Roof-less Roundhouse

I got delayed working on these 2 structures,...but this morning i ran across this image of a roof-less roundhouse,...definitely going to consider this approach

Another consideration

Turntable pit

Hey Brain, I have one of those. Does it work ok? if it does I would just put some task board around the outer side of pit and tape or hot glue it to keep it tight and gently open the cracks with hobby knife and put some plaster in the gaps. The board it came on is probably warped. Don't know if epoxy will work on hydrocal.   God Bless Ya   Dave 

Turntable

Here are about the best photos i could get of the warp-age of the turntable pit itself,...the discolored area in the first picture appears to be where it got wet, but I don't know how it happened,...

 

I decided to try bolting it back into its original place on its deck cutout of heavy plywood. Here you can see 4 good size bolts and nuts flattening the warp out to a significant degree,..
 

[attach:fileid=424013_15_R7m4+NJIBlGlCgdn/9k=]
Those bolts pulled things back into shape pretty good.

But I must admit I am not entirely satisfied with this solution. I think I need to create a new FLAT pit of 3/4 plywood rather than that 'composite board' the original was made from?

I thought I might be able to move forward with using this 'flattened pit', but if I were to cut the round hole in my new deck big enough to accommodate this existing pit with its relatively thick pit wall, ....then that hole would be a little too big for my newly constructed pit with a 1/4" thick pit wall made of 'foamed PVC' rather then the original hydrocal.
 

Bottom line, I'm better off constructing a new pit (and wall) for the very nice Diamond Scale bridge to work in, thus avoid any uneven wavy-ness for the turntable bridge to negotiate.

[attach:fileid=424013_15_0p+IqKIwVP3UUUURD//Z]

Flatenned

I think you can't go further with the flatening job

By the pictures you share, the pit is made of a fiber board similar of MDF

When this kind of stuff is really wet it wrap but it also inflate here and there and unfortunately keep this state when he is dry again.

You can flatten it but sure the inflate distortion will stay in any case

A turntable in any scale need precision to work reliably

So I think the best way to go is to build a new pit and ring; this one will give you trouble for sure

The chance you have is to have the right mensurations of the pit for the bridge.

I would suggest you to build a new pit and use and heavy plywood base with a 1' thickness for sure.

The ring of the pit need to be done and centered quiet perfectly, if you are not sure to do such ring ask a wood worker to do it, with good wood working machine is not really out of reach and this simple ring will not cost a lot

You can also use dental plaster ( which is hard as stone) to do a new one with a shaped trammel working from the center pit

Check all the forum ( you know how to do it, we all know that ) and for sure you can find good info's about how to erect a new ring

With the older pit you can make any "tools" to centering the ring and take careful mensurations

Turntable pit

Hey Brain, more warped than I thought. I don't think mine is warped, if isn't I would gladly send it to you. Let me know. It has the electric parts as well, all I would ask is to help with shipping cost.   God Bless Ya   Dave

Davnosdirt@gmail.com

Save7

Thanks for that offer. I sent you a private email.

Roundhouse Repair

Here is a very complete discussion on this Korber build/rebuild subject. I think this will be my guiding light for my repair job. 

...on another forum, and authored by the fellow Wayne mentioned above.

Building the roundhouse at Mount Forest...
https://bigbluetrains.com/showthread.php?tid=7469

Turntable Repair

Here's a blog I need to look thru in reference to my turntable pit repair,..
https://melvineperry.blogspot.com/p/135-foot-turntable-project.html

Roundhouse repair

Going forward with the start of this repair today.

I'm not so enamored to 'screwing' it together, as reported by DrWayne in the link above. I am also not so enamored with the use of superglues, as I consider them to brittle in the long run.

I'm thinking good old epoxy glue, perhaps the 5 minute stuff that allows for readjustments, that should be good for binding the resin pieces of the Kober roundhouse itself, plus the bonding of those pieces onto my very thin metal plate that will act as a base for the structure as a whole, ....plus the rigidity of the tracks and their pits within.
 

