Stock Studs vs. Enlarged Studs
08-15-09, 05:25 PM
#26
Studs are a backwards step from bolts? How do you figure? I'll have to go redesign our 2200 hp pumps here at work if that's the case (sarcasm).
I personally don't believe in using larger studs in place of dowel pinning. The primary loads on the studs is not the rotational stresses but merely the force of holding 5 plates together front to rear. Rotational loads are primarily absorbed by the dowel pins. Detonation forces are trying to push the faces of the rotors inwards and the housing walls outwards. No stud or dowel can help that.
I think the biggest mistake that people make is in thinking that the tension bolts, even larger ones, have a huge impact on controlling rotational twist on the housings. The stock ones being smaller than the hole they insert into aren't doing crap to help this. Larger ones that fit tightly into close tolerance bored holes do a bit better but each sharp little edge from the top of a thread is a stress point and you never want an edge to bear any loads if possible. Round or smooth surfaces are best hence the shape of the dowel pins. While there is some rotational stiffening benefit to be had from new larger tension bolts, it's still mostly controlled by the dowel pins. I design stuff like this all day at work for the oil drilling machinery and loads and their directions are very important to know.
A better option would be dowel pins that go all the way through the engine from front to rear. This reduces the loads from having 4 edges on the ends (which are relieved with a small chamfer btw) since we have 2 dowels back to back and have a total of 4 in the engine. If we could replaces these with just 2 long dowels, we'd spread this load out along the length of the pin better which would help control stresses in the end and intermediate housings. This alone could potentially save S4 housings from breaking at the dowel land locations. Better yet would be to add at least 2 more dowel pins all the way through the engine.
Let the dowels control the rotational forces. Let the tension bolts control the front to rear forces. As for the forces resisting detonation that are trying to split the engine apart in the last dimension, don't detonate! We can't strengthen this area without doing some serious modding to the housings themselves. For most street driven people that don't have 500+ hp that still have engine related strength problems, the dowel issue would take care of much of the problems.
I personally don't believe in using larger studs in place of dowel pinning. The primary loads on the studs is not the rotational stresses but merely the force of holding 5 plates together front to rear. Rotational loads are primarily absorbed by the dowel pins. Detonation forces are trying to push the faces of the rotors inwards and the housing walls outwards. No stud or dowel can help that.
I think the biggest mistake that people make is in thinking that the tension bolts, even larger ones, have a huge impact on controlling rotational twist on the housings. The stock ones being smaller than the hole they insert into aren't doing crap to help this. Larger ones that fit tightly into close tolerance bored holes do a bit better but each sharp little edge from the top of a thread is a stress point and you never want an edge to bear any loads if possible. Round or smooth surfaces are best hence the shape of the dowel pins. While there is some rotational stiffening benefit to be had from new larger tension bolts, it's still mostly controlled by the dowel pins. I design stuff like this all day at work for the oil drilling machinery and loads and their directions are very important to know.
A better option would be dowel pins that go all the way through the engine from front to rear. This reduces the loads from having 4 edges on the ends (which are relieved with a small chamfer btw) since we have 2 dowels back to back and have a total of 4 in the engine. If we could replaces these with just 2 long dowels, we'd spread this load out along the length of the pin better which would help control stresses in the end and intermediate housings. This alone could potentially save S4 housings from breaking at the dowel land locations. Better yet would be to add at least 2 more dowel pins all the way through the engine.
Let the dowels control the rotational forces. Let the tension bolts control the front to rear forces. As for the forces resisting detonation that are trying to split the engine apart in the last dimension, don't detonate! We can't strengthen this area without doing some serious modding to the housings themselves. For most street driven people that don't have 500+ hp that still have engine related strength problems, the dowel issue would take care of much of the problems.
....
08-15-09, 05:35 PM
#28
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Please don't read any tone into this, I'm not trying to be a smart-*** or any of that. . . just trying to understand this a bit better.
The only way I can see your compression going up from the type of force a stud would apply would be by pinching the side seals such that they can't "give" at all. That doesn't seem like something that could work very well for very long.
Can you please describe why you think studs increased your compression? If you wouldn't mind sharing details of that particular build, I'm sure the whole community would appreciate it.
