Author Topic: V3 90 deg 'Jota' Engine big bore  (Read 3361 times)

Offline Roger B

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #15 on: November 28, 2021, 05:13:18 PM »
Sleeve valves were (are?)used in aircraft engines.
Best regards

Roger

Offline Art K

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #16 on: November 29, 2021, 01:25:21 AM »
Alex,
Not to help you jump down the rabbit hole, but the sleeve valve engine is an interest of mine. There are two types of sleeve valve engines. The Knight uses a system with two cranks each operating sleeves they each have ports in them opening at intake and exhaust. Willy's in the US and Daimler in Britain are probably the most famous to use the system. The single sleeve Burt-McCollum design uses a crankshaft to drive the sleeve. This gives the sleeve an eliptical path opening the ports as it moves. It's best known for its use in Bristol Hercules and Centaurus aircraft engines. But It was also used in the Scottish auto Argyll and also Barr and Stroud motorcycle engines. I would suggest saving the sleeve valve for a different engine and do the V3 with conventional valves.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #17 on: November 29, 2021, 06:17:48 PM »
Thanks for the info guys.

It would be great for a test engine or single cylinder one. Would be nice experiment to build. But agree with you Art, it takes more challenge to fit in a V engine, and to get a good cylindricity of the sleeves (for my beginner skill and lathe).
But does someone here build a sleeve model before?
« Last Edit: November 29, 2021, 07:49:26 PM by AlexS »

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #18 on: November 29, 2021, 07:48:39 PM »
Tonight played with putting info in a simulator. Would like to run the simulations tomorrow and make some changes on geometry of valve/port and cam system.

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #19 on: November 30, 2021, 09:02:46 PM »
First digital testrun are done!  :atcomputer:

1st picture shows power curve of a 1 cylinder test engine. Changed some spec of the valves, cams and last manifold diameter of the intake. This should also be done for intake diameter before throttle valve (simulated for each cylinder) and for exhaust manifold and pipe (straight pipe for now).

2nd picture the power curve of the start model and latest changed model of the 3 cylinder (simulated as inline 3).
I am not really interested to get every hp out of it or in the horse numbers, but more that I am in the right direction to get a breathing and powerful high rpm engine ;)

For comparison, Dirtbike Honda CRF150R: 23,5 hp @12500 RPM 14.10 Nm @ 11000 RPM [66.0 mm bore x 43.7 mm stroke].
« Last Edit: November 30, 2021, 09:07:37 PM by AlexS »

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #20 on: December 01, 2021, 09:05:12 PM »
Today played around with EngMod4t and Solidworks model.

Simulation:

Intake/Exhaust valves 20mm both 6mm lift 250 deg duration with 40 deg overlap.
Intake and exhaust manifold and even for runner/pipe 20 mm diameter. Intake runner length 50+50 mm between valves-carb-atmosphere.


Added bigend split bearings for the split connecting rod. Changed some dimensions of the crank. Last thing added a idea of outside cylinder to liner.

Should be the "stickout"of the pistons to bad when the crank runs bdc swap? I could enlarger the liners, but the bottom side of the connecting rod hit the other liner in the V setup. More than the half of the piston skirt still hit the liner .

Offline Admiral_dk

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #21 on: December 01, 2021, 09:52:56 PM »
In my opinion you need to have the liners go a lot further down ....
Don't get me wrong - it will not prevent it from running as is, but it has a lot to do with wear and reliability ....

Also - the bigger the diameter to piston length ratio is - the higher demand on tight tolerances + full support on the total length of the travel. On the opposite end of that ratio, you can have the piston sticking far out without too many consequences ....

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #22 on: December 02, 2021, 10:03:24 AM »
Yes agree, playing around with dimensions of the connecting rod this is now 57.5 mm center-center big end to small end witch is now quit large for the stroke of 25! Or make the liners for Cyl 1 and 2 A-symmetrical.

Offline AVTUR

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #23 on: December 02, 2021, 11:18:15 AM »
Apologies for mentioning sleeve valves. The problem is that they don't scale. You are stuck with the same maximum engine speed whatever the engine size.

I will not metion the subject again on this thread.

I liked your valve calculations. I remember do them by hand at tech about 55 years ago.

AVTUR
There is no such thing as a stupid question.

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #24 on: December 03, 2021, 09:42:25 AM »
You don't have to apologies Avtur, I am always open for ideas. However, I am not really familiar with sleeve valves myself.

