Do companies just lend out their hard earned information for everyone to dupicate? No, so just sit back and wait.
Updated the TIs and found some of the information(journal diameters)
I’m going to call CSS and see if I can buy a single used rod/piston/ring assembly from Chuck.
Message sent to Chuck @ CSS in regards to buying a single reciprocating assembly from him for mockup/cutting up and a couple misc crank dimensions. We’ll see what he has to say :smile
I’ve been working my tail off the past week on this and have completed most of the R&D into the connecting rod choice for the motor. After looking into the dynamics of the rotating assembly and determining that the geometry of the OEM BMW components is not superb I decided the best route was to work all the requirements into a purpose built rotating assembly. BMW has all the correct geometry it’s just spread all over the place between the S50B30/32, S54, and S70 so using their OEM setups as a baseline I could pick and choose through a virtual “parts bin” for lack of a better term, and build the correct bottom end for a high revving NA V12. The S70 did have it all right, but go about obtaining the geometry of that motor(aside from bore/stroke)
This rod is variant one, designed as an H beam to be machined from billet VG nickle chromoly. I have a second billet variant of an A beam geometry specifically catered to Carrillo manufacture but that’s only a base template and backup as of now. Force oiled pin, designed to be lightweight. Not intended for any sort of forced induction here, the components are designed to serve only their function level 100%, plus a typical 15-20% margin.
Arrow Precision is going to be the manufacture unless I dictate a different rod configuration(IE Carrillo). I plan to work with Pankle for their titanium experience as well with a 6AL4V H beam. Pankle has been my source for titanium GT3-geometry connecting rods for various short stroke Porsche builds over the years and have an excellent track record with everyone who uses them. While titanium rods do have a limited fatigue life and must be replaced the added benefits for them in race applications dictate that I pursue that option, as options sell. Arrow Precision needs no introduction in the world of professional motorsports.
These images are the third from final rendering, but shows enough for here. I am sending the final rendering both to Arrow Precision and Pankle for small run production after the holiday and work up a collecting file there. Piston manufacturer is yet to be determined, Mahle and CP are on the top of the list due to their superior forging metallurgy. I still have quite a bit of work to move into those CAD’s yet. All my custom pistons I’ll typically send a few renditions to the manufacture of choice and have them send feedback, make changes/adjustments and work form there. You end up with the exact piston you need. Most piston manufacturers on the custom end of things will give you a piston that tends to be overkill in strength with 99% of the time leads to excessive weight. I like whittling things away until you get a scant piston weight with all the strength you’d even need for it’s dedicated purpose.
Just an FYI if you didn’t catch it above, this is not the final rendering of the rod. I merely touched up the third rendering to post here(final rendering are proprietary until machining commences). There are a few things changed between here and the final render as I can’t show everything ;D
Rod cap
Assembled, with bushing
Exploded view
This is the easier end of the work. Rods and pistons/rings come first, then I get to work on the crank design and balance order. Block will be the last major component, but that’s already known to work.
Questions, just ask away. Posting this here for your entertainment if anything.
Pff I was doing this shit in 7th grade. Project Lead the Way ftw. :rofl
totally jk, you’re a madman, man.
I’m not that bad am I…
You going to have dual coils and injectors like the S70/2?
change the FOV on the perspective viewports 
look a bit funny like that in ur original post
anyways looks good !
i used to model in 3ds max alot , before i had to work on web design daily =/
http://street-legal-mods.com/datas/users/243-vtec.jpg
http://street-legal-mods.com/datas/users/243-vtec2.jpg
vtec y0 ?
That’s just gay.
=/ go model something and show me
I was jk, it looks cool.
;D
The photos are not meant to look pretty. Those images are cropped/resized print screen views from trimetric view in Solidworks, some of which were rotated from the plane of view before hitting prtscrn. SW is catered to technical computing and to be able to instantly render objects for speed vs visual quality(IE, hatching of circles and lines in views). If I’m trying to make something look really good for visual asthetics I use Rhinoceros instead of SW, or import a SW file into photoworks and pretty it all up.
Nothing I do in CAD looks pretty as all my settings are for speed and processing. The beauty shows through in the final parts when CAM takes over, like everything machined on this bike :ssh
You CAD abilities are good…thought about pursuing a career in it or just not your cup of tea?
:bowdown
LOL, I don’t think I even know enough about engines to even ask a somewhat worthy question regarding your post. So I have a general engine question about light weight pistons and rods.