The only way I can see your compression going up from the type of force a stud would apply would be by pinching the side seals such that they can't "give" at all. That doesn't seem like something that could work very well for very long.
Can you please describe why you think studs increased your compression? If you wouldn't mind sharing details of that particular build, I'm sure the whole community would appreciate it.
08-16-09, 01:00 AM
#30
BTW, i found a shop that sells A2 precision ground metric rods in 3' lengths
I have thought long and hard about the solution to this. I think the problem with the oversized studs is that it applies pressure to and area that was never designed to take any loads other than coolant pressure and the trough bolts, secondly by the time you machine the front and rear irons to accept a 1/2" stud the castings are so thin that they are substantially weakened. If you could make a stud that was necked down in the front (10mm X 1.0) and say 7/16 in the rear you would have the benefits of the studs without weakening the front and rear irons. For now i will try the pins and solid dowels but on my next build i will make my own necked down studs.
08-16-09, 10:17 AM
#31
Red Pill Dealer
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I wonder if the differences in diameter between the stock bolts and 1/2" studs isn't the problem for people using the studs on four corners. The torque applied to a bolt is not arbitrary. Bolts stretch when torqued. The proper torque for a bolt is reached after it has stretched a certain amount and, theoretically, is at it's strongest. I've seen graphs of this and the strength goes up as it stretches till a certain point is reached and then the bolt is permanently stretched or breaks. Bolts at proper torque have very little stretch left in them and won't stretch under the designed load.
The torque to reach the proper strength for a 1/2" stud is greater than a 10 mm one. So is it's clamping force at proper stretch. This would produce greater clamp (and possibly stress) at the four corners. Torquing a 1/2" stud to the same torque as a 10 mm one changes the equation because it has not been stretched to it's maximum strength. Therefor could possibly stretch more even though it's a larger diameter.
I suppose this is also why you never see more than one sized head bolt used on piston engines. Just a thought.
The torque to reach the proper strength for a 1/2" stud is greater than a 10 mm one. So is it's clamping force at proper stretch. This would produce greater clamp (and possibly stress) at the four corners. Torquing a 1/2" stud to the same torque as a 10 mm one changes the equation because it has not been stretched to it's maximum strength. Therefor could possibly stretch more even though it's a larger diameter.
I suppose this is also why you never see more than one sized head bolt used on piston engines. Just a thought.
08-16-09, 03:43 PM
#32
Old [Sch|F]ool
Actually I work on quite a few engines that have two or three (or four!) different length head bolts.
What you say is true regarding ultimate bolt strength, however the clamping force you want isn't necessarily everything the bolt can handle. Wheel studs might be able to handle 150ft-lb of torque but if the wheel can only handle 80ft-lb then you torque it to 80, as an example.
A couple interesting things seen, though.
Exhaust manifold bolts that have a ~2" spacer/washer between the head and the manifold. Why ever could that be? Accomodate things shifting around without putting too much side-stress on a shorter bolt, which could result in a cracked manifold or broken bolts? Nahhh...
The trend in cylinder head clamping is to go with longer and longer bolts. The bolts on some VWAG products are waaaay long. Likewise, the head gasket problems GM had with the Quad 4 were fixed by making the head bolts about twice as long. And the Ford 4.6l practically has its head bolts rooted in the main webs. Accomodate thermal expansion by letting the bolt stretch (while still being acceptably tight when cold) instead of crushing the snot out of the gasket? Nahhh...
I always wondered what problem stronger bolts (in rotary) were meant to solve.
What you say is true regarding ultimate bolt strength, however the clamping force you want isn't necessarily everything the bolt can handle. Wheel studs might be able to handle 150ft-lb of torque but if the wheel can only handle 80ft-lb then you torque it to 80, as an example.
A couple interesting things seen, though.
Exhaust manifold bolts that have a ~2" spacer/washer between the head and the manifold. Why ever could that be? Accomodate things shifting around without putting too much side-stress on a shorter bolt, which could result in a cracked manifold or broken bolts? Nahhh...
The trend in cylinder head clamping is to go with longer and longer bolts. The bolts on some VWAG products are waaaay long. Likewise, the head gasket problems GM had with the Quad 4 were fixed by making the head bolts about twice as long. And the Ford 4.6l practically has its head bolts rooted in the main webs. Accomodate thermal expansion by letting the bolt stretch (while still being acceptably tight when cold) instead of crushing the snot out of the gasket? Nahhh...
