Turntable Design and Build

Where users can chronicle their builds. Start one thread and continue to add on to it.

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Glenn Brooks
Posts: 1453
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Turntable design

Post by Glenn Brooks » Sat Mar 04, 2017 1:31 am

More progress on the turntable since the January storms have subsided.

I have been able to clean up my set of 90 year old, double flanged, turntable wheels and press new 2 1/2" axle blanks into the old bearing races in the hub of the wheels. The process was a bit complicated as I needed to center the wheels in a four jaw chuck, then bore out the old rust and crud to achieve a concentric ID. Lots of rusty iron dust on the old Utilathe after four wheels!

Then went up to the local scrap yard and purchased 4' of what turned out to be really nice quality, old 3" shafting. Cut it down to 9" blanks, then turned down the OD to a press fit for each of the wheels. Tried to heat the wheels and shrink fit the axles, but the wheels contain so much embedded oil and grease they just heated up and oozed burning oil - re-rusting and sooting the ID with burned black carbon and iron oxide - ruining my clean surface and making a decent shrink fit all but impossible. So cleaned out the junk again and turned the axles a few thou more for a cold press fit. After some nervous moments, they all KA-THUNKED into place. I turned a 1/4" shoulder on each axle to hold each wheel to the correct 'gauge' when pressing the wheels onto the axles. You can see the beginnings of a shoulder in the axles in the first photo below.

The photos below show the axles in my initial stages of turning the blanks down to fit the wheels.
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The photo above depicts one axle blank and a second pressed into one of the double flanged wheels.
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Above is a side view of a wheel, showing the 2 1/2" center bore. A 1" axle fit in the center, and was surrounded with 6 each, 3/4" OD roller pin bearings - all packed with grease and held in place with giant washers on each side of the wheel. When I got them, the whole mass was rusted together into one big glob. Judicious torch work and a big hammer got the axles and bearings out of the wheels without damage.
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Once I pressed the axles into the wheels, I discovered I couldn't hold the wheels in the chuck - the axle blanks protruded into the spindle to far, holding the wheel flange away from the chuck jaws.

Sooooo, went to 'Plan B'- set up the lathe to turn the whole thing between centers. Which didn't work because the wheel centers had worn to a serious non-concentric diameter. The wheels flopped around on the axles blanks like they were mounted on an eccentric - which in fact they are, due to the now non concentric holes in the wheel hubs. The diameters and centers of each wheel were offset up to 1/8" in one case. I think this is due to the 6 large 3/4" pin rollers in each wheel, wearing away the inside of the wheel hubs during the prior decades of use.

Sooo, Plan C consisted of holding one axle end in the four jaw chuck, then dialing in the true center of the wheel by indicating the tread of the wheel flange. Once I found the true concentric wheel tread surface, I was able to drill concentric centers on the ends of the axles with a counter sink mounted in the tail stock. This actually worked pretty well. But I did spend a lot of time finding the Geoid of each wheel e.g. the 'smoothed' diameter of the wheel tread. I also dressed the tread and flanges to have decent reference surfaces should I need to revisit these things on the lathe, latter on.

Finally reverted to Plan B and turned the wheel/axle sets on center to accept 25mm flange bearings on each end of the axle stubs.

Here is a photo or two of one of the axles sets mounted between centers in my 95 year old Dalton 7" lathe. I've been using the Dalton to make the finish cuts to final diameter and turning the hubs to fit inside the steel housings I will make next. These housings will hold two bolt flange bearings that support the wheels. They in turn, will be bolted onto the ends of the turntable bed. The wheels and housings will guide the table around the ring of track I will lay down around the inside of the outer edge of the foundation -whenever it stops hailing, snowing, sleeting, and raining cats and dogs.

BTW! This is my first serious lathe operation since refurbishing my old Lot 5 Dalton Lathe last year. Couldn't be happier with the Dalton. It's a tight little machine, and a wonderful workhorse. Cuts like butter and "dances like a Bee", as Ali used to say! It's my scalpel. Whereas my old Standard modern 12 x48" big iron machine can take .250" DOC and reduced the axle blank diameters in no time, this little Dalton did the finish work like a champ. Close tolerance, fine finish, easy to work tight corners and edges . Just a lot of fun using it to turn these parts down to size... And, the drive dog in the picture, which I bought on eBay for this purpose, is stamped 'USAAF' for US Army Air Force. So I imagine, it had a lustrous career in WW II keeping bomber command, or maybe some fighter wing, in the air.
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Next step, Fab up the wheel housings and mount the axles.

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....

John Landrum
Posts: 30
Joined: Fri Feb 17, 2017 2:05 am

Re: Turntable design

Post by John Landrum » Sat Mar 04, 2017 9:04 pm

I have not built the turntable for my 18' gauge yet, however, I did have a hand in designing the full size turntable we use at McKinney Ave. Transit in Dallas to turn some of our streetcars which are single ended. You must have a center pivot.