I plan on utilizing foamed PVC 'floors' glued down in between the tracks, ...that will also add to the rigidity of that thin metal base,...as well as the glued down tracks themselves.

Any other suggests/recommendations for adhesives??

I think I would just use plaster to make a new wall for the pit.

Is it any more work to start fresh making a new wall for the pit than it is to try to glue the old one back in place?  If you use sheet metal for support, drill small holes around the edges to allow the plaster to go through and "bite" the metal.  I think it is a good idea to use plywood instead of MDF, but spend a little extra and get what they call "furniture grade" or also called "Baltic Birch".  You can recognize it because it has a lot of layers of thin ply instead of the few thick ply's found in less expensive plywood.  I think the big box stores sell cut pieces in 2'x2', and 2'x4' for a lower price than a full 4'x8' sheet.

Good Plywood for Turntable Pit

Do you recall that really nice plywood I found to build my 3/4 inch cantilevered decks with?
https://forum.mrhmag.com/post/waterproofing-plywood-12210240

A lot of it has been thru last summer and then this winter 'outdoors' in my shed, that is NOT full time acclimatized. It has held up real good. I have some left over, so that's likely what I will use for the turntable pit's base. 

Haven't decided on final construction of the pit's wall, but I am quite certain I will NOT use plaster,...too much of a hassle, when there are any number of options with materials that can bend into a circle and simulate pit walls. currently I am thinking 1/4' thick 'foamed PVC sheet'. ....could just be metal like Browser utilized?....or plastic sheet material?? 

The pit's wall doesn't have to provide support itself,..it can be just a decorative trim between the top deck's track surface and the bottom of the pit (top of plywood pit deck bolted at correct height below that upper deck).

(did I get that description correct/understandable?)

When I once thought of a turntable when I wanted to build

a steam era layout, I wondered about using an appropriately sized wooden embroidery hoop, or perhaps 2 glued together to make the pit walls?  Since I decided to model diesel and won't have a turntable, I never tried it.  It seems that the embroidery hoops with thin styrene glued to the inside painted concrete color might work.  If you can get a couple of hoops the right size, it would solve the problem of forming a perfect circle.

Get a New Pit

Brian,

I am in the midst of building up my own Diamond Scale 134 ft. turntable, so I have a fair bit of current experience with what you have.  First, your photos of the cracked pit wall and warped base plate indicate that pit is beyond repair.  I think you have arrived at that conclusion, as well.  Second, the suggestion to have a precision woodworker help you is a great one unless you opt for "Plan B"--getting a new pit from Diamond Scale.  Don't overlook that option, as that certainly will match up well to what you already have.

I just completed my turntable bridge assembly and recognize that as one of the more tedious "fiddly bits" of construction.  having a good one, as you indicate, is a great start.  That is even more so if you have one that truly has the rails centered to the shaft.

I chose to fill in part of my pit to achieve the inward slope found on my prototype pit--the still functioning Eugene, Oregon turntable.  In the course of forming the plaster slope filling between the ring ridge (support for the ring rail ties and rail) and the pit bottom, I created a scread that pivoted on the turntable shaft--elevated for my purpose.  BTW, a key component of the Diamond Scale table is the pair (TWO) of bearings for the shaft.  This is an important feature of their design--and of any good turntable mechanism.  It takes two bearings to assure flat rotation.  I previously used the arm for what became my plaster scread to form and set the ring rail.  I filed a notch at the desired rail radius and used that to fit and affix the ring rail, doing about two inches at a time as suggested in the Diamond Scale instructions.  This basic technique--an arm anchored upon the center shaft--is a great way to assure the circle geometry needed for many of the pit construction tasks.

