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Increasing displacement of rotary engine - CNC talk
It's been a couple years since I've seen an entirely machined aluminum blocks floating on the web.
Long story short, one of my friends is building an exceptional, high end CNC machine with 25hp servo motor, 4D, and top of the line linear bearing on every axis to handle toughest of tough jobs with utmost precision in the micro-inch range. Workspace is big enough to fit an entire engine block.
I floated the idea of making rotor housings with BIGGER displacement, replacement rotor out of exotic alloy, 20b parts, 23b parts?, 26b parts, aluminum center plates with reinforced steel sides, 300m e-shafts, etc. He is very interested in doing this. He has CNC experience in the past.
Is there any CAD drawing of 20b center section, e-shaft, rotors, and rotor housings floating around? If not, can someone chime in on how we should approach a complicated piece like a center section and the rotor? The rotor housings look simple enough minus the chrome part which can be done by an aftermarket company.
Ideally, I would want to see a larger displacement option for rotary. 3.0 20b? or even bigger. or at the very least better parts to allow for higher psi rating.
We're not looking to reinvent wheel, just looking to explore a viable way to think forward to increase displacement for our engine.
You could increase rotor width or eccentricity, but everything would be custom. IIRC there are industrial wankel power plants that vary widely in size.
aluminum center plates with reinforced steel sides
If you could even just produce aluminum centers and sides, I'm sure there's a market for them. I'd be interested in them, down the line.
Racing Beat has them, but for $1.5k to $2k a piece.
Custom fab and small productions (eg. out of Australia, I think) charge about the same (+$1k).
If you could beat those prices at all, you'd have some business.
Consider making aluminum housings for the Renesis? I think it'd be more involved, dealing with it's side ports and all, but I don't think anyone makes those at all (to my knowledge.)
Also, you might want to look into the possibility of plasma spraying/thermal spraying the housings (getting the process done at a place that specializes in it.)
I can't even recall seeing anyone post an all aluminum 13b they made/owned here before, but it's been a while.
Billet Inc. ? Home of the World's Fastest Rotary Engines Well these have been around for a while now and are proving to be very good and reliable. My buddy in Florida just got a set of plates and its around $2K plus per plate and the surface plates are replaceable.
if you can supply me accurate CAD file of the desired plate, I'll do it for you for next to nothing--aluminum plate costs $100 and shipping costs $50.
many man hours sound like what we're looking for. always searching for stimulating engineering project. we both like this idea. it's only a hobby, and we're both keeping our daytime jobs.
as for 26b, I do think those multi-rotor e-shafts are stupid expensive. I thought it would be nice to get community together to come up with CAD file so we can start producing them for cheap. You can lathe them out for a few hundred dollars on a 4000series steel. that's for both 3 rotor and 4 rotor shafts. Money is in R&D if you made them to put food on your table. in actuality, balancing and machining cost nothing--material-wise once you already have the CNC lathe and mill. seeing how all we need is to copy the existing product, I can't imagine this being too difficult for us to produce an accurate CAD file for multi-rotor shafts.
if you're building 26b, I would do PP with very thin center sections just to house the bearings and provide passage for the oil/water cooling. you could probably make it pretty compact.
like I said, our ultimate goal is to increase rotary displacement. I do think the easiest way would be to increase rotor width and shaft lobe width, and widen rotor bearing and apex seals.. custom manifold. am I missing anything else?
yea billet inc has been inspirational over the years. I always appreciated how they continue to innovate.
but my point is this... they charge $2000-3000 for front plate and rear plate--each. Another $2000-3000 for the e-shaft. if you want 3 rotor, add another $2500 for center plate. You're at $10k before rotors, rotor housings, seals, and rebuild cost.
in the end, they are nothing but milled out aluminum plates. they cost nothing to make on 4D CNC. if the community can focus on coming together to come up with a quality CAD file for these components or provide faithful copy of the OEM counterpart, we can advance our 30yr old engine technology tremendously. These companies will continue to innovate and can then focus their attention on doing something even more awesome.
I think I have seen some 3D renders of the whole 13b engine recently, but I can't seem to find the exact ones. I believe they weren't made to the true real-life dimensions, though.
Anyway, there is this member in the 2nd Gen builds section that seems to have some sort of 3D modeling done, but I'm not sure if his work was done to real dimensions. Also, I'm not sure if he's willing to share the files and he seems busy with his project, but maybe it's worth PMing him for some leads on CAD: https://www.rx7club.com/build-thread...-build-974831/
If he refuses, perhaps offer to make him housings at-cost?