In a turntable, most of the weight is taken by the center bearing and the side bearings are simply there to balance and guide. We figured that over half the weight of the car (around 26 tons total weight for a large car) is taken by the center bearing. Our turntable pit is 15' deep, the foundation for the center bearing is 20 feet deep and the turntable itself is fabricated out of an old, 40' Southern Pacific Railroad bridge. Irwin Car and Equipt. built the side bearing wheels for me and the ring rail is 90# #1 relay rail, custom rolled.

Now back to our gauge stuff,
Your center bearing is critical and the foundation, as Carl noted, is critical as well, as is soil conditions, moisture, etc. I recall Colonel Elliott Springs used civil war cannon balls as the center pivot for his turntable on the Lancaster and Chester line he built at Springs Park. I believe they ran 15" Class D Cagney's.

On the yahoo 18" forum, there were a bunch of guys talking about turntables. Then they fell to talking about using two 1/2" steel plates, greased up on the sides that faced each other and the rails welded to the top plate! "Yeah Bubba, that oughta do it" At that point, I quit paying attention and fled shrieking into the night. Thank goodness I found this site where engineering and prototype construction seems to matter!

A unique turntable was built by the late Terry McGrath for his 7 1/2". He used an old gas station hydraulic lift. The steaming bays were all at one height, but various peoples trailers were at different heights, as was the throat track and the engine house track. This allowed the turntable to be swung or pivoted on the central cylinder and then raised or lowered with air to the require height!

By the way John B., gorgeous gallows turntable, well done!

John Landrum

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ccvstmr
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Location: New Lenox, IL

Re: Turntable design

Post by ccvstmr » Sun Mar 05, 2017 4:07 pm

Hey Glenn...sorry, don't flame me because of this...but if you have a center pivot turntable...why do you need double-flanged wheels for stability? ...why do you need flanged wheels at all? Just need something to support the ends of the turntable when equipment rolls on/off the table. It's one thing to use parts that have been laying around...it's another when it comes to the KISS principle. Just curious.

Find attached a photo from the Orange Empire RR Museum in Perris(?), CA. Don't think any of the rollers had flanges...those used on the internal or external wheel rings. Suspect you don't want to make your flanged rollers blind either. Keep the posts coming. Carl B.
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Glenn Brooks
Posts: 1453
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Turntable design

Post by Glenn Brooks » Sun Mar 05, 2017 8:13 pm

Hi Carl and John,

John, yes, agree the center pivot is critical for turning operations. I've learned a lot about the underlining engineering of these things through this thread and some very able comments and advise, such as you posted. Thanks! Interestingly, I did learn that early day railways did somethimes build turntables without center pivot points. However they only worked well prior to the 1860's when the early day, light weight 4-4-0 Americans were common. Never found any surviving engineering data or even construction detail, just a few historical mentions. Anyway, a good pivot point certainly is the way to go. One of our old time master machinist guru's at our local Kitsap Live Steamers just donated three actual heavy duty 6" roller bearing assemblies for the pivot. So am preparing to bore out my existing socket and pin bearing assembly and re-fit the bearing. Although with the light loading we see in miniature railway operation, even at 12" gauge, a friction bearing and pin arrangement sees to work well.


Carl, Cool photo of the turntable at the museum in Ca. There aren't many detailed photos of turntable designs available on the internet. Yours has a very interesting view of the pivot supports and deck construction. Thanks for posting!

Very good question regarding the wheels. The main reason I am using the flanged wheels is that the old, original turntable was made with them. So I had these wheels on hand and thought it would be interesting to incorporate their use. When I dug the old turntable out of the rainforest -literally it was buried several feet deep under 30 years growth- green moss, ferns, and deadfall, I discovered the table itself was made from a single 16"x 14' old growth fir beam. Sadly the beam and all the metal fittings and brackets were rotted and decayed beyond use. Only the wheels were salvageable. The tread on these wheels are quite large, actually around 3" wide, and the width of 12# rail is around 1". So, under normal operation I don't expect the flanges will ever see any wear- they are just there for safety and describe the wheel form better.

Second reason is the turntable itself will do double duty as part of the mainline. Unlike most turntables, this one will be integral to the mainline track that I am able to lay around the back yard. For safety I want the ends - supported by the wheels and the rail edges at the foundation to carry the weight and offer stability and resistance when a train consist of four or five cars passes over at mainline speed. Essentially, when not shuttling cars onto the sidings, the turntable will will function as a rotating bridge. So in this sense, I plan on having three significant points of support, two on the ends and one at the pivot, versus the more traditional center pivot balance point common to standard designs. This is an odd use for a turntable, but I don't have room on my lot for any other approach.

