Author Topic: V3 90 deg 'Jota' Engine big bore  (Read 665 times)

Offline AlexS

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V3 90 deg 'Jota' Engine big bore
« on: December 22, 2019, 09:32:14 PM »
Hello there,

What should you do, when you have ideas and make some sketches the last couple of months?
I will start on make a 3d model of a new engine. And later on build it.

A multi cylinder of higher rpm range. More kind of a 'sport' engine.

I do like three, six and even twelve cylinder engines of there sound an simplicity/engine balance. But something different.
But what about a V3 engine? I only know a couple two stroke bikes that use this engine geometry (Honda NS500).


I was thinking of the next thing.

- 3 cylinder 90 degree bank angle
- 180 degree crankshaft. Where cylinder 1 and 3 are on 180 degree, and cylinder 2 shares the crank journal with cylinder 1. (so it is more a mix of a 180 deg twin and 90 deg V twin engine)
- Big bore B/S ratio around 1.4-1.5
- 3 or 4 valve design per cylinder
- Overhead camshaft while cylinder 1 and 3 shares the intake and exhaust camshafts(cam rollers are shifted 180 degrees)
- Split connecting rods with one piece crankshaft, two smaller bearings on each side, a larger bearing in the middle
- Thinking of 2 split crankcase
- Addition, two primary balance shafts for compensate the piston motion of cylinder 2
- Water-cooled
- Larger cam durations than my one cylinder, higher static compression ratio to 1:8-9

Firing order 1-3-2
1 [180 °] 3 [270 °] 2 [270 °]


Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #1 on: December 23, 2019, 01:18:16 AM »

A rough principle of the bottom block of the V3 engine. Reused some parts and had to modded dimensions.

Offline Art K

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #2 on: December 23, 2019, 03:37:29 AM »
Alex,
That sounds complicated, I'm glad you are visualizing how to make this work & not me.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Admiral_dk

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #3 on: December 23, 2019, 11:49:24 AM »
Hi Alex

The Laverda Jota was a straight 3 cylinder Four Stroke 1000cc with a 180 degree crank for the first six years 1976-1982 and later with a 120 degree crank - is this the one the title refers to ?

Real V3 motorcycles where : 1955 DKW 350, 1968 Suzuki RP68, 1982-1984 Honda NS5000/NSR500, 1983-1984 Honda MVX250F and 1985-1987 Honda NS400R.

A related layout was the W3 engine, although this placed all three cylinders in the same plane, but none of them in the same bank. This was used for the 1905–1915 four-stroke Anzani engine, which was used in motorcycle and aircraft applications.

I have tried to construct something similar to your ideas in Alibre a few years ago, but was never satisfied with the result ....

Best wishes

Per
« Last Edit: December 23, 2019, 01:40:37 PM by Admiral_dk »

Online tghs

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #4 on: December 23, 2019, 12:35:09 PM »
having road a few bikes, laverda jotas were a bit on the thumpy side at lower rpms, but fast and powerful once up to speed, great open road bike.. when BMW K100's came out (4cylinder inline)fast, even power with a harmonic buzz at certain rpms, I thought the electronic gear indicator was one of those "why?" things.. a few years later when the K75 came out (3 cylinder with a counter rotating counter balanced shaft) it was needed as the motor was as smooth as an electric motor,, best triple ever made 
what the @#&% over

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #5 on: December 23, 2019, 01:44:00 PM »
Yes indeed Per, this engine is refers to the Laverda Jota straight 3 engine. But then a V3 Jota. Seen that Laverda is not doing business anymore, they could not blame me for use the same name  ;)
The Laverda is known to me. For example, my father rode a 3C Jota from the 80s to around the 00s. I myself can no longer remember that he was still driving it. But funny fact, our current dog and former cat was also called Jota.
But an old neighbour here drove the same bike weekly in the warmer days. And you could tell by the typical sound whether he started it or came back from driving it.

After some looking on Youtube I saw a late 3 radial and early W3 engine. Here the guys are not scared, some fresh burned fuel after breakfast is a good way to start the day.

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #6 on: December 23, 2019, 04:23:01 PM »
I was looking for a site that sells CI piston rings. I can remember that I have visited a site that was suggested on this forum before. But can't remember the name :-[
I could remember that they also had rings for a 45 mm bore. And they sold more ready-made attributes for model engine construction.
Thanks!

Offline Roger B

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #7 on: January 01, 2020, 08:31:36 AM »
That's an interesting design concept and another interesting balance calculation  :ThumbsUp:  :ThumbsUp:

At 45mm bore maybe a moped or garden tools supplier can help with piston rings.
Best regards

Roger

Offline AlexS

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Re: V3 90 deg 'Jota' Engine big bore
« Reply #8 on: January 01, 2020, 03:38:12 PM »
For crank design I was thinking of rotation balance in the mid section web between cylinder 1 and 3. Cylinder 1 and 2 shared the same crank journal and so the extra length and +- 1/2 part of the weight of the connecting rod of the cylinder 2 should be compensate in the mid section web of the crankshaft(like you balance an one cylinder engine). And would be great to add two primary balance shafts in line of cylinder 2, that rotate the speed of the crankshaft to compensate the 'missing' 4th cylinder. So basically it should vibrate like a four-in-line engine. Would be fun to design and build for sure!

Thanks Roger I would look around for a related piston size of used mopeds.