Author Topic: Another Westbury Wyvern build  (Read 5106 times)

Offline Roger B

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Re: Another Westbury Wyvern build
« Reply #15 on: January 03, 2019, 11:02:55 AM »
Another interesting build to follow  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #16 on: January 03, 2019, 08:51:32 PM »
Thanks Dave and Roger, it's good to have you along.

Summer may slow down progress for a while (e.g. fishing, beach and the garden) so please be patient!

David

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #17 on: January 18, 2019, 01:19:46 AM »
Right - back from the beach and into the workshop.

Getting the bed plate squared up and to size looks like it's critical and everyone here tell me that these casting thingies aren't always quite what they should be. A careful check was needed:



Everything looked close to right and had enough (just) metal to get the part out of it, I missed seeing the only bit that was misplaced until later. The datum faces are going to be the underside and two edges of the bottom flange:



which involved a lot of careful clamp-juggling to keep the casting secure and get access for the cutter:



after turning the part over I could machine much more stable clamping surfaces on the top:



which allowed me to drill the securing stud holes - including one in the wrong place and the JBW'd plug is just visible here:



with the casting nested against a parallel clamped to the angle plate (it all has to be this way 'round to get the Y-axis travel needed, must look at a more flexible clamping system sometime) the cylinder mounting face was machined - note the bit of JBW where some of the earlier clamp-juggling failed:



Turned over yet again, but this time with stable and secure clamping surfaces available, I could clean up the inside edges. In an ideal world this would just be a quick filing job but the first error in the original drawings comes into play here. The width of this slot in the bed plate is shown as 1.5", exactly the width of the crank webs that have to turn in the slot (the original GA has the slot drawn with some useful clearance), so I opened this up to 1.625" with a boring head and then the cutter here:



Yet another inversion allows the sides of the main bearing flanges to be brought to size and here I found the only "error" in the casting - one side was displaced ~1/16" towards the centre line and the far side didn't clean up completely. This doesn't look like causing any real problems with the bearing's lateral location, if it does then it's back to the JBW and a bit more machining. Dental mirrors can be very useful things as well:



The last operation (for this post) was to face off the main bearing split line ready to fit the bearing caps. I thought the setting the 30 degree angle by the scale on the Aciera table was sufficiently precise:



If I'd thought this through properly I'd have clamped up the part before tilting the table, otherwise you need four hands to fiddle everything into place. This stays set up until the holes are drilled for the bearing caps.

David



Offline b.lindsey

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Re: Another Westbury Wyvern build
« Reply #18 on: January 18, 2019, 02:27:48 AM »
Hope the beach was enjoyable David. Nice to have you back too though and in the shop again.

Bill

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #19 on: January 18, 2019, 03:08:59 AM »
Thanks Bill, it was. My late father-in-law bought the land around 1955 and he and a couple of mates built the house over the next few years. There's a dirt road across the front then the creek and beach (below at sunset):



David

Offline steamer

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Re: Another Westbury Wyvern build
« Reply #20 on: January 18, 2019, 03:55:53 AM »
Nice Set ups!    Gotta love the Aciera!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #21 on: January 27, 2019, 11:02:08 AM »
Yes Dave, the F3 is going to star again a bit later!

The main bearing caps come as a single casting and I did as much machining as I could with them still together. After a quick clean-up with a file they were fixed upside down on parallels to mill a clean under surface:



then turned over and the surfaces for the securing nuts milled to thickness:



followed by one end as a reference face (still well outside the finished dimension):



the fore-and-aft centre lines of the lubricator bosses were found by eye and the fixing holes drilled and counter bored on those:



Now the caps were sawn apart, fixed to the baseplate and carefully machined to width. One of the critical bits of alignment in the whole build comes next - getting the crankshaft centre line bang on to the bearing split line and also getting the cylinder mounting hole centre at the same height. Here is another of the Aciera's many clever features, it's easy to turn the vertical head through 90 degrees and use the X-direction power feed for drilling and boring:



After marking out on the surface plate I used a needle and magnifier to pick up the CL of the crankshaft using the Y- and Z-feeds to adjust the position. The sine vice is just there because, for once, its height is an advantage and gives some necessary vertical clearance. Turn the vice through 90 degrees and the cylinder mounting hole can be drilled and bored:





Dave's right:
Gotta love the Aciera!

With everything back to "normal" the tops of the lubricator bosses were milled off flat:



Now I have to comment on the quality of the four alli castings that I've machined from this set so far. All have had a lot of small pores right through them, not enough to affect the strength but irritating all the same. Here is a macro shot of the main bearing stand bore:



While boring the cylinder mounting hole the freshly re-ground carbide tip went blunt (couldn't believe it at first and scratched my head for a while wonder what the heck was going wrong). I think now that some of those pores must have had sand in them - OK it was a cheap boring bare but these deal easily with cast iron...
I don't have much experience (almost none) with castings and I'd like to know how common this is guys?

David

Offline Jasonb

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Re: Another Westbury Wyvern build
« Reply #22 on: January 27, 2019, 12:32:03 PM »
Graham is the one to know but could be oxide rather than sand, if you can dig some out and the grains are much finer than you would expect for sand then it is Oxide. As you know Aluminium Oxide is used as an abrasive.

