Minimum Radius Rethink!

Could be my old eyes, but that does not look sharp enough for 36"R.  Did you try using a radius arm (stick with a nail at one end and a pencil at the other) to draw your curve?  Then there would be no doubt about the radius.

Regards,

Ed

Might you be confusing radius with diameter?  For example, old O-27 tinplate is a 27" diameter.  O-60, if I am not mistaken, is 60" diameter--that is  5 foot diameter, 30" radius.

Ed, I thought the same thing.  That radius does NOT look like 36".  Especially the one closest to the camera on video number 3.

 

Rick

I have personally run F units and 48' Gons on 27"r. It didn't look the best, but it is possible. Most 40' freight will negotiate 24"r as will many small switchers.

 

My problem comes with passenger cars. There is no getting around the fact that they look goofy on tight curves. Smaller cars can be used, but a 60ft car still looks iffy on 36"r to me. Of course I like to use 40"r+ in HO for my passenger equipment. That is 72"r+ in O scale. And THAT is why I don't have an O scale passenger layout ;-)

 

The wide radius requirement is the main factor that holds O scale back IMHO. It certainly isn't going to fit in my basement. At least not much more than a glorified loop or basic point to point.

I KNEW there would be a few "doubting Thomas's" out there! And yes, I know the difference between radius and diameter. LOL!!!  Do remember this is code 100 not 148 so perhaps that's creating the illusion.  Here's some pics..

 

NOW does it look sharp enough?  I don't have any full sized pax cars only 60 footers.  The area of my 36" radius curve will not be visible but hidden in a tunnel.  The sharpest curve that is visible will be 42".  My point is we don't think the locomotives can handle 36" radii.  Now, I saw where a fellow was selling a brand new Sunset SP Mogul that he said wouldn't negotiate his 48" radius code 148 curves.  If this is true I guess you need to check each locomotive.  Maybe only the more expensive have engineered enough side-play into the drive train to perform this feat. 

 

Anyway, thanks for listening,

 

Peter

That's interesting.

Peter,

My apologies.  I do have an appointment with the eye doctor.

Cheers,

Ed

Nice looking locomotive.

 

But the other thing you need to be careful of is can it pull a train at those radii?  Sure a locomotive can go on those turns, but it could pull the following car off of the track, or hit corners.  You say you are lengthening the drawbar, you may also have to increase the gap between cars to keep them from derailing or hitting.

Hmmmmmmm

 

Rick

Sinclair. 

 

As I am building the layout and the scenery as well as putting in the supports for track and the mountains above it, I will be very careful to avoid putting any where their corners will get hit.  As for cars, I believe a 40' car will go around about a 20" radius curve.   If you get the whole purpose of my bothering to post this it's because I have a small O scale layout.  Small means I won't be having long trains so I'm confident I will not be pulling anything off the inside of the curve.

 

I really don't understand you guys.  I take the time to post something which I thought might get people thinking and experiment with maybe getting a steam locomotive and all I see are comments about all the things that could go wrong!  Reminds me of my dearly departed mother in law.  That woman would find something wrong if she was hung with a used rope.

 

Peter

I think the 48" minimum was an appearance thing.  Even then, 80' passenger cars do not look realistic.  A scale Northern will have problems on 70" radius - you can see that by how much folks dremel the tailbem and cylinder block to make them work.

 

If you are willing to put up with equipment inaccuracies, 2- rail models can run on O-27, which, as I understand it, is 13 1/2" radius.

When I first considered switching to two rail, I got a Westside PRR J1a (2-10-4) from one of our local O scalers. It had been reworked by another member of our local group to go around tighter radius curves.  Nothing drastic or obvious, just some unobtrusive changes

 

I then set up a test track on the floor with Atlas 2 rail sectional track.  In other words, I did exactly what Peter did, established for myself what the radius limitations really are.

 

That massive J easily went around 48" radius curves with no easement. I then added easements and it went around 44" radius curves with no problem.  It went forward and backwards, either pulling or pushing a train.  It went around 40" radius, but not so smoothly.

 

Of course it did look a bit odd, but for curves that could not be viewed end on (or hidden) they would be fine.  Based on this, I went to 2 rail

 

My layout has Sunset GG1's pulling GGD full scale, close coupled passenger cars regularly going around 48" radius. They will go around 44" radius.  I have four axle diesels (close coupled A-B-B-A F units) pulling a 15 car Reefer block going around 40" radius curves.  That train will go around 36" radius. In the interest of full disclosure, all my curves have easements, and I have been told my track work is smooth

 

I submit that the need for large radius curves for 2 rail is a myth propagated by folks who never actually did the experiment

Peter said, "I really don't understand you guys.  I take the time to post something which I thought might get people thinking and experiment with maybe getting a steam locomotive and all I see are comments about all the things that could go wrong!  Reminds me of my dearly departed mother in law.  That woman would find something wrong if she was hung with a used rope."

