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Distance from Turntable to Roundhouse, Walthers

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Posted by BATMAN on Monday, July 19, 2021 3:02 PM

richhotrain
That would surprise me if the roundhouse instructions specified the distance because the radius of the turntable is part of the forumula, so the rounhouse specs would have to account for different size turntables such as 130', 110', 90', etc. Rich

As I said in my first post.

BATMAN

Well, this is a lot of discussion for something so simple. The instructions I read were if you were using a **** size turntable install RH tracks so they stick out **** inches from the front edge of the roundhouse floor. That is what I did and the fit was perfect.

 

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1/videos 


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Posted by richhotrain on Monday, July 19, 2021 3:34 PM

BATMAN
 
richhotrain
That would surprise me if the roundhouse instructions specified the distance because the radius of the turntable is part of the forumula, so the rounhouse specs would have to account for different size turntables such as 130', 110', 90', etc.  

As I said in my first post. 

BATMAN

Well, this is a lot of discussion for something so simple. The instructions I read were if you were using a **** size turntable install RH tracks so they stick out **** inches from the front edge of the roundhouse floor. That is what I did and the fit was perfect. 

I'm not sure where we are going with this.

You can't find the instructions that you read and you don't know where to find them. I looked at my instructions and template and there is no reference to distance specs.

So, apparently, it is not so simple.

But it doesn't matter because once I printed Ed's formula from my older thread, an exact distance was finally provided to the OP.

Rich

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Posted by Bayfield Transfer Railway on Monday, July 19, 2021 4:08 PM

Now to muddy the waters.

If the distance from the roundhouse to the turntable is long enough, you will get the tracks overlapping and there will be frogs in the approach tracks.  Ashland, WI on the NP was one example of such, and there are others.

 

Disclaimer:  This post may contain humor, sarcasm, and/or flatulence.

Michael Mornard

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Posted by gmpullman on Monday, July 19, 2021 4:26 PM

Bayfield Transfer Railway
If the distance from the roundhouse to the turntable is long enough, you will get the tracks overlapping and there will be frogs in the approach tracks.

Right.

Here's an example, C&NW in Chicago:

 CNW_RHcrop by Edmund, on Flickr

The LS&MS turntable at Ashtabula is so arranged that each rail has to be joined to the next, almost employing a "half-frog":

 New York Central Railroad Ashtabula Roundhouse Turntable by Ashtabula Archive, on Flickr

Regards, Ed

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Posted by SeeYou190 on Monday, July 19, 2021 6:01 PM

gmpullman
The LS&MS turntable at Ashtabula is so arranged that each rail has to be joined to the next, almost employing a "half-frog":

Now that would be a trick to wire so it worked right!

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by JDawg on Monday, July 19, 2021 6:05 PM

SeeYou190

 

 
gmpullman
The LS&MS turntable at Ashtabula is so arranged that each rail has to be joined to the next, almost employing a "half-frog":

 

Now that would be a trick to wire so it worked right!

-Kevin

 

 

More like a Nightmare!

 

Thanks for all the help guys. 

JJF


Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing. Smile, Wink & Grin

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Tomorrow is a Mystery.

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Posted by BATMAN on Monday, July 19, 2021 8:19 PM

SeeYou190
Now that would be a trick to wire so it worked right! -Kevin

HOLY FROG JUICERS! 

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1/videos 


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Posted by Lastspikemike on Tuesday, July 20, 2021 9:41 AM

richhotrain

 

 
Lastspikemike

The resulting distance has nothing to do with the size of the turntable. 

The smaller the turntable the longer the tracks will be. 

 

 

Aren't those two statements contradictory?

 

 

The footprint of the turntable and roundhouse are determined by the roundhouse stall angle and length. The turntable size is not relevant to the calculations you need to make. If the turntable needs to be (edit) smaller than ideal because the roundhouse stalls are very long or the operator wants long tracks in front of the roundhouse doors for some reason then connecting tracks could connect or cross, unless you also  change the stall angle. 

Put another way: you don't need to know the length of the connecting tracks between the edge of the turntable and each roundhouse doorway. That number doesn't help you locate or install the roundhouse and turntable.

You just cut those connecting tracks to fit after the roundhouse and turntable are in place just as you would for any layout.

No complex calculation is required. The roundhouse location determines where the center of the turntable must go which in turn requires a certain length of connecting tracks. You never need to calculate the length of those connecting tracks. 

