I had done a rather extensive fabrication of a turntable in O-scale.   Using some Diamond Scale parts and a Bowser deck detail kit. 
Here is a link to another post I did on another forum.  I should give you an idea as to how complex the project can be.  http://ogaugerr.infopop.cc/eve/forums/a/tpc/f/3681097934/m/6381056754?r=6381056754#6381056754
Pictures posted on my website.
http://www.mikedian.net/trains/Model%20Train%20Pics/Model%20Train%20Pictures/Fort%20Pitt%20Hi-Railers/Turntable/index.html

This is a Diamond Scale O-scale TT model OT 105 (105 scale feet) with a Weaver M1b with long haul tender.

Third Rail DM&IR 2-10-4 with large tender. 


You're probably right, 90 scale feet is not going to work on some of the larger engines  This is a scratch built turntable 33 1/2" or  134 scale feet.  A big boy will fit. 
This Pensy C1 0-8-0 looks small on the TT.

Diamond Scale and Bowser also makes HO TT as kits.

  http://www.diamond-scale.com/products.htm

http://bowser-trains.com/hoother/ttables/ttables.htm

This is a link to CDS dry transfers, a type of decal, that can be used on 8 or 9 bay 55 ton hopper.
http://www.canadasouthern.com/tmr/images/cds-99.jpg 
This bowser hopper would work.

You could check the Bowser site. http://www.bowser-trains.com/hocars/100t3bay/100t3bay.htm
Another link to 100 ton Shawmut cars.
http://www.bessemerhobby.com/.sc/ms/dd/HO%20Cars%20Bowser--100%20Ton%203%20Bay%20Hopper%20Car/4474447/Bowser%20%2A100%20TON%2045%27%20Triple%20Hopper%20Shawmut%20-%202nd

Both Bowser and Bessemer Hobbies, selling Bowser rolling stock, have stock of Pittsburg and Shawmut hopper cars.  The 55 ton fish belly hopper is going to be a bit more work. The Bowser site also shows a 70 ton hopper in Pittsburg and Shawmut.    I've used the CDS dry transfers on some O-scale Atlas hoppers.  The car behind engine 234 has CDS dry transfer decals.   
 

Speed control technology gets better every day.  In slightly larger scale with out speed control I do this consist often.  Each unit pulls about 1.5 amps AC.



With electronic speed control running engines that are different is much easier.   Even doing pushers on the end of the train is possible.

Another available Craftman Kit is from Diamond Scale.  You may want to check their wesite.    http://www.diamond-scale.com/products__turntables.htm     It takes a while to navigate their site and determine all the parts needed for the TT that you want.

This is my Diamond Scale OT 105 Turntable. 



Bowser also manufactures a turntable
A link to their site.         http://bowser-trains.com/hoother/ttables/ttables.htm   

This is a Bowser deck detail kit on my scratch built for TCA Fort Pitt High-railers show Turntable.

Justin:
     You and your friends are welcome anytime.  Unfortunately I have no O-gauge Thomas items.  I'm sure that my Grandson Micah would be thrilled if I did.
Micah runnings the trains from the layout. 
    

     Corrie and his Dad had  also talked about seeing my layout.  My layout like Corrie's is not complete. 
 
     I will also be at the Greenburg Show at the Monroeville Expo Mart, Pittsburgh, PA  July 12 and 13 with the TCA Fort Pitt Highrailers.  I usually bring all of my Pittsburg and Shawmut trains to run at that meet.  You and your friends may want to make that meet.  We allow the visitors to use our Lionel Cab-1 remotes and run the trains as long as they are not abusive.
A Shawmut Coal drag with (4) SW's  original paint skeem from Atlas with Custom paint  Atlas  (Independence and Betsy Ross bicentenial paint)






You can access my website

http://www.mikedian.net/trains/Model%20Train%20Pics/Model%20Train%20Pictures/index.html

Click on the file folders to aceess pictures.  Click on the thumbnail pictures to enlarge.  Check the upper left corner of the index page, there is usually more than page per file. 

