23 November 2014

Engine details Part 5: Crankshaft of the 1974 Datsun 160J SSS KP710 Violet Turbo

Crankshaft was taken out a couple of days ago. Just back from out of town so after having done all my family chores here I am blogging about this masterpiece...

Figure 1
LZ18 Crankshaft sports 8 flywheel holes.
Gear collar at front drives the gear set that turns
 dual camshafts near up top via a short chain.
My qualms with the crankshaft was that all the five main journals have had their radius transition onto the journal surface disturbed wrongly by the last machinist.

Before sending off the crank, I plan to remove the gear collar by a suitable puller tomorrow. The distributor drive collar came off easy but not the cam gear collar. Will update with a post soon!

Figure 2
The con-rod journal are standard and ok. Note the main journals!

Figure 3
Do you see it? The radius transition onto the mains are sharp and of a smaller radius.

Knowing what stress concentration and transition means, and having studied mechanical engineering and material science, I was at first so distraught by this I gave up on the rebuild 21 years ago after trying to locate another LZ18 crankshaft with no success. Today, despite the process being available decades ago, the web now allows much better advertisement, payment and shipping options so I'm back on a roll to rebuild the engine!

1) Submerged arc welding to build up the radius and journal

2) Reshape back to standard journal diameter and radius size

3) Heat treatment (Nitriding)

4) Straightening crankshaft

It is probably better to grind journals back with a slight extra, heat treat it(Nitriding) and then final grind the hardened surface to standard size. All this has to tie in with straightening the crank while it is hot off the oven. I'm no expert, just wondering!!

Enough said for tonight...Cheers everyone!! :-)

No comments:

Post a Comment