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MgMechanical
07-06-2009, 02:22 PM
မဂၤလာပါခမ်ာ!!!!
Mechanical engineers အားလံုး ကို ကၽြန္ေတာိႏုတ္ဆက္ပါတယ္ခမ်ာ။ ။ကၽြန္ေတာ္က BE က student တေယာက္ပါ။
mechanical ေတြအားလံုး efficiency & Losses ကိုရင္းနွီးၾကမယ္ထင္ပါတယ္။ကၽြန္ေတာ္တို႕ အဲဒါနဲ႕ပတ္သက္ျပီး ေဆြးေႏြးၾကရေအာင္။ ။ ;D ;D ;D

Efficiency ဆိုတာ output/input ေပါ့ ။efficiency ဟာ 100 percent ေတာ့ မရွိႏိုင္ပါ။ဘာ့ေၾကာင့္လဲဆိုေတာ့ mechanical components ေတြနဲ႕ mechanisms ေတြမွာ losses ေတြရွိလို႕ပါ။ losses=1-efficiency ေပါ့။ဥပမာ IC engine ေတြမွာဆိုရင္ friction losses,heat losses စတာေတြ ရွိပါတယ္။ဒါေတြနဲႏိုင္သမွ်နဲေအာင္ ကၽြန္ေတာ္တို႕ကၾကိုးစားရပါမယ္။အဲဒီ losses နဲျပီး efficiency ေကာင္း မဲ့ methods ေတြ ,principles သိရင္ေဝငွဖို႕ေတာင္းပန္ပါတယ္ခင္မ်ာ။ ။
ေနာက္ျပီး power drives ေတြထဲက gear,chain,belt drive ေတြအျပင္ တျခား ဘာေတြရွိေသးလဲ သိခ်င္ပါတယ္ခင္မ်ာ။ ။ ;D ;D ;D ;D ;D ;D ;D ;D
http://static.howstuffworks.com/gif/gear-bevel2.jpgေအာင္သူ၇ :P :P :P :P :P :P :P :P

နတၳိ
07-07-2009, 10:29 AM
ကိုေအာင္သူ၇
က်ေနာ္သိတာတစ္ခုေတာ့ရွိတယ္ဗ်
power drive ေတြမွာကတစ္ခ်ိဴ. mechanisim ေတြမွာအစ္ကိုေျပာသလိုပါပဲ
gear,chain ,belt ေတြအျပင္ shaft ေတြကိုပါသံုးတာေတြ.ရတယ္ဗ်
အထူးသျဖင္.vertical passageway ေတြမွာအသံုးမ်ားပါတယ္
industry ေတြမွာအသံုးမ်ားတာပါ
ဆက္လက္ေဆြးေႏြးပါဦးခင္ဗ်
ေနာက္လူေတြအတြက္ေလ့လာစရာေလးေတြေပါ့ဗ်ာ
က်ေနာ္တို.ေတြလည္းဗဟုသုတရပါတယ္

cy
07-07-2009, 03:27 PM
roller drives ေတြရွိပါေသးတယ္ ...
ကို နတၳိ ေျပာသလိုပဲ shaft နဲ. ေမာင္းတာ ..

Roller Drives
The concept of roller drives is pretty easy. A smaller shaft is pressed against a larger disk and as the shaft is turned the disk rotates. The reduction is the ratio of the diameters of the shaft and disk. If the shaft/disk pair is pressed together very hard and the correct materials are chosen for them they won't slip as they rotate. If one cascades two or three of these shaft/disk sets a reasonable gear reduction can be had:

Now everything we said above about worm gear precision above applies to these shaft/disk sets. They must me made concentric, smooth and round. If any of these three things is not precise then the rotational rate of the RA axle will vary.
If the manufacturing precision of these shaft/disk sets must be the same as worm gear sets what's the big deal? The answer is that it is very much easier to fabricate a round disk and shaft to high precision than it is to make a precision worm gear set. Almost any modern machine shop can fabricate a shaft/disk set to the required precision where as there are very few shops that can fabricate a precise worm gear set.

