Author Topic: JC attempts the MEM Corliss  (Read 26872 times)

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #75 on: June 07, 2021, 10:17:51 AM »
I decided to machine the covers on the lathe.

To support the material in the four yaw chuck, I first machined a plywood insert of appropriate thickness for the chuck, using my 3 axis cnc router.



With the material clocked into position in the four yaw chuck, I drilled a centre hole to use the live tail stock centre as extra support.



Probably not the fastest approach to do this on the lathe, but it worked out well in the end.



With all the holes drilled, I could not resist assembling all the bits and pieces to see what it looks like so far.



Next will be the crosshead guide. This will give me all the reference diameters for the front cylinder cover, to hopefully ensure accurate alignment between the crosshead guide and the cylinder.

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Online crueby

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Re: JC attempts the MEM Corliss
« Reply #76 on: June 07, 2021, 01:00:55 PM »
Congratulations on the engine block - looks terrific!

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #77 on: June 13, 2021, 10:43:08 AM »
Thanks Crueby!

I started out with a a 50mm diameter chunk of mild steel for the crosshead guide. I first bored out a large enough hole for the chuck side, so that I will not have to deal with a blind hole when boring the through hole.

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I then turned the workpiece around and step drilled and bored the through hole leaving it about 1 mm undersize. Fortunately the boring bar I made for the cylinder, is just long enough to bore the guide.

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I then turned the OD 1 mm oversize, to allow for any movement in the steel, as was suggested to Vince many moons ago.



After bringing the ID, OD and flange diameter to final dimension, the guide was parted off. I then turned it around and clocked it in the four yaw chuck, before carefully finishing the flange.



The bore was quite rough and measurably tapered, so I made a lapping tool similar to the one used for the cylinder, and lapped the bore to be smooth and parallel.





I also made a small brass test piece to check the bore. It slides smoothly from side to side. I will use the test piece again once the guide is complete.



The four yaw chuck was used to hold the guide on the milling machine, and the PCD function of the DRO used to drill the eight mounting holes in the flange.



I mounted the vice sideways on the milling machine, and then clamped and clocked the guide to mill the slots with the aid of my X-axis power feed.



After step drilling the two 15 mm holes at the ends of the slot, a 15 mm slot drill was used. The material in between the two holes was then removed with a 10 mm end mill.  I was so absorbed by the whole operation that I forgot to take any pictures!

After a bit of deburring, filing and sanding, the crosshead guide is ready to receive the crosshead! And the brass test piece still slides smoothly backwards and forwards. Hopefully the crosshead will do the same!


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Offline RReid

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Re: JC attempts the MEM Corliss
« Reply #78 on: June 13, 2021, 02:50:07 PM »
Quote
I was so absorbed by the whole operation that I forgot to take any pictures!

Hah! - I do that more often than not! I suspect others keep a camera taped to the forehead with the shutter linked to their eye blinks.

Multi step operations like that are often the most fun and interesting I think, both to do and to read about. That guide looks like it came out very well, and your photos and descriptions are really quite clear and concise.

Regards,
Ron

Online Kim

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Re: JC attempts the MEM Corliss
« Reply #79 on: June 13, 2021, 04:43:54 PM »
Nice work on the cross head guide!  It looks terrific!   :ThumbsUp: :popcorn:
Kim

Offline Don1966

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Re: JC attempts the MEM Corliss
« Reply #80 on: June 13, 2021, 06:57:05 PM »
Awesome work ……… :Love:


 :cheers:
Don

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #81 on: June 28, 2021, 07:56:03 PM »
Thanks Ron, Kim & Don for the kind comments. Much appreciated in these times of lockdown and social distancing!

With the crosshead guide completed, I decided to make and fit the crosshead. I turned it to the same diameter as the previous test piece, drilled and tapped the hole for the piston rod and then finished it off on the milling machine.

First time I could use  one of my newly acquired collet blocks.









Quite happy with how the crosshead slides in its guide.
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Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #82 on: June 28, 2021, 09:33:05 PM »
The design of the rear cylinder cover was modified slightly for an o-ring as gland packing.



Note the bosses on both sides of the cover, for precise alignment of the cylinder and the cross head guide.

The gland nut was made first. Since a standard M10 thread is quite coarse, I decided to single point cut a finer (non standard) thread on the lathe. I have never done any thread cutting before, so some Youtube research was in order.

