Heres my problem. I only have room for 36" bench work to build a helix to the 2nd level. Good news is I have 6.5 feet in length to build an oval. The power units would be Geep's, SW's, 0-8-0 and maybe a 2-8-2 max. Scale is HO, no cars over 40'. Is it possible to build.? The track would be glued in place with flex track, no roadbed. I've rack my brains out, pulled what hair I have left. Guess my high school math has gone so stale that I am lost. I looked at the spiral helix link, but that's not helping me. Can someone help this ol man out. I would hate to have only one level, and I know I can get what I'm striving for in N scale, but with grand kids and my age, HO seems to get what I need to model. By the way, the layout design is strictly mainline (2) , mostly 27" wide shelf type, except the helix.
A 36" wide space would allow a 16" radius helix leaving about 1" clearance between rolling stock on rails to edge of bench work. Suggest you tack down a 16" circle of track on a 2.5-3% grade & run ALL your rolling stock around it. If my math is right (LOL) that's about 100" long. That should give you a good idea which equipment will run thru your helix.
You would have a tough time getting an HO loco and one or two cars to negotiate a 16" radius helix. I believe to clear each level, you'll need about 3.25% over 100.5", and with the tight curve, that will place a heck of a strain on the train. Instead of a traditional round helix, you might be able to use the both the width and length of the bench to reduce the grade.
it is difficult to know what will work and what will not work without a better explanation of space available, or better yet, a track plan. can you upload something that will provide such? or, at the very least give exact size of space you have available that a helix could occupy. thanks! Gary
You have room for the roadbed on which your tracks will sit in the 36" you mention, but when you factor in the clearances so that nothing sideswipes the sides of the fascia or whatever is at the edge of the 36" and the extreme edge of your roadbed, you will only get perhaps 17" radius of the rails themselves, and that's with rolling stock with almost no overhang. Cylinder saddles and rear cab roof extensions on steamers are notorious for scrapping things set too close to the rails. so you may find that even 16.5" is the safest radius. Does that sound like something you'd enjoy installed permanently? Helices are tricky to erect, but they are also tricky to run. They need clearances to the sides, both inside and outside the curve, and also overhead in case you must reach over top of an item to lift it and recover it if something goes wrong. In HO, your rail top to overhead clearance (in a helix, the nether surface of the next level sub-roadbed) should be a minimum of 3.5" so that you can squeeze your fingers over the top of the item without causing them all to fall sideways and cause even more mess or details damage. I am currently building a helix with a an inner/outer edges radius for the sub-roadbed plywood ramp of 33"/39". At a grade of 2%, plus or minus 0.3%, with arcs of plywood that large I have overhead clearance of 4", plenty generous.
You will have to use an even smaller radius; outside the tracks you'll have support risers for the sub-roadbed. Probably a 15" radius, maybe 16" at most, is all you can get in. If your helix can be an 6,5 ft long oval, the grade will be just under 2,5%; which seems very doable. However added drag for curves is about 2%, so your grade on the curve is comparable with a 4,5% grade if it was on a straight piece of track. Short trains will not really be a problem I assume. Yes sir, a good drawing would help a lot. If the helix is double tracked radii become way to tight. I would rethink the whole concept. If I understand your plans right you are building a point to point system with a double track main in between; since the 27" shelves are way to narrow for turnback curves. Wish you wisdom Paul
Thanks, that helps to visualize your situation. Unfortunately, it doesn't improve our estimation that you have two apexes, each one at the very center of each curve, that look to be in the 14-15" radius range, and that's if the gods are having a good Friday. Your curvature onset, in four locations on this loop, are nice and wide, but as they turn past 80 degrees coming from either of the four entrances to the two curves they get much too tight. You would be better off having a real oval. If you meant to depict an oval, then your radius is still in the 16" range because you need clearance beside the tracks. From the center line of the tracks, measure one full inch outward over the tie ends. That's the minimum clearance you'll need on an 18" curve, but I'll bet good money you'll actually need about another quarter inch beyond that for longer cars and steam locomotive parts to clear.
