Would someone please post formula for calculating profile for a Helix
The profile of a helix is the same as the profile for a grade on a tangent:
Grade (%) = 100xrise/run, graphed as a straight line of constant slope.
The length of the run per turn of the helix is derived by calculating the circumference of a circle:
Circ = 2 x 3.14 x radius. 3.14 is a reasonable approximation of pi if your calculator lacks that key.
If calculating for minimum clearance, the grade should be established before the track enters the helix, and should remain constant until completely clear of any track above or below when exiting the helix.
Note that I gave no numeric values for any variable. They will vary by scale, by desired clearance and are grade and radius specific. Generating a three-dimensional table to cover all possible combinations of scale, radius and clearance is left as an exercise for the student.
Chuck (Modeling Central Japan in September, 1964 - with at least two hairy helices)
Expanding on Chuck's fomulae...
For HO-scale... You will need about a 4" rise (railhead to railhead) for one track to pass over another. A 2% grade is the steepest you'd want to go. Rise = 4"; grade = 2%; Run = y (In N-scale, since you only need to gain 2 to 2.5" per turn, the helix can be a smaller diameter.)
You will need a run of 200" at a 2% grade to gain a 4" rise (does not include vertical easements).
In a helix, the circumference is equal to the run of a single full turn. C (or run) = 200"; pi = 22 / 7; d = diameter (or 2 x radius)
In order to have a helix with a 2% grade gaining 4" with each turn, the helix will need to be at least 63.6363" in diameter (or 31.8181" radius).
REMEMBER...
Chuck / Chateauricher,
Thanks for your tips on building helix. I am planning to build two helices - single track at Algoa and double track near the main door in layout plan below.
The vertical separation between upper deck and lower deck is 14 inches. The single track helix at Algoa is 15" radius so that I can have sufficient aisle space (15" radius is a given)
The double track at main door is 15" radius for outside track and 13" radius for inner track.
For both helices, I want to maintain max 2% grade.
Please advise whether I can fit the helices within given parameters and what else I should watch out for. Thanks in advance.
Chuck, is this N Scale layout? I'll be building my layout in Philippines soon but in H.O. scale Bud(grinstuff)
Hi Jimmylow,
here is some more info on the constuction and experiences with regards to a helix.
http://cs.trains.com/trccs/forums/t/141599.aspx?PageIndex=1
Frank
"If you need a helping hand, you'll find one at the end of your arm."
Thanks Frank. I will study them and try out.
Jimmy
The vertical separation between upper deck and lower deck is 14 inches. The single track helix at Algoa is 15" radius so that I can have sufficient aisle space (15" radius is a given) The double track at main door is 15" radius for outside track and 13" radius for inner track. For both helices, I want to maintain max 2% grade. Please advise whether I can fit the helices within given parameters and what else I should watch out for. Thanks in advance.
Using your existing plan...
My observations on your existing plan:
If you can go with 18" radius curves and 2% grade, here are the numbers you'll get:
I like your track plan. It seems you have managed to include some very interesting details in a small space. Its a good start and I am sure with some tweaking, you'll be able to fit everything in that you want.
By the way, the lower deck will be used for what ?
