carl425the only reason I can think of for extra clearance is to be able to reach in and re-rail a car. That's not going to happen with anything short of 6+ inches and you won't get that with a helix so why have more grade than necessary?
Also a good point!
This will require some thinking and a bit more measuring of rolling stock on my part. Lowering the grade would seem to be a smart choice assuming that the reduced grade will lessen the forces that typically cause problems in helices. However, building something that does not allow wayward cars to be retrieved relatively easily would be a poor choice.
Gentlemen, thank you for your points of view.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
cuyamaMore importantly (for me), I personally just want more than .1" leeway should something go slightly awry in construction or if things warp or shift slightly over time.
Good point!
At a LHS they are building a small scenic H0 layout based in the Canadian Rockies, with two individual levels, one for CN and the other for CP. As they will run passenger cars, one of the people there told me that they had problems with 24" or 25" curves and had to re-do the curves to 27", iirc. The diaphragms were rubbing against each other and causing derails. So, I guess it would be the same in a helix. :)
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hon30critterSince I'm modelling the transistion era my actual clearance would seem to be greater than the 3.03" recommended by the NMRA. That is assuming 1/2" for the helix roadbed plus the height of the track. Do you feel that the NMRA recommendations are too tight?
The NMRA Standard is sufficient for properly scaled equipment. Some model equipment rides a bit high (more true for older models than for recent models).
More importantly (for me), I personally just want more than .1" leeway should something go slightly awry in construction or if things warp or shift slightly over time.
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Looks good. Since I have 89' rolling stock, even 30-inches seems tight for a helix so I would do some research and get feedback before building even a 30 incher.
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hon30critterDo you feel that the NMRA recommendations are too tight? What would you recommend?
Take a look at these:
http://www.icrr.net/plates.htm
No disrespect to Byron, but he and the NMRA, rather than being concerned with what will work, are more interested in what will never fail - even in a worst case scenario with less than skilled construction, out of scale models, changing interests... If I had a professional reputation to protect as he does, I would probably take a similar position.
For me, I'm more interested is doing what I can get away with to allow for a more interesting plan. What I did was measure the rolling stock I wanted to run, looked at the AAR specs and set my own clearance to keep my grade to a minimum. Assuming you aren't planning for future rolling stock, the only reason I can think of for extra clearance is to be able to reach in and re-rail a car. That's not going to happen with anything short of 6+ inches and you won't get that with a helix so why have more grade than necessary?
If you want to get the most out of your space, measure your stuff, do some tests, and set your own standard based on a level of risk you can live with.
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
cuyamathat's tighter than I would personally feel comfortable with.
Byron:
Since I'm modelling the transistion era my actual clearance would seem to be greater than the 3.03" recommended by the NMRA. That is assuming 1/2" for the helix roadbed plus the height of the track. Do you feel that the NMRA recommendations are too tight? What would you recommend?
Thanks,
cuyamaHopefully it will work fine for you. As you probably know, NMRA S-7 specifies 3.03" clearance for transition-era standard gauge HO and 3.15" for modern-era.
Because of tight tunnels, the N&W line I'm modeling is restricted to "plate B" which has a max height of 15'1" (2.08" when scaled down). I'm satisfied with 1/2" to spare. My tallest caboose stack clears by a full 1/4".
cuyamaPersonally, I wouldn't cut it as close as you are for myself or for a client, but best of luck with your layout.
If I were designing the layout for a client, I would also tend to be more conservative.
I planned going in to build it like this and run what worked. Imagine my pleasure when I found I could pull the full length train I was shooting for with only half the power I plan to run. Good luck indeed.
hon30critter I think I'll stick with my plan for a 30" radius with 3.75" track separation at a 2% grade.
Note that railhead-to-railhead elevation and clearance are two different things, as you probably know. 30" at 2% yields a railhead-to-railhead elevation difference of 3.75", but after allowing for subroadbed (say ½") and the height of the track (say 1/8"), the clearance is only about 3 1/8" (3.125"). Compared to the NMRA S-7 recommended clearances of 3.03" and 3.15", that's tighter than I would personally feel comfortable with.
