1/4 scale Porsche 917 180 degree V12 Build

[steamer]

Must feel good to get your process verified by the first good part!   

Dave, how are you guaranteeing the 0.520" spacing?  Do you have a gauge block or something that you're using to set between them as you do the press-fit?

Kim

I bumped it in with the mill vise, but I'm going to use an adjustable parallel that I can collapse and then reset.   I have .005" on both sides of each con rod bearing so I have some room for error, but I'm striving for on the nose.

Dave

[steamer]

Great to see the progress.  Sometimes the 'hard' stuff isn't as hard when you get into it.  Looks great Dave.

YUP!!!   So now I'm wondering about the stuff I think is going to be easy!!!

Now coming this far, I'd say that .002" interference on a hardened pin in the 6-8 mm diameter range is no problem at all.   It hold very well!   With it pressed in 1/4 the way, it needed to be moved with a soft faced hammer, so pressed home it's not moving.   My engagement is 1 pin diameter deep. 

I used a 0.265" diameter crank pin as I can get graded reamers going up or down easily in the states.   Now over seas, 7 mm diameter may be a better choice, but check for reamers that are appropriately undersized ( 0.039 to 0.050 undersize) so that you get the press you need.    The pins were made from precision ground A2 tool steel, that aside from drilling through and parting to length, were finished diameter and +/- 8 microns..    It needed little other than hardening and polishing.   Lightly round and polish the ends with some 600 grit to ease the pin into the hole to start with.

Dave

[90LX_Notch]

Nice Dave!

-Bob

[Admiral_dk]

Great to see the first parts come together 

Per

[steamer]

I was able to get 3 more assemblies together and some photo's    I make myself a "Sledge" as at .06 insertion depth....you need it!

And a family shot.....lots of parts....

[Kim]

Great set of process pics, Dave.  Really helps me see how you're tackling this!

Nice box'o parts too! 

Kim

[stevehuckss396]

Good stuff Dave!

Will there be a grub screw or some kind of pin to keep the disk from rotating on the pin?

[steamer]

Good stuff Dave!

Will there be a grub screw or some kind of pin to keep the disk from rotating on the pin?

No   not required.    Once it's in the block it can't physically move.   

Dave

[Vixen]

I was able to get 3 more assemblies together and some photo's    I make myself a "Sledge" as at .06 insertion depth....you need it!

And a family shot.....lots of parts....

The crankshaft looks to be coming together nicely. 

That was a neat trick to use the mill vice to press the pins home. A mill vice will keep everything square and parallel and you should be able to apply the force with much more control than with a fly press. I also like the depth stop ideas to set the length and gaps. What I could not see was how you aligned the two discs before you pressed the second disc home.

Cheers

Mike

[steamer]

I was able to get 3 more assemblies together and some photo's    I make myself a "Sledge" as at .06 insertion depth....you need it!

And a family shot.....lots of parts....

The crankshaft looks to be coming together nicely. 

That was a neat trick to use the mill vice to press the pins home. A mill vice will keep everything square and parallel and you should be able to apply the force with much more control than with a fly press. I also like the depth stop ideas to set the length and gaps. What I could not see was how you aligned the two discs before you pressed the second disc home.

Cheers

Mike

Hi Mike,

After you press the first side home, line up the second side by eye, and using the vise, press the pin about .06" deep using the vise.    Then I set the "A" side down on the flat tail of the vise, and brought a square up against it.    In this case, it was the sharp edge of a precision ground V block which is known square.   

If the two crank cheeks are aligned correctly, then both crank cheeks should touch the square at at all positions checked around the crank module assembly.    If it is not, I bring the assembly over  to my vise, and "bump" the "B" side web around rotationally around the partially installed crank pin until is passes this test.   It typically takes 3 or 4 or even more tries to get it acceptably aligned.

It doesn't need to be perfect, as the "B" side will be machined next using the finished "A" side as datum.   

Once acceptably aligned, I return the assembly to the vise, install the pre-set width stop, and press the "B" side home.   Once there ....it's not moving.

The "B" side has 0.04" on diameter, and .03" on length  to come off to get to finish dimension.   Any error left from the press fit assembly operation is removed by machining.

Dave

[Vixen]

Hi Dave,

Thanks. I can see how that works. Neat and simple, I had anticipated something more complex

Mike

[steamer]

Hi Dave,

Thanks. I can see how that works. Neat and simple, I had anticipated something more complex

Mike

Thanks Mike.....

Honestly....It's the way to go.   It gives you a chance to correct errors along the way and different steps of the process.   So far I am very happy with the Schilling approach, and can recommend it.   Schilling recommends .001" press fit....but I found with a hollow crank pin, you can go up to .002" which gives you some leeway on the pins and bored hole tolerances.   And I mean it....once that pin is in....It's not moving...I estimate it would take a 2 pound ball peen hammer to move a crank web once it's pressed home.....it's very secure....

Pins are .265 OD x .156 ID A2 hardened tool steel with 1144 SP crank webs with a .0015 - .002" press fit.

Crank pin is hardened to 50-55 Rc.

Build a few extras to make up a trial assembly to sort out doing this in YOUR shop..  You will learn alot.

Dave

[Vixen]

.........Build a few extras to make up a trial assembly to sort out doing this in YOUR shop..  You will learn alot.

Dave

Thanks Dave,

It is all too easy to overthink the problem. It's only when you have some hardware to play with, that you understand

Mike

[steamer]

.........Build a few extras to make up a trial assembly to sort out doing this in YOUR shop..  You will learn alot.

Dave

Thanks Dave,

It is all to easy to overthink the problem. It's only when you have some hardware to play with, that you understand

Mike

Aint that the truth!!!!

[steamer]

Making the lathe fixture to finish the crank cheek.....material was left on the bearing OD and face for this operation.   Needs some tapped holes.