Alyth Yard

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Posted by SeeYou190 on Tuesday, July 20, 2021 10:13 AM

BATMAN
HOLY FROG JUICERS! 

At least a few hexes!

Laugh

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Tuesday, July 20, 2021 10:57 AM

Lastspikemike
 
richhotrain 
Lastspikemike

The resulting distance has nothing to do with the size of the turntable. 

The smaller the turntable the longer the tracks will be.  

Aren't those two statements contradictory? 

The footprint of the turntable and roundhouse are determined by the roundhouse stall angle and length. The turntable size is not relevant to the calculations you need to make. If the turntable needs to be bigger than ideal because the roundhouse stalls are very long then connecting tracks could connect or cross, unless you also  change the stall angle. 

Put another way: you don't need to know the length of the connecting tracks between the edge of the turntable and each roundhouse doorway. That number doesn't help you locate or install the roundhouse and turntable.

You just cut those connecting tracks to fit after the roundhouse and turntable are in place just as you would for any layout.

No complex calculation is required. The roundhouse location determines where the center of the turntable must go which in turn requires a certain length of connecting tracks. You never need to calculate the length of those connecting tracks.  

I guess that the answer to my question was Yes. ConfusedConfused

Alton Junction

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Posted by snjroy on Tuesday, July 20, 2021 12:09 PM

Hi there. This is what I got when I purchased the 90' turntable - or was it the roundhouse??? Anyway, it says that this applies to both the modern and regular Walthers roundhouse. I can't find it on the Walthers Website. Maybe the model was changed or there was a mistake... Anyway, here it is:

 Walters 90 footprint on Flickr

Simon

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Posted by SeeYou190 on Tuesday, July 20, 2021 1:00 PM

snjroy
Hi there. This is what I got when I purchased the 90' turntable - or was it the roundhouse?

SeeYou190
That should give you about 5 1/2" of track between the turntable and the roundhouse (if my math is OK).

Hey, I was only off by 7/16" with my estimate. Not too shabby.

Cool

Thanks for posting the drawing Simon.

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Tuesday, July 20, 2021 1:39 PM

snjroy

Hi there. This is what I got when I purchased the 90' turntable - or was it the roundhouse??? Anyway, it says that this applies to both the modern and regular Walthers roundhouse. I can't find it on the Walthers Website. Maybe the model was changed or there was a mistake... Anyway, here it is:

 Walters 90 footprint on Flickr

Simon

 

This may be what Brent was referring to. I have the original 130' non-DCC turntable, and there are no distance measurements from the turntable to the roundhouse.

Rich

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Posted by BATMAN on Tuesday, July 20, 2021 1:40 PM

snjroy

Hi there. This is what I got when I purchased the 90' turntable - or was it the roundhouse??? Anyway, it says that this applies to both the modern and regular Walthers roundhouse. I can't find it on the Walthers Website. Maybe the model was changed or there was a mistake... Anyway, here it is:

 Walters 90 footprint on Flickr

Simon

 

Yes, this is what I got as well, I did not have to use my poor B+ grade 12 math skills. Just remember the track goes to the pit edge, not the edge of the lip so that is likely how I ended up with 30cm, pit centre to front edge of the RH.

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1/videos 


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Posted by richhotrain on Tuesday, July 20, 2021 1:44 PM

You may have been closer than that, Kevin, since that measurement is from the outer lip of the turntable, but the connecting track needs to reach the pit to connect to the bridge track. So, the connecting track would be about 5.775".

Rich

 

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Posted by Lastspikemike on Tuesday, July 20, 2021 2:28 PM

Just a reminder to other readers trying to use all of this information: 7/16" is basically half an inch. That's a big gap.

And approximately isn't going to work when actually fitting the track. I fit my joints pretty much with no gap at room temperature. No matter how accurately you try to cut and fit there will always be a bit of a gap somewhere big enough to accommodate thermally induced rail length changes. 

Use the same techniques to cut and fit roundhouse connecting track as you would for any track fitting. You don't need to know how long the track needed is, just use a piece long enough to cut to fit. You could cut all the pieces from just one instance.  They all should be exactly the same but only if you're  very accurate in your placement of the roundhouse and turntable. Mind you, using lengths of connecting track all cut exactly the same from the one example should orient your roundhouse to the turntable very accurately.

Alyth Yard

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Posted by SeeYou190 on Tuesday, July 20, 2021 2:29 PM

richhotrain
You may have been closer than that, Kevin

Woo Hoo!

Kevin for the win!

