Author Topic: Twin Oscillators  (Read 5788 times)

Offline K.B.C

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Re: Twin Oscillators
« Reply #15 on: April 17, 2019, 08:00:07 AM »
Hi JO,
Yes the cylinder castings were so out of line and under size.
I have made several of these engines and after my first set of casting being so bad I now only buy the standard and make the cylinders from stock material.
The engine at 9/16" bore x 5/8 Stroke are so powerful that on 30 p.s.i. you can't stall the engine by grabbing the main shaft, all that you do is friction burn your fingers.

Jason,

like all oscillators they run a bit wet and I can't say that I have noticed less condensate but I like the modified pipe runs.

George.
Your never too old to learn.

Offline Jo

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Re: Twin Oscillators
« Reply #16 on: April 17, 2019, 03:51:57 PM »
The cylinders were mounted on a mandrel for the remaining operations:

First was to turn the ends and the outside. You can see the nature of the gunmetal the cylinders are made of by the burr still hanging on on the end hoping to cut someone's fingers   :paranoia: Yes the casting was undersized so the ends have been turned 23mm rather than the 23.8mm of the covers - that was clearly intentional to leave space for a cylinder jacket   :-X

There wasn't much spare on the sides of the cylinder pivoting surface but there was plenty on the depth - which was needed as it had been cut off at a jaunty angle. Drilling the port holes had to be done carefully to avoid going into the bore of the cylinder - Thankfully the mandrel supports the inside and reduces the risk of the gunmetal being pushed down.

The cylinder could then have the steam port drilled down to meet the other hole, the cover holes drilled and a 1.2mm deep pocket so the steam can get into the end of the cylinder.

Two Cylinders  :)

Jo
Usus est optimum magister

Offline Johnmcc69

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Re: Twin Oscillators
« Reply #17 on: April 17, 2019, 06:16:18 PM »
Those are some nice plumbing/valving ideas.

 Nice work on those cylinders Jo!

 John

Offline Dave Otto

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Re: Twin Oscillators
« Reply #18 on: April 18, 2019, 01:11:58 AM »
Nice work Jo!

Dave

Offline Jo

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Re: Twin Oscillators
« Reply #19 on: April 18, 2019, 11:39:18 AM »
Thanks Guys  :)

I was a little worried about how to hold the stand but like the cylinders, after a quick fettle, it is designed to be initially held in the three jaw chuck  :ThumbsUp:

Having faced the centre and centre drilled it was possible to safely face the port faces and then drill/ream for the crank.  Turning round and mounting on an arbor the other end by the crankshaft could also be faced.

Now I just need to work out how to hold it to do the next bit  :noidea:

Jo
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Offline Ramon

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Re: Twin Oscillators
« Reply #20 on: April 18, 2019, 01:10:40 PM »
Now I just need to work out how to hold it to do the next bit  :noidea:

This any help Jo ?



Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Jo

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Re: Twin Oscillators
« Reply #21 on: April 18, 2019, 04:02:58 PM »
Thanks Tug  :ThumbsUp:

Like you I realised I had to start by squaring up the base of the casting to give me a reference. To be able to hold the top of the casting in a vice  :-X I clamped the casting face first onto the BCA bed and milled the back of the pivot blocks so that they were parallel to the front. Having clamped it in the vice The base was flycut and the last three sides squared up.

The next trick was to look to get the centre of the crank in the centre of the BCA table  :thinking: I chose to do this by finding a really long Allen screw (which I found was 1/4 UNF  :facepalm: ) and making a long nut that went into an existing BCA table collet.

A few hours later (the sun is also out which means the garden is very nice to spend time in  ::) ) and the Engine Standard is mounted in the centre of the BCA table, square with the angle measurements on the rotating table, ready for milling in the morning. In the meantime I am hoping Surus considers that this is sufficient progress for today to allow us to participate in a little casting fondling this evening :wine1:

Jo
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Offline Jo

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Re: Twin Oscillators
« Reply #22 on: April 19, 2019, 03:58:58 PM »
With a little jiggling around I managed to get the casting such that there was almost nothing to come off on the two insides of the bearings face and almost an equal extra on the two outsides, which was then milled off. The flat was milled across the centre of the face and then the holes drilled 6.5mm deep.

