Hi guys,
In a previous thread I posted photos of my HO turntable converted to handle my S trains. I know that it's semi-automated indexing is at 10 degrees, and I can index it manually if needed.
I have a three stall S turntable, and have been trying to figure out how far to place the roundhouse from the turntable. Is there a way to calculate this number or is it all about trial and error. I can't seem to find any information on this.
As for wiring how do you guys wire the roundhouse tracks? I have seen rotary switches, but really don't have a clue where to start, so any help would be appreciated.
Thank you,
George
John Armstrong's book "Track Planning for Realistic Operation" has some useful hints on turntables and roundhouses.
As far as wiring, we just used a regular on-off toggle for each track. You could use a rotary switch, but I think you would need to couple that with an on-off toggle for the whole business (so you can actually turn the whole block off, rather than shunting power to one track or the other).
nickaix,
First let me thank you for your response, this project is a seat of the pants deal and I need all the help I can get. I can't believe this, but I was at the LHS yesterday, and glanced at that book. I didn't look at it well enough, becasue I never thought about looking for turn table wiring.
Sounds like a trip back there tomorrow may be in order.
Thank you and Happy Thanksgiving,
You don't need to combine an auxiliary SPDT switch with a rotary switch. Just use a rotary switch with at least one more position than you have tracks. That position (or positions) becomes the "off" position.
Bob Nelson
Bob,
Thank you, I guess that makes sense, if I set the switch to a position that has nothing conected to it, it would be the same as off.
Ok, here you will see what an electrical novice I am. If I wire the inbound power to the selector switch, from the same feed as the lead track to the turntable, does that give me what I need?
Then each outbound track from the turntable to the roundhouse is fed from another position on the rotary switch?
For operation run the locomotive up the lead in track and onto the turntable. Then cut the power backto hold the locomotive on the turntable. Operate/rotate, the turntable to the desired roundhouse track, and re-apply power to the turntable to back the locomotive into the stall.
All corrections and comments welcome,
I think you've got it. Remember that you need to switch only one rail of each roundhouse track. The other rail can remain connected to the corresponding rail of the track leading to the turntable.
Hi Bob,
Thanks again for the help, I am planning to switch the hot side, not the base side. That is unless someone thinks it is better to switch the common side.
Now back to the mechanical end of things. I have posted some photos below, please no comments on my staging, I do plan to build this into my layout, just as soon as I figure out what I am doing. Right now I am trying to get this spacing between the roundhouse and the turntable right, so I can figure out placement on the layout.
This fist photo shows the roundhouse about as far away from the turntable as I can get it, and still have room for the three tracks. In fact at this distance I need to trim the AF roadbed a little to get the tracks straight. This one is straight in, pretty easy stuff.
The next photo is the round house stall to the right of center, as you can see the track does not line up straight.
And finally this photo shows the track to the left of the center stall, it is also not straiight.
I think the photos show that the tracks do not seem to align very well, and it gets worse the closer the roundhouse is to the turntable. Seems to me for something realistic looking the roundhouse needs to be further away from the turntable.
So what might be a better approach, pun intended.
George,
This may be in bad form, but you really need to visit the other O-Gauge forum(I know you're an S-scaler) and do a search for Roundhouse/turntable spacing. Dave Hikel over there is as knowledeable on that subject as Lionelsoni is about electronics.
In a nut shell, there is a formula for figuring the proper distance of the roundhouse from the turntable CENTER. You need to know the spacing, in degrees of the stalls of your roundhouse, and the width of the stalls, with those you can figure the proper setback for the roundhouse, for every thing to line up straight and centered.
Dave is as helpful as Bob is, when it comes to Helping fellow modelers figure their placement. It seems very complicated and confusing, but Dave will make it seem simple.
The answers to your questions are out there Grasshopper, you just need to look, where they are to be found,
Doug
May your flanges always stay BETWEEN the rails
Hi George,
Doug dropped me an e-mail and alerted me to your quandary. The critical measurements we need to know to calculate the natural position of your roundhouse are the stall width (measure the brick wall around each door) and the angular spacing between each stall. If you don't know the angular spacing we can figure it out by measuring the length of the stall and the width of one stall at the back wall.