chateauricher The vertical separation between upper deck and lower deck is 14 inches. The single track helix at Algoa is 15" radius so that I can have sufficient aisle space (15" radius is a given) The double track at main door is 15" radius for outside track and 13" radius for inner track. For both helices, I want to maintain max 2% grade. Please advise whether I can fit the helices within given parameters and what else I should watch out for. Thanks in advance. Using your existing plan... Track length per turn : 94.2478" Rise per turn : 1.8850" (railhead to railhead) Number of turns to attain a 14" change in elevation : 7.4271 JL: Timothy, thanks My observations on your existing plan: 15" radius curves, even in N-scale, are tight. And 13" curves are pushing the limits. You would be better to go with at least 18", particularly if you plan to run longer equipment. JL: Wish I would afford the space. As this is hidden but accessible, any overhang should not be obvious. The 1.8850" rise does not give you much room for the subroadbed and supporting benchwork for your helices. JL: I don't plan to have cork roadbed in helix. I need a longer approach and transition easement into the helix. If you cannot go with larger radius curves, then I suggest you forget about doing a double-track helix with the 13" inner radius. Looking at your plan, you should be able to join the two tracks near "C" and have a single track 15"-radius helix. It appears you may have room here to have an 18"-radius helix. JL: I can forego the 13" inner radius or take a look at 18" option. I will be doing a cardboard mock-up to determine spacing. As for the helix located at Algoa... I would eliminate it and the turning wye; replacing them with a reversing loop. Again, it seems like you can work in an 18" radius loop here. The turning wye you have now does not seem to be large enough to turn more than a single locomotive or car (it looks like its shortest tail is only about 12-15" long). With a loop, you'll be able to turn entire trains. JL: The short track after the wye is meant to hold length of 2 locos - the track is 15". I wanted the Algoa helix to go to lower deck which is Galveston. 18" is too much at Algoa. Already I am squeezing the aisle between Smither's Lake and Algoa to less than 2 feet. As a compromise, operator will stand at Alvin or in front of Smither's Lake. The aisle you have between Algoa and Smither's Lake appears to be very tight. I suggest you work on making it wider. JL: I did a balancing act here, between the space for the Smither's Lake curve and Algoa helix. I wanted to make sure the curves at both locations are 15" radius and take a hit on the aisle. Some of your industrial sidings (particularly in Algoa) are very short -- able to hold only 1 or 2 cars at a time. If that is what your prototype does, then that's ok. But you may want to increase their length. JL: There is no grain elevator in real Algoa (still confirming this fact). I want to model the grain train switching from BNSF and the loading and unloading in Algoa. The intention of the short tracks to hold 3-4 hoppers. A small switcher will do the switching and a local will pull the hoppers to Rosenberg while waiting for the BNSF grain train from Sealy to pick them up and proceed to Galveston. If you can go with 18" radius curves and 2% grade, here are the numbers you'll get: Track length per turn : 113.0973" Rise per turn : 2.2619" (railhead to railhead) Number of turns to attain 14" change in elevation : 6.1895 I like your track plan. It seems you have managed to include some very interesting details in a small space. Its a good start and I am sure with some tweaking, you'll be able to fit everything in that you want. JL: Thanks. I posted in TrainBoard and got good feedbacks on previous plan before settling for this one. The Rosenberg junction was a challenge initially but after spending whole night on it, I think I hit the right cord. Do check out my blog for progress. Yes, I will tweak as I do along. By the way, the lower deck will be used for what ? JL: Lower deck will be Galveston. I have not started work on this yet. But here's the preview. After exiting the Algoa helix, the train will travel a stretch and reach Virginia point, which is directly below the intersection of the UP Glidden and BSNF Galvesto tracks at upper deck. The Galveston causeway stretches from that point west to where the word "Alvin" is. The peninsular will host an industry and the Galveston Bay. The space between Alvin up to Rosenberg on lower deck will be Galveston terminal which will have UP and BNSF yards, intermodal terminal and petrochemical industry. While waiting for Phase 2 Galveston island, I will install a 4 track staging yard beneath Rosenberg. This allows continouous running between Algoa helix and Temple/San Antonio helix (lower wall helix) at lower deck. I will have the mainline installed but not branchlines or yards that Galveston will have. Lower deck track plan is still in my head but I am seeing a clearer vision now :) Thks again, Timothy.
JL: Timothy, thanks
JL: Wish I would afford the space. As this is hidden but accessible, any overhang should not be obvious.
JL: I don't plan to have cork roadbed in helix. I need a longer approach and transition easement into the helix.
JL: I can forego the 13" inner radius or take a look at 18" option. I will be doing a cardboard mock-up to determine spacing.
JL: The short track after the wye is meant to hold length of 2 locos - the track is 15". I wanted the Algoa helix to go to lower deck which is Galveston.
18" is too much at Algoa. Already I am squeezing the aisle between Smither's Lake and Algoa to less than 2 feet. As a compromise, operator will stand at Alvin or in front of Smither's Lake.
JL: I did a balancing act here, between the space for the Smither's Lake curve and Algoa helix. I wanted to make sure the curves at both locations are 15" radius and take a hit on the aisle.
