| Author | Message | ||
     Forevernow |
can any one give me some advice on setting cold squish?i am tearing apart my motor tomorrow for headporting and want to get the right gaskets or cylinder machineing if nessisary,ive been told to set it anywhere from 20 thou to 40 from differnt people wich doesent help me much ,also is solder between the piston and head the best way to check it?i am using hurricane pistons | ||
| Jimidan |
If you can get your hands on Battle 2Win mag, the last Issue 15, Spring of 2002, Aaron Wilson gives an excellent primer on Squishing for Power, complete with pictures. After doing with out B2W for a while, I realize what a resource for the Buell owner it truly was. Reg, come back, we will pay twice the price! | ||
| Notsip |
Forevernow, When setting piston to cylinder head squish there are several things to take into consideration. What cylinders are you going to use, Aluminum or Cast. If using aluminum, do they have a cast sleeve or are they plated. If you are using cast cylinders you can set the squish at .035" measured across each wrist pin. If you are using aluminum cylinders with a cast sleeve you can set the squish at .032-.035". If you are using aluminum cylinders that are plated you can set the squish at .030-.032". The reason there is a difference on each one is that the cylinders have different growth factors. The best cylinder is a cast cylinder (Axtell) because they keep better cylinder bore concintricity and control the growth better than any other cylinder on the market. The aluminum cylinder with a cast sleeve is the next best cylinder because it doesn't distort and grow as much as the plated cylinder does, which is the worst of the aluminum cylinders. They don't have much stability to them. The rod and piston growth is the same on each engine unless you are using aluminum or titanium rods which has a different growth factor. I hope this helps you. Notsip | ||
| Aaron |
I could show you LOTS of hard data that contradicts your statements. | ||
| Notsip |
Aaron, Show me what you have. I may need corrected, but I doubt it. Post your findings so I can review them. Notsip | ||
| Blake |
Notsip, Dimensional stability is primarily a product of the cylinder's ability to maintain a consistent axisymmetric temperature gradient. Therefore considering that the convective cooling environment (cooling airflow) is virtually identical for each configuration/type of cylinder, a material that conducts heat better will provide superior dimensional stability. Which material is a better conductor of heat, aluminum or iron? | ||
| Forevernow |
so...i have stock cylinders bored 15 over .030 sound right?any opinions? | ||
| Rick_A |
Save the small overbores for rebuilds...otherwise you're just shortening the useable life of your cylinder. If you want a bigger bore get a bigger cylinder. That's just my opinion, of course. As far as cylinder growth and concentricity I've always heard it being the total opposite to what you stated Notsip. | ||
| Forevernow |
this was just a rebuild to began with, the motor was useing oil and failed a leak down test,i had the dealer rebuild it ,partly paid for by the warranty so i desided to have them use 15 over hurricanes instead of 15 over t-storms,250 miles later i have desided to tear it back apart get the heads done and put it back together before summer,i just want to set the squish correctly because the dealer just stuffed some gaskets in it and said"good enough" | ||
| Aaron |
Bill: people have different theories about how much squish is optimimum. It's just another in the long list of things where you can ask an opinion of 5 experts and get 6 answers. I know people who push it under .020, I know people who insist .035 is a minimum. I've experimented with it some myself and I can point to situations where I was under .020 and had no contact going on and other cases where I was over .035 and got contact. The wrist pin bushing condition and fit plays a huge role, as do the materials and construction of the pistons, cyls, and rods, the core shift in the heads, and even the fit of the piston. It just ain' that simple that a person can give you,over the web and without looking at anything, the perfect number within a few thou. Want to see a BIG variable? Take a look at your heads, where the squish shelf meets the deck, and compare how much excess deck you have on one side versus the other. These are cast in squish bands and they're all over the map. That's going to do a LOT to dictate what your measurements look like and how hard you can push things. Cutting that excess deck off and cutting the squish shelf accurately changes the equation dramatically. Now, *generally* speaking, the factory has a lot of tolerance stackup and the average motor ends up pretty wide. Assuming typical clearances, wrist pin bushings, fits, materials, etc, .035 or so is *generally* safe. If you want to put some effort into it, though, you can get it tighter and reap some small benefits. That's the kind of thing we pay attention to in race motors. Is it worth it to you? With what you're doing, is it worth it to chase this level of perfection? Those are questions only you can answer. Best of luck, AW | ||
