Author Topic: By Jupiter  (Read 75301 times)

Offline Tennessee Whiskey

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Re: By Jupiter
« Reply #90 on: March 14, 2018, 09:05:19 PM »
Yeah and they also know there isn’t a chance of the lady bringing it back in for a buyback if things go wrong  :old: 8). Seriously, your work is phenomenal.  :cheers: :cheers:

Cletus

Online Vixen

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Re: By Jupiter
« Reply #91 on: March 14, 2018, 11:21:56 PM »
Hay Cletus,

I have built a number of super detailed engines over the years, but this Jupiter is the biggest (over 1/3 scale) and by far the most challenging yet. It is taking me into some of those dark, unknown corners of engineering where more sensible model engine builders rarely go. I will admit, I will be pleased when this lost wax casting phase is finished and I can get back to more traditional model engine machining and building.

The last few months have been technically interesting, researching, experimenting with a different casting technique. Although I can truthfully say that I have hand crafted all the patterns; that I have cast the silicone rubber moulds and cast (injected) all of the waxes. It is a disappointment that I have been forced, through lack of equipment, know how, skill etc to subcontract the actual metal pouring to someone else. Lucky for me that I was pointed in the direction of Just Castings Ltd by Jason and Neil Wyatt. JCL made the last part trouble free, quick and reliable.

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Online Vixen

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Re: By Jupiter
« Reply #92 on: April 06, 2018, 08:00:14 PM »
In Vixens Den springtime has arrived and the time has come to fit the Inlet Manifolds and the two Exhaust Stubs to the Bristol Jupiter Cylinder Heads.

My first task was to correct the rear face of the Cylinder Heads. I found they all needed to have 4.5mm cut off the rear face to match the Bristol's drawings. I managed to do this without using the camera to show an extra long 4mm diameter end mill cutting across the fins in a horizontal direction. You need to be very careful when re-machining cut fins, it is all too easy to catch an edge which usually results in a bent fin or two and lots of profanity.

The first photo shows a stripped down Cylinder Head being set up prior to drilling and tapping of the four 8BA screws which secure the Inlet Manifold to the rear of the Cylinder, the rear face has already been machined to size.  To my horror I found that two of the vertical fin slots coincide with two of the four securing bolt positions. To provide material for these two bolts, it was necessary to drill (mill) a 3mm dia hole between the offending fins and insert a 3mm dia aluminium dowel, secured with loctite. These two dowels can be seen on a latter photo




The drill insisted in trying to wander off course in the fin slot, so I made a steel drilling jig plate to help steer the 1.8 mm tapping drill down between the fins and into the new dowel. I also made second jig plate with 2.2 mm holes to steer the 8BA tap.




It all worked out well and the Inlet Manifold bolted to the Cylinder Head perfectly.




Fortunately the Exhaust Stub bolt holes did not present any problems. Each Exhaust Stub is secured with four 8BA threads.




The final sequence of photos show the competition completion of today's session







All I have to do now is to repeat this fiddly little job eight more times.

I will also order sufficient reduced head size 8BA bolts for the complete set of nine cylinders.

I will also lap in all 36 Inlet and Exhaust valves while the Cylinder Heads are being worked on. Another small step towards completion.

Mike

« Last Edit: April 06, 2018, 09:36:51 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline zeeprogrammer

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Re: By Jupiter
« Reply #93 on: April 06, 2018, 09:21:00 PM »
Wow. And 8 more to do! It is indeed very much a jewel.
 :popcorn:

The final sequence of photos show the competition of today's session

I don't know if you meant to say it that way...but I like it.  :Lol:
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Online Vixen

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Re: By Jupiter
« Reply #94 on: April 06, 2018, 09:33:24 PM »
Hi Zee

Well spotted, sometimes I think I have a smell chucker instead of a spell checker the way it mixes up the worms.

Congratulations on reaching the Age of Retirement. By the way, all those chores you put off until retirement can wait a little longer. Celebrate your retirement by indulging yourself a little, take that promised vacation, make chips in the shop or whatever. DO IT FOR YOURSELF for a change.

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Dave Otto

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Re: By Jupiter
« Reply #95 on: April 07, 2018, 01:18:13 AM »
Nice update Mike, it appears that the new parts are fitting up nicely.


Dave

Offline b.lindsey

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Re: By Jupiter
« Reply #96 on: April 07, 2018, 02:03:17 PM »
I can't add much to what has already been said Mike but am still checking in regularly and learning a lot from your posts. All this meticulous work will certainly pay off in the end with a jewel of an engine.

Bill

Offline steamer

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Re: By Jupiter
« Reply #97 on: April 07, 2018, 03:57:56 PM »
That looks great!
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Online Vixen

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Re: By Jupiter
« Reply #98 on: April 07, 2018, 04:28:18 PM »
Hi Dave

How are things with you.? Are you healing well? It is always slower process when we get a little older.

Why not spend a bit of time behind the desk drawing up that Porsche 917 engine you started on a while ago?

Mike
« Last Edit: April 12, 2018, 11:10:46 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline steamer

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Re: By Jupiter
« Reply #99 on: April 07, 2018, 05:48:15 PM »
Hi Dave

How are things with you.? Are you healing well? It is always slower process when we get a little older.

