2 stroke thread (with occasional F1 relevance!)

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Sun Nov 12, 2017 6:14 am

Hello all.

Quote from https://markwalkermotorcycles.com/ :

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Mark Walker:

“In the early 90’s I was travelling back from a Canberra Drag race and pulled into Bundanoon, I met a bloke in the bar, and he asked me what I had in the trailer, I said “My drag bike, a home built 2lt V-Twin” and he was very interested in my work and he happened to mention he was into Hot Rods and he said he had an unusual head at home, he said it had a cylinder in it, rotating and no valves, and I nearly dropped my coffee on the floor because at the time, I was building my own wooden models to build my own rotary valves,

so as you can imagine I was so keen to look at what this piece was,

so I followed him back to this old falling down weather board cottage, the house was chock with car parts and all around the yard and he directed me down to this old shed and he got up on an oil drum and lifted down this head wrapped in a blanket and he unfolded the blanket.

I wasn’t imagining much, but I went wobbly as it was a genuine Dunstan Rotary Valve, made in Melbourne by Dunstan himself, stamped no 29.

This changed my whole concept of cylinder heads, it was a cast aluminium head, water-cooled with a beautifully cast iron rotor cylinder down through the centre of it with slots both sides for the ports and floating bronze seals.

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Since that awakening I have learn’t alot about David Dunstan and his heads.

The type of head I am using on Big Ned is a Roland Cross design valve, he started his work in the early 20’s in England.

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2 Great Pioneers : Roland Cross and Aspen which you can research yourself.


I have spent my life working on, modifying and building Poppet Valve engines and then converted over to a new religion… “Rotary Valves”. When you realise the advantages of a Rotary Valve over a Poppet Valve are staggering…. They are an addiction.

End of quote.


Thanks
Manolis Pattakos

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Sun Nov 12, 2017 11:38 am

Hello wizz33


Qute from http://nautilusengineering.com/nautilus-cycle :

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A normal piston with "short" piston skirt (like that shown above) has a lot of tilting and "play".

Any idea on how the extension at the center of the piston crown aligns (as required toprovide sealing) with the hole in the cylinder head?


Here are shown the moving parts of the "cross-head" OPRE prototype engine:

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The above parts are inside the engine of the following youtube video:



The engine runs on Diesel fuel (compression ignition) at a 17:1 compression ratio, and stands free on the floor (vibration free).
Only the piston rings, the con-rod big end plain bearings and the fuel injection are from the market.


Even with the cross-head design of the above OPRE engine (which means extra long "piston skirt" and minimum piston play), the alignment of an extension on the piston crown with a hole in the cylinder head is difficult because the required clearance is too small otherwise the pressure difference between the two chambers - the main cylinder and the small cylinder in the head - cannot be significant.

Do I miss something?

Thanks
Manolis Pattakos

J.A.W.
52
Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: 2 stroke thread (with occasional F1 relevance!)

Post by J.A.W. » Sun Nov 12, 2017 3:09 pm

Yes Manolis.. the Nautilus & Walker* units appear to be 4T's & your's (quite rightly, thread topic-wise) is - a 2T!

*How has Walker improved upon the fundamentally flawed Aspen/Cross design - to make it viable?
Or are his 'back-yard' builds just 'novelty/folly' - types with no prospect of running long enough - for any practicable TBO?
Sturmbannfuehrer Dr von Braun sez..
"Oberste Prioritat hat es Londoner Terror zu vergelten. Und danach, der Mondflug!"

wizz33
0
Joined: Fri Aug 25, 2017 6:47 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by wizz33 » Sun Nov 12, 2017 7:24 pm

in the autoline interviews they mention that there is not much precision needed

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Mon Nov 13, 2017 8:11 am

Hello J.A.W.

Mark Walker is a different story.

Fortunately, he doesn’t care about the TBO and the number of strokes.

He made 4-stroke poppet valve racing engines:

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He made 2-stroke engines:

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He made 4-stroke rotary valve engines:

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In his Big Ned engine (Cross rotary valve):

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Mark Walkers applied the floating cylinder principle of Cross:

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according which the high pressure into the cylinder during compression – combustion – expansion pushes the cylinder – cylinder head onto the rotary valve.