But I'm conservative ... because I don't want to have to rebuild anything due to cutting the tolerances too close and making a small error somewhere. (Or for my clients to have to rebuild ...)
I'm not posting here to be critical of Carl, but only to point these issues out to others who may see a 24" radius helix in HO and extrapolate to think 24" is fine for every piece of HO equipment, even full-length passenger cars, big locos, and double-stacks. It won't be.
hon30critterWhat is the longest car that you have run on your Helix? To re-phrase, do you think an eight car passenger train with 85' cars and an ABA consist would run on it?
The SD40-2 at 70' is the longest thing my layout will see. I'm running freight only and nothing over 50' which is appropriate for the section of the N&W I'm modeling. The traffic will be mostly 100 & 70 ton coal hoppers with only 2 mixed freights per modeled day.
In the 50 years I've been at this hobby, I've never had an interest in running passenger trains so I can't help you with your 85 footers, but based on the coupler swing on my 70' locomotives, I can't imagine full size passenger cars with body mounter couplers would like my 24" radius. Maybe truck mounted couplers, but they come with their own problems.
What I can tell you from my experience is that if you can live with less than full NMRA clearance, a helix of whatever radius your stuff will run on would be worth a test.
Dave, I have a stack of unbuilt Branchline 80 footers myself. I don't like passenger cars without realistic close coupled diaphragms, which increases the minimum radius, so I am planning on a 36 minimum radius for the main.
I have come to this conclusion after scouring the Internet for opinions on the subject. I am leaning mostly on statements by well known modelers with years of experience under their belts. I am not entirely happy with this, but it is what it is.
CG
CentralGulfOr are you talking about the number of cars, Dave?
CG:
I'm not very knowledgeable of the dynamics of helices, but I would need to be able to run my version of the Canadian Pacific 'Canadian' on mine. I currently have seven Walthers 85' passenger cars and one shorter baggage car, plus the ABA consist of FP 7s/9s. I won't make the train any longer because it wouldn't fit on my passenger station track if I did. As you may be aware, the Walthers cars have body mounted couplers. If I understand what I have read, 24" is pushing things for the 85' cars on a flat curve so I'm a bit suspicious of trying to run them up a helix of the same radius. I noticed that the OP was running 3 bay hoppers which is a totally different thing.
Actually, I think that I have already reached my own conclusions. Putting 85' passenger cars with body mounted couplers on a 24" radius helix is inviting trouble, especially with the very minimal overhead clearance that the OP's design allows. I think I'll stick with my plan for a 30" radius with 3.75" track separation at a 2% grade. Byron's reference to the NMRA recommendations suggests that I could shave the track separation and reduce the grade a bit.
Cudos to the OP.
Thanks
carl425Clearance is 2.59"
Hopefully it will work fine for you. As you probably know, NMRA S-7 specifies 3.03" clearance for transition-era standard gauge HO and 3.15" for modern-era.
The smaller clearance you are using allows for a lesser grade. Based on others' experience with similar HO helix radii, longer cars and lighter cars (such as empty open tops) might still have a tendency to stringline, so if you plan to run those uphill, that might be worth a test before you button everything up.
Personally, I wouldn't cut it as close as you are for myself or for a client, but best of luck with your layout.
Not an expert, but my math agrees with Carl. 1/2 inch plywood I presume, with flex track laid directly on the wood when under another turn for a 2.1% grade. With the stated clearance, it all adds up.
Or are you talking about the number of cars, Dave?
carl425:
Well done! Your numbers seem to defy the 'experts' a bit but seeing is believing.
What is the longest car that you have run on your Helix? To re-phrase, do you think an eight car passenger train with 85' cars and an ABA consist would run on it?
I just spent a bunch of time adjusting my planned helices' radii from 26.5" to 30". Now I'm wondering if I needed to do that.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
We've talked about this a few times so I figured I owed those that offered advice "closure". Here's a test run.
My goal was 18-20 cars with 12 axles of power. I'll take 19 cars with only 6.