Can a block bend sitting on an engine stand?
01-27-2010, 06:35 AM
#46
Race Director
Those who matter, know that you know your stuff and are one of the most knowledgable contributors here on Rennlist. As one Renn old-timer to another, I recommend the following:
This message is hidden because Banshee is on your ignore list.
Jeremy
01-27-2010, 07:40 AM
#47
Instructor
Dont worry, i am thinking about making a new account anyways.
Funny that he mentions the word.."troll".
If anyone hypes up Tifos to what he really is its exactly that...a troll, and everyone likes him for it.
Funny that he mentions the word.."troll".
If anyone hypes up Tifos to what he really is its exactly that...a troll, and everyone likes him for it.
01-27-2010, 08:27 PM
#50
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Summary of Decent Intelligent Arguments so far... IMO... The added weight to the manhole cover is really interesting...
Metal does gradually bend a little if there's a lot of unsupported weight in one place. However, there's obviously a support structure built into these 944 engines, and they are normally only supported by 2 engine mounts in the middle, with extra weight hung off of the front and the back. I wouldn't worry about it being on an engine stand. If there is any deformation, I really doubt it's enough to matter.
If you're going to be concerned about anything bending from unsupported weight, it should probably be the crankshaft when it's not installed in an engine, as it is designed to be supported by the main bearing surfaces, and not by the weights (which aren't going to be even if you lay it on its side). But even with that, it's still somewhat of a topic for debate, with a lot of "a guy I know said" arguments.
If you're going to be concerned about anything bending from unsupported weight, it should probably be the crankshaft when it's not installed in an engine, as it is designed to be supported by the main bearing surfaces, and not by the weights (which aren't going to be even if you lay it on its side). But even with that, it's still somewhat of a topic for debate, with a lot of "a guy I know said" arguments.
can an engine bend enough to cause a problem ? that's for you all to decide. metal is not a solid until it gets extremely cold. until that point it is a semi liquid no different than glass. the **** bends. an engine needs to be on a flat surface. the first time i saw these engine stands, with the engine hanging over, i was like.... you got to be kidding me. best to rest it on a big rubber mat right on the floor when you're not working on it. have that block supported as much as possible.
once the cylider heads are on board the tendency for an engine to change it's shape is greatly reduced.
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once the cylider heads are on board the tendency for an engine to change it's shape is greatly reduced.
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http://en.wikipedia.org/wiki/Yield_(engineering)
Does an engine sitting on a stand bend? Yes. Permanently? No. "Plastic deformation" only occurs in metals if the stress exceeds its yield strength. Pretty unlikely that an engine which is designed for the loads of combustion to last hundreds of thousands of miles would see stresses exceeding yield strength while it's sitting still on an engine stand. I guess you might see yield around the bolts holding it on the stand, but that's not what the OP is asking about.
Does an engine sitting on a stand bend? Yes. Permanently? No. "Plastic deformation" only occurs in metals if the stress exceeds its yield strength. Pretty unlikely that an engine which is designed for the loads of combustion to last hundreds of thousands of miles would see stresses exceeding yield strength while it's sitting still on an engine stand. I guess you might see yield around the bolts holding it on the stand, but that's not what the OP is asking about.
I wouldn't be surprised if it could bend if it hung there for a long time. I know a crankshaft can bend if left leaning against a wall and it gets real hot. The engine is much more rigid when it is complete. I never leave on on a stand if I am not working on it. Better safe than sorry.
