Steam Engine Reviews/Piston Head Stress - Revision history

Bastelmike at 15:45, 30 August 2011

2011-08-30T15:45:56Z

← Older revision		Revision as of 15:45, 30 August 2011
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	The following review is provided by ~~Mike Bastel.~~		The following review is provided by Bastelmike

	Stress Calculations<br>		Stress Calculations<br>
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	Piston bolt<br>		Piston bolt<br>

	calculation in metric for bending piston force: F = A * p<br>		calculation in metric for bending
			piston force: F = A * p<br>
	A = 3,75” * 3,75” * 0,785 = 11,04 sq.inch = 71,2 cm² = 7120 mm²<br>		A = 3,75” * 3,75” * 0,785 = 11,04 sq.inch = 71,2 cm² = 7120 mm²<br>
	p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm² <br>		p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm² <br>

Mjn at 12:15, 19 August 2011

2011-08-19T12:15:01Z

← Older revision		Revision as of 12:15, 19 August 2011
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	tolerable pressure for sliding surfaces, mild steel on steel: none. high rate of wear !!!<br>		tolerable pressure for sliding surfaces, mild steel on steel: none. high rate of wear !!!<br>
	tolerable pressure for sliding surfaces, steel on bronze: 25 N/mm²		tolerable pressure for sliding surfaces, steel on bronze: 25 N/mm²

			Both the stress through bending and the area pressure seem to be much over tolerable values.

Mjn at 12:14, 19 August 2011

2011-08-19T12:14:27Z

← Older revision		Revision as of 12:14, 19 August 2011
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	b2 : 1 (diameter below 10 mm)<br>		b2 : 1 (diameter below 10 mm)<br>
	βk : 1,3 for St37-2; 1,4 for 30CrNiMo8<br>		βk : 1,3 for St37-2; 1,4 for 30CrNiMo8<br>
	ν : 1,5 average value<br>		ν : 1,5 average value<br>
	σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8		σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8

Mjn at 12:14, 19 August 2011

2011-08-19T12:14:02Z

← Older revision		Revision as of 12:14, 19 August 2011
Line 1:		Line 1:
	The following review is provided by Mike Bastel.		The following review is provided by Mike Bastel.

	Stress Calculations		Stress Calculations<br>
	OSE Steam engine		OSE Steam engine<br>
	Piston bolt		Piston bolt<br>

	calculation in metric		calculation in metric for bending piston force: F = A * p<br>
	for bending		A = 3,75” * 3,75” * 0,785 = 11,04 sq.inch = 71,2 cm² = 7120 mm²<br>
	piston force: F = A * p		p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm² <br>
	A = 3,75” * 3,75” * 0,785 = 11,04 sq.inch = 71,2 cm² = 7120 mm²
	p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm²

	~~[[Image:slug.gif]]~~ --> F = 7120 mm² * 1,76 N/mm² = 12531 N		--> F = 7120 mm² * 1,76 N/mm² = 12531 N

	assumed loose fit of the bolt in both parts		assumed loose fit of the bolt in both parts

	Mmax = F * (l + 2 * s) / 8 = 12531 N * (0,3” + 2* 0,1”) / 8		Mmax = F * (l + 2 * s) / 8 = 12531 N * (0,3” + 2* 0,1”) / 8 <br>
	= 12531 N * 12,7 mm / 8 = 19893 Nmm		= 12531 N * 12,7 mm / 8 = 19893 Nmm

	σ = M / W = M / 0,1 / d³ = 19893 / 0,1 / 6,35³ = 777 N / mm²		σ = M / W = M / 0,1 / d³ = 19893 / 0,1 / 6,35³ = 777 N / mm²

	for mild steel St 37-2 allowable σ : 330 N/mm² STATIC		for mild steel St 37-2 allowable σ : 330 N/mm² STATIC<br>
	for tempered high grade steel 30 CrNiMo 8 allowable σ: 1440 N / mm² STATIC		for tempered high grade steel 30 CrNiMo 8 allowable σ: 1440 N / mm² STATIC<br>
	only very high grade steel tempered will work, if just calculating static load		only very high grade steel tempered will work, if just calculating static load

	Dynamic calculation		Dynamic calculation<br>
	σzul = σD * b1 * b2 / βk / ν		σzul = σD * b1 * b2 / βk / ν<br>
	b1 : 0,88 for St 37-2 ( fine finished surface Ra 6,3)		b1 : 0,88 for St 37-2 ( fine finished surface Ra 6,3)<br>
	b1 : 0,72 for 30CrNiMo 8		b1 : 0,72 for 30CrNiMo 8 <br>
	b2 : 1 (diameter below 10 mm)		b2 : 1 (diameter below 10 mm)<br>
	βk : 1,3 for St37-2; 1,4 for 30CrNiMo8		βk : 1,3 for St37-2; 1,4 for 30CrNiMo8<br>
	ν : 1,5 average value		ν : 1,5 average value<br>
	σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8		σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8

	~~[[Image:slug.gif]]~~ --> for St37-2: σzul = 131 N/mm²		--> for St37-2: σzul = 131 N/mm²<br>
	~~[[Image:slug.gif]]~~ for 30CrNiMo 8 σzul = 367 N/mm²		--> for 30CrNiMo 8 σzul = 367 N/mm²

	no steel will stand 777N/mm² longtime (fatigue)		no steel will stand 777N/mm² longtime (fatigue)