Just from looking at your photos it seems like the roundhouse needs to sit back farther from the turntable. The angular spacing between each stall seems VERY narrow. It's certainly a lot less than the 10˚ you mentioned for the auto indexing. If that's the case you won't be able to use the auto indexing with this roundhouse.
Post some measurements and we can figure this out.
For those looking to do the calualtion for their own project, there's a great website with a circle segment calculator that can give you the info you need: The Complete Circle Calculator Be sure to change the measurement settings from feet to inches. Input the stall width as the "width" of the circle segment and the angular stall spacing as the "angle subtended by arc" and press "calculate." The "apothem" generated will be the distance from the center of the turntable (not the pit wall) to the front doors of the roundhouse.
Doug,
Good morning, and thank you for your reply, and for contacting Dave. I really appreciate your help. I was have dropped an email to Twin Whistle last night, asking about the stall angle on this roundhouse but haven't heard back yet.
Dave,
Thanks for your response, I will go and play with that link you provided, in the interim, I have posted all the dimensions below:
Front width of stall - 3.25
Depth of roundhouse - 21.5
Rear width of Stall 5.5
The width of the opening is 2.75, I agree it seems very narrow and not anywhere near the 10 degrees of the turntable. The indexing feature is not a must have. In the photos I had placed the roundhouse about 17" from the center of the turntable deck.
Thank you in advance for your assistance,
Great site, I gave it a try and if it did it correctly the stall angle is 8.66 degrees and the apothem is 21.43 inches.
I willl set up my test platform and give it a try. I don't think I am going to be able to use the roadbed, as even with yesterdays 17 - 18 inch spread the roadbed was going to need trimming to the width. I'll try ther track without the roadbed and see how it works out.
Thank you again for your help, this is great information.
I make the distance from the front to the center of the turntable to be 31 inches and the spacing to be 6 degrees. Here is my reasoning:
The width of the stall is proportional to the distance from the center. It changes at a rate of (5.5-3.25)/21.5 = 2.25/21.5 = 9/86. So, if the front is R inches from the center, the width of the front is R*9/86 = 3.25. So R = 3.25*86/9 = 31.0555. The stall angle in radians is very nearly the chord, 3.25, divided by the radius R, or .104651. In degrees, this is 5.996. (An exact calculation of the angle gives 5.991 degrees.)
The tracks, as with a prototype turntable, will probably be very close at the circumference of the pit, possibly with the rails touching. It's unlikely that there will be room for roadbed; and the ties will probably have to be staggered. What is the pit diameter? From the stall spacing angle and the diameter, we can calculate the track spacing at the rim.
It's no wonder I wasn't getting anywhere just moving the roundhouse back and forth, and trying to site the track lines. The pit diameter is 19 inches.
I am off to finish waxing the wife's car, which I started on wednesday before the thanksgiving celebration. I will be back on-line later.
Thank you again,
Okay. Nineteen inches in diameter means a 9.5-inch radius. So 9.5*9/86 gives a track spacing of .994 inch at the rim. S gauge is 7/8 inch, so this leaves .119 inch between the inside surfaces of the rails, which is probably very close to the width of the railhead. That means that you're going to have to shave a little off the outsides of adjacent rails where they meet at the pit.
Electrically, this could be a problem, since one rail will be common ("base"), while the one touching it will be "hot" unless you can insulate those rail slivers from each other. A better solution would be to solder them together and bite the bullet to use a two-pole rotary switch to select the track--despite what I posted above about only needing a single-pole switch.
If you're only going to have those three stalls, you might be able to cheat a little and swerve the outer two tracks away from the middle one and then back into a radial alignment with the turntable.
It could be worse--you could have needed frogs where the tracks meet!