JL: There is no grain elevator in real Algoa (still confirming this fact). I want to model the grain train switching from BNSF and the loading and unloading in Algoa. The intention of the short tracks to hold 3-4 hoppers. A small switcher will do the switching and a local will pull the hoppers to Rosenberg while waiting for the BNSF grain train from Sealy to pick them up and proceed to Galveston.
JL: Thanks. I posted in TrainBoard and got good feedbacks on previous plan before settling for this one. The Rosenberg junction was a challenge initially but after spending whole night on it, I think I hit the right cord. Do check out my blog for progress.
Yes, I will tweak as I do along.
JL: Lower deck will be Galveston. I have not started work on this yet. But here's the preview. After exiting the Algoa helix, the train will travel a stretch and reach Virginia point, which is directly below the intersection of the UP Glidden and BSNF Galvesto tracks at upper deck. The Galveston causeway stretches from that point west to where the word "Alvin" is.
The peninsular will host an industry and the Galveston Bay. The space between Alvin up to Rosenberg on lower deck will be Galveston terminal which will have UP and BNSF yards, intermodal terminal and petrochemical industry.
While waiting for Phase 2 Galveston island, I will install a 4 track staging yard beneath Rosenberg. This allows continouous running between Algoa helix and Temple/San Antonio helix (lower wall helix) at lower deck. I will have the mainline installed but not branchlines or yards that Galveston will have.
Lower deck track plan is still in my head but I am seeing a clearer vision now :)
Thks again, Timothy.
As it just so happens, I just recently finished writing code to help people figure out grade on a helix. Gather your rise and your radius and head on over to......
Helix Grade Calculator
I still have to write the instructions, but remember, rise is the distance between railheads! This includes all roadbed, support structures, etc....
jimmylow chateauricher 15" radius curves, even in N-scale, are tight. And 13" curves are pushing the limits. You would be better to go with at least 18", particularly if you plan to run longer equipment. Wish I would afford the space. As this is hidden but accessible, any overhang should not be obvious.
chateauricher 15" radius curves, even in N-scale, are tight. And 13" curves are pushing the limits. You would be better to go with at least 18", particularly if you plan to run longer equipment.
Wish I would afford the space. As this is hidden but accessible, any overhang should not be obvious.
I was not talking about overhangs; but about the ability of your locomotives and rolling stock to actually negotiate such tight curves without de-railing. I suggest you get some flextrack and test curves of various radii to see just how tight a curve your equipment can manage. Personally, I would not go with curves any smaller than 15".
jimmylow chateauricher The 1.8850" rise does not give you much room for the subroadbed and supporting benchwork for your helices. I don't plan to have cork roadbed in helix. I need a longer approach and transition easement into the helix.
chateauricher The 1.8850" rise does not give you much room for the subroadbed and supporting benchwork for your helices.
I don't plan to have cork roadbed in helix. I need a longer approach and transition easement into the helix.
Yes, by not having cork roadbed, you will save some headroom. However, by "subroadbed," I was refering to the structure supporting your track -- ie: the deck.
By beginning your grade prior to entering the helix proper, you will reduce the length of the helix (ie: the number of turns). The total length of the grade (about 700") between your levels does not have to be completely within the helix itself. It can include the approaches to the helix (at the top and/or bottom).
graphitehemi As it just so happens, I just recently finished writing code to help people figure out grade on a helix. Gather your rise and your radius and head on over to...... Helix Grade Calculator I still have to write the instructions, but remember, rise is the distance between railheads! This includes all roadbed, support structures, etc.
I still have to write the instructions, but remember, rise is the distance between railheads! This includes all roadbed, support structures, etc.
It is a bit unclear... Is "rise" the rise per turn or the total rise of the helix (ie: distance between levels) ?
Unfortunately, when I used your calculator with the OP's numbers (14" total rise; 15" radius), I get a 14+% grade ! It doesn't tell me how many turns are needed, or how long the total run would be -- variables I really need to know when building a helix.
A good helix calculator should includes these variables:
By providing any 3 variables, you should be able to calculate the others.