Originally Posted by John Huijben
If you can't find good CAD files or someone to create them, I think the most inexpensive and quickest way to get rough renders is with 3D scanning.
IIRC, one method I heard of people making a scanning rig is by taking a microwave's turntable and placing an object on it. You rotate the object very slightly and take a pic, turn, take a pic, repeat until 360deg around.
I believe the pictures are then fed into 3D scanning software that interprets them and renders a model.
A similar technique uses the Microsoft Xbox Kinect instead of a camera.
You could then possibly bring the housings/parts and the rough renders to a CAD design company and have them touched up, but I'm not too sure exactly where or if you could get that done ('CAD reverse engineering').
There's also that FARO arm that aids in rendering, but you'd have to find someone or someplace that does it.
I hope I'm not getting too off topic, but I just wanted to give you some ideas and direction on this (aluminum housings) as it interests me.
Regarding increasing displacement, have you looked into the 16x engine?
I don't think there's too much info out there about it, but it might give you some ideas, as it seems like your ideas are the same direction Mazda was going with the 16x/Renesis II.
What I read is that they decreased the rotor housing width/thickness (to fit bigger rotors, I believe) and also even gave it aluminum side housings.
Personally, I don't think we'll see the 16x or at least anytime soon, unfortunately, but that's all up to Mazda.
Good luck with this, though. I'll definitely be thinking about this further and subscribing to this thread.
You could increase rotor width or eccentricity, but everything would be custom. IIRC there are industrial wankel power plants that vary widely in size.
You could, theoretically, sure.
How would clearances change with new dimensions? Who pays to test this? Who makes the seals? You'43 not maching new side, apex, and oil seals in someone's backyard.
scathcart, the front, rear, and center plates would have removable steel sides for contact with the rotors. I can CNC channels with side plates removed. which coolant channels do you foresee being a big problem? I posted this to discuss ideas such as these. so let me know your concerns in more detail.
I personally don't see how you can justify the current aluminum plate prices at $2000+. These pieces don't cost more than a few hundred dollars to make. rest of it is rotary tax. People say R&D, but R&D is already done by Mazda. As for programming CNC, I would do it for fun. I would just copy mazda's design and make it out of aluminum which would conduct heat away from the rotor housings way better than stock iron plates.
who pays for it? I think this type of endeavor would be fair game for tax write-off. and since I pay about half of my money already in taxes, it wouldn't cost me anything.
you don't need new side and oil seals. only width of the rotor would be increased which would mean custom apex seals which are hydro or laser cut from some alloy. I was hoping I can have one of the apex seal makers to custom cut a few seals for me. as for parts list, it would be wider rotor, wider apex seal, new apex seal spring possibly, new rotor bearing, shaft, rotor housing, and longer tensioner bolts.
in the end, you're probably right that I'm shooting for the moon trying to increase displacement. My initial goal would be to at least copy 3 and 4 rotor components in aluminum to bring down the cost. well honestly, at least having an open source style CAD file for rx7club.com community to contribute their inputs would lead to engine development. Once CAD file is available, I can easily cut the plate or shaft using my friend's ridiculous CNC machine. If I give them away at near cost which would be around $200 for 20b center plate and maybe $300 for 20b shaft, I'm sure R&D can done by us.
Have you contacted John Huijben yet?
I read through his thread in its entirety and I believe he has his own CNC setup and has at least machined his own aluminum center housings (modified design).
He also expressed that he didn't want to machine engine parts for sale as a business, IIRC, so maybe he's willing to give some of his renders to a fellow rotary enthusiast and forum member for free? https://www.rx7club.com/members/john-huijben-150833/
I want to make CAD open source. There are many bright minds on this forum, and I don't think it's a stretch to hope that, as a collective, we can advance 30year old 20b center housing, shaft, and other technology. My ultimate goal is larger displacement.
Many modifications regarding cooling passages, plug, concern of housing bump between the plugs, etc. exist and I hope to address each with the open source CAD drawing.
My motivations are my love for the rotaries and potential tax deductions associated with R&D. Ultimately, if I can come up with larger displacement setup, I think IRS will be quite happy. This rotary tax crap is getting old--paying 4k for 30 year old engine plate and another $3k on used e-shaft on a race car is just a pure bulls***.