Idea

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by gmpullman on Tuesday, July 20, 2021 3:13 PM

Lastspikemike
No matter how accurately you try to cut and fit there will always be a bit of a gap somewhere big enough to accommodate thermally induced rail length changes.

Well, honestly, I really didn't give much consideration to thermal expansion on a 130' turntable.

I simply left each rail about a quarter inch (6.35 mm) longer than necessary then trimmed each one after the roundhouse was set in place.

 Pit_Rail by Edmund, on Flickr

Once trimmed and filed I set the base of each rail into a dab of epoxy. This is my second, nine-stall roundhouse at this location. The turntable and original Heljan roundhouse was installed in 1995.

 Pit_Rail_crop by Edmund, on Flickr

You can see that there is a bit of a gap in the closest track. This was easily pulled down (weighted) once the rail ends were trimmed and filed (a slight relief was filed into the gauge-side of the rail head) and a bit of epoxy was applied.

The 'new' roundhouse has been in place since April of 2018 and has not shown any signs of misalignment or thermal activity.

Good Luck, Ed

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Posted by richhotrain on Tuesday, July 20, 2021 5:52 PM

Lastspikemike

Just a reminder to other readers trying to use all of this information: 7/16" is basically half an inch. That's a big gap.

Before we all get lathered up about a 7/16" gap, let's recall that the 7/16" measurement was a guesstimate between Pruitt's indication that the dimension from the center of the turntable to the doors is 11 15/16".

Kevin indicated that the 90 foot turntable bridge is about 13" long, or 6 1/2" to center. That should give you about 5 1/2" of track between the turntable and the roundhouse.

Turns out, the exact distance was 5 1/16", or 7/16" difference. Not bad for a guesstimate. After all, JDawg's original estimate was 12". That's the beauty of the formula - - exactness.

Lastspikemike

Use the same techniques to cut and fit roundhouse connecting track as you would for any track fitting. You don't need to know how long the track needed is, just use a piece long enough to cut to fit. You could cut all the pieces from just one instance.  They all should be exactly the same but only if you're  very accurate in your placement of the roundhouse and turntable. Mind you, using lengths of connecting track all cut exactly the same from the one example should orient your roundhouse to the turntable very accurately. 

And that is why the forumula is so useful. It tells you the exact distance between the edge of the pit on the turntable and the front floor of the stalls.

In fact, once the formula provides the exact distance, that measurement can be used to perfectly align the roundhouse with the turntable.

Each and every connecting track will be the exact same distance whether the outermost stall or the middle stall or any other stall in between.

The shortcoming of your two-line theory is that it fails to identify that exact distance. It only tells you the distance from the centerpoint of the turntable to the round stall floor. You still need to know the radius of the pit to determine the exact length of the connecting track - - every connecting track.

Alton Junction

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Posted by Lastspikemike on Tuesday, July 20, 2021 5:53 PM

My point was about the size of any rail joint, not at turntables specifically. The rail gap between the turntable and connecting track has to be wider than would otherwise be correct in order to accommodate the swing of the gauge. The base of the ends of the rails on the bridge will conflict with those on the connecting tracks. That gap needs to be accurately made.

Sure, if you can measure accurately, allow for the necessary gap and cut all rails exsctiy the same and then position the roundhouse exactly correctly you might use a formula to calculate the cut length of your connecting tracks.

I remain sceptical. I plan to use my simple method to install my turntable and roundhouse. I'll let you know how that goes if and when we get around to it. So far we just have two paper templates. One circle and one wedge shape. 

Alyth Yard

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Posted by richhotrain on Tuesday, July 20, 2021 5:58 PM

Lastspikemike

And approximately isn't going to work when actually fitting the track. I fit my joints pretty much with no gap at room temperature. No matter how accurately you try to cut and fit there will always be a bit of a gap somewhere big enough to accommodate thermally induced rail length changes. 

Truth be told, there will always be a gap between the bridge rails and the rails on the connecting track, no matter how infinitesimal. If there weren't, every time the bridge track rotated across a connecting track, it would snag unless the cut were so exact that only a slight gap of paper width were made at the end of the connecting track. 

Alton Junction

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Posted by richhotrain on Tuesday, July 20, 2021 6:03 PM

Here is a good takeaway when installing a turntable and roundhouse. 

Once you determine the length of the connecting tracks by using the formula, you now know the approximate space required to install the turntable/roundhouse complex.

