TheSamba.com :: View topic - Fixing cranks; dowel pins loose?? Holes un-drilled and re-drill

Tue Jan 09, 2018 9:42 pm

Crank dowel jobs are a real challenge.
How do you make 8 pins line up perfectly at the same time, and fit perfectly straight in their perfectly fit holes with just the right press-fit?
You lie to yourself. That's as close as you will ever come. perfection is impossible :lol:
But I tried real hard this time and I took some pictures. Probably not enough pictures, but anyway it worked well enough I don't need to destroy the evidence, rather can share it.

Best christmas gift ever, my brother got me this fancy welding helmet.
Two LARGE parallel bars hang off the back of the table and there is my precision crank clamp-er, which is bored to 2.170" Shims are used to fit different sizes.

I welded up the holes, and faced the back of the crank flat again.

Put the flywheel on, check that it's straight, then attempt to ruin multiple drills and reamers boring into the welds. Wishing for a smooth hole with .001 press and praying they don't go oversize.
This device here lets you see how tapered ovaly and rough your holes are, which is depressing. it was a lot easier not knowing.

Success

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Tue Jan 09, 2018 10:14 pm

VERY NICE.
Thanks for sharing. And nice helmet, the Speedglas are my favorite masks.

What mangled crank was that?

Tue Jan 09, 2018 10:28 pm

It's the one you think it is. :wink:
Porsche journal, Okrasa

Whatever alloy these are, weld there will be HARD spots. like a-2 steel or something.
old scat crank, chinese crank, were far easier.
I haven't yet tried fixing the one you traded me. I probably will, since I have it all setup. CRANK MODE

Tue Jan 09, 2018 10:38 pm

Glad that you were able to fix it for him. I thought it might be the okrasa, the way they are finished is not like anything made now. And, very interesting to see the crank holding arrangement. I've been pondering the same thing, but have no parallels stout enough, yet :wink: sound like another excuse to buy tools..

I'm curious, since you've done a few of these repairs, what have you done / figured out along the way thats made the job easier?

SD

Tue Jan 09, 2018 11:06 pm

FGood post! I’m a Speedglass fan but I’’m missing the custom paint. Merry CHRISTmas! All these little details go unnoticed unless you’ve tried ‘em yourself. Try saving a hole by welding it shut or lay out multiple holes with a tight tolerance, diametric or X-Y, be honest. Just more small details that add up to ones work. :o

Wed Jan 10, 2018 1:35 am

I am just curious what the runout is after the flywheel was mounted?
Mount the package on a rollers and find out.

What did you do to cleanup the welds and establish the original flat for the flywheel to sit on?

Wed Jan 10, 2018 7:49 am

I'm getting a fizzy feeling all over my body!! :D

Wed Jan 10, 2018 9:20 am

glen, what size are those dowels? Have you ever used 8mm?

Wed Jan 10, 2018 9:34 am

Very nice job man. A lot better than I did at age 17 with a hand drill on an assembled engine.😁

Wed Jan 10, 2018 9:56 am

Modok, nice work. ..and that jig you made seems to work for you. ..I thought they made oversized pins to solve the oval-shaped hole problem? ...wouldn't it be easier to just re-drill all the holes for bigger pins?

VeeWeeman :D

Wed Jan 10, 2018 10:07 am

What reamers did you use?

Wed Jan 10, 2018 3:17 pm

Nice job! Looks like you have lots of other vw goodies layen around there, cool shop!

Wed Jan 10, 2018 3:30 pm

Holy smoked nuts! If there's ever a cylinder head shortage in the world, now I know who to blame.

Wed Jan 10, 2018 4:11 pm

How much material did you end up taking off the end of the crank to make it flat?

I have at least 100 cranks that I need to do this to. Many of them are perfect std/std too....

Wed Jan 10, 2018 4:35 pm

I would think the labor involved would make it too costly to save stock cranks.

Wed Jan 10, 2018 5:26 pm

nsracing wrote: I am just curious what the runout is after the flywheel was mounted?
Mount the package on a rollers and find out.

What did you do to cleanup the welds and establish the original flat for the flywheel to sit on?
To face it I used a simple flycutter, which I made myself, out of a crankshaft.

I indicated off the thrust surface to see the crank was square before facing it.
I then I took it off the mill, set on the flywheel and applied grinding paste to lap the flywheel can crank to eachother, then cleaned if off and bolted it up and checked runout again. When I put it back in the mill with flywheel attached I indicated the flywheel to see that the runout was the same as when it was on vee blocks.
I also checked the runout again after installing the pins.

Wed Jan 10, 2018 5:28 pm

[email protected] wrote: How much material did you end up taking off the end of the crank to make it flat?

I have at least 100 cranks that I need to do this to. Many of them are perfect std/std too....
Somewhere between .001 and .002"

Wed Jan 10, 2018 5:37 pm

veeweeman wrote: Modok, nice work. ..and that jig you made seems to work for you. ..I thought they made oversized pins to solve the oval-shaped hole problem? ...wouldn't it be easier to just re-drill all the holes for bigger pins?

VeeWeeman :D

Several of the original holes were ovaled so badly they were almost connected. The other crank in the last picture is next, I have only welded 5 of them, as 1 hole is ok and the other two can just be oversized.

Wed Jan 10, 2018 6:53 pm

Awesome work!!

Have you perfected the broken off flush pin removal yet?

Modok's FUBAR'ed crank repair service.

Brian

Wed Jan 10, 2018 7:41 pm

Ebel wrote: I would think the labor involved would make it too costly to save stock cranks.

when you can no longer find a std/std stock crank, it will be worth it. Hell, they're hard to find now.