Is there any way your helix calculator can include these variables ?
chateauricher jimmylow chateauricher 15" radius curves, even in N-scale, are tight. And 13" curves are pushing the limits. You would be better to go with at least 18", particularly if you plan to run longer equipment. Wish I would afford the space. As this is hidden but accessible, any overhang should not be obvious. I was not talking about overhangs; but about the ability of your locomotives and rolling stock to actually negotiate such tight curves without de-railing. I suggest you get some flextrack and test curves of various radii to see just how tight a curve your equipment can manage. Personally, I would not go with curves any smaller than 15". JL: Okay, I will test it out. Based on John Armstrong's Track Planning for Realistic Operation, 14 inch is considered conventional (normal) and 17 inch is broad. Let me test if I can increase the radius. The same goes to elsewhere on the layout to give a smoother curve. jimmylow chateauricher The 1.8850" rise does not give you much room for the subroadbed and supporting benchwork for your helices. I don't plan to have cork roadbed in helix. I need a longer approach and transition easement into the helix. Yes, by not having cork roadbed, you will save some headroom. However, by "subroadbed," I was refering to the structure supporting your track -- ie: the deck. By beginning your grade prior to entering the helix proper, you will reduce the length of the helix (ie: the number of turns). The total length of the grade (about 700") between your levels does not have to be completely within the helix itself. It can include the approaches to the helix (at the top and/or bottom). JL: The easement is necessary. I will keep the above in mind. Once again, thanks!
JL: Okay, I will test it out. Based on John Armstrong's Track Planning for Realistic Operation, 14 inch is considered conventional (normal) and 17 inch is broad. Let me test if I can increase the radius. The same goes to elsewhere on the layout to give a smoother curve.
JL: The easement is necessary. I will keep the above in mind.
Once again, thanks!
chateauricher It is a bit unclear... Is "rise" the rise per turn or the total rise of the helix (ie: distance between levels) ? Unfortunately, when I used your calculator with the OP's numbers (14" total rise; 15" radius), I get a 14+% grade ! It doesn't tell me how many turns are needed, or how long the total run would be -- variables I really need to know when building a helix. A good helix calculator should includes these variables: radius; grade; total rise, level to level; rise per turn (to ensure adequate clearances); and number of turns. By providing any 3 variables, you should be able to calculate the others. Is there any way your helix calculator can include these variables ?
As I said, I still have to write the instructions. Assuming your in N scale, 14" rise would take 7 turns at 2" to clear the trains (only assuming the clearance needed). So 2" Rise with a 15" Radius gives you a 2.12% grade with the calculator. It's only made to help you figure out grade in a helix. Once you know the grade to go 360 degrees, you can easily figure out how many times to go round and round. Which is basically what you went over in your first post on this thread.
Algoa Helix Calculation
Timothy / Craig
I relooked into the assumptions and the space I have and came out with the above rough calculation. Using Algoa single track helix as example, for an effective radius of 15 inches, the circumference is 94.2 inches while 16 inches radius has 100.5 inches.
Q: When you talk about helix radius, are you refering to the helix edge or to the track center? If it is the former, at 15 inches radius and 2% grade, the rise is 1.885 inches. In the latter, at 16 inches radius and 2% grade, the rise is 2.0 inches.
As I want 15 inches radius which is to the track center, I will leave a 1 inch space between track center and helix edge (total width of helix part that support track = 2 inches).
I have now considered 2.5% grade in the helix and throughout my layout. Is 2.5% grade acceptable for N-scale?
At 16 inches effective radius and 2.5% grade, I get 2.5 inches vertical separation between levels (roadbed to roadbed). Is this clearance suffice for autorack and stack cars?
With 14 inches between levels, I get 5.6 turns at 2.5% grade. And with 8 support columns for the helix, the support column is positioned at every 12.56 inches of the arc (center line of support column)
Pls verify my understanding.
Thks, Jimmy Low
I have created a stacked helix calculator. Download here http://www.savefile.com/projects/808751807
You can calculate single track and double track helices, up to 3 levels. Email me if you have any questions.
jimmylow Algoa Helix Calculation I relooked into the assumptions and the space I have and came out with the above rough calculation. Using Algoa single track helix as example, for an effective radius of 15 inches, the circumference is 94.2 inches while 16 inches radius has 100.5 inches. Q: When you talk about helix radius, are you refering to the helix edge or to the track center? If it is the former, at 15 inches radius and 2% grade, the rise is 1.885 inches. In the latter, at 16 inches radius and 2% grade, the rise is 2.0 inches.