I always wondered what problem stronger bolts (in rotary) were meant to solve.
08-17-09, 09:44 AM
#33
There comes a certain point where harder and harder tension bolts aren't going to do any good and eventually the reverse is true. As was mentioned a stud or bolt needs a certain amount of load. However if we use a tension bolt that is so hard that it can't "stretch" to it's required amount before the housings compress too much or the threads in the end housings fatigue, then we've got problems. I've often wondered if some companies offering stronger tension bolts chose them because they actually did the calculations necessary to determine if a stronger bolt was necessary (or even a good idea) or if they chose their new material out of a catalog because it's properties said it was stronger? You definitely don't want a stud that requires so much tension that in order to get it where it needs to be you've physically started to crush the aluminum rotor housings.
Remember when metals heat up, they expand. Aluminum more so than cast iron and at a different rate. Ever wondered how tight your bolts are at varying engine temperatures? Think about that one for a while! How do these temperature changes on the bolts affect their length and hence their tightness? How does the clearance change between the bolts and the housings? Ever thought that maybe there needs to be some slop in their clearances?
A larger tension bolt (stud) that needs to be machined into the engine housings to fit is only going to be clearanced properly at whatever temperature you machined it at. Here at work on our large crankshafts, we've seen up to 3 thousandths clearance differences between parts machined in cold weather vs hot weather and they were machined to the same tolerances. It takes a good machinist to know his material and how to compensate for temperature variations when machining. Think 3 thousandths isn't very much? When your total tolerances are within 3 thousandths, that means that temperature alone is enough to take you to your limits. This isn't even accounting for other variations.
My personal opinion is to replace the tension bolts with studs since you get tightening torque more evenly applied over the entire length rather than right on the head. However I'd use a stud that is the same equivalent diameter which means some "slop" going through the engine. I'd just coat them with rtv to absorb any vibration but at the same time leave plenty of give for any material expansion. Then I'd rely on twist to be controlled by dowels that extend all the way through the engine front to rear. I'd use 4 of them. I know some people say that because the housings get a little thin from machining that they'd be weaker. While I'd normally agree with this, you need to remember how you are spreading the loads out among a greater amount of studs. This area doesn't need to be as thick as it would if only 2 dowels were used. The loads applied to these areas actually aren't in the direction you'd think they'd be anyways so it isn't that big of a deal. There is always a certain point in the power department though where you'll still hit a limit when it comes to the strength of your housings and end plates. When machining spots larger for new dowels, you absolutely must machine in a relief at the bottom of the hole. It's just a small angle. You do not want it to be a sharp edge. This is a point of stress and will lead to cracking. If you relieve it, you'll get rid of a potential cracking area. I have no doubt that many people who machine their housings that see breaking here are blaming it on the material thickness rather than the fact that they didn't machine in a relief area. One issue is being misinterpreted as another.
Most people aren't having a problem with blowing their engines apart from front to rear. Most people aren't breaking tension bolts although a few have here and there. For the most part this isn't an area that needs attention. You need to deal with the areas that are problematic and then figure out what the loads are in those areas and in which way they are being applied. Then you go about finding a solution. Just arbitrarily adding dowels or stronger tension bolts may not be a cure. Maybe it is. It depends on the situation. If you are cracking housings because you are making tons of power, the solution might be to carefully weld on vertical strengthening ribs to the rotor housings on the spark plug side. Obviously there are some serious issues with getting this done such as how to get to the plugs and how not to warp the housings in the process of welding. One thing that piston engine builders do when making more power is to find ways to strenthen the block. We just don't see that on rotaries since it's not easy to do. We can't just go buy a stronger one. When you make lots of power, far beyond what the engine was designed for, it stands to reason that your material choice or thickness should also be accounted for. No one does this. They do what they know, break it, and then find something else to blame when the real issue is that they didn't address a problem area at all.
Start thinking "outside the block" a bit and you'll find some creative new ways to get more from the engine. Remember, even the R26B race engine had external stiffening plates but theirs were top and bottom with cross bracing.
