[Milsurplus] Dynamotor Repairs

[WA5CAB at cs.com]

Jim,

I never thought about trying this, and may, if I can find any units still 
here that I haven't already thrown away the casting pieces from.

This problem seems to be most prevalent with the DM-28-B.  And it is far 
worse with the support castings than with the brush and bearing carrier 
castings, although I have seen some of them broken.  I've had around 50 +/- 
DM-21-B's  NOSB and at least a third of them had at least one broken casting.  I 
haven't had nearly as many examples of other letter models but only about two 
had any broken castings.

In a message dated 9/8/2010 11:13:19 PM Central Daylight Time, 
jimandterri at bellsouth.net writes: 
> It is with  interest that I have followed the contributions on  dynamotor 
> repairs. I have something further to add to the discussion.
> Some time ago, I picked up a DM 21 dynamotor for my BC 342   only to 
> discover later that the zinc end castings were cracked and shattered. in this  
> model dynamotor there is an abundance of damaged end castings and that makes 
> for lots of Junkers and not so many extra  castings. (of course, I myself 
> picked out a Junker)
> almost as an afterthought before throwing the broken parts away, I decided 
> to try super glue, now don't dismiss the idea as entirely misguided, the 
> application of Cyanoacrylate (Super Glue) is at its best in jagged porous 
> closely mating surfaces and that's just what I had with the cracked castings. 
>  I carefully cleaned and dried the castings to remove all the oil that had 
> migrated and absorbed into the cracks and fissures I repeatedly used  
> commercial cleaning solvents in a spray can, cleaning is one of the most 
> critical steps to success and must be done properly. Drying of the solvents will 
> be expedited with low heat for several hours. If the damage is severe you 
> will have to get the alignment of the parts correct, I carefully reassembled 
> the parts using masking tape on the armature to maintain some semblance of 
> alignment and clearance  also keeping a light pressure pushing the 
> castings toward each other. I then did the initial gluing followed a day later by 
> several more ses
> sions with the unit back apart. Here's the surprising thing, I used "Super 
> Glue" brand glue that I got from  "Big Lots" this is the kind in a tiny 
> 0.10 oz bottle with a yellow label and red fluted top. this glue (when new 
> and fresh) is extremely thin and has a penetrating and wetting action that is 
> ideal for filling spider web cracks in grainy, porous zinc. I let things 
> harden for a day and cleaned up the excess on the flanges with a file. When 
> I was done, I could suspend the bare casting on a piece of wire and could 
> hear it "ring" when tapped with a small screw driver. Houston: we have 
> integrity!
> The dynamotor was saved and runs fine.  Might work for you too, if not, 
> there's nothing much lost for the effort.
> 
> Steady as she goes Captain.
> Jim Solsbury.

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480