Yes, measurements are to the centre of the track, whether curved or straight.
As I want 15 inches radius which is to the track center, I will leave a 1 inch space between track center and helix edge (total width of helix part that support track = 2 inches). I have now considered 2.5% grade in the helix and throughout my layout. Is 2.5% grade acceptable for N-scale?
2.5% is do-able; however, you may find you'll need to either add extra locomotive power or restrict the length of your trains in order to climb that grade.
Yes. 2.5" should be amble clearance for such cars. According to the NMRA's Recommended Practices for N-scale overhead clearances, the minimum should be 1-21/32" (1.65625") or 42.1mm ( http://www.nmra.org/standards/sandrp/s-7.html ). You'll be left with about 0.84375" (21.4313mm) for your benchwork and supports. If you want to be absolutely sure, put a piece of track on a table (with cork roadbed if you're using any) and place your tallest car on the track; then measure how high they are from table to top of the highest point on your car. I would then add about 0.25" (6.4mm) to get the minimum clearance your trains require.
With 14 inches between levels, I get 5.6 turns at 2.5% grade. And with 8 support columns for the helix, the support column is positioned at every 12.56 inches of the arc (center line of support column).
You might be able get away with 6 equally-spaced supports.
graphitehemi chateauricher It is a bit unclear... Is "rise" the rise per turn or the total rise of the helix (ie: distance between levels) ? [snip] As I said, I still have to write the instructions. Assuming your in N scale, 14" rise would take 7 turns at 2" to clear the trains (only assuming the clearance needed). So 2" Rise with a 15" Radius gives you a 2.12% grade with the calculator. It's only made to help you figure out grade in a helix. Once you know the grade to go 360 degrees, you can easily figure out how many times to go round and round. Which is basically what you went over in your first post on this thread.
chateauricher It is a bit unclear... Is "rise" the rise per turn or the total rise of the helix (ie: distance between levels) ? [snip]
[snip]
Yes, that may be true. However, your calculator (as I tried it last week) does not say if the rise is the rise per turn or the total rise of the helix (distance between levels). You should make that more clear when you write the instructions.
chateauricher jimmylow Algoa Helix Calculation I relooked into the assumptions and the space I have and came out with the above rough calculation. Using Algoa single track helix as example, for an effective radius of 15 inches, the circumference is 94.2 inches while 16 inches radius has 100.5 inches. Q: When you talk about helix radius, are you refering to the helix edge or to the track center? If it is the former, at 15 inches radius and 2% grade, the rise is 1.885 inches. In the latter, at 16 inches radius and 2% grade, the rise is 2.0 inches. Yes, measurements are to the centre of the track, whether curved or straight. JL: Thanks. I can push for better rise by measuring center to the helix edge. Cheat a little. I can have 15 inc to track centre and 16 inc to helix edge and use 2.5% GOS to get me 2.5 inc rise per run. As I want 15 inches radius which is to the track center, I will leave a 1 inch space between track center and helix edge (total width of helix part that support track = 2 inches). I have now considered 2.5% grade in the helix and throughout my layout. Is 2.5% grade acceptable for N-scale? 2.5% is do-able; however, you may find you'll need to either add extra locomotive power or restrict the length of your trains in order to climb that grade. JL: Okay, got to experiment the pulling power of 2 locos and 3 locos where are typical of UP and BNSF trains in this region. The helper will be great addition on longer coal trains. At 16 inches effective radius and 2.5% grade, I get 2.5 inches vertical separation between levels (roadbed to roadbed). Is this clearance suffice for autorack and stack cars? Yes. 2.5" should be amble clearance for such cars. According to the NMRA's Recommended Practices for N-scale overhead clearances, the minimum should be 1-21/32" (1.65625") or 42.1mm ( http://www.nmra.org/standards/sandrp/s-7.html ). You'll be left with about 0.84375" (21.4313mm) for your benchwork and supports. If you want to be absolutely sure, put a piece of track on a table (with cork roadbed if you're using any) and place your tallest car on the track; then measure how high they are from table to top of the highest point on your car. I would then add about 0.25" (6.4mm) to get the minimum clearance your trains require. JL: Great. I will read the RP. My tallest train will be stack trains which is 1.75 inches high from subroadbed to top of stack (no cork roadbed in helix). I am using 0.5 inch plywood as subroadbed. That gives be a clearance of 0.5 inch. With 14 inches between levels, I get 5.6 turns at 2.5% grade. And with 8 support columns for the helix, the support column is positioned at every 12.56 inches of the arc (center line of support column). You might be able get away with 6 equally-spaced supports. JL: I chose 8 so that 4 of them will hold the joints and another 4 provide support between the quarter arcs. Thks for advice, Timothy. Looks like my stacked helix calculator is okay.
