So I am helping A friend build his layout, and his plans call for a 22 inch helix with a 3 percent grade. I know it's been done and I know everyong is going to scream it can't be, but, if the train is limited to a 4 axle diesel and 9 or ten cars plus caboose, I can't see any real issue. Am I missing something?
JJF
Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing.
Yesterday is History.
Tomorrow is a Mystery.
But today is a Gift, that is why it is called the Present.
Yes.
Separation between ramps.
If the helix is made with thin enough material - and no dome cars, or double stacks. 3% grade gets wyou a little over 4" between levels but you have to subtrack out the thickness of whatever the helix is built on. And not use cork or other roadbed.
I've seen the video. I've seen it run. I still don't believe it is long term reliable.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
He’s going to need some diesels with a lot of traction! A regular 4 axle diesel has a tough time on my 3½% 32” helix pulling 12 cars. My super weight 6 axle diesels (2 lbs, 8 oz drawbar) do very nicely but the 4 axle locos slip. The grade plus the 22” radius is going to put a pretty good load on the loco. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
My layout models a fallen flag short line that rarely runs trains longer than about 10 NMRA weighted cars (none longer than 50' and most 40' or less). This double-decked layout has a 22" radius helix at each end of the layout. These helix structures were designed and built to provide 18" of lift with a 2.62% grade. Most of my Blue Box diesels are just capable of hauling 8 to 10 car trains up these grades but do better with two locos pulling. Some of my smaller steamers can only pull a couple of 50' passenger cars up these helix grades. My experience would indicate that a 22" helix can be done, but if I were to do it again, I would reduce the height between helix loops to the absolute minimum and add another loop to further reduce the grade. I don't think you'd be happy with a 22" radius helix using a 3% grade. Unless you run very short trains, a 22" radius with a 3% grade is bound to cause a lot of slipping.
Make your helix loop decks as thin as possible. Mine consist of two layers of 3/16" plywood laminated together (3/8" total) with the joints staggered at least 6 inches apart. Attach your track directly to the loop decks without roadbed. Finally, use the minimum possible height between loops as you can. No, you don't need clearance for fingers above the train cars as helix derailments are more efficiently dealt with from the ends of the cars.
Hornblower
JDawg So I am helping A friend build his layout, and his plans call for a 22 inch helix with a 3 percent grade. I know it's been done and I know everyong is going to scream it can't be, but, if the train is limited to a 4 axle diesel and 9 or ten cars plus caboose, I can't see any real issue. Am I missing something?
I have a program for helix design, if you give me the amount of rise I’ll post the printout. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Hornblower - what did you make the helix out of? That grade on a 22" radius is only 3.6" rise per loop. It's a double whammy using a smaller radius - if the grade isn't sttep enough, there's not enough clerance. A much larger helix can have a much less steep grade yet still get more rise per loop.
The helix on my friends N Scale NORFOLK SOUTHERN layout is Kato Unitrack on flat fiberglass. This was as thin as we could make it.
Twenty years with no problems.
-Kevin
Living the dream.
To the OP. Go to YouTube and search on Helix Smackdown. That should be informative.
Rio Grande. The Action Road - Focus 1977-1983
JDawg, your comensated grade, which takes into account the grade plus the additional drag of the curve, will be about 4.3%. You'll likely need some Bullfrog Snot on one set of wheels on the loco.
Good luck!
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
rrinkerHornblower - what did you make the helix out of?
Randy
Since I wanted to host operating sessions on my layout, I designed it with wide aisles so people can comfortably pass and work around each other without banging into one another or the layout. The wide aisles meant limited space for the two helix structures so I was stuck with a 22" radius. Your calculations are spot on and each loop gains 3.6" of elevation. I built each helix using 3/16" plywood that the big box stores sell as underlayment for sheet vinyl flooring. Each loop consists of two layers of 3/16" plywood arcs laminated together (3/8" total) with the joints staggered at least 6 inches apart. Once the grade of the lower approach and bottom loop was set using wood risers, I used the "fixed dimension riser block" method to complete the remaining loops of the helix. The riser blocks are located every 45 degrees around the helix so I haven't had any problems with the 3/8" thick loops sagging or warping. I used glue and an 18 gauge brad nailer to assemble the structure. Once the glue cured, the helix became rock solid.
I like to run my diesels as two-unit consists so the diesels have no problem hauling 10 to 14 car trains up a helix at around 5 scale miles per hour with no slipping, stalling or even hesitation. I run my steamers individually but also make them pull shorter trains. I have found that some of the steamers will slip pretty badly when backing a full train off the one helix into Newport Yard. However, I find that this problem can be dealt with by doubling the train for this maneuver. This adds a little fun and challenge to the operating scheme as well. If I find my operating crews complaining over this situation, I could always apply some Bullfrog Snot!