I have recently met an engineer who accidently came across an aluminum alloy that is self lubricating, disapates heat and will never wear out. He has used this alloy to make his own brake rotors and has used these rotors for ten years on his daily driven car without changing brake pads and they have yet to wear out.

I talked to him about possibly making apex seals and he said that it would be no problem to cast the seals out of this aluminum alloy, but I am wondering if this alloy is too hard and could possibly "eat" the rotor housing away.

I am planning to get him to cast me a few sets so I can build a turbo motor and an N/A motor just so I can try these seals to see how they stand up.



Any input on this subject would help.



Thanks

Joe

How are you going to obtain the Sealing Surface finish? Casting IS NOT smooth enough. If this material is so hard, how will you obtain the final dimesional tolerances required?

no doubt^^ what he said....



Machine a rough blank, lap it, then polish it to final tolerance required. Know what the material is?? Sounds like ubotanium...LOL

it might work for side seals, but they dont really wear anyways

Metal Matrix Aluminum? aka Duralcan which is a trademark licenced to Alcan. That stuff is super hard, in billet form if you were to make anything it needs to be water jet cut as it dulls any metal/carbon blade in a few passes. I think if you were to try to make those into seals you would kill the metal ring that the rotor housings have. I doubt you could get it to work as the thermal expansion may be greatly different than what steel alloy seals are made from.

I'd question lubrication specs and expansion specs.

These are the two most important specs for apex seals.





-Ted

Good Luck with that. https://www.nopistons.com/forums/pub...#>/biggrin.png

This alloy sounds good for housings/plates material

I've never heard of a self-lubricating Al material.

Al by itself is pretty "abrasive" and galls with most irons and steels.

I'd be interested if this is for real or some fantasy?





-Ted

I will have to talk to him again about this, but he said that this aluminum alloy is inprenated with graphite, which makes it hard. As for it the sealing surface finish, yes you are right casting does make a very rough surface, so what he was planning on doing was to cast a sheet of this material about 3-4mm thick and then machine both sides down to 2mm (the width of normal apex seals) so that it is avery smooth surface. Once we have a sheet of 2mm metal, use a cnc machine to cut out the shape of the apex seal and then round the top sealing surface.



Please tell me if any of what I just wrote made any sense. I'm not very good at explaning things. https://www.nopistons.com/forums/pub..._DIR#>/sad.png



Thanks

You just described carbon apex seals.

Im doing my masters in mechanical engineering, the project is material selection and testing for piston seals and chamber coatings in a pivotal engine (rectangular pivoting piston, 2 stroke) one of the seal materials that we are using is kind of an Al alloy, it is called CE7, it is a low expansion aluminium silicon alloy with approx 70% silicon, this material works well in our application but I dont think it would hold up to the temperatures in a rotor, also you would have to look carefully at the stiffness of the material at operating temperatures to make sure that it would not bend and catch on the exhaust port. Interestingly the mazda apex seals appear to have very little carbon/graphite on the wear/seal surface.

the problem with rotary seals is that the seal must withstand the brunt of all the forces during a combustion sequence, wehre as the piston ring seals are protected essetially since they are not in the path.



Mazda probably uses some sort of steel alloy with low conc of carbon. As carbon increases the brittleness of metals as it's concentration goes up. But it does make it harder.

do you guys really think you can make a better seal then mazda did on your own?

you must have a lot of money, good luck

it's cast, the lowest grade of cast iron has more carbon content then the highest carbon steel. the hardning of the steels is what makes it that bittle if you were to temper it it should work alright, you aneal the end of a punch and it takes the same if not more abuse.

if some one has enough money, time. and people to help any thing is posable.... and i wouldnt waste my time on casting, i would just make a mold and if the mold is all in spec every thing should be close or if not just good enough as it is.... but i dont think any of us do thes kind of things as a living... but i would also think about using an e.d.m. more then machining thim if its realy all that hard of a aloy



but other then that, its worth a try if your wanting to put the time and money into it.... good luch

yeah EDM is definately the way to go.

There are definitly plenty of materials out there that would probably be better than the mazda seals, just that there does not seem to be many people experimenting with it. When I get round to putting my motor together I think I will make my own seals purely for cost if I can find a block of something useful ( free EDM wire cutting at the university)

Do you have any idea just how many alloys mazda has tested over the years?

Aluminum melts at around 1000F. And because of the nature of the beast, mechanical properties are greatly diminished even at around 400oC and starts to soften at 700F-800F.



Choosing a suitable material for them apex seals is one thing.. then there is the question of manufacturing them. Manufacturing process will have to be closely controlled to get a homogeneous seal with no residual stresses(or a uniform state of). There's also a question of cost, performance characteristics like wear, natural frequency etc etc.



I'm not saying that a new high quality seal can be made.. just that there is a whole lot more to the material selection that alot of people think.