JL: Thanks. I can push for better rise by measuring center to the helix edge. Cheat a little. I can have 15 inc to track centre and 16 inc to helix edge and use 2.5% GOS to get me 2.5 inc rise per run.
JL: Okay, got to experiment the pulling power of 2 locos and 3 locos where are typical of UP and BNSF trains in this region. The helper will be great addition on longer coal trains.
JL: Great. I will read the RP. My tallest train will be stack trains which is 1.75 inches high from subroadbed to top of stack (no cork roadbed in helix). I am using 0.5 inch plywood as subroadbed. That gives be a clearance of 0.5 inch.
JL: I chose 8 so that 4 of them will hold the joints and another 4 provide support between the quarter arcs. Thks for advice, Timothy.
Looks like my stacked helix calculator is okay.
A brief comment on railhead-to-railhead clearance, grade and curvature:
When it comes to track geometry, an ounce of testing trumps a ton of opinion. Mock it up, try your own rolling stock and the dictates of your chosen prototype (or home-grown) operating standards, then decide what to do based on cold, hard facts.
Chuck (Modeling Central Japan in September, 1964)
Thks for sharing your comments.
I am planning to use 2.5% GOS on 16 inches radius to helix edge (or 15 inches to track center). This gives me good clearance with 0.5 inch margin over my tallest car.
Here are the snapshots from my stacked helix calculator for a 2% and 2.5% GOS on 16 inches radius.
2.0% GOS
2.5% GOS
At 2.0% GOS, the effective grade on track is 2.02% while a 2.5% GOS, the effective grade is 2.55%. While 2% is recommended, pushing it to 2.5% but not more than 3.0% is probably doable. Like you said, mock it up and test out.
jimmylow I have created a stacked helix calculator. Download here http://www.savefile.com/projects/808751807 You can calculate single track and double track helices, up to 3 levels. Email me if you have any questions.
Any comments on my stacked helix calculator? Tell me if you discover any bugs or if it is not that user-friendly.
Regarding the track plan:
1. It seems that with minor modification, one double-track helix would be sufficient, so need for second helix could be eliminated.
2. There is room, particular for the helix under Algoa, for straight track sections to be added (giving the helix a semi-rectangular shape rather than semi-square) so that the grade in the helix could be reduced significantly.
Mark
Just a thought for saving headspace in your helix:
Use 1/4 inch hardboard for the road bed, perhaps covered with 1/16 inch cork to deaden the sound and cut a groove in the vertical supports (inside and outside) into which the hardboard is glued. Don't forget to add a lip inside and outside between the vertical supports to keep derailments contained.
Thks Mark and Railfan8. I will jot them in my Ideas Book for construction consideration
I'd be a little careful about using 2.5" rise per turn with N gage. I think you would want to provide side protection inside and outside to prevent derailments from ending up on the floor. Even without this, 2.5 inches is a pretty small space in which to get to and realign the occasional derailment that stays on the roadbed.
I could not squeeze more aisle space if I want to maintain 2.0% GOS.
Thks for highlighting the side protection.
Here's a thought for an easy way to put in a helix
Buy it. See pg. 18 May issue MR for Ashilin Designs Railroad Miniatures.
Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/
Further to this tread. An excellent Helix article in May/June 2003 N-Railroading, N scale Helix helper. Thank you to everyone for their input, have used a bit of all ideas.
Jacobo