ceramic apex seals

[Grizzly]

Ceramics are certainly the way forard in not only the rotary engine but in other applications as well, for instance turbine blades.  Ceramics have superb heat abilities in that they are really not affected by heat and can withstand extreme temperatures.  brillient in a rotary engine.  The only major problem with them is that when they go....they go and I am just wondering how much more damage they might cause compared to that of the OEM seal.  Ceramics are widely used in aero engines because they do not expand and tighter tolerances can be allowed in engine building.  Ceramic can shatter quite cataspropically as they are affected by harsh hot to cold temperatures and visa versa.  Temperatures in an aero engine reach 2000 deg C but with blade cooling via air holes in the blades this comes down to an acceptable 800.

does anyone know what the combustion temps are in the rotary?? ie actually in the combustion chamber and not exhaust temps as these can be quite different.

yes Ceramics are realy good there are Lots of reasons why (Self Lube Propertys,Weight,How they handle heat as you say very little change in size to big change in temp). But the down side is they are Realy easy to Brake (not in high Boost or on a Track but if they Bind or catch some thing) they are So hard they Shatter into Small Fragments that Score the hell out of Anything Moving, the easyest way of Blowing a Ceramic is the Wrong Tolerance!! I belive the Cheaper one also suffer from Manufacturing Fractures  that are you can\'t see unless they are X-Ray\'d. Thats why they are Expencive :yes

[Grizzly]

what amazes me about the rotary is the many points of view on every aspect.

For this reason the rx7 will never ever die!

P.S i should never have joined that wine club!!

Yep, There are so many opinions out there and so many ways to do the Same Job. Its Great!! :yes

[pdtaylor18]

did you know that to get as pure a metal as possible free from microscopic cracks/flaws that they grow the metal, more so turbine blades. In this way the particals are all flowing in one direction which makes it stronger and hopefully flaw free and therefore fatigue which sets in after time will be eliminated.  Down side is the cost as they are somewhere in the region of £500 a blade.

[Timrxmotors]

I did have Iannetti ceramic seals in my 12A once upon a time.Housings were used,but in top condition.Compression when built was 5 bar,and after 1600 miles had fallen to 4.5 bar.Sealing was crap.Under load in 3rd gear engine would detonate because of leakage.I never went up the strip,it would have blown up.
The stock 3mm seals I use seal far better,giving much more power.The bottom edges of the seal have a different taper on each side to allow for proper sealing,and also has the correct radius on the top.Ceramics have no tapers,and the radius on top is different,i.e. wrong.
I have no problem making lots of power at very high rpm with stock seals,and if I do damage them,by detonation or warping,they are much much cheaper to replace.

[stuart wizy]

I need to know what the nominal size is for the 3mm slot for using ceramic tips.
all 2mm and 3mm steal tips are 4 thou under the nominal size and the slot is milled 2mm or 3mm dead size. I measured the standard 2mm seals and there 1.92mm thick - 3mm tips are 2.92mm thick so the tip thickness dictates the clearence.
so are ceramics made the same thickness or slightly wider because they dont expand? ie 1.95mm or 2.95mm?
ive got a funny fealing my slots are going to be to sloppy for ceramics because one of them with a 3mm tip in , u can get a 6 thou feeler down the side.
all the slots are dead central to the corner seal bores and dont bind on any of the solid 3mm corner seals.

[shaunwil]

yes Ceramics are realy good there are Lots of reasons why (Self Lube Propertys,Weight,How they handle heat as you say very little change in size to big change in temp). But the down side is they are Realy easy to Brake (not in high Boost or on a Track but if they Bind or catch some thing) they are So hard they Shatter into Small Fragments that Score the hell out of Anything Moving, the easyest way of Blowing a Ceramic is the Wrong Tolerance!! I belive the Cheaper one also suffer from Manufacturing Fractures  that are you can\'t see unless they are X-Ray\'d. Thats why they are Expencive :yes

Ceramic technology is moving along quite alot in the machining sector, they cerment them with high temp metals to improve their shock resistance properties. I\'ve watch ceramics cut metals at amazing speeds and loads dry, something even a carbide insert would struggle with or just burn up. With ceramics it is the shock loading that cracks the ceramic and the crack travels along the meterial at the speed of sound.

