Bristol Mercury revisited

[Vixen]

I am pleased Per took all that leg pulling with a good heart.

I have been making the final bits for the Bristol Mercury crankshaft assembly. Small items like woodruff keys and other fidelity small details.

Here are all the components for the crankshaft layed out for a family photo.



From left to right are the reduction gearbox spline drive and lock ring, The thrust bearing and lock ring, the gear wheel which drives the c,m ring reduction gears, the cam ring with it's internal gear and bronze bearings, the supercharger drive gear and lock ring, the accessory gearbox drive tailshaft, and finally the accessory skew gear and starter dog. The crankshaft is in two parts held tightly together by the large pinch bolt. You can also see the two 4mm ground rods used to align both halves of the crankshaft after the master conrod ihas been fitted.








The last tree images show the crankshaft components loosely assembled. That slender tailshaft performs several functions, it drives the accessory gearbox, it connects the starter to the crankshaft and it also conducts the flow of lube oil supply from the pressure oil pump which is located at the rear of the engine, to all the crankshaft bearings. You can see some of the oilway drillings at the rear of the tailshaft

They say the devil is in the detail, but sometimes I begin to think it's the amount of detail, which is the Devil.

Stay tuned

Mike

[Johnmcc69]

WOW!
That's a beautiful little assembly! Great job on the machining of it!

 That gives "fiddily" bits an entirely different meaning...

 

 John

[Vixen]

Thanks for calling in John. Here are some more 'fiddly' bits for you.

The connecting rod arrangement for most radial and rotary engines are all similar in concept. It consists of a Master rod to which eight Slave rods are attached. Here you can see some of the conrods for the Bristol Mercury engine. To make the hub of the Master rod as compact as possible ( to minimise geometric errors), bronze bushed bearings are used. Note, the big end of the Slave rod is actually smaller in diameter to the piston wrist pin. That shows how important it is to achieve a compact design.




This is the Master rod, you can see the eight lugs for the Slave rod bearing pins. The two lugs, either side of the main rod, are deeply recessed. This presented a problem during manufacture. I devised an offset grinding fixture for my Dremmel. The grinding head rotates about the Slave rod pin's axis centre, this allows the undercut to be ground away as the grinder swings from side to side.






Here you can see the Master rod big end bearing. The cylindrical part of the bearing is generously perforated to allow free flow of the lubricating oil, it bearing is free to float and rotate about the crankshaft pin and also inside the Master rod. Theoretically it could rotate at about half the engine speed. The end faces of the big end bearing have channels to direct  lubricating oil out to the eight Slave rod bearing pins.




Here is the Master/Slave rod assembly installed onto the crankshaft. That huge pinch bolt clamps the two halves of the crankshaft together. There are no keways to maintain alignment, it is totally reliant on the clamping force alone.






Here the crankshaft and con rods are being trial fitted to the two piece crankcase. A single cylinder and piston have been added so that the fore and aft position of the rotating parts can be checked and adjusted to ensure the outer ends of the rods are central within each piston. As you can see, it's all very tight within the crankcase. Not a lot of room for adjustments







The next items for installation are the cam ring and the eighteen roller cam followers which fit all into the front section of the crankcase.

So stay tuned

Mike

[crueby]

Oh. My.   That is both fascinating and stunning.

[fumopuc]

Hi Mike, following along speechless.

[scc]

Exquisite         Terry

[steamer]

Beautiful work Mike!!!!!

[Craig DeShong]

Love’in it Mike 

[michelko]

You are for sure an real Artist 

Regards Michael

[cnr6400]

Mike, 

[Vixen]

Thank you everyone for dropping in and leaving such nice comments. They are very much appreciated and rewarding. Seems to make the effort worthwhile.

The weather was fine and dry today, which gave me the opportunity to spray paint the outside of the crankcase. My preparation starts with washing the parts with clean cellulose thinners. The thinners quickly removes any cutting fluid residues and greasy fingerprints. I am always amazed at how dirty the liquid becomes while cleaning what appears to be perfectly clean metal. The down side is the smell which lingers in the air for days.

I always preheat the parts to be painted and also the rattle cans, by placing them on a warm radiator for half an hour. This ensures the paint will dry quickly and the propellant is at optimum pressure to produce a fine and even fan (aerosol) of paint. I apply a thin base coat of light grey acid etch primer, which makes the top coat stick like glue to the aluminium. The primer coat is allowed to dry thoroughly before I add two or three thin layers of satin black acrylic car paint. I find the rattle can paint from Halfords (a UK motor parts supplier) to be adequate. The spayed parts are allowed to dry and left to harden overnight. Needless to say there is a lot of masking off required to shield those parts which are to be left as bare metal.






All of the Bristol engines were painted with black enamel to prevent corrosion and supposedly to help with heat radiation.

The crankshaft and conrod assembly was reinstalled in the crankcase before I set about assembling the cam ring and the eighteen roller cam followers. The front cam ring has four lobes and drives the inlet valves, the rear ring drives the exhaust valves. The cam ring turns at 1/8 crankshaft speed driven by a simple spur gear reduction set. Each roller cam follower has a phosphor bronze wheel running on a hardened steel pin within a forked steel pushrod which slides in a bronze bearing. It was a seemingly endless task to make all these parts for my two Bristol Mercury engines.






Here you can see the results of today's work. The crankshaft and camshaft are now finally installed within the crankcase and everything rotates nice and smoothly. Along the way I discovered a broken M1.5 tap in one of the 36 cam follower bolt holes, I must have broken the tap years ago but had completely forgotten about it. I don't think there is much I can do to extract it other than to use a miniature spark eroder but that would mean stripping everything down and giving the EDM job to a local engineering firm. Bummer !!!




I will make a daylight photo to replace the last one, provided the weather is still dry tomorrow morning.

Stay tuned

Mike

[Admiral_dk]

Oh man what a bummer ... and thank God that this will not have any influence on running this beauty 

Besides this, I'm completely out off superlatives for this build Mike ....

Per

[Rick Doane]

Mr. Mike:

You Sir are an Artist!

Best Regards...….Rick

[zeeprogrammer]

...I'm completely out off superlatives for this build Mike ....

Yeah and you're not the only one. Time to repeat...awesome!

[Art K]

Mike,
the crankcase and rod assembly look great, what more can I say. To bad about the broken tap though.
Art