| Forevernow |
thanks Aaron,right now the squish is about .065 with .043 head gaskets,if its the same after the heads are done i think im going to get .020 cut off the cylinders and use .030 gaskets so if i do have a clearance problem i can go back to the thicker gaskets,this is no race motor but i am trying to get set it up the best i can,within reason | ||
| Notsip |
Aaron, I am glad that we somewhat agree on the amount of squish that Forevernow should use. By looking at his figures he has decided to set the squish at .032" which would be appropriate for his engine combination. If I recall I said it should be set at .032"-.035" for the aluminum cylinders with cast sleeves. We both took different avenues to get there but the answer was the same. All that matters is that Forevernow has the correct measurement. I would still like to see your "HARD DATA" about your cylinders, this could be very interesting. Lookin Foward To Hearing From You! Later, Notsip | ||
| Notsip |
Blake, Trying to figure out what all those big words mean. You "REALLY" need to bring this down to the level where the normal person can understand what you are saying. My understanding of what you are saying is that aluminum is a better conductor of heat. You are correct in stating this. But I have a few questions on this for you. Let's go back to Science '101', cold causes contraction and heat causes expansion. The colder it is the more contraction you have, the more heat you have the more expansion you have. Do we agree on this? Now lets make an example. Replacing a valve seat in a cylinder head. If you are going to replace a valve seat in a cast iron head you only need to set the squeeze (interferance fit) at .0015"-.002" to keep the valve seat in the head. Now if we are going to replace a valve seat in an aluminum head you must set the squeeze (interferance fit) at .0045"-.0055" to keep the valve seat in the head. So what this tells me is that aluminum conducts more heat than cast and therefore it grows more than cast does. This is why you need more squeeze on the seat to hold it in place so it doesn't fall out when the aluminum grows away from the seat. Now lets talk about cylinders. A aluminum cylinder conducts more heat than a cast cylinder does, so this means that the aluminum cylinder is going to grow more than a cast cylinder will. Now that we understand this in simple terms what does this mean. It mean's that a aluminum cylinder is going to grow a lot more than a cast cylinder will, but where is all this growth going to grow to. It can only grow in heigth only a certain amount because you have the cylinder capture between the engine case and the cylinder head by using approx. 35-40 lbs. of torque to hold it together and this controls the amount of cylinder growth. With the cylinder controlled in the growth heigth this means that the cylinder can on releive it's expansion pressure by growing laterally. This is beacuae aluminum doesn't have much stability to it. So when this happens the aluminum cylinder is going to expand towards the area that has the least resistance and this is in towards the cylinder bore which causes another set of major problems (which I'm sure we will dicuss at another time) and that is cylinder bore deflection and distortion which then causes piston ring seal failures (Blow-By). Now if you use a aluminum cylinder with a cast sleeve installed in it you will at least give it more structure and reduce the amount of cylinder bore deflection, because cast iron or ductile iron sleeves are more rigid. Cast iron cylinders are the most rigid and has the least amount of cylinder bore deflection. This is why everyone who wants to make power uses cast or ductile iron cylinders. Question? What cylinders did Aaron use on his Bonneville engine? Cast (Axtell) or Aluminum? If you have any "HARD DATA" that contradicts these facts, please post it for review. Till We Chat Again, Notsip | ||
| Blake |
Notsip, "So what this tells me is that aluminum conducts more heat than cast and therefore it grows more than cast does." Conductivity and thermal expansion are two different things. Conductivity is the ability of a substance/material to transfer heat energy. Thermal expansion is the tendency of a material to expand with increasing temperature. Yes, aluminum has a greater coefficient of thermal expansion than cast iron so when pressing new seats an aluminum head requires more interference than an iron one. What material comprises the pistons? "An aluminum cylinder conducts more heat than a cast cylinder does,... " Another way to describe that would be to say that an aluminum cylinder conducts heat more efficiently/quickly than an iron cylinder. "so this means that the aluminum cylinder is going to grow more than a cast cylinder will." Again, conductance is independent from thermal expansion. However, aluminum alloys are also more thermally expansive than iron, so if you assume that the aluminum and iron cylinders are at the same elevated temperature, yes, that is a valid conclusion. But since aluminum is so much more efficient than iron in conducting