Re: Fly wheel housing cracks

Posted by carla on Sep. 22, 1998 at 21:37:53

In Reply to: Re: Fly wheel housing cracks
posted by Gordon Biggar on Sep. 22, 1998 at 19:46:57

: : I just cleaned up my fly wheel housing and found some cracks inunexpected places.
: : I have two cracks approx. 1 1/2" long extending through the mounting holes at the 3 and 9 o'clock position where it bolts to the engine.I have heard that the upper two "ears" where the accelerator bracket bolts up is the common place for cracks (none here).
: : Can someone offer advice on options? Welding, metal stiching, etc.?
: : Thanks, Benny
:
: _______
: Benny --
: I just went through all of this a few months back.There should be some postings on the Board, as of the Spring of this year.If you decide to repair, which I would do since you don't plan on pulling this apart any time soon, there is a very definite procedure to follow.Cast iron tends to be difficult to work with.However, if you gradually heat up the housing to some 400 degrees over a period of 4-6 hours, you can then stick weld the cracks (bronze, if you prefer).Heat should then be removed slowly over a period of two hours.A rapid cooldown will create more cracks.
: If you are not doing this yourself, I would mention to whomever is doing your work to use this gradualistic approach.
: Good luck.
: Regards,
: Gordon
hello, gordon and benny,
i would think that you would do better to find a good used part, cos any weld in a cast iron part is, in reality, a gambling device, and your part can be cheaply replaced.
that said, if you would like to try welding up your part as a learning experience, read on---
the technique that gordon describes is a good one, in terms of weld strength and stress relief, but has a chance of developing a bit of warpage. there are differing opinions as to whether clamping the part against its mating part will pull it back into alignment without stressing the part, possibly leading to more cracking. my own guess is that it would be better to face or mill ( or-- ugh--shudder--hand scrape ) the part back to flatness and parallelism.
another technique would be the so-called "cold welding" or "hammer welding". to do this, you would drill small through holes just past the end of the cracks, and v groove the cracks as usual-- preheat the part only slightly, just enough that you cannot comfortably hold your hand on the part for more than a few seconds.
use 3/32" "ni-cast" welding rod, d. c. straight polarity,
try about 120 amps on a piece of scrap, and adjust your voltage and amperage settings until you get a nice bead.
on the part itself-- run only a few seconds of weld-- a very short bead--1/2" or less-- break the arc, and immediately peen the bead vigourously until cold with the pointed end of a chipping hammer-- the peening will expand your bead enough to offset the contraction as the bead cools. wait a bit until the area around the bead has cooled enough to touch, then do another short bead-- continue welding, peening, and cooling like this until the crack is filled.
this works well on cracked engine heads, with a minimum of warpage.--- its a good way to learn patience, too.
carla