Normally I wouldn't believe this. But, years ago as a Bell Lab research scientist I saw a demo at a conference. Someone mounted a manhole cover on an optical table, took some holographic images, then put a DIME on the edge and retook the images. You could see the miniscule effect of the distortion of the weight of the dime on the manhole cover.
not many mechanical engineers on rennlist i guess??
it has nothing to do with strenght, or yield strength.
deformation of a material that is exposed to stress or pressure is called creep.
for example an engine on a stand.
because of the stress and pressure on the material, movements in the material on atomic level (yes there is) tend to happen uneven. this results in deformation.
is it enought for an engine to damnage? i dont have experience with it, and measuring would be extremely hard.
i think the spots where the stand is connected to the engine will deform, after some years for example.
the deformation in the center line bore will be too small to matter.
it has nothing to do with strenght, or yield strength.
deformation of a material that is exposed to stress or pressure is called creep.
for example an engine on a stand.
because of the stress and pressure on the material, movements in the material on atomic level (yes there is) tend to happen uneven. this results in deformation.
is it enought for an engine to damnage? i dont have experience with it, and measuring would be extremely hard.
i think the spots where the stand is connected to the engine will deform, after some years for example.
the deformation in the center line bore will be too small to matter.
As a degreed and employed ME, I dont believe aluminum alloy pressure castings are subject to creep distortion below about 300 deg F. Certainly not at room temperature and certainly not at the low stresses that would be induced by the block's own weight.
And this aspect of materials science/engineering is pretty well known and studied, so auto manufacturers are not going to make engine blocks out of some poor material alloy that is subject to creep at low temps and stresses.
So, call it call it closed minded, but I am still saying this is a non-issue.
And this aspect of materials science/engineering is pretty well known and studied, so auto manufacturers are not going to make engine blocks out of some poor material alloy that is subject to creep at low temps and stresses.
So, call it call it closed minded, but I am still saying this is a non-issue.
I built my spare engine in an egine stand. I then left it in the stand for 2+ years before I installed it. Once installed... I ran perfect.
Guys metal can creep and metal can elasticly deform. Metal creep occurs at high temps. The temp needs to be some 75% of the melting temps at minium. However the actual creep characteristics are very dependant on the alloy, loads, and temps so 75% thing is very rough guess.
Point is temperature of a garage even in the Phoenix heat is too low for creep to be an issue. Plus the only load is the static load. Again not enough load.
The block can elastictly deform. Elasticly means it moves, but when the load is changed it moves back like nothing ever happend. Not I am not certain what might happen if you ran the engine with only the bell housing supports. It might not run right due to elastic deformation. Even so we don't run engines on stands so that is a non issue. The engine will turn over by hand just fine so even then my guess is there is not enough deformation to cause issues.
The real danger is plastic deformation at the bolt holes if you put too much weight on the end the block. For example if your bolts are not tight and you hang off the end you could bend the bolts (if you are lucky) or bend are of the bolt holes. Given the engine is 350-400 lbs adding another 200 off the end is not good, but probably is still ok.
So bottomline is you think it can damage it are not even close to being right.
Guys metal can creep and metal can elasticly deform. Metal creep occurs at high temps. The temp needs to be some 75% of the melting temps at minium. However the actual creep characteristics are very dependant on the alloy, loads, and temps so 75% thing is very rough guess.
Point is temperature of a garage even in the Phoenix heat is too low for creep to be an issue. Plus the only load is the static load. Again not enough load.
The block can elastictly deform. Elasticly means it moves, but when the load is changed it moves back like nothing ever happend. Not I am not certain what might happen if you ran the engine with only the bell housing supports. It might not run right due to elastic deformation. Even so we don't run engines on stands so that is a non issue. The engine will turn over by hand just fine so even then my guess is there is not enough deformation to cause issues.
The real danger is plastic deformation at the bolt holes if you put too much weight on the end the block. For example if your bolts are not tight and you hang off the end you could bend the bolts (if you are lucky) or bend are of the bolt holes. Given the engine is 350-400 lbs adding another 200 off the end is not good, but probably is still ok.
So bottomline is you think it can damage it are not even close to being right.
I never had heard of it before til i got into mechanics more... in 99 I heard of VW L4 motors bending over prolonged time on the engine stand... Understand though it takes time and that it can bend in the 100th and 1000ths of an inch margin but thats enough to mess up the center line bore...
