Turntable Design and Build

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Glenn Brooks
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Turntable Design and Build

Post by Glenn Brooks » Sun May 29, 2016 11:15 pm

Thinking about including a turntable in my backyard RR ROW (12" gauge). I have the flanged wheels, curved rail and some surviving hardware for the original turntable that came with the motive power and rolling stock (Ottaway stam engine, couple of riding and work cars and two 1960's vintage home built diesel switchers).

I haven't found any design criteria for the original turntable. Indeed the rotating 'bridge' was buried under deadfall and leaves when I discovered it, while removing the track from the prior owner's property last year. So never saw it in operation, or indeed, even installed.

So, trying to come up with some design ideas to build a new one. Anybody have any experience with turn tables for park gauge or 7 1/2" ga ? I know there is a small one at Traintown in Pa, which turns a Cagney. But know nothing about it, except

Iam particularly interested in whether these smaller trains (live steam scale) need to have a center pivot point to turn the loco on the turntable? If no pivot point, is it possible to turn a 2000# loco and tender by hand, if only supported on the rail flange wheels mounted on the ends??

Thanks much,

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

RONALD
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Re: Turntable design

Post by RONALD » Mon May 30, 2016 7:59 am

I researched turntables starting around 2000, and as you found out very little has been written about their construction. I was trying to make a scale model of the N&W's Lambert's Point Turntable built in 1913. As I researched further, I found that there were two main builders of turntables American Bridge Co. and Bethlehem Steel Co.; I had thought most TT's were homemade, I was wrong. I was fortunate to find a set of A.B.C. plans for their 1913 turntable model, which was exactly what N&W purchased from them.

You can read about my work in the March/April 2008 issue of Live Steam And Outdoor Railroading.

I also made a DVD of that work which one of the guy's put on you tube:

https://www.youtube.com/watch?v=cu7Cou5zVi0

Here is a photo of the TT with an engine on it.
Attachments
DSCN2339_2.jpg

Glenn Brooks
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Re: Turntable design

Post by Glenn Brooks » Mon May 30, 2016 7:32 pm

Ron, your turntable looks fabulous. A real gem of infrastructure. Where did you find the original drawings?

Given the overall relative light loading on scale turntables, in your experience, are center pivots necessary? In other words, could the turntable work satisfactorily with just turning the engine on wheels mounted on both ends of the table?

Thanks
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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FLSTEAM
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Re: Turntable design

Post by FLSTEAM » Mon May 30, 2016 7:51 pm

Glen

Since you said this was for a 12" ga. Cagney you might want to consider something dated a little older. Here is the gallows turn table I just built. It is built to 2.5" scale and 12' long.

I can turn my Shay ( 800 lbs. ) with one hand.

John B.
Attachments
Tunrtable12-30-15A.jpg
http://www.ngshay.com/
Shay drawings and castings

Glenn Brooks
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Re: Turntable design

Post by Glenn Brooks » Mon May 30, 2016 8:25 pm

Thanks John, very interesting design. Good use of wood material. do you have any photos of the pivot point, or maybe a sketch of how you engineered it? I am curious how much loading occurs at the pivot and how large should be the shafting and possible bearings. Also does your table rest on a bearing on some sort, or are the bearings only for turning the table??

Thanks much,
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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FLSTEAM
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Re: Turntable design

Post by FLSTEAM » Tue May 31, 2016 6:38 am

Glen

The table is a copy of the original. It uses a "spider" i.e. 8 spokes with a wheel on each. There are two angle iron rings that are used to roll on and keep the table centered. Very little load is carried on the outboard rollers. They are mostly for keeping the table level.

If you really get interested in building one I have plans ( well sketches ).
Here is a picture of the forms used to pour the base. I would do things a little different if I was doing it again.

John
Attachments
Turn Tabel Base forms.JPG
http://www.ngshay.com/
Shay drawings and castings

RONALD
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Re: Turntable design

Post by RONALD » Tue May 31, 2016 8:26 am

Glenn, what you are proposing a "Center-less" turntable would be almost impossible to build; like the wheel, a RR turntable is basically just a lever.

There are three kinds of levers, and depending on where you put the fulcrum you get different results.

In your case, you are putting the fulcrum at the wheels, and if you apply a torque to the other end it will want to rotate around those wheels, which will not give good results.

Of course, if you created a sort of "Lazy-Susan" type of TT, with many rollers spaced and confined near the edge, you might achieve what you want.

If a "Center-less" turntable was easily built, the RR's would have had those in the 1840's.