I want to make CAD open source. There are many bright minds on this forum, and I don't think it's a stretch to hope that, as a collective, we can advance 30year old 20b center housing, shaft, and other technology. My ultimate goal is larger displacement.
Many modifications regarding cooling passages, plug, concern of housing bump between the plugs, etc. exist and I hope to address each with the open source CAD drawing.
My motivations are my love for the rotaries and potential tax deductions associated with R&D. Ultimately, if I can come up with larger displacement setup, I think IRS will be quite happy. This rotary tax crap is getting old--paying 4k for 30 year old engine plate and another $3k on used e-shaft on a race car is just a pure bulls***.
What we need to be thinking is 3D Metal Printing and Investment Casting for the easier parts (to keep costs down).
With the printing, we can do all of the old school hand-ported oil/coolant passage mods integrated into the design, so everything works better and NO hot spots. It offsets the cost differential substantially.
This is the company I worked for last. Growshapes based out of Santa Clara, CA.
Last edited by RGHTBrainDesign; 06-15-17 at 11:58 PM.
What we need to be thinking is 3D Metal Printing and Investment Casting for the easier parts (to keep costs down).
With the printing, we can do all of the old school hand-ported oil/coolant passage mods integrated into the design, so everything works better and NO hot spots. It offsets the cost differential substantially.
This is the company I worked for last. Growshapes based out of Santa Clara, CA.
How does that compare in cost to CNC. I've dealt with some metal printed parts for the aircraft industry. My job was to "correct irregularities" to make the parts usable.
As Stickman said, lot's of good brains on here and I have an idea to machine rotors, no casting. I think it would be an excellent way to make a rotor out of titanium.
SLA, I don't know the first thing about 3D printing in metal. and entry fee for proper metal printing is over $1mil. That's not happening at least for me. If you can pull it off and if the final product is as strong as the milled metal (which I heard isn't the case), that sounds very promising.
Tony, as for titanium, feel free once the CAD becomes available. I mostly want to focus on turbo application and will be milling it out of some forged steel alloy (I'm guessing 4000 series steel).
Whether Mazda builds it or not, there already is the ability to build your own 16X. It's just if people want to invest in it. If one goes that route, why not an 18X? Mazda has given us the clue in the 16X, narrow rotor is more efficient than wide rotor.
Whether Mazda builds it or not, there already is the ability to build your own 16X. It's just if people want to invest in it. If one goes that route, why not an 18X? Mazda has given us the clue in the 16X, narrow rotor is more efficient than wide rotor.
Where did you get the information that narrower is better? Thermodynamically, I cannot see an advantage of going that route. Besides, going narrower while trying to achieve larger displacement would mean entirely new engine which I cannot do. My only option is to go wider, and if there is convincing reason not to go wider, I would love to know why.
I just read about it. They narrowed the rotor width because the flame front doesn't have enough time to burn the whole width of the rotor per combustion cycle. This is to increase efficiency.
I am thinking about 80% increase in rotor width with 2 leading spark plugs and 1-2 trailing plugs. Having 2 spark plugs should solve the width issue. Not sure whether that would lead to any heat retention issues at the plug area with having 2 plugs so close to each other. Feedback welcome.
My point was if you're going to custom build custom stuff, changing it is just a little more work. I think the biggest challenge to a home made rotary would be the rotor housing. I think the only viable alternative to the way Mazda did it would be nikasil coated all aluminum housings. I believe that Porsche actually used this coating this way in some of their engines. One might machine and shrink fit a steel liner and the rest of the housing together but, the chrome is not just ordinary commercially available chrome. It's a special process that makes it porous to retain oil.
I disagree. It's not "little" more work. Changing rotor profile means absolutely new everything--everything from side seals, oil ring, o-rings, intermediate plates, front plate, timing crap, etc.
I'm not going to reinvent the wheel. Not doing any special coating, etc. Steel liner is something I thought about, but I most likely will talk with some of companies to chrome the housings when the time comes.
Like I said though, the main focus would be replicate some rare parts that has skyrocketed in price. I am hoping I can get some destroyed 20b parts so I can start playing with it in solidworks. Once I have these parts in accurate CAD format, I still think increasing displacement is feasible. Frankly, I am not sure why nobody has done it.
06-12-17, 08:05 PM