I didnt hear of it again until 2002 when i worked at the viper shop and the boss would make me take them off the stands after disassembly and put the bare blocks on rubber mats on the floor; we would leave the adapter attached but basically the crank and heads were removed... when I asked him why; he said they can bend over time sitting on the stands too long...
I would say though that an older american engine with a cast or forged steel block is less likely to do this but these alloy blocks of today it seems more likely to me that it can...
I didnt hear of it again until 2002 when i worked at the viper shop and the boss would make me take them off the stands after disassembly and put the bare blocks on rubber mats on the floor; we would leave the adapter attached but basically the crank and heads were removed... when I asked him why; he said they can bend over time sitting on the stands too long...
I would say though that an older american engine with a cast or forged steel block is less likely to do this but these alloy blocks of today it seems more likely to me that it can...
01-27-2010, 08:56 PM
#51
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Im in the minority, i have never found it amusing for even ...well except for that one guy that posts from his cellphone. Lol, but other than that, it gets annoying after awhile. Dont even get me started on how discouraged i am from even making a thread if all i could get are flaming bull**** comments, because i really have no one else to ask about my car, so a stupid question is more likely to come from me then anyone else.
You just have to take the flak with the good stuff, fire away on those "stupid questions", and let the screen bits fall where they may.
You're anonymous, so does it really matter anyways?
01-27-2010, 11:24 PM
#52
Nordschleife Master
So... if an N/A block, while fastened to an engine stand, were placed on a tread mill....
would it be possible to turbo it?
More importantly, would a set of wheels I can't find on e-bay any more fit on the early car with late suspension components?
And once said, turboed, N/A engine was re-assembled, which oil should I use in it?
Should I observe any special break in procedures?
would it be possible to turbo it?
More importantly, would a set of wheels I can't find on e-bay any more fit on the early car with late suspension components?
And once said, turboed, N/A engine was re-assembled, which oil should I use in it?
Should I observe any special break in procedures?
01-28-2010, 06:13 AM
#53
Instructor
Quote:
Originally Posted by Banshee
Im in the minority, i have never found it amusing for even ...well except for that one guy that posts from his cellphone. Lol, but other than that, it gets annoying after awhile. Dont even get me started on how discouraged i am from even making a thread if all i could get are flaming bull**** comments, because i really have no one else to ask about my car, so a stupid question is more likely to come from me then anyone else.
I agree with you to some extent, but you have to realize that if every post was a dry, detailed, and carefully argued post, then the entertainment value would sink for a lot of technically savvy people here, and they might leave or not visit as often. And then the difficult questions based in reality might not be answered.
You just have to take the flak with the good stuff, fire away on those "stupid questions", and let the screen bits fall where they may. You're anonymous, so does it really matter anyways?
Originally Posted by Banshee
Im in the minority, i have never found it amusing for even ...well except for that one guy that posts from his cellphone. Lol, but other than that, it gets annoying after awhile. Dont even get me started on how discouraged i am from even making a thread if all i could get are flaming bull**** comments, because i really have no one else to ask about my car, so a stupid question is more likely to come from me then anyone else.
I agree with you to some extent, but you have to realize that if every post was a dry, detailed, and carefully argued post, then the entertainment value would sink for a lot of technically savvy people here, and they might leave or not visit as often. And then the difficult questions based in reality might not be answered.
You just have to take the flak with the good stuff, fire away on those "stupid questions", and let the screen bits fall where they may. You're anonymous, so does it really matter anyways?
There is one last obstacle at this point though
. Its getting Tifos to realize how cool he is and to hear it from me. Its unfortunate he has me ignored lol...and that to some extent has a piddly grudge against me, for whatever reason.