 

Peter, I believe you are misinterpreting the comments.  You are looking at them as a glass half empty when they are intended as a glass half full.  The comments are warnings about what could happen so you will not make the same mistakes as others have made in the past.  I believe it is your interpretation and not their intent that is at fault.

Regards,

Ed

 

Interesting Peter.  There is  a forum member Paul Lally who has a 2 rail layout with small 24" radius curves. His fairly large 2 rail Youngstown and Southern layout was featured in OGR magazine awhile back, it was the cover story. Yes his engines & cars are of smaller size.

........or by people that are clinging to yet another excuse to not move to 2-rail.

 

My curves are substantially tighter than John's - closer to 28-30" in many places and a few tighter entrances into siding where only an 0-4-0 might venture.  But the largest engines I have - 2-8-0's run fine while the 2-6-0's tend to complain a bit.  I had a 4-6-0 that was problematic, but that was easily solved by selling it,

Ed,

I can see your point about not wishing to repeat past mistakes and I did take it in the negative.  I guess I was so thrilled that I could use the 36" radius where I really needed it I had to share.  If someone told me an O scale steam engine with 4 flanged drivers could negotiate that I would have doubted it.  I knew a 3 coupled could as I have some but not a 4.  My intent was positive and I took some of the responses negatively instead of informatively.

Sorry,

 

Peter

My layout is a giant test loop.  Minimum 60", maximum 74", with loops in between.

 

My SP articulated chair car needed an additional 1/16" space between halves to go around the 74" radius.  My Northerns and ten- coupled locomotives can run only there, and not on the 70" loop.

 

It is all dependent on what you want your rolling models to look like.  If I double the spacing between passenger cars, remove the tail beams, and lengthen the engine truck and associated frame, then I can go smaller radius.  I have no desire to do any of that.

 

I know how to make O Scale models go around corners if I want.  I don't want.

 

On second thought, here is one that will easily do 24" radius with a string of 40' box cars.  I would probably have to modify the couplers on the boxcars.

 

 

17/64 scale.

Although you may be able to get small engines and cars to negotiate small radius curves, do you really want to?  I know many model railroaders who model in all gauges.  Nearly everyone eventually wants to run a large engine or car.   Modern road diesels, for example, are almost as large as a Big Boy.  Modern freight cars can be 80 feet long.   

 

I think that it always wise to build a layout with the largest radius curves as space allows.   It not only looks better but operations are also better.

 

Joe

 

Joe

I believe Ed Rappe, on his O Scale, 2 rail layout, has 55" minimum radius curves.  He is a big Pennsy guy!  On these curves he runs Centipedes, Q-2's, T-1's and other large engines with no problems whatsoever.

 

Steve

Peter...it's interesting that your using one the Fast Track radius fixtures. When they first introduce them I wondered if many would use them. It's a sure way to control radius size where it is critical. Go build that railroad now...I want to see more!

 

Thanks

 

Bob

Steve

 

My previous railroad (March 2000 Model Railroader) had a mainline minimum of 54" radius and a hidden one of 50".  It's design was influenced by John Armstrong who used 54" radius curves and curved turnouts to pack the most operation into a limited space (John ran a 2-6-6-6 super Allegheny and several 4-8-4's).  On my railroad I ran prototypically flanged PRR 2-10-0's, 2-10-4's, 4-8-2's, 4-4-4-4's, and 4-4-6-4's. The Westside Q2 and J1 required minor work on the journal shoulders to provide additional side play on the front and rear drivers.  I lengthened the tongue on the J1 leading truck slightly enabled the pilot trucks to clear the cylinders.  Locomotives with 4 wheel trailing trucks generally required removing a little metal out of the tail beam extension in the area of the rear axel to provide more swing.  Since the vertical cross section was not changed and the routing was deep under the firebox the mod was not noticeable even at eye level running.  The mine branch had a 42" radius curve hidden in a tunnel. To enable Key H class consolidations to operate on the branch I lengthened the leading truck tongue similar to what I did with the J's.  My experience is that with care you can significantly reduce the minimum radius for most O scale locomotives without marring their appearance - if done judiciously.

 

Ed Rappe

 

PS -  On the new railroad the mainline curve are broader as the basement is wider - 62" radius with most quite a bit larger.  I wish John was around to operate with us again.  I think he'd see his influence. 

I for one would rather have a bigger scale in a smaller space. That dictates smaller equipment and tighter curves. That's fine with me as I prefer the smaller prototypes to the big articulateds. I'm not a huge fan of the big modern 6 axle diesels or freight over 50' either. I tend to agree with the ideas that the late Joe G. used to write about.