heat, it will be significantly cooler. So your theory may need further analysis. "With the cylinder controlled in the growth height this means that the cylinder can only releive it's expansion pressure by growing laterally." That is not accurate. When a homogenous isotropic material, like most cast metals are, is heated, it wants to expand equally by xx% in all directions. If you have a sphere it stays spherical. If you have a cylinder, it stays cylindrical. If you constrain one dimension as the studs do to the cylinder, the cylinder does not relieve the added axial stress by expanding laterally. Yes there will be some negligible Poisson's ratio effect (small lateral expansion under axial compression), but that very slight distortion pales in comparison to the effects of nonuniform temperatures from the front to the back of each cylinder. "This is because aluminum doesn't have much stability to it." I think you are saying that aluminum is not as stiff as iron. If so, you are correct. Aluminum is however an extremely stable structural material. "So when this happens the aluminum cylinder is going to expand towards the area that has the least resistance and this is in towards the cylinder bore..." That is not quite true. It would also expand equally outwards. Again, the fattening of section due to compression is a small effect. The cylinders are bored while in a fixture that simulates the effects of the torqued down high tension studs. Left unrestrained, the typical aluminum alloy will grow approximately 0.000013" per oF for every inch of length, and there you have the coefficient of thermal expansion for most aluminum alloys, 13E-06 IN/IN/oF. Poisson's ratio for aluminum alloys is 0.33. This means that lateral strain introduced by the effects of an axial load will be just one third of the axial strain. Where strain is equal to total deflection divided by length or breadth as applicable. If you elastically (no yielding/permanent/plastic deformation) compress a 10" long bar of aluminum by 0.001", it has a strain of 0.001"/10"=0.0001. If that same bar were one inch diameter in section, it would deform through expansion laterally by 0.33*0.0001*1"=0.000033". Not very significant is it? Since the cylinder height to thickness ratio is fairly high, we would expect a similar relationship. Let's check... If the cylinder were subjected to a 200oF temperature increase it would try to deform/elongate by 13E-06*200=26E-04=0.0026" for every inch of height. A cylinder is less than 6" tall right? So it would not try to expand more than 6*0.0026"=0.0156". The cylinder wall thickness even at 0.75" would see a Poisson's effect expansion of only 0.33*0.0026*.75=0.00064". If half of that is outward expansion and half is inward, then the bore diameter decreases by the same 0.00064". Even doubles it is only 0.0013". With a coefficient of thermal expansion of 13E-06 that same 200oF temperature increase would cause a 3.5" bore aluminum alloy cylinder to expand by 13E-06*3.5*200=0.0091", the same amount that an aluminum piston would expand if subjected to the same thermal environment. Actually a piston could easily become hotter than the cylinders as it only has the hot oil and connecting rod to help cool it. Iron has less than half the thermal conductivity, (bad for cooling) and half the thermal expansion (different from pistons) compared to aluminum alloy. What is a typical piston to cylinder clearance? Somewhere like 0.020"? 0.0013" is not significant in that light, is it? "...which causes another set of major problems (which I'm sure we will dicuss at another time) and that is cylinder bore deflection and distortion which then causes piston ring seal failures (Blow-By)." See above. That is what I'm saying is the major issue. FYI, iron has about half the thermal expansion as aluminum. It also has about half the conductance. Anyway, I still contend that what causes the most severe distortion of cylinders is the difference in temperature as you travel around the circumference of the cylinder. That is of course due to the erratic and inconsistent flow of cooling accross the front and sides versus the rear of each cylinder. I'm not sure if iron has an advantage over hypereutectic aluminum alloys in distortion due to thermal gradient. The iron distorts less due to temperature, but the aluminum conducts heat more efficiently by a factor of over two to one, and thus maintains a more uniform and cooler temperature. Wouldn't an aluminum cylinder expand more uniformly along with the aluminum piston, the aluminum cases, and the aluminum cylinder head? What happens when an iron cylinder doesn't expand as much as the hot aluminum cylinder head or worse, the piston? I believe that the cylinders in Aaron's 208 mph LSR Buell were plated aluminum. The 183 mph RR1000 Team Elves LSR bike used Axtell iron cylinders. | ||
| Aaron |
