The earlier tip on the wheels was very eye-opening, and prompted me to do a test this evening. Some of my cars would roll down a ~1.5% incline by themselves, others felt smooth but would need a nudge every foot or so. There didn't seem to be much rhyme or reason as to which rolled best - new vs. old, car type, weight etc. Everything is running on MTL trucks & wheels. Very curious and will need some further investigation. I cherry picked the most free-rolling of the bunch and (if my math is correct) I managed to get my smallest loco (0-6-0 steam) to pull 8+ freight cars up a 1.3% grade. My two-truck Shay did even better, and I ran out of track before I found the Mikado's limit. A massive difference from my first try with the 2% grade and random selection of cars. I'm still struggling with track planning, but my hope is to have a coal mine on the lower level, connected to the mid level (main track) via a helix or grade, and then a higher upper level that'd likely be a standalone track. Originally, I'd hoped to fit in the mine, a small industrial area with switching yard, a farm, and a backshop/depot with turntable into my 8x3' area. Now that I've seen the size of my assembled buildings, I realize I've got less space to work with than I originally thought if I want to maintain a reasonable sense of scale, so will likely have to ditch a couple of items from my wish-list.
Isn't that the way it is. Ditching a couple of things you want to put on your layout. You aren't alone. That's okay. You'll figure it out.
I've tried out the effective grade calculator and learned that with my available radius of 15", a helix adds 1% to the effective grade vs. a straight track (2.3% vs. 1.3%). If I were to 'split' the helix so it's an oval with flat curves connected by inclined straights, how would that compare versus one single straight? Presumably the curves will still cause more resistance than a straight, but not as much as an inclined curve? If there's any trick or formula to help figure that out, it'd be a massive help. thanks again all!
Taymar, First response is to adding straight track to a section of the helix. I've done that and it works amazingly well. If not a straight section then I widened the curve out thus reducing the resistance. I did that on my mainline to get from the second level to the top level. Thus giving me some viewable train running footage. As to the math and calculation. I think you answered your own question. I think you hit the nail on the head. Sounds like what I learned in geometry and my architectural drafting classes. I'm interested in your calculator and where I could find such. I can say, that's my experience. I've played with the math but didn't come up with anything significant or provable. I need a working geometry car like the prototype. There should be percentage information out there based on the prototypes. I would think it would hold true for model railroaders...to a point. What I've experienced is: The tighter the curve the more resistance. That's true on a flat layout as well. In the helix I pushed my curves out to a minimum of 22". Thus reducing the drag. Rule of thumb: As experienced by most of my model railroading friends. On a flat, the tighter the curve, the more difficult it is for the train to pull through them. The drag/resistance is increased. Now add a grade, dependent on the gradient... ditto. Off the cuff solution, usually requiring us to reset the throttle just a bit higher. As Randqust pointed out: The tighter the curve and wheel slip becomes a problem. I could get into the traction tire issue or tractive effort. I won't. Just keep in mind most of my locomotives are bare metal to metal, wheels to rail. It gets a little tougher to deal with. Personal preference. Never mind the possibility of string-lining your train on the tighter curves. I don't like picking up my train cars up off the floor. There's another anomaly that occurs. As you look at my helix-i with four tracks side by side. The inside curve is actually steeper then the outside curve. Try wrapping your head around that one. You might be curious. While living in Big Bear Country, SoCal. My friends are all mountain railroad types. No flat-landers in the group. We love our mountain railroads. You will too. Best of luck. You are on the right track. No pun intended.
I've got a helix that is racetrack shaped - two half circles separated by short straights - to fit the space available. Does this cause more resistance than a circular helix with the same track length per rise and the same rise per rev? To lower the grade, use a thin sub roadbed (I use Formica instead of plywood) and skip the cork roadbed entirely. It reduces the rise per rev without increasing the size of the helix.
Gotcha, I think. You want to reduce the distance between the upper and lower deck. Am I right? I did the same thing with a different twist. I wanted to increase the distance between the top of the rail to the bottom of the upper structure. I eliminated the roadbed gluing the track directly to the 1/2" particle board. Easy to work with, cut and shape for a grade. Thus allowing me to minimize as much as possible the grade. However, to make the needed climb and keep it to a 2% or 2.2% grade I had to push my curves out. Now, I need to say this. If you are using 9 3/4" curves and you think a 9" straight at the quarter turn will solve your problems. Not at all. You can play with that if you so desire. It won't get the job done. Check and see what grade you'll be required to use. I promise you it will teach you what you need to know...in a hurry. Don't ask me how I know. Remember this isn't about me but about me sharing what works best. Hang in there!