' just finished the engineering-rich "The Wankel Rotary Engine, a history" by John Hege...



upon reading this thread and recomposing myself --- ten year brake pads and "no problem" apex seals--- i recovered enough to give you some helpful advice.



get your self a good patent attorney and call 1 800 mazda.



if you can do something better than their materials engineering company i am sure they would be delighted to pay you guys the big bucks.



just don't spend the money before you see the check. i do genuinely respect you optimism however.



howard coleman

No but im sure they tested a few considering that they were using a chilling process in production that was not even comonly availably in laboratories at the time.



Having said this though from looking at the microstructure of the mazda 3pc seal there is definitly potential to have a material with similar performance (wear and friction) but be much tougher



The black areas are graphite flakes, these being the main reason for the seals to being brittle. This graphite does not have anything to do with reducing friction or wear of the seal but it is likely that it helps prevent galling

Self lubricating and brake rotor don't belong in the same paragraph? On brake pads, they call it friction material for a reason.

Has anyone ever made or tried to make titanium apex seals????

bad idea mike I hate Ti the only good Ti is Thai food. Titainum sucks everybody, get over it. use carbon fiber https://www.nopistons.com/forums/pub...#>/biggrin.png



Oh, by the way, CE7 is garbage, JE tried making pistons out of it, the wrist pin would pull out the bottom of the piston. it would stick in the bores, even with a teflon coating on the skirts. TOOO much expansion properties and holding the proper piston to wall tolerances was damn near impossible without comprimising (sp) ring end gap/seal

titanium is not the all mighty metal that everyone thinks of. Titanium is not good in sheer along it's matrix.



Where it's at is still ceramic in my opinion. I'm not familar with it so I can't comment much, but if you can find a way to manufacture it cheaply then you'd be rich.

When you say too much expansion properties Im assuming that you mean the thermal expansion is too low, its about half that of a high silicone piston alloy, its is also alot weaker (ultimate tensile strength). Sticking to bores is strange though. I have been using this as a piston seal material with no problems like that, do you know what sort of bores they were running them in?.



As for Ti I'm also not that fond of it but did manage to get it to work well in the engine that I have been involved with the development of the biggest advantage was the reduction in weight by abouy 40% over a steel seal, the problem was that the seal would destroy the side plates and chamber coatings once it hard worn to a certain degree, also the manufacturing costs were high

they always scuffed up bad on the skirts cheese. We tried Nikasil, Durasil, good ol' iron bores in a pinto ff2000 block, everything. I stick with what works. I'm not an engineer, im an engine builder. I've seen stock seals hold up to 2 seasons of ENDURO (5-24 hours) racing with a 20B turbo in the back of a GTP car (vintage) about avg 15psi boost bursts of 25.

The main motivation for making my own seals is primarily cost, the second reason that I don't think mazda made 1pce 3mm seals that were not carbon.



Interesting about the CE7 though slightly different applications/operating conditions I guess. It won't work for apex seals only bought it up because it is a slightly exotic material along the lines of the Al graphite that was first mentioned.

This is a picture of the piston with the CE7 seals fitted. It is being run on various plasma sprayed coatings that are used in automotive engines.

why would you want 1piece seals? the whole point of the 2 peice seal, is so it can accomidate the seals change in length with heating/cooling. they stopped using a 1peice in the production cars because they sucked on the street.

Basically so they will be slightly stiffer and not fall out of the ports that I am in the process of making, only 3mm because the rotor tips are slightly burred so no longer usefull for 2mm seals.

Why would it matter if it fell out of not?

Are you going to design the corner seals too to not fall out?

The current 2-piece (2mm) Mazda OEM apex seal cannot fall out?





-Ted

You keep saying your motovation is cost. Wolnt you end up spending just as much on something that might not even work?

The corner seals wont fall out, I'm looking at a periferal port design and am more concerned about the seals bowing out and catching on the port. As for the cost they will basically be free. I am not just going go grab a block of metal and cut out some seals I have been doing resaerch and testing in this area for a long time now. The mazda seals do work well but that doesn't mean that they are the best for all applications

make them and i'll put them in an engine and torture test it https://www.nopistons.com/forums/pub...#>/biggrin.png

yeah, use my engine dyno



Go ahead and experiment cheese i have no problem with that, the problem is that you have no idea what you are getting yourself into, like all mech engieers that try to play with motors.

Its not just motors its any thing that we get our hands on

seriously, dont do a thesis on a motor

Its not really the motor just the compresion seals and chamber coatings so what I am doing is bench testing material couples with a tribometer to get friction and wear rate data and than characterising the materials using optical and electron microscopy.



On Thursday I tested a piece of a mazda apex seal on the best chamber coating that I have and found the seal wore faster than the best uncoated seal material that I have which itself does not last very long in the engine (25-40 hours @ 3000rpm 10 kw) which tends to confirm my theory that it is not a material problem but a lubrication or a seal loading problem with the engine which is out of the scope of my work.

ok, as long as you are just doing a "wear rate project" thats cool. Kepp us posted on further findings, formula mazda and lots of e-prod guys would love a set of seal that lasted 2-3 seasons instead of one!





PS us poor piston guys rebuild 1-2 times a season.