Journals to Engine Frame Clearance Measurement Questions

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heislerboy
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Journals to Engine Frame Clearance Measurement Questions

Post by heislerboy »

I am building a 2.5” scale 2-8-0 steam engine using Milner C-19 planes and casting. I am having problems with the driver journals going into the engine frame, the engine frame gapping for the journals calls for 2.5” and the journals call for 2.498” were the journals go into the engine frame, that measurement is only 0.002” of clearance . My frames were made to exact measurement to the planes as I am finding out when
I’m getting measurements of were the journals go and other key areas. I had my journals made for me because my machining skills aren’t that experienced for doing that type of machining. When I got the journals back from the machinist that did them for me, I took measurement of where they go into the frame and they are 2.497” – 2.498” that only 0.002” - 0.003” of clearance in between the frame and journal. So I asked my father what is his Railroad Supply CP173 American measurement are for his engine frame measurement is 1.375” and the journal measurement to go into the engine frame is 1.370” that clearance is only 0.005” in between the engine frame and the journal. When I try to put my journals into my frame it is a bear to get them to go into the frame even with oil, it almost feels like a tight hand press fit, and I know that the journals need to fit loosely into the frame to allow the journal to move up and down in the frame while the engine is running along the tracks. My fathers American has no issues moving up and down at the measurements that are in his planes. I am the fourth owner of this engine project, all I know is that the first owner bought all of the casting and main parts for this engine and even the engine frame, and I am the only owner that has started machining parts on this engine.
I am asking what should be the clearance for the journals to move up and down in the frame that is not to tight?

Andrew S.
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Bill Shields
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Re: Journals to Engine Frame Clearance Measurement Questions

Post by Bill Shields »

Things have to fit and slide and handle rough track.

Keep in mind that when running forward the axle boxes will be pushing on the frame..so the actual clearances are not that critical as long as:

The clearances are the same for all boxes and:

Axles are square to the frame when pushing -> moving forward as well as when pulling -> moving in reverse.

0.005 is not an unreasonable number. .002 is a little tight for by tastes especially for a loco of that size.
Too many things going on to bother listing them.
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LVRR2095
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Re: Journals to Engine Frame Clearance Measurement Questions

Post by LVRR2095 »

I remember something Carl Purinton once said about full sized locomotives.
He said that steam locomotives run best when they are completely worn out.....but not quite.
Remember you are not making a watch, but a steam locomotive that must be able to run over uneven tracks.

Keith
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Fender
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Re: Journals to Engine Frame Clearance Measurement Questions

Post by Fender »

Do the pedestal openings in the frame have sharp corners? They should be rounded slightly. Also, what is the clearance between the flanges on the driving boxes and the flat side of the frames?
Dan Watson
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cbrew
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Re: Journals to Engine Frame Clearance Measurement Questions

Post by cbrew »

imho, .002 to .003 is way to tight. I set my main axle to .005 and the next axle out each direction .007 and third axle .008
as Bill stated these little critters need to be able to move rock and roll on the rough track.
watch for burs and sharp corners. just taking a file and breaking the edge will help alot
If it is not live steam. its not worth it.
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