Have fun
Mike CT

The flywheel can have multiple purpose.  Momentum is obvious.  A smaller motor with a flywheel may be more economical that a larger motor with out.   In O-scale the flywheel may be equiped with an optical sensor that is coupled to an electronic speed control.  Extreme slow speed realism is sought after in O-scale   (2-scale mph)

Here are some pictures of an upgrade.  Larger motors replaced with smaller motors with flywheels.    Weaver E-8's with and Engineer on Board speed control upgrade.

E-8 A unit with standard can motors, no flywheels and an electronic forward reverse unit.


Remove all.


Put it all back together with much smaller motors.  Note the reader tape and optical sensor on the front motor.




The new electronics greatly enhance automatic operation with on board speed control.  The flywheel motors are a definite  plus. 

This is a Diamond Scale OT 105  turntable.  Works well for O-scale engines and would be easily adaptable to On30. 




Note the pit rail  bogies are well built and support all the weight of the engine.





Diamond Scale has changed hands in the last year.  Currently the O-scale Turntables and the largest HO scale TT are not available. 

Justin:
    Please note that Corrie has (4) sets each, Independence, and Betsy Ross. Eight total sets of Decals and I can get more.  When I ordered the decals I usually get multiple sets in case I mess one up.  He also has a list of all the colors I used along with decal setting solution and a clear coat.  He had talked about decals for his friend Frank. 

   Let me know if you can't get decals off Corrie, I can get more.  I picked the SW's up off E-bay for about $40 each and worked from there.  It was a nice air brush paint project. 

I'm sure you have the ability to create a nice set of Shawmut Line Diesels. 
 
Corrie has been busy on Maintenance of Way projects.  The Proto 2000 set needs some pretty nice track to operate properly.  I was surprised at how smooth and slow they will run.

Best to be doing school work at school.  

Mike CT

Justin, Sparks, Guilford... , It's nice to meet you guys.  I have been a parent for a long time, (4) wonderful kids, and now (4) wonderful grandkids. 

As a parent you are always concerned about what your children are doing.  I think it will be that way until my last day.   I'm sure that Corrie's dad is the same way. 

I agree.   LEARN!!   It's part of growing up.   Corrie also needs to clean up that signiture, that does not need to be.  He also needs to talk to his father and explain what happen.  I have said nothing to this point.  Part of growing up is accepting responsibility for your actions and the consequences that come from them. 

Corrie lets get this straighten out, At the least, even if you were right, you owe Henry Blue a public apology here on the forum.   
Thank you, Bach-man
Michael C. Thompson

A very nice set of Shawmut Line SW-9's

This is a very interesting situation.  Keep in mind that Corrie is or will be soon 15 years old.  He has some talent as was shown in his post and some computer skills.  The problem of lack of civility is not uncommon, I see a lot of it on an O-scale forum, which I participate. 

Rules are to be abided by.  Corrie e-mailed me last night explaining what had happened.  Unfortunately life is a never ending "learning experience".
Hard learned lessons usually stick. 

I'm sure that Bachman understands their market and their responsibilities concerning maintaining this forum.  What Bachman did is correct and they have my support.  Though not involve a lot with my nephew, he does respect  my model railroad abilities, i.e, I'm somewhat of a mentor.  The e-mail last night went on to say that he would be in trouble with his parents and not to tell them.  My brother, Dan, does a good job of parenting his two son and I'm sure Corrie will have some problems for awhile.

I would hope that Corrie learned something here.  But at the same time I would like to foster his modeling abilities and see him gain more skill.  It is in Bachman's best interest to also foster young hobbyist, some of them will become life-long hobbyist.   

Michael C. Thompson
Mike CT   

That is quite a project Corrie.  It is really looking good. You also did an excellent job of taking pictures. 

This should be a good home for these Pittsburg and Shawmut SW-9's once I get them finished.



Your father said he was sending me the decals yesterday when I talked to him  I have a few more things to do.  Apply a gloss coat and some trim pieces. I also have to replace the one light that is not working.  Then apply the decals and they should be done.

Good to see a nice project
Uncle Mike CT