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Front Engine Dragste
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Discussion Starter #1
Trying to get my beat up EF back on the road after mostly killing the SOHC ZC motor the guy before had torched the headgasket in . . .

Picked up a complete D15B6 for $40 on CL with a bad piston and started looking at the thing.

Crank is basically a D14 with the extra stroke so the idea behind the motor is a lightweight everything build (car is gutted out, has dreams of being a real race car) with d17 pistons to get the piston weight and ring weight out which leaves a custom rod.

Center to center length is standard 137mm with a pin end size of 19mm but the big end is only 41mm.

So taking a bunch of ideas from Lentz, Jager, and CP I came up with this:



Solidworks says weight will be around 360g which still puts me about 25g over the factory D15B6 rods (which are tiny).


Picked up a mint set of CARR (Carrillo) 5/16 rod bolts which are their Multiphase bolts with 285,000 Ultimate tensile strength. If nothing else, these should at least hold :ugh:





Finally got some 4340 in last week and spent an hour on the bandsaw since it was a drop and way too big in every dimension to use as-is.

Split it out in Solidworks and doing the cap and rod as two separate pieces. Eventually going to wire EDM the wave feature which is how the cap interfaces with the rod.

Worked some hours this weekend in my "free" time to get to this:



Need to bring the ball end up a hair and split the .090"CR end mill (it needs to be put out to pasture anyways) depth in two but otherwise the program for the front half of the cap is done.

Making 6 caps and rods (figure the setup piece is almost always not exactly on) and the next op is finishing the backside then the vertical work.
 

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EG8
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Rocket Motorsports design/stress test:


Idk the material he expected to use, but in comparison your I-beam flange looks thin. And the most important feature is the web anyway, plus the big radius helps, so it looks interesting.

And with the direction of technology, things just look crazier and crazier anyway: 3D printed titanium 35% lighter, 40% stiffer. All about those radius'!


Anyway in for more, and maybe pics of your stress test as well.
 

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Front Engine Dragste
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Discussion Starter #3 (Edited)
Rocket Motorsports design/stress test:


Idk the material he expected to use, but in comparison your I-beam flange looks thin. And the most important feature is the web anyway, plus the big radius helps, so it looks interesting.

And with the direction of technology, things just look crazier and crazier anyway: 3D printed titanium 35% lighter, 40% stiffer. All about those radius'!


Anyway in for more, and maybe pics of your stress test as well.

The beam is my takeoff of the Lentz rod used by a lot of NASCAR teams:



(The other major supplier being Pankl which uses a more conventional forged/h-beam style rod). The beam lightening is also done by a ball mill with a larger radius than the depth which means there's no straight wall anywhere . . . the radius basically just leads out. From a design standpoint, I love doing that since there's little need for deburring straight out of the machine and it feels great when you hold them. The feeling part obviously means nothing in this application but the strength is there since few straight corners or edges exist. They will be shot peened anyways regardless.

While I have Solidworks, it is very limited in scope as far as the options I have in the Simulation XPress deal.

I can show the von mises stress and deformation but I really don't know if the values I am putting in are good not to mention my fixtures and forces in SW are super limited since I don't have the top of the line premium package.


At any rate, ran all of the caps through the 2nd operation. Just have one more setup left.

 

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I have a D13 that I've been planning to boost for ages now. I was looking at getting a seet of Crower Maxilite rods, but if you manage to get yours into production and are interested in making these for others, I'll be very interested.
 

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Front Engine Dragste
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Discussion Starter #8
When will these up for sale?

Are ya taking custom orders?
Ha.

Eventually . . . one day . . . :fingersx:

I've got a long ways to go before I would feel confident enough to actually sell a set of rods.

Plan is to finish these up and run it for awhile to make sure the design works and more importantly the heat treatment and tempering will work for what they need to do.

I'll be daily driving the motor for awhile and probably spray it till something breaks (which I'm sure the d15b6 crank will first) while I build a motor I think can compete in some of the all motor classes.

These rods are more about getting the process right then selling sets. Would love to down the road though.

Let me holler at that STL file. I want to 3d print me some rods for decoration!
Sent you a PM . . . let me know.

I have a D13 that I've been planning to boost for ages now. I was looking at getting a seet of Crower Maxilite rods, but if you manage to get yours into production and are interested in making these for others, I'll be very interested.
Sounds good . . . like stated earlier though I'm not sure of a timeline for these.

I need to get the motor together sooner than later. I hope to finish these rods next week sometime depending on work schedule/machine schedule.
 

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EG8
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I mean even without 100% accurate #'s the stress and deformation simulations can still point out the weakest areas of the design, which is what I am more curious about anyway.

Are you sending them off to be heat treated or DIY? That's awesome that you're hitting all the right check boxes for sure though.

I design a handful of things, and help others do the same. My curiousity is always in fatiuge and failures, so I'm not saying your design is lacking in any way at all, just noting features that are significant to me. But even the slightest adjustment can be the secret sauce between success and failure.
 

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Front Engine Dragste
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Discussion Starter #10
I mean even without 100% accurate #'s the stress and deformation simulations can still point out the weakest areas of the design, which is what I am more curious about anyway.

Are you sending them off to be heat treated or DIY? That's awesome that you're hitting all the right check boxes for sure though.

I design a handful of things, and help others do the same. My curiousity is always in fatiuge and failures, so I'm not saying your design is lacking in any way at all, just noting features that are significant to me. But even the slightest adjustment can be the secret sauce between success and failure.
No doubt . . . the FEA simulation says they would "fail" where you pretty much expect them to . . . right in the transition/radius from the main beam to the boss for the big end. My only options in SW are a pressure (psi) or force (lbf) . . . I've been reading around 1200psi in the chamber? Then pressure exerted to a 75.5mm piston and then to the pin. I can grab a picture on Monday.

They will be sent out for heat treat. We use Braddock metallurgical here in Atlanta for most of our heat treatment as we usually have 10-20 items a month for our other job shop work.
 

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Front Engine Dragste
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Discussion Starter #11
Caps are getting close . . . just have to grind the sides to make sure the bolt holes are as parallel as possible to the outside edge and then throw it back in the mill for the vertical thinning done with a ball end mill.



At this point the caps are 126g and the stock d15b6 is 100g even. Should be pretty close after the ball end work.
 
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