At the risk of taking you and others off the MRH Forum, you might check out my two blog posts (so far) on my turntable project.  The next one (whenever I get to that task) will describe mounting the New York Rail Supply drive and indexing kit I got for my table.  The first two posts cover the pit and turntable bridge construction.

https://espeecascades.blogspot.com/2019/11/eugene-turntable-1-pit-preparation.html

https://espeecascades.blogspot.com/2020/02/eugene-turntable-2-turntable-bridge.html

Bill Decker, McMinnville, OR

Floor of the roundhouse, maybe sheet styrene

Rethinking at the moment,...I may utilize sheet styrene (rather than my cellular PVC) to build up the floors inside the roundhouse to mate with the tracks?...(greater variety of thicknesses available)  Need to have a closer look that this subject thread,..
Building a Grade Crossing using styrene sheet
https://forum.mrhmag.com/post/jlt-railroad-blog-building-a-grade-crossing-using-styrene-sheet-12191055

Cellar PVC & Warped Resin parts

I got delayed with this project with a number of home projects,..but in the meantime I was thinking of alternative repairs.

1) I am now firmly convinced that I will build a new pit and pit walls using cellar PVC (also known as foamed PVC). Its basically a light weight version of solid sheet PVC. I really like this material. I'll document this rebuild with photos. I need to retrieve my router so I can cut real accurate disc of PVC and holes in plywood deck to accept the new pit structure.

2) Still trying to determine the best method to flatten out the warped resin built doorways of the original Korber kit. I did see one reference to a method here,... http://designbuildop.hansmanns.org/2020/03/20/flattening-a-warp/

New Turntable Pit

I spend a fair amount of time thinking about how I might construct a new pit for my turntable. The two primary pieces would be the pit floor itself, ...then the pit wall. One thing for sure I was NOT going to utilize plaster. So here is what I came up with.

Pit Floor:
Good grade ½” to 3/4” thick plywood was a top choice in my mind, painted to limit any moisture absorption and look like concrete.

I happen to have a nice square piece of 1/2” thick piece of black Sintra board (cellular PVC) I had collected up from the scraps being discarded by a local sign shop. Why not experiment with this first, ....then I can always return to the plywood alternative if this didn't work out?. I decided my pit wall was going to be 1/4” thick material ( several different options), and bent into a circle to fit the round trench I would cutting into the floor.

I got out the router, installed a ¼” dia bit, and cut my 'trench' into the flat floor board.
 

        
Here I will note that I had 2 options,..cut that 'trench' (partial depth into the floor pit),..or just just cut all the way thru the pit floor piece forming an inner disc, and an outward retaining hole in that square floor piece of PVC. Either way, both methods would support my ¼” thick vertical pit wall.
 

Pit Wall:
I had another scrap piece of the black PVC that was 1/4” thick 9” wide, and about 5' long. I needed a strip of it about 1+3/8” wide for the full length of 5' to bend around to form my 'pit wall'. At first I thought about cutting it with a saw, but on second thought, why not use a sharp razor/ box cutter type device making multiple passes,...much cleaner operation.

That relatively thin strip of plastic would be flexible enough to bend into a radius to fit into my trench, but I wanted to trial run it several times, so several in and outs, plus final gluing. I figured it was going to be easier if the strip of 'pit wall' material had somewhat of a 'preset bend'. I clamped it around my old pit wall casting, and got out my heat gun. Bravo, nice preset bend. Finally I glued in place with PVC cement.

 
test fitting

 
test fitting

 
....final pit wall installed

Once all glued into the trench everything became quit rigid, very happy with result.

Now I just have to cut some more of that 1/4” thick PVC (maybe the white stuff this time) to make a 'shelf' onto which to glue down the pit rail with its ties,...something like shown in the mock-up I did before I started the router cutting.
 
 

I can use the same router dimension plate to cut the hole in my main plywood deck that this turntable assembly fits into.

NOTE: I am now firmly convinced that I would NOT utilize that black sintra board as a pit floor,...it seems to be prone to warpage more readily than the white cellular PVC. And of course there is the good old reliable 3/4" plywood.

