Westbury Seal by Vixen

[Vixen]

Thank you Craig and Mark for calling in and for your kind comments. 

Mark, I machined the valve pocket using a 6mm diameter cutter. That gives a corner radius is less than 2/16" which should help, I will have to see what happens later. Perhaps I can devise a special adjusting spanner to fit that tight corner.

Mike

[Vixen]

After the crankcase, I made the front bearing and cam gear drive casing. I decided to manufacture these casing from solid. For me. it was an easier task to machine from the solid rather than trying to find an engine part inside an oversize lumpy casting.

First up was to machine the spigot and bore the bearing carrier to fit the roller bearing and bring the plate to the required thickness. The mounting holes were drilled and tapped or drilled clearance size where appropriate. The bearing carrier was put to one side as the outside profile will to be machined together with the matching cam gear case.




The cam gear case started life as a block of 6082 t6. I started by machining the internal pockets and drilling the mounting holes to correspond with those on the bearing plate and also the front face of the crankcase. I also partly machined the outside flange profile. This was not strictly necessary as it was repeated later. I did serve to allow all the excess material to be hacksawed away; no point in unnecessary machining.




Next I bolted the cam gear cover and the bearing carrier to a sacrificial  jig plate made from some scrap perspex sheet (it's cheaper than alloy and there's plenty in my scrap box). The bolt holes were recessed to the required depth before the assembly. Then the first stage, the outside profile, was machined on both items




The central bosses were machined to shape and the recesses bored.






They were then machined to the correct height before  some final profiling of the bottom edge. The two units were then given some hand finishing before being offered up to the crankcase.




It will look much neater when the correct length of cap head screws are delivered, to replace these temporary ones.






Stay safe

Mike

[gadabout]

Mike, very nice indeed!
Seem to remember there was an error on the drawings with this part or I misread them! Kind of think one of the holes was incorrectly shown as a clearance hole and it should have been a tapped hole or vice versa

cheers
Mark

[Vixen]

Made a little progress with the Westbury Seal.

The rear bearing housing was straightforward lathe turning from aluminium stock rather than a casting.  It somehow escaped the attention of the camera. I decided to fit shaft seals at both ends of the crankshaft and modified both housings to suit. I selected some NBR rubber seals made by Barnwell in the UK. The rear shaft seal will be part no 056 037 13 NBR 01.

The oil sump, or oil pan, was next up. I also made this from a billet of aluminium rather than a casting. This allowed me to make the sump slightly deeper, to contain a larger quantity of oil and also to incorporate some small cooling fins on the sides.






The cylinder head casting presented a problem. Unlike the crankcase casting, which was generously oversize, the cylinder head casting had absolutely no machining allowance on the side and ends. The top and bottom surfaces were OK. The first casting I received was actually undersize, due to some overenthusiastic sawing and grinding by the foundry when they removed the infeed runner. Kirk at Hemingways quickly replaced it with a better casting. Even so, the new casting had no machining allowance and will need some careful hand filing to finish the side and end faces to match the machined crankcase. There was adequate machining allowance on the top and cylinder faces to machine them flat. I have still to drill the holes for the cylinder head studs.





Here is the engine loosely assembled and enjoying the spring sunshine. Isn't the sky blue, these days, with the reduced CO2 pollution levels?



Stay tuned in and keep safe

Mike

[fumopuc]

Hi Mike, nice progress.

[Vixen]

Thank you  Achim.

Still making good progress with the baby Westbury Seal.

The next item to be manufactured is the crankshaft, which started life as a 30mm diameter EN8 steel bar. The rear bearing journal, flywheel taper and the screw thread for the retaining nut were all machined without disturbing the chuck, to ensure concentricity.



There will be more to follow shortly.

Stay safe

Mike





It is notoriously difficult to achieve accurate positioning of the two parts when using tapers. The part machined flywheel was fitted to the shaft to check the fit of the crankshaft and flywheel tapers and the retaining nut. The position of the flywheel's forward face was accurately measured and the location of the seating of the rear ball race bearing adjusted accordingly. The outside diameter and rear face of the flywheel were then turned true while mounted on the embryo crankshaft.




There isn't a keyway to drive the flywheel, it relies entirely on the fit of the taper; just like the tailstock taper on your lathe. As you cans see, after finish turning the flywheel, I needed to use a bearing puller to release it from the taper on the crankshaft.