Blake: The 100" motor used Axtell aluminum cylinders which have cast iron sleeves. It's a well constructed cylinder, and they performed flawlessly under some really severe conditions. The XR1000 motor used it's factory stock cast iron cyls. They're heavy (obviously) and strong. Notsip, what I was disagreeing with is the notion that a sleeved cylinder is stronger than an all-aluminum cylinder. The Millennium cylinder in particular is far superior to the stock piece in terms of strength and resistance to distortion. It ain't even close. It's a VERY easy thing to measure, no rocket science involved. I don't really see the point in sharing my measurements since you've obviously already made up your mind. But if you're really interested in the truth, I encourage you to make the measurements yourself. It's an eye-opener, makes you realize how bad them stock things are. | ||
| Hobanbrothers |
Just the facts: When we were using stock (cast iron sleeve) cylinders we would need to straighten out (over bore) cylinders after every 2nd race weekend. When we switched to an aluminum sleeved/millenium cylinder it more than doubled the time frame of frequency of replating and one set did the whole season. Real world application and a fact. | ||
| Blake |
Aaron, Thanks for the correction. My bad. Hobanbro, Real world information is always appreciated. Thanks for taking the time to describe your experiences with different cylinder configurations. | ||
| Aaron |
Hey John! Great to finally meet you last weekend. You guys kick some butt this year!!! | ||
| Hobanbrothers |
How do you do that?? I spoke with your wife today as Brian is not back yet and you are at this time some place far away. I guess you computer guys have all the trick stuff, huh? Very nice meeting you also, I told your wife you are a very pleasant man to hang with. She said, "some times"?? Anyways, hope you enjoyed the show!! Thanks for the encouragement, you know our motto, "Win, spin, or pitch it through the fence!" Blake, you guys do all the figuren' with long equations and such (Dont take that the wrong way as our rider Jeff is the same way), my learning curve is typically--"start with a little science, then, beat the ever liven' crap out of it, and if it lasts, its all good!" | ||
| Court |
>>>I told your wife you are a very pleasant man to hang with. She said, "some times"?? Okay....I hereby declare this the "Aaron Wilson Quote of the Year"  | ||
| Rick_A |
So, how's the properties of the cast iron cylinders compare to the aluminum iron sleeved? I would think the sleeved would be more prone to distortion despite having better cooling, right? | ||
| Aaron |
Yeah, I'm on the other side of the world at the moment. Flew out of Indy and left Brian to take the truck home. BTW, it's 98 degrees here Rick, I've never made that particular comparison, but I betcha Ron Dickey has, and I betcha he'd say it was cast iron by a mile. He's a sharp cookie on this stuff. Keep in mind that not all sleeved cyls are created equal, too. The factory ones have very little aluminum around a relatively small sleeve. Axtell's are totally different. | ||
| Benm2 |
Cast iron liner with different rate of thermal expansion than alumimum will distort more than either a cast iron or cast aluminum (coated) cylinder, due to the aluminum moving more than the sleeve, if they are heated to the same uniform temperature. Interesting question: what does the heat distribution pattern look like for any of the three options? With the "rule of thumb" being 80% of combustion heat is lost through the head (Cameron's book), the area near the head would be hottest. An all-iron cylinder would conduct the least amount of combustion heat down the cylinder, an aluminum cylinder the most. Do the cast iron cylinders "open up" at the top, but not change length much? Do all-aluminum cylinders maintain more uniform top-to-bottom gradients? For a more uniform temperature rise, they would expand more, subjecting themselves to more compressive stress from the cylinder studs (which are steel), perhaps "beer-barreling" a little bit? When boring a cylinder with a torque plate, is it torqued to the tension that matches a "cold" cylinder, or to a "hot" cylinder? | ||
| Notsip |
Blake, I could use your expertise on figuring out the actual clamping pressure on the cylinder under cold conditions and then under hot conditions ( I am going to let you decide what the operating temperature of the cylinder would be. ) with 35 ft. lbs. of torque applied to each cylinder stud. And then what is the elasticiy of the cylinder stud and cylinder head screw. For a baseline on gaskets lets use a .020" metal base gasket and a 3-pc. Cometic head gasket .043" thick. I am trying to figure out some data so we can continue our conversation. I appreciate your input in this debate, as I am sure that everyone will learn something from it. I have several thousands of hours of "Real-World" data collected in our engine dyno ( not a squirrel cage dyno ) computer and I'm trying to apply what you have said so I can better understand what I am seeing from all of the data collected. When completed we can discuss what information that I have obtained and apply it. Thanks, Notsip | ||
| Blake |
