A Stuart Twin Oscillator

[Charles Lamont]

It's a bit late now, but I was going to suggest not filling with JB Weld but glueing in a brass plug and re-drilling. In my experience, trying to re-drill partly in epoxy and partly in surrounding metal (even aluminium) disnae wurrk. (You posted while I was typing.)

[Sanjay F]

Thanks Charles - yes, plugging is probably the best solution, but I've done what I done so let's see how that pans out and at least I have another route - all is not lost, but must admit it felt like it this afternoon! 

EDIT: I'll plug it tomorrow and re-drill, a far more satisfactory solution 

[Jasonb]

As the JBW is in there you could plunge with a small milling cutter, far less likely to wander than a drill. If it does not work you still have to machine out the JBW anyway and that too is best done with a plunged mill too.

If using that jig to position the new holes take a careful look at it, to me the top and bottom pairs of holes are not equally spaced.

All the small wobblers and the larger oscillating engines I have done have had the holes/slots positioned using the mill not a jig. To me the jigs date back to a time when few hobby shops had  a mill, a lathe being the only large machine which may have had to double up for drilling if you did not have a drill press or want to use a hand drill. If that is all you have then use a jig, if you have better options then use those.

Even if I were to make a jig, rather than marking out, punching, picking up the punch marks and drilling I get more accurate results using co-ordinated to use on the mill to position the holes. With calculators and a bit of trig or 2 or 3D CAD it has never been easier to work out hole positions.

[Sanjay F]

Thanks Jason that’s good info and I’m definitely looking at my ways of doing things rather than blindly following the build; there are too many errors and as I have discovered some of the operations are not exactly great.

However, I have plugged the holes and re drilled them and it looks a lot better and very much symmetrical to the other arm; I took a light skim off all surfaces so hopefully all is good now.

The cylinders are now bored and to the correct length so onwards and upwards with this little engine 🙂

[Sanjay F]

Any idea why the flux is drying out and not turning liquid? Have cleaned it off several times and just does the same thing?

I did bang the pegs in so maybe no gap but doesn’t explain it drying? I’ve cleaned it off with citric, not sure what to do?

[Jasonb]

Get it hotter, does not look like it has got hot enough to turn liquid. They bubble like that once the water has been burnt off and have the texture of sticky spit. Keep heating and it should flow as a clear liquid. The blobs of silver solder also suggest you are melting them in the flame and not on the metal.

This does not really go liquid all over until about 1.40 into the video

<a href="https://www.youtube.com/watch?v=EnTs7jx4Zc0" target="_blank">http://www.youtube.com/watch?v=EnTs7jx4Zc0</a>

[Sanjay F]

Well that's the thing I had the heat on for ages, it did its initial turning white and then solid, then just couldn't get it to run. I tested a bit of solder on the dried flux and it turned into a blob - very strange, I haven't had an issue with soldering in a little while.

Let me try again and apply more heat......

[crueby]

And as Jason said, you need to heat the metal and have the metal heat the solder/flux  - if the flame is directly on the flux/solder, you will burn off the flux before the metal is hot enough. If you are trying again, clean off the flux that is there and start fresh. If you don't get the metal hot quick enough, the solder will burn off some ingredients and not work properly. Could be you need a larger nozzle to heat the mass of metal faster too.

[Sanjay F]

Well that's odd the I tried a bit of scrap and that worked fine? Here's a video aof what I'm doing, maybe I need to heat the metal up more or maybe I do need a larger nozzle - anyone any idea what nozzle will suit the Sievert I have, I have been thinking about getting one anyjhow?

https://www.youtube.com/shorts/4WQhZxHTTTQ?feature=share

[Sanjay F]

Hooray, I wasn’t hearing the metal and heating the flux  - anyway looks better now, and lesson for the future, would still like a bigger nozzle though

[Jasonb]

The usual 28mm No2941 that comes with the handles will be more than adequate at 7.7kW

What regulator setting are you using? They want at least 2bar

EDIT just looked at the video. Your sq block is acting as a massive heat sink and sucking all the heat out of the casting. Also to a lesser extent it is raising it up so the walls of your hearth are nor bouncing back any heat where it is needed

[crueby]

One other thing - is this in an indoor shop? I'd never use a torch like that indoors, carbon monoxide from incomplete burning can be a real hazard, plus whatever fumes from the flux. But, glad you have it sorted! Agreed with what Jason said about the heat sink and more firebrick walls around the part to hold in more heat. I have a handful of different nozzles for my Seivert handle, the larger the part the larger nozzle I use, its surprising how much more is needed on a slightly larger part, especially with it attached to a block like that. Would not want to overheat a nice tooling block like that either!

[Sanjay F]

Thanks both, that been a great learning experience. I’ve taken a photo of the regulator (see below), but don’t know where I should set it?

My shop is indoors and you are right I shouldn’t be firing it up indoors, luckily its beautiful day so I have the garage door open to get some natural light but thanks for reminding me

I’m glad the standard is done, I finished it off by milling the tops of all the pegs flush; what a tricky little thing these oscillators are, but I must admit I like the design where the passages are hidden so no external pipe work twisting about or visible.

[Jasonb]

I would set that a bit above half way. You could even have it fully clockwise at 4bar

[Admiral_dk]

I REALLY hope that you did remove the part from your brand new Angle Block before heating ...!!!!!!!!!!

If NOT you are trying to destroy the Tool (ruining the hardening + accuracy) while it works as a VERY big Heat-Sink  :'(

Please tell me that I read the pictures wrong 

Best wishes

Per