"Head Gasket" For Rotaries
03-26-07, 10:58 AM
#1
"Head Gasket" For Rotaries
Here is my thought; design a gasket similar to a head gasket used on piston motors. Instead of using the coolant 0-rings, this would overlay the entire area around the iron housing face and have cut outs for all the coolant passages, dowl pins, etc. Basically if you traced the sides of the irons and rotor housings thats what it would look like. It would be either copper or mls (multi-layer steel). I would think something like with would be alot more durable than the fragile coolant o-rings. The only issue I can forsee is the gasket would have to be very thin as not to space out the housings too much and allow too much space between the rotor and housings. Why or why not? Discuss.
03-26-07, 01:01 PM
#3
I think it would take alot of machine work to cut the housings down enough to be able to put these gaskets. Basically you would probably have to cut/shave the housings down to where the oring usually sits. Then you could make a gasket that was as thick as the orings. Probably would work pretty well but would be a ton of work. If anyone wants to manufacture these and machine the housings the price would be crazy.
Last edited by hondahater; 03-26-07 at 01:09 PM.
03-26-07, 01:52 PM
#4
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waste of time, the O rings work fine for a long time as long as the engine isn't overheated.
Much better to focus your attention and money to preventing engine overheat, and warning you if an overheat is pending with an accurate aftermarket gauge and possibly warning light, or adjust your tuning (aftermarket ecm) so the the engine goes so pig rich above a threshold (say 220 F) that the engine basicly cannot run, if your really paranoid you could even use a temp switch in conjunction with an engine kill switch.
Much better to focus your attention and money to preventing engine overheat, and warning you if an overheat is pending with an accurate aftermarket gauge and possibly warning light, or adjust your tuning (aftermarket ecm) so the the engine goes so pig rich above a threshold (say 220 F) that the engine basicly cannot run, if your really paranoid you could even use a temp switch in conjunction with an engine kill switch.
03-26-07, 02:02 PM
#5
I agree partially. Its just an idea. I rebuild so many of these motors that things just pop into my head as I'm assembling them. I have seen many coolant o-rings let go without even overheating the car once the engine gets to around 50k miles.
03-26-07, 02:15 PM
#6
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Originally Posted by Rotary Experiment Seven
I agree partially. Its just an idea. I rebuild so many of these motors that things just pop into my head as I'm assembling them. I have seen many coolant o-rings let go without even overheating the car once the engine gets to around 50k miles.
most of us guys who would spend the money that it would cost to get this to work are guys who would be beyond happy to get 50k out of a motor... I'd be happy if i can get a motor to 10k miles lol
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03-26-07, 02:35 PM
#8
03-28-07, 02:54 PM
#10
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Originally Posted by peejay
Serious piston engines use O-rings instead of gaskets. Why downgrade?
03-28-07, 03:16 PM
#12
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The head gasket idea won't work in a rotary for a few reasons.
The tolerance between the irons and housings; they must mate. A gasket of any type must yeild to seal. The odds of getting both gaskets to yeild an exact uniform amount around the entire housing circumference is nearly nil. Add in the fact that you're torquing the entire "sandwich" of the motor at once. One gasket could yeild more than another etc and you're depending on 4 of them behaving exactly alike as you cinch each one down with the same set of bolts. Your tolerances would compound and you couldn't properly maintain them
You'd be using the torque setting of each bolt to attempt to assure you that 4 layers of gasket are properly mated. Nearly impossible. The distance between the irons wouldn't be properly maintained. O-rings don't have this issue because they yeild and allow the housings and irons to mate rather than fitting in between the housing and iron. In this way the o-ring gaskets have nothing to do with maintaining engine tolerances and do nothing but seal. Ideal in this case.
The rotary is a sandwich. Imagine stacking all of those gaskets and even if they did seal properly imagine trying to maintain something like eccentric shaft endplay.
A head gasket's job isn't nearly as difficult. Thickness isn't a major concern as all it does is vary compression ratio and it can't change the actual engine geometry. There's only a single layer to be clamped by the head bolts and that area is actually quite small compared to what a rotary would require; rotary parts would have to be massively stiff (overbuilt and heavy) to torque properly.
The tolerance between the irons and housings; they must mate. A gasket of any type must yeild to seal. The odds of getting both gaskets to yeild an exact uniform amount around the entire housing circumference is nearly nil. Add in the fact that you're torquing the entire "sandwich" of the motor at once. One gasket could yeild more than another etc and you're depending on 4 of them behaving exactly alike as you cinch each one down with the same set of bolts. Your tolerances would compound and you couldn't properly maintain them
You'd be using the torque setting of each bolt to attempt to assure you that 4 layers of gasket are properly mated. Nearly impossible. The distance between the irons wouldn't be properly maintained. O-rings don't have this issue because they yeild and allow the housings and irons to mate rather than fitting in between the housing and iron. In this way the o-ring gaskets have nothing to do with maintaining engine tolerances and do nothing but seal. Ideal in this case.
The rotary is a sandwich. Imagine stacking all of those gaskets and even if they did seal properly imagine trying to maintain something like eccentric shaft endplay.