Regarding the drag effect of putting a straight section into a circular helix: To get a reasonably accurate understanding of the effect, you need to consider how much of your train is on what parts of the helix. The total effect is an accumulation of the effects of the parts. If you had a helix made up of level curves of a radius that gives the same effect as a 1% grade, and had two half circles of that curved track connected with straight sections at a 1% grade, it would calculate out to an effective 1% grade for the entire run. (Except, in reality, there is actually some "transition" resistance between curves and straight sections, in both the horizontal and vertical directions, which can be reduced by easements.) But, if you don't have a constant resistance along the path, then you need to consider how much of the train is on each part of the path with different characteristics. Assuming that all of the cars are the same, then 40% of the train on a section that is straight and has a 1% grade and 60% of the train is on a curved section with a combined grade plus curve resistance equal to a 2% grade, then the net effect (neglecting transitions) is (0.4 x 1% + 0.6 x 2% =) 1.8%. But, for most of us, our cars are not equal with respect to drag, due to differences in weight, length, wheel types, crud build-up, etc. etc. etc. So, as different parts of the train move from straight to curved and level to graded sections of a variable helix, the drag will change, even if it is theoretically set up so that all parts (that are dissimilar in grade or curvature) have "equivalent grade." So, while this way of thinking helps us understand what is going on, it is really too difficult to predict what will happen in other than trivial cases (such as a circular helix with good vertical and horizontal easements at entry and exit points), because there are so many uncontrolled variables. Experience is the best teacher, but most of us don't have the time or money to learn everything "the hard way" on our own. That is why forums like this one are so valuable - we can learn from each other's mistakes and successes. So, posts to this thread that indicate success with a helix of a particular design would help us most if they also included the types of cars that are successfully navigating those designs, particularly their lengths and relative overhangs. Similarly, particular problems with car types on specific trackage sections would help us avoid learning those lessons the hard way.
My 'nolix' created the need for another invention, the dynamometer/spring scale car. I was trying to determine how much drag each train created, and where, coming up around my nolix to grade portion. I rigged up a school-grade spring scale with trucks on it, it worked, it's really crude, but it can be watched while going uphill. And I can also measure the effects of dirty vs. clean wheelsets, new vs. old. I have almost entirely MT wheelsets. As they crud up, two things happen: First, they will build up the 'crud' on the treads that's a mix of carbon from oxidation, dust, a little oil sometimes, etc. It can build up pretty good to the point I got an ultrasonic cleaner to do big batches at once. Removing that helps a lot..but... over time you'll also see the treads 'scuff up' loosing their polish. Scuffed wheels drag a lot more in curves, my sharpest curve coming out of the staging yard is 11", and you can certainly see it. So the other thing is that the curve resistance on a grade is not a constant, it's an increasing variable as wheels both get dirty and scuff up. My estimate is about 20% more drag before full wheel cleaning, which is enough to cause regular maintenance. I don't think you'd have the variability with metal wheels, but if you did, you might even have more resistance. Part of that is on how much taper the treads have, but on curves as sharp as we have, the cars are yanked to the inside of the railhead right up against the flange anyway, so the benefits of tread taper under load are pretty much nonexistent. I have a 'loop to loop' on my tiny portable logging layout (18x36) with a 4.5% grade and 9 3/4 curve on it, hidden loop climbing to visible loop. Given that, an Atlas 2-6-0 or a Rapido 2-6-0 can manage 4 40' cars and a caboose. Period. And when the wheels get scuffed up enough, it can't do that and in that case I simply rewheel the cars and it solves the problem. So the curve drag is significant, my rolling lab rats can prove it.
One thing no one has mentioned it transit time. With my 42" diameter helix, I would allow a train to enter it at the usual slow speed I operated trains, and then came back the next morning to see it come out the top, or so it seemed. My main criticism of helices, or any hidden running for that matter, is the time that it wastes.
t=S/V, your train engineer has to speedup or the helix have to be replaced by an elevator. Once, it was a slow train. It was so slow that the passengers had the time to collect mushrooms.
Well, at least it saves the effort and expense of implementing a "fast clock" to make the points on the layout seem farther apart.
This isn't meant to be a put down to those who like and use Elevators. Noting some difficulties. One difficulty with an elevator is the length of the train. If you operate short trains it might work for you. Operate 40 to 50 car freight trains or 10 to 12 car passenger trains, with 3 to 4 engine lash ups, then you will have problems. You'll soon learn having an elevator that is long enough to handle those trains may be an engineering marvel or nightmare. Where as a helix has a tendency to lift the cars without the added steps it takes to get your train on and off an elevator. Just a part of the run time. Ask someone who has tried building an elevator. A fellow model railroader friend of mine indicated, after trying it, it was a nightmare to operate. Tracks wouldn't line up. Access loops to the elevator could consume as much track as a loop. The elevator had to be hidden, like a hidden staging yard. Pulleys didn't always work right. Never mind there are design problems and flaws to be aware of. The time it takes a train to negotiate a helix is seen by some of us as the same time it takes for instance to get a 1:1 foot scale train through the real loops. Tehachapi loop which is all but a mile long also the Williams Loop, all in California. Now go to Canada and there is a tunnel loop check out how long it takes for a train to make it through it. Sorry name of such escapes me right now. Some of us like the fact a train disappears into a helix, even if it does take some time for it to eventually reappear on the layout. Beats watching them run around in circles and adds to the mystique. Of course on mine you can see the train pull through the helix, with meets often the case and it breaks up the monotony of waiting. Impatient souls we are. Just some things to look at.
It was just a humor attempt. Just a thought, for long trains a 1 1/2 or 2 turns of helix can be lifted. Ofcourse the alignment needs special care.
LOL Got it!! Actually you made a good point. Everything has it's place. I've seen elevators work how be it awkwardly. One place I visited they had an elevator, dead end spur, that was in the laundry room. A round the room,double deck, shelf type basement layout. My first question, how do you turn your trains? Answer, by utilizing the run around. They had switches on both ends and a single by pass or better said run around track. Trains were limited in size. Ten car freight trains and 3 car passenger trains. Keeping in mind there simply wasn't room for a helix. Hardly room for the elevator. Just some of the challenges we all face.
Sometimes we have to be self-denying or "shelf-denying". We can't defeat the limited space without dealing with it's limits.