Then, you can install the turntable. Once that is done, you can finesse the roundhouse into place by aligning both ends of the front of the roundhouse to the exact distance determined by the formula, after taking into account the fact that the connecting tracks need to extend over the lip of the turntable to the edge of the turntable pit.

Next, you can install the connecting tracks, all cut to the exact length determined by the formula.

Finally, you can test the rotation of the turntable bridge to see if the ends of the connecting tracks need to be filed to permit proper rotation of the turntable bridge.

Rich

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Posted by RR_Mel on Tuesday, July 20, 2021 8:24 PM

JDawg

I am trying to plan for a roundhouse/turntable on my condo layout. I am looking at the walthers 90ft and the matching roundhouse. How much space is there between the Turntable and the roundhouse. My calculations show about a foot between, but that seems extreme. How much space should I plan for?

 

I want to thank you for this topic!!!!  That gave me the incentive to draw up a couple of to scale top view drawings of my articulated locomotives.  I’ve been wanting to do that for several years.



The two locomotives are 18”+ and fit my kitbashed/lengthened Korber Roundhouse nicely.



Mel



 
My Model Railroad   
http://melvineperry.blogspot.com/
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.

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Posted by SeeYou190 on Tuesday, July 20, 2021 11:51 PM

RR_Mel
That gave me the incentive to draw up a couple of to scale top view drawings of my articulated locomotives.  I’ve been wanting to do that for several years.

Nicely done.

I like the cab forward and cab normal graphics.

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Wednesday, July 21, 2021 6:46 AM

Lastspikemike

I remain sceptical. I plan to use my simple method to install my turntable and roundhouse. I'll let you know how that goes if and when we get around to it. So far we just have two paper templates. One circle and one wedge shape.  

Remaining skeptical is a good sign in that it indicates that you might be persuaded otherwise. So, we look forward to learning the results of your approach.

Since you indicate that you have two paper templates, a circle and a wedge shape, you have already improved upon the two-line approach by adding in the radius of the turntable pit.

I assume that the wedge shape is the stall floor and that the circle represents the circumference of the turntable pit. Without that circumference, you don't know the radius, so you don't know how far to place the roundhouse from the turntable.

Alton Junction

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Posted by Lastspikemike on Wednesday, July 21, 2021 8:23 AM

My view is that the roundhouse is located first. Messing around with the two templates revealed this to us. You don't actually need a turntable template. A tape or meter stick will tell you if there's enough room for the turntable. We cut the turntable circle template not realizing we didn't need one. You do need to allow for the turntable approach track(s). We quickly discovered that the length of this approach track is the most likely limiting factor for fitting in a roundhouse. 

Place the roundhouse, draw two lines (or three if you're a woodworker, always three) and that marks the center of the turntable. Cut your turntable hole using that center for whatever circle cutting guide you are using.

Presto, the length of the required connecting tracks  can be measured directly on the layout. 

Allow a fudge factor of say 1/2" to finally locate the roundhouse after you actually cut the hole for the turntable allowing for cutting errors. The stall angles require the roundhouse to be exactly x" from the turntable. Cut those connecting tracks to fit leaving the required larger than usual gap between the bridge track ends and the connecting track ends. I think Walthers recommends tapering the inside edges of the turntable ends of the connecting track rails to facilitate transit of the locomotive wheels across these gaps. 

We'll find out if all this works.

Alyth Yard

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Posted by SeeYou190 on Wednesday, July 21, 2021 8:28 AM

gmpullman
Well, honestly, I really didn't give much consideration to thermal expansion on a 130' turntable.

I do not give thought about thermal expansion to anything.

My layouts have always been in the climate controlled section of the house, and this is not a factor.

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Wednesday, July 21, 2021 8:28 AM

Always position the turntable first.

Alton Junction

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Posted by SeeYou190 on Wednesday, July 21, 2021 9:05 AM

richhotrain
Always position the turntable first.

Agreed, and then using a laser like Ed showed in his pictures looks like that would make roundhouse alignment right on the money very easily.

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by RR_Mel on Wednesday, July 21, 2021 10:45 AM

I’ve built five turntable/roundhouse combinations over 50 years and installing the turntable first works out far better.  Four were scratch built turntables.

This is my last scratch built turntable bridge & superstructure in 1992.



My final turntable is a 135’ CMR kit which really works great.



The CMR turntable did not come with the superstructure so I did my scratch build thing using a Central Valley Bridge & Girders 1902-5 kit.





I used the October 1989 MR Centerfold as a go by.


 
Mel



 
My Model Railroad   
http://melvineperry.blogspot.com/
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.

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