air drag is your limiting factor.

Watching all the crew pulling the rope to raise the cart I could not help thinking on the ancient Egyptian building a pyramid.

[JMauk]

ANNOUNCING END OF TESTING FOR 2014

Posting some pics of the deterioration in the plywood spool for the pulling rope.  Bolts have started falling out!  Well, it was left out in the weather for two years before we could put a roof on it and start testing again.  We will be removing the lower cone and rehabilitating upper part of spool. Will have a new metal spool with split shaft collar attachment machined and installed.  Then will rebuild lower cone portion.  When all finished will start testing in the new year.  Happy New Year!

[ta0]

A brand new spool is a good idea. It is the most critical piece of the top.

As I see it, there are 3 main factors that you can work on that will determine your maximum rotation rate:

1. Weight on the cart = total energy available
2. Mechanical losses due to friction along the rope path, possible pulleys misalignment, etc.
3. Minimum diameter of the spool core = final gear ratio

In principle you want the smallest spool core diameter possible. Perhaps you need a longer belt pigtail at the end of the rope.
The maximum diameter of spool is not critical, but will be a factor in how smooth is the acceleration, what is important as any jolt will decrease the efficiency.

Happy new year to you: 2015 is the year of the big record!

[lincolnrick]

Your progress this year was amazing and I predict 2015 will be the year of the Giant Top!!

[Jack]

I predict 2015 will be the year of the Giant Top!!

screw this year as the year of the sheep! we shall declare it so! the year of the largest top to ever spin here here!