Author Topic: Two Cylinder Engine  (Read 69484 times)

Offline steam guy willy

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Re: Two Cylinder Engine
« Reply #75 on: August 19, 2018, 11:25:33 PM »
 hi Roger, ok Thanks, i shall endeavour to do that.........
Willy

Offline Roger B

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Re: Two Cylinder Engine
« Reply #76 on: August 26, 2018, 04:14:15 PM »
Next up is the connecting rod bearings. Both are made from RG7 bronze bar. The big ends were split in the mill using a 0.8mm thick slitting saw and then soft soldered back together. This piece was then mounted in the 4 jaw independent chuck and adjusted so that the split was on centre. I drilled and ream the bore before turning down the outside to reduce the chance of it cracking open (found out the hard way  :( )
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #77 on: August 26, 2018, 04:18:09 PM »
The finished bearings were melted apart with a electric soldering iron and the joint faces were cleaned up. It all fitted together  :) The little ends were drilled and reamed before turning to final size and were then pressed into the con rod. The reamer was put through again by hand to compensate for the interference fit.
Best regards

Roger

Online Kim

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Re: Two Cylinder Engine
« Reply #78 on: August 26, 2018, 05:24:03 PM »
Great work on the bearings Roger.
And very nice pics!
Kim

Offline Ye-Ole Steam Dude

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Re: Two Cylinder Engine
« Reply #79 on: August 26, 2018, 05:42:07 PM »
Beautiful work Roger.

Have a great day,
Thomas
Thomas

Offline Roger B

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Re: Two Cylinder Engine
« Reply #80 on: September 06, 2018, 05:56:43 PM »
Thank you both  :ThumbsUp:

I drilled and tapped a few more holes in the crankcase and then tried to assemble the crankshaft and conrods. Ooops I had forgotten to mill the clearance slots  :facepalm: On to the mill for a quick job with a 3mm end mill. It is now mostly ok but needs a little fettling as the design does not have much clearance.
The next problem to solve was the flywheel. When I first tried to install it the grub screws wouldn't hold. Checking again I found that I had used M3 instead of M4 and due to the two different materials, cast iron and free cutting steel, the holes had drifted inwards. I set it up on the RT and opened the clearance holes out with 4mm end mill and the tapped holes with a 3mm end mill. These were then opened out with a 3.2mm drill ready for tapping.
Best regards

Roger

Offline Ye-Ole Steam Dude

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Re: Two Cylinder Engine
« Reply #81 on: September 06, 2018, 06:05:41 PM »
Hey again Roger,

Your project is coming along nicely.

Have a great day,
Thomas
Thomas

Offline zeeprogrammer

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Re: Two Cylinder Engine
« Reply #82 on: September 06, 2018, 07:11:01 PM »
Following along.  :popcorn:
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Roger B

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Re: Two Cylinder Engine
« Reply #83 on: September 17, 2018, 07:38:46 PM »
Thank you both  :ThumbsUp:

The small holes were then tapped M4, the bush was turned 60° and the flywheel was fitted on a length of 10mm silver steel for a final skim. After a bit of fettling of the crankcase it was all fitted together and turns smoothly  :)

<a href="https://www.youtube.com/watch?v=0T2iuYGNzno" target="_blank">http://www.youtube.com/watch?v=0T2iuYGNzno</a>
Best regards

Roger

Offline crueby

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Re: Two Cylinder Engine
« Reply #84 on: September 17, 2018, 08:41:38 PM »
Very nice!
 :popcorn: :popcorn: :popcorn:

Offline Roger B

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Re: Two Cylinder Engine
« Reply #85 on: September 30, 2018, 07:52:59 AM »
Thank you Chris  :ThumbsUp:  :ThumbsUp:

The next step was to make a 20.15mm plug gauge for the cylinders ready for lapping. Both liners were lapped at the same time, the tighter one first. This was done as before with an Ezelap and (relatively) coarse diamond paste. When the plug gauge was a snug fit in both bores it all went into the ultrasonic bath for cleaning.

<a href="https://www.youtube.com/watch?v=i8Pz230FWx4" target="_blank">http://www.youtube.com/watch?v=i8Pz230FWx4</a>

The top of the cylinder block was marked out, drilled and tapped for the cylinder head fixings and water ways. I had previously bought a set of stub drills from Proxxon which certainly helped with head room and reduced deflection.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #86 on: October 06, 2018, 10:30:37 AM »
Next up was the pistons. These were turned from a length of 25mm aluminium. The outside was turned to 20.10mm, checked for fit in the liners and the recess was drilled and bored. Next the piston ring groove was cut, 0.9mm wide 1mm deep and the blank parted off.
To keep up the machining videos this was turning down the bar, 500 rpm, 1mm depth of cut with an aluminium insert from APT.

<a href="https://www.youtube.com/watch?v=ORm3tD_DF9E" target="_blank">http://www.youtube.com/watch?v=ORm3tD_DF9E</a>
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #87 on: October 06, 2018, 10:36:56 AM »
The piston blank was then set up in a vice on the Hobbymat mill to drill and ream the gudgeon pin hole and then moved to the RT on the Proxxon mill to machine out the little end cavity. The chart on the mill suggested 20 000 rpm for a 3mm cutter in aluminium but I ran at 8 000rpm with a 2mm depth of cut. Lots of swarf in a small hole  ::)
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #88 on: October 06, 2018, 10:42:24 AM »
There are a couple of design points still to think about:

1. Retaining the gudgeon (wrist) pin. I can use grub screws from below as before or I can fit brass/bronze end caps  :headscratch:

2. Retaining the liners. I could fix them in place with a Loctite product or fit an O ring at the bottom and assume I will be able to remove them later if I want to. I suspect that the cast iron and aluminium will corrode together so they will be as tightly held as if I had used Loctite  :headscratch:
Best regards

Roger

Offline fumopuc

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Re: Two Cylinder Engine
« Reply #89 on: October 06, 2018, 06:03:14 PM »
Hi Roger, I have used both ways to fix the wrist pins in the past. Now and in future I will prefer the brass pins. They can't get loose and block the crank drive.
And, good to have more than one mill.
Kind Regards
Achim

 

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