ETW's Wyvern Gas Engine

[tangler]

Hi Folks,

I've taken the plunge and ordered the castings and drawings for Edgar Westbury's  Wyvern gas engine from Hemingway today.  I'm hoping that telling you guys about it will discipline me to take this to completion in a (reasonably) short time.  Has anybody any experiences with the engine?  I'm tending towards gas (rather than petrol) as fuel.

I'll keep you posted.

Rod

[ths]

No experience with it, but I'm looking forward to seeing you build it.

Hugh.

[steamer]

Looking forward to it Rod!

Dave

[Bogstandard]

Again Rod, no specific experience, but if you are going with gas, I do have the drawings for regulators and demand valves, for when you get that far.


John

[Jo]

I have a set of his Centaur castings maturing in my collection 

Jo

[tangler]

John,

Thanks for the offer, I'll take you up on that when the time comes.

Cheers,

Rod

[michaelr]

Just finished building my Wyvern, it's a fairly straight forward build but I had some issues, the main bearing oilers have to be reduced in diameter to clear the crank webs, you may have to modify the side shaft bearing at the skew gear end to get clearance for the gear, and the fixing positions.

I made the exhaust valve seating the same as the intake valve, using valve pockets (picture attached) this makes it easier to remove the valve for regrinding, I also seated the valve pockets using O rings.

Mike.

[tangler]

Here are the castings.  Good quality sand castings, they look like they've been pickled after fettling.  Nice prompt service from Hemingway.  I ordered the castings only set as I want to make the gears myself so I now need to study the drawings to find out what other materials I need and think about how I will make the crankshaft.

Mike, thanks for the heads up, I'll bear your comments in mind.  ETW's oilers aren't particularly elegant, I might do something else.

[steamer]

Those castings look nice!

Dave

[vcutajar]

Rod

Looks like an interesting build.  I will be following you along.

Vince

[tangler]

OK, here we go - any comments, criticisms, advice and "whoa there, don't do it like that"will be very welcome!

Mr Westbury didn't think you needed to do much to the aluminium sub-base but then he didn't expect the maker to have a milling machine.  The top of the sub-base has a moulding number  cast in so this does have to be removed.  I sanded of the worst of the casting bumps on a piece of sand paper on the surface table so the base didn't rock.



Pretty straightforward the to mill the top surface with a 1/2" endmill





I the turned the sub-base over to mill the base but couldn't juggle the position/clamps on the table to be able to cover the whole base with the end mill so resorted to my only shell mill.

[steamer]

Great start Tangler!

Dave

[tel]

Off to a fine start - keep 'er going!

[tangler]

The main bed plate needs to have a good flat bottom to sit on the sub-base.  Very awkward to hold on the milling table so I reckoned it would be quicker to file it flat to the surface plate rather than make a fixture.  No pics I'm afraid - I seemed to get very blue! 

The bearing cap seats are machined at 30 degrees.

The head rotates on my mill and there is a taper pin that re-locates the head back to exactly 90 degrees so no worries there



In this configuration the milling cutter needs to cover the whole width of the cut so I continued with the shell mill



The centre of the bearing was popped, the seat needs to be milled down to this mark





Bearing caps next...

[Bogstandard]

Tangler,

If I could make a suggestion, hopefully before you go any further.

DO NOT trust that the castings are correct. Get them on your surface plate and using either a height gauge or scribing block, check that the castings are the correct height from one side to another, square where square should be, parallel in the right parts, say to the main base etc.

You must get an accurate datum on each main part before going any further.

If that isn't carried out, you run the risk of something becoming twisted or not fitting later.

Once you have your datum, and got it machined, then everything else goes from that.

This is a very common mistake when beginners start out with castings, they think that they should fit together correctly, but in fact, they very rarely do, and making from castings can be a lot more difficult than making from barstock.

There must be thousands of sets of part made castings sitting under benches where someone has started before getting their datums set up first, then soon found out that things don't fit.

I am not trying to scare you or put you off, but do please be careful and don't have a cavalier attitude towards casting sets.

I have used Hemingway castings before, and they are not all they are made out to be, they require a fair amount of work and fiddling to get a well running and looking motor.

If you really want to see how a datum is set up, have a look at a bit of my post, here

http://www.modelenginemaker.com/index.php/topic,158.0.html

John