I like the idea to turn the lathe by hand, as suggested by Steve Jordan:

[youtube1]https://youtu.be/ksCd9FfjUFQ[/youtube1]
So I first had to make a crank handle. A few trial external and internal threads were then cut using carbide inserts. The top slide was set at 60 deg, and a DTI used to monitor thread depth, as suggested by Blondihacks:

[youtube1]https://youtu.be/q7scadYptTI[/youtube1]

After also watching some of Joe Pieczynski's excellent videos on thread cutting, it turned out to be a fairly straight forward operation.

After preparing and cutting the gland nut thread, the hex head was milled using a hexagonal collet block.







Next up was the rear cylinder cover. The internal thread for the gland nut was cut after turning the undercut for the o-ring.



The internal thread was enlarged gradually until the gland nut screwed in snugly.



The gland nut was then parted off and the outside of the rear cylinder cover completed. The 6mm hole for the piston rod was bored out using one tip of a 4mm end mill. The hole was bored slightly oversize to allow free movement of the piston rod.



The cylinder cover was then parted off and turned around in the four yaw chuck to machine the cylinder boss.



With the eight mounting holes drilled, it was time to assemble everything and see how well the crosshead slides with the stainless steel piston rod in place.



The crosshead slides smoothly! Everything seems nicely aligned. I hope I can say the same once the piston and o-rings are also in place!
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Online crueby

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Re: JC attempts the MEM Corliss
« Reply #83 on: June 28, 2021, 10:18:41 PM »
Coming along fantastically - great work!
 :popcorn: :popcorn: :popcorn:

Offline gbritnell

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Re: JC attempts the MEM Corliss
« Reply #84 on: June 29, 2021, 11:59:28 AM »
Looks great!
Talent unshared is talent wasted.

Offline RReid

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Re: JC attempts the MEM Corliss
« Reply #85 on: June 29, 2021, 02:37:22 PM »
That's really looking the part! :ThumbsUp:
Regards,
Ron

Offline propforward

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Re: JC attempts the MEM Corliss
« Reply #86 on: June 29, 2021, 05:55:50 PM »
Excellent work here. Great job.
Stuart

Forging ahead regardless.

Offline JCvdW

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Re: JC attempts the MEM Corliss
« Reply #87 on: July 10, 2021, 07:29:11 AM »
Thanks for the encouragement and kind words guys!

The piston was made out of mild steel, as the O-ring should prevent it from touching the cylinder. The piston has about 50 micron clearance in the cylinder.

After researching O-rings a bit, I decided to go for about 10% compression of the ring between the OD of the groove and the ID of the cylinder, and about 20% clearance for the width of the groove. The O-ring has a cross-section of 1.5 mm, with 24mm ID.

I started by machining a sacrificial outside groove to the the same depth as the final groove, as it is easier to measure with a micrometer. Noting the DRO reading of the cross slide, I could then easily cut the actual groove to the same dimension.



After drilling and boring the hole for the piston rod, the sacrificial groove was removed and the piston parted off. I flipped it around in the four yaw chuck, and cleaned up the face. A small groove marks this side as 'inaccurate' relative to the hole, and hence to be the side for the piston rod bolt.



The piston rod was clocked up in the four yaw chuck and machined down to match the hole in the piston. After threading for an M4 bolt, the piston was mounted. With less than 20 microns run-out, I am quite happy.
 




Time to check the alignment of the piston, rod and crosshead relative to the cylinder and cross head guide. I fitted the piston O-ring and installed the piston assembly. The motion is smooth, with constant resistance throughout the stroke, so the alignment seems good!

The O-ring has quite a bit of friction inside the cylinder though. I cannot move the piston by simply blowing on one side of the cylinder while closing the relevant steam ports. Not sure if this a valid test. I will increase the O-ring groove depth later if needed once I can apply compressed air to the engine.
« Last Edit: July 10, 2021, 08:02:29 AM by JCvdW »
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Offline vcutajar

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Re: JC attempts the MEM Corliss
« Reply #88 on: July 10, 2021, 11:58:35 AM »
Quote
The O-ring has quite a bit of friction inside the cylinder though.

I guess that is a side effect of using an O ring.   I used a graphite impregnated yarn (can't remember the proper name for it) instead.  I remember that when I did my first run this yarn was not used (also no gaskets) but the Corliss still ran beautifully.

<a href="https://www.youtube.com/watch?v=GjaW1frBMk0" target="_blank">http://www.youtube.com/watch?v=GjaW1frBMk0</a>

Vince

Online crueby

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Re: JC attempts the MEM Corliss
« Reply #89 on: July 10, 2021, 02:26:19 PM »
Some oil will let the o ring slide easier too.

 

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