A head gasket's job isn't nearly as difficult. Thickness isn't a major concern as all it does is vary compression ratio and it can't change the actual engine geometry. There's only a single layer to be clamped by the head bolts and that area is actually quite small compared to what a rotary would require; rotary parts would have to be massively stiff (overbuilt and heavy) to torque properly.
03-28-07, 06:55 PM
#14
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Originally Posted by DamonB
Serious piston engines use no gaskets of any kind! The tolerances are so tight the parts are merely bolted together.
IIRC they also leak like a sieve anyway.
Now, on the other hand, let's look at the Ford Boss 429, which was designed for two things: Dominating NASCAR, and dominating Top Fuel. To that end, even the street versions (there were two) used O-rings instead of head gaskets. Coolant leaks were unlikely because you could get much more compression from an O-ring than a gasket, since the only part that crushes is the O-ring and not an entire gasket surface (even embossed steel type), and the combustion O-rings were V-shaped in cross section, to seal harder under pressure.
SCE Titan head gaskets are the closest thing you can get to this type of sealing with minimal (no) machining, but they are *not* cheap. IIRC around $400 a pair. But, even the SCE doesn't offer the fault-tolerance that you can get with an O-ringed system, where you can direct any possible lost combustion gases safely away from the cooling or oil passages and out of the head junction.
Last edited by peejay; 03-28-07 at 07:04 PM.
03-28-07, 07:18 PM
#15
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Can't edit the post again. I forgot two important points.
First, the main reason why F1 don't use gaskets is because they need to hold piston to head tolerances tighter than they could reasonably assume to get with the added variable of a crushable gasket. Last I remember, they also preheated the oil and coolant before trying to "cold"-start an engine, so there is minimal thermal expansion, allowing them to get away with using no sealing methods other than "ultra precise machining".
Second, please don't infer that I think the Boss '9 is the be-all end-all performance engine. It does kick *** but it has some glaring faults, not the least of which is being relatively unpopular. However, it *was* the first example that came to mind, and the only production engine that I could think of. Gasketless O-ringing is normally something only done for one-offs or supremely polished racing turds.
- Pete (supremely polished racing turds... SPRT... coincidence? i think not!)
First, the main reason why F1 don't use gaskets is because they need to hold piston to head tolerances tighter than they could reasonably assume to get with the added variable of a crushable gasket. Last I remember, they also preheated the oil and coolant before trying to "cold"-start an engine, so there is minimal thermal expansion, allowing them to get away with using no sealing methods other than "ultra precise machining".
Second, please don't infer that I think the Boss '9 is the be-all end-all performance engine. It does kick *** but it has some glaring faults, not the least of which is being relatively unpopular. However, it *was* the first example that came to mind, and the only production engine that I could think of. Gasketless O-ringing is normally something only done for one-offs or supremely polished racing turds.
- Pete (supremely polished racing turds... SPRT... coincidence? i think not!)
03-31-07, 01:53 PM
#16
I don't think a gasket would work well for reasons listed above. but I do believe that a metal ring, similar to the inner rings on a head gasket, could be made for the rotary. You'd have to mock up a few housings and tension them down to figure out the crush rate, and make a metal seal suitable to accept that crush rate.
It'd have to crush enough to let the housings seat to each other without busting open a coolant jacket wall casting, yet not crush so much as to allow a leak. IT would probably need to start off with a square cross section, just like the stock seals.
And if you say that the metal won't seal well to metal, explain how the crush washers on banjo fittings work, or how the rx-8 metal front cover gaskets work, or how copper head gaskets on piston engines work.
I am very surprised no one has come up with a metal inner o-ring, at very least. You wouldnt really need an outer...
It'd have to crush enough to let the housings seat to each other without busting open a coolant jacket wall casting, yet not crush so much as to allow a leak. IT would probably need to start off with a square cross section, just like the stock seals.
And if you say that the metal won't seal well to metal, explain how the crush washers on banjo fittings work, or how the rx-8 metal front cover gaskets work, or how copper head gaskets on piston engines work.
I am very surprised no one has come up with a metal inner o-ring, at very least. You wouldnt really need an outer...
03-31-07, 03:54 PM
#17
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I have heard of some type of metal ring that is pressed into a head and a small notch(half the size of the ring) is milled into the block, and when they are bolted together make the best seal possible.
04-01-07, 01:58 PM
#19
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Originally Posted by RotaryResurrection
And if you say that the metal won't seal well to metal, explain how the crush washers on banjo fittings work, or how the rx-8 metal front cover gaskets work, or how copper head gaskets on piston engines work.
Steel head and intake gaskets are embossed to get the surface area down, for a better clamp. Even then, they needed rather high torque loads and close bolt spacing to work. For example, the steel intake gaskets for an AMC V8 call for 45 ft-lb of torque. and I forget how many botls there are. My old 429 only called for 23ft-lb but there were something like 16 or 20 bolts. The last of the small-block Chevies (Vortec truck engines) used rubber O-rings in a steel or plastic holder, had only eight manifold bolts, and the final torque is only 11 ft-lb.
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