stay rods material?

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ChooChooChris
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stay rods material?

Post by ChooChooChris »

The material for the stay rods on my LE 040 boiler are pretty much the only part that do not have a astm code listed.

I think https://www.mcmaster.com/8920K135-8920K519/ is what I would be looking for at 3/8 inch it is a 1018 steel with a yield of 54,000 psi (this number feels low to me considering everything else is rated at 70k+)and an ASTM A108 rating. Can anyone verify that this would be the ideal material?
-Chris Srch---- Home track Tradewinds and Atlantic Railroad
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Bill Shields
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Re: stay rods material?

Post by Bill Shields »

FWIW:

A36 round bar is what I use....

is listed in the 58K range -> not that it will make that much difference.

if your diameter and spacing calculations are OK for 54K, then not to worry

if they are not, then look for something stronger
Too many things going on to bother listing them.
pat1027
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Re: stay rods material?

Post by pat1027 »

Bill Shields wrote: Mon Nov 28, 2022 10:47 am FWIW:
if your diameter and spacing calculations are OK for 54K, then not to worry

if they are not, then look for something stronger
That's the key. My boiler was built with 3/8" 316 stainless stays which show a slightly lower yield strength that your 1018 and maybe similar to Bill's A36. Spacing was calculated on the materials used.
ChooChooChris
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Re: stay rods material?

Post by ChooChooChris »

pat1027 wrote: Mon Nov 28, 2022 12:22 pm
Bill Shields wrote: Mon Nov 28, 2022 10:47 am FWIW:
if your diameter and spacing calculations are OK for 54K, then not to worry

if they are not, then look for something stronger
That's the key. My boiler was built with 3/8" 316 stainless stays which show a slightly lower yield strength that your 1018 and maybe similar to Bill's A36. Spacing was calculated on the materials used.
Following the plans for the LE 0-4-0 boiler so I have not done those calculations myself Just going off of what ever they had listed and going stronger whenever possible (firebox is slightly thicker then called for for example and stays ontop of firebox are thicker as well and thicker bottom on the "mudlegs ") Seems the material I listed exceeds the other material so im guessing it will be fine if i just continue with their spacing.
-Chris Srch---- Home track Tradewinds and Atlantic Railroad
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Bill Shields
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Re: stay rods material?

Post by Bill Shields »

I would calculate anyway.

Once you have built the boiler, it is a little late to say 'oops' the drawing was wrong.

Remakes on boilers can be very expensive
Too many things going on to bother listing them.
ChooChooChris
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Re: stay rods material?

Post by ChooChooChris »

Bill Shields wrote: Mon Nov 28, 2022 12:43 pm I would calculate anyway.

Once you have built the boiler, it is a little late to say 'oops' the drawing was wrong.

Remakes on boilers can be very expensive

Well I guess I should figure out how to do that then lol
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Bill Shields
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Re: stay rods material?

Post by Bill Shields »

think what is the minimum cross sectional area of the rod?
what is the MAXIMUM area of the flat firebox pressure does the rod support?
what is the operating pressure on that area for which the calculation is made?
what is the operating FORCE on the above area?
what is the safety factor?
what is the strength of the chosen material?
what is the strength of the weld?

you only have to do ONE ROD, based on the rod that supports the MAXIMUM surface area -> assuming you are using the same material and diameter in all locations.

trick to make it easy -> assume that the stay bolts carry ALL the pressure, even though the firebox walls carry a good load.
if your stays are then safe based on this calculation, you are good and need to go no further.
Too many things going on to bother listing them.
ChooChooChris
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Re: stay rods material?

Post by ChooChooChris »

So rough math from memory of plans . 6x8 before the metal starts to curve running at 120psi x 8 safety factor = ~46k , 3/8 stay type 1018 would be 21000 lbs Plans call for two of those on each side I could go up to 5/8th instead.
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Bill Shields
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Re: stay rods material?

Post by Bill Shields »

ChooChooChris wrote: Mon Nov 28, 2022 2:50 pm So rough math from memory of plans . 6x8 before the metal starts to curve running at 120psi x 8 safety factor = ~46k , 3/8 stay type 1018 would be 21000 lbs Plans call for two of those on each side I could go up to 5/8th instead.
6x8 - two on each side????

doesn't sound correct -> or I am misinterpreting
Too many things going on to bother listing them.
ChooChooChris
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Re: stay rods material?

Post by ChooChooChris »

Bill Shields wrote: Mon Nov 28, 2022 3:21 pm
ChooChooChris wrote: Mon Nov 28, 2022 2:50 pm So rough math from memory of plans . 6x8 before the metal starts to curve running at 120psi x 8 safety factor = ~46k , 3/8 stay type 1018 would be 21000 lbs Plans call for two of those on each side I could go up to 5/8th instead.
6x8 - two on each side????

doesn't sound correct -> or I am misinterpreting
my bad 4 on each on 2 inch centers. Didnt have it infront of me.
-Chris Srch---- Home track Tradewinds and Atlantic Railroad
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Bill Shields
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Re: stay rods material?

Post by Bill Shields »

ok...better -> so what is the loading -> as designed?
Too many things going on to bother listing them.
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