Case crack

Fritzer_108

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Sep 27, 2022
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I've got a 1952 88 Dominator engine and am rebuilding it for a build. I noticed that compared to the Atlas, this engine has a "rib" running through the middle of the case. Firstly, I am curious what the purpose of this piece is because my Atlas engine does not have it.

Then, I saw that there was a cracked at the base of this middle member. Is it something to worried about? Is it repairable? Thanks!!


Crack 1

Crack 1


Crack 2

Crack 2

 
You have not confirmed - does the "rib" line up with this crack? As in - likely to be a repair.
 
Fritzer_108 said:
What do mean with "Line up"?
Click to expand...
I mean - is it possible that the "rib" is a weld repair of that crack?
No picture of the "rib" leaves us guessing
The crack looks scary but has it been repaired? Photo of gasket face only tells so much
 
I note there is another hairline crack across the rear of the bridge (the one that isn't there for later models). Probably means the bridge is not working as intended and could be removed. Later dominators and all commandos never had that box bridge.
 
Here are pictures of the cases. What I call the "rib" is the box bridge I think. Sorry, I didn't know what is was called.

88 500cc

88 500cc


Atlas 750cc

Atlas 750cc


I've been talking about the hairline crack at the rear of the bridge. Is this a structural member and what role does it play? Do you also any other cracks?
 
Fritzer_108 said:
Here are pictures of the cases. What I call the "rib" is the box bridge I think. Sorry, I didn't know what is was called.

88 500cc

88 500cc


Atlas 750cc

Atlas 750cc


I've been talking about the hairline crack at the rear of the bridge. Is this a structural member and what role does it play? Do you also any other cracks?
Click to expand...
Yes - It appears to me to be a significant one this side of the rear stud in your first photo - looks like the crank casing is cracked through - don't know how far down it progresses. I thought this was the crack you were talking about
 
Fritzer_108 said:
Here are pictures of the cases. What I call the "rib" is the box bridge I think. Sorry, I didn't know what is was called.

88 500cc

88 500cc


Atlas 750cc

Atlas 750cc


I've been talking about the hairline crack at the rear of the bridge. Is this a structural member and what role does it play? Do you also any other cracks?
Click to expand...
I think it was probably designed as a structural member then, at some stage the penny dropped as, it was deleted from later models.
I can't honestly see any harm in removing it.
The only risk in leaving there, as is, is that the front may crack and it could drop onto the crankshaft with unsightly results.
 
robs ss said:
Yes - It appears to me to be a significant one this side of the rear stud in your first photo - looks like the crank casing is cracked through - don't know how far down it progresses. I thought this was the crack you were talking about
Click to expand...
Actually - looking at it again it just may be a quite crooked joint between the case halves.
 
robs ss said:
Actually - looking at it again it just may be a quite crooked joint between the case halves.
Click to expand...
I think it may just be that. I couldn't find anything when I checked. I'll try to see if I can save the bridge but I'm glad to hear it won't be a major problem
 
Hi Fritzer. Shape of the crack suggests bending fatigue stresses in the "rib" or bridge. Think of the heavy barrel and cylinder head swinging back and forth on the crankcase top.
While it is possible to weld the "rib" (bridge), it will require a post-weld heat treatment, otherwise your cases will probably warp.
I second "Robs SS" in #8 -- the engine will cope without the bridge, and removing it as per Atlas design is a better solution than just leave it be.

- Knut
 
Fritzer_108 said:
I've got a 1952 88 Dominator engine and am rebuilding it for a build. I noticed that compared to the Atlas, this engine has a "rib" running through the middle of the case. Firstly, I am curious what the purpose of this piece is because my Atlas engine does not have it.
Click to expand...

A feature of the early Dominator cases that later cases do not have, some parts drawings show a bridge on each case.
Case crack
 
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