Birth and Death of a crankshaft - a.k.a. "I had a huge Stupid Attack!!!!"

[dicej32]

After a few days off in my shop I decided it was time to tackle the crankshaft for my Upshur Farm engine. I decided I would machine it out of 1018 steel as one piece as described in the plans. I milled it to size, marked out the offset centers and rigged up a between center setup on my Taig. I grind up some hss tools according to an article in Model Engine Builder. On my little Taig, machining steel this size is a slow and tedious process. I figure I put in about 1 to 2 hours a day for about a week in my spare time to just machine the main journal. Here's a picture of my nice shiny finished journal:

Very satisfied my result, I proceed to unmount the part so I can saw off the excess material so I can turn the crankshaft ends on the 1/2" off set center. I mount the part in my vise and cut down the middle first on both sides of the journal. Cutting 1/2" steel with a hacksaw is cruel and unusual punishment but lacking a bandsaw, the only alternative.

After about half hour of intermittent cutting, I finish the longitudinal cuts. All I have left are two 1/2" cuts across the part. I remount the part in my vise and cut away. Have you guessed yet what I did? First the picture:

Pretty nice huh? A 0" THROW CRANK!!!!!!!!!
Needless to say it's hard to convey what I felt at the moment. After considerable expletives in English and Spanish I had to walk away from my shop. It was only yesterday after 4 days that I was able to get back in the shop. There's no way I'm going through the ordeal again of machining a one piece crank on my small equipment. After looking at it for a while, I decided to try to salvage some of it by combining the machined journal/web with a pinned and soft soldered shaft. Here's where I'm at:

Looks like it's going to work. I'll have to make a few spacers as the main journal/web assembly is about .10" too narrow but that should not be a problem. I'll continue updating soon. What was that saying, "Measure twice cut once?" Lesson learned!!!!

Jenaro

 

[steamer]

Don't beat your self too bad....anyone who says they have'nt pulled a boner...hasn't built anything.

What hurts is your already done with the hardest part!...the Journel!

Oh well

I think you recovery approuch is on the mark!....good luck!


Dave

 

[mklotz]

Jenaro,

Having made similar mistakes in the past, I've adopted the practice of marking the pieces to be cut away with a large 'X' using a Sharpie with a color that contrasts with the metal. Only takes a minute and has saved my bacon a number of times.

Just be sure, after doing the marking, to check the marked up block against the print to ensure that you haven't mismarked. DAMHIKT.

 

[Mcgyver]

Pretty nice huh? A 0" THROW CRANK!!!!!!!!!

@#$@#$@$@#$@#! lmao! I gotta give you a karma point for that, takes a big man to admit his mistakes; you're a giant among men :big: :big:

might not help much now while you're in pain, but think of the years of of grins you'll get thinking back on that one.

good save on it though

 

[steamer]

Cranks are always tough...
My first crank was at the same state as dices, after the last pass on the center throw and being ever so carefull, I just cranked the carriage back.....before I shut her down.....&%@#^%#!

I showed it to my mentor at the time ( fully expecting I would be making another) and he laughed histerically as he knew EXACTLY what I had done...

On a whim,he layed the now pretzel shaped crank on the bed of his HUGH mill and hit it twice with a babbit hammer....amazingly enough it bent right back into shape and only had 0.003" run-out...used it as is....still runs! ;D

If your gonna bake a cake...you gotta break some eggs!...and it's not always pretty!

As time goes by...you will giggle more

Dave

 

[Philjoe5]

Jenaro,
Thanks for sharing that. It will keep me on my toes for the next few days as I machine a new engine cylinder for the first time. Being able to salvage the part is good. You can always go back and remake the part later.

Cheers,
Phil

 

[kustomkb]

At work and at home I keep a couple messed up pieces in a frequently used drawer of my toolbox. It keeps me humble when I start getting cocky. Nice save though.

 

[Bernd]

Life handed you a lemon and you made lemonade. Excellent. :bow:

BTW, I also have a subscription to Model Engine Builder. I've got all the back issues to #13. Waiting for this years first issue. Haven't seen anything and it's the begining of April. What's going on?

Bernd

 

[steamer]

Thats a good question, I kept meaning to call

So I did........sorry don't want to hijack here so I will be very brief.

Toni and Mike are working feverishly on it. I am told issue 14 will be complete soon.

They're good people, they'll come through.

Dave

 

[Bernd]

Thanks Steamer. Back to on topic now.

Bernd

 

[BobWarfield]

You know, there are worse things than the "stupid attack". At least when you really screw up badly, it is obvious you should start over. What I hate are the "near misses." With a near miss, you are so close, you are tempted to try to force things to work out. Hours can be wasted to achieve a mediocre result at best, and total failure is a more common outcome. Knowing when to just scrap the part and try again is some judgement that I guess must take quite a lot of experience.

Now this eccentric crankshaft turning sure does look like some fun to play with. I guess I'm going to have to start making a list of engines I want to build. So far my project wish list is all tooling, but I must say, this site has opened my eyes to so many interesting engines its amazing.

Thank you all for that!

Best,

BW

 

[rake60]

Jenaro I doubt there is anyone here that hasn't made at least
ONE fatal exception on a part.

A few of us have had the pleasure of doing it at work.
It's a long walk to the formen's office when your trying to
come up with a good reason for why it happened...

At home it's a different story.
Your plan for the salvage is just a minor adjustment of the
original plan.

Rick