Gradients

Help with designing your track work
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Milzee
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Gradients

#1

Post by Milzee » Fri Jan 03, 2020 6:01 pm

I'm trying to fit a 50mm elevation into a siding on small Z gauge loop. I don't have the runs for a 2% gradient and the layout doesn't have the space for a helix. To complicate things the gradient will have to start in what is part of the main loop which is supposed to be at ground level. So I will have one incline of 0-25mm on the main loop and then after the point for the siding, I will have a two level embankment with a second incline 25-50mm on the siding and a decline of 25-0mm back to ground level on the main loop. If that makes sense. So all of my gradients will be between 4-5%:

main loop: 0-25mm with a 590mm run = 4.2%
siding: 25-50mm with a 525mm run = 4.8%
main loop: 25-0mm with a 485mm run = 5.1%

Questions I have are:

1. Are these gradients too much?
2. There is a point in the middle of the gradient. Are points normally level or can they be inclined on the gradient?
3. With a 4-5% gradient and segmented track how do you "blend" the transition from gradient to level ground?
4. There is a bridge at the end of the siding gradient. Could the bridge have a gradient? That would increase the run for the siding.

Track plan with gradient start and end points attached.
Image

brian1951
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Re: Gradients

#2

Post by brian1951 » Fri Jan 03, 2020 7:41 pm

Simple answer to your question is yes 4% to 5% is to much, and if its on a curve even more so.

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yelrow
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Re: Gradients

#3

Post by yelrow » Fri Jan 03, 2020 8:37 pm

Milzee, 2%, is really the maximum achievable. Sensibly, Hence the use of a helix. Makes life much simpler.

Milzee
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Re: Gradients

#4

Post by Milzee » Sat Jan 04, 2020 10:45 am

Is the 2% preference for realism or for traction? I've set up my tabletop layout with a 5 % gradient and the train climbs it fine. Bear in mind this is Z guage and the rolling stock is feather weight. A matter of grams per car.

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Steve M
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Re: Gradients

#5

Post by Steve M » Sat Jan 04, 2020 11:06 am

It’s a mixture of both. Traction is determined by friction which in turn is determined by both weight and gradient. Remember also that a gradient on a curve will increase drag and reduce the effectiveness of the setup.

And whilst a loco may well climb a steeper gradient than it would in the real world it may well end up looking unrealistic.
Deja Moo: The feeling that you've heard this bull before. ;)

MorganSen
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Re: Gradients

#6

Post by MorganSen » Thu Jan 09, 2020 9:26 am

Ah, the laws of physics are once again party poopers. haha

Chris
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Re: Gradients

#7

Post by Chris » Fri Jan 10, 2020 12:52 pm

Yes it is too steep but it works so is it really???

This is complicated by the fact that it also happens on the main line, if the gradient was only on the siding then you could compromise,
I built a steep gradient on a branch line but it only had space for 2 car DMU at the top so the fact an intercity wouldn't go up didn't really matter as it had no where to go but if it had been on the main line I could have only run 2 car trains about.

Could you move the point closer to the tunnel mouth and then have only the siding going up, and 50mm seems like a long way to go given it doesn't need to get clearance over another track or anything so could you reduce the height that way?

Chuffchuff
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Re: Gradients

#8

Post by Chuffchuff » Fri Jan 10, 2020 6:04 pm

It’s probably not what you want to read ! But I was keen on getting some incline on a 12 x 12 ft OO layout.

Apart from gradient problems, trying to fit in decent curve radius for a up and down line, and access from only the middle of the layout. I opted for a separate higher level track, with a lower track under.

The layout may not have the incline interest, but I hope that the tracks will allow me to run a number of trains at the same time using cab control.

Rgds

Milzee
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Re: Gradients

#9

Post by Milzee » Fri Jan 10, 2020 8:05 pm

Thanks for the feedback. I think I'll set up the gradients as a dry run once the baseboard is done and post some pics. 50mm is 11m or 36ft to Z scale so not much since its supposed to be up a mountain.

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