Remember when metals heat up, they expand. Aluminum more so than cast iron and at a different rate. Ever wondered how tight your bolts are at varying engine temperatures? Think about that one for a while! How do these temperature changes on the bolts affect their length and hence their tightness? How does the clearance change between the bolts and the housings? Ever thought that maybe there needs to be some slop in their clearances?
A larger tension bolt (stud) that needs to be machined into the engine housings to fit is only going to be clearanced properly at whatever temperature you machined it at. Here at work on our large crankshafts, we've seen up to 3 thousandths clearance differences between parts machined in cold weather vs hot weather and they were machined to the same tolerances. It takes a good machinist to know his material and how to compensate for temperature variations when machining. Think 3 thousandths isn't very much? When your total tolerances are within 3 thousandths, that means that temperature alone is enough to take you to your limits. This isn't even accounting for other variations.
My personal opinion is to replace the tension bolts with studs since you get tightening torque more evenly applied over the entire length rather than right on the head. However I'd use a stud that is the same equivalent diameter which means some "slop" going through the engine. I'd just coat them with rtv to absorb any vibration but at the same time leave plenty of give for any material expansion. Then I'd rely on twist to be controlled by dowels that extend all the way through the engine front to rear. I'd use 4 of them. I know some people say that because the housings get a little thin from machining that they'd be weaker. While I'd normally agree with this, you need to remember how you are spreading the loads out among a greater amount of studs. This area doesn't need to be as thick as it would if only 2 dowels were used. The loads applied to these areas actually aren't in the direction you'd think they'd be anyways so it isn't that big of a deal. There is always a certain point in the power department though where you'll still hit a limit when it comes to the strength of your housings and end plates. When machining spots larger for new dowels, you absolutely must machine in a relief at the bottom of the hole. It's just a small angle. You do not want it to be a sharp edge. This is a point of stress and will lead to cracking. If you relieve it, you'll get rid of a potential cracking area. I have no doubt that many people who machine their housings that see breaking here are blaming it on the material thickness rather than the fact that they didn't machine in a relief area. One issue is being misinterpreted as another.
Most people aren't having a problem with blowing their engines apart from front to rear. Most people aren't breaking tension bolts although a few have here and there. For the most part this isn't an area that needs attention. You need to deal with the areas that are problematic and then figure out what the loads are in those areas and in which way they are being applied. Then you go about finding a solution. Just arbitrarily adding dowels or stronger tension bolts may not be a cure. Maybe it is. It depends on the situation. If you are cracking housings because you are making tons of power, the solution might be to carefully weld on vertical strengthening ribs to the rotor housings on the spark plug side. Obviously there are some serious issues with getting this done such as how to get to the plugs and how not to warp the housings in the process of welding. One thing that piston engine builders do when making more power is to find ways to strenthen the block. We just don't see that on rotaries since it's not easy to do. We can't just go buy a stronger one. When you make lots of power, far beyond what the engine was designed for, it stands to reason that your material choice or thickness should also be accounted for. No one does this. They do what they know, break it, and then find something else to blame when the real issue is that they didn't address a problem area at all.
Start thinking "outside the block" a bit and you'll find some creative new ways to get more from the engine. Remember, even the R26B race engine had external stiffening plates but theirs were top and bottom with cross bracing.
08-17-09, 11:59 AM
#34
Old [Sch|F]ool
(...)You definitely don't want a stud that requires so much tension that in order to get it where it needs to be you've physically started to crush the aluminum rotor housings.
Remember when metals heat up, they expand. Aluminum more so than cast iron and at a different rate. Ever wondered how tight your bolts are at varying engine temperatures? Think about that one for a while! How do these temperature changes on the bolts affect their length and hence their tightness? (...)
Remember when metals heat up, they expand. Aluminum more so than cast iron and at a different rate. Ever wondered how tight your bolts are at varying engine temperatures? Think about that one for a while! How do these temperature changes on the bolts affect their length and hence their tightness? (...)
The reason why rotaries tend to blow their coolant seals after a good overheat is because the aluminum, trying to expand faster than the tension bolts can, get crushed under the stress. This is evidenced by taking measurements after disassembly and finding the rotor housings to be thinner than spec.