I tend to agree. Seems that a great majority of modelers equate bigger with better, and the smaller locos are scarcer for that reason. I started out in that mode myself, but soon came to the realization that maybe bigger was NOT necessarily better, at least for me. One thing that can't be denied is the smaller your equipment, the bigger bang you will get for your space. I do have one articulated, but I don't see any stable mates for it in the future. For me, smaller is definitely more attractive, and the era I prefer precludes huge modern diesels and a lot of the larger freight cars. It is all what you like, but sometimes reality (space) needs to be considered.

 

Simon

Like stated, we aren't trying to knock you down, just give you more to think about and watch out for as you make your tight radius layout.  Being a 3R guy, I build for the tight curves because of lack of room.  And I test my stuff too.  I had a min O31 K-Line Big Boy going on O27 curves one day because that is what I had (It now spends it's days on O48 mostly.).

 

As for hitting corners, I didn't mean on track side scenery, but on the cars themselves.  Knowing that most 2R guys have Kadee couplers, which are mostly body mount, I pointed out that you may have issues with rolling stock on tight curves.  Kadee couplers have close coupling of cars, and when you go on a tight turn with them, the corners of the rolling stock will either touch if there is enough side to side pivot to move that much, or will cause the cars to come off of the track if there isn't enough side to side pivot.  Many of my locomotive's manuals state somewhere in them something along the line, "While this locomotive is more than capable to go on O## curves, you may find that there is issues with the following car coming off of the track on tight curves.  Add weight to the car or try a different car if you find this is the case."  Also I know that Lionel made a 3R shay that could go on tight curves by itself, but try ti pull any cars behind it and it'd just pull them off of the track.  I just wanted to make sure you try it with cars in tow so that you don't lay track only to find out you can't have a train.

 

I really don't understand you guys.  I take the time to post something which I thought might get people thinking and experiment with maybe getting a steam locomotive and all I see are comments about all the things that could go wrong!  

 

So help me out here: you posted your comments hoping that everyone would agree with you?  Or that only folks who wanted to operate on 24" radius curves would respond?

 

 

Seems to me that you got plenty of agreement, plus a whole lot of comments on why the rest of us do not immediately go to tight radius.  That is what a conversation really is - diverging viewpoints, offered for discussion.

Peter, when I first got into 2 rail O scale I was using Atlas 24" radius track and their old F-9s and 40' freight cars and their old #4 switches (I think they were #4).  Everything worked fine but I never had any steam to run or diesels with 3 axle trucks.

 

Rick

I run 2-rail, full length passenger cars, including 85' streamline, on 36" r curves with KD couplers mounted on swing arms pivoted as close to the truck pivot points as practicable. Length of the swing arm is adjusted for each car so that diaphragms don't catch on each other. The result is approximately a 1/16" gap on straight track, which I can live with.

Bob and Sinclair,

 

When I posted this I did it for informational purposes as I was surprised what I found out.  I had never seen another posting about small locomotives and small radius curves.  Granted I do not follow these forums religiously so I might have missed it.  I never thought there would be so much feedback and I did take Sinclair's response the wrong way and I apologize again.  I broke my own rule of sleeping on any negative writing in an e-mail, memo, letter and now that I'm retired, forum post prior to hitting send, er "submit reply"!  

As a funny aside, I had written Jimmy at Glacier Park about minimum radius and he advised..."..... know the 2-8-0 will go around 42"  It was a lot of side play in drivers,  I'm sure it would, but it might be tight".  Based on this I bought it and decided to try the tightest 36", (not 24" Bob).  I sent him the video and he replied he was drawing up a layout plan that ended up with 1 38" curve he just couldn't make bigger and was contemplating a redo but now he will lay it and try it.  Hey, he imports these things but I guess like a lot of folks, they don't "think small" with O scale.

I hope to have that curve laid in about a week and then can try it with some cars.  I'll post a video.  I have five fingered a whole bunch of my cars around and on the S curve and no problems yet.  We'll see.  I have my crow tenderizer ready!!

 

Take care guys,

 

Peter

 

 

Peter,

I find your information, photos and videos to be refreshing and informative. Keep on posting.

I also found your information interesting. Yes, please keep on posting.

 

That is one beautiful locomotive and it runs great too.

 

Many years ago when I was 3 rail I bought a Lionel CNJ Camelback. It was rated at O-42 (21R) curves. I had it converted to 2 rail and the minimum radius did not increase. Of course I intend to get the tender closer to the engine and this will probably increase the minimum radius but as Bob2 always says (something like-not an exact quote) the center rail does not determine the minimum radius. One can have the same minimum radius as 3 rail if they decide to accept the same compromises. After much deliberation my minimum radius will probably be 48" in one turn. I think moving the tender closer to the engine will greatly improve the looks of this model which by no means has a lot of detail.

Hi Peter.

On my switching layout I have run 36" curves for the last 20 years with no problems either pushing or pulling but then I only run diesels.

