Sheepscot Turntable - Official Work Thread

[Dwight Winkley]

Heard Zack tell visitors, the turntable weight when finished will be 9 tons,
dwight

[Harold Downey]

Design estimate is 9.6 tons.  That's 400 lb. per foot.

[Harold Downey]

Let me clarify slightly:  9.6T is complete turntable bridge weight.  For crane estimation, it would be less.  No rail (1/2 ton), no rail sleepers, no truss rods or queen posts.   Maybe around 8.5 to 9 tons.

Harold

[Mike Fox]

I wish I could be there to help pick that. Baby weight compared to what we pick here. It is all in the rigging.

[Bob Holmes]

Can someone describe how the central parts of the turntable (center bearing, pivot, spider, etc.) fit together.  What is attached to what and is anything freely floating?  What is attached to the concrete base?  Is there some kind of rail that the spider wheels bear on?  What is attached to the trestle itself?  In what order is it all done?  Thanks for clarifying.

[Robert Hale]

Can someone describe how the central parts of the turntable (center bearing, pivot, spider, etc.) fit together.  What is attached to what and is anything freely floating?  What is attached to the concrete base?  Is there some kind of rail that the spider wheels bear on?  What is attached to the trestle itself?  In what order is it all done?  Thanks for clarifying.

In theory this is how it will work, just on a larger scale for the spider rollers. The center pivot bearing will be a plain bearing (I gather) rotating on an axle.
https://en.wikipedia.org/wiki/Thrust_bearing#/media/File:Thrust-ball-bearing_din711_ex.png

[Mike Fox]

You can see the wheels holding up the turntable on the inner ring rail in this picture.

Brendan posted this picture back in January. There is actually a center pivot. I'll see if I can find a picture of that too

[Gordon Cook]

Back on page 10 of this thread, Harold posted a picture of the spider assembly.

I note that on the drawing the spider wheels are described as tapered towards the middle, which would make the wheels want to pull outward, putting tension on the whole assembly.

Perhaps Harold could give us a more complete explanation of the design.

[Dwight Winkley]

page 7, first photo shows the pivot casings, lower left side of cart.
dwight

[Mike Fox]

Here is the photo

[Brendan Barry]

Turntable updates.

Center pin being installed.







Rail bent for the ring rail on the underside of the turntable. The rails have to be trimmed to length and bolted to the turntable.



Queen posts.

[Robert Hale]

You can see the wheels holding up the turntable on the inner ring rail in this picture.

Brendan posted this picture back in January. There is actually a center pivot. I'll see if I can find a picture of that too

Why is there a third tie-rod between the queen posts in this photo? Is it a modification of the design? Or something of an after thought because of issues with the queen posts?

[Jason M Lamontagne]

The tie rod is in the original Portland Company design.  It works against the compression strut lower down in the posts to hold them in the correct (angled) vertical orientation.

See ya
Jason

[Robert Hale]

The tie rod is in the original Portland Company design.  It works against the compression strut lower down in the posts to hold them in the correct (angled) vertical orientation.

See ya
Jason

I kinda figured that. One other thing you can see in the photo is how the main timbers are bowed upwards a bit even with the engine on the turntable.

[Benjamin Campbell]

Really great work!!!! I had asked earlier in this thread where and how the ring rails were being bent? Any photos of it being done?

I do wonder whether a steel center pin should be used for the bearing? While there should not be much lateral impact on the bearing arrangement it would not take much to snap a gray iron pin. Whether turned from the solid or a weldament – a steel center pin would give an extra degree of protection to equipment and persons. In the close up photo the spider wheels appear to be flanged which would have helped keep everything centered. In our design everything relies on the one central pin and cup.