the MRH Forum

Radius Getting started
Reply
Frequent poster 568 posts redP Frequent poster 568 posts
redP

A couple questions. 1. What is the minimum radius for a helix in HO scale?

2. Would a broader radius reduce drag?

 Modeling Penn Central and early Amtrak in the summer of 1972

 
Reply 0
blindog10 Prolific poster 3,329 posts
blindog10

ask JoeF...

....What his operators thought of his small helix. The answer is probably 50% bigger than you want to hear, unless you're running Shays pulling short log trains. And as for drag, check out the recent thread about grade compensation. The short answer is Yes. Scott Chatfield
Reply 0
Neal M Frequent poster 574 posts
Neal M

My Helix...

Is a two track helix. Inside radius 29.75 outside radius 32.00. It has a 2% grade with a height of 12" This was the biggest I could have due to space restrictions. I'm sure a wider helix with a lesser degree of grade would be better. I've run 2 diesel engines, both 4 and 6 axle engines and anywhere from 20-28 cars with no issue. However, with my 89' auto racks, I usually have 2 6 axle engines with 12 auto racks. I don't see any type of drag or issue running them up the helix.

Hope this helps.

Neal
Reply 0
Prof_Klyzlr Moderator 7,961 posts
Prof_Klyzlr

Search says...

Dear ?? (RedP),

Plugging "Helix radius" into the Search box at top right of this screen gives a wealth of relevant info and experiences, which should answer your questions. Suggest checking out:

https://forum.mrhmag.com/magazine-feedback-was-ezines-891776 helix

​ https://forum.mrhmag.com/post/smallest-radius-helix-12191643 

http://model-railroad-hobbyist.com/node/20316

http://model-railroad-hobbyist.com/node/28784

http://model-railroad-hobbyist.com/node/24604

http://model-railroad-hobbyist.com/node/4076

http://model-railroad-hobbyist.com/node/21952

http://model-railroad-hobbyist.com/node/31569

http://model-railroad-hobbyist.com/node/18570

http://model-railroad-hobbyist.com/node/9986

http://model-railroad-hobbyist.com/node/28284

Hope this helps...

Happy Modelling,
Aim to Improve,
Prof Klyzlr
Reply 0
railandsail Prolific poster 8,846 posts
railandsail

Interference Question

Quote:

Neal M

Mine is a two track helix. Inside radius 29.75 outside radius 32.00. It has a 2% grade with a height of 12" This was the biggest I could have due to space restrictions. I'm sure a wider helix with a lesser degree of grade would be better. I've run 2 diesel engines, both 4 and 6 axle engines and anywhere from 20-28 cars with no issue. However, with my 89' auto racks, I usually have 2 6 axle engines with 12 auto racks. I don't see any type of drag or issue running them up the helix.

I'm assuming those radius quotes are dimensions to the center of the tracks?

So on your double track helix you have 2 1/4" between the tracks.
1) Can you run your long auto racks up the outer track while running another train passing it on the inner track?
2) What sort of minimum clearance do you find necessary for those auto racks to clear any fixed obstacles (structures) outboard  of the outboard radius.
 

I am planning a double track helix in as big of a diameter helix as possible, but I am limited to probably a 31" outer radius. I also want to run those long auto racks and long passenger cars (and sometimes possible a passing situation on the helix). So my concerns are, the clearances needed for the ends of those cars around the outer helix structure components,....and the minimum distance I might allow between the inner and outer helix tacks to allow for those 'inadvertent' passing situations.

 

 

Brian

1) First Ideas: Help Designing Dbl-Deck Plan in Dedicated Shed
2) Next Idea: Another Interesting Trackplan to Consider
3) Final Plan: Trans-Continental Connector
Reply 0
Reply