Thanks for all the imput. I'm going to have to re-figure my thought pattern and design. I don't think I can get anymore real estate to do what I wanted to achieve. I might be able to get another inch in width, but I need to mock it up before I continue with the 2 level thought. The mainlines and holding tracks along with all the industrial sidings and spurs are actually coming from engineering prints from GTW. Giving up 6.5' in length is one compromise, but I gain another 40 feet plus of mainline on the second level with a helix, so that's a plus. If I extend the width to 38" I could fit a single track @ 17" allow 1" clearance for each side thus leaving another inch on each side and take all 38"'s, if I'm figuring this with your thoughts Crandell. I guess my question is still about the grade, and is this now an acceptable possibility to do. The train length would be no greater than 5-10 cars all 40 footers. single track, going north (UP the Helix), 10-15 cars coming down from 2nd level to the "Lake Yard" I've attached the bench work design.
hi again, the very small radius could become an issue; not only the radius it self but also the extra drag (32/R= 2 %) it adds to the grades. The small steamers I obtain, a 2-8-2 and a 4-6-0 do have problems with my 18" curves. On my new layout I was able to use 22" radii without binding issues anymore. Looking at your drawing you seem to have the possibility to widen your bench-work at least half a foot. This is the reason why a drawing of the whole space is preferable. Best of luck Paul edit: BTW, your last posting was done before I placed mine I would rethink the whole concept. I still think you should not try to squeeze in a helix in a space that narrow. With a 18 radius it remains questionable if your steamers will face no binnding problems. Add 3" at each side for support of the subroadbed and it becomes clear you will need about 4 feet of width for the helix. As said before, when the helix is single tracked, without return loops at the top and bottom you are not able to have a double tracked main. The emphasis of your plan could become dispatching and switching. Lets face it lots of terminal work has to be done on a true point to point. When the number of through trains is low however, you won't need to double track. Enough industrial area's are giving more then plenty of work. Paul
Two problems w/ your current plan. First the two yard levels are way too wide to reach across if your grids are 1'. Second the curve exiting the helix is way too small (6"R ?) as drawn. See if the attached plan for entering & exiting your helix works for you.
Your diagram shows a wall behind (to the left of) and below the 3x6.5 ft helix space. If the space to the right of the helix is an aisle, can you gain an inch or two into the aisle? If you have to maintain clearance for doors to clear the helix footprint, could you just widen the portion of the footprint where the door would still clear instead of the entire 6.5 feet? If you set the helix footprint at 3 ft wide in order to have an aisle that is X inches wide all along the 6.5 ft side of the helix, could you negotiate an extra inch or three only at the 1.5 and 5 ft marks where an 18 inch radius curve of track would come farthest into the aisle but then would curve back in to the 3 ft width (creating a kidney shaped or dented oval). This would result in a choke point in the aisle at the 1.5 and 5 ft marks, but if you use a curved fascia instead of straight, the choke point would only be a fraction of an inch long and the aisle would quickly widen back to X inches as the track curved on around the dented oval. If you used Cajon's figure-8 idea with 18 inch radius curves and a curved fascia, you could "dent" the oval a little more, but you would still have choke points that extend into the aisle at 1.5 and 5 ft. More problematically, you would also have two smaller access spaces of about 30 inches diameter each inside the helix instead of a single oval space of about 30x72 inches, and getting inside those smaller access spaces for track cleaning and repair is MUCH more uncomfortable. [For what it's worth, on a previous layout, I had a helix with an inside diameter of 30 inches and the lower level deck was at 36 inches elevation. That meant that I had to crawl on hands and knees to squirm beneath the underside of the benchwork (which provided about 31 inches of clearance). For subsequent helixes, I set my lower deck at 48 inches so clearance under the benchwork was about 42 inches. This allowed me to sit on a wheeled dentist's stool, bend forward, roll under the benchwork, and pop up into the helixes for maintenance and repairs. MUCH easier on the knees and back!]
Three of my current helixes have access openings that are 28 to 30 inches in diameter, and one has an oval opening that is 28x50 inches.
I appreciate all the comments. I guess my thought pattern has given in to the choice of no Helix and downsize my track plan to a smaller layout. (shorter point to point) I am inspired with Lance M and Jon with their switching layouts. I won't compromise and go N for numerous reasons. To small, sound is not good enough and tough to fit in Sw-12's and 15's, need magnifier to read car numbers, adding super detail to engines and cars is way to small. So I'll take apart the drawings and select industries and model it in a cut and paste method. Should still be able to still have 15-20 switching industries and keep the kids and me happy. Again thanks for the thoughts and input.
You might can get away with a slightly larger helix with flex track, but you might try what I did. I fudged a little, instead of a true circle helix, I used an oval and stretched out 2 areas the same length and opposite sides. That eased the pull up.
Jeff, That was what I thought in the beginning by using possibly 17" Radius and expanding the sides in length by 2 feet to give it a little ease pulling up to the 2nd level. Anything switched on level one, Empty's 5-6 would be brought up by a road switcher. All empty's from level 2 would set on a holding track for the road switcher to pick up and continue to the yard on level 2. The most going up would be 5-6 cars + caboose. Can see no problem coming down with 10-12 cars. Nothing larger than 40 footers. I'll leave that option open, since I'm starting at the Detroit yard (Reduced Drastically for more industry switching) and moving towards the question point. Who knows what the future holds. All track and switches are planned to be hand layed and it might take years to get to that decision.