That was the easy bit: Having marked off the holes that needed to be drilled for the internal porting it was time to realise that the hole from the top is more than just a long hole, it is a very long hole relative to the drill diameter  :paranoia: To play safe I chose to start with a shorter very sharp PCB drill and finish off with a brand new dormer drill. The vice is there to make sure everything is truly square before starting to drill. The ones on the side were much less stressful to drill. A poke with a drill down each hole proved that they all join up where they should  :)

Finally time to check it the bits go together  :wine1:

Jo

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Offline Bluechip

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Re: Twin Oscillators
« Reply #23 on: April 19, 2019, 05:39:24 PM »
Hi Jo

Looks like it's gone together OK ...  :ThumbsUp:

So what's the finish? Crack a bit of filler in the holes and a slosh of paint ?

Thought you'd have been out in the garden culturing your horties today.

My toms are in their final pots and seem to be thriving.  ;D
Fence panel and other stuff came this AM .. Was going to rip down the crap and convert into firewood for you .. except I was expecting a delivery from CPC and hung about doing nowt so UPS would not have to go searching for me. Thought they were getting a bit late then I saw the tracking ...... Delivery by end of day ..TUESDAY 23rd  ... bugger .....  :headscratch: :old:  Another day I won't get back.  :paranoia:

Dave
 

Offline Jo

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Re: Twin Oscillators
« Reply #24 on: April 19, 2019, 06:00:16 PM »
Thanks Dave  :)

I haven't decided on the finish: I normally avoid polished brass engines but paint  :toilet_claw:


The garden has been good today. My Toms are behind yours  :-\ I have two Cues in their final pots but am running out of space in the Conservatory as the triffids Courgettes are attempting world take over  :facepalm: Any amount of firewood is always welcome  :cheers:

I am still trying to work out where all the extra spare time went now that I am retired  :noidea:

Jo
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Offline Jasonb

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Re: Twin Oscillators
« Reply #25 on: April 24, 2019, 08:05:52 PM »
Any more progress on this one Jo or are you still to busy polishing off all those chocolate eggs?

Offline Jo

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Re: Twin Oscillators
« Reply #26 on: April 24, 2019, 08:28:43 PM »
Yes thank you  ;D

There were no eggs round here  :disappointed:

Jo
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Offline b.lindsey

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Re: Twin Oscillators
« Reply #27 on: April 24, 2019, 10:51:46 PM »
Had totally missed this one Jo, and now it's almost finished. Looks great though, Surus' should be pleased.

Bill

Offline Jo

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Re: Twin Oscillators
« Reply #28 on: April 25, 2019, 07:09:53 AM »
It is nearly finished Bill a little more fitting and a bit of plagiarism  ::) and I should be in a position to show some more photos.

Hopefully that will be today... if I have time  :embarassed:

Jo
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Offline Jo

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Re: Twin Oscillators
« Reply #29 on: April 28, 2019, 03:10:10 PM »
The two piston rods have big ends that have to be fitted together so I started by making up the two big ends and checking the fit. The rods and pistons are simple turnings. It gets tricky when the big ends have to be fitted to the piston rods and any amount of silver solder left on the rod is took much as when the crank goes round the big end gets very close to the gland, it took a bit of fitting to get them to miss.

Having decided to commit blatant plagiarism (thank you George  ;) ) it was time to knock up the reversing block. This was made in two halves of brass from the scrap bin.

The last task on the stand was to block up the unnecessary holes that were used to drill the ports, clearly a task for that nasty all thread studding stuff that some people think is suitable for engine studs  :hellno:

The steam lines were made from some 1/8" O/D copper tube that it was only after I had finished bending them did I find out that some of the tube was blocked and had to be poked clear  :facepalm:

Finally all fluxed up ready to be soft soldered together  :)

Jo
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