Mazda found a thin balance w.r.t. the tension bolts between the engine staying together when cold and not destroying itself when hot. Beefier bolts or severely overtightening the factory ones will really curtail the engine's ability to withstand temperature. Probably a fair tradeoff for a drag engine, but I wouldn't want to try it on a street or endurance engine.
08-17-09, 12:21 PM
#35
Red Pill Dealer
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Originally Posted by peejay
Which is why good bolts/studs are undercut...
Rolled threads are actually stronger than cut because the grain of the rod is then pressed along the V of the thread. Think forging. Ultimately, their strength is subject to quality of manufacture (accurate representation of the thread, this can vary a lot).
Tension bolts are made this very exact same way.
08-18-09, 03:14 PM
#36
I've seen the same issue as Abel has claimed, ran for years with dowels in "secret" places and cracked plates, due to less material. We switched over to studs problem solved. I've also ran sleeved stock tension bolts as well, same basic idea as smaller dowels it's been working fine. Both motors make well over 700whp and over 600ft/lbs, with so many passes and pulls I can't count anymore. I think it's a matter of knowing what works and how it works. I wont say others are wrong, I wont claim I am right, I will say this is our experience.
Last edited by Zero R; 08-18-09 at 03:20 PM.
08-18-09, 06:54 PM
#38
Issues like if you don't slowly bring the motor up to temp you will crack your side housings from conducting rotor housing heat into the studs and expanding the studs in the cooler, less conductive, brittle cast iron side housings as Mazda found in the 60s when they tried it.
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
--------------------------------------------------------
The Wankel Engine
1971
Jan P Norbye
chapter 11 "Toyo Kogyo" (Mazda parent company)
page 272
"Thermal fatigue, as a result of alternate heating and cooling of a given area, was also a problem in early Mazda engines and caused cracking at stress concentration points around the spark plug holes. These cracks, in extreme cases, penetrated to the water jacket. The first approach of the Toyo Kogyo engineers was to improve the cooling to cope with the most critical condition- rapid acceleration of a cold engine. In winder the combustion chamber walls could suddenly rise from a low ambient temperature to 450 deg F. This was the reason for adopting the most modern type of bottom-opening thermostat: one that continuously controlled bypass flow as well as flow through the radiator. A further cause of the cracking trouble was lack of flexibility in the trochoidal walls and conduction of heat from it to the cold end housings through the bolts holding them together. Improved flexibility and reduced heat transfer were simultaneously achieved by separating the side-bolt bosses from the trochoidal wall, and housings made in this way proved completely resistant to thermal fatigue.
-----------------------------------
OK, got it? Thermal stress is causing the cracking.
Remember, between Mercedes, Curtis Wright and Mazda technologies we think of as new or cutting edge like aluminum rotors, ceramic apex seals, direct injection, ceramet wear coatings, side exhaust ports, combo ports, "stud kits", etc were all evaluated in the 50s and 60s...
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
--------------------------------------------------------
The Wankel Engine
1971
Jan P Norbye
chapter 11 "Toyo Kogyo" (Mazda parent company)
page 272
"Thermal fatigue, as a result of alternate heating and cooling of a given area, was also a problem in early Mazda engines and caused cracking at stress concentration points around the spark plug holes. These cracks, in extreme cases, penetrated to the water jacket. The first approach of the Toyo Kogyo engineers was to improve the cooling to cope with the most critical condition- rapid acceleration of a cold engine. In winder the combustion chamber walls could suddenly rise from a low ambient temperature to 450 deg F. This was the reason for adopting the most modern type of bottom-opening thermostat: one that continuously controlled bypass flow as well as flow through the radiator. A further cause of the cracking trouble was lack of flexibility in the trochoidal walls and conduction of heat from it to the cold end housings through the bolts holding them together. Improved flexibility and reduced heat transfer were simultaneously achieved by separating the side-bolt bosses from the trochoidal wall, and housings made in this way proved completely resistant to thermal fatigue.
-----------------------------------
OK, got it? Thermal stress is causing the cracking.
Remember, between Mercedes, Curtis Wright and Mazda technologies we think of as new or cutting edge like aluminum rotors, ceramic apex seals, direct injection, ceramet wear coatings, side exhaust ports, combo ports, "stud kits", etc were all evaluated in the 50s and 60s...