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #25 on: December 08, 2021, 07:43:03 PM »
For bottom part of the engine, changed connecting rod center-center dimension to 75 mm and lifted the cylinders a couple of mm.

Was thinking about making valve guides/cages out of grey cast iron. Valve seat, guide and sliding surface for cam followers in-one.

The surfaces of the valve guides and cam follower should be reamed H7. I am not sure if the material should fit to the job to get good sliding and surface finish.


Last picture a shoot of a very very raw design, things grew (+-14 kg).
« Last Edit: December 08, 2021, 08:00:16 PM by AlexS »

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #26 on: December 13, 2021, 07:55:33 PM »
A quick view of designing the Jota. Our dog is also called Jota even as a kitten years ago! Named of the motorcycle of my dad had years ago, Laverda.

So last weekend spend modelling of cylinder head parts. :) Local supplier sells cast iron for same price as bronze for valve guides. So think that fits job better also to have soft valve seats run in easier.

Dual overhead cam. Idea is to make it modular as possible. There should be a transmission axle and combined balance shaft between the cylinders to connect every cylinder head to crankshaft. 4 belts seems a lot, have to look how it would fit, but less issues with distancing of pulleys. There is enough space in above the V shape.
Exhaust and intake camshafts connected by a pair of spur wheels.

Shims under the cam followers to adjust valve clearance. I have thought about what is useful to fix the valve spring assembly. Valve stem is now 5mm and what about give it a little bit of M5 thread, making or weld a nut so you can fix it. Valve spring (15mm 2.5 thread) stiffness 37 N/mm to match oscillating mass of around 50 gram each valve assembly.

Needle bearings for camshaft and even for big end connecting rods (could run 12k rpm for big end). Camshaft axial fixated with shaft collar and spur wheels.

Offline Roger B

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #27 on: December 13, 2021, 08:41:34 PM »
The valve gear seems rather tall, the max. valve lift only needs to be 1/4 of the valve diameter.

Valve cages can give sealing problems, especially with different thermal expansion. unless you are looking at serious use seats directly in the head will work.

Certainly an interesting design  :)  :ThumbsUp: Have you looked at ports and manifolds yet?
Best regards

Roger

Offline Art K

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #28 on: December 14, 2021, 02:59:32 AM »
Alex,
Just out of curiosity what is the angle between firing. The twin part of your engine would fire 180 degrees apart. Like an old John Deere B is a parallel twin fires 180 apart then 540 degrees before firing again. Is the 3rd cylinder such that it offsets that 540 deg. of no power stroke?
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #29 on: December 14, 2021, 07:08:57 PM »
Roger,

Yes the cams are quit large, 6mm lift while the valves are 20mm 5mm can also  :thinking:
I was thinking of press the two aluminium head part together, bore it to 19.5 mm and the ream it to 20H7 +21/0. Then turn valve cages with press fit p6 +48/+35 tolerance. Not sure if it seals good enough, maybe you have a idea?

Valve cages can give sealing problems, especially with different thermal expansion. unless you are looking at serious use seats directly in the head will work.

What do you mean by this sentence?


So far thinking of ports and manifold: Option A, to bore for intake 18mm or 16mm for each intake valve. Boring at an angle of 45 deg (viewing from horizontal orientation). And then mill both holes to a straight slot to meet the manifold or mill a v-shape hole in the manifold to combine both runners. I realise now that when you do this, you go straight trough the mounting holes cylinder studs.

Another option B is to mill both intake runners at right angles to the valve cages. But bore it with some angle so the centre of the runners meet each other in the head as one hole (Viewing from vertical orientation, face where manifold would be mounted). Doing both in angle directions would be difficult. Maybe with some angle fixture to mount the head on (mill can only twist the Z-axis).


Art,

Yes! The angle between firing between the twin part (cylinder 1 and 3) firing 180 degrees apart. 180-270-270 So first you have cylinder 1 bang, after 180 degree cylinder 3 bang, then after 270 degree cylinder 2 bang, 270 degree further cylinder 1 bang and then everything repeat. V-twin and inline twin combined.
I think this should give a nice sound. Other option is (cyl.1)90(cyl.2)-90(cyl.3)540 and so on. Or (cyl.1)90(cyl.2)-450(cyl.3)180. Or (cyl.1)450(cyl.2)-90(cyl.3)180.