With its 3lit capacity, the V-2 Big Ned is in another class of magnitude.


Does it matter the TBO or whether the engine is really functional?


Mark Walker had a dream and worked on it.

We should wish to have more guys like Mark Walker.

Thanks
Manolis Pattakos

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Mon Nov 13, 2017 11:56 am

Hello Wizz33

You write:
“in the autoline interviews they mention that there is not much precision needed”


Even if “there is not much precision needed” (let me doubt),
I can’t see the advantages,
while some drawbacks are obvious:

like the smaller valves (volumetric efficiency at high revs?),

like the compression-expansion of the mixture inside the cylinder before its ignition (the mixture in the cylinder is initially compressed at a, say, 12:1 compression ratio, then it expands at a, say, 8:1 compression ratio without making any work (actually, this process consumes mechanical work into friction), and only then the combusted mixture in the small chamber enter into the big chamber and ignites the rest mixture),

like the thermal loss when the combusted gas in the small chamber (which is from 1/6 to 1/3 of the total mixture) passes through the slim peripheral opening formed between the extension of the piston and the hole in the cylinder head (it reminds the pre-combustion chamber in the old Diesels), etc.


With a controllable VCR:

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(more at http://www.pattakon.com/pattakonVCR.htm )

the compression ratio can be as high as required for the auto ignition of the mixture and the HCCI combustion.


In the one case (Nautilus) we limit the high compression that causes the auto ignition in ~30% of the mixture, in the second case we compress all the mixture to the point of auto ignition.


What makes the divided chamber of Nautilus better and the BTE higher?

Thanks
Manolis Pattakos

J.A.W.
52
Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: 2 stroke thread (with occasional F1 relevance!)

Post by J.A.W. » Tue Nov 14, 2017 5:19 am

Hi Manolis, IMO, while Mark Walker does quite a creditable job of the 'tinkerer's art' - it stands no useful comparison..
..to Uniflow's proven practicable applications, or your own advanced 2T designs, conceptually..
Sturmbannfuehrer Dr von Braun sez..
"Oberste Prioritat hat es Londoner Terror zu vergelten. Und danach, der Mondflug!"

manolis
75
Joined: Tue Mar 18, 2014 9:00 am

Re: 2 stroke thread (with occasional F1 relevance!)

Post by manolis » Tue Nov 14, 2017 7:34 am

Hello J.A.W.

It seems that besides being a tinker, Mark Walker is a thinker as well.

A long existing problem / drawback of the “Cross floating cylinder design” is how to support the cylinder head on the crankcase and how to receive the thrust loads the piston skirt applies onto the floating cylinder.

With the cylinder head supported on some long stands, things get difficult.

Mark Walker thought a solution: to bridge the two cylinder heads of his Big Ned engine (a V-2 at 90 degrees with Cross rotary valves and floating cylinders) to form a stiff triangle structure.

With the added bridge (the gray pipes from the one cylinder head to the other):

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each cylinder head is not left alone to vibrate, and the stands can be thinner.



It takes more than a tinker to make from scratch, with limited resources, a competitive drag racing engine / motorcycle:

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Photo above:
Pistons and Rods under Development.

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Photo above:
First Crankshaft.
The first Crankshaft was made from Assab Steel. It was 4" Stroke. It had Press in Main Shafts to Flywheel and a Screw up Crankpin with 2 different numbers on threads on each end of the Pin and a 2" Big end Sleeve. The first Barrels were machined from a Caterpiller Liner

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Photo above:
Heads Assembled
Cylinder Heads, Conrod, Slipper Piston- machined from 5083 running on teflon buttons, Aluminium Bronze Seats, Stainless Steel Valves, Heads Machined out of 5083, Conrods - 1 in construction due to a backfire cracked the rod - machined from 7075 plate.

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And as he says:

“I have spent my life working on, modifying and building Poppet Valve engines and then converted over to a new religion… “Rotary Valves”.

When you realise the advantages of a Rotary Valve over a Poppet Valve are staggering…. They are an addiction.

Thanks
Manolis Pattakos