Why not spend a bit of time behind the desk drawing up that Porsche 917 engine you started on a while ago?

Mike
Not a bad idea!

I'm walking short distances starting to strengthen the quad.   The surgical connection is good, just need the rehab.
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Tennessee Whiskey

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Re: By Jupiter
« Reply #100 on: April 07, 2018, 07:57:13 PM »
Dave, mental, spiritual, or physical  :lolb: :lolb:. Sorry for the hijack

Cletus

Offline Craig DeShong

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Re: By Jupiter
« Reply #101 on: April 07, 2018, 11:20:34 PM »
Mike.  I've open this thread, followed along, and closed it saying nothing.  Thus work is so extraordinary, I find a comment difficult, but thanks for showing me this amazing level of workmanship.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline steamer

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Re: By Jupiter
« Reply #102 on: April 08, 2018, 12:10:25 AM »
Dave, mental, spiritual, or physical  :lolb: :lolb:. Sorry for the hijack



Cletus

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

Offline Art K

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Re: By Jupiter
« Reply #103 on: April 08, 2018, 12:50:44 AM »
Mike,
I've been busy in the shop myself getting Val ready for the NAMES show. Quite an elegant solution to the missing hole location. The interrupted hole is where I'd have been looking for an appropriate sized endmill.
Art

PS spell check only corrects wrong spelling not words. :lolb:
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Online Vixen

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Re: By Jupiter
« Reply #104 on: May 02, 2018, 02:31:13 PM »
You can only put off some jobs on an engine for a while but eventually you to make a start. The case in point being the 36 valves on the Jupiter' s cylinder heads.

Each valve has a steel valve seat screwed into the aluminium head with a fine 40 TPI thread and a separate screw in phosphor bronze valve guide. Each valve is closed by a set of triple valve springs, just like the full size engine. The steel spring seat cups are grooved to keep the three valve springs concentric.








I used Loctite 572 Pipe Sealant to secure and seal the phosphor bronze valve guides into the cylinder heads. While the sealant was curing, I made up two sets of piloted valve seat cutters from hardened silver steel (drill rod). Two at 45 degrees for the working face and two 60 degree cutters with which to thin the sealing face from 1.5 mm to approx 0.7 mm.






Any valve seat cutter, no matter how well made, will always leave minute radial ridges and grooves on the surface, you may need to use a X5 eyeglass to see them, but they are there. It takes a lot of extra time to lap away these marks. I followed Terry Mayhughs method of using two cutters one after the other to produce a finer surface to the valve seat. The idea being the second cutter should flatten any ridges left by the first. Only the lightest of pressure is used with the second cutter.




The easiest way I found was to grip the valve stems with a small drill chuck. There is a short piece of soft aluminium tube between the chuck jaws and the valve stem to prevent the valves being marked.





In order to test the quality of the valve seat lapping it purchased this little hand pump vacuum tester. It can get to about  400 mm Hg (-15 inch Hg) that's about  -8 psi without too much problem from internal leaks. I cap off the top of the valve guide with a short length of silicon tube, and insert a rubber cork into the inlet/ exhaust port. I can create the vacuum by squeezing the trigger a couple of times. The internal volume of the volume under test is approx 3.9 cc. I can make the volume bigger (20cc) by connecting a longer pipe, but the short pipe is the most sensitive. I have set an arbitrary leak rate pass criteria of 20 to 30 seconds for the -8 psi to leak to zero. Consider the engine running at 2000 rpm, the combustion chamber pressure should be at over 200 psi during the compression stroke and much higher still during the firing cycle. At 2000 RPM that's a duration of somewhere between 20 to 30 milliseconds. So my leak test criteria (8 psi over 20 to 30 seconds) has an enormous margin over the running environment.




I experimented with several types and grades of lapping compound. I tried various grades of metal polish (as suggested by Terry Mayhugh) as well as different grades of silicon carbide made up as a lapping slurry  It quickly became obvious that it would become a trade off between time and quality of the gas seal.

Solvol Autosol uses pumice as the abrasive, Given time (hours) it will lap the valve and seats to perfect finish which can achieve my 20 to 30 second test criteria. This shows that polished valve seats will provide the best sealing possible, but it takes forever. However, some valve seats for whatever reason, just would not ever achieve a perfect seal, no matter how long I lapped with the metal polish, On these problem valves I tried ultra fine 600 grit silicon carbide. The seats lapped in quickly, but this lapping compound leaves a dull surface rather than a polished surface, sufficiently that a vacuum leak rate of over 10 seconds cannot be achieved, seems you need polished surfaces for a perfect seal. That was rather unexpected, as I have always used grinding paste on full size engines in the past to get an even all round matt finish, which always appeared to be adequate, I never had a vacuum tester. Our model engines have much small capacity so will be susceptible to any leaks. Especially an engine with four valves per cylinder.

I have just obtained some 1200 grip abrasive powder and will experiment further (there are plenty of valves in the Jupiter)  to find a workable compromise between the time require for a highly polished valves seal using metal polish against the quicker, but less perfect seal that come with abrasive lapping media.




Some suggest that fine diamond lapping compounds are the answer, but I worry about the diamond becoming embedded in the valves or seat faces and the long term effects on the seats and the rest of the engine.

Mike


« Last Edit: May 02, 2018, 09:46:15 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

 

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