Pit Wall alternatives

There were several other materials I considered making the pit walls of:

a) 1/8" thick PVC window blinds (a neighbor had been ready to discard these items, and I saved them just in case). Two of them could have been bent around that trench, then had their tops sheared off level with the plywood train deck.
 

b) I could have also utilized 2 pieces of 1/8" thick cellular PVC , rather than the 1/4" I used.

All of these materials were PVC, so cheap PVC glue was used.

Base Plate for Roundhouse and its tracks off turntable

That little black piece under the track sitting on the plywood there is a thin sheet of metal like that I am going to cut a much larger piece of to make a base plate for my roundhouse,...so the roundhouse and its feeder tracks, pits, and raised floors will all be sitting on a common base plate that can easily removed from the layout to work on greater detail at a later date, and/or if I need to work on the viaduct and city scenes in the background behind these structures.

Interestingly the turntable bridge itself is also readily removable from its central drive pin,...per the design of the Diamond Scale turntable itself.

Perfectly Perpendicular Center Shaft

HELP
I need to drill a hole in the center of that floor to place the bearing (bushing) for the drive shaft. Ideally it will be perfectly square with the pit floor. Obviously I can NOT place it under a drill press, so what tool do I need to use to get that hole dead straight,...perpendicular??

Easy...

You need a milling machine.  Vertical is simple. Geting it centered is what ill take time.

If it doen't take you ten times as long to set it up as it does to make the hole,, you're either a professional machinist with 30+ years of experience, or you're doing it wrong.

Metal Guide & Centering

Its been suggested by a private party that I make a metal guide out of a block of metal on a drill press.

Finding center should not be a real problem as I started out defining that spot with my ice-pick centering device for the my router plate.

I screwed up! I'm not sure

I screwed up! I'm not sure what I did wrong?

I made a wood block something like you suggested Mel, and I drilled the holes in it on my drill press. I actually started out with rather smaller drills so as to get a direct hole in the center hole I had made when I used the router to make my circular trench, then moved up 2 larger size drills to get to the size I would need for the bushing that guides the vertical shaft.
 

Just before I went to drill the largest size hole I would need I inserted the plain shaft and loosely connected by turntable bridge to it, WOW I'm not centered properly!

I don't know how this happened !! It appears as though my center hole is off center by something like 1/16" to 3/32". Just don't know how this happened.

I have done some other measuring late this afternoon, and come up with several plans to correct this mistake,...tomorrow.

Centering Hole Correction

I was real upset with myself the other day when I found that my center hole was not centered properly.

At first I though I might just scarf in a new piece of that black PVC material into the center area of the pit, then locate and redrill a proper center hole. But first I thought I would try drilling out the larger FULL size hole needed for that brass bushing at the pit level, and relocating the center of that larger hole to its proper center. This was NOT acceptable, as it left that hole too large to properly retain the brass bushing in a snug, secure manner (oblong hole).

But it did led to another idea,...why not some sort of small thin metal plate glued to my pit floor that would snugly keep the brass bushing in its centered position. After all this upper brass bushing's primary job is keeping the turntable deck in a perfectly centered position. And since the brass bushing has a flange on its one end, it will fit perpendicular to that metal plate, that will in turn sit flat on the pit floor. So the turntable shaft will end up very perpendicular, particularly when the lower shaft bushing is located on center 2-3 inches under  that upper bushing.

That led me to a drilled out 'fender washer' to support that upper bushing.

Here are a few photos of that fender washer/bushing centering piece. The white ring inside the pit wall is 1/4" thick piece of PVC that will support the pit rail track. The pale white appearance over the whole pit area is piece of white tracing paper that was cut and laid in there to help locate the exact center in which to glue down that fender washer. Bushing sitting there (upside down) waiting to be installed.
 

When I cut out those pit rail foundation rings I ended up with some circular sections that matched the radius of my pit wall. I decided to add those scrapes onto the outside of my pit wall, as I need an additional 1/4" pad/spacer between the bottom surface of my plywood train deck and the base plate of my turntable pit.

(turntable drive shaft waiting to be installed)