HO Helix kits

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K

kbbgood

New Member
Building a 22" 2.5 foot raise helix seams like a lot of waiste if all I get is 2 loops per sheat of plywood. What can I do better? Isthere kits I can get for not a lot of money ? Am I missilg something building my own? Not ready yet to start but house almost paid for and will be building a grage soon with a 12 by 24 room on the end just for me and a few bit totes full of ho train stuff.
 
Check with a Google search since there are many site that have template for building a helix and U Tube video that may offer some ideas.

Greg
 
You are missing something. Why not build the helix from 1/2 circles or even 1/4th circles, so that the parts nest together allowing a minimum amount of waste?
 


kbbgood said:
Building a 22" 2.5 foot raise helix seams like a lot of waiste if all I get is 2 loops per sheat of plywood. What can I do better? Isthere kits I can get for not a lot of money ? Am I missilg something building my own? Not ready yet to start but house almost paid for and will be building a grage soon with a 12 by 24 room on the end just for me and a few bit totes full of ho train stuff.
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I have done a fair amount of reading on helix subject lately, and it appears to me that 22" radius is just too small. I even considered 24", but eventually was convinced that 30" is a much better idea,...particularly if you are going that high. Lots of info and images on the web.

And since it sounds like your project may be somewhat in the future, you might just take a look at my little experiment with PVC tubes that I hope to conduct in the next several months.
http://www.modelrailroadforums.com/forum/showthread.php?40316-Building-a-Helix-with-PVC-Pipe
 
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I would agree, in HO, a 22 inch radius is too tight of a radius and that 30 inches is a better choice. I would also say that a grade of around 2% is where you want to stay. unless helpers are going to be apart of your operations.
 
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Ashlin Designs makes several helix kits in both HO and N. They will also make custom heights in multiples of their kits, which are made in 90 degree segments, out of 1/4" plywood. Bought one, haven't used it yet, but seems like it would do the job. I got the 24-28" radius kit in HO. good luck.
 
If you are a MR Video Plus subscriber, David Popp just had a great video on laying out Helix cuts for their Canadian Canyon Layout Series. Very little waste...lots of pieces.


Sent from my iPad using Tapatalk
 
Yes, 22" radius is not a good idea. There is a thing called grade equivalent where the curvature of a helix causes a train to experience a grade significantly higher than the simple rise/run grade. One guy explained it wells as follows:

"The difference between the 4% and 2.5% for a 24" radius is caused by the grade equivalent. Grade equivalent, which was discussed earlier in this tread, is the drag (expressed as a grade) that a train sees from going through a curve. There is actually a complicated formula to figure this out, however there is also an easy rule of thumb for HO. Basically 32/radius of the curve= grade equivalent. So a train going through a LEVEL 24" radius curve will experience a drag equivalent to a 32/24 = 1.33 degree grade. So if a 24" radius helix produces an actual 2.65% grade (~2.5%) then the train will experience an almost 4% grade. The minimum radius I would use for a helix is 30 inches if you have the room."

There is a lengthy discussion at MRH forums that also might be good to read.

http://model-railroad-hobbyist.com/node/28784?page=4

So keeping in mind if you have a 30" radius track helix and want a 2% actual grade, your going to get 3.8" rise for every 360 degree turn. Remember, circumference = 2 x Pi x Radius and Grade = Rise over Run.

So even with the above 30" radius helix, the train is going to experience a grade, due to drag of the curve will be 3.3% (2.0 actual plus 1.3 drag equivalent) and that's assuming a separation of 3.8 inches between turns allows sufficient clearance when taking into account subroadbed thickness and track etc. I'd allow for a full inch for that, so with a 30" radius curve helix at 2.0% actual grade with 1 inch thickness and 1/16" track - you'll have 2.6 inches over the head of the rails. Is 2.6 inches enough to clear your tallest rolling stock? What about finger space if you need to re-rail cars? Just some factors to figure in on.

Bottom line is if you thought 2.0% was the grade you were getting with a 30" radius helix, in reality the trains are feeling a 3.3% grade, which is a lot higher. If you were counting on trains able to make a 2.0% grade, you may find they don't successfully get up the helix without more power because the engines are having to pull that train as if it was really 3.3%.
 
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Logger Mike said:
If you are a MR Video Plus subscriber, David Popp just had a great video on laying out Helix cuts for their Canadian Canyon Layout Series. Very little waste...lots of pieces.
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If you aren't a subscriber, is there a diagram for a minimal waste way of cutting out helix parts from a 4x8 sheet?
 


riogrande said:
If you aren't a subscriber, is there a diagram for a minimal waste way of cutting out helix parts from a 4x8 sheet?
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There wasn't/isn't a template per se, as I'm sure each Helix has its own idiosyncrasies , I merely pointed this out, as he went thru the steps for creating his "templates", then the process of laying out on the sheets. Albeit, it was for an N Scale Helix, but I'd imagine the steps would be the same.


