The Bucket Foundry

[Flettner]

Nice to machine, CC601 heat treated to T6.

[Flettner]

Put a gearbox in it shortly.
Flywheel will run on the right side via a wee gear drive. Drive will step up the flywheel speed say 1.5 to one. Little bit better charging than just bolted to the crankshaft. Pull start will operate off this flywheel.

[WilDun]

Put a gearbox in it shortly.
Flywheel will run on the right side via a wee gear drive. Drive will step up the flywheel speed say 1.5 to one. Little bit better charging than just bolted to the crankshaft. Pull start will opperate off this flywheel.

Looking good so far - relatively new territory I guess! - even if you had shelved something similar ( but successful), way back!

[lohring]

I'm not sure if this is the place to post this, but it's not a clean engine and the cylinder will eventually be investment cast. So far it's a thought project opposed piston design with two crankshafts. It will be piston ported, crankcase scavenged, through standard Walbro carbs. It uses as many standard parts as possible with output planned for each crankshaft driving two propellers. The gear train should be lightly loaded. I need to get at least 20 hp at around 16 to 18,000 rpm to compete with inline twins. More rpm should be easily possible since we've turned 26 cc engines to 25,000 rpm.

The main issue is how to get mixture from both crankcases into the cylinder. Below is my first thought. However, I think the different length transfers will upset the scavenging. Having all the transfers at one end with a passage connecting the crankcases is another option. Can you get mixture between the crankcases with this arrangement? How effective will be exhaust piston cooling and lubrication if mostly air goes into the exhaust end crankcase?

Lohring Miller

[Flettner]

Lohring, I have a design kind of along those lines for an autogyro engine, accept twin cylinder.
The gear train will have the two middle idler gears both become output gears. They are angled away from each other at 24, 12 from center, degrees and phased at 90 degrees each other.
Deep intermeshing, counter rotating. Look at the Anton Flettner intermeshing helicopter.

[Vannik]

Lohring, some thoughts:

1. One problem with OP engines is scavenging - swirl causes an unscavenged central column that can even move down towards the scavenging piston,
2. Using opposed transfer ports to clash the flows and causing an upward moving central column leaves and unscavenged outer region,
3. So how about using the one crankcase to feed transfers that causes swirl and the second crankcase to feed transfers that open slightly later to form the central column?

This swirl vs central column is also a problem for standard uniflow engines and is one of the regions where the ship engine builders are putting a lot of research into.

Why not use a toothed belt to connect the two cranks and have one end with a vernier pulley to adjust phase angle?

[Flettner]

This is the scavenge system used in my boat OP uniflow.
Two transfers opposite each other, upward swirl, 33% fuel.
Four more aiming at each other to create a central plume, 66% fuel, slightly later timing.
The ultimate aim was to head for 0% and 100% fuel respectivly. Creating an air buffer also. This combined with the different size pistons, inlet and exhaust.
9500 rpm. 25 years ago.
https://youtu.be/uiXsPkP9jvw

[WilDun]

Lohring, some thoughts:

1. One problem with OP engines is scavenging - swirl causes an unscavenged central column that can even move down towards the scavenging piston,
2. Using opposed transfer ports to clash the flows and causing an upward moving central column leaves and unscavenged outer region,
3. So how about using the one crankcase to feed transfers that causes swirl and the second crankcase to feed transfers that open slightly later to form the central column?

This swirl vs central column is also a problem for standard uniflow engines and is one of the regions where the ship engine builders are putting a lot of research into.

Why not use a toothed belt to connect the two cranks and have one end with a vernier pulley to adjust phase angle?

First thing I need to ask - is 'swirl' necessary in the first place? and if so, why is it necessary?
Surely this in combination with the curved entry of the transfer ports in a 'conventional' two stroke is the best way known to mankind of separating the components of the petrol/oil/air mix?? ........ isn't that the last thing we need?

I should stress that I am talking about the conventional two stroke here using the (also now conventional ) Schnuerle charging.

Someone here said that this actually was 'tumble' charging but I see it as 'axial swirl' (as opposed to the radial variety, which it is normally assumed to be!) - this must cause the now separated high speed charge to mix with the outgoing gases going into the chamber?

The OP arrangement ( which I have to admit can in certain cases be quite an awkward beast) does however give us a much better opportunity to keep the charges separate and use 'tumble charge' to create an integrated plug of fresh charge which moves down the cylinder, does not disintegrate and mix, but helps to push the charge out through a ring of radial exhaust ports.
This will also ensure that the cylinders/pistons stay a reasonably round shape, due to even heating (giving us the chance to use tighter clearances).

Along with several other 'outlandish' innovations, I believe that I have actually worked out a system on how that could possibly be done.
However, I am really past the stage now where I have the ability to carry out these experiments, so I have passed it on to someone else for evaluation - but no comment! ..... so realistically, I assume and accept it's not a viable solution! - it will no doubt remain just a figment of my imagination - never mind,..... doesn't matter!

[Pursang]

I believe that I have actually worked out a system on how that could possibly be done!
However, I am past the stage now really where I have the ability to carry out these experiments, so I have passed it on to someone else for evaluation - but no comment! ..... realistically, I assume and accept it's not a viable solution! - so it will no doubt remain just a figment of my imagination - never mind,..... doesn't matter!

Bill, if you really want Multiple evaluations by interested persons, and Plenty of comments, just post your ideas here!

cheers, Daryl.

[Flettner]

nothing can be ruled in or out until its tested. All ideas are valid until then.
OP uniflow is such an unknown, whats right, whats wrong?
Tumble flow may well have merrit.

[WilDun]

Bill, if you really want Multiple evaluations by interested persons, and Plenty of comments, just post your ideas here!

cheers, Daryl.

Yes, but I am such an introvert that I couldn't possibly do that! and what if some big foreign power got hold of it!! - where would it all end! - doesn't bear thinking about!

nothing can be ruled in or out until its tested. All ideas are valid until then.
OP uniflow is such an unknown, whats right, whats wrong?
Tumble flow may well have merrit.

That's fair comment -
I want to be realistic about my ideas (These thoughts are exactly that ! ie thoughts! - I do realize I could be entirely wrong) so I will not make all sorts of pre emptive claims ..... like someone else we all got to know on ESE a few years ago! and whose ideas possibly could have been enhanced by other peoples' input if only he had been prepared to listen, instead of arguing.
Things could have ended up with a much better outcome for his idea!

[Flettner]

No need to make claims, none of us know enough to do that, yet.
Thats the thing to think about, if you do review your idea here, its public from then on, like TPI for example.

[WilDun]

No need to make claims, none of us know enough to do that, yet.

For sure! but it's fun trying!

[lohring]

Thanks for your thoughts, everyone. I'm still thinking about some transfer options. The problem with belt drives is I want opposite rotating crankshafts. The gears are inexpensive, but hardened, RC car gears and should mostly be lightly loaded. I found a CFD study of scavenging with different crankshaft phase angles, but nothing about scavenging port angles. Trying to fit the long transfers around the exhaust along with cooling flow has been challenging, especially in Fusion 360. I'm learning more about lofts than I wanted to know. I think old time pattern making would be easier.

Lohring Miller

[Flettner]

I think old time pattern making would be easier.

Lohring Miller[/QUOTE]

YES.