Crank assembly

[Rick Blood]

I am doing my first crank and rather than destroy it with ignorance I figure I will ask questions. This one happens to be a CR80.
Are there any tips for assembly?
What lube if any do I use on the pin?
Should I use the hot/cold method?
How do I assure proper alignment?
How do I make sure that I don't press it past the pre measured width?

[Pete Muller]

Rick,

Are there any tips for assembly?

Lots.

What lube if any do I use on the pin?

Sunnen makes a special lube for press-fit assemblies. Personally, I use heavy-weight way oil. Something like STP would probably work fine too.

Should I use the hot/cold method?

Huh?

The amount to be gained be heating steel is minimal... additionally, the diameter is so small there is not much to be gained because of that either. Don't waste your time heating anything.

How do I assure proper alignment?

Ugh... this gets to be a bit complicated. I'd have to assume you don't have a die-set, correct? How you assemble the crank depends quite a bit on what type of equipment you have at your disposal. I'd assume you have a press? How big? (tonnage). What else do you have?

How do I make sure that I don't press it past the pre measured width?

Either with a fixture... or very carefully using a micrometer/vernier. The bigger your press is (tonnage), the easier it will be.

- - - -

Any chance you can get somewhere and watch an experienced engine builder assemble a crank? - This would probably shortcut your learning curve a lot.

PM
Muller Machine

[ October 26, 2001: Message edited by: Pete Muller ]

[Randy Fergus]

Pete,

By heavy weight way oil, are you referring to a Vactra-2 type of oil? Or something heavier than that? Could proper clearance be assured by a ground no/no go gauge? Would "perfect" alignment require using a fixture to preset the sections? If so, is this a commercially available product or a "tool and die" type project? Or would that be up the the individual builder's preference? Sorry about all the questions but I'm laid off from my "real world" machining job and am considering leasing some machinery to do some of my own stuff. Gotta save your pennies where you can, ya know?

[Pete Muller]

By heavy weight way oil, are you referring to a Vactra-2 type of oil?

Sure... that would be fine. Just something heavy and slippery. Main thing is not to put it together dry.


Could proper clearance be assured by a ground no/no go gauge?

Are you referring to clearance in the big-end rod bearing?... or interference in the crankpin fit?

Either one of those is best measured by using a micrometer and a dial bore gauge.


Would "perfect" alignment require using a fixture to preset the sections?

Actually, it's virtually impossible to get perfect alignment during assembly (even using a perfect die set). You'll still end up having to bump the crank around to get it aligned. A nice die set though just allows you to press the crank together fairly close with a minimum of hassles.

If so, is this a commercially available product or a "tool and die" type project?

You'll end up having to make it, though someone out there might offer one (I'm not aware of it though). If you've got a bit of time on your hands, you can just buy a surplus die set and do the machine work on your own... saves a lot of money.


PM
Muller Machine

[ October 26, 2001: Message edited by: Pete Muller ]

[Rick Blood]

Thank you Pete and Mark Watkins for your advice.
The crank is back together but not without a fair share of four letter words and a strong fear that it would never see the inside of our motor again.
If anyone thinks that this is an easy do it yourself project, I would suggest that you buy a new crank and have it handy if you goof the old one up.
The guys that get paid to do this deserve whatever they charge.

[Michael Polizzi]

Hi Rick

RCE has an alignment tool for this purpouse. They are a bit expensive. here is the link: http://www.rceracing.com/cranktool.html

Michael Polizzi 69n
fullborekarting.com

[Sean Cook]

Rick,

Glad to hear that you have a new respect for cranshaft labor. You would be surprised how many people complain about spending 40 dollars to have their rod changed out. There are many tricks that are learned through experience when pressing and aligning cranks.

Sean Cook
Cook Racing Engines

[Rick Blood]

Lets see, 10 stress filled hours missing from my life, 30 miles put on my truck tracking down the tooling, 4 heart attacks every time the crank popped while in the press or...40 bucks. Tough decision.

[Mark Watkins]

Rick,

Glad to see you are trying to grow as an engine builder and crew chief. Cranks can be a pain in the *** , but the up side is not depending on someone else with a very critical piece of the motor.

Donnie Bootes(you know him, 15 Duffies and 20+ Daytona Silver Cups in shifters)taught me and I praise him every time a do a crank. He uses only his press, small pushing and pulling tools, a well worn brass hammer and a dial gauge. Anything over .0005 is wobbly to him.

Mark

[Pete Muller]

quote:

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Originally posted by Rick Blood:
Lets see, 10 stress filled hours missing from my life...

---

That's all the first crank you've ever done took you??... 10 hours?

You're doing great, Rick!

Seriously... it's one of those things that gets easier and easier.

A couple small suggestions:
Make sure that you polish the ends of the crankpin, and also polish the corner of the crankpin bores in the crank halves. Anything you can do to reduce/eliminate the chance of "pulling metal" during assembly makes the crank easier to true.
Another thing: If you are struggling to get the crank to run dead true... kind-of "chasing around" the runout a bit... just let it sit overnight and give it another try the next day. There's a LOT of stress in the metal after assembly (.003+ interference on a 20mm pin is not uncommon) and sometimes the metal just needs to relax a bit before you finish true it. I know this sounds a bit hocus-pocus... but it works.
A final note: that "popping" you mentioned when pressing it together... the larger a press you use, the less this will happen. The popping comes from a "bend and release" force (in the frame of the press), so if you use something like a 50 ton press (instead of a 20), the assembly will go "smoother".

Pete
Muller Machine

[Rick Blood]

quote:

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Originally posted by Pete Muller:

just let it sit overnight and give it another try the next day.
[/URL]

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And I thought I was going crazy. Thats exactly what happened. I left it last night at about .0004 on the mag side and .0035 on the other. This morning it was .0003 and .0007. I must have checked it 10 times to make sure I was reading it right.
I shall sleep well tonight.
Thanks

[Pete Muller]

Nope... you're not going crazy.

How the crank is assembled will have an effect on this "phenomenon". The aforementioned polishing of entry points, lube, rigidity of the press... etc., are all variables in the assembly.

I always let a crank sit overnight before final truing. I just bang 'em in pretty close (say under .001) and then come back and finish it up the next day.

Your mileage may vary.


PM

[Brad Boyer]

As this thread has pointed out, manual pressing and alignment of cranks is a time consuming process. One tool that many shops (Eric Gorr/Forward Motion swears by it) use to dramatically speed up crank alignment after new rod/rod bearing installation:
http://www.rceracing.com/cranktool.html

Hope this info helps out.

[ October 31, 2001: Message edited by: Brad Boyer ]

[lynn haddock]

I use a die set for the initial pressing operation.......the crank width is easily controlled by making some (3) steel stop pins--these are placed at 120 degree angles around the crank and act as a stop for the die set. These pins can be made to any length desired (crank width) and can also be fine adjusted with steel shim paper or feeler gauge stock.

[fatoldman7]

Are you folks using the centers at the end of the cranks, or V blocks when you are indicating in your cranks?