Sent from my iPad using Tapatalk
 
riogrande said:
Yes, 22" radius is not a good idea. There is a thing called grade equivalent where the curvature of a helix causes a train to experience a grade significantly higher than the simple rise/run grade. One guy explained it wells as follows:

"The difference between the 4% and 2.5% for a 24" radius is caused by the grade equivalent. Grade equivalent, which was discussed earlier in this tread, is the drag (expressed as a grade) that a train sees from going through a curve. There is actually a complicated formula to figure this out, however there is also an easy rule of thumb for HO. Basically 32/radius of the curve= grade equivalent. So a train going through a LEVEL 24" radius curve will experience a drag equivalent to a 32/24 = 1.33 degree grade. So if a 24" radius helix produces an actual 2.65% grade (~2.5%) then the train will experience an almost 4% grade. The minimum radius I would use for a helix is 30 inches if you have the room."

There is a lengthy discussion at MRH forums that also might be good to read.

http://model-railroad-hobbyist.com/node/28784?page=4

So keeping in mind if you have a 30" radius track helix and want a 2% actual grade, your going to get 3.8" rise for every 360 degree turn. Remember, circumference = 2 x Pi x Radius and Grade = Rise over Run. So even with a 30" radius helix, the train is going to experience a grade, due to drag of the curve will be 2.8% and that's assuming a separation of 3.8 inches between turns allows sufficient clearance when taking into account subroadbed thickness and track etc. I'd allow for a full inch for that, so with a 30" radius curve helix at 2.0% actual grade with 1 inch thickness and 1/16" track - you'll have 2.6 inches over the head of the rails. Is 2.6 inches enough to clear your tallest rolling stock? What about finger space if you need to re-rail cars? Just some factors to figure in on.
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Great explanation. I'm going to read it thru several times as I contemplate the building of my helix for my new layout plan.
Brian

PS: correction made by Riogrande
riogrande said:
Alert Brian. I've gone back and corrected my original post as it had an incorrect grade equivalent. Your quote of my post has a bad number in it.

I had incorrectly given the grade figure as 2.7 effective grade for an actual 2.0% in a 30" radius helix. I multiplied 2.0 x 1.33 when I should have added it. The correct grade equivalent should be 3.3% effective grade on a helix with an actual 2.0% grade. That's quite a difference.
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beiland said:
Great explanation. I'm going to read it thru several times as I contemplate the building of my helix for my new layout plan.
Brian
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Alert Brian. I've gone back and corrected my original post as it had an incorrect grade equivalent. Your quote of my post has a bad number in it.

I had incorrectly given the grade figure as 2.7 effective grade for an actual 2.0% in a 30" radius helix. I multiplied 2.0 x 1.33 when I should have added it. The correct grade equivalent should be 3.3% effective grade on a helix with an actual 2.0% grade. That's quite a difference.

I had a nolix on my last layout and running trains up my 2.9% grade was not a major problem but it did require sufficient power and if a train became uncoupled on the grade, the cars would break away and pick up speed rolling down the hill. That's something to consider when making a helix too.

Unfortunately helixes are great space eaters, especially if constructed to minimize grade and ability to haul long trains with long cars up and down.
 
I would use Hardboard or Masonite, 1/8th inch thick. It would need to be well supported so it won't sag over time. With a thinner helix base, the grade can be lowered to it's minimum. Or, every turn of the helix can be lowered by 1/8th inch with the 1/8th inch Masonite over 1/4th inch plywood.

Also, if you haven't picked up that cutting full circles from your sheet materials is very wasteful, if the segments where made from 1/4 circles with a 30 inch radius for the outside track (the up track) many 60 inch radius circles can be made from a 4X8 sheet of material. Keep the 1/4 circles to one side of the sheet and it's possible some 1/4 circles could be cut from the other side. It is a simple matter of making a scale drawing of a 4X8 sheet and seeing how many segments can be cut from it.
 
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Helix's don't necessarily have to be a circle. I plan mine to be an oval 60" x 96", whenever I build it. That extra 72" of straight track (36" on each side), will allow a lesser grade through the curved part, as well as more clearance for fingers between levels. It is a space hog, but I plan to add a room outside the layout room on the porch of my train shed, similar to what Brian is doing on his building.

Willie
 
Here are some interesting comments by Joe Fugate on helixes:

Yep, do not overlook curve drag and the additional "grade equivalent" drag it will create. You're typically looking at a ~4% grade equivalent on a 24" radius helix. In my case, the largest visible grade on the layout is 2.65% and my 24" radius helix was 2.65% as well. I figured if I powered the train to make it up the visible 2.65% grade, then the 24" helix grade would be no problem.

Wrong! The trains consistently stalled on the 24" helix because the curve drag/grade equivalent was almost 4%. My operating crews HATED the helix and pleaded with me to replace it with something better. I finally relocated the helix into the shop area where I could expand it to a 40" radius and a 1.5% grade, making the total curve drag/grade equivalent just over 2%. The new helix worked wonderfully and the op crews were greatly relieved.

Morale of the story is this: do not put the steepest grade on your railroad in hidden trackage such as a helix or you're likely to regret it. On a helix where the entire train is in a curve, curve drag/grade equivalence MUST be accounted for so that the total drag on the train is no more than you have on a visible grade. Ideally, make hidden trackage a bit less than visible trackage.

In other words, your smallest radius, your steepest grade, your longest curve SHOULD NOT be hidden trackage. Stressing your operating limits more in hidden trackage is a bad idea since the trains are harder to access if there's an issue -- and issues are likely if you compromise your visible track standards because the track is hidden. You might get lucky, but what if you don't? You open to ripping out hidden trackage that fails to perform well?

Better is to keep the tightest compromises in your trackwork in visible trackage
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