နတၳိ
07-08-2009, 09:01 PM
လုပ္ၾကပါ
ဆက္ျပီးေတာ့ေဆြးေႏြးၾကတာေပါ့
က်ေနာ္တို.mechanical ေတြညိမ္ေနၾကတယ္ေနာ္
သူမ်ားေမဂ်ာေတြေဆြးေႏြးခ်က္ေတြအျမဲ update ျဖစ္ေနတယ္ဗ်ာ။

MgMechanical
07-10-2009, 11:48 AM
Chains versus belts

Drive chains are similar to drive belts in many ways, and which device is used is subject to several design tradeoffs. Drive chains are most often made of metal, while belts are often rubber, plastic, or other substances. This makes drive chains heavier, so more of the work put into the system goes into moving a chain versus moving a belt.[citation needed] On the other hand, well-made chains are often stronger than belts. Also, drive belts can often slip (unless they have teeth) which means that the output side may not rotate at a precise speed, and some work gets lost to the friction of the belt against its rollers.

Teeth on toothed drive belts generally wear faster than links on chains, but wear on rubber or plastic belts and their teeth is often easier to observe; you can often tell a belt is wearing out and about to break more easily than a chain. Chains often last longer.

Chains are often narrower than belts, and this can make it easier to shift them to larger or smaller gears in order to vary the gear ratio. Multi-speed bicycles with derailleurs make use of this. Also, the more positive meshing of a chain can make it easier to build gears that can increase or shrink in diameter, again altering the gear ratio.

Both can be used to move objects by attaching pockets, buckets, or frames to them; chains are often used to move things vertically by holding them in frames, as in industrial toasters, while belts are good at moving things horizontally in the form of conveyor belts. It is not unusual for the systems to be used in combination; for example the rollers that drive conveyor belts are themselves often driven by drive chains.

http://wpcontent.answers.com/wikipedia/commons/0/03/Chain.gif

cy
10-06-2009, 10:38 PM
efficiency အေၾကာင္းေတြနဲ. ပတ္သတ္ျပီးေတာ့ ဆက္ေျပာခ်င္တာေလးေတြကေတာ့ production အေၾကာင္းနဲ. Equipment Efficiency ပါ ။
ကုန္ထုတ္လုပ္မႈလုပ္ငန္း မွာ man power နဲ. material ကိုေပါင္းျပီးတြက္ပါတယ္ ။ အဲ့ဒီမွာ Time Efficiency ဆိုတာရွိပါတယ္ ။
1 – (Downtime / Uptime ) = Efficiency %
Downtime time is the key ဘာေၾကာင့္ စက္ရပ္ထားရသလဲ ဆိုတာ ေပၚမွာမူတည္္ပါတယ္ ။ production data ေတြထဲမွာ Downtime
ကိုလဲအဓိကထားပီး မွတ္ရပါတယ္ ။ ဒါမွ maintenance plan ကိုလုပ္နိင္မွာပါ ။ production မွာရွိတဲ့ loss အခ်ိဳ.ကေတာ့
Breakdowns(စက္ပ်က္ျခင္း) adjustment, Small stops and speed loss and human error ,Rejects product , quality inspection ။ ေျပာရရင္ ေနာက္ထပ္ Downtime ျဖစ္ေစတဲ့ loss ေတြရွိမွာပါ ။

ဆက္ျပီးေတာ့ေဆြးေႏြးၾကတာေပါ့ဗ်ာ

aungkyawlin
04-18-2010, 10:16 AM
fight.gif fight.gif fight.gif
i want to study about thermodynamic.
bec this process is important for mechincal.so ok
polytropic process is how to produce efficiency n losses?
thaz u :?

Nay Win
06-21-2010, 06:12 PM
Roller Bearing efficiency is 98%.
Total Efff = power( 0.98)no. of roller bearing.

Gear eff is also 96 to 98%
Total Efff = power( 0.98)no. of Gear Stagees

Regards
Nay Win

ေအ၇ာ
06-21-2010, 10:05 PM
Mechanical engineers အားလံုး ကို ကၽြန္ေတာိႏုတ္ဆက္ပါတယ္ခမ်ာ။ ။ကၽြန္ေတာ္က BE က student တေယာက္ပါ။
mechanical ေတြအားလံုး efficiency & Losses ကိုရင္းနွီးၾကမယ္ထင္ပါတယ္။
[color=black]Efficiency ဆိုတာ output/input ေပါ့ ။efficiency ဟာ 100 percent ေတာ့ မရွိႏိုင္ပါ။ဘာ့ေၾကာင့္လဲဆိုေတာ့ mechanical components ေတြနဲ႕ mechanisms ေတြမွာ losses ေတြရွိလို႕ပါ။ losses=1-efficiency ေပါ့။


