1/4 scale Porsche 917 180 degree V12 Build

[Hugh Currin]

Dave:

Well, that answers that question. Does sound like you considered it though.

Nice progress.

Thanks.

[Mike R]

Dave,
Looks like good progress.  Are you creating specific code for each gear in Fusion (sorry if I missed it, skimmed through and if I read it I didn't register it).  I wrote a simple bit of G-code to conventional mill gears - edit the code with the # of teeth, gear width,  cutter diameter, cut depth, etc. and it does the rest.  Seeing Mikes comment on climb milling I may have to revisit and redo the code to climb mill.  regardless let me know if you want me to share it.  I wrote a DP version and a Module version and they seem to have worked out so far for me.

Mike

[steamer]

Thanks Mike!    Unfortunately I don't currently have an A axis on my mill other than my old school dividing head....
I have a simple program that cuts a tooth full depth with a gear cutter and follows up with a "Dead pass"...and that completes the cycle
Index the head and hit cycle start...simple as that

Dave

[steamer]

No machining this week....had a spot of bother design wise that I missed, but I've got the solution well in hand....and I'll expound when It's sorted out.

Luckily I found it before I got into it!..

It's a risk you take on a new design.......

[Roger B]

It's a risk you take on a new design.......

Been there got the teeshirt and the cap   

[Craig DeShong]

Can't recall one engine I designed where the design didn't change somewhat as the build progressed, either through errors in the design I uncovered along the way or just a better design discovered as I 'got there'.  To me, it's just part if the design/build process.

[Vixen]

Can't recall one engine I designed where the design didn't change somewhat as the build progressed, either through errors in the design I uncovered along the way or just a better design discovered as I 'got there'.  To me, it's just part if the design/build process.

Spot on Craig. I look upon the combined design/ build process is a creation process.

Dave will soon have it fixed and the engine design will be stronger than ever.

Mike

[steamer]

Can't recall one engine I designed where the design didn't change somewhat as the build progressed, either through errors in the design I uncovered along the way or just a better design discovered as I 'got there'.  To me, it's just part if the design/build process.

Spot on Craig. I look upon the combined design/ build process is a creation process.

Dave will soon have it fixed and the engine design will be stronger than ever.

Mike

Yes it will!!!     I have to do "Work" work this week....including yesterday and today...but I'll roll back in shortly.   

[JonC]

Great work Dave.

Following along quietly in the background, learning all the way.

Jon

[steamer]

So I had a situation.     

I found that the 4mm bolts holding the crank together where going to break out into the root of the center gear on the  crank.    That WAS a 32 tooth 32 dp gear, to fix that, I changed the gear to a 35 tooth.   Doing  that increases the distance between the upper distributor/fan shaft and to the output shaft.   That changes the engine block ....and the gear centers to the cams.....lots of bad words were used......

I just didn't see it, as it was approximately flush....why didn't I see it?   well I modelled the holes in the crank at .386" from the center.....and had a senior moment when I modeled the gear and typed in .368.....a simple transposition.....but it was enough to not see it

OK...the good news.   I have not started machining the block!....so I took a divergence, and remodeled the block to correct this

Gear counts were  32/56  35/40    for a 2/1 reduction

NOW   

Gear count is 35/56  32/40   also for a 2/1 reduction

It required changing the centers of the gears in the gear towers, and a change in the block centerlines, but nothing else that I can see.   It also afforded me the ability to put in bigger bearings on the lay shafts.  So it worked out for the best going forward

Then I had to work for the last 14 days straight including the holiday......so nothing has happened so far machining wise.

I was able to get a start on the new block, and sort out the placement of the internals.    so we're almost back on track.

the "honey do" list is strong today, but I might be able to get back out there and start cutting 35 tooth gears tomorrow....stay tuned....

I'm also glad I started the engine from the center out, or I'd of scrapped the block.   So far I've only scrapped a gear.

Dave

[Kim]

Sorry to hear about the problem, but it sounds like you've got it sorted, Dave.

Looking forward to seeing your progress after you get the family taken care of (most important, of course!)

Kim

[crueby]

At least it was found before the block was all made!

[Vixen]

Hello Dave,

Sounds like the 'fix' was not too drastic. Lucky you discovered the problem when you did, before you started on the crancase itself. Hopefully it will be plain sailing from here on.

Take it easier

Mike

[steamer]

Hello Dave,

Sounds like the 'fix' was not too drastic. Lucky you discovered the problem when you did, before you started on the crancase itself. Hopefully it will be plain sailing from here on.

Take it easier

Mike

Amen to that!!!

Dave

[Admiral_dk]

well I modelled the holes in the crank at .386" from the center.....and had a senior moment when I modeled the gear and typed in .368.....a simple transposition.....but it was enough to not see it

I guess that most of us have seen the 'crooked sentences' where some of the letters has been rearranged ....
Almost everyone that sees them can still read them and I guess that something similar is going on here + you will recognize all the digits that was part of your original plan -> I'm not sure Senior is to blame, but that it could have happened to everybody ....

Still good that you caught it so early in the build