01-28-2010, 09:35 AM
#54
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Im in the minority, i have never found it amusing for even ...well except for that one guy that posts from his cellphone. Lol, but other than that, it gets annoying after awhile. Dont even get me started on how discouraged i am from even making a thread if all i could get are flaming bull**** comments, because i really have no one else to ask about my car, so a stupid question is more likely to come from me then anyone else.
01-28-2010, 03:30 PM
#55
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this is a fun thread... some people at rennlist take many of these sorts of matters very seriously. most of you have no idea that i posted the most visited thread of all time on politics and controversy... and i was roasted from one end of the Porsche world to the other for offering the fema-camps-as-internment-camps hypothesis, for which i have some knowledge about...
while the matter of engine warpage may not easily be settled, at least nobody has been injured so far.
i consulted with a friend who's an aerospace engineer for boeing, and mentioned the idea of an engine sans cylinder heads and he agreed that an engine's shape may in fact change slightly if encouraged to do so. and that's precisely the problem (encouragement) when an engine (without it's cylinder heads under ton's of pressure) is up on a stand. in any case, aluminum is likely to undergo FAR LESS of a geometrical change than steel. aluminum is extremely brittle.
in other words... in the case of an aluminum block - no worries.
i can offer one SURE point of view: certain classes of deformations go over well, and some less so...
.
while the matter of engine warpage may not easily be settled, at least nobody has been injured so far.
i consulted with a friend who's an aerospace engineer for boeing, and mentioned the idea of an engine sans cylinder heads and he agreed that an engine's shape may in fact change slightly if encouraged to do so. and that's precisely the problem (encouragement) when an engine (without it's cylinder heads under ton's of pressure) is up on a stand. in any case, aluminum is likely to undergo FAR LESS of a geometrical change than steel. aluminum is extremely brittle.
in other words... in the case of an aluminum block - no worries.
i can offer one SURE point of view: certain classes of deformations go over well, and some less so...
.
Last edited by odurandina; 01-28-2010 at 04:25 PM.
01-28-2010, 04:15 PM
#56
Three Wheelin'
Of course it will bend!
Same way when you put put the engine inside to the bay, the V angle will get smaller and smaller, because your block is drooping in between the two engine mounts. The plastic belly pan on my 2.7T audi is what keeps the engine block from leaking out of the bay or colapsing into an I6.
This is the same audi on which the gas milage quadrupled using a hydrogen-oxygen separator kit from ebay and has 550HP with the maf chip from the same venue.
Same way when you put put the engine inside to the bay, the V angle will get smaller and smaller, because your block is drooping in between the two engine mounts. The plastic belly pan on my 2.7T audi is what keeps the engine block from leaking out of the bay or colapsing into an I6.
This is the same audi on which the gas milage quadrupled using a hydrogen-oxygen separator kit from ebay and has 550HP with the maf chip from the same venue.
01-28-2010, 05:48 PM
#58
Race Car
So... if an N/A block, while fastened to an engine stand, were placed on a tread mill....
would it be possible to turbo it?
More importantly, would a set of wheels I can't find on e-bay any more fit on the early car with late suspension components?
And once said, turboed, N/A engine was re-assembled, which oil should I use in it?
Should I observe any special break in procedures?
would it be possible to turbo it?
More importantly, would a set of wheels I can't find on e-bay any more fit on the early car with late suspension components?
And once said, turboed, N/A engine was re-assembled, which oil should I use in it?
Should I observe any special break in procedures?
01-28-2010, 06:37 PM
#59
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Who do i have to pay off or sleep with to get those fancy titles? Now I have something to aspire to.
01-29-2010, 01:22 PM
#60
i consulted with a friend who's an aerospace engineer for boeing, and mentioned the idea of an engine sans cylinder heads and he agreed that an engine's shape may in fact change slightly if encouraged to do so. and that's precisely the problem (encouragement) when an engine (without it's cylinder heads under ton's of pressure) is up on a stand. in any case, aluminum is likely to undergo FAR LESS of a geometrical change than steel. aluminum is extremely brittle.
.
.