	Calculating area pressure		Calculating area pressure<br>
	Aproj = d * l = 6,35mm * 7,62mm = 48,4mm² in stem		Aproj = d * l = 6,35mm * 7,62mm = 48,4mm² in stem<br>
	p = 12531N / 48,4mm² = 259 N/mm² in stem fit		p = 12531N / 48,4mm² = 259 N/mm² in stem fit<br>
	Aproj = d * s * 2 = 6,35 mm * 5,04mm = 32mm² rod connector		Aproj = d * s * 2 = 6,35 mm * 5,04mm = 32mm² rod connector<br>
	p = 12531 / 32mm² = 392 N/mm² in fit to rod connector		p = 12531 / 32mm² = 392 N/mm² in fit to rod connector

	tolerable pressure for non-sliding surfaces, mild steel, dynamic load: 75N/mm²		tolerable pressure for non-sliding surfaces, mild steel, dynamic load: 75N/mm²<br>
	tolerable pressure for non-sliding surfaces,high grade steel, dynamic load: 150N/mm²		tolerable pressure for non-sliding surfaces,high grade steel, dynamic load: 150N/mm²

	tolerable pressure for sliding surfaces, mild steel on steel: none. high rate of wear !!!		tolerable pressure for sliding surfaces, mild steel on steel: none. high rate of wear !!!<br>
	tolerable pressure for sliding surfaces, steel on bronze: 25 N/mm²		tolerable pressure for sliding surfaces, steel on bronze: 25 N/mm²

Mjn at 12:10, 19 August 2011

2011-08-19T12:10:06Z

← Older revision		Revision as of 12:10, 19 August 2011
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	p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm²		p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm²

	 F = 7120 mm² * 1,76 N/mm² = 12531 N		[[Image:slug.gif]] --> F = 7120 mm² * 1,76 N/mm² = 12531 N

	assumed loose fit of the bolt in both parts		assumed loose fit of the bolt in both parts
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	σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8		σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8

	 for St37-2: σzul = 131 N/mm²		[[Image:slug.gif]] --> for St37-2: σzul = 131 N/mm²
	for 30CrNiMo 8 σzul = 367 N/mm²		[[Image:slug.gif]] for 30CrNiMo 8 σzul = 367 N/mm²

	no steel will stand 777N/mm² longtime (fatigue)		no steel will stand 777N/mm² longtime (fatigue)

Mjn: Created page with "The following review is provided by Mike Bastel. Stress Calculations OSE Steam engine Piston bolt calculation in metric for bending piston force: F = A * p A = 3,75” * 3,75..."

2011-08-19T12:08:26Z

Created page with "The following review is provided by Mike Bastel. Stress Calculations OSE Steam engine Piston bolt calculation in metric for bending piston force: F = A * p A = 3,75” * 3,75..."

New page

The following review is provided by Mike Bastel.

Stress Calculations
OSE Steam engine
Piston bolt

calculation in metric
for bending
piston force: F = A * p
A = 3,75” * 3,75” * 0,785 = 11,04 sq.inch = 71,2 cm² = 7120 mm²
p = 250 psi = 250 lbs / (25,4 * 25,4) = 0,387 lbs / mm² = 1,76 N / mm²

 F = 7120 mm² * 1,76 N/mm² = 12531 N

assumed loose fit of the bolt in both parts

Mmax = F * (l + 2 * s) / 8 = 12531 N * (0,3” + 2* 0,1”) / 8
= 12531 N * 12,7 mm / 8 = 19893 Nmm

σ = M / W = M / 0,1 / d³ = 19893 / 0,1 / 6,35³ = 777 N / mm²

for mild steel St 37-2 allowable σ : 330 N/mm² STATIC
for tempered high grade steel 30 CrNiMo 8 allowable σ: 1440 N / mm² STATIC
only very high grade steel tempered will work, if just calculating static load

Dynamic calculation
σzul = σD * b1 * b2 / βk / ν
b1 : 0,88 for St 37-2 ( fine finished surface Ra 6,3)
b1 : 0,72 for 30CrNiMo 8
b2 : 1 (diameter below 10 mm)
βk : 1,3 for St37-2; 1,4 for 30CrNiMo8
ν : 1,5 average value
σDSch = 290 N/mm² for St37-2; σDSch = 1070 N/mm² for 30CrNiMo8

 for St37-2: σzul = 131 N/mm²
for 30CrNiMo 8 σzul = 367 N/mm²

no steel will stand 777N/mm² longtime (fatigue)

Calculating area pressure
Aproj = d * l = 6,35mm * 7,62mm = 48,4mm² in stem
p = 12531N / 48,4mm² = 259 N/mm² in stem fit
Aproj = d * s * 2 = 6,35 mm * 5,04mm = 32mm² rod connector
p = 12531 / 32mm² = 392 N/mm² in fit to rod connector

tolerable pressure for non-sliding surfaces, mild steel, dynamic load: 75N/mm²
tolerable pressure for non-sliding surfaces,high grade steel, dynamic load: 150N/mm²

tolerable pressure for sliding surfaces, mild steel on steel: none. high rate of wear !!!
tolerable pressure for sliding surfaces, steel on bronze: 25 N/mm²