Well that all seems rather tight for the stall tracks, I would agree. And needing 31 inches from the center of the pit to the front of the roundhouse means an awfull lot of real estate for a three bay roundouse.
Now given my the new education that you and Doug and Dave have provided, I am considering cutting up the roundhouse and rebuilding it. I think I may purchase 2 more bays and put it together increasing the stall angle to 10 degrees. I think I can do this by adding spacers between the front wall of each stall. The story of why this roundhouse is only 6 degrees follows.
I bought this roundhouse from ebay, a kit someone had started and never finished. When I say started I mean the instructions state to bevel the edges of the resin castings. When I got the kit they had some pretty strange angles. As I tried to fit them together I sanded more thereby further narrowing the with of the front wall castings. I am going back to the calculator and work on some modifications.
Thank you as always,
I am Happy that I was at least able to help you find the info you needed. Both Bob and Dave have been Very Valuable assets to the forums, both have helped me a lot in the past.
I have thanked you many times, and I Hope you never tire of helping those of us, for whom electrical theory isn't second grade recess games, as it is for you.
I've not had a chance to THANK YOU yet, your website's instructions on wiring the MTH Scale Grade Crossing Gates was a HUGE help. Once I read about the DZ-1008A relays and found some, the schematic your site has, made the wiring simple(3-6 inches more wire on those gates would have really helped, but that was MTH's doing, not your's). The MTH 3 color signal wiring schematic, worked perfectly for my MTH operating Semaphore as well. Thank You again as the 2 sets of gates and the Semaphore really added to my Halloween display layout(my Wife and the Kids Really loved the gates)
You can increase the track spacing to 10-degree steps by keeping the stall fronts at the same width, keeping the stall depths at 21.5 inches, and extending the width of the back walls to 7.012 inches each. The fronts of the stalls would then be 18.574 inches from the turntable center; and the track spacing at the rim of the pit would be 1.662 on centers
Doug, thanks for the kind words. It's nice to know that people are making good use of those wiring diagrams.
George, I think Bob has the right idea for your situation. The roundhouse doors do need to sit 31 inches from the center of the TT. Since that won't fit for your space your best bet is to do some surgery and change the geometry of the roundhouse. If you increase the angle of each stall to 10˚ by adding to the back wall but keep the 3.25 inch front walls that would change the setback to 18.5 inches from the TT center. That would give you 9 inches from the TT pit to the doors. It also has the benefit of improved track clearance near the pit.
Hope that helps.
Bob, Dave,
I am confused, as I was thinking I needed to make the stall fronts wider in order to spread the tracks farther apart at the front of the pit. This in combination with making the rear of each stall wider would be a way to possibly get to a 10 degree stall angle. But Bob your numbers look real good.
As I look at the photos I posted, it seems to me that by making the stalls wider in the back of the roundhouse the tracks would be even closer together at the front of the pit. But I will have to set up the pieces on a table and check it out with your suggestions. I am also looking at aquiring one or two add on stalls. If I am going to perform surgery I might as well make it a little bigger.
In the photos shown I have about 8 inches between the front of the roundhouse and the edge of the pit, and 17 inches from TT center to the front of the roundhouse. So this is close to your calculations based on increasing the width at the rear of each stall. This sounds way better that 31 inches.
Thank you both for your continuing help,
If you make the front walls wider that will have the effect of pushing the roundhouse farther away. I would stick with just widening the back wall.
When you increase the angle of each stall but keep the front wall width the tracks do converge faster as you move away from the RH. However, you need to think of how the tracks come off the TT. Tracks that are 6˚ apart will always be closer together than tracks that are 10˚ apart. So how can both be true? As the stall angle increases the distance from the RH to TT pit wall is decreasing faster proportionally than the distance from the RH to the TT center. It's VERY counter intuitive, but it works.
Hi, been getting home from work late and haven't been able to set up my TT and Roundhouse yet. I hope to get to that before the weekend. I can follow what you are explaining , but as you say it does seem counter intuitive.
I am looking forward to getting back to this, and my Dremel tools are ready for surgery.
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