I recently had some phosphor oxide in some bronze castings that instantly took the edge off an HSS tool and I don't think my bandsaw is cutting as well since cutting the casting in two >:(

Offline RayW

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Re: Another Westbury Wyvern build
« Reply #23 on: January 27, 2019, 03:23:12 PM »
Hi David,

I definitely can't recall having that problem when I built my Wyvern. I think there may have been the odd minor imperfection in the castings, but nothing that caused me any problems. Looks like you may have just been unlucky and got a rogue casting.

Ray

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #24 on: January 31, 2019, 10:46:49 AM »
Thanks Jason, your suggestion of aluminium oxide in the casting makes more sense than simple casting sand. I haven't been able to find anything in the pores but there are a heck of a lot of of them. If another tool goes blunt I'll stop and take a good look.

Hopefully the rest of the castings are more like Ray's batch!

David

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #25 on: February 17, 2019, 07:34:33 AM »
The next bits of the Wyvern are the crankshaft and main bearings. The bearings are plain turning from bronze bar - no pictures of the set-ups but the bits will appear in later shots. The crank webs were turned from 3" FCMS blank, first brought to thickness and the central hole drilled, bored and reamed. The outside diameters were finished with the webs on an expanding mandrel:



The 2" - 3" micrometer doesn't come out of the box very often but it allowed me to get the two parts very close to the same size.

With the two webs stacked up, located by two V-blocks, and the central hole aligned to the mill axis the pair were offset for the crank throw and the crank pin holes reamed:



Web drawings were printed 1:1 and stuck to the blanks with spray adhesive so the shapes could be roughed out on the bandsaw. Bits of 1/2" PGMS served to align things in the vice and the faces cleaned up:




OK, a ruler dimension might have been good enough for the shaft length but I'm fussy. My slide calipers are only 6" capacity so another way was needed and this made me think (always useful) but for longer than it should have - once you have a DRO then you can measure anything up to the machine travel lengths. Zero the X display with the bit of bar against the top of the angle plate then off you go:



The crank pin is plain turning and the ends of the shaft needed reducing to 3/8" and threading:



Before getting out the Loctite 638 the bits were:



and the finished part looks like:



I'd spent a lot of time filling, rubbing down and painting (rattle can enamel called "Indian Red") and the project now looks like:



I copied tangler's idea and prevented the main bearings from rotating in the housings with 6BA CH screws and you can see that I also made the studs for the base:



I guess the cylinder liner and water jacket are next...

David

Offline Johnmcc69

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Re: Another Westbury Wyvern build
« Reply #26 on: February 17, 2019, 10:47:42 AM »
 :ThumbsUp:
Looking good David!
 A great build thread to follow.

 John

Offline b.lindsey

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Re: Another Westbury Wyvern build
« Reply #27 on: February 17, 2019, 02:20:37 PM »
That crankshaft is beautiful David. The whole project is coming along well!!

Bill

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #28 on: February 24, 2019, 12:35:06 AM »
Bill and John, Thanks for the encouragement!

The crankshaft needs two nuts and washers, 17 mm AF hex and 3/8 x 26 thread. I was going to make the thread M10x1.0 but that meant that the core of the crankshaft timing gear would be rather thin so I went back to the Imperial thread. First I needed some hex bar the right size:



The washers and nuts were plain turning and there was enough material for spare nuts so I made four of those:



I'll describe the cylinder liner and water jacket in the next post, right now the water jacket and bed plate are ready for their next coat of paint - "after 1 hour and before 2" are the instructions on the rattle can for re-coating.

David

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #29 on: February 24, 2019, 08:03:52 AM »
Next drawing:



and a link to the .pdf of this: https://1drv.ms/u/s!AnNmmwsT2XIilTYKTFN2ID3Ndlbz

The cylinder liner was from a length of continuously-cast iron, lovely stuff to machine if you don't mind the mess. The outside diameter and one end were finish machined, the OD being made a close sliding fit in the water jacket (next post):



Then, with the material supported by a fixed steady, an extra-long series drill used to start the bore (the extreme length obviously isn't needed, I just don't have anything in between):



followed up with my largest drill (21 mm):



which made lots of swarf in little curls that were interesting shapes:



I thought that these deserved a closer look:



and



Boring the liner to finished size was a nightmare; cast iron steady tips running on the cast surface generated a surprising (to me...) amount of heat and I changed from  ordinary lube oil to a moly-disulphide grease that solved the problem. At first there was no combination of tip, feed and speed that didn't result in horrible chatter. As the bore got bigger I added layers of lead sheet to deaden the boring bar (16 mm diameter) and after four layers this had the necessary effect. The result is ugly but effective:



and gave an acceptable finish which feels better than it looks (original image was 1:1 with a macro lens on a camera with 4032 pixels across):



With the steady removed the parting-off was easy:



The stub of CI  in the chuck was turned and bored to size for piston rings and I got three out of the bit:



I've run a small cylinder hone through and this smoothed off the finish to the feel without apparently changing its appearance but I'm reluctant to do much more for fear of affecting the diameter which is parallel to as well as I can measure it.

Next the water jacket which was actually machined in parallel with the liner but that makes the story way too complicated.

Regards, David

Edit 2019-03-28: Added missing drawing and links DT
« Last Edit: March 28, 2019, 02:35:19 AM by deltatango »