08-18-09, 10:04 PM
#39
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what is the outer edge?
i would like to see a post from the car owner or tuner that has seen the tension bolts,ports etc rock stock block.what is the outer edge/max horse power they have made and or seen?i believe that there are some serious high horse power numbers out there with bone stock parts.it is all (almost all)in the tune up and lack of pre ignition/detonation.now i have not had my car on the dyno to verify what i believe the engine is really making.you can get an estimation of horsepower by 60 foot et,1/8 mile ET and mph 1/4 mile ET and MPH at wallaceracing.com in there "automotive calculators" program,let me give you a little info about my combo,2200 lbs with driver,c4 trans with trans brake,5500 stall converter,28x11.5x15 slicks.4.11 rear gear,E85 fuel,4X1600 cc injectors,FD engine rock stock ports intake and exhaust stock tension bolts reused,rotary aviation super seals,72mm turbo,3 inch inter cooler tube,big front mount inter cooler.being that my car weights 2200 pounds with me in it,and i have gone as quick as 1.306 60 foot time at 18 pounds of boost.with my 60 foot ET and the car weight, the engine has to make 500 horsepower to propel it in this distance and time.now for my 1/8 mile time and MPH.the car went 1.306 60 foot, 1/8 mile 6.409 @ 104 MPH.if you use the "automotive calculator" you will see that the ET and MPH are off for the "claimed "horsepower.this is because the tune up is still real fat at 6000 rpm and above.the next time to the track i will lean it out.at what point is the biggest load on the engine?is it the expansion from combustion?is it the outward forces of RPM?is it a 9000 rpm full throttle, slide your foot off the clutch?is it the reverse radial twist the the drive train applies to the engine?being that i have an automatic transmission with a trans brake does this combo create less of a radial shock that would twist the engine?(being that the engine is already loaded and making full power at the time when i release the trans brake).WHAT HAVE YOU SEEN????
Last edited by mazda rx2 rotary; 08-18-09 at 10:24 PM.
08-19-09, 09:47 AM
#40
Issues like if you don't slowly bring the motor up to temp you will crack your side housings from conducting rotor housing heat into the studs and expanding the studs in the cooler, less conductive, brittle cast iron side housings as Mazda found in the 60s when they tried it.
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
--------------------------------------------------------
The Wankel Engine
1971
Jan P Norbye
chapter 11 "Toyo Kogyo" (Mazda parent company)
page 272
"Thermal fatigue, as a result of alternate heating and cooling of a given area, was also a problem in early Mazda engines and caused cracking at stress concentration points around the spark plug holes. These cracks, in extreme cases, penetrated to the water jacket. The first approach of the Toyo Kogyo engineers was to improve the cooling to cope with the most critical condition- rapid acceleration of a cold engine. In winder the combustion chamber walls could suddenly rise from a low ambient temperature to 450 deg F. This was the reason for adopting the most modern type of bottom-opening thermostat: one that continuously controlled bypass flow as well as flow through the radiator. A further cause of the cracking trouble was lack of flexibility in the trochoidal walls and conduction of heat from it to the cold end housings through the bolts holding them together. Improved flexibility and reduced heat transfer were simultaneously achieved by separating the side-bolt bosses from the trochoidal wall, and housings made in this way proved completely resistant to thermal fatigue.
-----------------------------------
OK, got it? Thermal stress is causing the cracking.
Remember, between Mercedes, Curtis Wright and Mazda technologies we think of as new or cutting edge like aluminum rotors, ceramic apex seals, direct injection, ceramet wear coatings, side exhaust ports, combo ports, "stud kits", etc were all evaluated in the 50s and 60s...
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
--------------------------------------------------------
The Wankel Engine
1971
Jan P Norbye
chapter 11 "Toyo Kogyo" (Mazda parent company)
page 272
"Thermal fatigue, as a result of alternate heating and cooling of a given area, was also a problem in early Mazda engines and caused cracking at stress concentration points around the spark plug holes. These cracks, in extreme cases, penetrated to the water jacket. The first approach of the Toyo Kogyo engineers was to improve the cooling to cope with the most critical condition- rapid acceleration of a cold engine. In winder the combustion chamber walls could suddenly rise from a low ambient temperature to 450 deg F. This was the reason for adopting the most modern type of bottom-opening thermostat: one that continuously controlled bypass flow as well as flow through the radiator. A further cause of the cracking trouble was lack of flexibility in the trochoidal walls and conduction of heat from it to the cold end housings through the bolts holding them together. Improved flexibility and reduced heat transfer were simultaneously achieved by separating the side-bolt bosses from the trochoidal wall, and housings made in this way proved completely resistant to thermal fatigue.
