Broken Vostok 2416b Oscillating Rotor

[JohnL]

Hi All,

Unfortunately I have discovered that a missing balance assembly wasn't the only issue with a recently purchased Vostok 2416b. I've attached a few photos showing the offending item. Any help and suggestions very much appreciated. Current thoughts (aside from getting a replacement) are completely separate the pivoting arm from it's weight, try and open up the folded edge on the groove in the weight. Clean all as much as possible, then join them back together with some sort of adhesive. 

By all means feel free to disabuse me of these ideas and put me on the right path.

John

[JohnL]

In light of the fact that nobody has berated me from a height for the temerity in suggesting using an adhesive to repair this, that's what I'll try and do. If it works I'll post pictures of any important steps and the result after the fact. If it doesn't well, maybe I'll just post a short message to that effect.

It does look like some form of adhesive was used before. If anyone would care to recommend what to use I'd appreciate it because I'm going to go with either CA or epoxy as they're what I happen to have. I don't have shellac and I don't currently have any of the Loctite thread lock adhesives.

[mikepilk]

It looks like someone has tried to press the edge down as a fix.

If you don't have Loctite, I seen no reason why you shouldn't glue it.

[watchweasol]

Hi. Same opinion as @mikepilk , the best stuff would be one of the loc5ite adhesives but failing that use what’s available.

[AndyGSi]

As others have said, I'd use superglue.

If possible and as you mentioned in your first post, you need to disassemble, straighten
and clean then make sure they fit back together correctly before trying to glue.

[rjenkinsgb]

How about cleaning the edge and groove, once the parts are separated, then adding a trace of solder paste in the groove before re-assembling it?

I'm not sure how safe it is to heat it to ~350'C though.

 

Alternative would be low melting point solder paste, eg. 

https://www.ebay.co.uk/itm/385050331282

 

Or, solder for white metal - 70'C melting point!

Use that with acid flux, then wash it very thoroughly. 

https://www.ebay.co.uk/itm/256451811844

[SwissSeiko]

A perfect opportunity to make a weight out of brass to replicate what G.O. is doing!

[JohnL]

Thank you all, that was a very pleasant surprise. 

Low temperature (138 C) soldering sounds like a nice solution, but my soldering skills pretty much prohibit it. I also prefer the idea of one of the stronger Loctite to standard CA, but I think 10ml of it is more expensive than a replacement rotor and it's unlikely to be used again. I think the use of Loctite is more likely to be assumed rather than solder if someone after me should look at it?

I will need to clean it (I'm hoping acetone will remove the gunk that's there), straighten it then get it back into the slot; the upper edge of which has, I think, what look like a number of shallow indentations suggesting an attempt at crimping. Not sure if that's the technically correct term. I don't think it's just that little bit folded down at the end that needs to be straightened.

"make a weight out of brass" don't have the equipment, don't have the skill. If I had both, then why not

[tomh207]

Soldering skills would not be a big deal if you use low temp solder paste, apply like glue then heat the parts with a heat gun until it all flows together. As others have said clean thoroughly after, IPA should get rid of the flux residue, often used in the electronics world for this.

 

Tom

[JohnL]

Separated the weight from the rotor.

Opened up the upper flange on the groove where it folded in, or crimped. I did that by putting a screwdriver tip in the slot and gently easing from one side of the fold, then the other, trying to keep the pressure on the lower flange at the back of the groove; at the tip of the screwdriver.

Dry fit

I then cleaned both parts with a fibreglass pen, just to make sure there was no crud.

I cleaned them with IPA. When doing the dry fit it wasn't easy to get the two ends to line up perfectly, the rotor arm would be slightly off to one side within the weight's groove. Even pressure was required so I lined it up in a case holder.

CA glue (yes, I know, but I don't have a staking set, and I'm not buying one to fix a ten dollar part) was then applied using a cheap oiler (smallest of them) with acetone on hand to clean it afterwards. I put the CA glue on a small square of tinfoil to use in a similar fashion to an oil pot. 

I then closed the clamp keeping slight downward pressure on the middle of the weight to stop it lifting. 

There's a tiny bit of squeeze-out, which I only saw when taking the photo, but I don't think it's going to affect things much. Looking on the positive side it will show anyone else that glue is present.

Should have remembered: The pressure points are slightly different being higher on the weight than on the rotor arm, slightly exacerbated by the slope on the clamp posts.

 

It's a nice tight joint on what is the underside of the rotor, facing upwards in the clamp, but it's opened slightly at the apex on the top face of the rotor. 

It's not bad at all, just could have been avoided. Low temp solder was the way to go.