The forward bearing journal and shaft were turned to finished size as was the outside diameter. 




The embryo crankshaft was transferred to the mill for machining of the flat faces on either side. I decided to try a different machining strategy to pocket the flat sides. I recently obtained some new CAM software from Estlcam. Among other features, the new software allowed the use of 'Peel' pocketing. I am sure there are alternative names for this 'Peel' machining, but basically it allows large depths of cut with very small stepover widths (typical 10%) coupled with higher feed rates. The most important feature being the toolpath never exceeds the set width of cut, unlike more normal pocketing methods, that can see the width of cut suddenly rise as the cutter gets itself into a corner. Also the 'Peel' strategy used a helical path while plunging to depth, which allows the use of non centre cutting end mills.




The 'Peel' toolpaths are quite different to anything I am used to seeing. A series of ever increasing concentric circles followed by an outside finishing pass. The higher depth of cut and narrow stepover seems to work well. The cutter removes a consistent amount of material, without the transient overloads normally associated with machining into corners. The cutter sounds unstressed and lightly loaded. I will experiment further to optimise the settings, I am sure I could drive the machine a lot harder, removing material at a much higher rate than before.




Here you can see the first finished flat surface on the side of the crankshaft and the three raised lands for the counterweights. These are not a normal feature on the Westbury Seal crankshaft, I figured a little conrod counter balancing could only be a good thing for a two bearing crankshaft.




Here I have used an 8mm ball cutter to refine the root of the counterweights.




And here is the part finished crankshaft enjoying some early morning sunshine.



There will be more to follow tomorrow, so stay tuned.

And stay safe

Mike

[Jo]

 

This reminds me I must finish the Seal Major crankshaft 

Jo

[Jasonb]

I like those sort of clearing paths both for internal pockets and also roughing out externally and they do seem to shift the metal. Plus you get to use plenty of the side of the cutter not just the first mm or two.

[michelko]

Veeery nice crank:cheers:
Michael

[steamer]

I like the integral counterweights...I built my Wallaby to the print...but your way is much better!

Dave

[Art K]

Mike,
I like the stuff you've done to this engine. Are you intending to add some sort of oil filter? Or will the deep sump be enough, with the added oil. I think the counter weights added to the crank are a great idea, as are seals. The great thing about any engine is you can build it any way you want, there is no wrong way.
Art

[gadabout]

Mike,
Your work is outstanding once again!
How do you like ESTLcam? Is it easy to learn and use? I need to get my head around using my cnc better, currently using featurecam 5 but I have to do quite a bit of editing the nc it spits out to get it to run on my machine using mach3.
Regards
Mark

[Roger B]

Nicely done   

How did you ensure that the two ends are concentric?

Have you seen any distortion due to unbalanced stess in the metal (it looks like cold drawn)?

[Vixen]

Thanks to all of you for calling in.

Jo, I  looked for inspiration in your Seal posts but find you have not got further than roughing out the Seal Major crankshaft. Are you giving it plenty of time to stress relieve?

Art, I have rediscovered the design freedom of a freelance engine, you can make whatever changes you wish. A true scale replica engine (Bristol Mercury or Jupiter) gives no such freedom, you are in a straight jacket.

Mark, Jason, The ESTLcam software is good in places and easy to learn. It offers several pocketing strategies, Linear (raster) Parallel, Peel and Trochoidal; each of which has is own advantages/ disadvantages. On the down side I can find no way of viewing or editing the G-code, It is saved direct to file from the toolpath preview screen. I have to use another CAM program (or LinuxCNC) to make and view edits. It's just another tool in the toolbox, sometimes you need to use all the tools available.

Roger, Distortion and concentricity will always be a problem with a long crankshaft. I propose to leave the part machined crank for as long as possible before machining the big end journals. Hopefully it will stress relieve itself with time. The throw pieces, for turning the big end journals, will be attached to the main bearing journals. Fortunately the Seal crankshaft is physically quite small which will help to minimise any errors.

Stay safe

Mike

[Jo]

Jo, I  looked for inspiration in your Seal posts but find you have not got further than roughing out the Seal Major crankshaft. Are you giving it plenty of time to stress relieve?

No I was suffering from Brain fade back then Its something to do with the drug the Doc gave me, which they mentioned after I had been taking it for a while  I am slowly building up to more complicated stuff again as the effects diminish.

Jo