Helix Design

[Omaha Road Man]

As posted in another thread I'm working on a bedroom sized layout. As part of my plan I wanted to utilize a closet to fit in a helix to provide access to lower level staging. I'm not 'in love' with the idea of the helix but I may have run into a snag. To fit in the closet (and not using the closet will waste to much layout space to justify the helix) I'd be able to use a 22" radius helix at most. From the searching/reading I've done this seems like it would be pretty tight; I'd need a 2.5% grade or greater to get the track separation I'd need. So before I have to rework my entire plan I'm wondering how much of a grade is too much for a helix? I'll be running 8 car trains plus the locomotive. How much of a separation between helix layers is need? It seems the standard is 4" but measuring the cars/locomotives I'll be using (and accounting for sub-roadbed/roadbed/track of course) it seems I could get away with 3.5-3.75". Is this just wishful thinking?

I won't be tackling the helix right away as stated in the other thread but its placement is key to the rest of the design. Need a bit of advice here, thanks.

[P5se Camelback]

ORM ...
Most, if not all of the answers to these and other questions regarding minimums, maximums and standards of all sorts relating to this hobby we all enjoy can be found on the Nation Model Railroaders Association Web site, <!-- m --><a class="postlink" href="http://www.nmra.org/">http://www.nmra.org/</a><!-- m -->. The site is a wealth of information and as far as I'm concerned, there are benefits to membership.

My own opinions are that 2.5 % is getting out towards the limits of grade varients ... I will have 2.5% grades coming and going from hidden staging on my own layout, which by the way, is about where yours is right now. I'm returning to the hobby after twenty years of being away (job, family, etc.) so I'm planning and building just like you.

i can't remember what the minimum for vertical separation is between grades, but I sorta recall something like a minimum of 3" above the railhead, but I'm not so sure that allows for some of the modern "tall" stuff, e.g. tri-level car carriers and the like. (I had to dig out my NMRA "Clearance Gauge" and physically measure it. Yeah, I'll admit it ... but it's more important to know where in information can be found than to attempt to keep it all in your head!) Remember to add the thickness of your roadbed and supporting subroadbed when you begin to do the math!

BTW, everyone here seems to have shortened "nicknames" often used as a typing shortcut. I'm often "P5" or sometimes in the Chat area, just "P," so take no offense at you name being shortened, O.K.?

[Omaha Road Man]

None taken . I was actually an NMRA member for a year but I think it just lapsed, or soon will, I'll have to check on that; thanks for reminding me of it.

[Russ Bellinis]

A helix hidden in a closet does not need roadbed. You can install the tracks directly on the sub roadbed and save that extra 1/4 inch. It may not seem like much, but it could make a difference. In addition if you support it from the sides with metal angle brackets with a maximum of 12 inches between supports, you can also use the thinnest of plywood like 1/8 inch luan, saving you another 1/4-1/2 inch. It might be a little noisy, but sometimes function rules out over form.

[nachoman]

It entirely depends on what kind of equipment you are running. If it is 4 axle diesels and 40-50 foot cars, I foresee no problems with those curves or grades. Even most 6-axle diesels or 8-coupled steam engines won't have problems with 22" curves if you take it slow. A lightweight 0-6-0 may not be able to handle 8 cars on that grade.

If you are putting it in a closet, you almost have to build it before you build the layout, because once the layout is in place you may no longer have access to the closet. Trying to shoehorn a helix into a closet with access blocked by a layout could prove extremely frustrating if not impossible.

[Russ Bellinis]

It entirely depends on what kind of equipment you are running. If it is 4 axle diesels and 40-50 foot cars, I foresee no problems with those curves or grades. Even most 6-axle diesels or 8-coupled steam engines won't have problems with 22" curves if you take it slow. A lightweight 0-6-0 may not be able to handle 8 cars on that grade.

If you are putting it in a closet, you almost have to build it before you build the layout, because once the layout is in place you may no longer have access to the closet. Trying to shoehorn a helix into a closet with access blocked by a layout could prove extremely frustrating if not impossible.

I had forgotten about the access issue. You will need to be able to crawl under and come up in the middle of the helix to rerail rolling stock that derails in the helix. You will need some sort of barrier on either side of the helix to keep your trains from taking the big drop to the floor in case of a derail. Your radius is always measured to the center line of the track. That means that your maximum size hole to come up through will be 20 inch diameter. If your shoulders are wider than 20 inches, you can only get your head and one arm up there to rerail. At best it will be awkward if any problems occur with the train, at worst it will be impossible. I think that if you don't have space in that closet for more than a 22 inch diameter helix, it won't work. Your absolute minimum radius for a helix has to be the width of your shoulders + a couple of inches when there are walls around the outside of the helix.

[Triplex]

22" radius, so the interior diameter will be about 40", not 20". That access issue only comes into play with N scale helixes.

[Russ Bellinis]

Thanks Triplex, I forgot to double the radius to get diameter!