Is it true that the reason for light weight pistons and rods is to decrease the g-loads subjected to these components, hence making them easier to move under combustion.
not sure if your talking to me lol but uh, i modeled a ton of stuff, and then i stopped because it was just a hobby, and that took alot of my time up on the pc…
but i didnt wan to get into it for a career because i know SO many people on my site who can blow me away with 3d skills easily, some are so good you really cant tell if the render is a render or a real photo…
anyone can get good at 3d tho, just practice, i learned how to model in one week on 3ds max and from there it was all practice, no more learning really needed, yea some rendering tutorials but thats all
nice bike man looks good ! , by the way the other crap i modeled was very low poly, for games…
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Yes that is a reason. Lower the mass of the reciprocating assembly…that weights is 1/2 weight of the rod(small end), rings, piston pin, piston. Reducing that weight has many benefits like reduce cylinder wall wear, reduced bearing and crankshaft loading, less inertia weight to change velocity, etc, etc. Reducing that weight is coupled with the fact that you mus then balance out the rotating assembly weight(big end of rod 1/2, rod bolts, bearing shells, dedicated crank section(counterweights and crankpin) per cylinder. Too light is bad as well though, as without weight the inertia of the rotating assembly fights itself. After a certain point, you will start to loose torque and lose drivability(in small increments mind you)
My bad fissle. Yeah single COP with twin injectors per cylinder(port and upstream). Using OEM S54 for simplicity, their just fine for the application. Upstream injectors help with fuel atomization at higher rpms to help with power, driveability, and throttle response. Far more complicated setup and tune, but the benefits outweigh the cost and difficulty.
Little bit more of an update on this “project” if you’d call it that.
Piston development is moving right along. Core design is 95% complete with structural testing complete on the current core as well. Finite changes will be made by the manufacture to suit their processes and design parameters, but overall slug design will remain mostly the same as it’s a BMW replicant with necessary changes to suit use in this motor setup(deck height, rings land widths, pin boss offset, etc, etc)
87mm bore
11.5:1 CR
4032 alloy
Some images of the core CAD, 95% complete:
Top showing valve reliefs, lines shown for depth perception.
Bottom showing pin boss along with other features
On the topic of the rods and crank, Arrow did come back with a quote for $9K to make the rod set and billet crankshaft which is fair considering what’s being done. I received a few quotes from various piston manufactures and am still unsure as to who I will be going through with that though it’s looking more like CP vs Mahle due to not meeting quantitiy minimums for Mahle.
More updates later on.
wow very nice adam ! thanks for posting more renders dude
Way cool.
Who is actually doing the design and engineering work on your rods and pistons? I’m thinking you made that model in SW yourself? Or was it sent to you by someone else.
There are aspects of the design that I would change:
On the rod, the rate of change of your cross sectional area is not reflective of the applied stresses. It should be. Your cross sectional area should be proportional to your design stress. Your section modulus should change as a function of distance along the length of the rod. The big end of the rod is exposed to a constant angular velocity, and the small end only a linear velocity. You should have a section modulus that is appropriate for your buckling loads at the beginning of the exhaust stroke, BDC. This obviously depends on piston mass. Section modulus should change to reflect the transition from purely rotary to reciprocating.
Stress concentrations, I see you have not found the correct values for your fillets. Sure you have things filleted, but there is a science to the geometry here. Sharp corners and intersections can multiply the actual stress by 3x or more. For your particular application on the big end of the rod, your fillet radius should be:
Fillet radius/minimum thickness of rod = > .30
AND your big end size to your main rod thickness should be as small as possible. A ratio of two here is the difference between a Kt of 1.25 and 1.85. You can essentially double your rods tensile strength here, I’m not nit picking.
(Values from Design of Machine Elements, Spotts, Shoup, Hornberger. 8th edition, Pg 144.)
A custom rod design is nothing but calculus. Only calculus will provide the most efficient solution. Your primary goal as a part designer should be to establish the maximum applied loads and their directions. Then find out their frequencies and relative phases. Then establish the highest combined stress. Then find your design area, and then manipulate the section modulus to fit the varying load in the axial direction. Your answer will be very complex, hollow, and expensive to manufacture but you’re doing one-off work so it doesn’t really matter.
I only post this because It’s a cool project, and I like to see peoples home engineered parts. But if your actually going to pay for them to be made to your specs, you have TONS of areas where you could make improvements. I’d be glad to help.