-----------------------------------
OK, got it? Thermal stress is causing the cracking.
Remember, between Mercedes, Curtis Wright and Mazda technologies we think of as new or cutting edge like aluminum rotors, ceramic apex seals, direct injection, ceramet wear coatings, side exhaust ports, combo ports, "stud kits", etc were all evaluated in the 50s and 60s...
Was this directed at me??? I asked about issues because he was running my studs, thanks for the lesson though.
Last edited by Zero R; 08-19-09 at 11:14 AM.
08-19-09, 10:36 AM
#42
08-19-09, 12:16 PM
#43
Was this directed at me??? I asked about issues because he was running my studs, thanks for the lesson though.
I was replying to your
"??issues??"
when I wrote
Issues like if you don't slowly bring the motor up to temp you will crack your side housings from conducting rotor housing heat into the studs and expanding the studs in the cooler, less conductive, brittle cast iron side housings as Mazda found in the 60s when they tried it.
When I wrote in the next paragraph
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
It was directed at all of us reading because the language use in that quote does not immediately make it clear that they mean Mazda tried close fitting bolts and the went to the current loose fitting bolts in coolant to solve a thermal fatigue issue.
I am just learning this stuff and found a nugget of info in a book and was trying to share and saw we were all still trying to figure out why studs would cause cracking.
I was replying to your
"??issues??"
when I wrote
Issues like if you don't slowly bring the motor up to temp you will crack your side housings from conducting rotor housing heat into the studs and expanding the studs in the cooler, less conductive, brittle cast iron side housings as Mazda found in the 60s when they tried it.
When I wrote in the next paragraph
My post on the 1st page repeated below. Everyone needs to read the italics a couple of times if they don't get an "a ha" moment right away..
It was directed at all of us reading because the language use in that quote does not immediately make it clear that they mean Mazda tried close fitting bolts and the went to the current loose fitting bolts in coolant to solve a thermal fatigue issue.
I am just learning this stuff and found a nugget of info in a book and was trying to share and saw we were all still trying to figure out why studs would cause cracking.
08-19-09, 12:25 PM
#44
The only problem with your theory is that Mazda had different intentions than we do
It is not a theory, I am just relating how Mazda found close fitting bolts caused cracking and that is why they changed if for the production (and race) engines.
I understand that thermal fatique resistance may be less important to some than keeping an engine together for 1320 feet while running with detonation combustion events.
V8 drag racers fill their engines coolant passages with cement to improve strength a little bit but this would obviously cause thermal fatique issues in most other situations.
I am just trying to disseminate some knowlege to rotor heads here gained at Mazda's expense.
It is not a theory, I am just relating how Mazda found close fitting bolts caused cracking and that is why they changed if for the production (and race) engines.
I understand that thermal fatique resistance may be less important to some than keeping an engine together for 1320 feet while running with detonation combustion events.
V8 drag racers fill their engines coolant passages with cement to improve strength a little bit but this would obviously cause thermal fatique issues in most other situations.
I am just trying to disseminate some knowlege to rotor heads here gained at Mazda's expense.
08-21-09, 03:54 AM
#45
Alot of theory on this site thats for sure,to many engineers with way to many big words
Both doweling and studding will work.
Its where you put them that makes the difference and what can be done to make a block stong would put all of the engineers theories to shame
Just do what you want to especialy with up to 800hp.
After that things need to be good
Both doweling and studding will work.
Its where you put them that makes the difference and what can be done to make a block stong would put all of the engineers theories to shame
Just do what you want to especialy with up to 800hp.
After that things need to be good
08-24-09, 10:03 AM
#48
I didn't call him an idiot. Not at all. He may be a very smart guy and kudos if he has some really nice cars. That's awesome. Using the term "too many engineers with too many big words" however implies that engineers aren't smart. Just remember it's not always the smart guy with the fastest car. Money along with someone else's knowledge goes a long way too.
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Frisky Arab
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