Thanks for taking the time to do this exercise and posting it.

Neville in West Australia.

Peter,

 

I came to the same conclusion as You, John, Ed, and others about the naysayers and radius in 0 scale. Thanks for the post. 

Minimum radius is like most of everything else we do in model railroading, it is a compromise.    After all, we run our steamers with electricity, and our diesel-electrics have no diesels.    Not many pieces of equipment have working brakes.   The distances our layouts cover are very small compared to real life, yet we sometimes say we are going from NY to Chicago. 

 

Everyone will base his requirement on what he wants to do.  If he just wants to see a couple big steamers run around a loop, he will use the largest radius an around the walls loop will all.    On the other hand, if he wants an operating layout to run with friends and do switching and car forwarding and whatnot, he will design a layout with minimum radius his equipment will handle and probably select equipemnt or eras that use smaller equipment.

 

Back in the 50s and 60s, the other old-timers (before I became one) pretty much figured 48 inch radius was a good standard or compromise.    Some guys went a little bigger if they had space but 60 inch radius was considered rare and wonderful.     On the other side, many modelers use less than 48 inch and modified some equipment that would not fit.    All Nation listed the minimum radius for all their steam loco kits, 4-4-0, 4-6-0, 4-6-2, and 4-4-2 were most common.    If my memory is correct the smaller ones had a 40 inch minimum listed and the 4-6-2 might have been listed as 44 inch.    These locos were the standards on many layous.   AN also offered a 4-8-2 at times, but I never saw an ad for it with the minimum listed.   I would guess that it would handle 48 inch radius OK.  

 

I have a Pearce 2-8-2 that easily goes around 48 inch radius.    I also have most of PRR steamers imported by USHobbies and they all go around 48 inch radius, this includes the 4-8-2 mountains.   

 

My minimum is 52 inch on the main line because I had the space when I built this layout.    I now have a J1 2-10-4 and it is OK with 52 but would handle 48.

 

So my recommendation is, build what will work for you and look OK to you, remember "Rule #1", it is  your Model RR!.    Plan it for what you want to run and do with the RR, not for what someone else might think.   I would also recommend using the largest radius that will fit your plan.    I think 40ft cars with body mount coupelrs will work on 24 inch radius, but I am not sure.   The coupler swing will be the limiting factor and you can modify the boxes to get more swing. 

 

Wise words prrjim.

I have been in O Scale since around 1985 (but who's counting!) and have been blessed with a room 26x26 feet even that size is small for O Scale so I filled it with an industrial area.

The only hiccup I have found with sharper curves than 36" is when pushing cars larger than 40 footers they can touch (in some cases) of course you can modify the couplers and all those sorts of things but it isn't always necessary naturally pulling cars around a sharp curve they are spaced out further so there is no problems but the original question was about steamers not cars.

Just as a matter of interest when you are limited for space 40's and below look better not only on curves but sitting in sidings that are shorter than normal again it's up to the layout owner what they like and what parameters they set for their layout.

Thanks. Roo.

I have to say that thid thread has thrown some light on questions I have been bringing up about 2 rail and curves as opposed to 3rail equipment.  I brought this up with Allan Miller at the TCA show. Yes I am considering doing an all O display to displace ha Ha I mean take place of the Spruce.

I must have tight radius and I want to prove you can have craftsman work and knock out detail on a super small full sized o scale layout. Unrealistic curves do not bother me as I can disguise them but I know I don't want 3 rail.

Soŕry, typing with my thumbs on phone here.

My biggest concern (and this thread only confirms it) is that the "uh-oh, I wouldn't do THAT" crowd has possibly chased away more potential 2-trail O-scalers that we care to admit. Anyone who does the basic research will find plenty of material on what will and what won't work on a given radius in O-scale. If you study the early trackplans of the Dean Hizzself, John Armstrong, many are based on a minimum radius of 36" in O-scale, including a gem of a folded dogbone plan that fits in 20' x 24' and incorporates a helper grade with turning facilities at the top and a division point yard!

Everyone knew you weren't going to run Northerns and SP Decks on that layout, but you could have satisfying prototype operation in that space if you were happy with 2-8-0's, Moguls, and mainly freight rolling stock.

I've got just over 1500 sq. ft. of space for a layout, and I chose to build a railroad with 46"  minimum radius curves and 3% uncompensated grades to create a layout that will be a challenge to operate and be a believable amalgam of California shortlines (couldn't settle on just one ;-)). I'm having a ball pushing track from Bakersfield to Guadalupe, and those USH Harriman Consolidations look right at home on those sharp foothill curves.

 

That is one of the biggest problems out there right now, this thought that in order to be in 2 rail you must have monstrous curves which simply isn't true.  There are many, many models that will operate just fine on smaller radius if you do the research and get the information.