Author Topic: Another Westbury Wyvern build  (Read 4020 times)

Offline Admiral_dk

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Re: Another Westbury Wyvern build
« Reply #45 on: March 07, 2019, 11:20:07 AM »
Nice family shot and the piston looks good too - keep up the fine work  :cheers:

Offline Roger B

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Re: Another Westbury Wyvern build
« Reply #46 on: March 13, 2019, 02:31:09 PM »
Excellent progress  :praise2:  :wine1:

Tjark had a problem with a porous piston crown on his Kiwi that leaked sufficiently to lose compression. Hopefully yours is not so bad.
Best regards

Roger

Offline b.lindsey

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Re: Another Westbury Wyvern build
« Reply #47 on: March 13, 2019, 02:39:26 PM »
Still following along here too David. Had missed a few posts so nice to see the excellent progress being made.

Bill

Offline Tjark

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Re: Another Westbury Wyvern build
« Reply #48 on: March 13, 2019, 06:33:27 PM »
Roger is right, i had problems with a casted piston.
One small inclusion, almost not visible caused a lot off problems.
Have made one out off solid bar and this worked well.
David, by the way the engine is very good looking so far.
Hoop you will have no trouble running the engine.


    Tjark.
« Last Edit: March 13, 2019, 06:38:52 PM by Tjark »

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #49 on: March 14, 2019, 12:03:31 PM »
Thanks everyone! Particularly for the info re Tjark's problem piston. I hadn't considered that a pore, or a series of connected pores, might make a track through the crown. A layer of JB Weld on the inside of the piston crown might prevent leaks and add strength, wouldn't be hard to do either.

David

Offline derekwarner_decoy

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Re: Another Westbury Wyvern build
« Reply #50 on: March 15, 2019, 04:50:01 AM »
David....simple open poured casting in aluminium is prone for defect due to porosity [entrapped air bubble during the pour]

This is not so important with structural or mechanical components, yes where a localisation plastic metal repair be effected

Having said this, any defect [in a component subjected to any pressure] established during preliminary machining should best render the casting as defective

Return to manufacturer or machine from Grade quality referenced bar stock which has far higher mechanical strength and machinability

Would be terrible to progress a piston with a defect.......add plastic metal to the piston internals underneath the  crown.......only to have a steam bypass  :zap: some time after completion of the engine

Derek
« Last Edit: March 15, 2019, 04:53:22 AM by derekwarner_decoy »
Derek Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #51 on: March 17, 2019, 01:09:54 AM »
Thanks Derek, I've put away the JBW! Without any guarantee that a new casting would be any better, machining from the solid will be the way to go.

Next drawing:



and the .pdf is at: https://1drv.ms/b/s!AnNmmwsT2XIilTND5H63TKsxS3t6

The next part is the cylinder head which is a complex shape with a lot of surfaces to machine. The casting had a rough finish with small bits of the fins missing so the first job was filling (JBW) and filing to removed the worst of the surface defects. Then I gripped the chucking stub in a my biggest tailstock drill chuck and presented it to the 4-jaw for clamping:



and cleaned up the chucking stub:



so that the casting could be held in a collet to level the underside and machine out the combustion chamber as well as forming the important recess that clamps and seals to the top of the cylinder liner to dimension:



With the underside machined this was pressed down onto parallels and the stud holes drilled and counterbored:



I then made the studs and checked the fit of those and that the recess was just shallow enough to seal:



The paint on the water jacket turned out to be slightly soft (too thick a coat, probably) and picked up bits of swarf, a rub down and re-spray will fix that. The chucking stub was used again to mount the part in the dividing head to machine the three side faces and drill the holes for the valve cages and the inlet and exhaust passages. The fourth side is just a small flat to take the camshaft bearing:



The bottoms of the ports to take the valve cages have to be bored flat and for this I backed up the grip from the collet with an angle plate:



Setting up this way makes drilling the inlet and exhaust tracts to the correct depth easy:



The last surfaces in the combustion chamber were formed with a 5/16" round nose slot drill:



The chucking stub was cut off and the head clamped down to machine and drill the rocker arm mountings and drill and tap for the spark plug:



I had to juggle a compromise between the correct coordinates for the rocker arm pivots and the centres of the bosses on the casting, there may be some adjustments needed to the arms when these are made. The head now just needs a few studs making and a coat of paint (matt black stove paint I think) and it will be ready to assemble.