And also, to further safety, I initially envisioned the flanges could help mitigate against the turntable ends derailing and tipping the loaded cars, neighborhood kids, and engine down into the pit in the event of some sort of accident.... :shock: :shock: :shock:

One thing I didn't think about in the beginning, but now might prove to be the most important benefit is - the flanged wheels have a curved tread design. The tread flares up to the flange on both sides, similar to a standard wheel tread contacting the head of the rail. I now suspect this dual curvature might help guide the tread of the wheels around the curved ring better, if I don't get the angle of curvature on my end mounts just right.

Anyway, those are my main reasons for going with the flanges...

Cheers,
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....

K. Brouwers
Posts: 22
Joined: Wed Mar 21, 2007 11:57 am
Location: Philippines

Re: Turntable design

Post by K. Brouwers » Mon Mar 06, 2017 8:19 am

Hello Friends,

May I suggest a peek at the turntable built by the WW&F railroad Museum
http://forum.wwfry.org/index.php?topic=2628.0

John Landrum
Posts: 30
Joined: Fri Feb 17, 2017 2:05 am

Re: Turntable Design and Build

Post by John Landrum » Mon Mar 06, 2017 9:18 pm

Hey Glenn,

If it weren't for the file size, 4.8 MB, I would post some photos I shot last summer of the remains of the turntable on Otto Mears Silverton Railroad which headed North out of Silverton. It was unique in that it had a turntable in the middle of the main line to get around the fact that they needed to change direction and did not have enough room for traditional methods. Most of the wood is gone but there is quite a bit of the iron bits left including the turnbuckles, center pivot and guide wheels. Very cool!

I am not certain that the double flanges will be necessary to keep the train from falling into the pit as the turntable is basically captive inside the pit walls. The center pivot keeps it from turning over and, with each end up against the pit walls there is really no where for it to go.

For grins I post here a picture of some of the pit wall for my 12" to the foot turntable as it was being built a few years ago.

John
Attachments
TT.jpg

Glenn Brooks
Posts: 1453
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Turntable Design and Build

Post by Glenn Brooks » Mon Mar 06, 2017 9:57 pm

John, that that is some serious work! Iam curious. What sits underneath grade to require so much depth in the prototype? At 15' depth of pit, what is themo everall diameter of the center casing/pivot

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....

John Landrum
Posts: 30
Joined: Fri Feb 17, 2017 2:05 am

Re: Turntable Design and Build

Post by John Landrum » Wed Mar 08, 2017 1:37 am

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Glenn, This is what sits in the turntable pit. A 40' long southern pacific railroad bridge. The center pivot is about 6' in diameter and the gear case and drive unit are affixed to that about 7' below the bottom of the bridge. The entire structure is below ground because the generous folks who were footing the bill for this project wished it so. The entire deck of the turntable which covers the pit, rotates with the turntable.

John Landrum
Posts: 30
Joined: Fri Feb 17, 2017 2:05 am

Re: Turntable Design and Build

Post by John Landrum » Wed Mar 08, 2017 1:42 am

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This is the gear case and drive motor which sits on the center pivot foundation. It is connected to the turntable structure by what I believe is called a, "torroidal" collar (probably misspelled) which is basically a flexible disk fastened to both the drive shaft and the underside of the bridge.

John Landrum
Posts: 30
Joined: Fri Feb 17, 2017 2:05 am

Re: Turntable Design and Build

Post by John Landrum » Wed Mar 08, 2017 2:02 am

City Place TT.jpg
Here is the completed turntable with one of our small cars sitting on it.

Glenn Brooks
Posts: 1453
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Turntable Design and Build

Post by Glenn Brooks » Thu Mar 23, 2017 11:01 pm

John, thanks for adding your photos and additional details describing the pit and drive unit. Very impressive. Iam curious - is the deck supported on the rail, at the edges - or cantilevered out from the edge of the bridge structure?

The decking is way cool. Must resist... ideas... to add to my little contraption.

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....

Glenn Brooks
Posts: 1453
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Turntable Design and Build

Post by Glenn Brooks » Tue Mar 28, 2017 1:15 am

Fabricating the wheel mounts for the table ends. I milled and spot welded one mounting assembly for the prototype today. Seems to work just fine. Will finish off the other three tomorrow. The key feature for each mount is a slotted 1/2" bolt hole on the side plates that will allow me to separately adjust the height of each wheel to fit the track. I want the turntable ends to sit solidly on the rail, even if the structure is not dead parallel to the ground, or if the turntable foundation shifts and settles during our annual surface water winter hydronic cycle. The slots allow the wheels to move about 2" up and down, as needed.
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Prototype wheel housing - spot welded, with bearings and wheel/shaft installed. Three more to go...
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Front view
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Bottom view
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Milling the slot in the side plates.
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Cool little milling fixture that holds multiple parts on the center of the rotary table.
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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