# Ground clearance?



## DKRickman (Mar 25, 2008)

This one has me stumped for the moment, and my design/modelling can't continue until it's solved... 

What would be an apropriate clearance height for the lowest part of a US narrow gauge 1860-1880 era steam locomotive? In particular, how close should the bottom of the pilot be to the rails? 

Now, I know that current US practice requires that no part of a locomotive may extend closer than 6" to the rail head. When I drew that on my diminutive little teakettle, however, it seemd way to high. I looked through some locomotive drawings, and found a standard gauge Mason 4-4-0 of around 1860, which shows the pilot being about 2" above the rails. That seems awfully low, but maybe that's just my engineer training finding a reason to bad-order something. /DesktopModules/NTForums/themes/mls/emoticons/hehe.gif 

Is/was there any kind of standard? Is there any agreed upon dimension for those of us in the large scale community which has been shown to work well & look good? What say the masses?


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## DKRickman (Mar 25, 2008)

Sorry for responding to my own question, but I've found a number of standard gauge engines from the era in question, and pilot heights seem to vary anywhere from 2" to 6", with most being on the lower end of the range. I think for my engine I'll use 2", (2.5 mm) unless anyone has any suggestions or opinions to the contrary.


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## toddalin (Jan 4, 2008)

While it looks good, prototypical pilot height may not be desirable in a garden setting! 

My GP-9 has lost both the pilot step and snow plow on numerous occasions when it has bottomed out at "less than stellar" track joints. I've actually raised both of these slightly just because of this. 

I've personally seen the big Big Boy and the big Accucraft brass engines' pilots also bottom out. Only thing is when they do it, the brass shorts out the rails shutting down the power pack, at least momentarily. 

Like rail height, wheel flanges, etc., some things, when scaled out properly, don't provide the best real world service in the garden setting.


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## DKRickman (Mar 25, 2008)

Good point, and thanks for your comments. Do you happen to know how high the various components you mentioned are? 6" in 1:29 works out to just over 5mm, just under in 1:32. In either case, that's roughly twice the height I was considering. 

Would I be a fool to assume that I'll just make sure my track is good? I've been accused of being a perfectionist, and I definitely believe in keeping track as close to perfect as possible, but I also know that the real world is far from perfect. How hard is it to keep outdoor track in tip-top shape? 

For the record, I have absolutely no track at the moment, so the model, when finished, will have to be a shelf queen for the time being. Eventually, though...


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## toddalin (Jan 4, 2008)

Posted By DKRickman on 08/04/2008 4:35 PM 
Good point, and thanks for your comments. Do you happen to know how high the various components you mentioned are? 6" in 1:29 works out to just over 5mm, just under in 1:32. In either case, that's roughly twice the height I was considering. 
Would I be a fool to assume that I'll just make sure my track is good? I've been accused of being a perfectionist, and I definitely believe in keeping track as close to perfect as possible, but I also know that the real world is far from perfect. How hard is it to keep outdoor track in tip-top shape? 
For the record, I have absolutely no track at the moment, so the model, when finished, will have to be a shelf queen for the time being. Eventually, though...

I would love to answer your question but: 
I've already raised this stuff on one of my Geeps and the other doesn't have the steps attached. (Maybe the prior owner had same problem?) 
But if it is any consolation, this is my worst engine for bottoming out, and these are plentyful, so someone here could take this measurement for you. 
You can make your track as perfect as you like, but unless it sits on a solid surface, you will get at least some differential settlement. 
BTW, when I saw the Big Boy bottom out (actually in a couple spots) it was on Roger Clarkson's massive 1/3 acre railroad and his track is all mounted securely on concrete with minimum 20 foot diameter curves, so in some cases, it doesn't take much. And yes, it did shut down his system. 
Enjoy.


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## SlateCreek (Jan 2, 2008)

There's a photo someplace on the old site that someone put up .... I believe it's on the Silverton Northern someplace, but it could be RGS .... the locomotive has a wooden pilot with two big grooves worn in it from the steep upgrades .... 

I think you'll find how high depends on what type engine, what year, and what road ... and modified by conditions it encountered! 

Matthew (OV)


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## Ironton (Jan 2, 2008)

Matthew 

That picture is of the Silverton RR #100 (the Ouray). The grooves are from the sudden changes from one grade to a different grade. That is the vertical curves that appear when you change grade. The Silverton had 5 1/2 percent grades in places. You can find that picture and others at the Denver Public Library site in their western pictures collection


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## East Broad Top (Dec 29, 2007)

Most of my pilots are between 3/16" and 1/4" above the railhead (right around the 5mm mentioned above). That's close enough to "look good," but high enough to where it doesn't get in the way (too much) on the occasional dip. Most of my pilots do, however, have scuff marks where they've scraped the tops of the rails on occasion. 

Later, 

K


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## DKRickman (Mar 25, 2008)

Posted By East Broad Top on 08/05/2008 8:35 AM
Most of my pilots are between 3/16" and 1/4" above the railhead (right around the 5mm mentioned above). That's close enough to "look good," but high enough to where it doesn't get in the way (too much) on the occasional dip. Most of my pilots do, however, have scuff marks where they've scraped the tops of the rails on occasion. 

Later, 
K




Thanks! That's exactly the kind of voice of expereince I'm looking for. It sounds to me like the scuff marks are prototypical enough, though I don't think I'll go so far as cutting grooves over the rails. I've been unable to find that picture emntioned, so if anyone has it saved, or has a link to it, I'd love to see. 

Interestingly, I settled on 5mm last night after fiddling with some ideas. I decided to see what would happen if the lead driver suddenly went from level to a 4% grade with no transition. Any more than that would ause the pilot to rise into the deck anyway, so I'll call that my limit. I found the point at which a 5mm high pilot would hit the rails, then figured out the shape of the pilot from that - it looks good to my eye and has the right proportions, so it seems like that's the ticket. 

I miss the ability to use CAD, but a pencil and paper don't have OS conflicts!


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## Ironton (Jan 2, 2008)

I have a detail of the picture of Silverton #100. This shows the front of the engine and one of the grooves is easily visible. 
The one on the right side of the pilot. The one on the left side is obscured. I will try to attach it here. 












Hope it comes through. Enjoy


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