David

Edit 2019-03-28: Added .jpg and link to .pdf of next drawing - DT
« Last Edit: March 28, 2019, 02:40:44 AM by deltatango »

Offline scc

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Re: Another Westbury Wyvern build
« Reply #52 on: March 17, 2019, 09:33:33 AM »
Very nicely done :ThumbsUp:                            Terry

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #53 on: March 17, 2019, 11:29:35 AM »
Thanks Terry!

Looking at the last picture in the previous post I can see that I forgot to say that I've changed the design to use a bronze insert for the exhaust valve and not to seat the valve in the head as drawn by ETW. For this I tapped the head M12 x 1.0 and cut a 5/8" hex on the body of the insert. The inlet valve housing could easily have been made the same but I'd already bought the casting so I machined that. Pictures next time.

David

Offline Roger B

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Re: Another Westbury Wyvern build
« Reply #54 on: March 17, 2019, 05:25:21 PM »
That cylinder head looks quite a tricky thing to hold and machine  ::) You seem to have got it sorted  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline Muddy Rutter

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Re: Another Westbury Wyvern build
« Reply #55 on: March 18, 2019, 01:54:42 PM »
It's good to see your progress David.

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #56 on: March 26, 2019, 11:02:28 AM »
Having a nearly finished cylinder head it's time to make some of the bits to attached to it, this time the valves and housings. Like other people I've modified the design to have both valves in inserted seatings rather than have the exhaust seating directly in the alli of the head (probably left over from having the head cast in iron). These could both be the same from bronze bar stock but as I'd already paid for the inlet side casting I might as well machine this as a start. There was a lot of extra metal on the raw casting so no worries regarding finding the finished part inside it. Mounted in the 4-jaw I turned the valve seat end to fit the hole in the head:



which could then be held in a collet to rough down the other end:



and drill and bore this to take the valve spring:



The flange was filed to shape using a steel guide made from the drawing. The exhaust housing was very much the same apart from the M12x1.0 thread and a 5/8" hex milled on to give a spanner something to get hold of:



After the 45 degree seatings were machined (see later), the final operation on both parts was to put a 2 degree taper on the outer end to improve the appearance:



The two valves were turned back-to-back from stainless steel (grade unknown but it may not have been free-cutting!). SS is a poor conductor of heat and flood coolant was necessary for running down the stem to 1/8", first with a Crobalt bit in the Diamond Tool Holder, then finishing with a sharp carbide bit:




Getting the lathe set up to turn the valve seating faces was tricky as its necessary to machine the valve faces and the bronze seatings at the same setting. The top-slide was set over to 45 degrees and the lathe run in reverse to machine the valves:



I was concentrating hard to avoid mistakes on the bronze bits and forgot to take a picture - sorry! Before separating the two valves looked like:



The springs were supplied in the kit of bits from Hemingway, I made two spring collars and 5BA nuts from MS and at this stage the finished set of bits looked like:



The final nerve-racking op was to fit the bronze seatings into the head and drill through for the inlet and exhaust tracts. All went well and the bits all fit together:



and into the head:



Currently the family looks like:



David

Offline MJM460

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Re: Another Westbury Wyvern build
« Reply #57 on: March 26, 2019, 11:13:20 AM »
Great progress David.  The family is really coming together.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Muddy Rutter

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Re: Another Westbury Wyvern build
« Reply #58 on: March 26, 2019, 11:55:46 AM »
Looking good David and really useful to follow.

Nick

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #59 on: March 28, 2019, 02:54:18 AM »
Hi everyone,
I've created a new version of the Wyvern CAD model and drawings. These incorporate the errors, omissions and modifications that have been needed as the build has gone on. The exhaust valve bronze housing now has a 5/8" hex for tightening rather than tommy bar holes and the timing gears are close to correct sizes. The flywheels hubs have been modified (again) to clear the crankshaft timing gear. A bunch of useful or omitted dimensions have been added.

I've edited the previous posts where there were pictures or links and added missing drawings to two other posts. Hope all these work OK.

When the timing gears, camshaft and valve gear and the con-rod are done then it will be on to the last sheet of drawings (ignition and carby).

At the end of next week we are going to Japan for two weeks so progress will stop until the end of April.

David