Below is a part of what I wrote for Live Steam & Outdoor Railroading in 2008, that information is ten or more years old, the guy who sold me the drawings may no-longer have a web site.
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screenshot1.jpg

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ccvstmr
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Re: Turntable design

Post by ccvstmr » Tue May 31, 2016 8:34 am

Glenn...check this out: http://www.rwmcasters.com/parts_accesso ... ctions.cfm

Helped a friend late last year build/install a turntable for his 7.5" gauge, 2.5" scale RR. Built a 15 foot turntable to get a gallows type "decoration" as FLSTEAM showed in his photo. The turntable still required a center footing and support, but now the out-rigger wheels don't have to support as much weight. If you design the center swivel to be supported on (4) large thread rods...you can use the nuts to level the swivel and bear most of the weight with the out-rigger wheels to support the turntable and train/loco weight during loading/unloading. The swivel design keeps weather out of the bearing race (well, most of it). Comes with grease fitting. Several sizes to choose from. If this isn't what you're looking for...hope this at least gives you some ideas. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
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Erskine Tramway
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Re: Turntable design

Post by Erskine Tramway » Tue May 31, 2016 8:50 am

Hi Glenn......

Do you want your table to be a 'model' or do you just want to be able to turn your engines?

Our original turntables on the 15" gauge Riverside & Great Northern Ry. at Wisconsin Dells had a flat plate riding on top of a large pin for a pivot, with a 'collar' plate below to keep it in line. The bridge itself was two "I" beams, with a truss rod on each side. If you had the engine balanced on the table, the load rode on the pin, the end rollers didn't touch the ring rail. I had a stripe painted on the wooden 'deck', and I would spot the injector overflow pipe at different distances from it, depending on how much water I had in the tender. Properly balanced, and greased, I could 'spin' the 5-ton Atlantic by hand.

Here's the only good photo I have of the Western Springs table, by Russ Porter, of me 'walking' the #128 off the table in 1965.
Western Springs, 1965 R Porter photo mail.jpg
Good luck with your design..

Mike Decker
Former Locomotive Engineer and Designer, Sandley Light Railway Equipment Works, Inc. and Riverside & Great Northern Railway 1962-77
BN RR Locomotive Engineer 1977-2014, Retired

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NP317
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Re: Turntable design

Post by NP317 » Tue May 31, 2016 9:46 am

Glenn:
By design, railroad turntables carry most of the weight on the center bearing device, what ever design it is. The outer rails are more for guidance than weight bearing.

I have operated a 90-ton steam locomotive on the S.P. turntable at the California Railroad Museum in Sacramento, CA. This was during their 10-day opening celebration in 1982. Two steam shows were held daily, in which locomotives steamed onto the turntable for a 360 degree display rotation.

I always had to carefully position the locomotive so the table was balanced (it actually rocked on the pivot), but with some weight over the end with the driving motor. Then the outer guide rail load was light enough for the small air-operated motor to turn the table & engine.

Off-subject: My big challenge with that turn table was positioning the locomotive. One foot made a big difference, and a super heated locomotive has quite a throttle delay! I was not always successful the first try in front of the audience...
It was a remarkable experience!

~Russ

Glenn Brooks
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Joined: Mon Nov 10, 2014 1:39 pm
Location: Back in Washington, Alas

Re: Turntable design

Post by Glenn Brooks » Tue May 31, 2016 2:13 pm

Thanks all for the great feedback. I will go with the center pivot design you all recommend. Have located one of the RMW 5000 # turntable bearing pivot units that Carl mentioned, on line for a reasonable price and with some judicious scrounging around have found some 5 x10 I beams for the table portion. Not free, but very affordable. These should be plenty strong.

My last decision point is whether I can install the round table to work with my mainline? E.g. Build it in line with the main line and how to fit into a 40' radius curve. I am very limited in space around my shop, so one of the ideal locations is to put the turntable in line with my main line loop about 25' from the shop doors. This so I can divert rolling stock onto a storage siding and also load engines and cars onto a small secondary loading ramp to bring stuff onto the shop for repair/refurbishment to n rolling carts with casters. I guess it's a matter of building the ends of turntable with a close tolerance so they don't rock much when a loco goes through.

Edit: one other consideration I just thought of: how big and deep should I make the cement foundation that the pivot will mount on??

I am thinking there are design considerations for counterbalancing the vertical movementof the engine sitting on top of the table, etc??? Build a simple web of roots out of angle iron extending out from the base, like a tree puts down, or maybe just 2' cement shaft poured into the ground.... Any ideas???

Well, Iam off to try to determine final height of the rail at the turntable...

Certainly would apprecrate any comments regarding feasibility and design issues I should be watching for.

Regards
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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ccvstmr
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Re: Turntable design

Post by ccvstmr » Fri Jun 03, 2016 7:26 am

Glenn...you were asking about the foundation for the center pivot. I'm not a civil engineer, but would say center pivot foundation design depends mostly on the type of ground you're installing this turntable on. At a minimum, I'd think something at least 12" square would be needed to set the pivot base for large thread rods that will support the pivot. 3 large rods would be good...and that would allow you to level the center pivot like a surveying sight or laser. The thread rods would also allow you to raise or lower the center pivot to level and line up (horizontally) with the ring rail. 4 large rods would probably be better. Foundation depth? Have to consider Winter frost line depth. If using the thread rods in the center...I'd bet you don't want to be utt adjusting the center pivot height every Spring. If frost is not a problem, at least 12" deep...or maybe as much as 18 or 24" deep should suffice. Not sure if this helps...but at least it's a starting point. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!

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