Standard ceramic grooving inserts arnt keep and they are mass produced !

Material technology is coming along and one day they will be a very good choice !

Shaun

[Grizzly]

I did have Iannetti ceramic seals in my 12A once upon a time.Housings were used,but in top condition.Compression when built was 5 bar,and after 1600 miles had fallen to 4.5 bar.Sealing was crap.Under load in 3rd gear engine would detonate because of leakage.I never went up the strip,it would have blown up.
The stock 3mm seals I use seal far better,giving much more power.The bottom edges of the seal have a different taper on each side to allow for proper sealing,and also has the correct radius on the top.Ceramics have no tapers,and the radius on top is different,i.e. wrong.
I have no problem making lots of power at very high rpm with stock seals,and if I do damage them,by detonation or warping,they are much much cheaper to replace.

Yeh this is quite common, but thre are Tuners that claim 8 bar on Ceramics?(Might be on NRS\'s though)  But tbh i can\'t see that on any 1 pc seal?

Still rate stockers

[Warthog]

Interestig thread boys, keep it up.:Thumbs-up

[88GT-R]

I have used NRS 3mm, and felt the benifit. Unbelievable engine acceleration, all the way through 8 grand. Unfortunately one cracked, after 2000 miles form forign debris. Back on steels at the mo, until next strip down.
BTW, cost around 900 bucks for complete set of NRS 3mm seals and springs.

John

[Grizzly]

There are alot of people say the NRS are better than the Iannetti\'s, if you go of Compresion/Price then they would look better.

[stuart wizy]

im in 2 minds what to do now! ceramics or steals
dont forget this engine im building has got to be proved with the custom inlet manifold and 50 mm runners and much bigger inlet ports, so spending big bucks on ceramics could be a mistake until its been proved, I already have the 3mm atkins, but I will be gutted if it wont rev with the 3mm steals fitted when on the dyno.
On the other hand going of what tims saying with his experience,  im in two minds!
Ive seen tim run his  12A at very high rpm with good success, in the tens now I believe , well done tim by the way on a 10 second run:Thumbsup!

the motor at the moment stands me at hardly anything to be honest only tips and gasket sets cause ive done all the porting and millng, the housings are good seconds from tim so maybe I should build it with my 3mm atkins, test it , see how it makes its power,  wait till it pops and then go for brand new rotor housings with 3mm ceramics on the 2nd build when I have an idea of what its capable of.
I would love to build the motor with that 2 piece aussie ecentric shaft with the roller bearing that suports the shaft in the middle plate, surely with support in the middle of the shaft you could run much higher revs without the chatter or runout of the shaft.
I used to turn big shafts and spindles using roller steadys to suport them in the areas being cut , same principle, massive diference to run out and chatter on any size dia shaft.

[stuart wizy]

something else im not to sure of is springs to use for 3mm steals,
Ive just got the outer springs (long ones), should i use the inner spring to?
I read somewhere a while ago to only use outer springs with 3mm , not as much spring force is required cause of extra centrifugal force with extra weight of 3mm tips.
what springs do you use tim mate??

[88GT-R]

Tim\'s seals are machined on the inner edge to reduce help reduce their weight, so his spring requirements may be different to what is normaly used.

[stuart wizy]

do you mean the opposit edge to the rad ie the bottom of the tip, would this not cause them to bend like a banana!
normaly when milling or grinding anything thin, u take equal amounts of top and bottom (keep turing it over) to stop bending, do they grind across the top of the rad side  when the tip is roughed out on the bottom u mean? to keep flat.
thanks for the info by the way mate:Thumbs-up

[88GT-R]

Speak to Tim about the details.....not my place.