Notsip, NOW WERE TALKING!!! A man after my own heart. ![:]](http://www.badweatherbikers.com/buell/clipart/proud.gif) Can you provide material/alloy/heat-treat specifications and stud, screw and cylinder geometry? Also cylinder head geometry. I would need cross section and thread geometry for the studs/screws. Cross sectional geometry/area for cyhlinder, fins excluded. It is not as simple as it first might appear, but we can come up with a bounding analysis (max/min possible). | ||
| Benm2 |
Blake: Material is probably some standard casting alloy, for both the aluminum and cast iron material. I think typical casting alloys for Al are 356. material properties are available at http://www.matweb.com. Thread geometry is available from any machinery's handbook, and you probably already know the thread designation. For generating a first comparison, I'd use standard spec's for grade-8 fasteners. There's not significant differences in material properties for high-strength steel alloys commonly used for hardware. Also, again for comparison, I'd assume the "bounding conditions" at head & cylinder base is that they are significantly rigid enough not to be deflected. If you don't do that, I'd guess at 1" thick Al plates bolted at each end. Real analysis of the stresses and deflections based on true geometry probably exceed the amount of spare time you have to setup the FEA grids, and I'm guessing you don't have the software to run it anyway. (If you do, I'm jealous) As far as a heat transfer model, you could set that up separately, just for fun. If you assume some standard air conditions (why not just standard conditions??) and some velocity of the air, a heat-transfer text should provide some insight as to how to develop the temperature profile of the cylinder. I'd concentrate a heat load at the head end, set at some known operating head temp (350F?), and see what the base temperature turns out to be. Hmm, conduction of heat down the cylinder, convective losses from the fins, at least one bi-metallic interface, sounds like a simple analysis of that alone could burn a few days. In my younger days, I remember doing a two-month long project to determine why a particular shaft in a gearbox was failing. I did stress analysis, and I wrote a simple shaft FEA program to map the stresses. Did lots of charts in mathcad, and I mapped out all the dynamic & static loads on the shaft. At the end of the day, I made the shaft bigger, and added a fillett at a diameter transition. And, for fun, I found someone to forge shaft blanks from 4340. Never broke again, but probably just could have made the shaft bigger where it was breaking and gone with that from the get-go. Analysis paralysis, its called, isn't it? As indicated above, the real world provides the quickest data, for those with the MONEY to do the tests and find out what works best. For the rest of us, it's the TIME to pose the questions, and try to produce a recommendation based on the data. The bitch is trying to make the two agree... | ||
| Notsip |
Blake, Looks like Ben has given you the information that you were asking for. If there is any "Real World" Data that I can provide let me know. Thanks for your help!!! Benm2, Thanks for your input in this matter. If there is any "Real World" Data that I can provide for you also just let me know. Notsip | ||
| Blake |
I need geometry. I don't know the size of the studs/screws. I have no idea of the cross section of the cylinder. I'd like to know the exact grade of the stud and screw so I can estimate max reload. There are HUGE differences between the yield strengths of different high strength fasterners. Ben, have at it. Sounds like you enjoy tackling new types of analysis. We cannot get by without it anymore. If we were to design a modern jet aircraft or a skyscraper based on trial an error, the families of the victims tend to get upset. | ||
| Benm2 |
Blake: For the purposes of developing comparative data, exact geometry is not required. Also, I'd start off with the assumption that no real engineering team would develop an engine that loaded the studs to yield during operation (based partly on your statement that trial-and-error doesn't work well). Anyway, the studs look to be about 3/8". I'd start with 1/4" wall iron for the sleeve, and 3/8" aluminum around it. Then, I'd try 1/2" iron for solid barrels, and so on. First, I'd do the thermal convective stuff to try to determine a temp profile. Then, I'd divide the cylinders into maybe 10 sections (to correspond to the temp profile) and estimate thermal strain per section. Then to the stress stuff. Also, racing is more trial & error than the real world allows, as you assert. That's why streetbikes are (relatively) heavy & slow. I think that coated Al cylinders have been used on Buell racebikes for a LOOOONG time. General consensus on this board is they're better. Why haven't they made the production line?? Might have something to do with those real world limitations you speak of. Anyway, with an old house, an old truck, an M2 that needs race prep, a son to watch, and a pregnant wife, I'm low on spare time. So, no analysis from me. | ||
| Spiderman |
HEY AARON I'm torn between the Axtell cast iron and Aluminium Nikelsel (my spelling is off I know:P)Could you give me those numbers of expansion. Also with the Axtell's steel and aluminium cylinder. you can e-mail to me if ya want. |