ကိုေအာင္သူရေရ
Efficiency ဆိုတာ Power Efficiency ကိုဆိုလိုတာေပါ့ေနာ္ ေအ၇ာတို႕လည္း အင္/ယာ မဟုတ္ေပမယ့္ Efficiency ဆိုတာကို စြမ္းရည္ ဆိုၿပီးၾကားဖူးတယ္ရွင့္၊
စက္ပစၥည္းတစ္ခုကိုေပးသြင္းရတဲ႔ Input Power ႏွင့္ ယင္းစက္က ျပန္လည္ထုတ္ေပးႏိုင္တဲ့ Output Power ဆက္စပ္မႈကို ေဖၚျပႏိုင္တယ္လို႔လည္းသိရပါတယ္။
အမွန္မွာေတာ့ ပါ၀ါေပးသြင္းသေလာက္ျပန္ထြက္တာပါပဲ၊ စက္တည္ေဆာက္သူေတြလိုခ်င္တဲ့ အက်ဳိးျပဳအသံုး၀င္တဲ့ ပါ၀ါနဲ႕ သူတို႕မလိုလားတဲ့ ဆံုးရံႈးမႈပါ၀ါရယ္လို႔ကဲြျပားေနလို႔သာပါေနာ္။

ဒီေတာ့ စုစုေပါင္းေပးသြင္းပါ၀ါ = ထုတ္ယူသံုးစဲြႏိုင္ေသာ ပါ၀ါ + ေလလြင့္ဆံုးရံႈးေသာ ပါ၀ါရယ္လို႕ ညီမွ်ျခင္းရယူႏိုင္ပါတယ္။

ဆံုးရံႈးမႈကေတာ့ ပြတ္တိုက္မႈအားေၾကာင့္အပူျဖစ္ကုန္တာျမင္လြယ္တတ္ပါတယ္၊ ဒီ႕အျပင္လည္းရွိပါေသးတယ္။
အဲဒီေတာ့ ထုတ္သံုးႏိုင္တဲ့ပါ၀ါဟာ ေပးသြင္းတာထက္ အၿမဲငယ္ေနမွာ ဟုတ္ပါတယ္ရွင္။

စြမ္းရည္ဆိုရာမွာလည္း ေပးရသေလာက္ရဲ႕ ဘယ္ေရြ႕ဘယ္မွ်ျပန္ရသလဲ သိခ်င္တာဆိုေတာ့ အ၀င္ႏွင့္အထြက္ကို ႏိႈင္းယွဥ္ခ်ိန္ထိုး အခ်ဳိးခ်ၾကည့္ၾကတာပဲျဖစ္ပါတယ္။
သခ်ၤာသမားေတြကေတာ့ စြမ္းရည္ရာခိုင္ႏႈန္း ဆိုတာကိုအသံုးျပဳၿပီး စက္တစ္ခုျခင္းရဲ႕ ပါ၀ါေတြေျပာင္းလဲေပးႏိုင္တဲ့အရည္အေသြးကိုေဖၚျပေလ့ရွိၾကပါတယ္၊
စြမ္းရည္ရာႏႈန္းရွာေဖြဖို႕ အထြက္ပါ၀ါကိုတည္ကာ ေပးသြင္းခဲ့ရတဲ့ပါ၀ါႏွင့္စားၿပီး ၁၀၀ ႏွင့္ေျမွာက္ေလ့ရွိၾကပါတယ္။
စြမ္းရည္အေၾကာင္းေျပာလွ်င္ ရာႏႈန္းျဖင့္တဲြဖက္ေျပာေလ့ရွိတာမ်ားပါတယ္။

" losses=1-efficiency ေပါ့။" လို႔ ေဆြးေႏြးထားတာက မမွားေပမယ့္ နားလည္မႈရႈတ္ေထြးႏိုင္ေစပါတယ္ရွင္။

ေလးစားစြာျဖင့္
ေအ၇ာေမ

samsoon
06-26-2010, 11:11 AM
Hi..All,

It's a good topic and article. Pls continue.

Thanks