Hey, i was just wondering if anyone has any ideas on reshaping the combustion chambers? i was thinking you may be able to build them back up, but not sure what material you could use to weld to the rotor like that. anyone with more experience got some input?

 

that is something i always wanted to try..spray welding is maybe best method...but i always worried about warpage

 

yeah, warping the rotor had crossed my mind, but i don' t think that it would warp a rotor. i think they have a good shape for something like that, not thin or flat, big and bulky. I'd really like to figure this out though, i think some really awesome things could be done with the engine if there was a way to do this.

 

Saw a junk rotor in half sometime. It's thinner than you think. Distortion from welding up the entire combustion chamber would be a big issue. Even with preheating. Now, some welding in the combustion chamber would be OK but, where the line is drawn. I don't know. The more welding, the more distortion or chance there of.

I've welded on rotors just to see if it could be done. They weld fairly nicely with a TIG.

I think a more productive route might be taking S5 high comp rotors and machining some stock out of the bathtub. One could never get compression as low as a turbo rotor but weight could come off and compression reduced from 9.7. With other lightening methods, it could be interesting.

 

i want the compression higher. maybe a recasting would be a better idea. then the thickness wouldn't be an issue.

 

I think that cerment coatings can be applied to raise the compression by filling that bathtub. I have not called them but one of my friends has and he told me that they could do it. Might want to check it out.

I also spoke to Jim M., the owner of Racing beat on this subject and he said that he has done several dyno tests with higher compression rotors vs lower and told me that the higher compression rotors did not make anymore peak power than the lower comp rotors but that the higher compression rotors made more power and torque at lower rpm range and was one of the reasons the renesis engine uses the higher compression rotors to gain the needed lower and mid range power.

I have heard many mixed reviews on the subject of the 9.7 s5 rotors vs the renesis rotors. I sure am not seeing many high horsepower numbers with the renesis rotors in a N/A motor though.

 

you should read the book "rotary engine" its on the web, its mazda's book, and they have graphs of the power difference between the different compression ratio's.

there is an SAE paper (something 84 recent tech, also on the web) that shows the power difference between the different combustion chamber SHAPES.

as you raise the compression the shape gets weirder, which is not really good for power.

 

another consern of mine has to do with too much compression causing uncontrollable detonation sisues, which will hamper your tunnign ability and limit your scale of hp ranges...I think it is easier to just go with rx8 rotors or 9.7 S5 rotors...anythign more may just be trying to reinvent the wheel so to speak..
I know John Deeere had a diesle rotary before Mazda bought it from them but i doubt they ran huge compression ratios as they only used it for a generator or pump of some sort..and it ran on both gas fuel and diesle once started up or something like that...not to sure if that is correct but i read this somewhere.....


henry

 

the reason i wanna fill it in, is so that i can reshape the CC from scratch. i had a good idea for a combustion chamber shape that would promote rotation of the engine, instead of just filling it in until the compression was where i wanted it. The other reason is because i need really high compression, like diesel high compression. i'm trying to get to atleast that 16.5:1 CR, or higher, so i don't need glow-plugs. my biggest concern is keeping the seals intact.

 

there is a engineering company in ohio here ..i was talking to one of the key engineers and they are in the process of designing a small one rotor diesel engine for UAV planes.military money...they are looking into all of these possiblities...not sure where they have gotten so far though.
I think you will have to run some very thick apex sels for that kind of compression ..i would consider milling out rotor and run 6mm like old school 12a used to use.....
alos does your combustion chamber design incoporate a kind of figure 8 design..creatin swish as the compression stroke takes place?
thus promoting better flame propagation? if you say yes to this then just look at early twin distributor style 12a rotors..they did all of this with very thick 6 mm seals....high compression...but over time what have they gone to? of course they are using thinnner seals now just for efficiency and low drag and fule mileage.....
you wont have these concerns if your looking to create a diesel......

 

my thoughts were more of a triangular shape actually, but a figure-8 is an idea to think about also. my idea was more to favor the combustion chamber a bit to one side so that combustion would have more leverage to turn the rotor.

 

a triangular shape may actually cause more of a heat sink than a combustion area...flame will move into the tighter angle with so much force it may create a very hot corner...tht is why most combustion chamber designs that work are well rounded shapes..to avoid hot points...
a figure eight will enable something like a simiese combustion chamber thus promoting almost 2 flame fronts , HOWEVER, if your designed is flawed at all you can end up with detonation due to falme collision..

henry

 

all very valid points. the idea behind my triangular design was the same reason you were against it. I wanted all the energy pushed into a smaller area, and i wanted it to be closer to the edge of the apex. Maybe keeping a similar design to the stock shape, but moving it and making it smaller would be more the key. I was also thinking that a wedge-like bottom to the CC would be a better idea, to give a more efficient, leveraged push on the rotor face. if someone can give me an idea for safely filling in this combustion chambers, i would love to try as many designs as we can come up with. i'm just using my old 12a, i already have another running engine in my car, no hurry, i just wanna see how well it works and how much potential could be hiding.

 

modify that triangle to a tear drop with a deep end on the drop side...this will create a pocket for expanded gasses to move towards..the thin edge of the tear drop (lets call it trailing edge)
is for that tight compression your wanting..picture a water wheel withthe bucket catching the energy ofthe flame front....i see it in my mind, not sure if i put it down here as i see it

henry

 

i like it. so, next obstacle is the seal problem. i am gonna take a look at some of the materials being used now in the aftermarket.

 

Sounds like you are describing an LDR (leading deep recess) rotor like Mazda already made for the 12A.

Current MDR (medium deep recess) design


LDR design

 

yep, something similar to that.

 

read the book, they already did the research and put it in a book

 

i was thinking of that lower one but more drastic at the shallow end..BUT i did tell him that it has all been done already...tried and tried , till perfection...however he is looking for more compression so it s his dream guys

 

Well you can get a company that does plasma metal spraying to build up the rotor faces and machine them back down to spec, but it will be expen$ive.

Looks like JHB has some development going on with rotors.

 

thanks, i appreciate all the input and support. i understand that people have tried diesel rotary engines, i understand that people have tried different shapes in the combustion chambers, and a lot of other options all very similar to what i wanna do. But, there isn't a high compression, direct injection rotary engine out there yet, and i think it would be badass. I'm moving the next week, but after that i'm gonna bring up the engine i'm gonna use for this project and tear it down, and see what can be done with the rotors.

 

Oh, for direct injection diesel rotaries look into the Curtis Wright engines developed in the '60s.

They did lots of research on having the spark plug and injector placement in the combustion chamber and injection timing and the rotor recess.

I believe you will also have to do spark ignition if using the Mazda geometry.

It is a bummer that the two ways to get low rpm torque on a rotary are at odds with eachother ie the higher the eccentric shaft offset the lower the theoretical compression ratio.

The 16X will have a lower theoretical compression ratio than 13B, but don't know if that will translate into lower manufactured CR because so many more factors are involved into rotor recess design.

It would be nice if 16X was more turbo friendly though

The book you want for research is The Wankel Engine design development applications by Jan P. Norbye 1971

 

awesome, thanks, i will definitely check it out. i don't want to use spark ignition at all, hence the need for much higher compression. i would prefer to not need glo-plugs either. i will check out that book though and maybe it can fill me in on some of the missing info. and "why" questions that i have.

 

they have diesel rotaries now... not sure about the details though

 

yeah, there were some great examples given of some great diesel rotary options that have been done over the years. some of them had similar ideas, but none of them seemed to put it all together the way i want to do it. if i can get it to work the way i want it, it would be a pretty simple engine to run. Getting to that point will be a long road though.