Author Topic: JC attempts the MEM Corliss  (Read 26866 times)

Offline EricB

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Re: JC attempts the MEM Corliss
« Reply #60 on: May 14, 2021, 06:06:25 PM »
Great work! Thanks for posting Joe Pie's video too. Now I know what new tools I need to make to help with my tapping struggles.  :whoohoo:

Eric

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #61 on: May 20, 2021, 09:30:02 PM »
Thanks Eric. The small tap wrench certainly helps to feel the tap resistance, and when to clean out swarf. I magnetised a 1.5 drill bit for this purpose. However, I still managed to break an intermediate M2 tap! With this particular make of tap I could not really use the first tap in the set, and I think the intermediate tap was getting blunt and fatigued.

After some agony, I managed to mill out the broken tap with a carbide 1.5 ball nose cutter, without causing any noticeable damage.  Disaster averted!

I then bought a German set of M2 taps, which is definitely of a better quality. With this set I can use all three taps, with less strain on each tap.

Today I finished drilling and tapping the 32 M2 holes for the valve bonnets. With all the M2 holes out of the way, I feel a bit more confident about all the remaining holes in the cylinder block.



It is time to lap the cylinder and then make the front cylinder cover.
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Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #62 on: May 24, 2021, 05:05:53 PM »
I tried to lap the cylinder as before, using the lapping tool described previously. But try as I might, I could just not get the same finish on the cylinder bore again. After a lot of fiddling around, I decided to look back at my previous post. The secret was a bit of polishing compound!. Applied polishing compound - and the finish is much better. I am going to assume that this will be good enough for teflon piston rings.



After studying the excellent build threads of Arnold and Vince (again!), I drilled and tapped the holes for the front cylinder cover using the PCD function of the DRO.



I then turned the front cylinder cover, making sure that it fits snugly in the cylinder bore.



I located and drilled one of the 3mm through holes and then bolted the cover to the block to spot drill the other seven holes.



Quite happy with the final result. I always find a completed subassembly very motivating to carry on...



Looking ahead, I am wondering what the purpose is of the gland nut that screws into the rear cylinder cover?

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Offline crueby

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Re: JC attempts the MEM Corliss
« Reply #63 on: May 24, 2021, 05:13:00 PM »
Great results on the lapping, that should do very well. Excellent progress overall!
 :popcorn: :popcorn: :popcorn:

Offline EricB

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Re: JC attempts the MEM Corliss
« Reply #64 on: May 24, 2021, 08:49:40 PM »

Looking ahead, I am wondering what the purpose is of the gland nut that screws into the rear cylinder cover?

The gland nut holds the seal in place for the piston rod.

Eric

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #65 on: May 29, 2021, 12:32:57 PM »
Thanks for the feedback crueby & Eric!

Vince mentioned in his build threat that he adjusted some of the M3 hole locations on the cylinder block to allow for better nut placement. I followed his approach and modified the size and hole positions for the front cylinder cover. He mentioned similar changes for the cover plates.

All these small changes to the original metric plans started to bother me. After all the machining already done on the cylinder block, I want to avoid drilling a hole in the wrong location at all cost.

So I decided to first model the cylinder block and all its attachments in Autodesk Fusion 360. A software model is after all much more forgiving when putting a hole in the wrong place! The model also allows me to see how the engine will eventually look with standard M2 and M3 nuts and washers.



An interactive version of the model can be found here: https://a360.co/3p3kaKt

I hope that I can find the correct size DIN 433 M3 washers locally. The freely available M3 washers are a bit oversize, with an outside diameter of 6.8mm, in stead of 6.0mm.
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Offline vcutajar

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Re: JC attempts the MEM Corliss
« Reply #66 on: May 29, 2021, 02:10:52 PM »
Hi JC

I received your PM.  I have a habit of changing the size of the nuts and bolts primarily because I think they might look better.  At that time I used standard size nuts and bolts but now I know that there are model size nuts and bolts which look even better.

https://knupfer.info/shop/index.php/deutsch/modellmuttern/va-a2-niro/402-30.html

As for washers, I used DIN 433 washers which are smaller than standard size washers which I got from the UK.

https://www.westfieldfasteners.co.uk/Metric-Washers/For-Cheesehead-Washer-M3-A2-Stainless.html

I don't remember exactly why I might have changed the position of the bolt holes.  If it was for an important reason I might have mentioned it in my build log.  The only reason I can think of is that I might have been worried that some of the bolt holes would be breaking into the valve holes.

That's a great looking 3D model of the cylinder.  I have 3D modelled my Kiwi and also the Monitor steam engine in Fusion 360 but for some reason not the Corliss.

Sorry if I wasn't a great help in my reply to your PM.

Vince

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #67 on: May 29, 2021, 04:40:44 PM »
Hi Vince

Thanks very much for your quick response to my PM!

You helped me a lot. Using the Knupfer nuts certainly looks much better.



Now I have to deal with the EUR/ZAR exchange rate!  :'(
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Offline vcutajar

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Re: JC attempts the MEM Corliss
« Reply #68 on: May 29, 2021, 04:56:35 PM »
I think on the knupfer homepage they are saying that they will be on holiday from the first of June till the sixteenth of June.

Vince

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #69 on: June 01, 2021, 08:40:26 PM »
All 84 holes in the cylinder block drilled and tapped!  :whoohoo:



Now only the steam pockets left to mill, then the cylinder block will be complete. But somewhere in the future there are still 84 studs waiting to be made...
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Offline Admiral_dk

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Re: JC attempts the MEM Corliss
« Reply #70 on: June 01, 2021, 10:49:37 PM »
That is a major milestone - all those holes and threads in the right places and no major mishaps  :ThumbsUp:

Offline crueby

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Re: JC attempts the MEM Corliss
« Reply #71 on: June 01, 2021, 11:10:44 PM »
Terrific! Great spot to sit back and admire your work!

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #72 on: June 04, 2021, 05:03:38 PM »
Thanks Crueby and Admiral_dk! I thought I should first complete the engine block before sitting back, so today I milled the two pockets for the steam ports. Now the cylinder block is truely complete!

I started by plunge milling with a 10mm cutter, and then finished off with a new 7mm cutter that I had. Really enjoyed my X-axis power feed on the mill today.




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Offline RReid

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Re: JC attempts the MEM Corliss
« Reply #73 on: June 04, 2021, 08:30:50 PM »
That is one serious hunka metal. Obviously lots of work, and very nicely done.
Regards,
Ron

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #74 on: June 05, 2021, 11:23:49 AM »
Thanks Roland! Yes at some point I started to doubt whether I will ever see the cylinder block completed!.

I started on the steam port covers by squaring off two pieces of 6mm BMS, making sure that  both are exactly the same length as the cylinder block.



Not sure yet if this is a task for the lathe or the rotary table on the milling machine.
There is no planet B ...

 

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